Al2O3 materials with different crystal forms were synthesized via the hydrothermal synthesis method using the low-cost raw material, and then the corresponding NiMo/Al2O3 catalysts were prepared by using Al2O3 materials with different crystal forms as the supports. The restrictive diffusion effects on the hydrodesulfurization reaction of different reactants with different molecular sizes over the NiMo/Al2O3 catalysts with different crystal forms were investigated systematically for the first time. NiMo/δ-Al2O3 exhibited the highest values of the effective factor (η) and effective diffusion coefficient (De), which could be ascribed to its proper pore diameter and relatively concentrated pore diameter distribution. The hindered magnitudes of diffusion decrease in the order of NiMo/δ-30 (2.23) < NiMo/θ-30 (2.83) < NiMo/γ-30 (3.42), indicating that the restrictive diffusion effect of NiMo/δ-30 catalyst was weaker than those of the other two catalysts.

A series of CoMo/Al2O3 catalysts was prepared using different crystal forms of alumina (including γ-Al2O3, δ-Al2O3, θ-Al2O3, and α-Al2O3) as supports for the hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of fluid catalytic cracking diesel. The physicochemical properties of the supports and the corresponding catalyst were analyzed by various characterization methods. The results showed that δ-Al2O3 possessed a moderate surface area, a concentrated pore size distribution, and less surface hydroxyl groups. The CoMo/δ-Al2O3 catalyst exhibited the highest HDS and HDN efficiencies, 98.4 and 96.1%, respectively. This could be attributed to its reduced metal–support interaction, moderate stacking morphology, and highest sulfidation degree of active phases. The HDS and HDN efficiencies of the catalysts followed the order of CoMo/α-Al2O3 (87.3 and 72.2%) < CoMo/γ-Al2O3 (94.8 and 87.9%) < CoMo/θ-Al2O3 (96.2 and 90.1%) < CoMo/δ-Al2O3 (98.4 and 96.1%).

The micro-mesoporous materials ZF-x (ZSM-5-FDU-12, x = SiO2/Al2O3) with different molar ratios of SiO2/Al2O3 were synthesized by an in situ nano-assembly method with the ZSM-5 precursor serving as the silica source. The physicochemical properties of the supports and the corresponding catalysts were analyzed in detail by various techniques including SEM, TEM, XRD, nitrogen physisorption, FTIR, UV-Vis, pyridine IR, Raman and XPS. The nitrogen physisorption measurement showed that the composite ZF-130 possessed excellent physical properties compared to other ZF-x materials. In addition, the XPS spectra displayed that catalysts NiMo/ZF-x showed a higher sulfurization than NiMo/FDU-12, and the NiMo/ZF-130 exhibited the highest contents of MoS2 and NiMoS. In addition, DBT was employed as the probe molecule to evaluate the HDS (hydrodesulfurization) performance of the sulfide catalysts of NiMo/ZF-x under different weight hourly space velocities (WHSVs) 20–120 h−1, while NiMo/FDU-12 was used as the reference. Furthermore, the relationship between the structure of micro-mesoporous materials and the HDS activities of catalysts was systematically evaluated. The HDS efficiencies followed the order NiMo/ZF-130 > NiMo/ZF-110 > NiMo/ZF-150 > NiMo/ZF-90 > NiMo/ZF-70 > NiMo/FDU-12 under the operation conditions of 340 °C, 4.0 MPa, and H2/oil of 200 20–120 h−1. Compared to other NiMo/ZF-x catalysts, NiMo/ZF-130 displayed the highest efficiency of DBT HDS, 96.3% at 20 h−1, which could be attributed to the synergistic effects of its larger pore sizes (14.9 nm), greater specific surface area (352 m2 g−1), moderate B and L acid sites, and the highest ratios of Mo4+/Mo (58%) and NiMoS/NiT (64%).

•A series of mesoporous γ-Al2O3 was synthesized at different aging temperatures.•NiMo/γ-363 exhibited superior DBT and 4,6-DMDBT HDS activity.•The vital role of aging temperatures in DBT and 4,6-DMDBT HDS was discussed.•The HYD route was the preferential pathway in 4,6-DMDBT HDS over NiMo/γ-363.•A possible reaction network for the HDS of 4,6-DMDBT was proposed over NiMo/γ-363.A series of γ-Al2O3 materials with different textural properties and acidities were synthesized from the boehmite sol by tuning the aging temperatures. NiMo supported catalysts were prepared by using γ-Al2O3 as the supports, then the catalytic HDS performance were evaluated by using DBT and 4,6-DMDBT to be the probe molecules. The physico-chemical properties of γ-Al2O3 supports and the corresponding NiMo catalysts were characterized by XRD, N2-physisorption, Py-IR, UV–Vis DRS, laser Raman spectra, H2-TPR, XPS, HRTEM methods. The characterization results showed that NiMo/γ-363 catalyst possessed a large pore size (12.0 nm), open pore volume (0.86 cm3 g− 1), moderate acidity and appropriate MSI. The NiMo/γ-363 catalyst presented the highest DBT and 4,6-DMDBT conversions at all the WHSVs. The NiMo/γ-363 catalyst showed highest kHDS and TOF values of the 4,6-DMDBT HDS, which could be ascribed to the synergistic effect of excellent textural properties, appropriate acidity and suitable MSI of the NiMo/γ-363 catalyst, moderate dispersion degree, high sulfidation degree and desirable stacking morphology of the MoS2 crystallites. The highest HYD/DDS ratio (1.51) of the 4,6-DMDBT HDS over the NiMo/γ-363 catalyst indicated that the HYD pathway was the main reaction route. Furthermore, a possible reaction network for 4,6-DMDBT HDS over the series of NiMo/γ-Al2O3 catalysts was proposed.Download high-res image (350KB)Download full-size image

