In selective hydrodesulfurization processes for hydro-upgrading fluid catalytic cracking (FCC) naphtha with high olefin and sulfur contents, it is a common practice to split the feeding full-range FCC naphtha into a light fraction and a heavy fraction. This operation can effectively alleviate olefin saturation and thereby octane loss. Thus, the determination of a suitable cutting temperature plays a vital role in guaranteeing the success of the operation. Starting by fractionating two FCC naphthas into nine narrow cuts, this paper shows that, despite the great differences in the properties of the two FCC naphthas, both hydrocarbons and sulfides have almost the same distributions in the nine cuts. More importantly, it was observed that the distribution of sulfides in the narrow cuts is irrelevant to their true boiling points because of the formation of azeotropes between sulfides and hydrocarbons. On the basis of these findings, a simple model for estimating thiophene content in light FCC naphtha and, thereby, determining the cutting temperature was deduced and its applicability was verified using three other FCC naphthas sampled from different refineries. The salient feature of the model lies in that it only uses the total thiophene content of the feeding FCC naphtha to perform the estimation without the necessity to carry out time-consuming and cost-expensive pre-hydrogenation and fractionation tests. Thus, it can provide in-prior estimation for the design and operation optimization of FCC naphtha hydro-upgrading processes.

Silica hollow microspheres (SHMs) with size-tunable penetrating macropores from 250 nm to 560 nm are prepared by a water/oil/water ternary phase emulsion system. Furthermore, the thus-obtained SHMs can serve as a superior support to fabricate supported palladium catalysts for the hydrogenation of bulky polystyrene molecules.

An energy-saving and environmentally friendly approach to synthesize zeolite Y from natural aluminosilicate minerals without the involvement of aluminum- and silicon-containing inorganic chemicals was developed. When used as a fluid catalytic cracking catalyst, the resulting zeolite Y exhibited an outstanding catalytic cracking performance.

Mono-dispersed Mo-based inorganic–organic hybrid nanocrystals (HNCs) in water phase with a uniform size of ca. 3 nm have been successfully synthesized via a simple and facile method at room temperature. With the help of comprehensive characterizations, the chemical composition and structure of this hybrid material was determined: Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. Interestingly, the resultant nanocrystals can spontaneously self-assemble into lamellar mesoscale nanocomposites with an alternative arrangement of inorganic and organic layers when simply removing water or adding ethanol into the solution. The distance between two layers depends on the length of the quaternary ammonium cations used, indicating that the cationic surfactant functions as a structure-directing agent and induces the formation of an ordered lamellar mesostructure. Moreover, we found that the lamellar mesoscale structure can be disassembled into well-dispersed HNCs when being re-dispersed into a large amount of water. The unique self-assembly and disassembly behavior of the mono-dispersed HNCs may have great potential for fabricating Mo-based functional materials.

This article presents a novel strategy to prepare alumina-supported Mo and MoNi hydrodesulfurization (HDS) catalysts using Mo-based inorganic–organic hybrid nanocrystals (HNCs) as a superior precursor under moderate hydrothermal conditions. The characterization results revealed that each HNC in the aqueous solution has a size of ca. 2.5 nm and shows a core–shell structure with one Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. The proposed approach not only significantly promotes the dispersion of supported Mo species, but also greatly enhances the stacking of MoS2 active phase, endowing the resulting catalysts with sufficient and accessible Ni–Mo–S active sites and thereby with a remarkably enhanced HDS performance as compared to their counterparts prepared by the conventional impregnation method. Thereby, a novel precursor for preparing Mo-based catalysts was successfully developed and the roles of the HNC-derived preparation method in tuning the size and morphology of supported metal sulfide nanoparticles in HDS catalysts were demonstrated, shedding a light on the rational design and controllable fabrication of supported metal sulfide catalysts.

