Composites (GrO@Cu-BTC) based on Cu-BTC and graphene oxide were synthesized by a solvothermal method for the separation of CO2/CH4 binary mixtures. The as-synthesized composites were then characterized. The isotherms of CO2 and CH4 on the as-synthesized materials were measured by the volumetric method. The isotherms and adsorption selectivities of CO2/CH4 binary mixtures were estimated on the basis of ideal adsorbed solution theory (IAST). The results showed that the composite 1GrO@Cu-BTC had a higher BET surface area and pore volume compared to the parent Cu-BTC. More importantly, its adsorption capacity for CO2 improved significantly in comparison with that of Cu-BTC, which was up to 8.19 mmol/g at 1 bar and 273 K. The dual-site Langmuir–Freundlich (DSLF) model was applied favorably for fitting experimental isotherm data of CO2 and CH4 adsorption on the samples. The predicted isotherms of the binary mixture based on IAST showed that CO2 was more favorably adsorbed than CH4 on the sample 1GrO@Cu-BTC. TPD showed that the desorption activation energy of CO2 on 1GrO@Cu-BTC was higher than that on Cu-BTC, indicating a stronger interaction between CO2 molecules and 1GrO@Cu-BTC. Thus, the CO2/CH4 adsorption selectivity of the composite 1GrO@Cu-BTC was significantly higher than that of Cu-BTC, namely, 14 at 1 bar, or 2.6 times that of Cu-BTC.

•Starch sugar was used as carbon precursor to successfully synthesize novel Glc-As adsorbents.•Their surface area reached as high as 2073 m2/g and their pore diameters fell into the region of micropores.•Glc-A-4 had super-high C2H6 uptake of 7.98 mmol/g at 288 K and 1 bar.•Glc-As exhibited greatly preferential adsorption of ethane over ethylene with selectivity of 5.98.•C2H4/C2H6 binary mixture can be well separated in the fixed bed packed with Glc-As.In this work, we reported novel glucose-based adsorbents (Glc-As) with high C2H6/C2H4 adsorption capacity and selectivity. Starch sugar (e.g., glucose, 50 wt%) was used as carbon source to prepare novel glucose-based carbon materials for C2H6/C2H4 separation. The BET surface area of the resulting Glc-As can reach as high as 2073 m2/g, and their pore diameters fell into the region of micropores benefiting adsorption of light hydrocarbons. FTIR spectra and XPS were applied to analysize the surface chemistry of the samples. It showed the presence of O functionalities in Glc-As, and its contents decreased with increasing KOH/C ratio at which the sample was activated. Glc-As achieved superior high C2H6 adsorption capacity of 7.98 mmol/g at 288 K and 1 bar, which was benefited from the abundant micropores. More importantly, Glc-As exhibited greatly preferential adsorption of C2H6 over C2H4, with the C2H6/C2H4 adsorption selectivity in the range of 2.02–5.98 at pressure below 100 kPa, higher than most reported adsorbents possessing preferential adsorption of C2H6 over C2H4. This could ascribe to the higher polarizability and larger kinetic diameter of C2H6, resulting in its stronger interaction with the pore surfaces of Glc-As compared to C2H4, and exhibiting in significantly preferential adsorption of ethane over ethylene. Besides, adsorption heat calculation showed that the isosteric heats of C2H6 adsorption on Glc-As were higher than the isosteric heats of C2H4. Fixed bed experiments showed that C2H4/C2H6 mixture can be well separated in the fixed bed packed with Glc-As. In sum, Glc-As as new carbon materials possess not only excellent stability, but also excellent adsorption properties for separation of C2H6 and C2H4, It would be promising adsorbents for the effective separation of ethane/ethylene.Download high-res image (84KB)Download full-size image

•Novel Glc-Cs adsorbents were synthesized by using starch sugar as carbon source.•Glc-Cs exhibits superhigh surface area of 3153 m2/g and pore volume of 2.06 cm3/g.•Glc-Cs possessed a high CO2 adsorption capacity up to 22.4 mmol/g at 30 bar.•The selectivity of Glc-Cs was up to 66 and 27 for CO2/N2 and CO2/CH4, separately.•CO2 desorption efficiency of Glc-Cs reached about 97–98%.We reported novel glucose-based carbon materials (Glc-Cs) with high surface area, high CO2 adsorption capacity and excellent CO2/CH4/N2 selectivity. Starch sugar (glucose) was used as carbon source to prepare Glc-Cs, and then the resultant samples were characterized by N2 adsorption at 77 K, FTIR, TGA and SEM. CO2/CH4/N2 adsorption isotherms of Glc-Cs were separately measured and the isosteric heats of CO2/CH4/N2 adsorption on the samples were estimated. IAST theory was applied to predict the selectivity of the samples toward binary gas mixtures. The regenerability of the resultant materials was evaluated by means of experiments of CO2 adsorption-desorption cycles. Results showed that BET surface area and pore volume of the resultant Glc-Cs reached as high as 3153 m2/g and 2.056 cm3/g, respectively. Glc-Cs possessed not only excellent stability, but also super-high CO2 adsorption capacity up to 22.4 mmol/g at 30 bar, comparable or superior to many stable metal-organic frameworks (MOFs). Besides, Glc-Cs possessed excellent adsorption selectivity toward CO2/N2 and CO2/CH4 binary mixtures. For example, for CO2/N2 binary mixture, its IAST-predicted selectivity at 30 bar reached as high as 20 toward CO2/N2 (0.5:0.5) mixture and 66 toward CO2/N2 (0.15:0.85) mixture separately. For CO2/CH4 binary mixture, its IAST-predicted selectivity at 30 bar reached as high as 4.5 for CO2/CH4 (0.5:0.5) mixture and 27 for CO2/CH4 (0.1:0.9) mixture separately. Experiment of multiple cycles of CO2 adsorption-desorption showed that the Glc-Cs has excellent regenerability. CO2 desorption efficiency reached about 97–98%. Glc-Cs is a promising adsorbent for the separation of CO2/N2 and CO2/CH4 mixtures.Download high-res image (73KB)Download full-size image

