Comparing Al-SBA-15 Support and Pt/Al-SBA-15 Catalyst: Changes in Al Speciation and Acidic Properties Induced by the Introduction of Pt via Aqueous Medium

Differences between the acidic properties of silicoaluminic Pt-containing catalysts and those assessed on their parent supports have been reported in the literature and attributed to the presence of the metal nanoparticles and to their influence on the acid sites. It is shown here that for mesoporous materials containing various types of Al species, an alternative explanation can be proposed. ²⁷Al NMR spectroscopy, FTIR of adsorbed CO and probe catalytic tests suggest the redistribution of aluminium atoms upon contact of the parent support with the aqueous solution containing the Pt precursor. Upon contact with water and thermal treatment, strong and mild Brønsted sites (Si–O(H)–Al) transform into strong Lewis sites (isolated tetracoordinated Al atoms). As a consequence, it may not be straightforward to deduce the acidic properties of metal-containing catalysts supported on Al-containing mesoporous materials from those of the bare support, because the surface species may differ significantly.     

Synthesis of mesoporous aluminosilicates with low Si/Al ratios using a single-source molecular precursor under acidic conditions

A single molecular precursor, bis(sec-butoxy)-aluminoxy-triethoxysilane, was used as aluminum source for the synthesis of mesoporous aluminosilicates with Si/Al ratios ranging from 1 to 10 under acidic conditions. Aluminum can be stoichiometrically incorporated into the mesoporous materials at pH = 1.5. The mesoporous aluminosilicates synthesized with the single molecular precursor display larger unit cell parameter and pore diameter than that of the materials prepared with aluminum sulfate, aluminum nitrate, aluminum hydroxide, and aluminum isopropoxide as the aluminum sources. IR spectra of adsorbed pyridine and NH₃-TPD showed that both Br?nsted acidic sites and Lewis acid sites with medium strength are present in the materials. However, no direct relationship between the acidic properties and the content of aluminum was observed when the Si/Al ratios of the mesoporous aluminosilicates are lower than 10.     

Synthesis and characterization of mesoporous Mn/Al-SBA-15 and its catalytic activity for NO reduction with ammonia

Al-SBA-15 was prepared by one-step hydrothermal synthesis method, and was characterized by X-ray diffraction, N₂-adsorption, transmission electron microscope and Fourier infrared spectra of chemisorbed pyridine (Py-IR). The results showed that Al-SBA-15 had well-ordered hexagonal mesopores. As compared with Si-SBA-15, Al-SBA-15 had thicker pore wall, higher surface area, and stronger Lewis acidity. Due to the stronger Lewis acidity, Mn/Al-SBA-15 catalyst prepared by impregnation showed better activity than Mn/Si-SBA-15 in the selective catalytic reduction of NO by NH₃.     

Al-SBA-15固体酸催化合成硬脂酸三乙醇胺酯

制备了一系列Si/Al比(均为摩尔比,下同)从15到50的Al-SBA-15固体酸催化剂,并将其应用于硬脂酸与三乙醇胺的酯化反应中。结果表明,Si/Al比为25的Al-SBA-15固体酸催化剂的催化活性和选择性较高,反应6 h酯胺的酸值可降至1.78 mg KOH/g,单双酯总质量分数可达84.79%;该催化剂重复使用6次,催化活性没有明显降低,说明该催化剂具有高的稳定性。采用XRD、N2吸附脱附、透射电镜和吸附吡啶的红外光谱对催化剂的结构、比表面积和表面酸性进行了表征,结果表明,Si/Al比为25的Al-SBA-15催化剂保持了SBA-15的结构,具有大的比表面积和均一的孔径,在催化剂表面同时存在Lewis酸和Brnsted酸。     

Direct synthesis, characterization and catalytic performance of Al-SBA-15 mesoporous catalysts with varying Si/Al molar ratios