This article proposes a novel cetyltrimethylammonium bromide- and fluorine-assisted hydrothermal deposition method for modulating the morphology of supported metal nanoparticles in NiWF/Al2O3 hydrodesulfurization (HDS) catalysts. The proposed approach significantly promotes the dispersion of supported W species by bridging and anchoring the precursor of W species onto the surface of fluorinated Al2O3 as well as restraining the subsequent aggregation of W species in calcination. The dual effects of the improved dispersion and F-enhanced stacking endow the corresponding catalyst with superior morphology featured by sufficient and accessible Ni–W–S active phases and thereby with a remarkably promoted HDS performance as compared to its counterpart prepared by the conventional impregnation method. We successfully demonstrate the roles of the cetyltrimethylammonium bromide- and fluorine-assisted hydrothermal deposition method in tuning the morphology of supported metal nanoparticles in HDS catalysts, shedding light on the rational design and fabrication of supported metal sulfide catalysts.

Mesoporous Si-SBA-15 was applied to enhance the FCC gasoline selective hydrodesulfurization (HDS) performance of conventional Co-Mo/Al2O3 catalysts and the physicochemical properties of the resulting catalyst were compared with those of Co-Mo/Al2O3 catalysts incorporated with macroporous kaolin, mesoporous Si-MCM-41 and microporous Si-ZSM-5. The selective HDS performances of all the catalysts were assessed with different FCC gasolines as feedstocks. The results showed that the HDS selectivity of the catalysts was closely related to the Mo sulfidation that depends on catalyst surface area and metal-support interaction. With the superior Mo sulfidation, the Co-Mo/Si-SBA-15–Al2O3 catalyst had the optimal HDS selectivity for not only the full-range FCC gasolines but also the heavy fractions thereof. The present article demonstrates the significance of enhancing Mo sulfidation in improving HDS selectivity and thus sheds a light on the development of highly selective HDS catalysts.Research highlights► Incorporation of Si-SBA-15 into Co-Mo/Al2O3 increases catalyst surface area. ► Incorporation of Si-SBA-15 weakens the metal-support interaction in Co-Mo/Al2O3. ► The two effects enhance the Mo sulfidation and thus HDS selectivity of the catalyst.

Highly ordered mesoporous silica and aluminosilicate materials with extremely high hydrothermal stability have been synthesized successfully at a high hydrothermal treatment temperature of 200 °C by using inexpensive sodium silicate and sodium aluminate as the silica source and alumina source, respectively. The resultant mesoporous materials possess a hexagonal mesostructure and extraordinary stability towards the steam treatment at 800 °C for 2 h. In addition, the direct incorporation of Al into the mesoporous framework can further enhance the hydrothermal stability of ordered mesoporous materials. Our contribution provides a commercially important approach to synthesize ordered mesoporous materials with highly hydrothermal stability, which may find potential applications for the catalytic cracking in the petroleum industry.

Highly ordered mesoporous materials with extremely high hydrothermal stability have been successfully synthesized by a novel and facile approach. Our method is built on the understanding that the hydrothermal treatment process plays an important role in the synthesis of mesoporous materials. It is proposed that in order to use high temperature hydrothermal treatment to increase the inorganic framework cross-linkage, an important requirement is that the organic surfactants must be retained as much as possible to maintain the preformed organic−inorganic composite mesostructure against framework shrinkage during the hydrothermal treatment process. This requirement can be achieved by enhancing the surfactant−silanol interaction at the organic−inorganic interface through adjusting the hydrothermal treatment pH and adding acetic acid (HAc) during the synthesis. When a high temperature (∼200 °C) hydrothermal treatment is employed, ordered mesoporous materials can only be obtained in a hydrothermal treatment pH range of 1−3. When the hydrothermal treatment pH is near the isoelectric point of silica, the highest silanol density on silica walls can entrap the largest amount of surfactants within pores, resulting in highly ordered mesostructured materials. Moreover, the disadvantage of the hydrothermal treatment under strong acidic conditions widely adopted in the literature has been revealed. Compared to previous reports, our approach is simple and does not involve environmentally unfriendly or expensive agents, thus is easy to be scaled up for industrial applications. Most strikingly, the highly ordered mesostructure of aluminosilicate synthesized by our approach can be maintained after steam treatment at 800 °C for 5 h with only a 4.9% decrease in the Brunauer−Emmett−Teller surface area. Our achievements have added new contributions to understanding the preparation of highly ordered and highly stable mesoporous materials, which sheds light on the practical applications of this new family of porous materials in the petroleum and petrochemical industry.

