不同晶粒大小的TS-1沸石的表征及其丙烯环氧化性能

在四丙基溴化铵-正丁胺体系中合成不同晶粒大小的TS-沸石,采用IR、XRD、UV-Vis、SEM、27Al MAS NMR对其进行表征,并以丙烯环氧化反应为探针考察其催化性能。结果表明,当TS-1晶粒的b轴小于1μm时,晶粒变化对丙烯环氧化活性的影响不大;而当b轴大于1μm,县城反应介质中H2O2沈度较高时,随着晶粒的增大,催化剂活性急剧下降,说明此时反应受至明显的扩散限制的影响.     

Epoxidation of Propylene with Dilute H2O2 over Titanium Silicalite Containing Trace Aluminum

Titanium silicalite (TS-1) was successfully synthesized by using TPABr as the template and silica sol as silicon source in a 100 l stainless steel autoclave. IR, XRD, UV--vis, elemental analysis, and ²⁷Al and ³¹P MAS NMR were used to characterize the synthesized products. The results show that the synthesized material has an MFI structure with high crystallinity and large crystal size and two kinds of titanium species. Trace aluminum in silica sol is also incorporated into the zeolite framework. The synthesized TS-1 exhibits high activity in the epoxidation of propylene with dilute H₂O₂ with high selectivity to methyl mono-ethers and low selectivity to propylene oxide (PO). The low selectivity toward PO is due to the residual acidity onto TS-1. The selectivity of PO can reach up to 90% through adjusting the pH of the reaction mixture. Extra amounts of base decrease the H₂O₂ utilization and the H₂O₂ conversion. However, in over acid-treated TS-1 in which part removal of extra-framework titanium takes place, the utilization of H₂O₂ is quite different: for the low Si/Ti ratio of TS-1, the H₂O₂ utilization increases. But the utilization of H₂O₂ does not change for the high Si/Ti ratio TS-1. Thermal analysis shows that the as-synthesized TS-1 exhibits high activity and thermal stability in the calcined range 540-900 °C.     

水热法合成的钛硅分子筛催化性能研究

考察了用不同模板剂和碱源合成的钛硅 （ＴＳ－１） 分子筛在丙烯环氧化反应中的催化性能, 研究了酸处理和晶粒大小及结晶度的影响。结果表明,ＴＳ－１ 分子筛的催化活性高于ＴＳ－２ 分子筛; 用酸处理催化剂会造成环氧丙烷（ＰＯ） 选择性的下降; ＴＳ－１ 分子筛晶粒增大, 环氧化速率下降, 但环氧丙烷选择性上升; ＴＳ－１ 分子筛结晶度上升, Ｈ２ Ｏ２ 转化率和利用率均提高。以较廉价的四丙基溴化铵 （ＴＰＡＢｒ） 为模板剂, 二乙胺、正丁胺或氨水为碱源, 可合成出具有较好催化丙烯环氧化性能的ＴＳ－１ 分子筛。     

Separation characteristics of tetrapropylammoniumbromide templating silica/alumina composite membrane in CO<Subscript>2</Subscript>/N<Subscript>2</Subscript>, CO<Subscript>2</Subscript>/H<Subscript>2</Subscript> and CH<Subscript>4</Subscript>/H<Subscript>2</Subscript> systems

Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide (TPABr)-templating silica sols were coated on tubular alumina composite support ( γ-Al₂O₃/ α-Al₂O₃ composite) by dip coating and then heat-treated at 550 °C. By using the prepared TPABr templating silica/alumina composite membrane, adsorption and membrane transport experiments were performed on the CO₂/N₂, CO₂/H₂ and CH₄/H₂ systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport mechanism in the membrane. In the single gas systems, adsorption characteristics on the α-Al₂O₃ support and nanoporous unsupport (TPABr templating SiO₂/ γ-Al₂O₃ composite layer without α-Al₂O₃ support) were investigated at 20–40 °C conditions and 0.0–1.0 atm pressure range. The experimental adsorption equilibrium was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The α-Al₂O₃ support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO₂ and CH₄. While the adsorption rates in the unsupport showed in the order of H₂> CO₂> N₂> CH₄ at low pressure range, the permeate flux in the membrane was in the order of H₂≫N₂> CH₄> CO₂. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed gases, such as CO₂/H₂ and CH₄/H₂ systems. Although light and non-adsorbable molecules, such as H₂, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as CO₂ and CH₄, showed a higher separation factor (CO₂/H₂=5-7, CH₄/H₂=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport. And these results could be explained by surface diffusion. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

