Characterization and catalytic performance of mesoporous molecular sieves Al-MCM-41 materials

Mesoporous Al-MCM-41 materials of different Si/Al ratios have been synthesized and characterized by X-ray powder diffraction, ²⁷Al and ²⁹Si MAS NMR, differential thermogravimetric analysis, N₂ adsorption measurements, FT-IR and catalytic cracking of alkanes. The experimental results show that the incorporation of aluminium into the framework of MCM-41 has a great effect on the degree of long-distance order, the surface acidities and the mesoporous structures of the materials. With increase of the aluminium content, the amounts of tetrahedral framework aluminium and the acid sites on the samples increase, but the acid strength decreases. Al-MCM-41 materials exhibit high activity for n-C₁₆ ⁰ cracking and good selectivity for producing low carbon alkylenes, particularly for i-C₄ ⁼.     

Synthesis of Fe,Co, and Mn substituted AlPO-5 molecular sieves and their catalytic activities in the selective oxidation of cyclohexane

Fe, Co, and Mn substituted AlPO-5 molecular sieves, including FeAPO-5, CoAPO-5, MnAPO-5, FeCoAPO-5, FeMnAPO-5, and CoMnAPO-5 were synthesized by hydrothermal method and characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), nitrogen adsorption, and Fourier transform infrared (FT-IR) spectroscopy. The lattice expansions were observed with Fe, Co, and/or Mn substitution of Al atom in AlPO-5. The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol (K/A oil) with molecular oxygen was studied over these catalysts at the reaction temperature of 403 K. The higher activities of the multi-metal substituted AlPO-5, compared to that of single metal substituted AlPO-5, were observed. The underlying reason for the superior activity of the multi-metal substituted AlPO-5 was analyzed.     

介孔分子筛的功能化制备及催化性能研究进展

介绍了介孔分子筛经杂原子取代,引入酸功能、氧化还原功能;经有机－无机嫁接（杂合）,引入聚合催化功能、酸催化功能、手性催化功能;经修饰的介孔分子筛,用作固定化酶催化剂的载体;作为催化剂的载体,用于负载过渡金属及其氧化物和制备负载化的固体酸催化剂。综述了介孔分子筛经功能化制备及催化性能的研究进展。     

含钛介孔分子筛的合成与催化性能

论述了含钛介孔分子筛的水热合成、室温合成、微波合成和选择不同模板剂与嫁接法等合成方法及其特点。对含钛介孔分子筛的表面修饰与改性技术进行了概述。总结了含钛介孔分子筛在催化氧化、烯烃环氧化、羟基化和光催化等反应中的催化性能。指出今后的研究方向是:高水热稳定性含钛介孔分子筛的合成方法;通过对含钛介孔分子筛进行表面修饰,制备出具有独特性能的催化材料;含钛介孔分子筛在光催化及其他催化反应中的催化作用机理。     

Synthesis and catalytic properties of substituted AlPO4-31 molecular sieves

Molecular sieve AlPO₄-31 and substituted analogues (MnAPO-31,SAPO-31, MnAPSO-31) have been tested for their catalytic properties in the isomerization of 1-butene over 6 h time on stream at 743 K. The conversion of 1-butene proceeds selectively by either double bond or skeletal isomerization. MnAPSO-31 with a molar MnO/P₂O₅ ratio adjusted to 0.01 yields the highest percentage of isobutene whereas the parent AlPO₄-31 leads almost completely to a double bond shift with only minor skeletal isomerization. The results are related to the acidity characteristics that were determined by ammonia thermodesorption. Deactivation is accompanied by a loss of selectivity for the skeletal isomerization.     

