Ordered Mesoporous Materials with Improved Stability and Catalytic Activity

Microporous crystals of zeolites such as Y, Beta, and ZSM-5 are widely used commercial catalysts, but their applications are strongly limited by their small pore sizes. Recent progress in solving this is used to ordered mesoporous materials such as MCM-41, HMS, and SBA-15. These mesoporous materials have pore diameters of 2.0–30 nm and exhibit good catalytic properties for the catalytic conversion of bulky reactants. However, when compared with microporous crystals of zeolites, the catalytic activity and hydrothermal stability are relatively low, which severely hinders their practical applications in industrial catalytic reactions such as petroleum cracking. The relatively low catalytic activity and hydrothermal stability can be attributed to the amorphous nature of the mesoporous walls. In this account, we systemically review the routes for improving catalytic activity and hydrothermal stability of mesoporous materials, which include (1) acidic sulfated zirconia supported in mesoporous materials; (2) strongly acidic and thermally stable mesostructured sulfated zirconia with tetragonal crystalline phase; (3) strongly acidic and hydrothermally stable mesoporous aluminosilicates synthesized in alkaline media; (4) strongly acidic and hydrothermally stable mesoporous aluminosilicates synthesized in strongly acidic media; (5) hydrothermally stable mesoporous titanosilicates with catalytically active titanium species in oxidations; (6) high-temperature generalized synthesis of ultrastable ordered mesoporous silica-based materials by using fluorocarbonhydrocarbon surfactant mixtures.     

锯末快速热解气的在线催化裂解

采用Py-GC/MS装置对锯末进行快速热解并对热解气进行在线检测,研究了HZSM-5分子筛和SBA-15介孔催化剂对热解气进行在线催化裂解的效果。结果表明,热解气经HZSM-5催化裂解后,乙酸、羟基乙醛、呋喃类以及酚类物质的产率都大幅降低,同时形成了大量的芳香烃产物,主要是甲苯和二甲苯;而热解气经SBA-15催化裂解后,乙酸产率降低、羟基乙醛产率稍有降低、呋喃类和酚类物质的产率增加,只检测到了极少的烃类产物。由此可知,这两种催化剂对热解气有着不同的催化裂解效果：HZSM-5具有较好的催化脱氧功效;而SBA-15则基本不具有催化脱氧形成烃类产物的能力,但其介孔结构能够允许生物质裂解过程中形成的分子较大的低聚物进入其中并发生二次裂解,从而形成小分子产物。     

添加Sm对Pt /SBA-15催化苯完全氧化反应活性和热稳定性的影响

以Pt/SBA-15为催化剂,考察催化剂载体中添加Sm对于苯的完全氧化反应活性和热稳定性影响。采用了一种简便的记录起燃温度曲线和催化剂热稳定性评价方法,即向装载好催化剂的固定床反应器中持续通入恒定流量的反应气,逐步阶段性升高反应温度,同时在线检测出口尾气的浓度变化, 得到起燃温度曲线后,继续提高反应温度,然后恒定在某一设定的温度(如550℃)持续运行较长时间, 期间定时在线取样分析,如果有必要还可以连续考察降温情况下催化剂的反应活性情况。研究结果表明,几种催化剂低温活性次序为：Pt/SBA-15≈Pt/4%Sm₂O₃/SBA-15> Pt/Sm₂O₃> 4%Sm₂O₃/SBA-15,而对于高温稳定性则是Pt/4%Sm₂O₃/SBA-15> Pt/1.2%Sm₂O₃/SBA-15> Pt/SBA-15,Pt/Sm-SBA-15(SG)> Pt/SBA-15(SG)。总之,Sm的添加虽然未能提高Pt/SBA-15的低温催化活性,但是能明显提高催化剂在高温情况下活性的稳定性。1%Pt/4%Sm₂O₃/SBA-15同时具备较好的低温催化活性和高温稳定性,具有较好的应用前景。     

The Production of Straight Carbon Microfibers by the Cracking of Methane over Co-SBA-15 Catalysts