两种钛硅分子筛合成体系的比较

分别在四丙基溴化铵(TPABr)-正丁胺体系和以四丙基氢氧化铵(TPAOH)为模板剂的修正经典合成法体系中合成了钛硅分子筛TS-1，对比了两个体系的晶化过程，并对所获得的TS-1进行了XRD、IR、SEM表征和催化反应性能评价。结果表明，在TPABr-正丁胺体系中合成TS-1，晶化速率较慢，母液pH值先降后升；而以TPAOH为模板剂合成的TS-1，晶化速率很快，母液pH值先升后降。对比两种分子筛的XRD、IR表征结果，未发现明显的差别；但SEM观察结果表明，TPABr-正丁胺体系合成的TS-1晶粒较大。在丙烯环氧化反应中，两种分子筛均具有较好的催化性能；在苯酚羟基化和苯乙烯氧化反应中，以TPAOH为模板剂合成的分子筛具有较高的活性。采用TPABr-正丁胺体系合成时，由于体系的碱度较低，液相中硅酸盐的浓度较低，因而所得TS-1比修正经典合成法体系所得的晶粒为大。这种廉价的较大晶粒的TS-1可以满足扩散限制较小的丙烯环氧化反应的要求。     

TS分子筛的催化氧化性能研究Ⅳ.TPABr对TS-1分子筛晶粒度和环氧化性能的影响

用自制的四丙基溴化铵 （ＴＰＡＢｒ） 部分取代四丙基氢氧化铵 （ＴＰＡＯＨ） 为模板剂, 在Ｎａ＋ 离子 （含量２０～３０μｇ／ｇ）存在下, 合成出了结构优良的ＴＳ－１ 分子筛。在丙烯Ｈ２Ｏ２ 氧化制环氧丙烷反应中,考察了合成的ＴＳ－１ 分子筛的催化活性, 催化剂的预处理、用量、利用次数、再生和反应温度与时间对反应的影响。研究表明, 不同的模板剂组成和合成条件明显影响分子筛的晶粒大小。晶粒度为０．４～０．７μｍ 的ＴＳ－１ 分子筛经１０％ ＮＨ４Ａｃ 预处理后, 对丙烯的环氧化具有优良的催化性能。室温下, 用０．４ｇ 催化剂, 以甲醇／水为溶剂, 反应１ｈ, Ｈ２Ｏ２ 转化率和对环氧丙烷的选择性分别可达６５％ ～８０％ , ８５％ ～９０％ 。     

廉价原料合成的钛硅分子筛的热稳定性能的研究

以四丙基溴化铵（TPABr)为模板剂 ，正丁胺为碱源，水热条件下合成了钛硅分子筛TS－1，采用IR，XRD，UV－Vis,SEM等对其进行了表征，并考察了丙烯环氧化性能，采用在空气中程序升温焙烧的方式考察了其热稳定性，采用XRD，IR，UV－Vis光谱详细考察了不同焙烧温度下钛硅沸石中钛的存在环境，结果表明，所合成的钛硅沸石与标准方法合成的钛硅沸石相比，主要差异在于晶粒尺寸与非骨架钛类型，即以TPABr为模板剂合成的晶粒较大，且其中的非骨架钛为非锐钛矿型TiO2，廉价原料合成的TS－1具有较好的热稳定性能，当焙烧温度低于1100℃时，IR谱图中960cm^-1左右代表钛进入骨架的特征峰的强度变化不大，UV－Vis谱图中代表非骨架钛的特征峰的信号变化也不大。当焙烧温度高于1100℃时，IR谱图中960cm^-1处的峰强度及峰TPAOH为模板剂合成的钛硅沸石中，非骨架钛转化成锐钛矿型TiO2，廉价原料合成的高钛含量的钛硅分子筛在高温下熔烧时，非骨架钛也转化成金红石型TiO2，但酸处理可以提高其热稳定性能。