Promotion effect of cerium and lanthanum oxides on Ni/SBA-15 catalyst for ammonia decomposition

CeNi/SBA-15 and LaNi/SBA-15 catalysts were prepared by deposition–precipitation (DP) method and characterized by N₂ physical adsorption, XRD, H₂-TPR, H₂-chemisorption and TEM. Their catalytic performances in the ammonia decomposition reaction were tested and compared with Ni/SBA-15 catalyst. Addition of cerium and lanthanum oxides to the Ni/SBA-15 catalyst caused some decrease of BET surface area and pore volume of the catalysts, but led to a promotion effect to their catalytic activity which was closely related to the ratio of Ce (La)/Ni. The highest conversion of ammonia could be obtained when the Ce (La)/Ni ratio was around 0.3. The promotion effect is more evident on CeNi/SBA-15(0.3) than on LaNi/SBA-15(0.3) catalyst under identical reaction conditions. The CeNi/SBA-15 and LaNi/SBA-15 catalysts show smaller nickel particle size and easier reducibility in comparison with the Ni/SBA-15 catalysts.     

Dispersion of Nano Nickel Particles over SBA-15 Modified by Carbon Films on Pore Walls

Mesoporous SBA-15 was prepared by using P123 as a template. The precursor with the template was calcined in an inert atmosphere so that carbon films might be formed in pores of SBA-15 due to the decomposition of template. The SBA-15C thus formed contained 3% C and exhibited similar pore structures as the SBA-15. Both SBA-15 and SBA-15C were used to support 20% nickel (by weight) via impregnation. It was found that doping with carbon films enhanced the dispersion of supported nickel. However, calcination at high temperatures before the reduction had a negative effect on the dispersion of nickel. The un-calcined 20%Ni/SBA-15C after the reduction in H₂ at 673 K exhibited the highest dispersion of nickel (42%) and smallest average particle size of about 2.4 nm, in the catalysts studied in this work. It was also the most active catalyst for the hydrogenation of toluene to methyl cyclohexane. Conversion of toluene could be detected even at room temperature and atmospheric pressure for the catalyst in a fix-bed reactor, and 100% conversion of toluene was reached when temperature was raised to 358 K.     

Effects of functionalization conditions of sulfonic acid grafted SBA-15 on catalytic activity in the esterification of glycerol to monoglyceride: a factorial design approach

A series of propyl sulfonic acid-modified SBA-15 catalysts (SBA-15SO₃H) was prepared under various conditions using post-functionalization approach. A factorial design coupled with response surface analysis were employed to evaluate the effects of the preparation conditions on the catalyst activity. Optimization of the conditions to find the most active SBA-15SO₃H catalyst with the highest activity in glycerol esterification with lauric acid at 160?°C for 6?h was also made. Amount of 3-(mercaptopropyl)trimethoxysilane (MPTMS) and reflux time were chosen as parameters of the preparation conditions. The presence of propyl sulfonic acid groups in SBA-15SO₃H catalysts was confirmed by FT-TIR method. The catalysts were also characterized by means of surface analysis, XRD, TEM and TGA. The results obtained from the statistical models suggested that the amount of MPTMS was more important parameter to influence the activity compared to the reflux time. The optimum preparation condition was achieved at a reflux time of 20?h and an MPTMS amount of 1?mL/gram SBA-15 to obtain the SBA-15SO₃H(1) with the highest monoglyceride selectivity (70.2%) and corresponding lauric acid conversion (95%) in the esterification process.     

Potassium-modified molybdenum-containing SBA-15 catalysts for highly efficient production of acetaldehyde and ethylene by the selective oxidation of ethane

Mo-incorporated SBA-15 (Mo-SBA-15) catalysts with different Mo:Si molar ratios were synthesized by a direct hydrothermal method, and SBA-15-supported Mo catalysts (Mo/SBA-15 and K-Mo/SBA-15) were prepared by an incipient-wetness impregnation method. The structures of the catalysts were characterized by means of N₂ adsorption–desorption, XRD, TEM, FT-IR, and UV-Raman, and their catalytic performance for the oxidation of ethane was tested. Turnover frequency and product selectivity are strongly dependent on the molybdenum content and catalyst preparation method. Furthermore, the addition of potassium promotes the formation of isolated tetra-coordination molybdenum species and potassium molybdate. The K/Mo-SBA-15 catalysts possess much higher catalytic selectivity to acetaldehyde in the selective oxidation of ethane than the supported molybdenum catalysts (Mo/SBA-15 or K-Mo/SBA-15). The highest selectivity of CH₃CHO + C₂H₄ 68.3% is obtained over the K/Mo-SBA-15 catalyst. Analysis of kinetic results supports the conclusion that ethane oxidation is the first-order reaction and ethane activation may be the rate-determining step for the oxidation of ethane. Ethylene is a possible intermediate for acetaldehyde formation.     

