环境友好催化体系——钛硅分子筛／H2O2的研究

钛硅分子筛（ＴＳ）／Ｈ２Ｏ２催化体系氧化烃类化合物具有很高的活性,无废物产生,是一个对环境友好的有机合成催化体系。本文就近年来国内外对钛硅分子筛（ＴＳ）的合成、表征方法及其催化性能的研究进展进行了简要的介绍。     

Fe-Zn共改性ZSM-5催化作用下生物质快速热解特性研究

选取木屑和花生壳作为原料进行生物质热解,研究有机产物分布,催化剂使用Fe、Zn两种金属元素进行改性。通过X射线衍射（XRD）、扫描电镜（SEM）、傅里叶红外（FT-IR）、比表面积测试（BET）对Fe-Zn改性的ZSM-5进行分析。使用闪速裂解-气质联用仪（PY-GC/MS）对原料进行热解,探究生物质催化热解的产物分布变化。催化剂的使用使得芳烃类产物产率获得较大提升,在木屑热解中,Fe负载的分子筛催化获得了酚类的最高产率,比ZSM-5催化热解产率提升18.30%。金属改性催化剂在花生壳热解中,大幅提升了芳烃类产物产率,其中Zn负载催化剂芳烃类产物产率最高,Zn负载催化热解比直接热解的酚类产率降低了18.92%。Zn负载催化获得了最低的酮类产率,与直接热解相比酮类产率降低19.74%,显示出较强的脱羟基效果。此外Zn负载催化和Fe-Zn双金属负载催化在花生壳热解中都大幅降低了酸类产物产率,与直接热解相比酸类产率分别降低了30.46%、36.71%。     

CuZnTiO2/SAPO-34双功能催化剂的设计、制备及其用于CO2加氢制烯烃性能

CO₂加氢经甲醇（含氧中间体）制低碳烯烃工艺路线,可实现成醇、脱水两步反应串联协同进行,打破费托合成产物Anderson-Schulz-Flory（ASF）分布限制,高选择性地制取低碳烯烃。传统甲醇合成Cu基催化剂加氢能力较强,在两步反应中产物以CH₄、低碳烷烃为主。实验设计、制备了CuZnTiO₂/(Zn-)SAPO-34复合催化剂,实现了CO₂加氢在Cu基复合催化剂上高选择性合成C₂～C₄烯烃（约60%）。研究表明,两步反应过程中甲醇体积分数较低（＜6%）,且高温下逆水煤气变换反应严重,导致催化剂酸性变化对产物分布的影响较大。调变两类活性位点比例发现,CH₄的产生与串联反应存在竞争关系,SAPO-34酸量的增加抑制了CH₄的生成,促进串联反应正向进行;合适的酸性有助于生成C₂～C₄烯烃。控制成醇、脱水两类活性位点接触距离可调变烯烃的二次反应,降低加氢能力,改善产物分布。     

含钛分子筛的合成与应用研究进展

对近年来钛硅分子筛的合成方法进行了综述,并简单评述了中孔含钛分子筛的合成技术。讨论了模板剂在分子筛合成过程中的选取和作用机理,模板剂对分子筛孔道大小的影响及结构取向作用。     

Synthesis of a Stable Metallic Niobium Oxide Molecular Sieve and Subsequent Room Temperature Activation of Dinitrogen

Mesoporous niobium oxide was treated at room temperature with bis(toluene) niobium to make a new black material that exhibits metallic properties. The metallic behavior is attributed to low‐valent Nb^II in the walls of the porous structure and is fully supported by strong emissions at the Fermi level, variable temperature resistivity measurements, and temperature‐independent paramagnetism. These materials possess higher conductivities than reported for any molecular sieve and also represent the first example of a metallic oxide‐based molecular sieve. For comparison, the conductivity is almost 10 000 times greater than the highest value measured for an open structured mesoporous material. Treatment at room temperature with dinitrogen leads to formation of a thin nitride coat on the surface. Cleavage of dinitrogen is an extremely rare and important reaction that typically requires very forcing conditions in the solid state (high temperatures in excess of several hundred degrees, argon plasmas, etc.) or low‐valent coordinatively stressed metal centers in the homogeneous phase. This is the first example of a molecular sieve mediating this process and because of the controlled porosity and high surface areas of these materials they are ideal candidates for model studies for nitrogen reduction and catalytic nitrogen incorporation into organic compounds. Since porous materials are often the catalytic support of choice for industrial processes, these materials may lead to the development of commercial nitrogen incorporation processes.     