•MIL-100(Fe) with a BET surface area of 2558 m2 g−1 was prepared.•C2H4 and C3H6 uptakes of MIL-100(Fe) were 3.8 mmol g−1 and 7.5 mmol g−1 at 1 atm and room temperature.•C2H4/C2H6 selectivity of MIL-100(Fe) was 111 at 1 kPa and room temperature.•C3H6/C3H8 selectivity of MIL-100(Fe) was 70 at 1 kPa and room temperature.MIL-100(Fe) with a BET surface area of 2558 m2 g−1 was prepared for the separation of olefin–paraffin mixtures. The sample was characterized by X-ray diffraction (XRD), and scanning electron microscope (SEM). Isotherms of C2H4, C2H6, C3H6 and C3H8 were measured with a volumetric method, and the C2H4/C2H6 and C3H6/C3H8 adsorption selectivities of the sample were calculated based on the ideal adsorbed solution theory (IAST). The results showed that (a) MIL-100(Fe) adsorbent achieved a superior C2H4 adsorption capacity of 3.8 mmol g−1 and C3H6 7.5 mmol g−1 at 1 atm and 298 K. (b) The isotherms could be well described by the dual-site Langmuir–Freundlich models. (c) The C2H4/C2H6 and C3H6/C3H8 adsorption selectivity of MIL-100(Fe) at 1 kPa and 298 K were up to 111 and 70, respectively, which can be attributed to the selective π-complexation between olefins and Fe(II) of MIL-100(Fe).Download high-res image (260KB)Download full-size image

A composite of Cu-BTC and graphite oxide (GO) was prepared by rapid room-temperature synthesis method for thermally driven adsorption chillers (TDCs). A series of composites Cu-BTC@GO with varied GO loading were synthesized at room temperature within 1 min, and characterized by N2 adsorption test, scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared analysis. The adsorption isotherms of ethanol on the composites were measured at different temperatures, and then, the isosteric heats of ethanol adsorption were estimated. The composite working capacities and coefficient of performance (COP) of the composite–ethanol working pair were calculated for the application of refrigeration. Results showed that Cu-BTC@GO possessed a superhigh adsorption capacity for ethanol up to 13.60 mmol/g at 303 K, which was attributed to introduction of GO leading to increases in the surface dispersive forces and the mesoporous volume of Cu-BTC@GO. The isosteric heat of ethanol adsorption on Cu-BTC@GO was slightly higher than that of Cu-BTC. The adsorption capacity of Cu-BTC@GO was higher than many other metal–organic frameworks (MOFs) under the application conditions of TDCs. The composites exhibited 5.8–17.4% higher working capacity and energy efficiency than parent Cu-BTC for the application of refrigeration. The rapid room-temperature synthesis approach has potential for the preparation of new MOF-based composites.

A novel mechanochemical method was proposed to reconstruct quickly moisture-degraded HKUST-1. The degraded HKUST-1 can be restored within minutes. The reconstructed samples were characterized, and confirmed to have 95% surface area and 92% benzene capacity of the fresh HKUST-1. It is a simple and effective strategy for degraded MOF reconstruction.

Novel composite MIL-101(Cr)@PFs were successfully prepared by immobilizing MIL-101(Cr) crystals onto the 100% virgin pulp fibers (PFs), and then characterized by N2 adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and thermal analysis. The adsorption isotherms of CO2 and benzene vapor on MIL-101(Cr)@PFs were measured by a volumetric method. Mechanical stability of sheet MIL-101(Cr)@PFs were tested on an oscillator with adjustable oscillation frequency of 2 and 4 Hz. Results showed that the as-synthesized MIL-101(Cr)@PFs demonstrated similar gas uptake to the parent MIL-101(Cr) as well as excellent stability. The surface area of MIL-101(Cr)@PFs increased with the loaded amount of MIL-101(Cr). The uptakes of 67MIL-101(Cr)@PF for CO2 and benzene vapor reached 2.13 mmol g−1 and 10.29 mmol g−1 at 298 K, respectively, close to those of unit mass of MIL-101(Cr) loaded on the pulp fibers, suggesting high utilization efficiency of MIL-101(Cr) after casting on PFs. MIL-101(Cr)@PFs prepared in this work were flexible. 50MIL-101(Cr)@PFs can be distorted up to 360° without damage. Importantly, mass retention rate of MIL-101(Cr)@PFs maintained up to 99% after vibration of 120 minutes at 2 Hz or 4 Hz, implying that MIL-101(Cr) crystals had been anchored on pulp fibers stably. It could be expected that the sheet MIL-101(Cr)@PFs would become a promising adsorption material for gas adsorption and purification in practical applications.

It is well-known that water vapor is omnipresent. It would inevitably have a negative influence on VOC adsorption on novel porous materials in actual situations. In this work, the competitive adsorption behavior of water vapor with three VOCs, 1,2-dichloroethane (DCE), ethyl acetate (EA) and benzene, on MIL-101 in a humid atmosphere was investigated by isotherm measurement, breakthrough experiments and TPD experiments. The results showed that adsorption capacities of MIL-101 for DCE, EA and benzene were individually up to 9.71, 5.79 and 3.76 mmol g−1, much higher than those of other conventional adsorbents. Breakthrough experiments indicated that the presence of water vapor in the feed stream resulted in a sharp decrease in the VOCs working capacities of MIL-101 due to competitive adsorption of water vapor on MIL-101 surfaces. The breakthrough times and the working capacities of these VOCs became smaller with an increase in the relative humidity. TPD experiments indicated that the desorption activation energies of water vapor, DCE, EA and benzene on MIL-101 were 72.9, 47.14, 41.9, and 38.16 kJ mol−1, respectively. The stronger interaction of water vapor with MIL-101 formed strong competitive adsorption with VOCs on MIL-101, resulting in the sharp decrease of the VOCs working capacities in a humid atmosphere.