Efficient cyclohexyl acrylate production by direct addition of acrylic acid and cyclohexene over SBA-15-SO3H

A set of propysulfonic acid modified mesostructured silica materials (SBA-15-SO₃H) were prepared by a convenient one-pot co-condensation method. Samples were characterized by XRD, FT-IR, Py-FTIR, N₂ adsorption–desorption, elemental analysis and acid–base titration. The catalysts exhibited excellent activities and selectivities for addition esterification of acrylic acid and cyclohexene. The highest catalytic activity (82.8 %) and selectivity (92.6 %) were obtained over SBA-15-SO₃H (15 %). The efficient catalytic performance of SBA-15-SO₃H (15 %) was attributed to the high surface area, proper mesopore texture and presence of sulfonic acid groups in its structure. SBA-15-SO₃H catalyst was easily separated and recycled with high stability.     

SBA-15 mesoporous silica modified with rhodium by MDD method and its catalytic role for N<Subscript>2</Subscript>O decomposition reaction

SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N₂O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)₃ as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified with metals were characterized with respect to metal loading (EPMA), structure (XRD), texture (BET), morphology (SEM), Rh dispersion (oxygen chemisorption), surface acidity (pyridine adsorption) and chemical nature of introduced copper and iron species (UV–vis-DRS). The rhodium-containing SBA-15 samples were found to be active catalysts for the N₂O decomposition reaction. Deposition of Al on the Rh-loaded catalyst increased its activity. An opposite effect was observed for the samples modified with Cu and Fe.     

Total Oxidation of Naphthalene Using Mesoporous CeO2 Catalysts Synthesized by Nanocasting from Two Dimensional SBA-15 and Three Dimensional KIT-6 and MCM-48 Silica Templates

Ceria catalysts have been prepared by a nanocasting procedure using SBA-15, MCM-48 and KIT-6 silica-based templates, and investigated for the total oxidation of naphthalene. In all cases cubic fluorite CeO₂ was prepared, and the structure of the template was replicated when SBA-15 and MCM-48 were used. The KIT-6 template was not replicated by the nanocasting synthesis, but in all cases mesoporous CeO2 was obtained with high surface areas (91–190 m² g^?1). All of the catalysts demonstrated high activity for naphthalene oxidation to CO₂, and the most active was the catalyst prepared from the KIT-6 template. The high activity was attributed to the small crystallite size of the CeO₂, combined with high surface area and the highly accessible catalyst surface.     

A mesoporous Pt-SBA-15 nano architecture with catalytic functions on oxidation of CO

Among many kinds of noble metal catalysts, platinum is the most efficient and widely used as automotive exhaust catalysts for treatment to remove poison gases. Due to the regular pore system and controllable pore size, mesoporous silica has been acknowledged as supports of adsorption, separation, catalysts for the extremely large surface areas and shape selective properties. SBA-15 supported Pt particles are prepared by a facile method and characterized by X-ray diffraction, Transmission Electron Microscopy and N₂ isotherms techniques. Results indicate that the Pt precursor is introduced into the mesoporous successfully and all of the particles are confined in SBA-15 with monodispersed form and uniform size. The catalytic activity of Pt-SBA-15 on oxidation of carbon monoxide are also investigated and the result indicate that the catalysts possess high catalytic activity, catalytic efficiency and stability on oxidation of CO.     

高分散的Ir/SBA-15的制备及其催化性能

采用一锅法将P123、TEOS、HCl和H2IrCl6溶液混合,酸性条件下得到高度分散的Ir/SBA-15催化剂.使用X射线衍射、透射电镜和N2吸附-脱附等对样品进行表征.结果表明,一步合成的Ir/SBA-15依然保持高度有序的介孔孔道结构、较大比表面积和孔容,而且Ir在SBA-15孔道内高度分散.CO的催化氧化反应结...     

Catalytic activity of mesoporous V/SBA-15 in the transesterification and esterification of fatty acids

Mesoporous V/SBA-15 with different weight percentages (1, 2.5 and 5 wt%) of vanadia was prepared via the wet impregnation method. The mesoporous nature of the catalysts were investigated, using the X-ray diffraction analysis, N₂ adsorption–desorption isotherm and scanning electron microscope. All the catalysts showed the highly dispersed vanadia was confirmed by the result of the diffuse reflectance UV vis technique. From the NH₃-temperature programmed desorption, it is observed that, the acidity values of the prepared catalysts are in the range 72–102 µmol/g. 5 % V/SBA-15, possesses Bronsted and Lewis acid sites ensured by pyridine-adsorbed Fourier-transform infrared method. The acidity of the catalyst was experimented in the transesterification of sunflower oil. The reaction conditions were optimized with maximum conversion (100 %) of sunflower oil into biodiesel and the activity of the catalyst was found to be more in 5 wt% V/SBA-15 at 140 °C. Different fatty acids like butyric, valeric, caprylic and oleic acid were also studied under optimized conditions, and the isolated product was confirmed from the H¹ NMR spectroscopy.     