Cobalt incorporated SBA-15 (Co-SBA-15) catalysts were prepared by using hydrothermal synthesis and over which very straight carbon microfibers were made by cracking CH₄. The influence of Co loading (from 0.5 to 3 wt%) in SBA-15 and cracking temperature on the methane conversion, structures and morphologies of the microfibers was investigated. The highest yield of microfibers was obtained at 800 °C over the 2 wt% Co loaded SBA-15 catalyst. After 16 h reaction, the carbon fibers almost stopped further growth. The diameter of the carbon microfibers could be roughly controlled by judiciously adjusting the Co concentration in SBA-15. The carbon microfiber’s growth followed a root-growth mechanism. XRD, HRTEM and Raman studies confirmed that the microfibers were graphitic. The microfiber grown over the 0.5 wt% cobalt loaded SBA-15 catalyst had a higher degree of graphitic structural order than that obtained over the 2 wt% cobalt loaded one.     

固体超强酸SO42-/ZrO2/SBA-15的合成及其催化活性

水热合成了介孔材料SBA-15,并以其为载体负载固体超强酸SO42-/ZrO2,通过XRD和N2吸附/脱附对制备的SO42-/ZrO2/SBA-15催化剂进行了表征。在固定床反应器中,以丙烯和乙酸为原料,研究了该催化剂合成乙酸异丙酯的活性。结果表明实验制备的催化剂具有较好的介孔结构,并在乙酸异丙酯的合成中表现出了良好的活性。     

One-pot hydrothermal preparation of SBA-15 supported Keggin-type 12-tungstophosphoric heteropolyacid mesoporous material and its bifunctional catalytic performance

In this work, a series of 12-tungstophosphoric acid (HPW) catalysts supported on mesoporous molecular sieves SBA-15 were prepared by a one-pot hydrothermal method and their physical and chemical properties were characterized by various techniques such as fourier transform infrared spectroscopy, powder X-ray diffraction, nitrogen adsorption–desorption and transmission electron microscopy. It has been found that all the catalysts retained the mesopore structure of SBA-15 and the primary Keggin-type structure of heteropoly acid. The surface areas and pore volumes of HPW-SBA-15 decreased with the increase of HPW heteropoly acid loadings. HPW units were mostly encapsulated inside the mesopores of SBA-15. The prepared catalysts showed excellent multifunctional catalytic properties. Their bifunctional catalytic performances were examined by photo-catalytic degradation of rhodamine-B dye and microwave-catalytic synthesis of isoamyl acetate. The sample with 20 wt% loading of 12-tungstophosphoric acid was found to be more active than the other catalysts under the photo and microwave-catalytic reaction conditions. Accordingly, reasons for the catalytic activity difference were simply explicated by the effect of HPW concentration on the physicochemical characteristic of HPW-SBA-15 catalysts such as surface areas, porosity, and mesostructure.     

水热法合成SBA-15负载杂多酸催化纤维素水解加氢

采用水热一步法在介孔SBA-15载体上负载杂多酸,并进一步负载金属Ru制备具有酸性和加氢性能的双功能催化剂。用BET、XRD、TEM、ICP、NH₃-TPD对其结构性质进行表征。考察了反应时间和反应温度对纤维素催化反应的影响。在190 ℃、16 h,5 MPa H₂的条件下,纤维素转化率达到55.2%,山梨醇的收率为36.8%。催化剂的循环使用表明杂多酸在载体上能够稳定存在,不易流失。制备的双功能催化剂具有很好的稳定性和催化活性。     

介孔Fe2O3/SBA-15催化臭氧氧化含酚废水

含酚废水来源广泛自然条件下难以去除,酚类物质毒性大对生态环境和人类生活健康造成了较严重的影响。本文选取了有机废水处理中较为高效的臭氧催化氧化技术,使用臭氧氧源曝气产生大量的含氧自由基,催化氧化降解酚类有机物,同时对活性中心载体进行了优化,选取制备了一类水热稳定性好及机械强度高的多孔材料,使用这些多孔材料对活性中心Fe₂O₃进行了再组装,合成了一系列表面富集Fe₂O₃的SBA-15介孔薄膜材料,由于SBA-15材料较大的比表面积、丰富的孔隙结构、高度分散的活性中心,在臭氧催化氧化含酚废水中取得了较好效果。苯酚溶液初始浓度为100mg/L (COD 238mg/L)、Fe₂O₃(5)/SBA-15催化剂投加量为30g、臭氧气体流量为2mg/min、废水HRT为5min、流量为0.8L/h的条件下,该催化剂能高效连续稳定运行500h不易失活,其COD去除率仍能保持在65%以上,催化剂活性依然保持在83%以上。Fe₂O₃/SBA-15类介孔催化材料在深度处理含酚废水中具有工业化应用潜质。     