The objective of this work is to develop CuCl@AC adsorbent with high CO capacity and selectivity from CO/N2 binary gas mixture. A series of CuCl@AC adsorbents were prepared by a solid-state auto dispersion method, and then characterized by N2 adsorption test, XRD and XPS. CO and N2 adsorption isotherms on the adsorbents were measured by a volumetric method. The adsorption isotherms and selectivities of CuCl@AC adsorbents for CO/N2 binary mixture were estimated on the basis of ideal adsorbed solution theory (IAST). Results showed that (a) CO uptakes of CuCl@AC increased with CuCl loading in the loading range of 0–1.2 g/g. The maximal CO adsorption capacity of the CuCl@AC with CuCl loading of 1.2 g/g reached 38 cc/g at the P/P0 of 0.40, around 8 times of that over the original AC; (b) calcination time for the preparation of Cu(I)@AC had significantly impact on CO adsorption of the adsorbents due to valence change of Cu species on carbon surfaces. XPS analysis indicated that when the calcination time was optimized to be 1 h at 350 °C under argon, the prepared Cu(I)@AC had the highest percentage of Cu+ species on its surfaces, and consequently it had the highest CO capacity among the adsorbents since adsorptive species responsible for CO adsorption is Cu+; (c) The IAST-predicted CO/N2 adsorption selectivities of 1.2CuCl/AC decreased with pressure. Its CO/N2 selectivity was up to 100–450 at low pressure range of 0–10 kPa, and it remained in the range of 50–100 at higher pressure range of 20–100 kPa. The high adsorption capacity and selectivity of Cu(I)@AC adsorbents made it a promising adsorbent for CO/N2 mixture separation.

We firstly propose the application of CNTs as novel catalysts and molecular oxygen as the oxidant for the oxidative desulfurization (ODS) of a model fuel containing benzothiophene (BT), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) at atmospheric pressure and low temperature. Results showed that when three CNTs including CNT-SZ, CNT-TS, and CNT-CD were separately used as catalysts with molecular oxygen as the oxidant, the conversion of DBT to its corresponding sulfone reached 100% at 150 °C separately within 40, 120 and 180 min. The CNT-SZ exhibited a superior catalytic activity even at a high fuel-to-catalyst ratio of 7.5 kg fuel per g catalyst. The oxidation reactivity of these benzothiophenic compounds followed the order: 4,6-DMDBT > DBT > BT. The deactivated CNT can be effectively regenerated by heat treatment under an argon atmosphere at 900 °C. Raman spectroscopy analysis revealed that the graphitization degree of the CNT played a decisive role in its catalytic activity for DBT oxidation. The CNT with the higher degree of graphitization had higher catalytic activity for DBT oxidation since its higher electric conductivity benefited the transfer of electrons involved in the oxidation–reduction reaction.

A novel composite material GrO@MIL-101 was synthesized using a solvothermal synthesis method. Then the parent materials (MIL-101 and graphene oxide) and the GrO@MIL-101 were characterized using SEM, TEM, XRD, nitrogen sorption, and Raman. The acetone isotherms on the GrO@MIL-101 and MIL-101 were measured separately. The isosteric heat of adsorption and the desorption activation energies of acetone on the two samples were estimated. The results of characterization confirmed the formation of well-defined GrO@MIL-101 with higher surface area and pore volume compared to the MIL-101, and the crystal size of the MIL-101 in the composite was smaller than that of the parent MIL-101. The acetone isotherms on the GrO@MIL-101 were much higher than those on the MIL-101. The acetone adsorption capacity of the GrO@MIL-101 was up to 20.10 mmol g−1 at 288 K and 161.8 mbar, having an increase of 44.4% in comparison with the MIL-101. The desorption activation energy of acetone on the GrO@MIL-101 was higher than that on the MIL-101, indicating the stronger interaction between acetone molecules and the GrO@MIL-101. Consecutive cycles of acetone adsorption–desorption showed that the desorption efficiency of acetone on the GrO@MIL-101 can reach 91.3%. Acetone adsorption on this composite material was highly reversible.

Covalent anchoring of 2,2′-bipyridine (L) to a graphene (Gr) modified electrode followed by treatment with an Mx+(NO3)x solution (M = Fe3+, Co2+, Ni2+, or Cu2+) results in surface-bound catalysts with high redox activity in neutral water at ambient temperature. Raman and IR spectroscopies indicate the successful L grafting and Gr deposition onto the electrodes, whereas metal concentration was determined by inductively coupled plasma mass spectrometry (ICP-MS). Cyclic voltammetry measurements were used to investigate catalytic performances, whereas a rotating ring-disk electrode was used to measure the faraday efficiencies of oxygen evolution reaction and determine experimental turnover frequencies (TOFs). Of the four metal-L complexes investigated, Co-L on a Gr-modified indium tin oxide (ITO) electrode exhibits the best catalytic activity. Washing with a solution containing catalytically inert Zn2+ removes Co weakly bound by surface carboxylate functionalities, and ensures the presence of only covalently attached active catalytic species. This process results in an experimental TOF of 14 s–1 at an overpotential of 834 mV. Functionalization of Gr-modified electrodes with appropriate metal-binding moieties thus provides a feasible strategy for loading first row transition metals onto conductive surfaces for the generation of highly active water oxidation catalysts.Keywords: 1st row transition metal; electrochemistry; graphene; water oxidation catalyst

One-pot photocatalysis-assisted adsorptive desulfurization (ADS) of diesel using bi-functional doped-TiO2 adsorbents with molecular oxygen in air under ambient conditions was developed, which achieved a high ADS capacity of 1.89 mg-S per g-Ads. The developed approach provides a new path for ultra-clean fuel production.