Preparation, characterization, and catalytic properties of the Mo2C/SBA-15 catalysts

A series of Mo₂C/SBA-15 catalysts with different Mo contents were prepared by temperature-programmed carburization (TPC). The materials obtained and their oxide precursors (MoO₃/SBA-15) were characterized by Nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), and Fourier transform-infrared (FT-IR) spectroscopy. The activities of the catalysts for deep hydrodesulfurization (HDS) of thiophene were evaluated. The results of N₂ adsorption-desorption isotherms indicated that the surface area and pore diameter of the oxide precursors increase after carburization. The XRD patterns show that Mo₂C particles are highly dispersed in the SBA-15 ordered mesoporous. The test results show that Mo₂C/SBA-15 catalysts have an excellent performance for the deep HDS under the lower temperature region.     

Preparation of High-Density Fuel Through Dimerization of β-Pinene

High-density fuel was prepared by catalytic dimerization and subsequent hydrogenation. Different amounts of phosphotungstic acid (H₃PW₁₂O₄₀, HPW) were loaded on mesoporous silica (SBA-15) by a simple impregnation method to prepare HPW/SBA-15 catalysts. The prepared catalysts were mesoporous. Characterizations indicated that the dispersion and the specific surface area depend on the HPW amount. The obtained dimers from catalytic dimerization of β-pinene underwent isomerization and then dimerized to form the heterogeneous products. At the optimum load of HPW, the HPW/SBA-15 catalyst displayed the highest catalytic activity and the increased yield of dimer for a 3-h reaction. After the subsequent hydrogenation reaction, the obtained hydrogenated dimer products displayed a density and a volume calorific value comparable to those of commercial JP-10.     

MgO-SBA-15 Supported Pd-Pb Catalysts for Oxidative Esterification of Methacrolein with Methanol to Methyl Methacrylate☆

Novel MgO–SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO–SBA-15 supports were synthesized with different...     

Catalytic performance of Ti-SBA-15 prepared by chemical vapor deposition for propylene epoxidation

Ti-SBA-15C catalysts were prepared by supporting Ti on SBA-15 with chemical vapor deposition (CVD) using TiCl₄ as titanium source, and were characterized by XRD, N₂ adsorption, FT-IR and ICP. The results show that SBA-15E prepared by ethanol solution extracting template has higher concentration of surface Si-OH groups than SBA-15 calcined at 550 °C, resulting in high Ti content on Ti-SBA-15EC prepared by CVD. The temperature and time of TiCl₄ deposition affect the Ti content and catalytic activity of Ti-SBA-15EC for the epoxidation of propylene with cumene hydroperoxide (CHP). Ti-SBA-15EC prepared by CVD at 700 °C for 1.5 h exhibits more excellent performance than Ti-SBA-15C, Ti-SBA-15 prepared hydrothermally and Ti/SBA-15 (impregnation method), and the 87.3% conversion of CHP and 96.4% selectivity to propylene oxide can be obtained at 80 °C for 4 h. The performance of Ti-SBA-15EC is decreased hardly for the epoxidation of propylene after used repeatedly 6 times.     

SBA-15/Ni/TiO2/CNTs复合材料的制备及其光催化性能

通过溶胶凝胶法,经多次涂覆在SBA-15上负载掺杂镍的纳米TiO₂,得到SBA-15/NiO/TiO₂复合物;再以TiO₂中还原态金属镍为催化剂,通过化学气相沉积法（CVD）,在SBA-15/NiO/TiO₂表面原位生长碳纳米管,制得SBA-15/Ni/TiO₂/CNTs复合材料。通过XRD、SEM、TEM、UV-Vis和Raman等方法考察了SBA-15/Ni/TiO₂/CNTs复合材料的结构和性能,并通过降解亚甲基蓝溶液评价其光催化活性。结果表明,SBA-15/Ni/TiO₂/CNTs复合光催化剂的催化活性较SBA-15/NiO/TiO₂显著提高。 二次涂覆掺杂镍的二氧化钛制得的复合光催化剂的催化活性高于一次涂覆。     

