•Hierarchical ZSM-5 was obtained by the treatment of HF and NH4F.•Both framework Si and Al were indiscriminately extracted from ZSM-5 zeolite.•The catalyst showed excellent catalytic performance in the reaction of MTG.Chemical etching with fluoride ions is a new approach for secondary porosity engineering of aluminosilicate zeolite frameworks. This work shows that the mixture of HF and NH4F extracted indiscriminately both framework Si and Al from ZSM-5 zeolite. After the treatment, the relative crystallinity decreased slightly; the external surface areas and mesopore volumes increased, but the micropore surface areas and volumes and the acidity of the obtained hierarchical ZSM-5 did not change appreciably. When the hierarchical materials were applied in the reaction of methanol to gasoline (MTG), the catalyst lifetime was prolonged significantly with the liquid hydrocarbon selectivity improved slightly. The results can be ascribed to the improved transport through the crystals coupled with the retained zeolite acidity.Liquid hydrocarbons (LH) yields over the parent and HF-NH4F-treated ZSM-5. Reaction conditions: 400 °C, 1 atm, WHSV = 10 h−1.Download high-res image (90KB)Download full-size image

•Few ZSM-5 phases were detected by the synthesis with calcined MFI zeolite as seeds.•Pure ZSM-5 zeolites were synthesized by calcined MFI seeds in the presence of CTAB.•Aggregates of nano ZSM-5 crystals were obtained by dissolving bulk ZSM-5 seeds.•Hierarchical aggregates showed great enhance in methanol to propylene reaction.A seed-induced method was developed to synthesize aggregates of nano-sized ZSM-5 crystals by template-free MFI seeds and cetyltrimethyl ammonium bromide (CTAB). Various MFI zeolites after calcination, including: nano-sized silicate-1, nano-sized ZSM-5 aggregates and commercial bulk ZSM-5 crystals were used as seeds. A trace of CTAB could accelerate the crystallization and pure MFI structure was obtained in the presence of CTAB. More importantly, the aggregates of nano-sized ZSM-5 crystals were dramatically synthesized by transforming the bulk seeds into smaller sizes with NaOH treatment before crystallization. The resulting solid exhibited an excellent catalytic performance in the methanol to propylene reaction.Catalytic performance was greatly improved by the seed-induced method with the bulk crystal seeds after alkali treatment.Download high-res image (97KB)Download full-size image

A seed-induced method was applied to synthesize a series of ZSM-5 aggregates using silicalite-1 (S-1) as seeds. The samples were characterized by several techniques and studied in the methanol-to-gasoline (MTG) conversion reaction in a continuous fixed-bed reactor. The results showed that the molar ratios of Na2O/SiO2 and H2O/SiO2 in the precursors had great effects on the physicochemical and catalytic properties. The ZSM-5 aggregates with the highest crystallinity, external surface areas, micropore volumes, mesopore volumes and small primary crystal and aggregate sizes, obtained with the molar composition of 0.12Na2O–1SiO2–0.02Al2O3–25H2O-0.01Seed in the precursor, exhibited the highest stability.

A hierarchical ZSM-11/5 composite zeolite with a high SiO2/Al2O3 ratio was successfully synthesized using a seed-induced method in the presence of cetyltrimethylammonium bromide, characterized by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, 27Al NMR, 27Si NMR, N2 physical adsorption, and temperature-programmed desorption of ammonia, and studied in the frame of the methanol-to-olefins reaction. The results show that the amount of seed added plays a pivotal role in the formation of hierarchical ZSM-11/5 composite zeolite. With an increase in the amount of seed, the composite zeolite exhibits excellent catalytic performance in the methanol-to-olefins reaction, which can be attributed to the higher specific surface areas, higher external surface areas, more mesopore volumes, and more acid sites than ZSM-11 synthesized by the conventional method with tetrabutylammonium ions as a template. Contrary to the conventional point of view, the addition of too much seeds results in a dramatic decrease in the catalytic performance, which is ascribed to the higher proportion of ZSM-5 in the ZSM-11/5 composite zeolite.

