Catalysis Over Pore-Expanded MCM-41 Mesoporous Materials

Pore-expanded MCM-41 (PE-MCM-41) silica was obtained via a two-step strategy consisting of synthesis of MCM-41 in the presence of cetyltrimethylammonium cations (CTMA⁺) followed by hydrothermal treatment in the presence of an aqueous suspension of dimethyldecylamine (DMDA). It is believed that the two surfactants self-organize into concentric cylinders comprised of an inverted DMDA micelle within a regular CTMA⁺ micelle. The amine head groups point towards the pore center, thus creating a hydrophilic channel within the pores. Selective extraction of DMDA afforded PE-MCM-41E, a highly porous material with hydrophobic surface. Calcination of as-synthesized PE-MCM-41 or PE-MCM-41E gave rise to PE-MCM-41C which exhibits a unique combination of large pores (up to 20 nm), large pore volume (up to 3.5 cm³/g) and large surface area, often exceeding 1000 m²/g. All three mesophases were used as starting materials for the development of innovative catalysts and adsorbents. Moreover, post-synthesis alumination of PE-MCM-41 and PE-MCM-41C led to novel large pore aluminosilicates with different Si/Al ratios, which provided new opportunities in acid and bifunctional catalysis. This contribution is an overview of the catalytic applications of pore-expanded mesoporous silica and aluminosilica.     

介孔分子筛MCM-41的合成探索

以正硅酸乙酯(TEOS)为硅源、十六烷基三甲基溴化铵(CTAB)为模板剂,利用水热合成法制备了介孔氧化硅MCM-41,并采用TEM、XRD、N2吸附-脱附等测试手段对产物进行了表征。结果表明,合成的介孔材料为高质量的MCM-41。     

Mechanical Stability of Mesoporous Materials, MCM-48 and MCM-41

The structural collapse of mesoporous molecular sieves, MCM-48 and MCM-41 materials by mechanical compression was found to occur mechanochemically through hydrolysis of Si–O–Si bonds. Their ordered structures were retained by compressing the well-dried samples under dry N2. Trimethylsilylation of mesoporous materials proved effective in eliminating their instability to compression through enhancing hydrophobicity.     

Catalytic epoxidation of unsaturated alcohols on Ti-MCM-41

The catalytic epoxidation of a series of unsaturated terpenic alcohols was carried out on titanium-containing MCM-41 mesoporous materials with tert-butylhydroperoxide. A direct comparison between in-framework Ti-MCM-41 and Ti-grafted MCM-41 showed a better performance of the latter, even if the difference between them becomes lower as the alcoholic group approaches the C=C double bond. At 358 K and in both acetonitrile and ethyl acetate, the epoxidation rate of the double bond is ruled, on these catalysts, mainly by electronic factors, which cause the preferential oxidation of internal unsaturations instead of the terminal ones. It is also governed by the OH-function position, so that, particularly in ethyl acetate, the closer the hydroxyl group to the unsaturation, the higher is the conversion rate of the terpene.     

反应条件对环己醇低温脱氢过程的影响

在固定床反应器中,采用Cu系催化剂研究了环己醇低温脱氢合成环己酮的反应,考察了反应温度、反应压力、空速和原料组成对环己醇低温脱氢转化率和选择性的影响。确定较佳的反应条件为:反应温度264～272℃,反应压力为常压,空速0.6～0.8 h~(-1),还应控制原料中环己酮和杂质的含量。在264℃、常压、空速0.8 h~(-1)的条件下,环己醇转化率为65.6%,环己酮选择性为99.0%。     

MCM—41中孔分子筛的研究和开发

介绍了近期国内外中孔分子筛ＭＣＭ－４１的研究情况,阐述了其合成机理并简述了其性能和应用。     

新型介孔材料MCM-41的研究进展

从合成和表征等方面介绍了新型介孔材料 MCM- 41的研究进展 ,讨论了影响材料结构 ,孔径和稳定性的因素。     

Ti-MCM-41分子筛催化剂的合成、表征及催化性能

以正硅酸四甲酯为硅源,钛酸四异丙酯为钛源,在异丙醇和水的混合溶液中室温下合成了Ti-MCM-41介孔分子筛,采用TEM、N 2吸附-脱附、XRD、UV-Vis和Raman等研究了分子筛的结构特性。并以过氧化氢异丙苯为氧化剂,考察了硅烷化处理后的Ti-MCM-41分子筛催化剂在丙烯环氧化反应中的催化性能。结果表明,与骨架外六配位钛物种相比,骨架内四配位钛物种活化有机过氧化物的能力更强,速率更快;四配位钛物种是环氧丙烷生成的活性物种,而六配位钛物种的存在则会导致反应副产物的生成。合成时添加适量的异丁醇可有效促进钛物种进入分子筛骨架中,并增大比表面积和孔体积,进而改善Ti-MCM-41催化剂的丙烯环氧化催化性能。性能最佳的催化剂上过氧化氢异丙苯转化率可达94.7%,环氧丙烷选择性可达95.8%。     