改性介孔分子筛上直馏柴油催化氧化吸附脱硫研究

合成了磷钨酸改性的SBA-15介孔分子筛,将其用于直馏柴油脱硫,能够实现催化氧化吸附脱硫一步完成,考察各操作条件对脱硫结果的影响,得出最佳操作条件为：氧化剂用量(以氧原子与硫原子物质的量比计）即n(O)∶n(S)=1.28,催化剂用量为柴油质量的5.36%,反应温度为70 ℃,在最佳条件下对反应前后的柴油做硫分布分析,结果表明,沸点小于320 ℃的各类含硫化合物均能有效脱除,直馏柴油的脱硫率达80%。     

Niobium rich SBA-15 materials – preparation, characterisation and catalytic activity

Hexagonally ordered mesoporous niobiosilicates of SBA-15 type were synthesised by a new synthesis route in which the use of hydrochloric acid was avoided. This route allowed the incorporation of much higher amounts of niobium into the mesoporous network (Si/Nb between 15 and 5) as compared to the conventional method of preparation. The location of niobium was determined by UV–Vis and XRD techniques. The latter combined with N₂ adsorption measurements allowed the estimation of texture/structure parameters. The high niobium content in the NbSBA-15 had a significant impact on the sulphurisation of methanol leading to the formation of organic sulphur compounds. It is well correlated with the acidity of the materials measured by pyridine adsorption followed by FTIR studies. Such a relationship was not observed for oxidation of methanol and epoxidation of cyclohexene showing that the redox properties are not linear related to the amount of niobium if Si/Nb is equal or below 15 (as applied in this work).     

Al-Z-SBA-15介孔分子筛催化合成丙烯酸正丁酯

采用降解法成功合成Al-Z-SBA-15介孔分子筛,通过XRD、FTIR、Py-FTIR测试手段对样品进行了分析,结果表明,Al-Z-SBA-15具有高度有序的六方介孔结构和表面酸性。以Al-Z-SBA-15为催化剂,在间歇式反应釜中对丙烯酸和正丁醇液相酯化反应进行了研究,最佳反应条件为:n(丙烯酸)∶n(正丁醇)∶n(对苯二酚)=1∶1.4∶0.4,反应温度190℃,反应时间4 h,催化剂用量为丙烯酸质量的6%,在此条件下丙烯酸的转化率最大,为80.94%,催化活性高于纯硅SBA-15和Z-SBA-15。Al-Z-SBA-15分子筛重复使用17次后转化率仍高达72.94%,具有较好的稳定性,是合成丙烯酸正丁酯的一种理想固体酸催化剂。     

Catalytic behavior of vanadium substituted mesoporous molecular sieves

A series of V-MCM-41 samples with different pore sizes has been systematically investigated with both gas and liquid phase reactions. Methanol oxidation has been performed in the gas phase on these catalysts. Turnover frequencies are normalized by oxygen uptake measured under reaction conditions. A strong effect of pore size on the catalytic activity was observed in the form of a “volcano curve” and may be correlated with a variation in the local bond angle of Si–O–V. Considering this effect, the catalytic activity may be ‘tuned' to maximum by varying the pore size. As expected, the same effect was observed in the liquid phase oxidation of cyclohexene. In order to interpret the pore size effect, the reaction rates of both the gas phase and liquid phase oxidation were then correlated with the variation of edge energies of V K-edge XANES on these MCM-41 catalysts. Additional reactions were performed in the liquid phase to compare the activity of V-MCM-41 with that of crystalline vanadium and titanium silicalite zeolites. The possible causes of the difference in the catalytic behaviors of these materials is also discussed.     

Vanadium, niobium and tantalum modified mesoporous molecular sieves as catalysts for propene epoxidation

SBA-3 mesoporous molecular sieves doped with transition metal ions (Fe, V, Nb and Ta) have been applied for selective oxidation of propene towards propylene oxide in the presence of N₂O as an oxidant. The kind and amount of applied modifiers significantly affected the catalytic activity. V/SBA-3 was found to be the most active among the catalyst under study. In spite of relatively high selectivity towards propylene oxide (reaching up to 23%), the main oxidation product was still propionaldehyde. Surprisingly, CO_x was not formed over V, Nb and Ta modified SBA-3 catalysts. Additional modification of V containing samples (V/SBA-3) with iron complexes resulted in the further increase in the catalysts activity for epoxidation reaction. A PO selectivity of about 20% could be achieved at a propylene conversion of 17% over mixed Fe/V/SBA-3 catalytic system.     

