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A facile strategy for the synthesis of a high quality TS-1 zeolite without anatase Ti species via a hydrothermal method using urea as a mineralizer was reported, which exhibits excellent performance in the direct gas phase epoxidation of propylene.

Effects of different Ni site location on the Ni-based catalysts were investigated in the ethylene oligomerization.

Liquid organic hydrogen carrier (LOHC) has attracted a great deal of attention in recent years for its use in hydrogen storage. Supported Rh catalyst has been widely used in the hydrogenation react...

Significant progresses have been made in the performance of homogeneous catalysts in the oligomerization of 1-decene to polyalphaolefin (PAO), whereas it remains a big challenge to design heterogeneous catalysts with high catalytic activity in the PAO synthesis. Herein, a series of heterogeneous mesoporous catalysts with different acidity were successfully synthesized by the in situ incorporation of Al in the channels of mesoporous silica under room temperature and atmospheric pressure. These samples were characterized by various techniques including XRD (X-ray diffraction), SEM (scanning electron microscopy), TEM (transmission electron microscopy), BET (N2 adsorption–desorption analyses), Py-IR (pyridine-adsorbed IR) and XPS (X-ray photoelectron spectroscopy). The obtained samples exhibit a high surface area, high ordering, and controllable Bronsted and Lewis acid sites. The results indicated that the increasing acidity promotes oligomer selectivity, especially for the trimer (C30). The resulting heterogeneous catalyst exhibited excellent performance with high conversion (70.7%) and high oligomer selectivity (96.7%) due to the suitable acid sites. Moreover, the spent heterogeneous catalyst could be regenerated and its catalytic activity maintained after five cycles.

Gamma-ray (gamma-ray) irradiation was introduced into zeolite synthesis. The crystallization process of zeolite NaA, NaY, Silicalite-1, and ZSM-5 were greatly accelerated. The crystallization time of NaA zeolite was significantly decreased to 18 h under gamma-ray irradiation at 20 degrees C, while more than 102 h was needed for the conventional process. Unexpectedly, more mesopores were created during this process, and thus the adsorption capacity of CO2 increased by 6-fold compared to the NaA prepared without gamma-ray irradiation. Solid experimental evidence and density function theory (DFT) calculations demonstrated that hydroxyl free radicals (OH*) generated by gamma-rays accelerated the crystallization of zeolite NaA. Besides NaA, mesoporous ZSM-5 with MFI topology was also successfully synthesized under gamma-ray irradiation, which possessed excellent catalytic performance for methanol conversion, suggesting the universality of this new synthetic strategy for various zeolites.

A novel melting-assisted solvent-free route using solid oxalic acid was proposed for the post-treatment of SAPO-11 zeolite, followed by loading with 0.5 wt% Pt by the incipient wetness impregnation method. Subsequently, the performance of the obtained bifunctional catalysts toward the hydroisomerization of n-dodecane was examined. The prepared samples were characterized by XRD, SEM, BET, XRF, Py-IR, and solid-state NMR. From the results, it was found that the high crystallinity and uniform morphology were retained after the post-treatment and that more (002) crystal faces were exposed, which was beneficial since more acid sites were provided. More importantly, the total Bronsted acid sites and the ratio (Ra) of the micropore area to the total surface area were optimized by this method. Thus, the catalytic performance was enhanced significantly, and the prepared Pt-SAPO-11-10% catalyst had the highest i-dodecane yield of 80.1% compared to 55.3% of Pt–SAPO-11. Expectedly, this facile and cost-effective method is promising for the hydroisomerization of normal paraffin in the production of lubricant base oils.

The SAPO-11 zeolite is widely used in the hydroisomerization of n-paraffins due to its unique shape selectivity, and the particle size plays an important role in the catalytic performance. Herein, multi-scale SAPO-11 zeolites with different particle sizes (65 nm to 4.5 μm) are successfully synthesized via a modified dry-gel conversion method by controlling the nucleation rate and the growth rate of the crystal. The resulting samples were characterized by XRD, SEM, N2 adsorption desorption, NH3-TPD, Py-IR and 29Si MAS NMR. These solid results indicate that the change in particle size of SAPO-11 has a large effect on its structure and acidity. Furthermore, the n-dodecane hydroisomerization reaction was investigated in this work, and the experimental results show that the prepared bifunctional Pt/SAPO-11-10% catalyst has the highest iso-dodecane yield (70.9%) with a conversion of 93.5% among all the samples, which could be ascribed to the synergistic effect between the suitable particle size and acid sites, which enhanced its catalytic performance.