SAPO-34, a silicoaluminophosphate zeolite, has been synthesized by the hydrothermal method with the addition of different molecular weights of polyethylene glycol (PEG), and has been characterized with XRD, SEM, N2 adsorption–desorption, FT-IR, and NH3 temperature-programmed desorption (NH3-TPD). We studied SAPO-34 as a catalyst in the methanol-to-olefins (MTO) reaction, in a fixed-bed reactor. The results show that the chain length of PEG has a great influence on the particle size and morphology of SAPO-34. PEG acts as inhibitor in the crystallization process. With the increase of the chain length of PEG used in the synthesis, from a relative molecular weight of 400–6000, the morphology of SAPO-34 changes gradually from cubic to nanoplate-like and then changes to cubic again. The particle size decreases markedly at first and then increases to some extent. The catalytic stability in the MTO reaction also increases first and then decreases, with all the catalysts having almost the same selectivity to olefins. When the sample is synthesized with PEG800, the particles become nanoplate-like with a thickness of 46 nm on average, and the catalytic stability is appreciably prolonged, which is attributed to the shorter diffusion paths of the reactants in the zeolite.

Titanium silicalite (TS-1) without and with extra-framework titanium have been prepared and TiO2 is also prepared under the same conditions. All the samples are characterized with XRD, FT-IR, and UV–Vis. The effects of extra-framework titanium in TS-1 on the ammoximation of cyclohexanone have been studied in a continuous slurry reactor. The characterization results reveal that the extra-framework titanium exists as anatase. The catalytic evaluation results show that the anatase has a positive effect on the ammoximation of cyclohexanone by extending the catalytic life because it also exhibits some activity, while the conversion of cyclohexanone and the selectivity to cyclohexanone oxime are not influenced. The anatase TiO2 does not catalyze H2O2 decomposition appreciably compared with TS-1 without extra-framework titanium. The results are very useful in guiding the TS-1 production.

ZSM-5 zeolite prepared by a hydrothermal method with the addition of seeds was treated with different concentrations of NaOH. The obtained samples were characterized by XRD, N2 adsorption, NH3-TPD, FT-IR, SEM, and studied in the catalytic performance of the hydration of cyclohexene to cyclohexanol. The characterization results showed that with the increase of NaOH concentration, the crystallinity of the treated samples decreased monotonously, and the acid sites of ZSM-5 zeolites first increased and then decreased, while more mesopores formed inside the ZSM-5 zeolites. The experimental results of catalytic performance showed that cyclohexene conversion can be improved through introducing the mesopores and enhancing the acidity of ZSM-5 with the NaOH treatment at a low concentration. The highest cyclohexene conversion of 12.8% was obtained when the concentrations of NaOH solution were in the range of 0.2–0.6 mol/L. The selectivity of cyclohexanol on all samples was higher than 99.6%.

Hollow ZSM-11 was successfully prepared through post-treatment with tetrabutylammonium hydroxide (TBAOH). The products were characterized by XRD, TEM, ICP-OES, 27Al NMR, 27Si NMR, N2 physical adsorption and NH3-TPD and studied as catalysts for the reaction of methanol to hydrocarbons. The characterization results showed that the hollowness might be formed through a dissolution–recrystallization process. The hollow ZSM-11 zeolite showed higher specific surface areas, higher external surface areas, higher mesopore volumes and more acid sites than the untreated ZSM-11, and exhibited excellent catalytic properties in the reaction of methanol to hydrocarbons.

Zeolite ZSM-5 (SiO2/Al2O3 = 50) has been treated with hydrofluoric acid (HF) solutions, characterized with many techniques and studied in the conversion of methanol to gasoline (MTG). After the HF treatment, the crystallinity of the zeolite is retained; mesopores are generated and the mesopore volumes increase with the HF concentration; the SiO2/Al2O3 ratios increase; the acidities of the samples and the Brönsted acid sites decrease, while the Lewis acid sites increase with the HF concentration. Aluminum from the framework was removed to an extent by the treatment. With increasing the concentrations of HF solution in the treatment, the stabilities of the ZSM-5 samples improve significantly in MTG. The results demonstrate that the acidity and the pore structure are two crucial factors in determining the catalytic properties.