酞菁铜/介孔分子筛复合催化剂催化氧化巯基乙醇的研究

采用浸渍法将α-八-(异戊氧基)酞菁铜分别负载在SBA-15和MCM-41介孔分子筛上,制备了CuPc/SBA-15和CuPc/MCM-412种复合催化剂。通过紫外-可见吸收光谱、红外光谱和N2吸附方法对催化剂的结构和组成进行了表征。测试了2种催化剂对巯基乙醇的催化氧化性能,并考察了温度对催化氧化活性的影响。实验结果表明,在pH=11时,CuPc/SBA-15催化氧化巯基乙醇的转化率高于CuPc/MCM-41;随着温度的升高,CuPc/SBA-15对巯基乙醇的转化率逐渐增大,并计算了CuPc/SBA-15催化反应在25℃时的活化能Ea为30.50kJ/mol。     

Fe-SBA-16介孔分子筛的制备及其催化苯酚羟基化反应性能

以正硅酸乙酯为硅源,F127为模板剂,采用水热合成法直接合成不同铁含量的Fe-SBA-16分子筛。通过X射线衍射、N₂物理吸附-脱附、红外光谱、紫外-可见漫反射光谱等分析手段对催化剂的结构进行表征。研究了Fe-SBA-16在以H₂O为溶剂,H₂O₂为氧化剂的苯酚羟基化反应中的催化活性并考察了不同的反应条件（Fe含量、反应温度、反应时间、催化剂用量、反应物配比）对催化性能的影响。结果表明,在一定铁含量的条件下合成出的Fe-SBA-16样品均保持了SBA-16介孔分子筛的立方笼状介孔结构和高的比表面积,且Fe被成功地引入到SBA-16骨架上。当Si/Fe=30时,Fe-SBA-16催化剂表现出良好的催化活性和选择性。反应温度为65℃,反应时间为2h,苯酚：双氧水为1：0.4时催化活性最好,苯酚的转化率为30.8%,邻苯二酚与对苯二酚的选择性分别为64.3%与30.5%。     

含Ni介孔分子筛的合成及其对苯加氢催化性能

采用水热法合成出不含镍和含镍的硅基介孔分子筛.利用XRD、FT-IR、TPR、TEM和比表面孔径测定等手段对样品进行了表征.结果表明：合成出有序性好的介孔分子筛（MCM-41）,550 ℃焙烧可以将模板剂有效去除,所合成介孔分子筛负载Pt后介孔有序性降低,但是介孔结构仍然存在.苯催化加氢反应研究表明：不含Ni的介孔分子筛不具有加氢活性,当将其负载Pt后具有苯加氢催化活性;含Ni介孔分子筛本身具有苯加氢活性,含Ni介孔分子筛负载Pt后苯加氢催化活性有较大的提高,所有样品的环己烷选择性都接近100 %,说明含Ni介孔分子筛可以直接作为苯加氢反应的催化剂或作为苯加氢催化剂良好的载体.     

Synthesis,characterization and catalytic properties of hexagonal mesoporous vanadium aluminophosphate molecular sieves

Novel vanadium containing hexagonal mesoporous aluminophosphate molecular sieve (VHMA) have been synthesized. XRD and TEM analysis confirm the phase purity of the synthesized samples. FT-IR analysis suggests the incorporation of V⁴⁺ in the aluminophosphate framework. ESR, UV–Vis spectroscopic techniques and cyclic voltammetric studies confirm the incorporation of vanadium and reveal its presence of tetrahedral and square pyramidal environments in the as-synthesized samples. Cyclic voltammetry reveals the presence of two redox couples in VHMA. This catalyst is found to be a good oxidation catalyst.     