In this work, we explored a two-step oxidative desulfurization (ODS) approach using in-situ-generated peroxides in diesel by light irradiation. The supported catalysts were prepared by incipient wetness impregnation and characterized by N2 adsorption test, X-ray diffraction, and X-ray photoelectron spectroscopy. Kinetic curves for peroxide generation by light irradiation and self-decomposition over a MoO3/SiO2 catalyst were measured. Catalytic activities of the catalysts for ODS were tested. Results showed that (a) the efficiency of peroxide generation in diesel under a mercury lamp was much higher than that under a xenon lamp at the same light intensity and can be enhanced at a higher temperature, (b) with in-situ-generated peroxides in diesel by light irradiation, the ODS conversion of catalysts followed the order of MoO3/SiO2 > V2O5/SiO2 > WO3/SiO2 and the conversion reached 75.6% using the MoO3/SiO2 catalyst at the reaction temperature of 45 °C at the O/S ratio of 8, and (c) accompanying the main ODS reaction with hydroperoxides over the MoO3/SiO2 catalyst in diesel, the competing side reaction of peroxide self-decomposition occurred and its kinetics increased dramatically with the reaction temperature. The overall ODS conversion may be affected by the diffusion of bulky refractory sulfur compounds in diesel on the catalyst, which can be enhanced by increasing the pore size of the MoO3/SiO2 catalyst. The two-step oxidative desulfurization approach provides a viable path to achieve clean diesel effectively under mild conditions without using costly hydrogen.

This work investigates the adsorption of organosulfur compounds in model fuels over metal–organic frameworks (MOFs) using a combined experimental/computational approach. Adsorption isotherms of three MOFs, MIL-101(Cr), MIL-100(Fe), and Cu-BTC, follow the Langmuir isotherm models, and Cu-BTC shows the highest adsorption capacity for both dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), ascribing to the highest density of adsorption sites and fairly strong adsorption sites on Cu-BTC. Experimental results show adsorption selectivity of various compounds in model fuels follows the order of quinoline (Qu) > indole (In) > DBT > 4,6-DMDBT > naphthalene (Nap), which is consistent with the order of calculated binding energies. Adsorption capacities of thiophenic compounds decrease significantly with the introduction of Qu, In, or water due to their strong competitive adsorptions over the coordinatively unsaturated Cu sites on Cu-BTC. The binding energies of Qu, In, H2O, and DBT are calculated as −56.04, −41.01, −50.27, and −27.52 kJ/mol, respectively. The experimental and computational results together suggest that the adsorption strength of thiophenic compounds over Cu-BTC is dominated by the interaction of both the conjugated π system (π-M) and the lone pair of electrons on sulfur atom (σ-M) of thiophenes, with the coordinatively unsaturated sites (CUS) on Cu-BTC. Alkyl groups on 4- and/or 6-positions of thiophenic compounds function as both eletron donor to increase π-M interaction and steric inhibitor to decrease σ-M interaction. MOFs with strong and highly dense CUS can be promising materials for ADS of fuels.

The performance of NiO, MnO2, CeO2, Fe2O3, and CuO catalysts on alumina in removing toluene from a gas stream was studied in a plasma catalysis system. The NiO catalyst performed better than the other catalysts, generating more toluene-destroying oxygen species by decomposing ozone. The optimum nickel loading in the NiO/γ-Al2O3 catalyst was approximately 5 wt%, close to the monolayer dispersion threshold of NiO on γ-Al2O3. The presence of water vapor had a negative effect on catalytic performance due to its quenching of high speed electrons and its competition with toluene for adsorption sites. Water vapor also reduced the outlet ozone concentration by inhibiting the production of key intermediate in the ozone formation process.

The adsorption capacity and selectivity of carbon dioxide and nitrogen at 298 K have been evaluated for two series of MMOFs built on metal paddle-wheel building units, including non-interpenetrated Zn(BDC)(TED)0.5 (1), Zn(BDC–OH)(TED)0.5 (2), Zn(BDC–NH2)(TED)0.5 (3), and interpenetrated Zn(BDC)(BPY)0.5 (4), Zn(BDC)(DMBPY)0.5 (5), Zn(NDC)(BPY)0.5 (6) and Zn(NDC)(DMBPY)0.5 (7) framework structures. The ideal adsorbed solution theory (IAST) has been employed to predict the adsorption selectivity of CO2–N2 binary mixtures on all seven MMOFs using single-component experimental adsorption isotherm data. The applicability of IAST to these systems is verified by GCMC simulations performed on both single- and multi-component gases.

This work is mainly involved with study of adsorption and electrothermal desorption of water vapor on the activated carbons (ACs) with different electric conductivities. The ACs were modified by using microwave irradiation in a nitrogen atmosphere, and then the surface oxygen content and the electric conductivity performances of the modified samples were respectively characterized using X-ray photoelectron spectrometer and electric heating experiments. The isotherms of the water vapor on the modified ACs were measured by means of batch adsorption experiments. The results show that the microwave-assisted modification make the surface oxygen contents of the ACs decrease so that the electric conductivities of the ACs are greatly improved, which would enhance the electric heating desorption efficiency of water from the modified ACs. The electrothermal desorption rate of water increases with an increase in the electric conductivities of the ACs and in the voltage exerted on the bed. The better electric conductivity performances of the ACs could make the water adsorbed on the ACs be desorbed more quickly. For example, for the AC900, it only took 100 s to desorb 80% of the amounts adsorbed of water on the AC900.Highlights► Microwave irradiation in nitrogen made the oxygen content of the ACs decreased. ► Electric conductivities of the ACs were greatly improved by microwave irradiation. ► Electrothermal desorption was firstly applied to desorption of water from the ACs. ► Electrothermal desorption rate of water on ACs increased with electric conductivity.

