共缩聚法制备功能化P(St-MPS)/MCM-41核壳复合微球

以聚(苯乙烯-γ-甲基丙烯酰氧基丙基三甲氧基硅烷)(P(St-MPS))微球为核模版,十六烷基三甲基溴化铵为壳模版,以P(St-MPS)微球、正硅酸乙酯与MPS的混合物为硅源,直接在无皂乳液中通过共缩聚方法合成表面链有碳-碳双键功能基的P(St-MPS)/MCM-41核壳复合微球;采用TEM,XRD和FT-IR对产物进行了表征.结果表明,表面功能化的P(St-MPS)/MCM-41核壳复合微球可以直接在无皂乳液中一步合成,所制备的核壳复合微球粒径约为260 nm,壳层约为10 nm.     

The use of palladium nanoparticles supported with MCM-41 and basic (Al)MCM-41 mesoporous sieves in microwave-assisted Heck reaction

A series of supported catalysts has been obtained by grafting of chemically generated palladium nanoparticles onto basic, Cs⁺ ion-exchanged molecular sieves (Al)MCM-41 and onto the non-basic, parent material MCM-41. Catalytic activity of the catalysts has been investigated in the Heck reaction between bromobenzene and butyl acrylate under microwave irradiation. The activity of the bifunctional catalysts (Pd@Cs⁺-(Al)MCM-41) and the activity of Pd@MCM-41 combined with sodium acetate as an external base were considerably higher under microwave irradiation than activities observed for the same catalytic systems under the conventional heating. The Pd@MCM-41/NaOAc system showed higher conversions than the bifunctional catalysts presumably due to a different nature and accessible amount of the base. On the other hand, microwave irradiation seems to increase the rate of aggregation of the metallic particles and thus also catalyst deactivation as compared with the usual heating.     

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.     

HZSM-5/MCM-41对小球藻催化热解的影响

以HZSM-5/MCM-41为催化剂,在管式炉内对小球藻进行了催化热解研究。考察了HZSM-5/MCM-41复合催化剂中MCM-41的添加比例对小球藻热解产物影响,并采用GC-MS和元素分析对所制取生物油进行了表征。结果表明:与HZSM-5催化剂相比,90%HZSM-5与10%MCM-41混合后生物油中3,7,11,15-四甲基-2-十六烯的选择性最好。羧酸类和含氮物质分别降低12.85%、43.97%,脂肪烃和芳烃的质量分数之和达到50.34%,且不存在硬脂酰胺和油酸腈等物质。根据元素分析可知,10%的MCM-41的引入使生物油含氧量降低23.52%,O/C原子比明显降低,H/C原子比得到提高,热值达到32.995 MJ·k-1,且油品组成与生物柴油接近。热重实验表明,分子筛催化剂失活主要是由于积炭的产生,HZSM-5/MCM-41具有良好的稳定性。随着催化剂用量的增加,生物油热值增加,同时含水量也增多,HZSM-5/MCM-41与小球藻质量比例为1:5时,生物油产率最高。     

MCM-22分子筛的合成研究进展

MCM-22分子筛是一种高硅铝比分子筛,具有独特的晶体结构、高孔容及微孔率、优良的水热稳定性能和酸性性能,在烃类催化裂化、甲苯岐化、芳烃芳构化和烷基化等反应表现出了优异的催化性能,因此引起了科研工作者的极大研究热情。本文综述了MCM-22分子筛的结构特征、合成的影响因素以及在催化反应上的应用。提出了目前MCM-22分子筛合成所存在的问题,并对其今后的主要研究工作进行了展望。     

以聚乙二醇/十六烷基三甲基溴化铵为模板剂制备MCM-41分子筛

通过将聚乙二醇(PEG)直接引入MCM-41分子筛合成模板剂十六烷基三甲基溴化铵溶液中,经脱洗和焙烧处理得到厚孔壁有序介孔材料.选用X射线衍射(xRD)、透射电子显微镜(TEM)和等温吸附(BET)对样品进行了表征,结果显示,添加PEG的合成产物孔壁厚度增加,孔壁厚度可达1.45 nm,孔径尺寸和比表面积减小,有序性降低,低相对分子质量PEG的添加有助于厚孔壁产物生成.     

AlMCM-41介孔分子筛催化合成苯甲酸甲酯的研究

本文以介孔分子筛AlMCM-41为催化剂,采用碳酸二甲酯(DMC)作为酯化试剂与苯甲酸(BA)反应制备苯甲酸甲酯(BA)。反应结果表明,碳酸二甲酯是一种很好的酯化试剂,介孔分子筛AlMCM-41对此酯化反应是高效的催化剂。并且还发现苯甲酸的转化率和苯甲酸甲酯的选择性与催化剂上的Lewis酸位有很大联系。另外本文还讨论了此反应的机理。     

MCM-22分子筛的合成、性质与催化应用

MCM-22分子筛具有独特的晶体结构、适宜的酸性和较高的稳定性,在烯烃与苯烷基化反应、甲烷无氧芳构化、催化裂化、烯烃芳构化及甲苯歧化等方面显示出广阔的应用前景。在总结大量相关研究的基础上,就目前MCM-22分子筛的合成、性质和催化应用方面的研究成果进行了概括和评述。     

SO2-4/TiO2-Al-MCM-41制备及其催化合成戊酸丁酯

选择硅酸四乙酯为硅源,在室温和pH=3.5条件下合成具有较低硅铝比的MCM-41型分子筛。以其为基础载体,采用浸渍和焙烧法制备含钛分子筛型固体超强酸。低温N₂吸附、IR、SEM和XRD分析表明,铝已进入分子筛的骨架中;Hammett指示剂测定表明,酸强度H₀<－14.52。以戊酸丁酯合成为探针反应,考察了催化剂的催化性能。结果表明,反应温度为138 ℃、催化剂用量为反应物总质量的1%、丁醇和戊酸的物质的量比为3∶1条件下,产品转化率达98.5%。