Martyn Poliakoff

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Name: Albertina Cabañas

Organization: School of Chemistry University of Nottingham Nottingham , England

Department: School of Chemistry University of Nottingham Nottingham

Title: (PhD)

TOPICS

Organic Chemistry

Asymmetric Synthesis Hydrogenation

Inorganic Chemistry

Metal Organic Frameworks

Chemicals
References

Continuous niobium phosphate catalysed Skraup reaction for quinoline synthesis from solketal

Co-reporter:Jing Jin;Sandro Guidi;Zahra Abada;Zacharias Amara;Maurizio Selva;Michael W. George

Green Chemistry (1999-Present) 2017 vol. 19(Issue 10) pp:2439-2447

Publication Date(Web):2017/05/22

DOI:10.1039/C6GC03140D

Solketal is derived from the reaction of acetone with glycerol, a by-product of the biodiesel industry. We report here the continuous reaction of solketal with anilines over a solid acid niobium phosphate (NbP), for the continuous generation of quinolines in the well-established Skraup reaction. This study shows that NbP can catalyse all the stages of this multistep reaction at 250 °C and 10 MPa pressure, with a selectivity for quinoline of up to 60%. We found that the catalyst eventually deactivates, most probably via a combination of coking and reduction processes but nevertheless we show the promise of this approach. We demonstrate here the application of our approach to synthesize both mono- and bis-quinolines from the commodity chemical, 4,4′-methylenedianiline.

A laboratory-scale annular continuous flow reactor for UV photochemistry using excimer lamps for discrete wavelength excitation and its use in a wavelength study of a photodecarboxlyative cyclisation

Co-reporter:Erica N. DeLaney;Darren S. Lee;Luke D. Elliott;Jing Jin;Kevin I. Booker-Milburn;Michael W. George

Green Chemistry (1999-Present) 2017 vol. 19(Issue 6) pp:1431-1438

Publication Date(Web):2017/03/20

DOI:10.1039/C6GC02888H

This paper describes a new annular reactor for continuous UV photochemistry, which uses easily interchangeable excimer lamps of different wavelengths. The reactor has narrow clearance to form thin films of material for efficient irradiation of molecules. Its use is demonstrated by investigating the effect of discrete wavelength lamps (222, 282 and 308 nm) on the reaction of potassium N-phthalimidobutanoate 1. The ability of the reactor to be integrated into multistep processes is illustrated by combining it with an Amberlyst scavenger and a solid acid catalyst, NbOPO4, to access a second product 3 that is obtained in a single telescoped process. The tricyclic scaffold in 3 is a motif found in several biologically active compounds and has possibilities as a synthon for new pharmaceutical products.

Yuri and high temperature water

Co-reporter:Martyn Poliakoff

Journal of Molecular Liquids 2017 Volume 239(Volume 239) pp:

Publication Date(Web):1 August 2017

DOI:10.1016/j.molliq.2017.05.072

A Simple and Versatile Reactor for Photochemistry

Co-reporter:Charlotte A. Clark, Darren S. Lee, Stephen J. Pickering, Martyn Poliakoff, and Michael W. George

Organic Process Research & Development 2016 Volume 20(Issue 10) pp:1792-1798

Publication Date(Web):September 21, 2016

DOI:10.1021/acs.oprd.6b00257

A photoreactor that generates a thin film upon rotation for efficient irradiation of solutions is described. The reactor is based around a standard piece of equipment found in most synthetic laboratories, namely, a rotary evaporator. Three different photo-oxidation reactions have been used to examine the effects of several parameters such as irradiated volume, flask size, rotation speed, and light intensity. The reactor can be operated in a semicontinuous manner, and two possible configurations are described. The thickness of the generated film and the rate of mixing under different conditions have been examined using in situ electronic absorption spectroscopy.

Enabling the Scale-Up of a Key Asymmetric Hydrogenation Step in the Synthesis of an API Using Continuous Flow Solid-Supported Catalysis

Co-reporter:Zacharias Amara, Martyn Poliakoff, Rubén Duque, Daniel Geier, Giancarlo Franciò, Charles M. Gordon, Rebecca E. Meadows, Robert Woodward, and Walter Leitner

Organic Process Research & Development 2016 Volume 20(Issue 7) pp:1321-1327

Publication Date(Web):June 10, 2016

DOI:10.1021/acs.oprd.6b00143

The development of a continuous flow process for asymmetric hydrogenation with a heterogenized molecular catalyst in a real industrial context is reported. The key asymmetric step in the synthesis of an API (active pharmaceutical ingredient) has been developed on a kilogram scale with constant high single-pass conversion (>95.0%) and enantioselectivity (>98.6% ee) through the asymmetric hydrogenation of the corresponding enamide. This performance was achieved using a commercially available chiral catalyst (Rh/(S,S)-EthylDuphos) immobilized on a solid support via strong interaction resulting from the requirement of electroneutrality. The factors affecting the long-term catalyst stability and enantioselectivity were identified using small-scale continuous flow setups. A dedicated automated software-controlled high-pressure pilot system with a small footprint was then built and the asymmetric hydrogenation on kilogram-scale was realized with a space time yield (STY) of up to 400 g L–1 h–1 at predefined conversion and enantiopurity levels. No catalyst leaching was detected in the virtually metal-free product stream, thereby eliminating costly and time-consuming downstream purification procedures. This straightforward approach permitted an easy and robust scale-up from gram to kilogram scale fully matching the pharmaceutical quality criteria for enantiopurity and low metal content, thus demonstrating the high versatility of fully integrated continuous flow molecular catalysis.

Selective aerobic oxidation of para-xylene in sub- and supercritical water. Part 3: effects of geometry and mixing in laboratory scale continuous reactors

Co-reporter:Eduardo Pérez, Morgan L. Thomas, Duncan Housley, Paul A. Hamley, Joan Fraga-Dubreuil, Jun Li, Edward Lester and Martyn Poliakoff

RSC Advances 2016 vol. 6(Issue 14) pp:11289-11294

Publication Date(Web):27 Jan 2016

DOI:10.1039/C5RA26964D

In this paper we report a strong dependence of the observed performance of the catalyst on the geometry and the configuration of laboratory scale reactors in the continuous aerobic oxidation of p-xylene in supercritical water. Small differences, such as the length of the feed pipes protruding into the reactor, have a very large effect on the observed yields and selectivities as well as on the reproducibility of the results. Different reactor designs also exert an influence on the perceived catalyst performance. We demonstrate that these effects are consistent with the relative efficiency of mixing of the reactant streams in the different reactors. The overall conclusion is that caution is required when comparing sets of data derived from studying such reactions even in apparently similar experimental arrangements.

A synthetic-dynamic method for water solubility measurements in high pressure CO2 using ATR–FTIR spectroscopy

Co-reporter:Gurbuz Comak, Stéphanie Foltran, Jie Ke, Eduardo Pérez, Yolanda Sánchez-Vicente, Michael W. George, Martyn Poliakoff

The Journal of Chemical Thermodynamics 2016 Volume 93() pp:386-391

Publication Date(Web):February 2016

DOI:10.1016/j.jct.2015.09.024

•A synthetic method using ATR–FTIR spectroscopy has been developed to measure the solubility of water in CO2.•New data have been obtained for the dew point of the water at 4.05 MPa, 5.05 MPa and 6.03 MPa.•These data fill a gap in the literature and could be of significance for CO2 transport in pipelines for CCS technology.A new synthetic method for studying phase behaviour is described using Attenuated Total Reflection (ATR) spectroscopy. The method has been developed to provide relevant information on the solubility of water in CO2. The dew point of water has been determined at three different pressures, viz. (4.05, 5.05 and 6.03) MPa with mole fractions of water between 0.01 and 0.04. The data obtained fill the gap in the literature in these regions of pressures and temperatures and could be of high importance in the context of Carbon Capture and Storage (CCS) technology. Indeed, the presence of water in the captured CO2 could damage the pipeline used for CO2 transport. Hence, it is very important to have a fully understanding of the behaviour of the (CO2 + H2O) mixtures in wide range of temperature relevant for CCS.

Continuous catalytic upgrading of ethanol to n-butanol and C4 products over Cu/CeO2 catalysts in supercritical CO2

Co-reporter:James H. Earley, Richard A. Bourne, Michael J. Watson and Martyn Poliakoff

Green Chemistry 2015 vol. 17(Issue 5) pp:3018-3025

Publication Date(Web):09 Mar 2015

DOI:10.1039/C4GC00219A

n-Butanol (BuOH) often has superior properties as a bio-fuel compared to ethanol (EtOH). However finding sustainable sources of BuOH is proving difficult. In this paper, direct production of BuOH from EtOH is compared over custom-synthesized six Cu catalysts, supported on different solid acids. These catalysts were tested in a continuous flow supercritical CO2 (scCO2) reactor, and were found to catalyse the dehydrogenation, aldol condensation and hydrogenation steps of the so-called Guerbet reaction converting EtOH to BuOH. BuOH yields and selectivities were significantly different over the four catalysts. Cu on high surface area CeO2 showed the best activity for BuOH formation, with yields above 30% achieved with good selectivity. In addition high pressure CO2 is shown to have a positive effect on the reaction, possibly due to the redox cycle of Ce2O3 and CeO2.

Photocatalytic hydroxylation of arylboronic acids using continuous flow reactors

Co-reporter:Inès G. T. M. Penders, Zacharias Amara, Raphael Horvath, Kai Rossen, Martyn Poliakoff and Michael W. George

RSC Advances 2015 vol. 5(Issue 9) pp:6501-6504

Publication Date(Web):17 Dec 2014

DOI:10.1039/C4RA15588B

The photocatalytic oxidation of mono- and di-substituted arylboronic acids to phenols has been investigated using a continuous flow photoreactor fitted with white LEDs. An EtOH–H2O solvent system accelerated conversion at 2 MPa; whereas reactions at atmospheric pressure allowed for moderately efficient desymmetrisation.