高稳定性介孔分子筛的合成与表征

以天然黏土和硅酸钠为原料、十六烷基三甲基溴化铵为模板剂,水热法合成了有序性好的高稳定性介孔分子筛.用粉末X射线衍射、透射电镜、Fourier变换红外光谱和比表面积孔径分析等方法对所合成的介孔分子筛进行了表征.结果表明:所合成的介孔分子筛的比表面积大于550m2/g,平均孔径为2.72nm.样品经850℃焙烧3 h,100℃水热处理10 d,介孔分子筛的介孔结构没有被破坏,并且热处理使孔发生收缩,比表面积减小,水热处理使介孔的有序性变得更好,天然黏土为原料提高了介孔分子筛的水热稳定性.     

Catalysis: The Key to Waste Minimization

The drive towards greater economic and environmental efficiency in chemicals manufacture has led to a growing need for processes that produce minimal waste and avoid, as much as possible, the use of toxic and/or hazardous reagents and solvents. This has led to a reassessment of many existing technologies. Alternative processes to particular products are compared on the basis of their atom utilization and E factor (kg byproduct per kg product). The use of high-atom utilization, low-salt catalytic processes as clean alternatives to conventional technologies for the manufacture of fine chemicals is discussed. In particular catalytic oxidations and catalytic carbonylations are highlighted using citral, caprolactam, paracetamol, ibuprofen and methylmethacrylate as commercially relevant examples. The question of catalyst recovery and recycling is also addressed, e.g. with the use of redox molecular sieves as solid catalysts for liquid phase oxidations and the use of a water-soluble palladium(0)trisulfonated triphenylphosphine complex, as a catalyst for carbonylation in aqueous media. © 1997 SCI.     

全硅MCM-41中孔分子筛的合成

在碱性条件下,采用水热晶化法,以水玻璃为硅源,表面活性剂十六烷基三甲基溴化铵为结构模板剂,成功合成出全硅MCM－41中孔分子筛。采用X射线衍射分析研究了合成条件(pH值）、凝胶配比（表面活性剂／SiO2、H2O/SiO2）和凝胶后处理条件（老化时间、晶化温度、晶化时间和焙烧温度）对MCM－41结构的影响。结果表明全硅MCM－41的合成条件为pH10.5-12.5,表面活性剂／SiO20.05-0.7,H2O/SiO2 40－200,老化时间长对合成晶形较的全硅MCM－41有利。晶化温度70℃-100℃,晶化时间24小时,焙烧温度540℃－740℃。     

用高性能制氧分子筛变压吸附

对沸石分子筛进行离子交换改性 ,同时严格控制成型活化条件 ,开发出变压吸附空分用系列高性能制氧分子筛。测试其氮、氧静态吸附等温线以及吸附热数据 ,并对数据结果进行分析。这为进一步开发和优化变压吸附制氧过程提供了良好的基础     

咪唑改性MCM-22分子筛的制备及甲烷无氧芳构化性能

以硅溶胶为硅源,环己亚胺为模板剂,在动态条件下利用水热合成法合成了MCM-22分子筛,并在该体系下以咪唑为添加剂合成了咪唑改性MCM-22-I分子筛,考察了咪唑对MCM-22-I分子筛合成的影响,利用FTIR、XRD、SEM、ICP、BET、NH₃-TPD、H₂-TPR和TG/DTG等手段分别对咪唑改性前后分子筛的物化性质进行了表征。结果表明,咪唑改性能够增大MCM-22的比表面积、孔容和酸性,同时可有效降低模板剂HMI的用量。采用等体积浸渍法制备了6Mo/MCM-22和6Mo/MCM-22-I双功能催化剂,在连续流动固定床反应器上,反应温度700℃、反应压力1.01×10⁵Pa（1atm）、空速1500mL/(g-cat·h)的反应条件下,考察了催化剂催化甲烷无氧芳构化合成苯的催化剂性能。结果表明,与6Mo/MCM-22催化剂相比,咪唑改性的6Mo/MCM-22-I催化剂具有更高的择形性能和催化活性,甲烷的平均转化率提高了24.1%,苯的平均生成速率和选择性分别提高了24.3%和10.0%。