Ti-MCM-41分子筛催化剂的表面硅烷化改性研究

以硅酸四乙酯（TEOS）为硅源,钛酸四丁酯（TBOT）为钛源,阳离子表面活性剂CnTMABr为模板剂,通过水热晶化法合成了含钛中孔分子筛Ti-MCM-41.采用XRD,FT-IR,SEM、N2吸附-脱附等方法对分子筛进行了结构表征,研究了不同硅烷化处理方法对Ti-MCM-41分子筛疏水性及催化氧化性能的影响.结果表明：模板剂CnTMABr碳链长度（n）影响Ti-MCM-41分子筛结构有序度.只有在n =16时所合成的Ti-MCM-41分子筛才具有长程有序结构.经不同硅烷化试剂处理后,Ti-MCM-41分子筛的Si/Ti增大,而比表面积、平均孔径、孔容积均有不同程度降低,但疏水性、催化氧化活性及环氧化物选择性增大.采用TMSCl（氯化三甲基硅烷）的硅烷化效率最高.     

超微粒介孔分子筛Ti-MC M-41的制备及催化氧化乙苯合成苯乙酮和α-苯乙醇

在强酸性及常温常压下 ,以无水乙醇和异丙醇为混合溶剂 ,合成了n(Si)∶n(Ti)分别为 30∶1、5 0∶1和 70∶1的超微粒介孔分子筛Ti MCM 41。经X衍射光谱、Fourier红外光谱 (FTIR)和扫描电镜表征 ,该分子筛具有规则的晶体结构 ,颗粒直径为 0 0 5～ 0 1μm ,在FTIR的 96 0cm-1处表现出Si—O—Ti的特征吸收峰。同时研究了该分子筛在乙苯液相氧化中的催化行为 ,讨论了催化剂及反应条件的影响。结果表明 ,在Ti MCM 41催化下 ,双氧水可以将乙苯氧化为苯乙酮和α 苯乙醇。当催化剂n(Si)∶n(Ti)由 70∶1降至 30∶1,催化剂加入量由 10 0mg增加到 30 0mg ,n(H2 O2 )∶n(乙苯 )由 1 0∶1 0增至 3 0∶1 0 ,反应时间由 1h延长至 10h ,反应温度由 15℃升高到6 0℃时 ,乙苯的转化率分别提高到 3 3倍、1 4倍、2 6倍、1 7倍和 2 2倍。以氯仿、丙酮和甲醇为溶剂时 ,乙苯的转化率分别为 0 6 4%、1 2 7%和 3 5 5 %。     

两种环己醇脱氢催化剂的稳定性比较

对两种用于环己醇脱氢的Cu-Zn 催化剂在100ml 评价装置上1000 小时连续运转的结果进行了比较, 对其还原过程中H₂浓度的变化、各段反应温度的变化、选择性随时间的变化、使用后催化剂的活性对比进行了分析和讨论。     

MCM-41介孔碳材料的合成及其电化学性能

以十六烷基三甲基溴化铵(CTAB)为模板剂,可溶性淀粉(Starch)为碳源,通过软模板法一步合成了高度有序的介孔碳材料。通过热重分析(TG)、X射线衍射(XRD)、N2吸附-脱附和透射电子显微镜(TEM)对材料的结构进行了表征。结果表明:当m(模板剂CTAB)∶m(可溶性淀粉)=1.0∶1.5,650℃焙烧碳化3 h,并用氢氟酸去除二氧化硅后,所得到的MCM-41有序介孔碳材料(OMC-650)的比表面积为985 m2/g,平均孔径为2.5nm,且孔径分布均匀。XRD和TEM分析结果表明,OMC-650具有典型的MCM-41结构特征,有序性良好。以OMC-650作为工作电极,氧化汞为参比电极,铂为辅助电极,用6 mol/L KOH做电解液,测其比电容为150 F/g,且经过1 000次充放电循环后,其比电容仍为138 F/g,为原电容的92%,说明所合成的材料具有良好的电容稳定性。     

常压制备Ti-MCM-41介孔分子筛及其表征

以水玻璃为硅源,四氯化钛为钛源,去离子水为溶剂,EDTA为络合剂,十六烷基三甲基溴化铵(CTAB)为模板剂,常压合成Ti-MCM-41,采用X射线粉末衍射(XRD)、低温N2吸附-脱附试验(77 K)、傅立叶红外光谱(FTIR)、紫外可见光漫吸收光谱(UV-vis)和透射电子显微镜(TEM)等方法表征了合成的介孔分子筛,研究了晶化时间、晶化温度、pH值、Ti含量、煅烧制度对介孔结构的影响.结果表明:pH值和煅烧对产物的影响最为明显;EDTA抑制非骨架钛具有良好的效果;绝大多数的 Ti以四配位状态存在于SiO2网络骨架中.     