Synthesis of metal–organic frameworks by continuous flow

Co-reporter:Peter A. Bayliss, Ilich A. Ibarra, Eduardo Pérez, Sihai Yang, Chiu C. Tang, Martyn Poliakoff and Martin Schröder

Green Chemistry 2014 vol. 16(Issue 8) pp:3796-3802

Publication Date(Web):06 Jun 2014

DOI:10.1039/C4GC00313F

A continuous flow process for the synthesis of a metal–organic framework using only water as the reaction medium and requiring only short residence times is described. This affords a new route to scale-up of materials incorporating many of the principles of Green Chemistry. The process is demonstrated by the synthesis MIL-53(Al) via continuous flow reaction requiring only 5–6 minutes with a space time yield of 1300 kg m−3 d−1. We have demonstrated the synthesis of 500 g of MIL-53(Al) using this process, which can be scaled-up further by simply feeding further solutions of metal salt and ligand through the reactor. The product has a higher surface area and a better colour than a commercially produced sample of this MOF. In addition, a new and effective method for the extraction of terephthalic acid from within the pores of MIL-53(Al) using supercritical ethanol has been developed, representing a new methodology for activation and removal of substrates from porous hosts.

Synthesis of antimalarial trioxanes via continuous photo-oxidation with 1O2 in supercritical CO2

Co-reporter:Jessica F. B. Hall, Richard A. Bourne, Xue Han, James H. Earley, Martyn Poliakoff and Michael W. George

Green Chemistry 2013 vol. 15(Issue 1) pp:177-180

Publication Date(Web):15 Nov 2012

DOI:10.1039/C2GC36711D

The oxidation of an allylic alcohol to its hydroperoxides represents a key step in the synthesis of a series of spirobicyclic, antimalarial trioxanes. Herein, we investigate the continuous photo-oxidation of an allylic alcohol with 1O2 in scCO2, as a ‘green’ alternative to conventional methods, and examine the remaining two steps in the synthesis of antimalarial trioxanes from readily available starting materials.

Editorial: Conveying the Excitement of Chemistry on YouTube

Co-reporter:Brady Haran ; Martyn Poliakoff

Angewandte Chemie International Edition 2013 Volume 52( Issue 34) pp:8758-8759

Publication Date(Web):

DOI:10.1002/anie.201304861

No abstract is available for this article.

Editorial: Auf YouTube fr Chemie begeistern

Co-reporter:Brady Haran ; Martyn Poliakoff

Angewandte Chemie 2013 Volume 125( Issue 34) pp:8920-8921

Publication Date(Web):

DOI:10.1002/ange.201304861

No abstract is available for this article.

Near-critical water, a cleaner solvent for the synthesis of a metal–organic framework

Co-reporter:Ilich A. Ibarra, Peter A. Bayliss, Eduardo Pérez, Sihai Yang, Alexander J. Blake, Harriott Nowell, David R. Allan, Martyn Poliakoff and Martin Schröder

Green Chemistry 2012 vol. 14(Issue 1) pp:117-122

Publication Date(Web):14 Nov 2011

DOI:10.1039/C1GC15726D

The microporous metal–organic framework {[Zn2(L)]·(H2O)3}∞ (H4L = 1,2,4,5-tetrakis(4-carboxyphenyl)benzene) has been synthesised using near-critical water (300 °C) as a cleaner alternative to toxic organic solvents. A single crystal X-ray structure determination confirms that the complex incorporates tetrahedral Zn(II) centres bridged through the carboxylate anions to form a binuclear building block, which extends into a one dimensional chain along the c axis. Four L4− ligands bind to each Zn(II) centre and cross-link the one dimensional chains along both a and b axes to afford a three dimensional network structure incorporating pores of ca. 4.3 Å in diameter. The complex shows high thermal stability up to 425 °C by gravimetric thermal analysis, and on desolvation, displays a high adsorption enthalpy of 11.0 kJ mol−1 for H2 uptake at zero coverage, consistent with the narrow pore diameter for the framework.

Immobilised photosensitisers for continuous flow reactions of singlet oxygen in supercritical carbon dioxide

Co-reporter:Xue Han, Richard A. Bourne, Martyn Poliakoff and Michael W. George

Chemical Science 2011 vol. 2(Issue 6) pp:1059-1067

Publication Date(Web):11 Mar 2011

DOI:10.1039/C0SC00641F

Photosensitisers have been incorporated into both polymer and aerogel supports for the photochemical generation of singlet oxygen, 1O2, in supercritical carbon dioxide, scCO2. These systems showed high activity and an acceptable lifetime for the photo-oxidation of α-terpinene and of citronellol in continuous reactors over a period of at least 5 h. The most effective photosensitiser was a covalently coupled analogue of tetradi(2,6)chloro-phenylporphyrin (TDCPP) on polyvinyl chloride (PVC). This immobilisation removes the need to separate the photosensitiser from the downstream solution.

Could the energy cost of using supercritical fluids be mitigated by using CO2 from carbon capture and storage (CCS)?

Co-reporter:James G. Stevens, Pilar Gómez, Richard A. Bourne, Trevor C. Drage, Michael W. George and Martyn Poliakoff

Green Chemistry 2011 vol. 13(Issue 10) pp:2727-2733

Publication Date(Web):01 Sep 2011

DOI:10.1039/C1GC15503B

This article explores the possibility of utilising supercritical CO2 obtained from carbon capture and storage (CCS) as a solvent and examines the hydrogenation of isophorone to 3,3,5-trimethylcyclohexanone using supercritical CO2 with added N2, CO or H2O to emulate the contaminants expected in CO2 from CCS. None of the impurities appear to cause insuperable problems in the hydrogenation of isophorone when present at concentrations likely to be found in CO2 from CCS. N2 introduces modest changes in phase behaviour at some pressures, while CO and H2O reduce the activity of the catalyst. However, the activity can be largely regained by increasing the reaction temperature.

Selective aerobic oxidation of para-xylene in sub- and supercritical water. Part 2. The discovery of better catalysts

Co-reporter:Eduardo Pérez, Joan Fraga-Dubreuil, Eduardo García-Verdugo, Paul A. Hamley, Morgan L. Thomas, Chong Yan, W. Barry Thomas, Duncan Housley, Walt Partenheimer and Martyn Poliakoff

Green Chemistry 2011 vol. 13(Issue 9) pp:2397-2407

Publication Date(Web):21 Jul 2011

DOI:10.1039/C1GC15138J

An extensive and systematic study has been carried out on the catalytic effect of more than 20 elements on the aerobic oxidation of p-xylene to terephthalic acid in super- and subcritical water. Reactions have been performed in a continuous reactor under catalyst unsaturated conditions. Reaction product, by-products and intermediates have been quantified as well as the burn (the amount of CO2 originating from total oxidation of p-xylene). CuBr2 has been found to be a superior catalyst to MnBr2, which has been widely used in the literature for this reaction in water at high temperatures. At catalyst unsaturated conditions (i.e. with low concentrations of catalyst), MnBr2 gives a terephthalic acid yield of 36.1% whereas CuBr2 enhances this value to 55.6%. A strong synergistic effect has been found between CuBr2 and other metals and sources of bromide. Indeed, we show that Cu/Co/Br, Cu/Co/NH4/Br and other mixtures give better results than CuBr2 reaching a terephthalic acid yield of 70.5% for the four component catalyst. The compositions of the catalyst as well as the reactor temperature have been optimized and their effects on the analyzed compounds are discussed. A substantial amount of additional data is included in the electronic supplementary information.

Selective aerobic oxidation of para-xylene in sub- and supercritical water. Part 1. Comparison with ortho-xylene and the role of the catalyst

Co-reporter:Eduardo Pérez, Joan Fraga-Dubreuil, Eduardo García-Verdugo, Paul A. Hamley, W. Barry Thomas, Duncan Housley, Walt Partenheimer and Martyn Poliakoff

Green Chemistry 2011 vol. 13(Issue 9) pp:2389-2396

Publication Date(Web):26 Jul 2011

DOI:10.1039/C1GC15137A

The selective, continuous, aerobic oxidations of para-xylene (pX) and ortho-xylene (oX) were performed in an identical fashion in supercritical water. The xylenes were oxidized without a catalyst and with hydrobromic acid, cobalt(II) and manganese(II) bromide catalysts. The conversions and yields to phthalic acid (OA) from oX were always significantly higher than those for terephthalic acid (TA) from pX. The formation of CO2 was significantly higher for pX than oX despite the higher conversions to oX. These results are unexpected because the literature teaches that thermal and catalytic decarboxylation is much higher for OA than TA. The superior yields from oX are consistent with a lower steady-state concentration of hydroxyl radicals, OH˙ due to the internal, concerted attack of the peroxides with the oX methyl group. This mechanism forms the phthalide directly from o-tolualdehyde (oTOL) which is consistent with the observation that ortho-toluic acid (OTA) is much lower in oX than para-toluic acid, PTA, in pX oxidation. This mechanism also lowers the steady-state concentration of aromatic acids consistent with the observed lower benzoic acid and CO2 yields. Overall, the results suggest that the metal catalysts can play more than one role, thereby opening up the opportunity for discovering new catalytic synergies which are explored in our next paper, Part 2 of this series.