This article describes a new set of scale-up parameters of spouted beds derived from solid stress analyses. Compared with the first set of scale-up parameters of spouted beds proposed by He et al. [He Y. L., Lim C. J., Grace J. R., Scale-up studies of spouted beds, Chemical Engineering Science, 52 (2), 329–339, 1997], this set introduced a new parameter, the coefficient of restitution of particles, that accounts for the effects of particle–particle collisions in the spout region of a spouted bed. To verify the present set of scale-up parameters, a series of experiments were designed and conducted in two spouted beds of 80 mm and 120 mm in diameter, respectively, operated in the different testing cases consisting of different combinations of the involved scale-up parameters. The results showed that the more closely the scale-up parameters of the spouted beds tested were matched, the higher hydrodynamic similarity could be achieved. The comparisons of the hydrodynamic properties such as fountain height, spout diameter and bed voidage measured in the different testing cases revealed that the coefficient of restitution of particles could significantly impact the particle–particle interactions and thus its effects should be taken into account in scaling-up spouted beds.In this paper, we show that the more closely the scale-up parameters of the spouted beds were matched, the higher hydrodynamic similarity could be achieved, and the coefficient of restitution of particles could significantly impact the particle–particle interactions and thus its effects should be take into account in scaling-up spouted beds.

The reactivities of model hydrocarbons (n-paraffins, i-paraffins, olefins, naphthenes, and aromatics) typical for fluid catalytic cracking (FCC) gasoline were investigated over a Ni−Mo/modified HZSM-5 + Al2O3 catalyst. Olefins had the highest reactivity and were unidirectionally converted into molecules of the other groups, especially i-paraffins and aromatics. On the basis of the results, a reaction mechanism was proposed for olefin hydroisomerization and aromatization in the presence of excess hydrogen. During the olefin hydroisomerization and aromatization, the initial adsorption sites of the olefins are the acid sites rather than the metal sites of the bifunctional catalyst. The olefin hydroisomerization reaction is in accordance with the hydrogen spillover concept. The function of the metal sites is to dissociate hydrogen molecules into active H ions, and the acid sites are the reaction sites. The olefin aromatization in the presence of hydrogen occurs through diene and cyclo-olefin intermediates by hydrogen transfer/dehydrogenation and cyclization. The results obtained form the fundamental basis for the olefin conversion in the presence of hydrogen and shed a light on the correlation between the reactivity of model compounds and that of real gasoline with complex compositions.

This article describes a novel citric acid treatment method for realuminating dealuminated HZSM-5 zeolite and its application in enhancing the performance of the zeolite derived FCC gasoline hydro-upgrading catalysts. A series of modified HZSM-5 zeolites were prepared by streaming and/or acid treatments and the influences of the different modification methods on the acidity, pore structure and catalytic performance of the modified HZSM-5 zeolite supported catalysts were compared in the present investigation. The results showed that compared with the single HCl or citric acid treatment, the steaming treatment, and the steaming/HCl treatments, the citric acid treatment after steaming exclusively increased the amount of framework Al species due to its realumination effect on the steamed HZSM-5 zeolite. This realumination effect of the citric acid treatment could optimize the ratio of framework Al to extra-framework Al in the steamed HZSM-5 zeolite and thus greatly improve the acidity distribution and pore structure of the corresponding catalyst. The catalytic performance assessments of the different zeolite supported catalysts for FCC gasoline hydro-upgrading revealed that the catalyst supported on the steaming/citric acid treated HZSM-5 zeolite had balanced initial and long-term activities in hydrodesulfurization, hydroisomerization and aromatization, high liquid yield and improved gasoline road octane number. The superior catalytic performance of the catalyst could be closely related to its suitable ratio of framework Al to extra-framework Al achieved by the combinational use of the steaming dealumination and the citric acid realumination, fully demonstrating the effectiveness of the steaming and citric acid treatments in optimizing the physicochemical properties and catalytic performance of HZSM-5 zeolite supported catalysts.