Hydrotreating of gas oil on SBA-15 supported NiMo catalysts

The siliceous and the metal substituted (B or Al)-SBA-15 molecular sieves were used as a support for NiMo hydrotreating catalysts (12 wt.% Mo and 2.4 wt.% Ni). The supports were characterized by X-ray diffraction (XRD), scanning electron microscopy and N₂ adsorption–desorption isotherms. The SBA-15 supported NiMo catalysts in oxide state were characterized by BET surface area analysis and XRD. The sulfided NiMo/SBA-15 catalysts were examined by DRIFT of CO adsorption and TPD of NH₃. The HDN and HDS activities with bitumen derived light gas oil at industrial conditions showed that Al substituted SBA-15 (Al-SBA-15) is the best among the supports studied for NiMo catalyst. A series of NiMo catalysts containing 7–22 wt.% Mo with Ni/Mo weight ratio of 0.2 was prepared using Al-SBA-15 support and characterized by BET surface area analysis, XRD and temperature programmed reduction and DRIFT spectroscopy of adsorbed CO. The DRIFT spectra of adsorbed CO showed the presence of both unpromoted and Ni promoted MoS₂ sites in all the catalysts, and maximum “NiMoS” sites concentration with 17 wt.% of Mo loading. The HDN and HDS activities of NiMo/Al-SBA-15 catalysts were studied using light gas oil at temperature, pressure and WHSV of 370 °C, 1300 psig and 4.5 h⁻¹, respectively. The NiMo/Al-SBA-15 catalyst with 17 wt.% Mo and 3.4 wt.% of Ni is found to be the best catalyst. The HDN and HDS activities of this catalyst are comparable with the conventional Al₂O₃ supported NiMo catalyst in real feed at industrial conditions.     

Selective oxidation of propane to oxygenates over mesoporous SBA-15-supported potassium catalysts

As a novel catalyst system for the selective oxidation of low alkanes, mesoporous SBA-15-supported potassium catalysts were firstly employed for the selective oxidation of propane to oxygenates by using molecular oxygen as oxidant. It was found, compared with bare mesoporous SBA-15, that the selectivities to the oxygenates including formaldehyde, acetaldehyde, acrolein and acetone were remarkably enhanced over K _x /SBA-15(K:Si = x:100, mol) catalysts, and the main products were acrolein and acetone. At 500 °C, the yield of the oxygenates can reach 464% over K_3.0/SBA-15, which is the highest value over SBA-15–supported potassium catalysts. The catalysts were characterized by XRD and BET techniques. The results demonstrated that the catalytic performance was strongly dependent on the potassium content of the catalysts. Furthermore, the highly dispersed potassium on the catalyst surface was shown to be important to orientate the reaction toward the production of oxygenates. The obtained results showed that mesoporous structure, uniform pore sizes and appropriate pore surface area were favorable for the selective oxidation of propane. The samples with moderate amount of potassium promoted the selectivity to the oxygenates.     

SBA-15改性固体酸催化合成乙酸正丁酯的研究

以SBA-15为载体利用尿素水解法制备Zro2/SO2(4)-改性的固体酸SZ/SBA-15,通过XRD、N2吸附-脱附、IR、SEM 、Hammett指示剂法和N H3-TPD法对合成材料的孔结构、骨架结构及表面酸性等进行了表征.实验结果表明,所合成的固体酸催化剂具有典型的介孔结构特征,酸强度在0.80 < Ho <...     

Ethylene polymerization catalyzed by metallocene supported on mesoporous materials

Summary  In this work, different mesoporous materials were employed for the preparation of supported metallocene catalysts to be evaluated in ethylene polymerization and their performance was related to the chemistry of the materials surface used as support. The supports employed were MCM-41, SBA-15 and mesoporous TiO₂. The performance of the prepared catalysts was compared with the homogeneous catalyst precursor system. Those mesoporous materials, as well as the prepared metallocene catalysts, were analyzed by infrared absorption spectrometry (FTIR). Polymers were also characterized by FTIR, for the determination of the number-average molecular weight, and by differential scanning calorimetry (DSC) to determine thermal characteristics of the produced polyethylene. Among the studied metallocene supported catalysts, the one based on the mesoporous support SBA-15 achieved the highest activities, almost as high as that observed for the homogeneous system.     

Preparation of solid acid catalyst packing AAO/SBA-15-SO3H and application for dehydration of xylose to furfural

The solid acid catalyst packing AAO/SBA-15-SO₃H was prepared by the co-condensation and grafting method with porous anodic aluminum oxide (AAO) as support. FT-IR, SEM and TEM were applied to characterize the prepared samples. Results showed that catalysts prepared by two methods both contained active centers, and SBA-15 nanorod arrays grow inside a porous alumina membrane AAO and are perpendicular to the substrate. Their catalytic performances were tested for dehydration of xylose to furfural. The conversion of xylose and selectivity of furfural were 90% and 74% on the AAO/SBA-15-SO₃H(C) catalyst prepared by the co-condensation method, respectively. The deactivation and regeneration of the AAO/SBA-15-SO₃H(C) catalyst for the dehydration of xylose were also investigated, the activity of catalyst treated by 30 wt.% H₂O₂ almost was recovered.