The 13 Principles of Green Chemistry and Engineering for a Greener Africa

Co-reporter:Nigist Asfaw, Yonas Chebude, Andinet Ejigu, Bitu B. Hurisso, Peter Licence, Richard L. Smith, Samantha L. Y. Tang and Martyn Poliakoff

Green Chemistry 2011 vol. 13(Issue 5) pp:1059-1060

Publication Date(Web):18 Apr 2011

DOI:10.1039/C0GC00936A

A graphical abstract is available for this content

Adaptive Process Optimization for Continuous Methylation of Alcohols in Supercritical Carbon Dioxide

Co-reporter:Richard A. Bourne, Ryan A. Skilton, Andrew J. Parrott, Derek J. Irvine, and Martyn Poliakoff

Organic Process Research & Development 2011 Volume 15(Issue 4) pp:932-938

Publication Date(Web):May 12, 2011

DOI:10.1021/op200109t

A self-optimizing continuous flow reactor has been developed using the Super-Modified Simplex algorithm. This system, coupled with online gas chromatographic analysis enables automated optimization via a feedback control loop without user intervention. This has been applied to the methylation of 1-pentanol in supercritical carbon dioxide using dimethyl carbonate and methanol with γ-alumina catalyst to give 98% and ∼68% yield of pentyl methyl ether respectively. This was accomplished by variation of four reaction parameters; Temperature, Pressure, CO2 Flow rate, and the Ratio of methylating agent.

Applying a Fiber Optic Reflectometer to Phase Measurements in Subcritical and Supercritical Water Mixtures†

Co-reporter:Alexander A. Novitskiy ; Jie Ke ; Victor N. Bagratashvili

The Journal of Physical Chemistry C 2011 Volume 115(Issue 4) pp:1143-1149

Publication Date(Web):September 29, 2010

DOI:10.1021/jp106438d

A corrosion study of optic fibers in sub- and supercritical water has been carried out to find a suitable fiber for performing phase behavior studies with a fiber optic reflectometer on mixtures containing water at high pressures and temperatures. Corrosion was compared for a range of different fibers at 400 °C and 24 MPa. The lowest corrosion was observed with a fluorine-doped fiber. To validate the high resistance of the chosen fiber, the phase behavior of the binary system (water + ethanol) was studied at 250 °C, which gave results in good agreement with literature data. The fiber still gave acceptable signals after 40 experiments. The fiber was then used to measure, for the first time, the phase behavior of the reactive system of acetonitrile + water up to 300 °C.

Self-Optimizing Continuous Reactions in Supercritical Carbon Dioxide

Co-reporter:Andrew J. Parrott;Dr. Richard A. Bourne;Dr. Geoffrey R. Akien;Dr. Derek J. Irvine; Martyn Poliakoff

Angewandte Chemie International Edition 2011 Volume 50( Issue 16) pp:3788-3792

Publication Date(Web):

DOI:10.1002/anie.201100412

The Periodic Table of Videos

Co-reporter:Brady Haran

Science 2011 Volume 332(Issue 6033) pp:1046-1047

Publication Date(Web):27 May 2011

DOI:10.1126/science.1196980

A YouTube project, started on impulse, has become a chemistry resource in daily use in classrooms and homes worldwide.

Continuous heterogeneous catalytic oxidation of primary and secondary alcohols in scCO2

Co-reporter:Adrian O. Chapman, Geoffrey R. Akien, Nicholas J. Arrowsmith, Peter Licence and Martyn Poliakoff

Green Chemistry 2010 vol. 12(Issue 2) pp:310-315

Publication Date(Web):07 Jan 2010

DOI:10.1039/B913434D

A miniature catalytic reactor has been developed for the oxidation of alcohols with O2 in supercritical CO2. Particular attention has been given to ensuring good mixing of O2 and CO2 prior to contact with the substrate. The reactor was optimised using the oxidation of 2-octanol over 5% Pt + 1% Bi on Al2O3 and the mass balance was measured. The reactor was then evaluated for the oxidation of a series of secondary alcohols, and also the primary alcohol, 1-octanol.

Continuous Acid-Catalyzed Methylations in Supercritical Carbon Dioxide: Comparison of Methanol, Dimethyl Ether and Dimethyl Carbonate as Methylating Agents

Co-reporter:Peter N. Gooden, Richard A. Bourne, Andrew J. Parrott, Han S. Bevinakatti, Derek J. Irvine and Martyn Poliakoff

Organic Process Research & Development 2010 Volume 14(Issue 2) pp:411-416

Publication Date(Web):January 29, 2010

DOI:10.1021/op900307w

The development of high-yielding, “greener” chemistry-based routes for the continuous synthesis of methyl ethers are reported in this study. Ethers have been efficiently produced using a methodology which eliminates the use of toxic alkylating agents and reduces the waste generation that is characteristic of traditional etherification processes. For the first time it is shown that the use of acidic heterogeneous catalysts can successfully achieve etherification when using scCO2 as a reaction medium. Furthermore, the relative efficiencies of three alternative methylating agents, dimethyl carbonate, dimethyl ether and MeOH, have been compared and contrasted for the methylation of 1-octanol. Dimethyl carbonate has proven to be the superior methylating agent, demonstrating higher conversion and selectivity. Successful methylation of secondary alcohols, diols, carboxylic acids and amines using dimethyl carbonate in supercritical carbon dioxide has also been shown. Substrate structure was found to influence the temperature required to maximize the yield of the desired product, substrates with multiple hydroxyl groups requiring the highest temperatures.

The Continuous Catalytic Debenzylation of 1,4-Dibenzyloxybenzene with H2 in THF Expanded with High Pressure CO2

Co-reporter:Geoffrey R. Akien, Jean-Christophe Legeay, Andrew Wells, and Martyn Poliakoff

Organic Process Research & Development 2010 Volume 14(Issue 5) pp:1202-1208

Publication Date(Web):July 19, 2010

DOI:10.1021/op100136g

The continuous debenzylation of 1,4-dibenzyloxybenzene (1a) with H2 and supported Pd catalysts has been studied in high-pressure CO2 + tetrahydrofuran. A range of parameters and catalysts have been tested, with one of the most successful results giving 86% conversion and 86% selectivity to the monodebenzylated product, 1,4-(benzyloxy)phenol (2a). In the absence of CO2, the reaction was unselective with no formation of 2a. When complete debenzylation was required, the best catalyst was 5% Pd supported on Deloxan APII, giving quantitative yields of hydroquinone (3), the completely debenzylated product, at temperatures as low as 50 °C. This Deloxan-supported catalyst was also substantially active at only 30 °C.

The Continuous Acid-Catalysed Etherification of Aliphatic Alcohols Using Stoichiometric Quantities of Dialkyl Carbonates

Co-reporter:Andrew J. Parrott, Richard A. Bourne, Peter N. Gooden, Han. S. Bevinakatti, Martyn Poliakoff, and Derek J. Irvine

Organic Process Research & Development 2010 Volume 14(Issue 6) pp:1420-1426

Publication Date(Web):October 27, 2010

DOI:10.1021/op1002243

A range of methyl and ethyl ethers of aliphatic alcohols have been synthesized cleanly in high yield by reacting the corresponding alcohol with dimethyl carbonate or diethyl carbonate over the solid acid catalyst, γ-alumina. The reaction could be conducted at ambient pressure without the need for the large excess of dialkyl carbonate as previously reported in the literature. If the reaction was conducted at high pressure, the conversion of the starting alcohol was greatly reduced. However, high pressure CO2 can be used as the solvent without significant reduction in yield. This has implications for tandem reactions.

Pressure Drop as a Simple Method for Locating Phase Transitions in Continuous Flow High Pressure Reactors

Co-reporter:Geoffrey R. Akien, Ryan A. Skilton and Martyn Poliakoff

Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 10) pp:4974

Publication Date(Web):April 27, 2010

DOI:10.1021/ie902017b

This paper describes the use of the pressure drop across a packed column to locate phase transitions in high-pressure fluids in continuous flow. The pressure drop method yields data that can be used to locate phase transitions objectively, and an example of an automated searching algorithm is demonstrated as a proof of concept. Finally, we demonstrate the ability of the pressure drop method to be applied in operando to a hydrogenation reaction.

Real-Time Product Switching Using a Twin Catalyst System for the Hydrogenation of Furfural in Supercritical CO2

Co-reporter:James G. Stevens;Dr. Richard A. Bourne;Dr. Martyn V. Twigg; Martyn Poliakoff

Angewandte Chemie International Edition 2010 Volume 49( Issue 47) pp:8856-8859

Publication Date(Web):

DOI:10.1002/anie.201005092

The continuous self aldol condensation of propionaldehyde in supercritical carbon dioxide: a highly selective catalytic route to 2-methylpentenal

Co-reporter:James G. Stevens, Richard A. Bourne and Martyn Poliakoff

Green Chemistry 2009 vol. 11(Issue 3) pp:409-416

Publication Date(Web):23 Jan 2009

DOI:10.1039/B819687G

The aldol reactions of propionaldehyde and butyraldehyde have been explored in supercritical CO2, scCO2, using an automated continuous flow reactor. The reaction was found to proceed over a variety of heterogeneous acidic and basic catalysts and with increased selectivity compared to using neat reactants.

A critical look at reactions in class I and II gas-expanded liquids using CO2 and other gases

Co-reporter:Geoffrey R. Akien and Martyn Poliakoff

Green Chemistry 2009 vol. 11(Issue 8) pp:1083-1100

Publication Date(Web):02 Jun 2009

DOI:10.1039/B904097H

This short review aims to give a summary of the publications on reactions in class I and II gas-expanded liquids (GXLs) (those with organic or aqueous liquid components), and to draw conclusions from the trends in the current literature.