•FDU-12 with different morphologies were synthesized.•The effect of morphology on HDS activity was discussed systematically.•Morphology was important for the diffusion of DBT molecules.•NiMo/FDU-12 with hexagonal prism morphology exhibited the best activity on DBT HDS.Mesoporous silica FDU-12 with remarkable morphologies such as hexagonal prisms, spiral rodlike and brick-like, were successfully synthesized under low temperature and strong acidic conditions by introducing of different inorganic salts. The products were characterized by Small-angle X-ray scattering (SAXS) patterns, UV–vis diffuse reflectance Spectroscopy, N2 adsorption-desorption, scanning electron microscopy (SEM), laser Raman spectra (Raman), Fourier transform infrared spectroscopy with pyridine adsorption (pyridine-FTIR), X-ray photoelectron spectrometer (XPS), and transmission electron microscopy (TEM). The results showed that all the samples had high degrees of crystallinity, regular shape, large pore size and specific surface area, while the addition of different inorganic salts had a great influence on the morphology of FDU-12. Furthermore, the DBT HDS performances of FDU-12 supported NiMo hydrodesulfurization (HDS) catalysts were also investigated. The hexagonal prism NiMo/F-HP catalyst had a higher sulfurization degree and more acid sites than other catalysts. The catalytic results indicated that the morphologies and acidities of FDU-12 materials played an essential role in the catalytic performance of DBT HDS over NiMo catalysts. Among the catalysts with different morphologies, the DBT HDS conversions followed the order: hexagonal prism catalyst (NiMo/F-HP) > spiral catalyst (NiMo/F-SP) > brick-like catalyst (NiMo/F-BL). The highest activity of NiMo/F-HP could be ascribed to the relatively higher acidity, higher sulfurization degree and the better dispersion of the active phases.Download high-res image (121KB)Download full-size image

Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.

The control of the photocatalytic activity of TiO2 by tailoring their crystalline structure and electronic structure is a current topic of great interest. In the present study, the phase composition and exposed facets on Ti3+ self-doped TiO2 were regulated by simply changing the fluorinion concentration during the hydrothermal synthesis process of TiO2. It was found that the phase composition can be tuned facilely, and the phase transformation process was analyzed by XRD and UV Raman spectroscopy. The introducing fluorinion during the hydrothermal preparation of TiO2 resulted in F-doping and phase transformation. And the F-doping also affects the amount of Ti3+ ions in the TiO2. SEM analysis indicated that the morphology and exposed facets changed with the change in fluorinion concentration, and the ratios of exposed facets are adjustable. Through systematically optimizing these parameters, the TiO2 prepared under fluorinion concentration of 17.5 mM showed the excellent photocatalytic performance under full spectrum illumination. The good photocatalytic performance was mainly attributed to the more phase junctions and surface heterojunctions for enhancing charge separation.

A series of CoMo/δ-Al2O3 catalysts promoted by different organic and inorganic cobalt salts were successfully prepared using low-cost δ-Al2O3 as a support through a two-step incipient-wetness impregnation method. The obtained catalysts were indicated as MoCo-N/δ, MoCo-S/δ, MoCo-A/δ and MoCo-D/δ, in which N, S, A, D, and δ represent cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt diacetylmethane, and δ-Al2O3, respectively. The as-synthesized catalysts were introduced to the hydrodesulfurization (HDS) process of fluid catalytic cracking (FCC) diesel, in a fixed-bed reactor. The oxidized catalysts and the corresponding sulfurized catalysts for HDS were characterized by UV-vis, Raman, X-ray diffraction, TPR, and XPS techniques. The catalytic activities followed the order of MoCo-A/δ < MoCo-N/δ < MoCo-D/δ < MoCo-S/δ. These catalytic results could be ascribed to the introduction of different cobalt salts decreasing the metal-support interaction (MSI), and led to the formation of easily reduced Mo species, which were the precursors to form more active sites that could enhance the HDS activity of the catalysts. The highest activity shown by the MoCo-S/δ catalyst could be ascribed to its (1) higher metal dispersion, (2) lower Mo reduction temperature, and (3) higher sulfurization degree. As a result, the excellent catalytic performance could be attributed to its outstanding promoter effect.

A CdS encapsulated carbon nanotube (CNT) photocatalyst was prepared by a liquid-chemistry method. Through filling of CNTs with CdS, the aggregation of CdS was prevented efficiently by the good confinement effect of CNTs, and the photocatalytic performance of CdS was enhanced by 2.5 times via synergistic integration of the confinement effect of CNTs and heterojunction between CNTs and CdS. The photostability of CdS encapsulated in and attached on CNTs was investigated systematically through methylene blue photocatalytic degradation, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. The results indicate that the photocorrosion of CdS is successfully suppressed when it is encapsulated in the CNTs. The mechanism analysis suggests that spatial synergy of the CdS and powerful adsorptivity of CNTs are the primary causes for photocorrosion inhibition. Our efforts propose a new scheme to remarkably promote both the photostability and photocatalytic activity of photocorrosion-susceptible photocatalysts.

A photonic crystal-based CdS–Au–WO3 heterostructure was constructed on WO3 photonic crystal segments. Highly efficient visible-light-driven hydrogen and oxygen evolution are demonstrated relative to those of single-, two-component and unstructured systems due to good light harvesting of photonic crystals and efficient electron transfer of this heterostructure.

Venezuela Orinoco heavy crude oil was sequentially separated into several subfractions to determine the contents and types of vanadyl porphyrins contained in the products. Vanadium contents in each subfraction were detected using an atomic absorption spectrometer (AAS) combined with the characterization of vanadyl porphyrins by ultraviolet–visible (UV–vis) spectroscopy and positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Six types of petroleum vanadyl porphyrins, which have been identified previously, were well-characterized with the detailed fractionation. Three new series of vanadyl porphyrins corresponding to molecules of CnHmN4VO2, CnHmN4VO3, and CnHmN4VO4, respectively, were identified in addition to the six known types of vanadyl porphyrins.