Through a directly hydrothermal process and utilizing Pluronic P123 triblock polymer (EO₂₀PO₇₀EO₂₀, M_av = 5800) as a template, Al-SBA-15 mesoporous materials have been prepared with different Si/Al molar ratios. The materials were characterized by XRD, ICP-OES, SEM, TEM, Py FT-IR, N₂ adsorption–desorption and NH₃-TPD techniques. Meanwhile, the catalytic performance of the Al-SBA-15 materials was investigated through Friedel–Crafts alkylation of 2,4-ditert-butyl-phenol with cinnamyl alcohol. Characterization results showed that the catalysts contain a variety of acid sites whose contents vary in a systematic manner with various Si/Al molar ratios of the materials, and have a higher catalytic activity in the alkylation reaction of phenol with tert-butanol. It was found that the Al-SBA-15 samples with good mesoporous structure are highly reusable preserving most of their catalytic activity after five cycles.     

Hydrocracking of heavy oil using zeolites Y/Al-SBA-15 composites as catalyst supports

A series of Y/Al-SBA-15 composites were prepared by a two-step synthesis procedure in mild acidic medium. The materials were characterized by powder X-ray diffraction (XRD), N₂ sorption isotherms and TEM techniques. Catalytic cracking of cumene and 1,3,5-tri-isopropylbenzene was carried out as the probing reactions on these composites. The XRD results showed that these materials are composites of Al-SBA-15 and Y zeolite. N₂ sorption isotherms and TEM displayed that these composites were abundant in micropores and mesopores. At the same time, the mesopores may communicate with the␣micropores in some domains, which may result in the high catalytic activities of Y/Al-SBA-15 composites for the␣cracking of both small-molecule (cumene) and large-molecule (1,3,5-tri-isopropylbenzene) hydrocarbons. The existence of mesopores may also make the acid sites easily accessible for reactants. Catalysts of W–Ni supported on Y/Al-SBA-15 and modified Y zeolites with mesopores were prepared by impregnation method, and the hydrocracking of heavy oil was performed on these catalysts. The catalyst using zeolite Y/mesoporous Al-SBA-15 composites as support gave higher yield of diesel compared to the catalysts using modified zeolite Y as support. In addition, the higher aromatics potential of heavy naphtha and the significantly lower BMCI (U.S. Bureau of Correlation Index) of tail oil revealed Y/Al-SBA-15 composite catalyst possessed integrated performance in the hydrocracking of heavy oil. These results proved that the combination of Y zeolites and mesoporous Al-SBA-15 plays a great role in improving the performance of catalysts for hydrocracking heavy oils.     

La-SO42-改性Al-SBA-15催化剂的制备与应用

以Al-SBA-15为载体,采用浸渍法制备La-SO₄^2-/Al-SBA-15催化剂,考察催化剂的制备条件。结果表明,La³⁺浓度为0.03 mol·L^-1和500 ℃焙烧3 h制得的La-SO₄^2-/Al-SBA-15在催化乙酸正丁酯反应中具有良好的催化性能。将制得的La-SO₄^2-/Al-SBA-15催化剂应用于乙酸正丁酯合成,结果表明,在n(冰乙酸)∶n(正丁醇)=1∶1.2、催化剂用量为冰乙酸质量的6%和反应3.5 h条件下,酯化率达97.85%。     

金属负载方式对Al-SBA-15/USY分子筛加氢裂化催化剂的影响

以Al-SBA-15/USY复合分子筛为主要成分,分别采用浸渍法、混捏法制备了催化剂。对催化剂进行了透射电镜（TEM）、氢程序升温还原（H₂-TPR）、氨程序升温脱附（NH₃-TPD）、氮气吸附-脱附表征。结果表明,催化剂具有微孔-介孔孔道,而且采用浸渍法制备的催化剂的孔容达到0.34 mL/g、孔径达到5.5 nm、酸量达到0.265 mmol/g,均高于混捏法制备的催化剂。以减压蜡油（VGO）为原料在200 mL评价装置上对催化剂进行评价。结果表明,与混捏法制备的催化剂相比,浸渍法制备的催化剂的中间馏分油收率提高1.6%、选择性提高1.9%。     