Activated carbon (AC) supported CuCl (CuCl/AC) has been prepared with CuCl2 as precursor by a monolayer dispersion method. The samples are investigated for CO adsorption and characterized by inductively coupled plasma optical emission spectrometry, X-ray diffraction, N2 adsorption/desorption and X-ray photoelectron spectroscopy. The characterization results reveal that CuCl2 supported on AC can be completely converted to CuCl after activation at 543 K in N2. The resulting adsorbent displays high CO adsorption capacity, high CO/N2, CO/CH4 and CO/CO2 adsorption selectivities and excellent reversibility, and the adsorption equilibrium isotherms of CO on the adsorbents at temperatures up to 333 K can be well fitted by both the Langmuir and Sips models.

A facile and economical route to synthesize nano-sized ZSM-5 zeolite aggregates with mesopores was developed by a modified seed-induced method using silicate-1 (S-1) as seeds without additional templates in the presence of a trace amount of cetyltrimethylammonium bromide (CTAB). The effect of the amounts of CTAB and S-1 on the morphologies and textural properties were studied in detail, and the possible formation mechanism was proposed. The primary crystal sizes of the ZSM-5 zeolites could be adjusted and mesopores were generated in a certain range. The resulting ZSM-5 zeolites showed a uniformly conglobate morphology with particle sizes of 400–600 nm, aggregated with 20–50 nm crystallites, possessing a large external surface area and abundant inter-crystallite mesopores under the optimum synthesis conditions (CTAB to total SiO2 molar ratio was 0.02 and SiO2 in S-1 gel took up 8% to the total SiO2). The catalytic performance of nano-sized ZSM-5 zeolites in methanol to propylene reaction showed a high stability and high propylene selectivity.

Titanium silicalite-1(TS-1)was synthesized by a hydrothermal synthesis method with different amounts of tetrapropyl ammonium hydroxide(TPAOH)as template. The as-prepared TS-1 was characterized by scanning electron microscopy, X-ray powder diffraction, Fourier-transform infrared resonance spectroscopy, ultravioletvisible diffuse reflectance spectroscopy and nitrogen physical adsorption and desorption, and studied in the propylene epoxidation with hydrogen peroxide in a fixed bed reactor. The results showed that the amount of TPAOH had a strong influence on the grain morphology, the amount of framework Ti, and the average particle sizes of TS-1. With the increase of TPAOH amount in the synthesis(the molar ratio of TPAOH/SiO2 increasing from 0.25 to 0.45), the morphology changed gradually from ellipsoids to cubes, the particle sizes of TS-1 decreased slightly, the amount of the framework Ti increased appreciably, and the catalytic stability in the propylene epoxidation increased markedly. Moreover, all the catalysts had the same selectivity to propylene epoxide. However, when the molar ratio of TPAOH/SiO2 was further increased to 0.55, the particles became large hexagons with the size distribution in a wide range, and the catalytic stability decreased sharply although the amount of the framework Ti increased further, which can be attributed to the long diffusion paths of the reactants in the zeolite.

Mesoporous titanium silicalite-1(TS-1)was hydrothermally synthesized with the addition of triethanolamine( TEA)in the conventional process, and used in the cyclohexanone ammoximation in a continuous slurry reactor. The as-prepared TS-1 was characterized with X-ray diffraction(XRD), scanning electron microcopy( SEM), N2 adsorption-desorption, Fourier transform infrared (FT-IR)spectroscopy, UV-Visible(UV-Vis) diffuse reflectance spectra and UV Raman spectroscopy. The results indicated that the addition of TEA resulted in the formation of mesopores and the slight increase of framework titanium in TS-1. TS-1 synthesized with the addition of TEA exhibited a higher stability in the cyclohexanone ammoximation than that without the addition of TEA, attributing to the increase of mesopore volumes and the slight increase of the framework titanium in TS-1. However, when the addition of TEA was up to TEA/SiO2 ratio of 0.24, the crystallinity and framework titanium of TS-1 decreased markedly, and the average crystal sizes of TS-1 increased, with the catalyst stability becoming poor.