•TiO2/CdS was structured into hollow sphere with Pt loaded onto the internal wall.•Vectorial electron transfer and spatially separated reaction surfaces were achieved.•The as-prepared catalyst exhibits good photocatalytic hydrogen evolution activity.•The underlying mechanism for the photocatalytic hydrogen evolution was proposed.Solar driven semiconductor photocatalytic water splitting to produce hydrogen is an extremely charming process by storing photon energy in chemical bonds. In the present study, composite semiconductor TiO2/CdS was structured into uniform and porous double-shelled hollow sphere with cocatalyst platinum selectively loaded onto the internal wall. The SEM, TEM, STEM, XRD, BET and EDS elemental distribution etc. were employed to evidence the formation of the targeted photocatalyst. It was demonstrated that the material has a high efficiency of visible-light-driven hydrogen evolution (296 μmol·h−1/10 mg) with an apparent quantum efficiency (QE) of 14.5% at wavelength of 420 nm. Comparative experiment analysis and time-resolved infrared absorption study suggested that the high photocatalytic activity of the catalyst is attributed to the vectorial electron transfer (CdS → TiO2 → Pt) and the spatial separation of reduction and oxidation active surfaces achieved by the special morphology.Porous hollow sphere of h-(Pt–TiO2)/CdS, with outer shell of CdS as an antenna for visible light, and internal shell of TiO2 with Pt nanoparticles as H2 evolution active layer, exhibits a high efficiency of visible-light-driven photocatalytic H2 production. The excellent catalytic performances are attributed to the synergetic effects of the ideal electron transfer and the spatial separation of reduction and oxidation active surfaces.

Using heptane, toluene, and tetrahydrofuran (THF) as eluant, asphaltenes were fractionated into five fractions based on their polarity and solubility. The molecular composition of polar heteroatom species in both asphaltene and its fractions were analyzed by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The application of UV-vis spectrometer in characterizing asphaltene composition and measuring asphaltene concentration was discussed. About 11.9 wt% asphaltene components adsorbed permanently on silica gel in the extrography column after excessive elution with various solvents. In negative FT-ICR MS, the mass spectra show that acidic and neutral nitrogen-containing compounds such as N1 and N1S1 mainly existe in the first three less polar fractions, while oxygen-containing compounds such as O2, O2S, O2S2, O3, and O4 show high relative abundance in more polar fractions. These results suggest oxygen-containing compounds have stronger adsorption ability with silica gel. It was observed that the double bond equivalence (DBE) distribution of N1 class species in the fractions shifted to higher values while the carbon number shifted to smaller numbers as polarity of fractions increased. This indicates that acidic and neutral N1 compounds with longer carbon chain and less aromaticity have less polarity compared with those with shorter carbon chain and stronger aromaticity. UV-vis absorbance indicats that fractions containing the most aromatic and most polar asphaltene have better absorbance at long wavelength, while the fractions that consist of least aromatic and least polar asphatlenes show high absorbance at short wavelength.

Engineering metal–organic frameworks (MOF) for heterogeneous catalysts have been of extreme interest since they could bridge the gap between homogeneous and heterogeneous catalysis. We have designed and synthesized gold functionalized IRMOF-3 catalysts by post-covalent modification (PM) and one-pot (OP) synthesis methods. The gold functionalized IRMOF-3 catalysts provide an efficient, economic, and novel route for the one-pot synthesis of structurally divergent propargylamines via three component coupling of alkyne, amine, and aldehyde (A3) without any additives or an inert atmosphere. The catalysts were characterized in depth to understand their structure–property relationship. It was shown that the 4.6%Au/IRMOF-3 catalyst, prepared by the PM method, contains a fraction of cationic gold (Au3+/Au0 = 0.2), which shows much higher catalytic activity than that of 3.2% or 0.6%Au/IRMOF-3 prepared by OP method, although the former exhibits much lower crystallinity than the latter two catalysts. Notably, the catalytic activity of the Au/IRMOF-3 catalysts could be significantly enhanced at a moderate reaction temperature (150 °C). All the Au/IRMOF-3 catalysts can be easily recycled and used repetitively at least 5 times, especially the catalysts prepared by the OP method, which showed no drop in activity for the successive 5 uses. These features render the catalysts particularly attractive in the practice of propargylamines synthesis in an environmentally friendly manner.

Acid hydrolysis and hydrogenation/hydrogenolysis reactions can be combined for catalytic conversion of cellulose into renewable biorefinery feedstocks by using two heterogeneous catalysts: sulfonic acid (–SO3H) functionalized mesoporous silica (MCM-41) and Ru/C. The combination is suitable for a one-pot tandem process to convert cellulose into alkanediols (mainly propylene glycol and ethylene glycol), yet deactivation of the sulfonic acid (–SO3H) functionalized mesoporous silica occurred rapidly after only one reaction cycle because of an irreversible change in the mesoporous structure and loss of acid groups. However, much better selectivity of hexitol or γ-valerolactone (GVL) can be obtained in a sequential tandem process by hydrogenating the hydrolysis products, glucose and levulinic acid (LA). A similar irreversible deactivation of acid catalyst also occurred when it involved the hydrogenolysis of glucose into alkanediols. When the sulfonic acid-functionalized mesoporous silica is filtered, and the hydrolysis products of cellulose are directly used in the hydrogenation reaction without further purification, a better selectivity and stability of hexitol production can be obtained. Under such conditions, the lifetime of the catalyst system can be significantly extended, up to 6 times the original durability of the acid-functionalized silica.

A novel technique was developed for characterization of saturated hydrocarbons. Linear alkanes were selectively oxidized to ketones by ruthenium ion catalyzed oxidation (RICO). Branched and cyclic alkanes were oxidized to alcohols and ketones. The ketones were then reduced to alcohols by lithium aluminum hydride (LiAlH4). The monohydric alcohols (O1) in the products obtained from the RICO and RICO-LiAlH4 reduction reactions were characterized using negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) for identification of iso-paraffins, acyclic paraffins and cyclic paraffins. Various model saturated compounds were used to determine the RICO reaction and ionization selectivity. The results from the FTICR MS analysis on the petroleum distillates derived saturated fraction were in agreement with those from field ionization gas chromatography time-of-flight mass spectrometry (FI GC-TOF MS) analysis. The technique was also used to characterize a petroleum vacuum residue (VR) derived saturates. The results showed that the saturated molecules in the VR contained up to 11 cyclic rings, and the maximum carbon number was up to 92.