Strategies for cleaner oxidations using photochemically generated singlet oxygen in supercritical carbon dioxide

Co-reporter:Xue Han, Richard A. Bourne, Martyn Poliakoff and Michael W. George

Green Chemistry 2009 vol. 11(Issue 11) pp:1787-1792

Publication Date(Web):07 Sep 2009

DOI:10.1039/B914074C

Photochemically generated singlet oxygen, 1O2, has been reacted with four different substrates in supercritical carbon dioxide. By using fluorous surfactants and a co-solvent to solubilise more polar photosensitisers and reactants respectively, the applicability of the system is greatly enhanced.

Cleaner Continuous Photo-Oxidation Using Singlet Oxygen in Supercritical Carbon Dioxide

Co-reporter:RichardA. Bourne Dr.;Xue Han, ;MichaelW. George

Angewandte Chemie 2009 Volume 121( Issue 29) pp:5426-5429

Publication Date(Web):

DOI:10.1002/ange.200901731

Cleaner Continuous Photo-Oxidation Using Singlet Oxygen in Supercritical Carbon Dioxide

Co-reporter:RichardA. Bourne Dr.;Xue Han, ;MichaelW. George

Angewandte Chemie International Edition 2009 Volume 48( Issue 29) pp:5322-5325

Publication Date(Web):

DOI:10.1002/anie.200901731

Phase Behavior, Densities, and Isothermal Compressibility of CO2 + γ-Valerolactone Systems in Various Phase Regions

Co-reporter:Yucui Hou, Weize Wu and Martyn Poliakoff

Journal of Chemical & Engineering Data 2009 Volume 54(Issue 1) pp:118-126

Publication Date(Web):December 12, 2008

DOI:10.1021/je8007759

The phase behavior of CO2 and γ-valerolactone (GVL) has been measured using a high-pressure variable-volume view cell and a fiber optic reflectometer. The density of the binary mixture has also been measured, and the isothermal compressibility (KT) of the binary mixture was calculated from the density of the binary mixture. The phase transition points, bubble point, dew point, and critical point, have been measured on the range of GVL mole fraction from 0.01 to 0.15 and temperatures from (308.2 to 550.2) K. The density of the mixture is sensitive to the pressure near the critical point of the mixtures, and KT is also sensitive to the pressure when the pressure is close to the phase transition point, especially close to the critical point. When the pressure is much higher than the phase separation pressure or the composition is far from the critical composition, KT is very small and the effect of pressure on KT is very limited. The phase boundary data of the binary mixture can be correlated well by the Peng−Robinson equation of state (PR EOS) with two interaction parameters.

A New Continuous Method for Performing Rapid Phase Equilibrium Measurements on Binary Mixtures Containing CO2 or H2O at High Pressures and Temperatures

Co-reporter:Alexander A. Novitskiy, Eduardo Pérez, Weize Wu, Jie Ke and Martyn Poliakoff

Journal of Chemical & Engineering Data 2009 Volume 54(Issue 5) pp:1580-1584

Publication Date(Web):February 20, 2009

DOI:10.1021/je800923q

Apart from paying a deserved tribute to Professor Schneider, a new synthetic dynamic method for rapid determination of phase boundaries at high pressures and temperatures is presented. This device is based on the change in the Flame Ionization Detector signal given by a small amount of sample taken by a capillary fiber from an equilibrium cell through which a mixture of known composition is continuously flowing. To validate the method, the phase boundaries for the system acetone + CO2 are measured at (0.2 and 0.7) acetone mole fraction and at (350 to 380) K. We also measured the phase boundaries for the system ethanol + H2O at compositions ranging from (0.05 to 0.4) ethanol mole fraction and temperatures up to 600 K. The results agree well with literature data, showing the feasibility of this method to measure the phase behavior of binary mixtures containing CO2 and H2O at extreme conditions.

A dramatic switch in selectivity in the catalytic dehydrogenation of 4-vinylcyclohexene in high pressure steam; a cautionary lesson for continuous flow reactions

Co-reporter:Morgan L. Thomas, Joan Fraga-Dubreuil, A. Stuart Coote and Martyn Poliakoff

Green Chemistry 2008 vol. 10(Issue 2) pp:197-201

Publication Date(Web):21 Nov 2007

DOI:10.1039/B706711A

We report an investigation of the continuous oxidative dehydrogenation of 4-vinylcyclohexene (VCH) in high pressure steam. Oxidative dehydrogenation reactions such as this are often limited by unselective or total oxidation. We find that these side-reactions not only occur in this case, but can also have a major influence on the selectivity; a small increase in flow rate results in a complete switch in selectivity of the reaction. Our results suggest that styrene (ST) is formed as the initial product but that unless the H2 is sequestered, ST may then be hydrogenated to yield ethylbenzene (EB). The observation of periodic temperature spikes near the surface of the catalyst bed indicate cycles of propagating flames occur in a relatively small volume of the reactor, leading to total oxidation of some VCH and removal of O2, which would otherwise sequester the H2. These flames give rise to the large variations in the observed product selectivity. We suggest that these observations may not be restricted to this reaction system and reactor configuration, and may occur in other situations where small-scale continuous flow oxidation reactors are used.

The continuous synthesis of ε-caprolactam from 6-aminocapronitrile in high-temperature water

Co-reporter:Chong Yan, Joan Fraga-Dubreuil, Eduardo Garcia-Verdugo, Paul A. Hamley, Martyn Poliakoff, Ian Pearson and A. Stuart Coote

Green Chemistry 2008 vol. 10(Issue 1) pp:98-103

Publication Date(Web):15 Nov 2007

DOI:10.1039/B710041H

Caprolactam (CPL) is a widely used chemical intermediate for the production of Nylon-6. However, existing synthetic routes in industry have severe drawbacks. The development on the synthesis of CPL from 6-aminocapronitrile (ACN), using near- and supercritical water as the solvent, reactant and catalyst, is described in this paper. The two-step reaction (hydrolysis and cyclization) to produce CPL is combined in a single process, by using a continuous-flow system. Effects of pressure, temperature, residence time and the concentration of ACN were studied. The high-temperature high-pressure environment possesses unique properties which result in very efficient catalysis. The overall CPL yield reaches 90% within a short residence time (<2 min).

The synthesis of o-cyclohexylphenol in supercritical carbon dioxide: towards a continuous two-step reaction

Co-reporter:Rodrigo Amandi, Katherine Scovell, Peter Licence, Tobias J. Lotz and Martyn Poliakoff

Green Chemistry 2007 vol. 9(Issue 7) pp:797-801

Publication Date(Web):20 Mar 2007

DOI:10.1039/B618727G

The use of supercritical carbon dioxide, scCO2, as an environmentally friendly reaction medium for the continuous synthesis of the fine chemical o-cyclohexylphenol has been investigated. The alkylation of phenol was carried out using a solid acid catalyst, γ-Al2O3, using both cyclohexene and cyclohexanol as alkylating agents. Though cheaper, cyclohexanol gave poorer results because of the water formed in the reaction inhibiting the catalyst performance. The possibility of performing the reaction as a two-step process was then investigated. The dehydration of cyclohexanol over the same catalyst was found to be quantitative. Clearly, the water by-product must be eliminated before the alkylation step and, although this was found to be difficult to achieve on a small scale, the process looks promising as a two-step reaction.

Catalytic selective partial oxidations using O2 in supercriticalwater: the continuous synthesis of carboxylic acids

Co-reporter:Joan Fraga-Dubreuil, Eduardo Garcia-Verdugo, Paul A. Hamley, Eva M. Vaquero, Lucinda M. Dudd, Ian Pearson, Duncan Housley, Walt Partenheimer, W. Barry Thomas, Keith Whiston and Martyn Poliakoff

Green Chemistry 2007 vol. 9(Issue 11) pp:1238-1245

Publication Date(Web):20 Jul 2007

DOI:10.1039/B706730E

A variety of different alkylaromatic compounds having a range of alkyl groups (methyl, ethyl and isopropyl), varying aromatic groups (benzene, naphthalene and pyridine), and largely different ring electron densities (toluene and 3,4-dimethoxytoluene) have been successfully oxidized selectively to aromatic aldehyde and carboxylic acids in sub- and supercriticalwater using a continuous reactor under a wide range of experimental conditions. The estimated difference in initial reactivities of these substrates is approximately 10000. Selected yields include toluene → benzoic acid (83%), isopropylbenzene → benzoic acid (46%), ethylbenzene → benzoic acid (68%), 2,6-dimethylnaphthalene → 2,6-naphthalenedicarboxylic acid (25%; co-oxidized with p-xylene) and 3,4-dimethoxytoluene → 3,4-dimethoxybenzoic acid (60%). 2-Nitrotoluene gave very poor yields, consistent with previous attempts to oxidize this substance homogeneously. For the first time, the reactivities and carboxylic acid yields of all three isomers of methylpyridine (picoline) have been determined. The initial reactivities are 3-isomer > 2-isomer > 4-isomer, the thermal decarboxylation rates are 2-isomer ≫ 3-isomer > 4-isomer, and the best yields are 3-isomer > 4-isomer > 2-isomer, with maximum yields of 50, 33, and 18 mol% respectively.

Rapid and clean synthesis of phthalimide derivatives in high-temperature, high-pressure H2O/EtOH mixtures

Co-reporter:Joan Fraga-Dubreuil, Gürbüz Çomak, Alasdair W. Taylor and Martyn Poliakoff

Green Chemistry 2007 vol. 9(Issue 10) pp:1067-1072

Publication Date(Web):01 Jun 2007

DOI:10.1039/B704405D

A variety of phthalimide derivatives have been synthesised effectively in high-temperature, high-pressure H2O/EtOH mixtures (HTHP-H2O/EtOH) as the solvent. This clean method is based on the condensation of o-phthalic acid and amines and affords phthalimide compounds as pure crystals in most cases, because of the dehydrating effect and change in solvation properties of H2O/EtOH at high pressures and temperatures. After conducting a series of model reactions, it was found that a mixture, 1/1 v/v H2O/EtOH, was appropriate for obtaining good yields combined with high purity of the phthalimides. Moderate to excellent yields were obtained depending on the nature of the amine. Aromatic amines generally afforded higher yields than aliphatic ones except for 3-hydroxypropylamine, where a yield up to 95% was obtained.