Mesoporous aluminosilicate catalysts from FAU precursor under mild acidic conditions and with Al in totally tetrahedral coordination

Al-SBA-15 mesoporous catalyst with strong Brönsted acid sites and Al stabilized in a totally tetrahedral coordination was synthesized from the addition of hydrothermally aged zeolite Y precursor to SBA-15 synthesis mixture under mildly acidic condition of pH 5.5. The materials possessed surface areas between 690 and 850 m²/g, pore sizes ranging from 5.6 to 7.5 nm and pore volumes up to 1.03 cm³, which were comparable to parent SBA-15 synthesized under similar conditions. As much as 2 wt.% Al was present?in the most aluminated sample that was investigated, and the Al remained stable in totally tetrahedral coordination, even after calcination at 550 °C. Calcined Al-SBA-15 showed high hydrothermal stability when treated with steam (20% v/v in nitrogen) at 650 °C for 2 h. Textural characteristics are maintained on steam treatment, and very little or no conversion of Al from tetrahedral to octahedral coordination resulted. The Al-SBA-15 mesoporous catalyst showed significant catalytic activity for cumene dealkylation, and activity increased as the amount of zeolite precursor added to the SBA-15 mixture was increased. The catalyst’s activity was not affected by the aging time of the precursor for up to the 24 h aging time investigated. This method of introducing Al and maintaining it in a total tetrahedral coordination is very effective, in comparison to other direct and post synthesis alumination methods reported.     

Y分子筛/介孔Al-SBA-15复合材料与脱铝Y分子筛的表征和重油加氢裂化性能

采用两步法和水热-化学方法制备了具有高水热稳定性的Y分子筛/介孔Al-SBA-15复合材料和含有介孔的脱铝Y分子筛,用浸渍法制备了加氢裂化催化剂,并利用XRD、N2 吸附、SEM、XRF和TEM等分析手段对Y分子筛/介孔Al-SBA-15复合材料、含有介孔的脱铝Y分子筛及其催化剂的物化性质进行了对比分析。相同条件下催化剂的重油加氢裂化性能对比评价结果表明,以Y分子筛/介孔Al-SBA-15复合材料为载体的加氢裂化催化剂的中间馏分油收率和中油选择性高达66.21%和84.5%,比以脱铝Y分子筛为载体的催化剂分别提高了5.68%和5.7%。     

Synthesis,characterization and catalytic properties of mesoporous Al-FSM-16 materials

Al-substituted mesoporous FSM-16 materials with different SiO₂/Al₂O₃ (28–452) ratios have been synthesized by intercalating kanemite using cetyltrimethylammonium bromide (CTMABr) as the intercalating agent and sodium aluminate as the aluminium source, and characterized by different physico-chemical characterization techniques. The XRD measurements revealed a slightly disordered hexagonal packing of channels in the Al-FSM-16 samples. The thermal stability of Al-FSM-16 samples was confirmed by DTA analysis, where no structural changes were observed in the temperature range of 600–900°C. No significant changes were observed in the morphology of kanemite and the Al-FSM-16 sample obtained from kanemite as revealed by the SEM analysis. This result clearly indicated that the Al-FSM-16 sample is formed via a folded sheet mechanism. Moreover, TEM measurements confirmed the presence of a slightly disordered hexagonal array of channels in Al-FSM-16 in agreement with the XRD results. The BET surface areas (638–788 m² g⁻¹) and pore volumes (0.57–0.87 cm³ g⁻¹) were indicative of the high porosity of the Al-FSM-16 samples. The Al-FSM-16 (SiO₂/Al₂O₃ = 49) sample exhibited excellent hydrothermal stability at 150°C. The Al-FSM-16 samples were found to catalyze the isomerization of m-xylene to p- and o-xylenes.     