The hydrodynamics of an annulus airlift reactor (AALR) was studied and compared with that of a slurry bubble column reactor (SBCR) with silica sands of 75–125 μm in size as solids, city tapping water as liquid phase, and air as gas phase in the present investigation. The effects of superficial gas velocity and solids concentration on gas holdup and solids distributions were investigated. The results showed that the local average gas holdup decreased along the column height, and the average gas holdup decreased with the increasing solids concentration, but this tendency became less at higher solids concentrations. It was found that the effect of superficial gas velocity on axial solids distribution was negligible over the gas velocity range investigated, as long as the solids in the column could be suspended. Increasing solids concentration led to flatter axial solids holdup profiles. The axial distributions of solids concentration and gas holdup in the AALR were much more uniform than those in the SBCR, and slurry circulation in the AALR damped the effects of increasing solids concentration on the hydrodynamics. These advantages of an AALR over a SBCR are especially important for some catalytic reaction processes in three-phase systems such as Fischer–Tropsch synthesis and methanol synthesis.

A thermally stable MCM-41/γ-Al2O3 composite (“Composite 2”) was obtained by in situ synthesis using boehmite, a hydrated γ-Al2O3, and compared to a MCM-41/γ-Al2O3 composite (“Composite 1”) made using pure γ-Al2O3. The two composites were studied by means of X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), laser particle size analyzer, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDS), and nitrogen adsorption isotherm measurements. The results showed that with boehmite as the initial material, the thermal stability of the MCM-41 in Composite 2 was greatly improved and thus its specific surface area and pore volume were significantly increased. It was also found that in the two composites MCM-41 grew in two different mechanisms: in Composite 1 MCM-41 grew on the outer surface of γ-Al2O3 or occurred as non-in situ crystallization product, whereas in Composite 2 MCM-41 overgrew only on the internal surface of boehmite grains.

•A top-down method to efficiently depolymerize natural minerals was developed.•The reorganization of depolymerized intermediates into hierarchical ZSM-5 zeolite was achieved.•Neither inorganic aluminum and silicon salts nor mesoscale template and post-treatment were used.•The resulting hierarchical ZSM-5 zeolite showed superior catalytic performance.In this article, we describe a novel strategy for synthesizing hierarchical ZSM-5 zeolites via the nanoscale depolymerization–reorganization of natural aluminosilicate minerals. This strategy involves two important steps: the first is the top-down depolymerization of one aluminum-rich aluminosilicate mineral via a novel submolten salt system and one silicon-rich aluminosilicate mineral via conventional thermal treatment into nanoscale building blocks, and the second is the bottom-up rearrangement and reorganization of nanoscale building blocks in the synthesis system into hierarchical ZSM-5 zeolites. When used as a fluid catalytic cracking catalyst additive, the resulting ZSM-5 zeolite with hierarchical micro–mesoporous structure exhibited high activity and selectivity for valuable products in preliminary oil refining tests. The salient features of the strategy lie in that it neither involves any inorganic aluminum and silicon salts as precursors nor uses any secondary mesoscale template and post-treatment to create mesopores, thus demonstrating itself to be a green route to synthesizing hierarchical zeolites.Download high-res image (87KB)Download full-size image

This article proposes a one-step strategy to hydrothermally synthesize SAPO-11 with hierarchical micro- and meso-porous structure. The structure and acidity properties and the isomerization performance of the resulting hierarchical SAPO-11 were extensively characterized and assessed, respectively, and compared with those of a microporous SAPO-11. The results showed that the SAPO-11 with mutually interpenetrating micropores and mesopores had been obtained by introducing tetradecylphosphoric acid into the synthesis system of microporous SAPO-11. Compared with microporous SAPO-11, the hierarchical SAPO-11 had much higher external surface and mesoporous volume, and more active sites with suitable Brönsted acid strength. These advantages endowed the hierarchical SAPO-11-based catalyst with superior isomerization activity, enhanced selectivity to di-branched products, and decreased cracking selectivity. The strategy proposed opens a new route to synthesizing a variety of hierarchical mesoporous SAPO molecular sieves for size-selective catalytic conversions of relatively large hydrocarbon molecules.Graphical abstractThe P atoms in alkylphosphonic acid are introduced into the SAPO-11 framework, and thus the long alkyl groups bonded with these P atoms induce the formation of intracrystal mesopores after calcination. The interpenetrating micro–mesoporous channels of the hierarchical SAPO-11 endow the resulting catalyst with the superior di-branched isomer selectivity.Download high-res image (97KB)Download full-size imageHighlights► The P atoms in alkylphosphonic acid are introduced into the SAPO-11 framework. ► The long alkyl groups bonded with these P atoms induce intracrystal mesopores. ► The hierarchical SAPO-11-based catalyst has superior di-branched isomer selectivity.