A middle-temperature coal tar (MTCT) was distilled into multiple narrow boiling point fractions. The MTCT and its distillate fractions were subjected to bulk property analysis and molecular compositional characterization by gas chromatography–mass spectrometry. Acid/basic liquid extraction was performed to separate the MTCT into acidic, basic, and neutral fractions, which were characterized by positive-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The dominant compounds in MTCT were aromatics, phenols, and normal alkanes. The number of carbon atoms in the substituent chains varied over a relatively broad range for each homology. The composition of narrow distillate fractions varied: light naphtha (<100 °C) had a high benzene content, which is an unsuitable gasoline blending stock; middle distillates (160–240 °C) enriched with phenols, which is a good extraction feedstock for chemical products; and heavy distillates (>240 °C) are a hydrotreating feedstock for clean fuel production. The MTCT had large amounts of acidic and basic components, consisting of oxygen- and nitrogen-containing molecules. The basic fraction accounted for 2.68 wt % MTCT. Only nitrogen compounds in the MTCT could be detected by positive-ion ESI. Most of the oxygen-containing molecules exhibited a weak acidity and were partially extracted into the acidic fraction. Basic nitrogen compounds co-existed in the acidic, basic, and neutral fractions of MTCT. However, the molecular compositions of basic nitrogen compounds were different among these fractions: molecules with low carbon numbers and high aromaticities were found in the acidic and basic fractions, whereas mono-nitrogen basic compounds were abundant in the neutral fraction.

A commercial lignite gasification-derived middle-temperature coal tar (MTCT) was subjected to acid–base extraction to obtain acidic, basic, and neutral fractions. The neutral fraction was characterized by mass spectrometry (MS) for hydrocarbon-group-type analysis and further fractionated by extrography into six subfractions, which were characterized by gas chromatography–mass spectrometry (GC–MS). Saturate, aromatic, and resin fractions of the neutral fraction accounted for 16.4, 47.6, and 36.0 wt %, respectively. The GC–MS analysis showed that the first neutral subfraction (15.7 wt %) contained alkanes, alkenes, and cycloalkanes; the second subfraction (52.0 wt %) contained 1–6-ring aromatics; the third subfraction (4.6 wt %) contained neutral nitrogen compounds, such as indoles, carbazoles, and benzocarbazoles; the fourth subfraction (8.2 wt %) contained neutral polar compounds, such as C8–C28 alkyl nitriles and aliphatic and aromatic ketones, such as 4-, 5-, and 6-ketones and phenyl ketones, derived from a series of propiophenone to decanophenone; the fifth subfraction (14.9 wt %) contained 2-ketones and aromatic ketones, such as acetophenones, indanones, and acetonaphthones; and most of the sixth subfraction (1.3 wt %) cannot be eluted from GC. Electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to analyze the third neutral subfraction, which was enriched with neutral nitrogen compounds. In addition to indoles, carbazoles, and benzocarbazoles, FT-ICR MS analysis showed that dibenzocarbazoles and tribenzocarbazoles with various carbon numbers were present in the third neutral subfraction.

Reliable and efficient product yield estimation for unknown oils after the fluid catalytic cracking (FCC) reaction is one of the key components in heavy oil intelligent processing. This paper describes the use of two chemometric pattern recognition methods, k-nearest neighbor (k-NN) classification and supervised self-organizing maps (SSOMs), for building classification models to determine the most similar oil sample to an unknown sample in a given data set and to use the FCC yields record of the correspondent oil as the product yield prediction for the unknown sample under the same reaction conditions. Two-sided t test, correlation analysis, and hierarchical cluster heat map analysis were performed to assess the quality of the models. The work provides laboratory evidence that k-NN or SSOMs techniques could all be employed for FCC product yield estimation, while the k-NN model would be more suitable for industrial application in terms of stability and efficiency.

The adsorption of ammonia at Brönsted and Lewis acid sites on three low-index (001), (010) and (100) surfaces of V2O5 catalyst was investigated using density functional theory (DFT) method. Three levels of surface relaxation periodic models including top single layer relaxation (S-model), moderately deeper relaxation (M-model) and full relaxation model (F-model) were applied to examine the effect of the surface relaxation on the binding structures and adsorption energies. The results of calculations showed that on the saturated basal plane V2O5 (001), ammonia adsorption at the Brönsted acid sites (VOH) is energetically more favorable. On unsaturated (010) and (100) surfaces, ammonia is adsorbed strongly on both Brönsted (VOH) and Lewis acid sites (V). Surface relaxations have no influence on ammonia adsorption on saturated (001) surface, while a strong dependence on the relaxation models is observed for NH3-adsorption energies on (010) and (100) surfaces, especially at the Lewis acid sites of both side planes. When complete relaxation considered (F-model), ammonia adsorption on the Lewis acid sites (V) dominates for side planes (010) and (100). In the presence of VOH as neighbor, the ammonia adsorption at V sites is however weakened significantly due to steric hindrance. Hydrogen bonds may play a role, although not determining one, in the respect of the adsorption of ammonia on (010) and (100) surfaces. Moderate relaxation and full relaxation are absolutely necessary for the description of both H and NH3 adsorption on unsaturated (100) and (010) surfaces, respectively.We have theoretically investigated ammonia adsorption on the V2O5 surfaces in the view of geometry structure and adsorption energy and showed differences in NH3 adsorption ability (i) between different surfaces like (001), (010) and (100) and (ii) between different Brönsted (VOH) and Lewis (V) acid sites. For a comparison, H-adsorption is also studied.Highlights► On the basal V2O5 (001), NH3 adsorbs preferentially at Brönsted acid sites. ► On side (010) and (100), NH3 adsorbs strongly at Brönsted and Lewis acid sites. ► Surface relaxations have no influence on NH3 adsorption on saturated (001) surface. ► NH3-adsorption energies on (010) and (100) surfaces depend on the relaxed models.