Characterization and synthesis of Ce-incorporated mesoporous molecular sieves under microwave irradiation condition

Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized by microwave irradiation method from sodium silicate and ammonium cerium (IV) nitrate precursors and using cetyltrimethyl ammonium bromide (CTAB) as template. The resulting samples were characterized by means of XRD, TEM, FT-IR, UV-Vis, XPS and N₂ physical adsorption, respectively. The effect of the Si/Ce molar ratio on the textural properties of CeMCM-41 was investigated. The results reveal that the CeMCM-41 was successfully synthesized. The resultant mesoporous materials have specific surface areas in the range of 602–1,216 m²/g and pore sizes in the range of ca. 2.6–2.9 nm. The structural properties are related to the amount of cerium incorporation. The surface area and pore volume of the resulting CeMCM-41 were gradually reduced as the cerium content in the sample increased, and the mesoporous ordering diminished.     

Transition metal substituted derivatives of cubic MCM-48 mesoporous molecular sieves

Mesoporous Ti-, Cr- and V-substituted derivatives of the cubic silica molecular sieve MCM-48 have been hydrothermally synthesized at 373 K by an electrostatic assembly pathway using cetyltrimethylammonium cation as the templating agent. The transition metal substituted products all exhibit improved crystallinity and a narrower pore size distribution relative to the pristine molecular sieve. Transition metal substitution caused an enlargement of the cubic unit cell as well as an increase in the degree of crosslinking in the mesopore walls. The coordination of V-sites in the meso-structure is exclusively tetrahedral, as judged by NMR spectroscopy. These sites as well as those of Ti and Cr sites are active and selective for the peroxide oxidation of styrene and methyl methacrylate to benzaldehyde and methyl pyruvate, respectively.     

Selective catalytic oxidation of aniline to azoxybenzene over titanium silicate molecular sieves

The oxidation of aniline using aqueous H₂O₂ and titanium silicates, TS-1 and TS-2 as catalysts was carried out in a batch reactor in the temperature range 333–353 K. TS-1 catalyzes aniline selectively to azoxybenzene and is superior to TS-2. The influence of different solvents, concentration of H₂O₂ and the catalyst in the reaction mixture on the conversion and product distribution has been studied. Acetonitrile is a suitable solvent in this reaction, while acetone is not. For the TS-1 catalyzed oxidation reaction,t-butyl hydroperoxide is not a suitable oxidant. At optimum conditions, a H₂O₂ efficiency of about 100% for aniline conversion is obtained with a selectivity of 97% to azoxybenzene in the product.     

新型磷酸铈铝分子筛的合成

本实验以拟薄水铝石,正磷酸,碳酸铈为原料,三乙胺为模板剂,采用水热合成法合成磷酸铈铝分子筛（CeAPO-5）。利用XRD,SEM,BET等方法对CeAPO-5分子筛进行了表征。结果表明合成的CeAPO-5分子筛具有规整的六方棱柱晶体外形,杂原子Ce的引入未引起分子筛的骨架阳离子原子Al和P的配位环境和结构类型的改变。     

煤系高岭土制备Fe-MCM-41介孔分子筛及其氨选择性催化还原NOx

以煤系高岭土、十六烷基三甲基溴化铵（CTAB）、硝酸铁等为原料,通过水热法合成不同Fe含量的六方介孔分子筛Fe-MCM-41。通过傅里叶变换红外光谱、N2吸附脱附、高分辨透射电子显微镜对催化剂进行表征,并以氨为还原剂研究其选择性催化还原NO活性以及反应条件（包括Fe掺量、反应温度、空速、氨氮比和O2浓度等）对催化性能的影响。结果表明,Fe成功进入MCM-41介孔材料的骨架内,Fe-MCM-41介孔分子筛BET比表面积为980.2～596.8 m2/g,孔容积为0.95～0.60 cm3/g,平均孔径在3.90～3.45 nm。随着铁掺杂量的增加,介孔结构的有序度下降。当n(Fe)/n(Si)=0.05、空速为5000 h?1,Fe-MCM-41催化剂在350 ℃反应时NO转化率最高,可达90.7%;且当氨氮比为1.1和O2含量为2.5%时,催化剂能保持较高的活性。