Lubricating oil is one of the important types of petrochemical products widely used in industry. However, traditional petroleum-based lubricants, which are associated with exhausting fossil resources, pose a great hazard to the environment owing to their non-degradability. Castor oil, as a type of vegetable oil, is a promising candidate to replace mineral oil to alleviate energy stress and protect the environment. Herein, we report a novel strategy for developing a non-noble metal catalyst for the oligomerization of methyllinoleate to directly produce bio-lubricant oil. The obtained dimers and higher oligomers of methyllinoleate were produced with a high conversion of 99.9% and a maximum yield of 70.8% using a molybdenum-containing silica–alumina catalyst under optimised conditions. The superior activity was attributed to the highly dispersed MoO3 nanoparticles on the surface of the silica–alumina support. The polymerization mechanism of the Mo-based catalyst for this eco-friendly oligomerization process was proposed and verified using density functional theory (DFT) calculations to provide a better understanding of the catalytic mechanism.

Single-crystalline zeolites are highly desirable in this field owing to their high hydrothermal stability and high mass transfer efficiency. However, the preparation of single-crystalline silicoaluminophosphate SAPO-11 zeolite remains a significant challenge due to its complex synthesis process. Herein, we firstly report a facile and direct approach to synthesize single-crystalline SAPO-11 by interzeolite transformation via a kinetic-modulated process. The crystallization process of single-crystalline SAPO-11 was monitored by the time-dependent characterizations. A panel of characterizations by XRD, SEM, N2-adsorption and solid-state NMR provided evidence that the formation mechanism of single-crystalline SAPO-11 involved fast interzeolite transition process between two different topologies from AlPO4-8 (AET) to SAPO-11(AEL), thus it avoids the aggregation of small nanocrystals during the conventional polycrystalline SAPO-11 synthesis. In addition, the Bronsted acid sites of the prepared samples could be precisely regulated. The resulting single-crystalline catalyst exhibits superior isomer selectivity (92.3% vs. 70.6%) and yield (77.9% vs. 62.3%) in the n-dodecane hydroisomerization compared with the conventional polycrystalline sample due to the unique morphology and suitable acidity. This synthetic strategy provides a new orientation to design other single-crystalline zeolite catalysts.

SAPO-34 zeolite with a butterfly patterned hierarchical pore system and high relative crystallinity was synthesized by a melting-assisted solvent-free route. Oxalic acid in the solid state was used as the etching agent through a facile thermal treatment of the parent SAPO-34. The resultant zeolite exhibited complete methanol conversion, high C2=–C4= selectivity (>91%) and a long lifetime in the MTO process.

Acidity controlled Pt/ZSM-22 catalysts for n-dodecane hydroisomerization were explored through a simple and efficient post-treatment with different NaOH concentrations, and then the resulting samples were characterized using acid measurement, XRD, SEM, TEM, XRF and XPS. It appeared that the high crystallinity, uniform morphology and textural structure almost remained even after the alkaline-treatment of the parent zeolite with a low Si/Al ratio (∼20). However, the distribution of acid sites, and in particular the Bronsted acidity, changed which then affected the catalytic performance. This originates from the Bronsted acid sites of the parent catalyst being partially blocked. With the acid sites optimized using the alkali treatment, the selectivity for isomers increased from 59.5% (parent sample) to 87.3% (treated sample) with the yield increasing from 43.3% to 69.8%. Thus, such an ordinary alkaline treatment proved to be promising in the n-paraffin hydroisomerization for the cleaner production of lubricating oil based stocks.