Crude oil was subjected to extrography to obtain various acid compounds in multiple subfractions. Negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) and gas chromatography–mass spectrometry (GC–MS) were used to determine the acid compounds in the crude oil subfractions. Isoprenoidyl phenols with molecular formulas of C27H48O and C28H50O, which were previously deduced as sterol-type compounds, were highly enriched in a subfraction and confirmed by GC–MS. The mass peak with a molecular formula of C27H46O2 was identified as δ-tocopherol. The eluting sequence of the various compounds in crude oil was N1 carbazoles, followed by O1 class acid compounds, then O2 class acid compounds, and finally, N1O2, O3, and O4 class acid compounds. The results show that extrography is an adequate separation technique for partitioning crude oil acid compounds into various subfractions.

Detailed elemental composition and distribution of sulfides and thiophenic compounds in four subfractions of Kazakhstan vacuum gas oil (VGO) were determined by positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The sulfides in VGO subfractions were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI). The sulfur compounds in the oxidized VGO subfractions were reacted by methylation to form methylsulfonium salts and were then characterized. Elemental composition and distribution of sulfides and thiophenic compounds in the VGO subfractions were characterized by their double bond equivalents (DBE) values and carbon numbers before and after the oxidation reactions. The results showed that the S1 class species with DBE values of 6 and greater are likely thiophenic compounds, while those with DBE values less than 6 are sulfides. As boiling point of VGO increased, the abundance of thiophenic compounds increased. DBE value and carbon number of the compounds also increased.

Detailed characterization of oil sludge obtained from an electric dehydrator was performed using various analytical techniques and compared with that of its parent crude oil. The findings showed that the oil sludge was a stable emulsion consisting of oil, water, solids, and polyethers, which are chemical additives commonly used in the oilfield and refinery operations. Spectral peaks derived from positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) were assigned to sodium adducts [M + Na]+ for four types of polyethers that are nonionic surfactants. The Na1Ox class species found in the sludge at the bottom section of an electric dehydrator were likely due to their low solubility in oil as the number of oxygen atoms in these compounds increased. Polyethers were likely involved in the formation of oil sludge in the electric dehydrator. Sodium adducts, such as [M – 2H + Na]−, [M – 3H + 2Na]−, and [M – 4H + 3Na]−, of both C80 and C60+ ARN acids found in the fractions derived from acidified toluene extraction of oil sludge solids ionized by negative-ion ESI were also identified that confirm the assignment of ARN acids.

The size of residue molecules is crucial to catalyst design and petroleum use. An Athabasca tar sand vacuum residue was fractionated into 13 narrow fractions and an end-cut by supercritical fluid extraction and fraction (SFEF). Average molecule diameters and size distributions of the residue and its five SFEF cuts were determined from bulk-phase diffusion coefficients, which were measured at 308 K by a diaphragm cell. All five cuts show obvious polydispersity in size, with the end-cut possessing the broadest size distribution. A strong tendency of asphaltenes to aggregate suggests that the large size of the end-cut results from the aggregation of asphaltene molecules. The average hydrodynamic diameter of the end-cut was estimated to be 4.7 nm, as opposed to a range of 1.1−1.7 nm for the four narrow fractions. The average diameters of all five cuts can be correlated with their average molecular weight. In comparison to the size range of 1.1−4.7 nm for the narrow cuts, the feedstocks of the whole residue have a smaller size distribution of 1.4−3.9 nm. The attraction of heavier molecules at the beginning of the diffusion run and the disequilibrium at the end result in the smaller size distribution for the whole residue.

A coker heavy gas oil (CHGO) was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The resin fraction was separated into six subfractions by high-performance liquid chromatography (HPLC). The CHGO and its subfractions were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The mass spectra showed that the mass range of basic and neutral nitrogen compounds was 200−450 and 160−400 Da, respectively. Five nitrogen class species, N1, N2, N1O1, N1O2, and N1S1, were assigned in the positive-ion spectrum. Six nitrogen class species, N1, N2, N1O1, N1O2, N2O1, and N1S1, were assigned in the negative-ion spectrum. Among the identified nitrogen compounds, the N1 class species was dominant. The N1 class species were enriched in the resin fraction. The N2 class species are likely amphoteric molecules and were enriched in the asphaltene fraction. The composition of nitrogen compounds in the resin subfractions varied significantly in double-bond equivalence (DBE) and carbon number. As the polarity of the resin subfraction increased, the average molecular weights of the nitrogen compounds decreased, DBE values for each heteroatom class species increased, and the N2 class species became the dominant nitrogen compounds at the expense of the N1 class species.

A novel analytical method for identifying sulfides in petroleum and its fractions was developed. Sulfides in petroleum were selectively oxidized into sulfoxides using tetrabutylammonium periodate (TBAPI) and identified by positive-ion electrospray ionization (ESI) Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). A variety of model sulfur compounds were examined to evaluate the selective oxidization and ionization efficiencies for sulfur compounds in petroleum. Two fractions, straight-run diesel and saturates of Athabasca oilsands bitumen were investigated using this approach. The oxidization process was highly selective for sulfides from thiophenes and aromatic hydrocarbons. Oxidation generated sulfoxides were ionized by positive-ion ESI and analyzed by FT-ICR MS. Mass spectra revealed the composition characteristics of sulfides in the diesel by contrasting the double bond equivalence (DBE) and carbon number distribution of sulfur compounds before and after oxidation. The abundant sulfides in the straight run diesel and saturates fraction of oilsands bitumen had DBE values of 1−3 and 1−4, respectively.

The reaction mechanism for catalytic pyrolysis of C4 hydrocarbons on a modified ZSM-5 catalyst was analyzed. With the overall reactants and products classified into six species, a 6-lump kinetic model was established to describe the reactions with appropriate assumption. Rate constants of the kinetic model at 480, 500, 530, and 560 °C were estimated by a nonlinear least-squares regression method. Pre-exponential factors and apparent activation energies were then calculated according to the Arrhenius equation. The 6-lump kinetic model showed good prediction performance, with predicted yields close to the experimental ones. The variation in ethene and propene yields with reaction temperature and the weight hourly space velocity of C4 hydrocarbons were predicted using the lump model as basis.