Highly ordered mesoporous Al-SBA-15 with high aluminum content and high hydrothermal stability has been synthesized by a new pH-adjusting and high-temperature hydrothermal treatment approach. Thus-prepared samples were characterized by X-ray fluorescence spectroscopy, X-ray powder diffraction, 27Al nuclear magnetic resonance spectroscopy, N2 adsorption–desorption, temperature-programmed desorption of ammonia, Fourier transformed infrared spectroscopy with pyridine adsorption, temperature-programmed reduction with hydrogen, and high-resolution transmission electron microscopy. The results showed that Al-SBA-15 had high aluminum loading (with its molar Si/Al ratio of 5.1, similar to that of the initial gel mixture) and homogenously distributed Al species in the walls. Moreover, the product showed extremely high hydrothermal stability (with only a 15.2% decrease in surface area after steaming at 800 °C for 5 h) and moderate acidity. An Al-SBA-15-supported NiW hydrodesulfurization catalyst was prepared and evaluated using dibenzothiophene hydrodesulfurization. Compared with γ-Al2O3- and SBA-15-supported catalysts, the Al-SBA-15-supported NiW catalyst showed outstanding hydrodesulfurization activity.Al-SBA-15 was prepared by adjusting the pH value during high-temperature hydrothermal treatment. Appropriate metal–support interaction combined with suitable acidity endowed the NiW/Al-SBA-15 catalyst with excellent hydrodesulfurization activity.Download high-res image (107KB)Download full-size image

Using rectorite extrudates from calcined rectorite powder as the starting material, a series of ZSM-5/rectorite composites were prepared via the in-situ crystallization method. The physicochemical properties and propylene boosting performance of the resulting samples were characterized by using X-ray diffraction, scanning electronic microscopy/energy dispersive spectrometer, N2 adsorption-desorption, and Fourier transformed infrared spectroscopy of pyridine adsorption, respectively, and assessed by using Daqing atmospheric residue as feedstock. The results showed that the ZSM-5/rectorite composites in which the ZSM-5 phase grows in-situ as a 2-3 ím thick layer on rectorite particles have a trimodal microporous-mesoporous-macroporous structure and thus exhibit outstanding propylene boosting performance. Compared with a commercial ZSM-5 incorporated fluid catalytic cracking catalyst, the ZSM-5/rectorite composite incorporated catalyst increased the yield and selectivity of propylene by 2.44% and 5.35%, respectively.

•Increasing MgO loading leads to the increased ratio of Lewis acid sites to Brönsted ones.•The suitable ratio of medium and strong Lewis acid sites to medium and strong Brönsted ones is about 1.•The suitable optimum ratio of total Lewis acid sites to total Brönsted ones is 2–3.•Formation of coke with lower H/C ratio is the main factor accounting for catalyst deactivation.On-stream stability of fluid catalytic cracking (FCC) naphtha hydro-upgrading catalysts that convert olefins into high-octane isoparaffins and aromatics is crucial for guaranteeing the long-term operation of industrial units, and therefore suppressing catalyst deactivation due to coking becomes the focus of FCC naphtha hydro-upgrading process and catalyst development. Here we report a simple and novel strategy to enhance the on-stream stability of a HZSM-5 based FCC naphtha hydro-upgrading catalyst by magnesium modification. The characterization and catalytic test results showed that the incorporation of a suitable amount of MgO can adjust the ratio of Lewis acid sites to Brönsted ones and thereby significantly improve stability of the resulting catalyst.Download high-res image (214KB)Download full-size image