Adsorption equilibrium and diffusion of benzene on mesoporous chromium−terphthalate-based crystals (MIL-101) were experimentally studied by the gravimetric method in the pressure range up to 60.0 mbar. The MIL-101 crystals, whose sizes are about 100 nm, were synthesized by using microwave irradiation method. Adsorption isotherms and kinetic curves of benzene on the MIL-101 were measured experimentally. Results show that the maximum amount adsorbed of benzene on the synthesized MIL-101 was up to 16.5 mmol/g (or 176 wt %) at 288 K and 56.0 mbar. Diffusion coefficients of benzene within the MIL-101 were in the range of (4.25−4.76) × 10−9 cm2/s in 288−318 K with a lower activation energy of 2.41 kJ/mol. Temperature programmed desorption (TPD) curves exhibited two separated peaks corresponding to two types of major adsorption sites for benzene adsorption on MIL-101. Consecutive cycles of adsorption−desorption experiment showed a fast desorption kinetics and high reversibility for benzene adsorption on MIL-101. The efficiency of benzene desorption from MIL-101 can reach 97%.

In this work, isotherm and kinetics of CO2 adsorption on a chromium-based metal organic framework MIL-101 sample were studied. The MIL-101 crystal cubes were synthesized by the microwave irradiation method and then characterized. The isotherms and kinetic curves of CO2 adsorption on the MIL-101 sample were separately measured at 298, 308, 318, and 328 K within a pressure range of 0−30 bar by a gravimetric method. The mass-transfer constants and diffusion activation energy Ea of CO2 adsorption on the MIL-101 crystals were estimated separately. Results showed that the maximum uptake of CO2 on MIL-101 was 22.9 mmol/g at 298 K and 30 bar and that isotherms of CO2 adsorption were well-fitted with the Freundlich model. The isosteric adsorption heat of CO2 on MIL-101 was in the range of 4.0−28.6 kJ/mol. It depended upon the amount of CO2 uptake and decreased with the loading of CO2. The adsorption kinetics of CO2 on the MIL-101 crystals was described by the linear driving force (LDF) model. With the increase of the temperature, the mass-transfer constants of CO2 adsorption on MIL-101 increased. The diffusion coefficients of CO2 were in the range from 4.11 × 10−11 to 2.54 × 10−10 cm2/s. The coefficients increased with the temperature and decreased with the pressure. The diffusion activation energies Ea of CO2 on MIL-101 were in the range of 2.62−4.24 kJ/mol, which decreased with the pressure.

The adsorption equilibrium and diffusion of ethyl acetate (EA) on chromium-terphthalate-based crystals (MIL-101) are experimentally studied. The MIL-101 synthesized in this work shows an extra-high surface area of 5014 m2·g–1 (Langmuir). Adsorption isotherms and kinetic curves of EA on the MIL-101 are measured by a gravimetric method. Results show that the isotherms of EA can be fitted favorably by the Langmuir equation. The adsorption capacity of the MIL-101 for EA is up to 10.5 mmol·g–1 at 288 K and 54 mbar. Diffusion coefficients of EA within the MIL-101 are in the range of (1.617 to 2.264)·10–10 cm2·s–1 in (288 to 318) K with a lower activation energy of 8.361 kJ·mol–1. The isosteric heat of EA adsorption on the MIL-101 is within the range of (36.48 to 42.25) kJ·mol–1. The isosteric adsorption heat increased slightly with the amount adsorbed of EA, implying the existence of favorable lateral interactions between EA molecules. Multiple adsorption–desorption cycles are conducted at 298 K to examine the reversibility of EA adsorption on the MIL-101. Adsorptions were performed separately at (2, 3, 5, 7, and 10) mbar, and desorptions are performed at 0.05 mbar. Experimental results show that the EA adsorption on the MIL-101 is highly reversible and the desorption efficiency of EA is up to 98.4 %.

This work is mainly involved with study of the adsorption of dibenzothiophene (DBT) on Ag/Cu/Fe-supported activated carbons (ACs) prepared by ultrasound-assisted impregnation (UI). Ag/AC-UI, Cu/AC-UI, and Fe/AC-UI were separately prepared by using impregnation of different metal salt solutions under ultrasound irradiation (UIr) and characterized by X-ray photoelectron spectroscopy (XPS) and CO-chemisorption experiments. Isotherms of DBT on the modified ACs were separately measured, and the effects of different metal ions loaded on the ACs on the amount of adsorbed DBT on the modified ACs are discussed. Results indicated that (1) the DBT adsorption capacity of the ACs modified by using impregnation without UIr followed the order: Ag/AC > Cu/AC > AC > Fe/AC; (2) the modification methods have significant influence on the adsorption abilities of the modified ACs toward DBT. The application of UIr to prepare metal ion-impregnated ACs can make the metallic particles on the carbon surfaces become finer and disperse better in comparison with the use of impregnation only. As a consequence, the Ag/AC-UI and Cu/AC-UI prepared by using the UIr have higher adsorption capacities of DBT than the Ag/AC and Cu/AC prepared using impregnation.

Activated carbon (AC) was modified by oxidation with nitric acid and microwave-assisted reduction. The textural properties and surface oxygen content as well as the surface acidities of the ACs studied were determined by nitrogen adsorption, X-ray photoelectron spectrometry, and Boehm titration. The adsorption isotherms of the water vapor were measured, and temperature-programmed desorption experiments were conducted to estimate the desorption activation energy, Ed, of water on the ACs. The results indicated that the oxidation increased the value of Ed and the adsorption capacity of water on AC in low relative humidity (RH) but decreased the adsorption capacity of water in high RH. The reduction decreased the value of Ed and the adsorption capacity of water on AC over the whole RH range. The modification of AC first by the oxidation treatment of nitric acid and then by microwave-assisted reduction treatment not only increased the adsorption capacity of water in a high RH but also greatly decreased the value of Ed. The microwave-assisted reduction of virgin or oxidized AC with hydrogen should yield a lower Ed and higher adsorption capacity of water in high RH than the reduction of that with nitrogen.