Venezuela crude oil was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The sulfur compounds in the crude oil and its SARA fractions were reacted with iodomethane in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 class species were identified in crude oil derived methylsulfonium salts. The molecular composition and mass distribution of sulfur compounds in the subfractions were distinctly different. Small amounts of S1 class species (cyclic-ring sulfides) were present in the saturates fraction. Thiophenic sulfur compounds were dominant in the aromatics fraction. Complex multiheteroatoms (N1Sy, OxSy, and N1OxSy class species) were present in the resins and asphaltenes fractions. The relative abundance plots of double-bond equivalence (DBE) versus the carbon number of S1, S2, O1S1, and O2S1 class species showed that as the molecular polarity of the fraction increased, the DBE values of the abundant Sy class species increased. SARA fractionation isolates the highly aromatic sulfur species in the resins and asphaltenes fractions, which are not observed in the parent crude oil sample.

Sulfur compounds in Canadian oilsands bitumen were reacted with methyl iodide in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Heteroatoms were characterized by their class (number of nitrogen, oxygen, and sulfur heteroatoms), type [rings plus double bonds (DBE)], and carbon number distribution. The S1, S2, S3, O1S1, O1S2, O2S1, and N1S1 sulfur-containing class species were identified in bitumen-derived methylsulfonium salts. The molecular weights of the sulfur compounds were varied from 200 to 700 Da. The Sx class species were the predominant heteroatom compounds. The S1, S2, and S3 class species comprised 74%, 11%, and 1%, respectively, of the total identified species. As the sulfur atom number increased, the DBE of the abundant Sx class species shifted to a higher value. Sulfur species identified from the spectrum had a DBE value of less than 20. The potential molecular structures of heteroatom classes were inferred from the DBE distribution and carbon number data. Methylation followed by ESI MS is an effective technique for sulfur speciation of bitumen.

A Liaohe crude oil was separated as saturates, aromatics, resins, and asphaltenes (SARA) and neutral nitrogen fractions. The crude oil and its subfractions were analyzed by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The results show that neutral nitrogen and acidic heteroatom compounds in the crude oil contain 15−55 carbon atoms with double-bond equivalent (DBE) values of 1−27, containing N1, N2, N1O1, N1O2, N1O3, N1O4, O1, and O2 heteroatom classes. No molecules in the saturate fraction can be ionized by ESI. The aromatic fraction contains N1 and N1Ox compounds with high molecular weights but low DBE values. The resin and asphaltene fractions contain highly aromatic and acidic class species, which are enriched in oxygen- and nitrogen-containing compounds with lower molecular weights than those found in the aromatic fraction. The distribution patterns of N1, N1O1, and O1 class species in the resins and asphaltenes are similar. The mass spectrum of the neutral nitrogen fraction differs from those for the bulk crude oil and its SARA fractions; the neutral nitrogen fraction is enriched with N1 and N1O1 class species. Neutral nitrogen compounds with molecular weights lower than 200 were discriminated in the FT-ICR MS spectrum under the chosen operating conditions. However, the nitrogen species detected by gas chromatography only accounted for a small amount of that found in the neutral nitrogen fractions. Some of the neutral nitrogen species were entrained in asphaltenes during the deasphalting step of sample fractionation.

The pyrolysis performance of catalytic cracking naphtha and coker naphtha on different carriers and an active catalyst was investigated in a confined fluidized bed reactor. For the pyrolysis of catalytic cracking naphtha on quartz grain, the yield of total light olefins increased with the enhancement of temperature, while it varied slightly with increasing weight hourly space velocity (WHSV) and steam/oil weight ratio. The optimal reaction temperature, WHSV, and steam/oil weight ratio were 700 °C, 5.7 h−1, and 0.5, respectively. The selectivity of total light olefins of coker naphtha was better than that of catalytic cracking naphtha under the optimal reaction conditions. The surface area and pore size of the inert carrier showed little effect on the pyrolysis performance. The introduction of the active catalyst could improve the conversion and the yield of total light olefins.

This paper presents experimental and computational studies on the flow behavior of a gas–solid fluidized bed with disparately sized binary particle mixtures. The mixing/segregation behavior and segregation efficiency of the small and large particles are investigated experimentally. Particle composition and operating conditions that influence the fluidization behavior of mixing/segregation are examined. Based on the granular kinetics theory, a multi-fluid CFD model has been developed and verified against the experimental results. The simulation results are in reasonable agreement with experimental data. The results showed that the smaller particles are found near the bed surface while the larger particles tend to settle down to the bed bottom in turbulent fluidized bed. However, complete segregation of the binary particles does not occur in the gas velocity range of 0.695–0.904 m/s. Segregation efficiency increases with increasing gas velocity and mean residence time of the binary particles, but decreases with increasing the small particle concentration. The calculated results also show that the small particles move downward in the wall region and upward in the core. Due to the effect of large particles on the movement of small particles, the small particles present a more turbulent velocity profile in the dense phase than that in the dilute phase.