Hydrogen is a promising candidate to replace the exhausting fossil fuels. However, it is still a big challenge for hydrogen storage. Liquid organic hydrogen carrier (LOHC), which possesses high safety and purity, easy transport and reversibility, is highly attractive for hydrogen storage. Herein we report a new reusable bimetallic Pd-Rh nanoparticles (NPs) catalyst with synergy effect, boosting both the hydrogenation of N-ethylcarbazole (NEC) and dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NEC), which allows multiple cycles of reversible high-weight% hydrogen storage and uptake in short reaction time. Various ex- and in-situ characterizations evidenced that the superior activity was attributed to the bimetallic Pd-Rh NPs cluster structure on the surface of γ-Al2O3 support. The mechanism of NEC hydrogenation over the Pd-Rh catalyst was proposed and verified by density functional theory (DFT) calculations. Such a strategy can be extended to other LOHCs and sheds light onto the development of LOHCs as energy vectors.

Direct conversion of carbon dioxide (CO2) into lower olefins (C2=–C4=), generally referring to ethylene, propylene, and butylene, is highly attractive as a sustainable production route for its great significance in greenhouse gas control and fossil fuel substitution, but such a route always tends to be low in selectivity toward olefins. Here we present a bifunctional catalysis process that offers C2=–C4= selectivity as high as 80% and C2–C4 selectivity around 93% at more than 35% CO2 conversion. This is achieved by a bifunctional catalyst composed of indium–zirconium composite oxide and SAPO-34 zeolite, which is responsible for CO2 activation and selective C–C coupling, respectively. We demonstrate that both the precise control of oxygen vacancies on the oxide surface and the integration manner of the components are crucial in the direct production of lower olefins from CO2 hydrogenation. No obvious deactivation is observed over 150 h, indicating a promising potential for industrial application.

Although considerable progress has been made in carbon dioxide (CO2) hydrogenation to various C1 chemicals, it is still a great challenge to synthesize value-added products with two or more carbons, such as gasoline, directly from CO2 because of the extreme inertness of CO2 and a high C-C coupling barrier. Here we present a bifunctional catalyst composed of reducible indium oxides (In2O3) and zeolites that yields a high selectivity to gasoline-range hydrocarbons (78.6%) with a very low methane selectivity (1%). The oxygen vacancies on the In2O3 surfaces activate CO2 and hydrogen to form methanol, and C-C coupling subsequently occurs inside zeolite pores to produce gasoline-range hydrocarbons with a high octane number. The proximity of these two components plays a crucial role in suppressing the undesired reverse water gas shift reaction and giving a high selectivity for gasoline-range hydrocarbons. Moreover, the pellet catalyst exhibits a much better performance during an industry-relevant test, which suggests promising prospects for industrial applications.

ZSM-5 crystals with controllable c-axis length were successfully synthesized through a one-pot solvent-free route, with urea as an additive. X-ray diffraction patterns (XRD) show that the prepared samples exhibit high crystallinity. N2 adsorption–desorption isotherms and mercury intrusion porosimetry (MIP) analysis together with TEM observations indicate that micro-, meso-, and macropores exist in the obtained samples. Catalytic tests for the methanol to gasoline (MTG) conversion showed that the prepared c-axis oriented hierarchical ZSM-5, which allow fast mass transfer, exhibited both 100 % methanol conversion and far longer lifetime (900 h) than those of ZSM-5 with conventional morphology (350 h) in the MTG reaction. The enhanced MTG performance by the c-axis oriented zeolite under one-pot solvent-free synthesis is of great importance as it is easily scaled-up for industrial applications.

Fast deactivation of catalyst is the main problem in methanol-to-aromatics (MTA) process. Herein, Zn-containing HZSM-5 zeolites with hierarchical pores (H-Zn/HZSM-5) were prepared by treating directly synthesized Zn/HZSM-5 with NaOH solution. The changes in crystallinity, acidity and textural properties of Zn/HZSM-5 before and after alkali treatment were characterized by X-ray diffraction, NH3-TPD, 27Al MAS-NMR, N2 physisorption, X-ray fluorescence and TEM techniques. MTA reaction under the operating conditions of T = 400 °C and WHSV = 2.5 h−1 showed that the aromatic yield was improved from 41.4% for HZSM-5 to 55.3%. Furthermore, H-Zn/HZSM-5 exhibited a high initial space time yield of 0.62 g gcat−1 h−1 and a long lifetime up to 120 h. These results could be ascribed to the hierarchical pores and the providential acidity, which enhanced the adsorption and diffusion of intermediates/products during the reaction.