A series of potassium and/or phosphorus modified Co–Mo/Al2O3 FCC gasoline hydro-upgrading catalysts were prepared and the influences of potassium and/or phosphorus on the morphology, acidity and catalytic performance of the resulting catalysts were studied in the present investigation. The results showed that, compared to the single potassium or phosphorus modified catalyst, the Co–Mo–K–P/Al2O3 catalyst in which the atomic ratio of potassium to phosphorus was 2.0 could better balance the hydrodesulfurization and olefin saturation activities due to the compromised dispersion and stacking of MoS2 slabs on the support as well as the good acidity property, and thus present the excellent selectivity in hydrodesulfurization. The present investigation also demonstrates the superiority of adjusting the K/P atomic ratio in optimizing the structure of MoS2 slabs and thus provides a novel method for developing highly selective hydrodesulfurization catalysts.

This article describes a novel hydrothermal deposition method for preparing highly dispersed NiW/γ-Al2O3 catalysts and demonstrates its advantages over the conventional impregnation method. Via the hydrothermal precipitation reactions between sodium tungstate and hydrochloric acid and between nickel nitrate and urea, respectively, the active species W and Ni were deposited on γ-Al2O3. In the hydrothermal deposition of WO3, a surfactant hexadecyltrimethyl ammonium bromide (CTAB) was used to prevent the aggregation of WO3. The characterization results obtained by means of X-ray photoelectron spectroscopy (XPS), N2 adsorption and high-resolution transmission electron microscopy (HRTEM) measurements showed that compared with the catalyst prepared by the conventional impregnation method, the catalyst with the same metal contents prepared by the hydrothermal deposition had much higher W and Ni dispersion, higher specific surface area, larger pore volume, the significantly decreased slab length and slightly increased stacking degree of sulfided W species, leading to the significantly enhanced dibenzothiophene (DBT) hydrodesulfurization (HDS) activity. The DBT HDS assessment results also revealed that the catalyst containing 17.7 wt% WO3 and 2.4 wt% NiO prepared by the hydrothermal deposition method had the similar DBT HDS activity as a commercial NiW/γ-Al2O3 catalyst containing 23 wt% WO3 and 2.6 wt% NiO, resulting in the greatly decreased amount of active metals for achieving the same HDS activity.

This article describes a novel modification method consisting of steaming and subsequent citric acid leaching to finely tune acidity and pore structure of HZSM-5 zeolite and thereby to enhance the on-stream stability of the zeolite derived fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst. A series of dealuminated HZSM-5 zeolites and their derived catalysts were prepared and characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), 27Al MAS NMR, nitrogen adsorption, temperature programmed desorption of ammonium (NH3-TPD) and infrared (IR) spectroscopy of chemisorbed pyridine. The results showed that the citric acid leaching could preferentially remove the extra-framework Al (EFAl) species formed by steaming treatment and thus reopen the EFAl-blocked pore channels of the steamed zeolite. The steaming treatment at a suitable temperature and subsequent citric acid leaching not only decreased the strength of acid sites to a desirable degree but also increased the ratio of medium and strong Lewis acidity to medium and strong Brönsted acidity, both of which conferred the resulting catalyst with superior selectivity to aromatics, good hydroisomerization activity and gasoline research octane number (RON) preservability, as well as enhanced on-stream stability. The results fully demonstrated that the treatments by steaming and followed citric acid leaching can serve as an important method for adjusting the physicochemical properties of HZSM-5 zeolite.

This article describes a novel non-hydrogenating FCC gasoline upgrading catalyst system consisting of a kaolin/γ-Al2O3 binary-matrix and an active component zeolite HZSM-5. Different catalysts made from the different combinations of HZSM-5 with the three matrices (two kaolins and γ-Al2O3) or their binary mixtures were prepared and their catalytic performances were assessed in a continuously flowing fixed-bed reactor using FCC gasoline as feedstock. The results showed that compared with the single-matrix based HZSM-5 catalysts, the binary-matrix based HZSM-5 catalysts had much better catalytic performance. The characterization results of the acidity, specific area and pore structure properties of the catalysts revealed that the synergisms between the matrices and HZSM-5 in the acidity and pore distribution of the binary-matrix based catalysts accounted for their improved catalytic performance. Our results demonstrated that the non-hydrogenating catalyst system developed in the present investigation can convert olefins in FCC gasoline into aromatics that have higher research octane number (RON) and thus has potential application for FCC gasoline upgrading because of its excellent olefin reduction ability and RON preservability.