B–SBA-15–SO<Subscript>3</Subscript>H: a versatile mesoporous catalyst

Novel approach was developed towards the synthesis of heterogeneous mesoporous B–SBA-15–SO₃H acid catalysts. That is: B–SBA-15 materials were hydrothermally synthesized by using three different boron sources (boric acid, trisiopropylborate and potassium borohydride) and then post-synthetically functionalized with sulfonic acid to test their catalytic activity for the esterification of propionic acid with methanol. Mesoporous and amorphous character of the materials as well as the incorporation of the boron into the framework were verified by XRD, N₂-adsorption/desorption, ICP–OES, SEM and FT-IR techniques. All of the boron incorporated acid catalysts showed better activity than pure SBA-15–SO₃H for methyl propionate synthesis. Combining the advantageous of hydrothermal synthesis and post functionalization, the obtained B–SBA-15–SO₃H catalysts should present versatile catalytic properties in terms of both catalytic activity and reusability. Boron incorporation and post functionalization encourage the structural configuration, since the grafted catalytically active groups may experience similar environments and be isolated from each other.     

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.     

AI-SBA-15介孔分子筛的制备及应用进展

介孔分子筛SBA-15通过化学改性,可将一些官能团引入到其骨架中改善催化性能,其中以铝改性效果最好,铝改性后的SBA-15介孔分子筛的水热稳定性及酸性明显提高。介绍了A1-SBA-15介孔分子筛的合成及应用现状,展望了介孔分子筛A1-SBA-15未来的发展方向。     

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.     

Effect of support morphology and Pd promoter on Co/SBA-15 for Fischer–Tropsch Synthesis

An influence of support morphology and Pd promoter on physicochemical properties and catalytic performance of Co/SBA-15 in Fischer–Tropsch Synthesis (FTS) was investigated. SBA-15(M) from a hydrothermal synthesis with decane addition had smaller particle size, larger pore size and shorter cavity length which enhanced the dispersion of cobalt oxides, eased diffusion of reactants and improved the FTS performance. 10Co/SBA-15(M) provided the highest and most steady conversions of CO and H₂ with the highest yield of C₅–C₉ products. The addition of Pd enhanced the reduction of cobalt oxides but produced more methane and light paraffins.     

介孔分子筛SBA-15表面改性对脂肪酶固定化的强化作用

引言 脂肪酶可以催化酯水解或醇解、酯合成、酯交换、多肽合成及高聚物合成等多种有机反应,已被广泛应用于食品、精细化工及制药工业中[1].作为重要的生物催化剂,脂肪酶应用的有效性和经济性很大程度上取决于酶的固定化.     

Highly active recyclable SBA-15-EDTA-Pd catalyst for Mizoroki-Heck,Stille and Kumada C–C coupling reactions

Highly efficient SBA-15-EDTA-Pd(11) heterogeneous catalyst was synthesized by covalent anchoring Pd-EDTA complex over organo-modified surface of SBA-15. SBA-15-EDTA-Pd(11) catalyst was found to exhibit excellent catalytic activity in appreciable yield for Heck, Stille and Kumada cross-coupling reactions. Catalytic system exhibited excellent activity for completion of reaction, isolation, Pd loading (0.87 mmol%) and yields of products as compared to earlier reported heterogeneous supported Pd catalysts. Covalently anchored heterogeneous SBA-15-EDTA-Pd(11) catalyst can be recycled for more than five times without noticeable loss in activity and selectivity.     