•A novel mechanism for the SCR cycle of NO by NH3 on the V2O5 goes in module steps.•L-acid, single B-acid, double B-acid, and the defective sites are formed in turn.•At the first three kinds of active sites, NO and NH3 are converted into N2 and H2O.•The addition of O2 plays a role of resuming the defective surface to the V2O5.Selective catalytic reduction (SCR) of NO via NH3 and O2 over the V2O5 surface has been the focus of considerable research interest due to its role in mitigating air pollution. Our theoretical investigations at the periodic DFT level reveal that the Lewis acid active center could be a starting point in the dominant Eley–Rideal mechanism, while other active sites might either exist or be formed during the reaction process and play roles in competition. In this systematic study, an integrated catalytic cycle consisting of four module steps (i) NH3 + NO + V2O5 → N2 + H2O + HV2O5, (ii) NH3 + NO + HV2O5 → N2 + H2O + HHV2O5, (iii) NH3 + NO + HHV2O5 → N2 + 2H2O + HV2O4, and (iv) NH3 + NO + O2 + HV2O4 → N2 + 2H2O + V2O5 is proposed by using uniform theoretical model for the most possible processes involved. This suggested mechanism is easy to understand and agrees well with the experimental observations and results of other theoretical studies. More satisfactory, differences in the catalytic activity for diverse active sites can be explained not only by relative energies and barrier heights but also by geometries of the intermediates and transition states appeared in the cycle. For Step I, the formation of species HOVNH2 followed by H-migration of HO at Lewis acid site Va is decisive because of the very high activation energy (63.6 kcal/mol), while following transformations and the release of N2 and H2O are relatively easy. The most favorable path is however going through Vb site for Step I. The change from intermediate 1 to 2 must suffer a barrier of 52.7 kcal/mol, which is only 10.9 kcal/mol lower than that for Va. After the formation of one VOH Brønsted acid site, the transformation from intermediate 11 to 12 is the most difficult process for Step II (Ea = 38.6 kcal/mol). The most stable configuration for double VOH sites displays two potential pathways depending on the priority of removing H2O at the late stage of Step III. Our calculations indicate that Step IV favors to occur through HVt1 related pathway in which the oxygen vacancy and VOH sites are opposite to each other. This novel multi-step mechanism can provide us a deeper understanding of the SCR reaction over V2O5 surface, and we expect that the design of SCR catalyst could be improved on the basis of theoretical predictions related to these key sites and important processes.Graphical abstractFour elementary steps served as blocks can be flexibly combined to describe the SCR mechanism of NO via NH3 over V2O5 (0 0 1) surface in the presence of O2.Download high-res image (62KB)Download full-size image

•A series of novel mesoporous Al2O3 with different crystal forms was synthesized.•NiMo/δ-Al2O3 exhibited superior hydrodesulfurization (HDS) activities.•Effect of crystal forms on 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS was found.•Hydrogenation (HYD) route was the main pathway in 4,6-DMDBT HDS over NiMo/δ-Al2O3.•The HDS reaction network of 4,6-DMDBT over NiMo/δ-Al2O3 was proposed.Mesoporous Al2O3 (MA) materials with different crystal forms were synthesized from the boehmite sol. A series of MA materials were used as supports for sulfided NiMo catalysts in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The as-synthesized MA materials with different crystal forms and the corresponding NiMo catalysts were characterized using XRD, nitrogen physisorption, FTIR, pyridine FTIR, UV–vis, Raman, H2 TPR, XPS, and HRTEM characterization methods. The NiMo/δ-Al2O3 (NiMo/δ-MA) catalyst exhibited the highest DBT and 4,6-DMDBT conversion at all the weight hourly space velocities (WHSVs); moreover, its DBT conversion (99.6%) was about twice that of the commercial NiMo/Al2O3 (NiMo/C-MA) catalyst (50.2%), while its 4,6-DMDBT conversion (65.8%) was more than four times that of the NiMo/C-MA catalyst (15.5%) at 613 K, 4.0 MPa, 200 ml/ml, and 150 h−1. The superior catalytic performance of the NiMo/δ-MA catalyst could be ascribed to the synergistic effect of desirable textural properties, moderate acidity, suitable metal–support interaction, appropriate dispersion, and excellent stacking morphology of the active phases. 4,6-DMDBT HDS over the NiMo/δ-MA catalyst showed the highest HYD/DDS ratio (3.08), indicating that the HYD pathway was the main reaction route. Furthermore, an HDS reaction network was proposed for 4,6-DMDBT over NiMo/δ-MA.Download high-res image (238KB)Download full-size image

•One-step synthesis of supported Au@Pt NPs is realized by GBMR method.•Amounts of active oxygen species are increased by synergistic effect of Au core and Pt shell.•The contact between soot particles and catalysts is improved by 3DOM support.•3DOM Au@Pt/CZO catalysts exhibit super catalytic performance for soot combustion.•Pt shell can improve the stability of supported Au(core)-based catalysts.Supported Au@Pt core–shell nanoparticles (NPs) were successfully synthesized on three-dimensionally ordered macroporous (3DOM) oxides by a one-step gas bubbling-assisted membrane reduction (GBMR) method. The Au@Pt core–shell NPs were highly dispersed on the pore wall of oxides and the Pt shell was obtained by direct epitaxial overgrowth on the surface of the Au core. The multifunctional nanocatalysts were used for diesel soot oxidation. 3DOM structure facilitates the contact between soot particles and catalysts, and the synergetic effect of the Au core and Pt shell significantly increases the surface concentration of active O2− species. 3DOM Ce0.8Zr0.2O2-supported Au@Pt core–shell NP catalyst is one of the best catalysts reported so far for soot oxidation under “loose” contact between soot and catalyst. The stability of the Au-based catalysts for soot oxidation is also improved due to the formation of an Au@Pt core–shell structure.Graphical abstractDownload high-res image (85KB)Download full-size image

This work reports a striking enhancement of catalytic performance of gold nanoparticles (NPs) with average diameter of 3.2 nm partially (ca. 32–40%) confined in the cavity of carbon nanotubes (CNTs) for the gas-phase hydrogenation of 1,3-butadiene (BD), as well as liquid-phase hydrogenation of cinnamaldehyde (CAL). The reaction rates and turnover frequencies of the CNTs confining gold NPs exceed those with a similar size deposited on the outer surface of CNTs and activated carbon by more than one to two orders of magnitude in both two reactions. The selectivity to monobutenes and hydrocinnamaldehyde is up to 100% and 91% at 100% and 95% conversions of BD and CAL, respectively. Au/CNTs catalysts were characterized in depth to establish their structure–property relationship. The peculiar interaction of confined gold NPs with the surface of CNTs facilitates the dissociation/activation of H2, which is the rate-determining step for hydrogenation reactions demonstrated by kinetic studies.Graphical abstractCNTs-confined gold nanoparticles (ca. 3.2 nm) show striking enhancement catalytic performance compared with those located on the outer surface and activated carbon for hydrogenation reactions.Download high-res image (173KB)Download full-size imageHighlights► Au/CNTs with Au nanoparticles of 2–5 nm were prepared by the gold colloid method. ► The ratio of gold nanoparticles filled inside nanotubes to the total was different. ► CNTs-confined Au nanoparticles show high performance for hydrogenation reactions.