Activated carbon (AC) supported CuCl (CuCl/AC) for ethylene/ethane separation has been prepared with CuCl2 as precursor by a solid-state dispersion method. The samples are characterized by inductively coupled plasma optical emission spectrometry, X-ray diffraction, N2 adsorption/desorption and X-ray photoelectron spectroscopy, and investigated for ethylene (C2H4) and ethane (C2H6) adsorptions. The characterization results reveal that CuCl2 supported on AC can be highly dispersed on the surfaces of AC support and completely converted to CuCl after activation at 543 K in N2. The resultant adsorbent displays high ethylene adsorption capacity, high C2H4/C2H6 adsorption selectivity and excellent reversibility. The adsorption isotherms of ethylene and ethane on CuCl/AC at temperatures up to 333 K can be well fitted by the Sips models, and the corresponding isosteric heats of adsorption are calculated from the Clausius–Clapeyron equation. The value of isosteric heat of adsorption suggests that the interaction of ethylene with CuCl/AC is between physisorption and chemisorption.

Titanium silicalite-1(TS-1) treated with triethylamine (TEA) solution under different conditions was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet-visible diffuse reflectance spectrum (UV-Vis), nitrogen physical adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA concentration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.

The epoxidation of allyl chloride with hydrogen peroxide catalyzed by a TS-1/SiO2 catalyst in a fixed-bed reactor has been studied. The effects of reaction temperature (304–316 K), methanol concentration (73.51–76.02 wt%) and hydrogen peroxide concentration (1.44–2.02 wt%) on the reaction are investigated. The experimental results show that the decreasing rate of hydrogen peroxide conversion with reaction time on stream decreases with rising reaction temperature, methanol concentration and decreasing hydrogen peroxide concentration. The kinetics of the catalyst decay of the allyl chloride epoxidation based on the Wojciechowski model is studied by fitting the experimental data. The results show that the deactivation reaction order is two, and the catalyst exhibits higher stability with higher methanol concentration and lower hydrogen peroxide concentration.

Titanium silicalite-1 (TS-1) has been hydrothermally synthesized with tetrapropylammonium hydroxide (TPAOH) as the template in the presence of various amounts of Na+, characterized by inductively coupled plasma, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultro-violet-visible spectroscopy and studied in cyclohexanone ammoximation. The characterization results show that with the increase of Na+ concentration in the synthesis, both the crystal sizes of TS-1 and extra framework Ti increase but framework Ti decreases. The addition of Na+ below 3 mol-% of TPAOH in the synthesis does not influence the catalytic properties with above 98% conversion of cyclohexanone and 99.5% selectivity to cyclohexanone oxime. However, at the concentrations of Na+⩾3mol-% of TPAOH in the synthesis, the catalysts are deactivated faster with the increase of Na+ addition, which can be attributed to more high molecular weight byproducts deposited in the large TS-1 particles and the loss of the frame-work titanium. The results of this work are of great importance for the industry.

TS-1/SiO2 catalyst for the epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor has been investigated. The catalyst activity decreases gradually with the online reaction time, but the selectivity of propylene epoxide is kept at about 93%. The fresh, deactivated and regenerated catalysts were characterized with X-ray diffraction, Fourier transform infrared spectroscopy, ultra-violet-visible diffuse reflectance, Brunner-Emmett-Teller method and thermogravimetric analysis, and the deactivated catalyst was regenerated with H2O2/methanol solution. Compared with the fresh catalyst, both the framework structure and the content of titanium in the framework of the deactivated and regenerated TS-1/SiO2 catalysts were not changed. The major reason of the catalyst deactivation was the blockage of the channels of the catalyst by bulky organic by-products, which covered the active centers of titanium in TS-1. The deposited materials on the deactivated TS-1/SiO2 catalyst could be removed by treatment with hydrogen peroxide/methanol solution or pure methanol; the higher the treatment temperature and the higher the concentration of H2O2 in methanol, the higher the extent of the regeneration. The regeneration treatment did not influence the product selectivity in the propylene epoxidation.