The textural properties and the surface acidities of four commercial activated carbons (ACs) were determined separately by nitrogen adsorption and Boehm titration. The adsorption isotherms of water vapor on the ACs were measured by the gravimetric method and fitted by the simplified version of the Do−Do (DD) model. The results indicated that all isotherms of water vapor on the ACs can be well-fitted by the simplified version of the DD model. The value of parameter n in the model increases with the pore size of the AC and is very close to 5 when the average pore diameter is between (1.96 and 2.8) nm. The order of parameter N0 is in good agreement with that of the total surface group concentrations. The parameter CμS is almost equal to the amount adsorbed of water on the AC at a relative humidity of 100 % or to the value of its total pore volume. The parameter Kμ depends on the pore size and decreases with increasing pore size. The value of parameter b depends on the combined contribution of the pore size and total surface group concentration of the AC and increases with the total surface group concentration and pore size.

The mesoporous silica gels impregnated with different metal salts were prepared and studied. The pore structure and specific surface area of adsorbents were evaluated using nitrogen adsorption. Then, the sorption isotherms and dynamics of water vapor were carried out at 303 K and different relative humidity (RH). The temperature programmed desorption experiments were conducted to estimate the activation energy (Ed) of water desorption on the silica gels. The results showed that the sorption capacity for water decreased with the increase of the ionic radius (except the calcium ion) and that CaCl2 and LiCl were particularly suitable for use in modification of the mesoporous silica gel to improve their sorption rates and capacities for water vapor at the lower and medium RH (RH < 80%). The larger the average pore diameter and pore volume of the initial silica gels, higher the accrual rates of the water vapor sorption rate and capacity were after modification with hygroscopic salts. The activation energy of the water desorption on the mesoporous silica gel modified by CaCl2 were much higher than that on the silica gel modified by LiCl, because the polarizability of the Ca2+ was higher than that of Li+.

This work mainly involved the investigation of the adsorption of benzothiophene (BT) and dibenzothiophene (DBT) on transition-metal ion-impregnated activated carbons and ion-exchanged Y zeolites. Five kinds of transition-metal ions, Ag+, Ni2+, Zn2+, Cu2+, and Fe3+, were separately loaded on activated carbons (ACs) and the NaI/Y zeolites, respectively. Adsorption isotherms were measured with the static adsorption method. Textual properties of these adsorbents were measured by using ASAP 2010. Results indicated that (1) there was no adsorption of DBT on NaI/Y because the aperture size of NaI/Y was smaller than the molecular size of BT, (2) the equilibrium amount adsorbed of BT on AgI/Y was the highest within six ion-exchanged zeolites studied and that on NiII/Y, ZnII/Y, CuII/Y, and FeIII/Y became improved in comparison to NaI/Y, (3) the equilibrium amounts adsorbed of BT and DBT on the modified ACs followed the order: AgI/AC > NiII/AC > CuII/AC > ZnII/AC > AC > FeIII/AC, and (4) at low BT concentrations (Cs < 3mmol/L), the ion-exchanged Y zeolites had a higher adsorption capacity of BT compared to the modified ACs because of their larger surface area of micropores, while at higher BT concentrations (7 < Cs < 10 mmol/L), the modified ACs had a higher adsorption capacity of BT because of their much larger surface area.

In this work, the effect of the textural property of activated carbons on desorption activation energy and adsorption capacity for benzothiophene (BT) was investigated. BET surface areas and the textural parameters of three kinds of the activated carbons, namely SY-6, SY-13 and SY-19, were measured with an ASAP 2010 instrument. The desorption activation energies of BT on the activated carbons were determined by temperature-programmed desorption (TPD). Static adsorption experiments were carried out to determine the isotherms of BT on the activated carbons. The influence of the textural property of the activated carbons on desorption activation energy and the adsorption capacity for BT was discussed. Results showed that the BET surface areas of the activated carbons, SY-6, SY-13 and SY-19 were 1106, 1070 and 689 m2·g−1, respectively, and their average pore diameters were 1.96, 2.58 and 2.16 nm, respectively. The TPD results indicated that the desorption activation energy of BT on the activated carbons, SY-6, SY-19 and SY-13 were 58.84, 53.02 and 42.57 KJ/mol, respectively. The isotherms showed that the amount of BT adsorbed on the activated carbons followed the order of SY-6 > SY-19 > SY-13. The smaller the average pore diameter of the activated carbon, the stronger its adsorption for BT and the higher the activation energy required for BT desorption on its surface. The Freundlich adsorption isotherm model can be properly used to formulate the adsorption behavior of BT on the activated carbons.

This work mainly involves the study of desorption kinetics of phenol from polymeric resins under the influence of an ultrasound field. A new phase equilibrium-kinetics model (PEKM), for estimation of diffusion coefficient was proposed, kinetic experiments of phenol desorption on NKA-II resin in the presence and the absence of ultrasound were separately conducted, and diffusion coefficients of phenol within an adsorbent particle were estimated by means of proposed PEKM. Results showed that the use of ultrasound could enhance the diffusion of phenol within the resin. The diffusion coefficient of phenol in the resin in an ultrasonic field increased by an order of magnitude in comparison with the diffusion coefficient in the absence of ultrasound. The more intense the ultrasonic field the larger was the diffusion coefficient.