H-type aluminosilicate zeolites are extensively used as solid-acid catalysts and support materials in industrial catalysis. However, the conventional synthesis methods involving hydrothermal syntheses and ion-exchange processes suffer from severe water pollution and toxic gas emissions. Herein, H-type MFI zeolite catalysts with a unique stacked structure were directly synthesized in the presence of NH4F and with the help of zeolite confinement through a solvent-free route without further ion-exchange procedures. A range of ex situ and in situ characterization procedures were used to provide evidence of the simultaneous use of pre-made ZSM-5 and NH4F as a confined Al source and mineralizer, respectively. The confined zeolite framework of ZSM-5 prevented the formation of AlFx species between NH4F and Al atoms, ensuring that the prepared samples had desirable acidic properties. Moreover, the resulting morphology could be controlled by using different silica substrates. The obtained H-type MFI zeolites showed excellent catalytic performance in methanol-to-gasoline reactions owing to their unique structure and directly exposed acidic sites. The developed one-pot strategy provides an alternative method for the facile synthesis of H-type zeolites with defined morphology.

A hierarchical ZSM-5 zeolite with high crystallinity, high surface area, adjustable Si/Al ratio and suitable acidic properties was synthesized by a one-pot solvent-free method. The resultant zeolite exhibited complete methanol conversion, high C5+ selectivity (>60%) and a long lifetime (350 h) in the MTG process.

Impacts of K promoter on microstructures of a precipitated Cu–Fe based catalyst were studied by N2-physisorption (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD) and hydrogen temperature-programmed desorption/reduction (H2-TPD/TPR). Mixed alcohols synthesis (MAS) was carried out in a fixed-bed reactor. The results indicated that incorporation of K in the Cu–Fe based catalyst decreased the surface area of the particles, whereas promoted the immigration of bulky iron species to surface layers and strengthened the interaction of surface Fe–Cu. The increase of K concentration weakened the H2 chemisorption and restrained the reduction of both the Cu and Fe species. The catalytic activity and mixed alcohols selectivity increased accompanied with a gradually increasing K concentration, and reached the highest values as the amount of K increased to 0.5 wt.%. Subsequently, the MAS activity and selectivity C 2 + OH presented a decreasing trend. In addition, the increase of K concentration facilitated the formation of heavy hydrocarbons.

SAPO-34 molecular sieves with different crystal morphologies were synthesized under microwave conditions. The type of organic templates, crystallization time and temperature were optimized to control the synthesis. These SAPO-34 samples were characterized by XRD, SEM, EDX, TG, nitrogen adsorption–desorption, NH3-TPD and solid state MAS NMR techniques. It was found that the crystallization conditions greatly affected the crystal morphology, textural data, Si incorporation and acidity of SAPO-34. Pure SAPO-34 with uniform sphere particles of 20 nm was obtained after crystallization at 165 °C for 0.75 h under microwave conditions using TEAOH as the template. Raising the temperature to 220 °C and prolonging the crystallization time to 2 h led to the formation of nano sheet-like SAPO-34 with a BET surface area of 593 m2/g. NH3-TPD profiles showed that low crystallization temperature and short crystallization time resulted in fewer weak acid sites and strong acid sites, while higher crystallization temperature and longer crystallization time increased the amount of both acid sites, which may benefit the methanol to olefins (MTO) reaction. The nano sheet-like SAPO-34 exhibited 100 % methanol conversion for 380 min during the MTO process, an ethylene selectivity of 51.77 % and a C 2 = –C 4 = selectivity of 90.20 %. The result was much better than that of the sample with a larger cubic morphology of 1.5–2.5 μm synthesized under hydrothermal conditions, on which the 100 % methanol conversion could only be kept for 212 min as well as an ethylene selectivity of 49.84 % and a C 2 = –C 4 = selectivity of 86.81 %. The unique morphology of the nano sheet-like SAPO-34 decreased its coke formation rate, which might be responsible for its improved catalytic performance.