Maximising opportunities in supercritical chemistry: the continuous conversion of levulinic acid to γ-valerolactone in CO2

Co-reporter:Richard A. Bourne, James G. Stevens, Jie Ke and Martyn Poliakoff

Chemical Communications 2007 (Issue 44) pp:4632-4634

Publication Date(Web):16 Oct 2007

DOI:10.1039/B708754C

Phase behaviour is manipulated during the hydrogenation of aqueous levulinic acid in supercritical CO2 to separate almost pure γ-valerolactone from water and unreacted acid with reduced energy requirements compared to conventional processing.

Continuous Flow Hydrogenation of a Pharmaceutical Intermediate, [4-(3,4-Dichlorophenyl)-3,4-dihydro-2H-naphthalenyidene]methylamine, in Supercritical Carbon Dioxide

Co-reporter:Peter Clark;Andy Wells

Advanced Synthesis & Catalysis 2007 Volume 349(Issue 17-18) pp:

Publication Date(Web):21 NOV 2007

DOI:10.1002/adsc.200700395

The hydrogenation of complex pharmaceutical intermediate, rac-sertraline imine has been optimized as a continuous flow process utilizing a palladium/calcium carbonate (Pd/CaCO₃) catalyst and hydrogen in supercritical carbon dioxide (scCO₂). Superior levels of selectivity were obtained in the flow system possibly attributable to the heat transfer properties of scCO₂ which help to remove excess heat from the catalyst surface.

Empowering Green Chemists in Ethiopia

Co-reporter:Nigist Asfaw;Peter Licence;Temechegn Engida

Science 2007 Volume 316(Issue 5833) pp:1849-1850

Publication Date(Web):29 Jun 2007

DOI:10.1126/science.1144439

Summary

Collaborations between scientists in economically developed countries and their African colleagues can be inspiring and productive.

The application of a shear mode piezoelectric sensor to monitoring the high-pressure phase behaviour of asymmetric binary systems

Co-reporter:Jie Ke, Katherine E. Reid, Martyn Poliakoff

The Journal of Supercritical Fluids 2007 Volume 40(Issue 1) pp:27-39

Publication Date(Web):February 2007

DOI:10.1016/j.supflu.2006.05.003

We demonstrate for the first time that high-pressure phase diagrams can be measured in a simple, objective and fully automated manner for complex binary fluid mixtures. Supercritical CO2 is becoming of increasing industrial importance. Many of the important binary systems with CO2 are highly asymmetric, and exhibit a variety of the phase behaviour from liquid–liquid immiscibility to discontinuous critical loci. We investigate the possibility of mapping these different types of phase diagram using a single shear-mode piezoelectric sensor. We focus on two systems (1-octanol + CO2 and 2-octanol + CO2). We show that the existence of three phases (liquid–liquid–vapour) can be detected by the presence of two discontinuities when the impedance minimum of the sensor is measured as a function of fluid volume. This method is used to measure the three-phase coexistence curve quantitatively for the 1-octanol + CO2 system and the result is in good agreement with literature data. By analyzing the impedance minimum along the p–T phase boundary, we have found that the vapour–liquid critical locus of 2-octanol + CO2 is interrupted by the occurrence of a previously unobserved liquid–liquid immiscibility. For both systems, we have used the critical points, located either by the isochoric method or extrapolated from composition/T/p phase envelope to construct a p,T-projection with characteristic features which allow the particular mixture to be classified to its appropriate type (i.e., 1-octanol + CO2, Type III; 2-octanol + CO2, Type IV).

In situ generation of hydrogen for continuous hydrogenation reactions in high temperature water

Co-reporter:Eduardo Garcia-Verdugo, Zhimin Liu, Eliana Ramirez, Juan Garcia-Serna, Joan Fraga-Dubreuil, Jason R. Hyde, Paul A. Hamley and Martyn Poliakoff

Green Chemistry 2006 vol. 8(Issue 4) pp:359-364

Publication Date(Web):31 Jan 2006

DOI:10.1039/B515470G

The thermal decomposition of HCO2H or preferably, HCO2X (X = Na or NH4) can be used to generate H2 for the continuous hydrogenation of aromatic and cyclic aldehydes, ketones and nitroaromatics in high temperature pressurised water (HTPW). This means that hydrogenation reactions can be carried out in exactly the same equipment as has previously been used for selective oxidation in HTPW, thus facilitating relatively simple application of these reactions for non-specialists.

Continuous kinetic resolution catalysed by cross-linked enzyme aggregates, ‘CLEAs’, in supercritical CO2

Co-reporter:Helen R. Hobbs, Betti Kondor, Phil Stephenson, Roger A. Sheldon, Neil R. Thomas and Martyn Poliakoff

Green Chemistry 2006 vol. 8(Issue 9) pp:816-821

Publication Date(Web):17 Jul 2006

DOI:10.1039/B604738F

We report the use of cross-linked enzyme aggregates (CLEAs®) to catalyse the kinetic resolution of tetralol and 1-phenylethanol in a continuous supercritical carbon dioxide (scCO2) system. We describe the performance of the CLEA from Candida antarctica lipase B (CALB) and compare this to the catalytic activity of Novozym 435 (CALB immobilised on a macroporous acrylic resin). In addition, we report a two-stage reaction with the kinetic resolution of 1-phenylethanol performed in series with the metal (Pd) catalysed hydrogenation of acetophenone. Reactions performed in series have a potential economic advantage as the second, and subsequent reactions do not require additional expenditure of energy for re-pressurization of solvent.

Continuous Asymmetric Hydrogenation in Supercritical Carbon Dioxide using an Immobilised Homogeneous Catalyst

Co-reporter:Phil Stephenson;Betti Kondor;Peter Licence;Katherine Scovell;Stephen K. Ross

Advanced Synthesis & Catalysis 2006 Volume 348(Issue 12-13) pp:

Publication Date(Web):11 AUG 2006

DOI:10.1002/adsc.200606172

Continuous flow supercritical carbon dioxide (scCO₂) has previously been shown (P. Stephenson, P. Licence, S. K. Ross, M. Poliakoff, Green Chem.2004, 6, 521) to be a viable medium for conducting continuous asymmetric hydrogenation when it is combined with an appropriate enantioselective catalyst. Here we examine the use of a composite catalyst immobilisation system modified with several different types of asymmetric bisphosphine ligands in continuous flow scCO₂. In particular, proprietary ligands from Solvias AG were found to be the most successful, with Josiphos 001 improving the enantiomeric excess (ee) to>80 % in the asymmetric hydrogenation of dimethyl itaconate (DMIT); this ee is higher than that reported for the batch hydrogenation of DMIT using a homogeneous catalyst fully dissolved in scCO₂ (S. Lange, A. Brinkmann, P. Trautner, K. Woelk, J. Bargon, W. Leitner, Chirality2000, 12, 450).

The catalytic oxidation of benzoic acid to phenol in high temperature water

Co-reporter:Joan Fraga-Dubreuil, Juan Garcia-Serna, Eduardo Garcia-Verdugo, Lucinda M. Dudd, Graham R. Aird, W. Barry Thomas, Martyn Poliakoff

The Journal of Supercritical Fluids 2006 Volume 39(Issue 2) pp:220-227

Publication Date(Web):December 2006

DOI:10.1016/j.supflu.2005.12.012

The oxidation of benzoic acid (BA) to phenol (the Dow Phenol Process) has been studied in high temperature water (HTW) using a continuous flow system over various metal oxide heterogeneous catalysts: NiO, CuO, Carulite®, MnO2 and Al2O3. Excellent selectivities (>99%) and good yields for phenol (up to 70%) were obtained. The reaction conditions were optimised by varying the temperature, the pressure and the effect of O2. Experiments were carried out for sustained periods in order to study the catalyst deactivation. The results are presented in most of the cases in dynamic conditions; results observed versus time-on-stream for each catalyst tested. Carulite® 300 catalyst was the most effective with a good activity/robustness over time-on-stream. Activity and regeneration of the catalyst with oxygen is reported. Overall HTW shows considerable potential as a medium for this process. Possibilities for extending this chemistry are discussed.

The automation of continuous reactions in supercritical CO2: the acid-catalysed etherification of short chain alcohols

Co-reporter:Ben Walsh, Jason R. Hyde, Peter Licence and Martyn Poliakoff

Green Chemistry 2005 vol. 7(Issue 6) pp:456-463

Publication Date(Web):05 Apr 2005

DOI:10.1039/B413890B

We describe a new, automated apparatus for continuous catalytic reactions in supercritical carbon dioxide, scCO2. The reactor incorporates on-line sampling, enabling us to quantify gaseous products such as light alkenes, which would normally be lost in the decompression stage of more conventional supercritical reactors. The on-line sampling is coupled to a gas chromatograph running an isothermal program, which provides automated analysis of the reaction products. We illustrate the operation of the reactor by studying the acid-catalysed etherification of linear alcohols, C1 to C5, both individually and in pairs, over a range of temperatures and pressures equating to a total of 180 different experiments.