Silicalite-1 was hydrothermally synthesized in the presence of different concentrations of Na+ using tetrapropylammonium hydroxide (TPAOH) as a template. The synthesis was followed by a base treatment. The silicalite-1samples were characterized using X-ray diffraction, scanning electron microscopy, N2 adsorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and NH3 temperature-programmed desorption. The samples were used as catalysts for the vapor phase Beckmann rearrangement of cyclohexanone oxime. During the synthesis, the sodium ions were incorporated onto the silicalite-1 crystals, but were then removed by the base treatment. All the catalysts exhibited nearly complete conversion of cyclohexanone oxime to ɛ-caprolactam with selectivities grater than 95%. Addition of less than 2.5 mol-% Na+ (relative to TPAOH) did not influence the catalytic properties. However, for Na+ concentrations ⩽5 mol-%, the particle sizes of silicalite-1 increased and the catalytic activities decreased, which can be attributed to carbon deposition. The results in this work are of great importance for the polymer industry.

Silicalite-1 was hydrothermally synthesized with tetrapropylammonium hydroxide (TPAOH) as the template in the presence of various Br− and Na+ concentrations, characterized by XRD, SEM, BET, XPS, FT-IR and NH3-TPD and studied in the vapor phase Beckmann rearrangement of cyclohexanone oxime. The characterization results show that the crystal sizes of Silicalite-1 increase with the increase of Na+ concentrations in the synthesis; Na+ is combined in the Silicalite-1 crystals, but removed by a base treatment. The base treated catalysts exhibit nearly complete conversion of cyclohexanone oxime with above 95% selectivity to ɛ-caprolactam. Catalysts with the addition of up to 20 mol% Br− relative to TPAOH without Na+ in the synthesis do not influence the physical and chemical as well as the catalytic properties. The addition of Na+ below 2.5 mol% of TPAOH do not influence the catalytic properties either. However, at the concentrations of Na+ ≥ 5 mol% of TPAOH in the synthesis, the catalysts deactivate faster with the increase of Na+ contents, which is attributed to more carbon deposition in the larger Silicalite-1 particles, determined by TGA. The results of this work are of great importance for the industry.Graphical abstractCatalysts S-1-20Br with up to 20 mol% Br− and S-1-2.5 with 2.5 mol% Br− and Na+ of TPAOH in the synthesis show very good stability as catalyst S-1-0 synthesized in the absence of Br− and Na+. With high concentrations of Na+ in the synthesis, the catalysts deactivate faster.Research highlights▶ Presence of Br− in synthesis does not influence properties and performance of S-1. ▶ Presence of high concentration Na+ in synthesis increases the particle sizes of S-1. ▶ S-1 synthesized in the presence of high concentrations of Na+ deactivate faster. ▶ Na+ below 2.5 mol% of TPAOH can be tolerated in synthesis of S-1 as catalyst.

A dual bed catalyst system consisting of a metallic Ni monolith catalyst in the front followed by a supported nickel catalyst Ni/MgAl2O4 has been studied for the autothermal partial oxidation of methane to synthesis gas. The effects of bed configuration, reforming bed length, feed temperature and gas hourly space velocity on the reaction as well as the stability are investigated. The results show that the metallic Ni monolith in the front functions as the oxidation catalyst, which prevents the exposure of the reforming catalyst in the back to the very high temperature, while the supported Ni/MgAl2O4 in the back functions as the reforming catalyst which further increases the methane conversion by 5%. A typical 5 mmNi monolith–5mmNi/MgAl2O4 dual bed catalyst exhibits methane conversion and hydrogen and carbon monoxide selectivities of 85.3%, 91.5% and 93.0%, respectively, under autothermal conditions at a methane to oxygen molar ratio of 2.0 and gas hourly space velocity of 1.0 × 105 h−1. The dual bed catalyst system is also very stable.

Thermodynamics of ethanol reforming with carbon dioxide for hydrogen production has been studied by Gibbs free energy minimization method. The optimum conditions for hydrogen production are identified: reaction temperatures between 1200 and 1300 K and carbon dioxide-to-ethanol molar ratios of 1.2–1.3 at 0.1 MPa. Under the optimal conditions, complete conversion of ethanol, 94.75–94.86% yield of hydrogen and 96.77–97.04% yield of carbon monoxide can be achieved in the absence of carbon formation. The ethanol reforming with carbon dioxide is suitable for providing hydrogen-rich fuels for molten carbonate fuel cell and solid oxide fuel cell. The carbon-formed and carbon-free regions are found, which are useful in guiding the search for suitable catalysts for the reaction. Inert gases have a positive effect on the hydrogen and carbon monoxide yields.