Synthesis and characterization of Co-containing SBA-15 catalysts

Two Co-SBA-15 catalysts were synthesized and characterized by thermogravimetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, porosity, UV–visible diffuse reflectance and temperature programmed reduction with H₂. The first catalyst was prepared synthesizing SBA-15 and then adding Co ions by impregnation (Co_imprSBA-15). The second catalyst was prepared using a more complex procedure of immobilization of cobalt ions in the presence of pyridine and H₂O₂ on –COOH groups anchored to the SBA-15 structure [Co-SBA-15(COOH)]. These COOH groups were created starting from cyano groups introduced during the synthesis of the periodic mesoporous materials as 4-triethoxysilylbutyronitrile. Characterization of the samples indicates that in both cases the typical 2D periodical hexagonal structure of SBA-15 was obtained, but with less ordered packing in the second case. The cobalt is highly dispersed in the SBA-15 (up to 9% w/w) and is present mainly as Co²⁺ ions in highly distorted tetrahedral or square pyramidal coordination. Some coordinatively unsaturated Co(II) Lewis acid centers are present in Co_imprSBA-15, while in Co-SBA-15(COOH) coordination of pyridine to cobalt tentatively may induce the formation of Co³⁺ ions, although in both catalysts the dominant species are Co²⁺ ions in a very close environment.     

Synthesis of mesoporous aluminosilicates with low Si/Al ratios using a single-source molecular precursor under acidic conditions

A single molecular precursor, bis(sec-butoxy)-aluminoxy-triethoxysilane, was used as aluminum source for the synthesis of mesoporous aluminosilicates with Si/Al ratios ranging from 1 to 10 under acidic conditions. Aluminum can be stoichiometrically incorporated into the mesoporous materials at pH = 1.5. The mesoporous aluminosilicates synthesized with the single molecular precursor display larger unit cell parameter and pore diameter than that of the materials prepared with aluminum sulfate, aluminum nitrate, aluminum hydroxide, and aluminum isopropoxide as the aluminum sources. IR spectra of adsorbed pyridine and NH₃-TPD showed that both Brönsted acidic sites and Lewis acid sites with medium strength are present in the materials. However, no direct relationship between the acidic properties and the content of aluminum was observed when the Si/Al ratios of the mesoporous aluminosilicates are lower than 10.     

A comparative investigation on the properties of Cr-SBA-15 and CrOx/SBA-15

High-surface area and well-ordered mesoporous Cr-incorporated SBA-15 (Cr-SBA-15) and SBA-15-supported chromia (CrO_x/SBA-15) with Cr surface density = 0.05–1.11 Cr-atom/nm² have been prepared, respectively, using the one-step synthesis and incipient wetness impregnation method, and characterized by AAS, XRD, BET, ESEM, TEM, XPS, laser Raman, UV-Vis, FT-IR, and H₂-TPR. It is observed that the Cr-SBA-15 and CrO_x/SBA-15 samples showed an evolution of surface morphology from long chain-shaped to short rod-like and further to an irregularly spherical architecture at elevated Cr content, which might arise from the interaction of Cr ions or CrO_x domains with SBA-15. There were co-presence of tetrahedrally coordinated mono- and poly-chromate (Cr⁶⁺) as well as octahedrally coordinated Cr³⁺ species in Cr-SBA-15 and CrO_x/SBA-15, with the Cr⁶⁺ species being dominant at Cr surface density ≤0.22 Cr-atom/nm² in Cr-SBA-15 and Cr ≤0.54 Cr-atom/nm² in CrO_x/SBA-15, whereas the amount of the Cr³⁺ species increased markedly at Cr surface density ≥0.53 Cr-atom/nm² due to the formation of crystal Cr₂O₃ phase. Maximal Cr incorporation into Cr-SBA-15 and one monolayer surface CrO_x coverage on CrO_x/SBA-15 occurred at Cr surface density ≤0.53 Cr-atom/nm² and <1.11 Cr-atom/nm², respectively. The CrO_x/SBA-15 samples exhibited better reducibility than the Cr-SBA-15 samples, with the best reducibility exhibited at Cr surface densities of 0.54 and 0.12 Cr-atom/nm², respectively.     