Continuous hydrogenation reactions in supercritical CO2 “without gases”

Co-reporter:Jason R. Hyde, Ben Walsh, Jasbir Singh and Martyn Poliakoff

Green Chemistry 2005 vol. 7(Issue 5) pp:357-361

Publication Date(Web):18 Apr 2005

DOI:10.1039/B419276A

Continuous fixed-bed hydrogenation reactions are one of the most promising reactions studied under supercritical conditions. A reactor and supporting equipment has been developed in a collaboration between the University of Nottingham and HEL Ltd. to provide the means for small-scale experimental research. The high pressure gases required to achieve the supercritical state are not supplied by bottled or liquefied gases, but by the in situ decomposition of formic acid, HCO2H, which can be selectively decomposed to produce CO2 and H2. These gases can be used directly as both the supercritical solvent and reagent gases. Further control of the H2 concentration can be achieved by the parallel decomposition of other liquid precursors, namely ethyl formate HCO2Et, which can produce C2H6 + CO2. We report the hydrogenation of several organic substrates to demonstrate this approach, its application in research and its potential as a development tool.

Simultaneous continuous partial oxidation of mixed xylenes in supercritical water

Co-reporter:Eduardo Garcia-Verdugo, Joan Fraga-Dubreuil, Paul A. Hamley, W. Barry Thomas, Keith Whiston and Martyn Poliakoff

Green Chemistry 2005 vol. 7(Issue 5) pp:294-300

Publication Date(Web):13 Apr 2005

DOI:10.1039/B419098J

In this paper we show that a mixture of xylenes can be simultaneously oxidised in supercritical water (scH2O) in a continuous mode to a mixture of the corresponding carboxylic acids in high combined yield, despite the differences in reactivity of the xylene isomers in conventional oxidation. The single phase environment in scH2O together with the effect of higher temperatures should increase the reaction rate for each of these oxidation reactions and thus reduce the reactivity differences between the components of the C8 refinery mixture. Such a process should lead to a considerable reduction in the overall energy input for the oxidation of xylenes. The process in scH2O described here could simplify the downstream purification processes to a simple crystallization process. This is commercially important, because the purification process can be as expensive as the reaction producing the product. Furthermore, the oxidation of mixed xylenes could avoid the need not only for downstream purification, but also for the upstream separation of the xylene isomers. The use of high temperature water also offers significant cost advantages through enhanced energy recovery, due to a higher process temperature. Finally, the process totally eliminates the use of organic solvents.

Continuous reactions in supercritical fluids; a cleaner, more selective synthesis of thymol in supercritical CO2

Co-reporter:Rodrigo Amandi, Jason R. Hyde, Stephen K. Ross, Tobias J. Lotz and Martyn Poliakoff

Green Chemistry 2005 vol. 7(Issue 5) pp:288-293

Publication Date(Web):11 Apr 2005

DOI:10.1039/B418983C

Continuous fixed-bed catalytic Friedel–Crafts alkylation of m-cresol with different alkylating agents, isopropanol (IPA) and propylene, has been carried out using supercritical CO2, scCO2, as an alternative and more environmentally friendly reaction medium, for the synthesis of the fine chemical thymol. Both a solid Lewis acid catalyst (γ-Al2O3) and a solid Brønsted acid catalyst (Nafion® SAC-13) have been investigated over a range of reaction conditions to optimise yield and selectivity for thymol. The reaction product distribution was found to be related to the type of catalyst employed. This is likely to have been due to the different reaction pathways through which the reaction occurred, a direct Friedel–Crafts alkylation in the case of Brønsted type acids and a Fries rearrangement when employing the Lewis catalyst. The new technique of 2DCOR-GC analysis was employed to establish the order of formation of the different species generated in the reaction over the two catalysts in scCO2.

Hydrogen-Catalyzed Dehydrogenation: A Supercritical Conundrum

Co-reporter:Jason R. Hyde, Ben Walsh,Martyn Poliakoff

Angewandte Chemie International Edition 2005 44(46) pp:7588-7591

Publication Date(Web):

DOI:10.1002/anie.200502049

“Hydrogen-Catalyzed” Dehydrogenation: A Supercritical Conundrum

Co-reporter:Jason R. Hyde Dr.;Ben Walsh Dr.

Angewandte Chemie 2005 Volume 117(Issue 46) pp:

Publication Date(Web):31 OCT 2005

DOI:10.1002/ange.200502049

Hot Spots: Die überraschende, offenbar katalytische Wirkung von H₂ bei der Dehydrierung von 1 in überkritischem CO₂ ist das Ergebnis thermischer Hot Spots (siehe Thermobild des Reaktors), die zu Beginn im Katalysatorbett durch eine exotherme Hydrierung erzeugt werden. Dieses punktuelle Erhitzen erzwingt die Dehydrierung und ermöglicht einen einfachen Zugang zu Dien 2.

Continuous catalytic asymmetric hydrogenation in supercritical CO2

Co-reporter:Phil Stephenson, Peter Licence, Stephen K. Ross and Martyn Poliakoff

Green Chemistry 2004 vol. 6(Issue 10) pp:521-523

Publication Date(Web):29 Sep 2004

DOI:10.1039/B411955J

Continuous hydrogenation in supercritical fluids has been shown to be a technically viable alternative to traditional batch-wise methodologies. Clearly, the next stage of development of this technology is the application of immobilised enantioselective catalysis in the preparation of optically active products. Enantioselective hydrogenation has been successfully carried out in supercritical carbon dioxide using batch-type reactors but has yet to be efficiently carried out continuously. Here we examine an established method of catalyst immobilisation and demonstrate its suitability for application in continuous reactors using supercritical carbon dioxide as solvent.

Is it Possible to Achieve Highly Selective Oxidations in Supercritical Water? Aerobic Oxidation of Methylaromatic Compounds

Co-reporter:Eduardo Garcia-Verdugo;Eleni Venardou;W. Barry Thomas;Keith Whiston;Walter Partenheimer;Paul A. Hamley

Advanced Synthesis & Catalysis 2004 Volume 346(Issue 2-3) pp:

Publication Date(Web):29 MAR 2004

DOI:10.1002/adsc.200303218

We have demonstrated that different methylaromatic compounds [1,4-dimethylbenzene (p-xylene), 1,3-dimethylbenzene (m-xylene), 1,2-dimethylbenzene (o-xylene), 1,3,5-trimethylbenzene (mesitylene) and 1,2,4-trimethylbenzene (pseudocumene)] can be aerobically oxidized in supercritical water (scH₂O) using manganese(II) bromide as catalyst to give corresponding carboxylic acids in the continuous mode over a sustained period of time in good yield. No partially oxidized intermediates (i.e., toluic acid and benzaldehydes) were detected for the dimethylbenzenes and mesitylene reactions. By fine tuning pressure and temperature, scH₂O becomes a solvent with physical properties suitable for single-phase oxidation since both organic substrate and oxygen are soluble in scH₂O. There is a strong structural similarity of metal/bromide coordination compounds in the active oxidation solvents (acetic acid and scH₂O) which does not exist in the much less active H₂O at lower temperatures. This may account for the successful catalysis of the reactions reported herein. Aromatic acids produced by the loss of one methyl group occurred in all of these reactions, i.e., 3–6% benzoic acid formed during the oxidation of the dimethylbenzenes. Part of this loss is thought to be due to thermal decarboxylation. The thermal decarboxylation process is monitored via Raman spectroscopy.

The fibre optic reflectometer: A new and simple probe for refractive index and phase separation measurements in gases, liquids and supercritical fluids

Co-reporter:Mikhail V. Avdeev, Aleksei N. Konovalov, Viktor. N. Bagratashvili, Vladimir K. Popov, Svetlana I. Tsypina, Maia Sokolova, Jie Ke and Martyn Poliakoff

Physical Chemistry Chemical Physics 2004 vol. 6(Issue 6) pp:1258-1263

Publication Date(Web):11 Feb 2004

DOI:10.1039/B311207A

A fibre optic reflectometer (FOR) has been developed to monitor refractive index (n) and density (ρ) changes in gases, liquids and supercritical fluids (SCFs). The key operating principle is the measurement of the intensity of light from a light emitting diode, LED, which is reflected from the end of a fibre immersed in the medium. The amount of reflected light depends on the difference between the refractive indices of the fibre and the medium. The refractive index of the medium is related in turn to its density. The FOR is particularly sensitive to phase separation, a key aspect of supercritical fluid systems, because of the density discontinuity which accompanies the separation. This device allows the collection of data with a high spatial (9 μm-fibre diameter) and time (∼0.02 s) resolution. The small size of the fibre optic probe means that it can be put into operating reactors and even catalyst beds. Experiments are described with pure CO2 and CHF3, and mixtures CO2+cyclohexane and CO2+MeOH over wide pressure and temperatures ranges. The measurements are in excellent agreement with published data for these systems.

On-line monitoring of the hydrolysis of acetonitrile in near-critical water using Raman spectroscopy

Co-reporter:Eleni Venardou, Eduardo Garcia-Verdugo, Stephen J Barlow, Yuri E Gorbaty, Martyn Poliakoff

Vibrational Spectroscopy 2004 Volume 35(1–2) pp:103-109

Publication Date(Web):17 June 2004

DOI:10.1016/j.vibspec.2003.12.003

The hydrolysis of CH3CN in near-critical water, without added catalyst, has been successfully monitored with on line Raman spectroscopy, up to 350 °C at 300 bar. Using a unique miniature high pressure and high temperature (HTHP) spectroscopic cell, in situ quantitative measurements with Raman spectroscopy have allowed the pseudo-first-order rate constant and the activation energy for the reaction to be calculated. The effects of temperature, pressure, density, dielectric constant, ionic product of water and initial CH3CN concentration on the reaction rate have also been investigated. The reaction involves the formation of CH3CONH2 as an intermediate, and gives CH3COOH as the final product. No other products have been detected in the effluent. Water plays the role of solvent, reactant and acid catalyst at the same time, whereas the reaction also shows an autocatalytic effect, due to CH3COOH which accumulates in the system as the reaction progresses.