SAPO-34 molecular sieve samples with sheet-like and cubic morphology were synthesized under microwave and hydrothermal conditions, respectively. The sheet-like SAPO-34 was 130 nm thick with a Brunauer-Emmett-Teller (BET) surface area of 593 m2/g, while the cubic sample was 1.5–2.5 μm in size with a BET surface area of 708 m2/g. Both samples exhibited a similar density for strong acid sites, while the cubic SAPO-34 possessed less weak acid sites. A methanol to olefins catalytic test carried out at 450 °C and 1.0 h−1 showed that the sheet-like SAPO-34 exhibited a long stability life of 380 min and gave a high ethylene selectivity of 51.77% and a high total selectivity for ethylene, propylene, and butylene of 90.20%. However, the stability life for the cubic SAPO-34 was only 212 min, and the ethylene selectivity and total selectivity for ethylene, propylene, and butylene decreased to 49.84% and 86.81%, respectively. It is thought that the longer stability life and higher olefin selectivity for sheet-like SAPO-34 occur because of the shorter diffusion path that hinders the further conversion of produced olefins and coke formation.

Effect of manganese promoter on the microstructures of co-precipitated Fe-Cu catalysts was investigated by N-2 physisorption, X-ray diffraction (XRD), and temperature-programmed reduction/desorption of hydrogen (H-2-TPR/TPD). Higher alcohols synthesis (HAS) was performed in a fixed bed reactor. The characterization results indicated that incorporation of manganese into the Fe-Cu based catalysts facilitated the formation of Fe-Mn-O solid solution and promoted the dispersion of both the iron and copper species. In the HAS reaction, the catalytic activity of CO hydrogenation, selectivity of C-2(+) OH and hydrocarbons increased gradually with increasing Mn concentration, which may be attributed to the well dispersion of both the iron and copper surface active sites in higher manganese content. The optimum conditions for producing higher alcohols from syngas were determined as 270 degrees C and 6.0 MPa. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.

Effect of iron promoter on the microstructures of CuMnZnO catalysts was investigated by N2 physical adsorption (BET), X-ray diffraction (XRD), and temperature-programmed reduction of hydrogen (H2-TPR). Higher alcohols synthesis (HAS) was performed in a fixed bed reactor. The characterization results indicated that incorporation of iron in the CuMnZnO catalyst resulted in the increase of BET surface area and the dispersion of catalyst particles. Adding iron facilitated the formation of Fe–Mn solid solution and reduced the interaction between copper and manganese, which promoted the separation of CuO from the Cu–Mn solid solution and the reduction of the catalyst. In the HAS reaction, the catalytic activity of CO hydrogenation and the selectivity to C 2 + OH and hydrocarbons presented an increasing trend with the increase in iron concentration, which may be attributed to the synergistic effect between the dispersed copper and iron carbides.

The effect of Ni/Mg mole ratio of Ni–MgO/γ-Al2O3 cordierite monolithic catalysts on dry reforming of model biomass fuel gas(H2/CO/C2H4/CH4/CO2/N2 = 16.0/12.1/2.5/15.1/22.0/32.3, vol.%) was investigated in a lab-scale stainless steel tubular reactor. The results showed that CH4 and CO2 conversions, H2 and CO yields and H2/CO ratio in the tail gas was 87.2%, 54.4%, 65.2%, 43.0%, and 1.17 respectively at 750 °C over the optimized MCNi0.51Mg0.49O (the ratio was 0.51:0.49 with 8.3 wt% NiO loading amount) during 60 h of time on stream (TOS). And the formation of NiO–MgO solid solution structure would restrain the active Ni0 centers from agglomeration and decrease carbon deposition. Cold test of the vertical-placed tubular reformers (packed by monolith of 7 mm cell spacing) indicated that the pressure drop was as low as 850 Pa at 1.57 m/s of gas velocity with 330 g/m3 fly ash added. The reforming of real biomass fuel gas (H2/CO/C2H4/CH4/CO2/N2 = 10.2/16.8/0.5/6.4/15.2/51.0, vol.%, from air gasification of 200–250 kg/h pine sawdust in the pilot plant) in the multi-tube reformer packed with MCP (larger in size than MCNi0.51Mg0.49O) exhibits the pressure drop of less than 700 Pa, CH4 and CO2 conversions of about 84% and 38.5% and the decrease of tar content from 4.8–5.3 g/m3 to 0.12–0.14 g/m3 during 60 h TOS at 670 °C. The characterization of the spent catalysts by TG, XRD and ICP-AES proved the anti-sintering and anti-carbon deposition properties of NiO–MgO solid solution monolithic catalyst.