Synthesis and Characterization of Al-MCM-41 and Al-MCM-48 Mesoporous Materials

A novel route in the synthesis of Al-MCM-41 and Al-MCM-48, using tetraethoxysilane (TEOS) and sodium aluminate (NaAlO₂) as Si and Al source has been obtained. The effect of surfactant nature and the synthesis conditions such as surfactant/Si ratio and hydrothermal treatment time on the formed mesostructure regularity has been studied. Different methods of template removal have also been evaluated. The samples were characterized by X-ray diffraction, nitrogen physisorption, FT-IR, and solid-state MAS NMR spectroscopy.     

Ti-MCM-41负载酞菁铁光催化氧化脱硫

合成了钛硅分子筛Ti-MCM-41,通过对Ti-MCM-41改性以共价键将带有不同取代基的酞菁铁负载于Ti-MCM-41上制备出Ti-MCM-41负载酞菁铁催化剂,并利用红外光谱、X射线衍射、扫描电镜以及BET氮气吸附-脱附等温线以及紫外-可见吸收光谱对合成的催化剂进行表征。在常温常压下,以Ti-MCM-41负载酞菁铁为光催化剂,空气为氧化剂,己内酰胺四丁基溴化铵离子液体为萃取剂,可见光下催化氧化二苯并噻吩(DBT),采用单一变量法探索该体系的最佳反应条件。结果表明,Ti-MCM-41负载氨基酞菁铁具有较好的光催化活性,且在最佳工艺条件下,DBT的脱除率最高可达95.6%。催化剂重复使用5次后,催化活性没有明显下降。     

环己醇催化脱氢铜基催化剂研究进展

环己酮在工业上有重要的用途,是制备己内酰胺和己二酸的主要中间体。环己醇催化脱氢法工艺制环己酮,具有副反应少、操作容易、低污染等优点,铜被广泛用作这类反应催化剂的活性组分。文章综述了近年来国内外用于环己醇催化脱氢制环己酮的铜基催化剂,最后,结合现存问题提出了今后的研究方向。     

MCM-41介孔碳材料的合成及其电化学性能研究

该文以十六烷基三甲基溴化铵（CTAB）为模板剂,可溶性淀粉(Starch)为碳源,通过软模板法一步合成了高度有序的介孔碳材料。通过热重分析（TG）、X-射线衍射（XRD）、N2吸附-脱附和透射电子显微镜（TEM）等对材料的结构进行了表征。结果表明：当模板剂与可溶性淀粉质量比为m(CTAB):m(Starch)=1.0：1.5,650 ℃焙烧碳化3 h,并用氢氟酸去除二氧化硅后,所得到的MCM-41有序介孔碳材料（OMC-650）的比表面积为985 m2/g,平均孔径为孔径分布均匀,平均孔径为2.5 nm。XRD和TEM分析表明,OMC-650具有典型的MCM-41结构特征,有序性良好。以OMC-650作为工作电极,氧化汞为参比电极,铂为辅助电极,用6 M•L-1 KOH做电解液,测其比电容为150 F/g,且经过1000次循环后,其比电容仍为138 F/g,为原电容的92%,说明所合成的材料具有良好的电容稳定性。     

环己醇脱氢制环己酮催化剂的研究进展

评述了由环己醇脱氢制己内酰胺生产的重要中间体环己酮催化剂的研究与实际应用的进展。重点叙述了目前国内外工业应用催化剂的组成,制备方法,并对其优缺点进行了评述。     

Synthesis, structural characterization and photocatalytic activity of Ti-MCM-41 mesoporous molecular sieves

This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface area, large pore size and well ordered mesostructure, are partially retained in the titania containing materials. Modifying synthesis temperature, it was shown that MCM-41 isotherms are different for temperatures above or under 140°C. UV-VisDR spectroscopy was used to investigate the local environment of Ti sites. The obtained materials were evaluated for the photocatalytic degradation of Rhodamine 6G in aqueous medium. The best photocatalytic activity was found for the sample prepared at higher ageing temperature of 160°C, at which anatase particles were formed.