The copper based catalysts, CuO/γ-Al2O3, CuO/γ-Al2O3-cordierite (Cord) and CuO/Cord, were prepared by impregnation method. The catalytic activity of the catalysts was tested in absence and presence of water vapor, and the catalysts were characterized. Temperature program desorption (TPD) experiments of toluene and water on the catalysts were carried out. The influence of water vapor on the activity of the catalysts was discussed. Results showed that addition of the water vapor has a significant negative effect on the catalytic activity of the catalysts. The higher the concentration of the water vapor in feed steam was, the lower the catalytic activity of the copper based catalysts became, which could be mainly ascribed to the competition of water molecules with toluene molecules for adsorption on the catalyst surfaces. TPD experiments showed that the strength of the interaction between water molecules and three catalysts followed the order: CuO/γ-Al2O3CuO/γ-Al2O3-Cord>CuO/Cord. As a consequence of that, the degree of degradation in the catalytic activity of these three catalysts by the water vapor followed the order: CuO/γ-Al2O3CuO/γ-Al2O3-Cord>CuO/Cord. However, the negative effect of the water vapor was reversible.

•Concerned with the question why ODS catalyst is not effective for real gasoline.•Reported the strong inhibiting effect of gasoline composition on ODS for the 1st time.•ODS reactivity is suggested to be determined by partial charge on S atom of thiophene.•Proposed approaches to improve ODS selectivity for real gasoline desulfurization.This work is concerned with the question of why oxidative desulfurization (ODS) catalyst that show good catalytic performance for ODS of model gasoline thiophenic compounds is not effective for real gasoline. For the first time, the effects of gasoline composition on ODS using a phosphotungstic acid/activated carbon (HPW/AC) catalyst with H2O2 were investigated. ODS of thiophene, one of the most difficult thiophenic compounds to be oxidized, was studied in a model fuel system, where a high thiophene conversion rate of 90% could be reached in 2 h at 90 °C. However, when applying the ODS to a real gasoline, the ODS conversion rate decreased to only 32%, suggesting a strong inhibiting effect of gasoline composition on ODS. The ODS studies in different model fuels suggested that the inhibiting effect can be ascribed to the competitive adsorption and oxidation with the presence of the alkenes and alkylated aromatic hydrocarbons in real gasoline. The active pi-electrons in alkenes and alkyl groups in alkylated aromatic hydrocarbons may react with polyoxoperoxo species or peroxo-metallate complexes formed by phosphotungstic acid–H2O2 interaction. Additionally, it was indicated that the ODS selectivity followed the order of benzothiophene > trimethylthiophene > dimethylthiophene ∼ methylthiophene > thiophene, suggesting the partial charge on the electron-rich sulfur atom may play a decisive role for its oxidation reactivity. To mitigate the inhibiting effect of gasoline composition on ODS, we propose (a) implementation of selective separation–oxidation processes; (b) choice of suitable selective oxidants; (c) optimization of selective ODS reaction temperature, etc. to improve ODS selectivity for real gasoline desulfurization applications.

•A series of asphalt–based activated carbons (A-ACs) are successfully synthesized.•A-ACs exhibit ultra-high BET area of 3111 m2/g and pore volume of 1.92 cm3/g.•A-ACs are ethane-selective adsorbents with super high ethane uptake of 7.2 mmol/g at 25 °C and 100 kPa.•Ethane/ethylene adsorption selectivity of A-ACs is up to 16.3 for the cracked gas mixture.We reported novel asphalt–based activated carbons (A-ACs) with high C2H6/C2H4 adsorption capacity and selectivity. A series of A-ACs were prepared by a one-step preparation method and characterized. The adsorption performances of A-ACs for ethane/ethylene were examined. Results showed that the sample A-ACs prepared at 800 °C and the KOH/asphalt ratio = 4 exhibited ultra-high BET area of 3111 m2/g and its pore volume reached 1.92 cm3/g. Their surface O and N contents gradually decreased with activation temperature or KOH/asphalt ratio at which A-ACs were prepared. More interestingly, A-ACs showed significantly preferential adsorption of C2H6 over C2H4. It could be ascribed to the stronger interaction of C2H6 with the surfaces of A-ACs by hydrogen bonds compared to C2H4, which were revealed by Density functional theory calculation. Its C2H6 adsorption capacity was up to 7.2 mmol/g at 100 kPa and 25 °C and its C2H6/C2H4 adsorption selectivity for typical cracked gas mixture (15:1 ethylene/ethane) was in the range of 3.2–16.3 at the pressure below 100 kPa, higher than the most reported ethane-adsorbents. Additionally, the isosteric heat of ethane and ethylene adsorption on A-ACs were lower than those on π-complexation adsorbents. Therefore, these excellent adsorption properties would make A-ACs as a type of promising adsorbents for adsorption separation of C2H6/C2H4.Download high-res image (200KB)Download full-size image

The imidazolate framework ZIF-8 samples were modified separately by using ammonia impregnation and thermal treatment in atmosphere of N2 or H2 in order to improve its adsorption property toward CO2, and the modified samples A-ZIF-8, N-ZIF-8 and H-ZIF-8 were correspondingly available. The modified ZIF-8 samples were characterized, and the surface chemical properties of the ZIF-8 samples were determined separately by FTIR, CO2-TPD, NH3-TPD and H2O-TPD. The isotherms of CO2 on the modified ZIF-8 samples were measured. Results showed that after surface modification, the total amounts of basicity of the modified samples significantly increased, and followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The uptakes of CO2 increased proportionally with the basic groups on the surfaces of the ZIF-8 samples due to CO2 being an acidic molecule. As a consequence of that, the CO2 adsorption capacity of the samples followed the order: A-ZIF-8>H-ZIF-8>N-ZIF-8>O-ZIF-8. The amount adsorbed of CO2 on the modified ZIF-8 sample by ammonia impregnation is the highest, having an increase.Highlights► ZIF-8 was modified by ammonia impregnation and thermal treatment in gaseous N2 or H2. ► Ammonia impregnation has the CO2 uptake of modified ZIF-8 increase by 45%. ► The CO2/N2 selectivity of modified ZIF-8 has a maximum increase of 56%. ► The hydrophobility of modified ZIF-8 was improved due to increase of surface basicity.