Synthesis of mesoporous MOR materials by varying temperature crystallizations and combining ternary organic templates

An approach, which involved perturbations of synthesis conditions in crystallization temperature and organic template composition, has been proposed for derivation of mesopores from bulk structural defects formed in mordenite (MOR) phases, based on the character of intrinsic crystal defects and tensional distortions of two compressed 8-membered rings in MOR framework. Consequently, hierarchically porous materials with MOR structures were prepared by varying temperature synthesis and using ternary organic micelles templates. The synthesized materials were characterized by powder X-ray diffraction, nitrogen adsorption at 77 K and transmission electron microscopy. These crystalline materials combined the advantages of both mordenites with the micropore system and mesoporous materials by featuring an additional intracrystalline mesopore system in MOR single crystals, resulting in a hierarchical pore distribution in range of 1.7-80.0 nm together with the significant specific surface areas. In particular, individual crystal morphologies of typical mesoporous MOR materials showed the defect-rich structures responding essentially to the mesoporosity; the mesoporous materials were substantiated matchable well to normal mordenites in acid capacity and acid strength distribution. Furthermore, several factors acting on intracrystalline mesopore formation were elucidated for explicating the perturbation synthesis approach, and whole reaction routes for synthesizing different solid products under related crystallization conditions were summarized coupling with a demonstration of part TEM micrographs. The overall results suggested that the investigative approach of perturbation imposed on crystal growth provides an alternative route for direct hydrothermal synthesis of mesoporous zeolite materials and implied that bulk structural defects within single crystals lead to the formation of intracrystalline mesopores in various sizes.     

Influence of initial Si/Al ratios on the structural,acidic and catalytic properties of nanosized-ZSM-5/SBA-15 analog composites prepared from ZSM-5 precursors

Nano-ZSM-5/SBA-15 analog composites (ZSC) were prepared in a two-step process from ZSM-5 precursors with different Si/Al molar ratios (10–50) via high-temperature synthesis in mildly acidic media (200 °C, pH 3.5) aiming to evaluate the influence of the initial Si/Al ratio on their structural, acidic and catalytic properties. The resulting materials were characterized by SAXS, XRD, FTIR, TEM, N₂ sorption, ²⁷Al solid state-NMR, NH₃-TPD, FTIR spectroscopy of adsorbed pyridine, AAS and ICP-AES. Under the applied synthesis conditions, a ZSC material with controlled distribution of nano-ZSM-5 and SBA-15 analog phases can be prepared from ZSM-5 precursors by adjusting the initial Si/Al ratio in the range of 20–30. Increasing the initial Si/Al ratio to 50, only ZSM-5 nanocrystals were obtained whereas reducing the initial Si/Al ratio to 10 led to the formation of a disordered mesoporous SBA-15 analog. The total acidity increases with the crystallinity of the ZSM-5 phase as varying the Si/Al ratio from 10 to 30 despite the decreased amount of incorporated aluminum. However, the acidity declines slightly when raising the Si/Al ratio to 50 because of the low incorporated aluminum. The catalytic performance of the ZSC materials compared to the reference materials, i.e. purely mesoporous Al-SBA-15 and purely microporous H-ZSM-5 was assessed in the gas phase cracking of cumene and 1,3,5-tri-isopropylbenzene (TIPB) as test reactions. The results show that a balanced ratio of nano-ZSM-5 and SBA-15 analog phases obtained by tuning the initial Si/Al ratio is crucial to achieve superior catalytic performance of the ZSC materials in the cracking of both cumene and TIPB.     