Experimental spectroscopic high-temperature high-pressure techniques for studying liquid and supercritical fluids

Co-reporter:Yuri E Gorbaty, Galina V Bondarenko, Eleni Venardou, Stephen J Barlow, Eduardo Garcia-Verdugo, Martyn Poliakoff

Vibrational Spectroscopy 2004 Volume 35(1–2) pp:97-101

Publication Date(Web):17 June 2004

DOI:10.1016/j.vibspec.2003.12.002

The purpose of this paper is to share our many years of experience in designing and using high-temperature, high-pressure (HTHP) devices for studying the behavior of fluids and chemical reactions at elevated temperatures and pressures. The HTHP cells for IR and Raman spectroscopic techniques described in the paper are unique and can be used at pressures of up to 1500 bar and temperatures up to 550 °C. However, the most attractive feature of these designs is that they provide high accuracy of measurements, in most cases even higher than that achieved with standard cells at ambient conditions. The performance of these IR and Raman HTHP spectroscopic cells is demonstrated using some representative spectra.

Sensing the Critical Point of High-Pressure Mixtures

Co-reporter:Jie Ke Dr.;Robert M. Oag Dr.;P. J. King Dr.;Michael W. George

Angewandte Chemie 2004 Volume 116(Issue 39) pp:

Publication Date(Web):29 SEP 2004

DOI:10.1002/ange.200460624

Neu, allgemein und objektiv ist die hier vorgestellte Bestimmung kritischer Punkte von Fluidmischungen (siehe Bild). Neu, weil sie die Tatsache nutzt, dass sich die flüssige Phase bevorzugt an der Sensoroberfläche bildet. Allgemein, weil sie mit jedem beliebigen oberflächenempfindlichen Sensor gelingt. Objektiv, weil sie auf einem numerischen Sensorwert und nicht auf der bei Phasengleichgewichtsstudien sonst üblichen visuellen Bildanalyse beruht.

Sensing the Critical Point of High-Pressure Mixtures

Co-reporter:Jie Ke Dr.;Robert M. Oag Dr.;P. J. King Dr.;Michael W. George

Angewandte Chemie International Edition 2004 Volume 43(Issue 39) pp:

Publication Date(Web):29 SEP 2004

DOI:10.1002/anie.200460624

A new, general and objective approach to locating critical points of fluid mixtures is described (see picture). It is new because it exploits the fact that the liquid phase forms preferentially on the surface of the sensor. It is general because it can be used with any type of surface-sensitive sensor, and it is objective because it is based on the numerical output of a sensor rather than the visual image normally used for phase equilibrium studies.

Synthesis of benzimidazoles in high-temperature water

Co-reporter:Lucinda M. Dudd, Eleni Venardou, Eduardo Garcia-Verdugo, Peter Licence, Alexander J. Blake, Claire Wilson and Martyn Poliakoff

Green Chemistry 2003 vol. 5(Issue 2) pp:187-192

Publication Date(Web):12 Mar 2003

DOI:10.1039/B212394K

The objective of this research was to conduct constructive organic chemistry in water and to achieve yields that were comparable to, or better than, those in conventional media. The synthesis of 2-phenylbenzimidazole from 1,2-phenylenediamine and benzoic acid was chosen as a benchmark reaction. The reaction parameters, such as temperature, density and reaction time, have been systematically studied to understand whether the solvent properties of high-temperature water can have a positive effect on the chemistry. The reaction was performed in a new design of batch-type autoclave and was also monitored in situ by UV-vis spectroscopy. By tuning the parameters, the yield has been optimised to around 90%. The optimised conditions were then applied to related benzimidazoles, some of which crystallised from solution in situ to yield single crystals that were sufficiently pure to be analysed directly by X-ray diffraction, without any further purification.

Study of the reaction of Rh(acac)(CO)2 with alkenes in polyethylene films under high-pressure hydrogen and the Rh-catalysed hydrogenation of alkenes

Co-reporter:Jie Zhang, Xue-Zhong Sun, Martyn Poliakoff, Michael W. George

Journal of Organometallic Chemistry 2003 Volume 678(1–2) pp:128-133

Publication Date(Web):15 July 2003

DOI:10.1016/S0022-328X(03)00439-X

The thermal reaction of Rh(acac)(CO)2 with alkenes has been studied both in the absence and in the presence of high-pressure hydrogen using in situ FTIR and polymer matrix techniques. A series of rhodium alkenes complexes, Rh(acac)(CO)(alkene) (alkene=ethene, propene, 1-butene, 1-octene and trans-3-octene), have been characterized using IR spectroscopy. In the presence of a high-pressure hydrogen, catalytic hydrogenation of alkenes was achieved using Rh(acac)(CO)2 within the polyethylene matrix. These results suggest that this hydrogenation process follows the so-called “olefin route” operating via a sequence of ligand loss, binding of an alkene, oxidative addition of hydrogen to the rhodium metal centre, insertion of the coordinated alkene into the MH bond and finally reductive elimination of the alkane. Rh(acac)(CO) appears to be the active catalytic species in this process. High-pressure polymer matrix techniques have allowed us to unravel some of the interconversions of the catalytic species involved in this catalytic process.The thermal reaction of Rh(acac)(CO)2 with alkenes has been studied both in the absence and in the presence of high-pressure hydrogen using a high-pressure cell for in situ FTIR and polymer matrix techniques. A series of rhodium alkenes complexes, Rh(acac)(CO)(alkene), have been characterized using IR, and the catalytic hydrogenation of alkenes has been monitored.

Chemical Emissions: An Ongoing Issue

Co-reporter:Alan H. Lockwood

Science 2002 Vol 298(5593) pp:541-542

Publication Date(Web):18 Oct 2002

DOI:10.1126/science.298.5593.541

Selective partial oxidation in supercritical water: the continuous generation of terephthalic acid from para-xylene in high yield

Co-reporter:Paul A. Hamley, Thomas Ilkenhans, Jeremy M. Webster, Eduardo Garcia-Verdugo, Eleni Venardou, Matthew J. Clarke, Rita Auerbach, W. Barry Thomas, Keith Whiston and Martyn Poliakoff

Green Chemistry 2002 vol. 4(Issue 3) pp:235-238

Publication Date(Web):24 Apr 2002

DOI:10.1039/B202087B

The continuous selective oxidation of p-xylene (p-X) by O2 (generated by thermal decomposition of aqueous H2O2) catalyzed by MnBr2 in supercritical H2O at ca. 400 oC is reported for the first time. The selectivity for terephthalic acid (TA) is >90%. Compared to existing industrial processes, the reaction has the potential for a significant increase in energy efficiency and a substantial reduction in waste. This reaction is significant because the presence of H2O lowers the catalytic activity of MnBr2 in the conventional route to TA via oxidation of p-X in CH3COOH.

The Supercritical Fluid Antisolvent Synthesis of C60(C2Hx) (x=4 or 6); The Crystal Structures of Two Materials Which Were Thought Unlikely to Exist

Co-reporter:Adam O'Neil;Claire Wilson Dr.;Jeremy M. Webster Dr.;Francis J. Allison Dr.;Judith A. K. Howard

Angewandte Chemie International Edition 2002 Volume 41(Issue 20) pp:

Publication Date(Web):18 OCT 2002

DOI:10.1002/1521-3773(20021018)41:20<3796::AID-ANIE3796>3.0.CO;2-T

The intercalation of ethane and ethene into the octahedral interstitial sites of the C₆₀ lattice can be achieved by antisolvent precipitation, using supercritical C₂H₄ and C₂H₆. This method of crystallization (see picture), which has yielded unprecedented intercalation compounds with hydrocarbons once thought too large to form such species, should be applicable to other gases, solvents, and fullerenes.

The Supercritical Fluid Antisolvent Synthesis of C60(C2Hx) (x=4 or 6); The Crystal Structures of Two Materials Which Were Thought Unlikely to Exist

Co-reporter:Adam O'Neil;Claire Wilson Dr.;Jeremy M. Webster Dr.;Francis J. Allison Dr.;Judith A. K. Howard

Angewandte Chemie 2002 Volume 114(Issue 20) pp:

Publication Date(Web):18 OCT 2002

DOI:10.1002/1521-3757(20021018)114:20<3950::AID-ANGE3950>3.0.CO;2-#

Überkritisches C₂H₄und C₂H₆ dienen gleichzeitig als Fällungsmittel und intercalieren in die oktaedrischen Zwischenräume des C₆₀-Gitters. Auf diese Weise werden Intercalationsverbindungen mit solchen Kohlenwasserstoffen kristallisiert, die wegen ihrer Größe bislang nicht intercalierten. Der Weg zu Intercalationsverbindungen mit anderen Gasen, Lösungsmitteln und Fullerenen ist freigemacht.

The continuous hydrothermal synthesis of nano-particulate ferrites in near critical and supercritical water

Co-reporter:Albertina Cabañas and Martyn Poliakoff

Journal of Materials Chemistry A 2001 vol. 11(Issue 5) pp:1408-1416

Publication Date(Web):28 Mar 2001

DOI:10.1039/B009428P

Magnetic spinel type oxides such as magnetite, Fe3O4, cobalt, nickel, and zinc ferrites, MFe2O4 (M = Co, Ni, Zn) and the mixed nickel and cobalt ferrite, NixCo1 − xFe2O4 have been synthesised continuously by the hydrolysis and simultaneous oxidation of mixtures of Fe(II) acetate and different M(II) acetates in near-critical and supercritical water using a flow reactor. The materials have been characterised by powder X-ray diffraction (PXD) and, in selected cases, by transmission electron microscopy (TEM). The bulk composition of the samples was determined by Atomic Absorption analysis (AA). Additionally, Energy-dispersive Detection X-ray analysis (EDX) was carried out on some of the samples. TEM pictures showed a “bimodal” particle size distribution: small particles of ca. 10 nm and larger particles of up to 100 nm, both of which are highly crystalline. Possible reaction mechanisms are discussed, which may be responsible for the observed morphology. The effects of temperature and residence time on the reaction have been studied.