Micro-mesoporous composite material Beta-KIT-6 (BK) with the BEA microporous structure and cubic Ia3d mesoporous structure was synthesized and used as catalyst support for the hydrodesulfurization of dibenzothiophene. The composite material possessed both KIT-6 and Beta structures. NiMo/BK had similar acidity as NiMo/Beta and possessed more acid sites and stronger acidity than NiMo/KIT-6 and NiMo/SBA-15. NiMo/BK showed the highest dibenzothiophene hydrodesulfurization activity among all the catalysts that were studied, and the dibenzothiophene conversion on NiMo/BK was about 2–3 times that of NiMo/Al2O3. The acidity of NiMo/BK enhanced the activity of the direct desulfurization pathway more significantly than that of the hydrogenation pathway. Cyclohexen-1-yl-benzene was detected as intermediate of the hydrogenation pathway. NiMo/KIT-6 exhibited higher activity than NiMo/SBA-15 due to the superior mass transfer ability of the cubic Ia3d mesoporous structure.Micro-mesoporous composite material of Beta-KIT-6 (BK) was successfully synthesized. Superior mass transfer property combined with suitable acidity make Beta-KIT-6-supported NiMo an excellent catalyst for the hydrodesulfurization of dibenzothiophene.Download high-res image (119KB)Download full-size image

The hydrodynamics of binary mixture of Geldart Group A and D particles in a turbulent fluidized bed were investigated by experiment and computational fluid dynamics (CFD) method in this paper. The results showed that at low gas velocity, the binary mixtures tend to segregate. At moderate gas velocity, they incline to mix well in the dense phase. Further increasing gas velocity, small particles are entrained and accumulate in the upper regime of the bed, and a segregation trend of the binary mixture appears again. At high gas velocities, segregation efficiency in the continuous classification process increases with increasing the gas velocity and mean residence time of the binary mixture, however, decreases with increasing the small particle content. A strong particle recirculation appears all over the dense phase of the bed, causing an approximately uniform solid composition in radial direction of the fluidized bed.

A large probe molecule, cumene, was chosen to study diffusion and adsorption on mesopore structured ZSM-5, using a high precision intelligent gravimetric analyzer. Compared with ZSM-5, a 2–3 order of magnitude increase in the diffusion coefficient of cumene was observed on the mesopore structured ZSM-5. The increased adsorption rate and the increased adsorption heat with increased cumene coverage, supported a mechanism of diffusion, phase transition, and re-arrangement of cumene molecules during the adsorption process on the mesopore structured ZSM-5. The introduced mesopores also decreased the diffusion–adsorption activation energy by a factor of 4.6. Consequently, although the amount of strong Brønsted acid sites decreased, the conversion of cumene on the mesopore structured ZSM-5 catalyst doubled compared to ZSM-5 catalyst, and the total light olefins yield increased by 2.47 wt% with Daqing heavy oil as a feedstock.

A red pine fast pyrolysis bio-oil was subjected to sequential solvent fractionation into n-hexane soluble (HS), ether soluble (ES), ether insoluble (EIS), dichloromethane soluble (DS), and methanol soluble (MeS) fractions. The volatile components of bio-oil were analyzed by gas chromatography–mass spectrometry (GC–MS), indicating the presence of acids, aldehydes, ketones, alcohols, phenols, and anhydromonosaccharides, which consisted of methoxy, hydroxy, and carbonyl functional groups. These results imply that the bio-oil was similar to the most reported fast pyrolysis bio-oil samples in molecular composition. The bio-oil and its five subfractions were analyzed by negative-ion electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The predominant compounds in bio-oil were O2–O17 class species with 1–22 double-bond equivalent (DBE) values and 4–39 carbon numbers. The most abundant class species in biocrude oil, HS, ES, EIS, DS, and MeS subfractions were O7, O6, O8, O10, O7, and O8 class species, respectively. The predominant EIS subfraction presented an obvious relative low DBE value, sustaining the tentative identification as “sugar fraction”. The predominant compounds in DS subfraction were likely lignin dimers, whereas those in MeS subfraction should be lignin dimers and trimers. The number of oxygen atoms of the bio-oil compounds was negatively correlated with the average DBE value, indicating that oxygen atoms were present in various functional groups of the bio-oil compounds. The N1Ox class species were also identified, which contained 1–16 DBE and 6–30 carbon numbers.

Nanosheet ZSM-5 zeolite with highly exposed (010) crystal planes demonstrates high reactivity and good anti-coking stability for the catalytic cracking of n-heptane, which is attributed to the synergy of high external surface area and acid sites, fully accessible channel intersection acid sites, and hierarchical porosity caused by the unique morphology.

A CdS encapsulated carbon nanotube (CNT) photocatalyst was prepared by a liquid-chemistry method. Through filling of CNTs with CdS, the aggregation of CdS was prevented efficiently by the good confinement effect of CNTs, and the photocatalytic performance of CdS was enhanced by 2.5 times via synergistic integration of the confinement effect of CNTs and heterojunction between CNTs and CdS. The photostability of CdS encapsulated in and attached on CNTs was investigated systematically through methylene blue photocatalytic degradation, X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy. The results indicate that the photocorrosion of CdS is successfully suppressed when it is encapsulated in the CNTs. The mechanism analysis suggests that spatial synergy of the CdS and powerful adsorptivity of CNTs are the primary causes for photocorrosion inhibition. Our efforts propose a new scheme to remarkably promote both the photostability and photocatalytic activity of photocorrosion-susceptible photocatalysts.