NO2 and N2 sorption in MFI films with varying Si/Al and Na/Al ratios

MFI crystals or films with controlled thicknesses and different Si/Al ratios were grown on seeded cordierite monoliths using a clear synthesis mixture with template or a template-free gel. The materials were analyzed by scanning electron microscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectrometry, X-ray photoelectron spectroscopy, thermogravimetric analysis and sorption experiments using N₂ or NO₂ adsorbates. The films were uniformly distributed over the support surface. As expected, the specific monolayer N₂ adsorption capacity (mol/g_zeolite) was constant and independent of film thickness. The specific molar NO₂ adsorption capacity was significantly lower than the specific molar monolayer N₂ adsorption capacity, indicating that NO₂ is adsorbed at specific sites rather than evenly distributed in a monolayer. A number of NO₂ adsorption sites with varying strengths were observed by TPD experiments. At 30 °C, the amount of adsorbed NO₂ in the MFI films increased with increasing Al and Na content as opposed to the N₂ adsorption capacity, which was independent of these parameters. At 200 °C, the adsorbed amount of NO₂ was lower than at 30 °C and apparently independent on Al concentration in the Na-MFI films. These results indicate that different mechanisms are involved in NO₂ adsorption. NO₂ may adsorb weakly on Na⁺ cations and also react with silanol groups and residual water in the zeolite, the latter two results in more strongly bound species. Upon NO₂ adsorption, formation of NO was observed. This work represents the first systematic study of the effects of Al and Na content on NO₂ adsorption in MFI films.     

碳纳米管/有机酸复合相变材料的制备及性能

以多壁碳纳米管（MWNT）为支撑材料，十二酸（LA）、十四酸（MA）、十六酸（SA）和十八酸（PA）为相变主材，采用熔融共混法制备不同成型复合相变材料。利用压片机、红外热成像仪、导热系数测试仪和电阻率测试仪对成型材料的物理性质、温度场分布、蓄-放热时间、导热率和电阻率进行测试。结果表明，成型压力和MWNT添加量对复合材料密度影响较小。4种有机酸中分别添加24%、19%、25%和26%的MWNT时，有机酸不会泄漏。成型后虽然温度场分布更均匀，且具有良好疏水性，但蓄热速度减缓。复合材料导热率分别比纯有机酸提高2.7~3.7倍、2.7~4.5倍、2.7~4.4倍和1.7~2.4倍。压力从1MPa变到11MPa时，复合材料电阻率分别减小75.9%、76.5%、72.2%和74.0%，材料电阻率变化曲线拟合表明两者之间相关性较高。说明制备的复合相变材料具有良好的疏水、导热和导电性能。     

Synthesis and characterization of boron-acrylate/Santa Barbara Amorphous-15 polymer composite

In the present work, boron-acrylate/Santa Barbara Amorphous (SBA)-15 polymer composite was synthesized using free radical polymerization method. Firstly, SBA-15 was functionalized with 3-(trimethoxysilyl)propyl methacrylate to obtain chemically bonded boron acrylate (BAc) polymer on the SBA-15 surface. The structural analysis was evaluated via Fourier-transform infrared spectroscopy and solid-state nuclear magnetic resonance ¹³C. Samples were also characterized by using scanning electron microscopy, X-ray powder diffraction, N₂ adsorption/desorption and thermogravimetric analysis. In order to examine the BAc polymers in the mesopores, the silica framework was removed via hydrofluoric acid etching process. The results indicated that the synthesis of boron-acrylate/SBA-15 polymer composite was performed successfully. Thermal stabilities of the composites were higher with greater amounts of BAc polymer in mesopores under oxidative conditions.     

Synthesis, characterization and electrochemical performance of mesoporous FePO4 as cathode material for rechargeable lithium batteries

Mesoporous FePO₄ could deliver enhanced specific capacity of 160 mAh g⁻¹ at first discharge process, 90% of theoretical capacity of pure FePO₄, and 135 mAh g⁻¹ in the following cycles at 0.1 C rate. At 1 and 3 C rates, the capacities are 110 and 85 mAh g⁻¹, respectively, which is much higher than that of previously reported for modified FePO₄ materials. Electrochemical impedance spectroscopy (EIS) tests proved that mesoporous structure in FePO₄ materials enhanced the lithium ion intercalation/deintercalation kinetics as indicated by smaller charge transfer resistance (R_ct) of these materials. These results revealed that this mesoporous electrode material can be a potential candidate for high-power energy conversion devices.