Two W/γ-Al2O3 catalysts were prepared by a surfactant-assisted hydrothermal deposition method developed in the present investigation and the conventional impregnation method, respectively, and characterized by means of XRD, XPS, TEM, N2 adsorptipn, NH3-TPD and H2-TPR. The results showed that compared with the catalyst prepared by impregnation, the catalyst prepared by the surfactant (cetyltrimethylammonium bromide, CTABr)-assisted hydrothermal deposition had higher dispersion of tungsten species with weak metal–support interaction, more open pore channels, and more acid sites, and thus presented a significantly enhanced hydrodenitrogenation activity. The novel method introduced here sheds a light on preparing supported metal catalysts with high activity.

•We controllably prepared supported catalysts with various pore sizes and structures.•The precursors are newly-proposed Mo-based organic–inorganic hybrid nanocrystals.•We confirmed the close relationship between the catalyst structure and performance.•The structure with 3D open pore channels is favorable for the reaction activity.A series of mesoporous sieves with different pore diameters and structures have been controllably synthesized by adding variable amounts of swelling agent 1,3,5-trimethylbenzene in the preparation process for SBA-15. NiMo catalysts supported by mesoporous sieves are prepared by using the newly proposed Mo-based organic–inorganic hybrid nanocrystals as precursors to load Mo and subsequently using wetness impregnation to load Ni. The hydrodesulfurization (HDS) activity of these obtained catalysts is evaluated in a continuously flowing tubular fixed-bed microreactor using 1 wt% dibenzothiophene (DBT) in heptane as a model compound. The results show that HDS ratio has gradually increased as the pore diameter of supports is enlarged from 7 to 11 nm with the mesostructure keeping an ordered two-dimensional hexagonal symmetry. When the structure is in the intermediate stage of structural transition from ordered hexagonal mesostructure to mesocecullar structure, HDS ratio is decreased dramatically due to the disordered and collapsed structure to block the pore channels. After the mesocecullar structure with three-dimensional open pore channels is formed which is more convenient for the molecular diffusion, HDS ratio has increased again as a result. It is concluded that both the pore size and window size connecting the adjacent pores play an important role in the HDS activity but the window size is of more significant importance, which is the key point for the enhanced catalytic performance.Download high-res image (147KB)Download full-size image

An oxalic acid-assisted hydrothermal deposition method to prepare highly dispersed W/γ-Al2O3 and NiW/γ-Al2O3 hydrodesulfurization catalysts without strengthening the metal–support interaction was developed and compared with the conventional impregnation method. The resulting oxidic and sulfided catalysts were characterized, and their catalytic performance was assessed. The results showed that the oxalic acid-assisted hydrothermal deposition method can better disperse tungsten oxide on γ-Al2O3 while decreasing the metal–support interaction, resulting in more efficient sulfidation of tungsten oxide and formation of highly stacked WS2 slabs with short length, and thereby the significantly enhanced hydrodesulfurization activity of the resulting catalysts. The improved dispersion of W species is attributed to the anti-aggregation effect of the oxalic acid adsorbed on active metal particles formed during the hydrothermal deposition process, whereas the strong interaction between carboxyl groups of oxalic acid and hydroxyl groups or unsaturated Al3+ on alumina surface accounts for the weakened metal–support interaction.

Hydrothermally stable composite materials with hierarchical macro–meso–micro-porous structure were successfully synthesized via in situ assembly of preformed zeolite Y nanoclusters on kaolin using cetyltrimethylammonium bromide as template under alkaline conditions. The characterization results show that the mesophase in the composite contains primary and secondary structural building units of zeolite Y. The building units contribute micropores in the composite with acidity similar to that of zeolite Y, whereas the macroporous kaolin substrate contributes macropores. This hierarchical macro–meso–micro-porous structure increases the accessibility of the active sites in the composite to reactants and thus confers superior catalytic performance on the resulting catalyst in cracking heavy crude oil. The present work demonstrates that the in situ assembly of zeolitic nanoclusters on substrates (e.g., kaolin) can provide a novel route for fabricating composite materials with hierarchical pore structure.