A metallic Ni catalyst has been prepared with nickel sponge and further promoted with YSZ (yttrium-stabilized zirconia) by an impregnation method. The catalysts are characterized by ICP, BET, SEM, XRD and H2-TPR, and then studied for the partial oxidation of methane to hydrogen. The influences of reaction temperature, CH4/O2 ratios and gas hourly space velocity on the reaction rate are investigated. The catalyst characterization results show that the YSZ-promoted metallic Ni catalysts have high specific surface area; there is more NiO phase in the YSZ-promoted catalysts than in the metallic Ni catalyst; a mutual diffusion of Ni2+ and Zr4+ ions might happen between the NiO and YSZ phases. The reaction results show that the YSZ promotion increases the CH4 conversion and the selectivities to H2 and CO.

Thermodynamic equilibrium of ethanol partial oxidation has been studied by Gibbs free energy minimization method for hydrogen production in the range of oxygen-to-ethanol molar ratio from 0 to 3, reaction temperature from 500 to 1400 K, pressure from 1 to 20 atm and nitrogen-to-ethanol molar ratio from 0 to 100. The optimal operation conditions were obtained, which are 1070–1200 K, oxygen-to-ethanol molar ratio of 0.6–0.8, and 1 atm. Under the optimal conditions, complete conversion of ethanol, 86.28–94.98% yield of hydrogen and 34.69–38.64% concentration of carbon monoxide could be achieved and at which no coke tends to form. The hydrogen-rich fuel obtained is suitable for the use in Molten Carbonate Fuel Cell and Solid Oxide Fuel Cell. Higher pressures have a negative effect on the hydrogen yield. Inert gases have a negative effect on the hydrogen yield at low nitrogen-to-ethanol molar ratios (below 40), but further increasing the concentrations of the inert gases increases the hydrogen yield slightly. Coke tends to form at lower temperatures and lower oxygen-to-ethanol molar ratios.

Hβ was synthesized by a hydrothermal method followed by ion exchange and treated with aqueous solutions of ammonia. The obtained catalysts were characterized by BET surface area measurement, XRD, XPS, TEM, IR, pyridine-TPD and studied in the vapor phase Beckmann rearrangement of cyclohexanone oxime. The results show that in comparison with pure Hβ, the ammonia treatments led to higher BET area, lower SiO2/Al2O3 ratio, more total acid sites, more weak acid sites, especially more weak Brønsted acid sites, and slow deactivation in the Beckmann rearrangement reaction. The results indicate that for the catalysts having the structure of β-zeolite, the suitable acid sites for the Beckmann rearrangement might be the weak Brønsted acid sites.

A MgO-promoted metallic nickel monolith was prepared from nickel sponge by sintering, acid treating and loading. The catalytic performances on the monolithic catalysts, unpromoted and promoted by MgO, were studied in the partial oxidation and oxidative steam and CO2 reformings of methane to syngas.

A series of Ti-Hβ zeolites were synthesized by liquid-solid isomorphous substitution. Hβ and Ti-Hβ zeolites were characterized by BET, XPS, IR, etc., and studied in the vapor phase Beckmann rearrangement of cyclohexanone oxime. In comparison with pure Hβ, the incorporation of Ti in the Hβ framework leads to larger BET surface area and weaker Brönsted acid sites. The incorporation of Ti in the Hβ framework increases the conversion of cyclohexanone oxime and its stability. It is inferred that for the catalysts having the structure of a β zeolite, the suitable acid sites for the vapor phase Beckman rearrangement might be the weak Brönsted acid sites.

Ti-MCM-41, B-Ti-MCM-41 and Ti-grafted MCM-41 were synthesized, characterized and studied in the epoxidation of cyclohexene. The synthetic methods and the effect of water in the oxidant are discussed.

A kind of green SiC fine powder was characterized by XRD and UV-Vis diffuse reflectance, and studied in the photocatalytic splitting of water. The results showed that the green SiC fine powder can absorb visible light and split water with the formation of hydrogen under visible light irradiation. The activity is affected significantly by the initial pH of solutions and the types of cheap reagents, where the addition of OH− or S2− leads to a remarkable increase in the activity.