•Compositing GrO and MIL-53(Cr) yields a series of novel GrO@MIL-53(Cr) composites.•GrO@MIL-53(Cr) exhibits high CO2 uptake and superior CO2/CH4 selectivity.•10% GrO doping results in a 16 times higher CO2/CH4 selectivity at 5 bar.•10GrO@MIL-53(Cr)’s CO2 uptake is improved by 62% at 5 bar compared to MIL-53(Cr).•The enhanced performance is attributed to a quenched breathing effect proved by XRD.Compositing graphene oxide (GrO) as a robust support into MIL-53(Cr) can provide a feasible strategy to stabilize its flexible structure from CO2-triggered shrinkage, resulting in an enhanced CO2 uptake together with a higher CO2/CH4 adsorptive selectivity of the GrO@MIL-53(Cr) composites for biomethane upgrade. In this work, a series of novel GrO@MIL-53(Cr) composites were prepared from GrO and MIL-53(Cr). Their adsorptive performance for CO2/CH4 separation was experimentally investigated. IAST was applied to predict their adsorptive selectivity for CO2/CH4 separation. Results show that a small amount of GrO doping (1%) could significantly improve surface area and pore volume of the resulting 1GrO@MIL-53(Cr), while a remarkably enhanced CO2 uptake was observed with sufficient GrO doping (10%) for 10GrO@MIL-53(Cr) at 5 bar and room temperature, which is 62% higher than that of its parental MIL-53(Cr). XRD indicates a quenched “breathing effect” could be responsible for the remarkably enhanced CO2 uptake. With this quenched breathing effect, 10GrO@MIL-53(Cr) shows a 16 times higher CO2/CH4 selectivity at 5 bar for the equimolar CO2/CH4 mixture. SEM and TEM show well-defined compositing structures, while IR, Raman and TG suggest GrO@MIL-53(Cr) composites manage to preserve most of the crystallographic and chemical characteristics of their parent MIL-53(Cr).Download high-res image (138KB)Download full-size image

The activated carbons (ACs) with high surface area were modified separately by using ammonia aqueous solution impregnation and microwave irradiation in an atmosphere of N2 or H2 in order to improve their adsorption properties toward CO2. The modified ACs were characterized, and the surface chemical properties of the ACs were determined separately by FTIR, Boehm titration and X-ray photoelectron spectroscopy (XPS) methods. The isotherms of CO2 on the modified ACs were measured. Results showed that after surface modification, the contents of elements C and N of the samples increased, while that of the element O of the samples decreased in comparison with the original AC. Correspondingly, the amounts of the surface basic groups of the modified ACs increased, while those of the surface acidic groups decreased as compared to the original AC. The use of microwave irradiation in an atmosphere of N2 to modify the carbon can make the total basic groups of the surfaces of the ACs be the highest among the modified ACs. As a consequence of that, the modified AC samples had higher adsorption capacities of CO2 than the original AC, and the more the surface basic groups of the ACs, the higher the adsorption capacity of the ACs for CO2. The amount adsorbed of CO2 on the modified AC by the microwave irradiation in the atmosphere of N2 was up to 3.75 mmol/g at 1 atm and 293 K, having an increase of 28% in comparison with the original AC.

A novel composite material GrO@MIL-101 was synthesized using a solvothermal synthesis method. Then the parent materials (MIL-101 and graphene oxide) and the GrO@MIL-101 were characterized using SEM, TEM, XRD, nitrogen sorption, and Raman. The acetone isotherms on the GrO@MIL-101 and MIL-101 were measured separately. The isosteric heat of adsorption and the desorption activation energies of acetone on the two samples were estimated. The results of characterization confirmed the formation of well-defined GrO@MIL-101 with higher surface area and pore volume compared to the MIL-101, and the crystal size of the MIL-101 in the composite was smaller than that of the parent MIL-101. The acetone isotherms on the GrO@MIL-101 were much higher than those on the MIL-101. The acetone adsorption capacity of the GrO@MIL-101 was up to 20.10 mmol g−1 at 288 K and 161.8 mbar, having an increase of 44.4% in comparison with the MIL-101. The desorption activation energy of acetone on the GrO@MIL-101 was higher than that on the MIL-101, indicating the stronger interaction between acetone molecules and the GrO@MIL-101. Consecutive cycles of acetone adsorption–desorption showed that the desorption efficiency of acetone on the GrO@MIL-101 can reach 91.3%. Acetone adsorption on this composite material was highly reversible.

The adsorption capacity and selectivity of carbon dioxide and nitrogen at 298 K have been evaluated for two series of MMOFs built on metal paddle-wheel building units, including non-interpenetrated Zn(BDC)(TED)0.5 (1), Zn(BDC–OH)(TED)0.5 (2), Zn(BDC–NH2)(TED)0.5 (3), and interpenetrated Zn(BDC)(BPY)0.5 (4), Zn(BDC)(DMBPY)0.5 (5), Zn(NDC)(BPY)0.5 (6) and Zn(NDC)(DMBPY)0.5 (7) framework structures. The ideal adsorbed solution theory (IAST) has been employed to predict the adsorption selectivity of CO2–N2 binary mixtures on all seven MMOFs using single-component experimental adsorption isotherm data. The applicability of IAST to these systems is verified by GCMC simulations performed on both single- and multi-component gases.

A novel mechanochemical method was proposed to reconstruct quickly moisture-degraded HKUST-1. The degraded HKUST-1 can be restored within minutes. The reconstructed samples were characterized, and confirmed to have 95% surface area and 92% benzene capacity of the fresh HKUST-1. It is a simple and effective strategy for degraded MOF reconstruction.