This article presents a novel method for preparing NiW/USY–Al2O3 ultradeep hydrodesulfurization (HDS) catalysts via combined citric acid-assisted hydrothermal dispersion of active metals and hydrothermal modification of HY zeolite. The results showed that the citric acid-assisted hydrothermal method yielded monomeric W species as W precursors that were well dispersed by the interaction between citric acid and WO3 particles and were suitably stacked by the preferential interaction between citric acid and the support, guaranteeing a compromised dispersion and stacking of the supported Ni–W–S phases. The citric acid-assisted hydrothermal modification combined the framework dealumination of the HY zeolite and the removal of nonframework Al species, exposing more Brønsted acid sites on the catalyst. The finely tuned morphology of the Ni–W–S phases and the suitably adjusted Brønsted acidity of the zeolite endowed the resulting NiW/USY–Al2O3 catalyst with outstanding hydrogenation and hydrogenolysis activities for 4,6-dimethyldibenzothiophene and coking diesel HDS.Graphical abstractA novel method for coupling the citric acid-assisted hydrothermal dispersion of active metals and the hydrothermal modification of HY zeolite was proposed, which endows the resulting NiW/USY–Al2O3 catalyst with outstanding hydrogenation and hydrogenolysis activities for hydrodesulfurizing 4,6-DMDBT.Download high-res image (139KB)Download full-size imageResearch highlights► Citric acid-assisted hydrothermal system enhances the dispersion of active metals. ► This hydrothermal system finely tunes the acidity and pore structure of HY zeolite. ► These two effects endow the catalyst with outstanding hydrodesulfurization activity.

Mono-dispersed Mo-based inorganic–organic hybrid nanocrystals (HNCs) in water phase with a uniform size of ca. 3 nm have been successfully synthesized via a simple and facile method at room temperature. With the help of comprehensive characterizations, the chemical composition and structure of this hybrid material was determined: Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. Interestingly, the resultant nanocrystals can spontaneously self-assemble into lamellar mesoscale nanocomposites with an alternative arrangement of inorganic and organic layers when simply removing water or adding ethanol into the solution. The distance between two layers depends on the length of the quaternary ammonium cations used, indicating that the cationic surfactant functions as a structure-directing agent and induces the formation of an ordered lamellar mesostructure. Moreover, we found that the lamellar mesoscale structure can be disassembled into well-dispersed HNCs when being re-dispersed into a large amount of water. The unique self-assembly and disassembly behavior of the mono-dispersed HNCs may have great potential for fabricating Mo-based functional materials.

This article presents a novel strategy to prepare alumina-supported Mo and MoNi hydrodesulfurization (HDS) catalysts using Mo-based inorganic–organic hybrid nanocrystals (HNCs) as a superior precursor under moderate hydrothermal conditions. The characterization results revealed that each HNC in the aqueous solution has a size of ca. 2.5 nm and shows a core–shell structure with one Mo8O264− as the inorganic core and long-chain quaternary ammonium cations as the organic shell. The proposed approach not only significantly promotes the dispersion of supported Mo species, but also greatly enhances the stacking of MoS2 active phase, endowing the resulting catalysts with sufficient and accessible Ni–Mo–S active sites and thereby with a remarkably enhanced HDS performance as compared to their counterparts prepared by the conventional impregnation method. Thereby, a novel precursor for preparing Mo-based catalysts was successfully developed and the roles of the HNC-derived preparation method in tuning the size and morphology of supported metal sulfide nanoparticles in HDS catalysts were demonstrated, shedding a light on the rational design and controllable fabrication of supported metal sulfide catalysts.

Silica hollow microspheres (SHMs) with size-tunable penetrating macropores from 250 nm to 560 nm are prepared by a water/oil/water ternary phase emulsion system. Furthermore, the thus-obtained SHMs can serve as a superior support to fabricate supported palladium catalysts for the hydrogenation of bulky polystyrene molecules.