Acoustic measurements of critical points for four-component mixtures in hydroformylation reactions in carbon dioxide

Co-reporter:Jie Ke, Buxing Han, Michael W. George, Haike Yan, Martyn Poliakoff

Fluid Phase Equilibria 2001 Volume 185(1–2) pp:327-337

Publication Date(Web):30 July 2001

DOI:10.1016/S0378-3812(01)00481-2

A simple acoustic technique has been used to study the vapour–liquid critical points of the reaction mixtures of hydroformylation in carbon dioxide. The systems CO2+CO+H2+propene and CO2+CO+H2+hex-1-ene have been investigated. These two quaternary systems were measured by the pseudo-binary approach (i.e. the ratio of alkene, CO and H2 being held constant). The effects of the solutes (alkene, CO and H2) on the critical points in the CO2-rich fluids are discussed.

The Structure of [Fe(CO)4]—An Important New Chapter in a Long-Running Story

Co-reporter:Martyn Poliakoff ;James J. Turner

Angewandte Chemie International Edition 2001 Volume 40(Issue 15) pp:

Publication Date(Web):2 AUG 2001

DOI:10.1002/1521-3773(20010803)40:15<2809::AID-ANIE2809>3.0.CO;2-U

The structure of the singlet state (¹A₁) of [Fe(CO)₄] in the gas phase (see picture) has been determined by a combination of laser photochemistry of [Fe(CO)₅] and electron diffraction imaging. The ground state of [Fe(CO)₄] is known to be a triplet species (³B₂), and this is the species detected in picosecond time-resolved IR experiments with [Fe(CO)₅] in solution. This is an appropriate moment to survey the state of knowledge on [Fe(CO)₄], beginning from the first low-temperature matrix experiments.

Die Struktur von [Fe(CO)4] – ein neues Kapitel einer langen Geschichte

Co-reporter:Martyn Poliakoff ;James J. Turner

Angewandte Chemie 2001 Volume 113(Issue 15) pp:

Publication Date(Web):3 AUG 2001

DOI:10.1002/1521-3757(20010803)113:15<2889::AID-ANGE2889>3.0.CO;2-I

Die Struktur von Singulett(¹A₁)-[Fe(CO)₄] in der Gasphase (siehe Bild) wurde durch Kombination der Laser-Photolyse von [Fe(CO)₅] mit einem Elektronenbeugungsverfahren bestimmt. Der Grundzustand von [Fe(CO)₄] ist bekanntermaßen ein Triplettzustand (³B₂), wie in zeitaufgelösten Picosekunden-IR-Messungen an [Fe(CO)₅] in Lösung nachgewiesen wurde. Ein guter Zeitpunkt, sich beginnend mit den ersten Tieftemperatur-Matrixisolationsversuchen einen Überblick über den Kenntnisstand bezüglich [Fe(CO)₄] zu verschaffen.

Continuous, selective hydroformylation in supercritical carbon dioxide using an immobilised homogeneous catalyst

Co-reporter:Nicola J. Meehan, Albertus J. Sandee, Joost N. H. Reek, Paul C. J. Kamer, Piet W. N. M. van Leeuwen and Martyn Poliakoff

Chemical Communications 2000 (Issue 16) pp:1497-1498

Publication Date(Web):19 Jul 2000

DOI:10.1039/B002526G

A continuous process for the selective hydroformylation of higher olefins in supercritical carbon dioxide (scCO2) is presented; the catalyst shows high selectivity and activity over several hours and no decrease in performance was observed over several days.

A continuous and clean one-step synthesis of nano-particulate Ce1−xZrxO2 solid solutions in near-critical water

Co-reporter:Albertina Cabanas, Jawwad A. Darr, Edward Lester and Martyn Poliakoff

Chemical Communications 2000 (Issue 11) pp:901-902

Publication Date(Web):09 May 2000

DOI:10.1039/B001424I

Gram-scale quantities of microcrystalline powdered CeO2–ZrO2 solid solutions can be produced continuously in a near-critical water flow reactor at ca. 300 °C and 25 MPa; rapid hydrothermal co-precipitation leads to nano-particulate Ce1−xZrxO2 (x = 0 to 1), the composition of which is merely determined by the initial concentrations of Ce4+ and Zr4+ ions in the starting solution.

Continuous Reactions in Supercritical Water: A New Route to La2CuO4 with a High Surface Area and Enhanced Oxygen Mobility

Co-reporter:Alexer A. Galkin Dr.;Boris G. Kostyuk Dr.;Valery V. Lunin

Angewandte Chemie 2000 Volume 112(Issue 15) pp:

Publication Date(Web):2 AUG 2000

DOI:10.1002/1521-3757(20000804)112:15<2850::AID-ANGE2850>3.0.CO;2-7

Intermediates in organometallic and organic chemistry: spectroscopy, polymers, hydrogenation and supercritical fluids

Co-reporter:Michael W. George

Journal of Physical Organic Chemistry 1998 Volume 11(Issue 8‐9) pp:589-596

Publication Date(Web):18 DEC 1998

DOI:10.1002/(SICI)1099-1395(199808/09)11:8/9<589::AID-POC67>3.0.CO;2-F

IR spectroscopy has transformed the study of mechanistic organometallic chemistry. Reaction intermediates can now be detected and characterized; their kinetics can be measured and their behaviour understood. However, the field is not static. New techniques are still being developed. We focus here on hydrogenation and related reactions describing (i) a miniature low-temperature/high-pressure cell, which allows photochemical reactions to be studied under high pressures of gases, (ii) the use of flow reactors for continuous reactions in supercritical fluids, including hydrogenation of organic compounds, and (iii) the use of supercritical fluid solutions for studying weak metal–ligand interactions by nanosecond time-resolved IR spectroscopy (TRIR) and the application of TRIR to the detection of intermediates in organic reactions. © 1998 John Wiley & Sons, Ltd.

Schwingungsspektroskopie in überkritischen fluiden Phasen: von der Analytik bis zur Synthesechemie

Co-reporter: Martyn Poliakoff;Steven M. Howdle;Sergei G. Kazarian

Angewandte Chemie 1995 Volume 107(Issue 12) pp:

Publication Date(Web):13 JAN 2006

DOI:10.1002/ange.19951071205

Überkritische fluide Phasen werden in der Chemie in zunehmendem Maße eingesetzt. Ihr Anwendungsbereich reicht von der Extraktion und Chromatographie in der analytischen Chemie bis hin zu Lösungsmitteln für die präparative Chemie und zur Herstellung neuer Materialien. Das spektroskopische Verfolgen der Vorgänge ist in der Chemie von überkritischen Systemen wichtig, wobei die Schwingungsspektroskopie sich in diesem Zusammenhang als besonders nützlich erweist, da das Schwingungsspektrum einer Verbindung für gewöhnlich recht empfindlich auf Veränderungen der Umgebung reagiert. Deshalb sind Schwingungsspektren ausgezeichnete Sonden für die in der fluiden Phase herrschenden Bedingungen. In dieser Übersicht wird eine Vielzahl von Techniken und Meßzellen für die IR- und Raman-Spektroskopie in überkritischen fluiden Phasen beschrieben und versucht, die Bandbreite der Anwendungsmöglichkeiten in solchen Phasen deutlich zu machen. Die Beispiele umfassen die Verwendung überkritischen Xenons als spektroskopisch durchlässiges Lösungsmittel für chemische Reaktionen und für die Chromatographie mit überkritischen fluiden Phasen sowie FT-IR-Detektion der Analyten, die Raman-Spektroskopie als Sonde für in überkritischem CO₂ gelöste Gase, dem Einfluß der Lösungsmitteldichte auf die Bildung von Wasserstoffbrückenbindungen in überkritischen fluiden Phasen und die Bildung inverser Micellen, das IR-spektroskopische Verfolgen der Imprägnierung oder Extraktion von Polymeren mit überkritischen fluiden Phasen und der Reaktionen von in Polymeren eingebrachten metallorganischen Verbindungen, die Reaktionen metallorganischer Verbindungen in überkritischen fluiden Phasen sowie schließlich die Verwendung von Miniatur-Durchflußreaktoren für die präparative Chemie im Labormaßstab. Alles in allem ist es unser Ziel, dem Leser eine Grundlage zu verschaffen, die es ihm ermöglicht zu beurteilen, ob solche Messungen erfolgreich auf sein eigenes spezielles Problem angewendet werden könnten.

Maximising opportunities in supercritical chemistry: the continuous conversion of levulinic acid to γ-valerolactone in CO2

Co-reporter:Richard A. Bourne, James G. Stevens, Jie Ke and Martyn Poliakoff

Chemical Communications 2007(Issue 44) pp:NaN4634-4634

Publication Date(Web):2007/10/16

DOI:10.1039/B708754C

Immobilised photosensitisers for continuous flow reactions of singlet oxygen in supercritical carbon dioxide

Co-reporter:Xue Han, Richard A. Bourne, Martyn Poliakoff and Michael W. George

Chemical Science (2010-Present) 2011 - vol. 2(Issue 6) pp:NaN1067-1067

Publication Date(Web):2011/03/11

DOI:10.1039/C0SC00641F