Short channeled Zr-Ce-SBA-15 supported palladium catalysts for toluene catalytic oxidation

Short channeled Zr-Ce-SBA-15 (ZCS) mesoporous materials were synthesized through hydrothermal routes without addition of mineral acids. 0.5 wt.% palladium was loaded on ZCS and SBA-15 via an ethanol reduction approach. Pd/ZCS possesses unique hexagonal platelet morphologies with short channels running parallel to the thickness in the range of 400–500 nm, while Pd/SBA-15 has a fibrous macrostructure with channels at the micrometer scale. Palladium species present in supports as well dispersed PdO nanocrystals with diameter of ca. 5–6 nm. Comparing with Pd/SBA-15, Pd/ZCS shows enhanced catalytic activity for toluene oxidation, which is ascribed to short channeled supports facilitating the molecular diffusion.     

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.     

SBA-15固载酸性离子液体催化酯化反应性能

为了减少离子液体用量及解决催化剂分离问题,采用键合法制备了以SBA-15为载体的固载化离子液体催化剂[C₃SO₃HCP]HSO₄/SBA-15,通过FT-IR、TG、XRD、BET和TEM分析了催化剂的结构和稳定性。并将其应用于催化丁二酸酐和乙醇的酯化反应。结果表明:[C₃SO₃HCP]HSO₄被成功固定在SBA-15上,且具有较高的热稳定性和催化活性,克服了非均相催化剂活性不高与均相催化剂难以分离的不足。在催化剂用量为反应物总质量的5%、n(C₄H₄O₃):n(C₂H₅OH)=1:3,反应温度80℃;反应时间4 h、带水剂用量为反应物总质量的30%的条件下,酯收率达93.7%,且该催化剂循环使用8次后,仍具有较高的催化活性。此外,还考察了以[C₃SO₃HCP]HSO₄/SBA-15为催化剂催化合成系列酯也获得了较高的酯收率,且易于与产物酯分离。     

SBA-15负载杂多化合物在苹果酯合成中的催化性能

用浸渍法制备了一系列中孔二氧化硅分子筛SBA-15负载的磷钨酸(PW)及其铯盐和钾盐催化剂,考察了其在乙酰乙酸乙酯与乙二醇缩合制苹果酯反应中的催化性能, 并以N2吸附,Hammett指示剂和FT-IR等手段表征了催化剂的物化性质, 在水处理试验中考察了催化剂的稳定性,溶脱到水中的杂多化合物浓度用紫外可见分光光度仪测定.结果表明,在合成苹果酯的反应中,当PW的负载量低于30%,杂多酸盐负载量低于20%时,固体催化剂无活性;催化剂在反复使用过程中活性下降的量与活性组分在极性体系中的溶脱量成对应关系,说明催化剂活性下降的主要原因是杂多酸(盐)活性组分的流失造成的,而负载磷钨酸铯盐良好的催化稳定性来源于磷钨酸铯盐的难溶脱性.     

Enhanced ketalization activity of cyclohexanone and ethanediol over immobilized ionic liquid in mesoporous materials

Three different mesoporous molecular sieves, including MCM-41, MCM-48, and SBA-15, were synthesized by hydrothermal process and characterized by XRD, BET and TEM. The chlorine-aluminate acidic ionic liquid of 1-butyl-3-methylimidazolium chloride-aluminum chloride ([Bmim]Cl-AlCl₃, denoted as Al-ILs) was prepared by two-step method. The immobilized ionic liquid (SBA-15/Al-ILs, MCM-41/Al-ILs, MCM-48/Al-ILs) was prepared through impregnating Al-ILs. The structures of composite catalysts were characterized by XRD, BET, FT-IR, TEM and XPS. The amounts of aluminum present in the resulting composite catalysts were detected by ICP-AES to calculate the amount of AL-ILs impregnated. The ketalization between cyclohexanone and ethanediol was used as the model reaction to test the catalytic activities of the composite catalysts. The effects of molar ratio of the reactants, reaction time, the catalyst dose, as well as the addition of cyclohexane were discussed in detail. Also, catalytic activities of three catalysts with different pore sizes were compared. Under comparable conditions, the SBA-15/Al-ILs composite catalyst exhibited much high catalytic activity and gave a maximum yield that was ca. 85.1%.