Effects of organic solvent addition on the epoxidation of propene catalyzed by TS-1 were studied. It was found that addition of 1,2-dichloroethane to the reaction increased not only the conversion and utilization efficiency of H2O2, but also the selectivity to PO. The origin of the effects was studied through the characterization of the catalysts after the reaction and the influence of organic solvents on the decomposition of H2O2 and PO.

A metallic Ni catalyst was prepared with nickel sponge, followed by acid treatment. It was further promoted with yttria by an impregnation method. The catalysts were characterized by SEM, BET, XRD, TPR, XPS, etc., and studied in the partial oxidation of methane to syngas. The characterization results showed that the yttria promoted metallic Ni catalysts had high specific surface area and more NiO. The reaction results showed that the yttria promoter increased the CH4 conversion and the selectivity for H2 and CO.

•The aggregates were changed from cuboid to sphere with increasing NaOH/SiO2 ratios.•The catalytic performance in the MTP reaction was remarkably improved.•CTAB played an important role in producing aggregates of superfine ZSM-5 crystals.•The crystallization process was fast and a growth mechanism was proposed.•Centrifuging or filtration procedure can be replaced by natural sedimentation.Loose aggregates of superfine ZSM-5 crystals (S-ZSM-5) were synthesized by a seed-induced method in the presence of cetyltrimethylammonium bromide (CTAB), characterized by XRD, SEM, N2 adsorption and desorption, XRF, NH3-TPD, 27Al MAS NMR, TG analysis, FTIR and TEM, and studied for the methanol to propylene (MTP) reaction. The results showed that CTAB played a curial role in the formation of S-ZSM-5 zeolites; NaOH concentration had a significant effect on the textural properties of S-ZSM-5 zeolites, with the morphology being controllable from cuboid to sphere by varying the NaOH/SiO2 ratios from 0 to 0.27. Compared with the catalysts synthesized by the conventional seed-induced method without CTAB, all S-ZSM-5 catalysts showed much higher stability and higher propylene selectivity in the MTP reaction. The excellent catalytic performance can be attributed to the aggregates of superfine ZSM-5 crystals with abundant mesopores and more weak acid sites, which hinder various side reactions such as hydrogen-transfer reactions.NaOH/SiO2 ratios have an important effect on the aggregate morphologies and catalytic performance.

The Publisher regrets that this article is an accidental duplication of an article that has already been published in Microporous and Mesoporous Materials, DOI of original article: http://dx.doi.org/10.1016/j.micromeso.2016.10.027. The duplicate article has therefore been withdrawn.As a consequence, pages 1–9 originally occupied by the withdrawn article are missing from the printed issue. The publisher apologizes for any inconvenience this may cause.The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

•ZSM-11/5 composite is successfully synthesized with addition of CTAB without template.•Without addition of CTAB, large ZSM-5 crystals are formed.•ZSM-11/5 composite zeolites synthesized with addition of CTAB are hierarchical.•ZSM-11/5 composite exhibits excellent performance in methanol to hydrocarbon reaction.ZSM-11/5 composite zeolite was successfully synthesized through the addition of cetyltrimethylammonium bromide (CTAB) and seed, but in the absence of template. However, without the addition of CTAB, pure large hexagonal ZSM-5 crystals were formed in the presence of ZSM-11 as seed. The products were characterized by SEM, XRD, XRF, 27Al NMR, 27Si NMR, N2 physical adsorption and NH3-TPD. The SEM images imply that large ZSM-5 crystals gradually evolve from imperfect to perfect crystals, rather than forming small crystals first, and then gradually growing. The ZSM-11/5 composite zeolite exhibited hierarchical characteristics with higher specific surface areas, higher external surface areas, higher mesopore volumes and more acid sites than the sample synthesized by the conventional method with tetrabutylammonium as template. The ZSM-11/5 composite zeolite also exhibited excellent catalytic properties in the reaction of methanol to hydrocarbons.CTAB results in the formation of hierarchical ZSM-11/5 composite without template.