丙烯环氧化反应的研究新进展

综述了不同氧源与丙烯环氧化反应的研究新进展。主要包括:氢氧原位制备过氧化氢丙烯环氧化,直接以分子氧为氧化剂的光诱导环氧化反应以及以臭氧和一氧化二氮为氧化剂的研究。指出开发活性高、选择性好的催化剂是解决问题的关键,并对其应用前景进行了讨论。     

KOH沉淀剂对Ag/TS-1催化剂用于丙烯气相环氧化的影响

采用沉积-沉淀法制备Ag/TS-1催化剂,在423 K、常压条件下用于丙烯气相环氧化反应,研究了碱金属沉淀剂KOH的影响。结果表明,以KOH为沉淀剂、TS-1为载体制备的Ag/TS-1催化剂反应性能最佳,丙烯转化率为1.8%,环氧丙烷选择性为91.7%;K+的存在对反应有促进作用。     

丙烯直接气相氧化过程中Ag/TS-1催化剂上活性银物种的分布

在常压固定床、石英反应器中,以丙烯直接气相氧化反应为探针,考察了硅烷化处理及TS-1中模板剂对Ag/TS-1催化性能的影响.同时,采用UV-Vis、ICP和TEM等手段对其进行了表征.结果表明：在丙烯直接气相氧化过程中,载体TS-1硅烷化后所制备的Ag/TS-1的催化性能增强.通过硅烷化处理负载2%SiO₂,制备的Ag/TS-1的丙烯转化率可达2.1%,环氧丙烷选择性98.4%.用TS-1原粉（含有模板剂）所制备的Ag/TS-1不具有环氧化性能.分子筛内外表面的银物种均具有环氧化性能,但内表面的银物种在丙烯气相氧化过程中起决定性的作用.     

Epoxidation of propylene by air over modified silver catalyst

Epoxidation of C₃H₆ to C₃H₆O by air was studied over a silver catalyst modified with alkali or alkaline earth chloride salts. The catalyst preparation factors and the operational conditions could affect obviously the catalytic epoxidation property of the silver catalyst. It was shown that, as a promoter of the silver catalyst, NaCl or BaCl₂ is more suitable than LiCl or NH₄Cl. The loading of NaCl should be controlled at about 3.8 wt%. Using a feed gas of 10% C₃H₆/air at a space velocity of 1.75×10⁴ h⁻¹, 18.6% C₃H₆ conversion and 33.4% selectivity to C₃H₆O were obtained at 350°C. Using a feed gas of 5% C₃H₆/air at a space velocity of 2.4×10⁴ h⁻¹, 54.0% C₃H₆ conversion and 26.3% selectivity to C₃H₆O were obtained at 390°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ag助剂对丙烯气相环氧化Au/TS-1-B催化剂性能的影响

以堵孔钛硅分子筛（TS-1-B）为载体,通过沉积-沉淀法制备了金催化剂（Au/TS-1-B）和金-银双金属催化剂（Au-Ag/TS-1-B）,考察两个催化剂在丙烯气相环氧化反应中的稳定性,并利用HRTEM、Py-GC-MS和UV-vis DRS等手段对金属颗粒粒径变化、结焦量及结焦种类等进行了表征。结果表明,Ag的引入显著降低了催化剂表面焦类物质总量和结焦中低聚烯烃的相对含量,从而显著提升了催化剂的稳定性。     

H2-O2气氛中丙烯环氧化反应研究进展

对H2-O2气氛中丙烯环氧化反应所采用的催化剂、反应器及操作方式进行了评述.综合分析了所使用的钯(金或银)/钛硅分子筛(或氧化钛)双功能催化剂的各项性能指标以及所采用的反应器型式.结合H2-O2直接合成H2O2所用催化剂,对原位氧化丙烯反应过程进行了系统描述.指出进一步的研究方向是借助反应或分离耦合技术,创造有利于原位生成的H2O2及时进行环氧化而避免分解的操作环境,包括催化剂表面状态、反应器型式、溶剂体系和操作方式,并提出以丙烷路线经脱氢、环氧化是制取环氧丙烷的最佳组合.     

Y型银催化剂宏观动力学研究

采用磁力搅拌内循环无梯度反应器,在2.1 MPa,202.9—257.2℃和气体摩尔分数C2H415.13%—34.61%,O22.27%—8.22%,CO20.57%—7.00%(余为N2)及抑制剂1,2-C2H4Cl20.15×10-6—2.44×10-6条件下,对Y型银催化剂上乙烯环氧化合成环氧乙烷的宏观动力学特性进行了系统实验研究,在前人银催化剂动力学研究成果的基础上构建了适用于Y型银催化剂的双曲型宏观动力学模型方程,并运用单纯型法对动力学实验数据进行了非线性参数估值。统计检验结果表明:该模型方程良好地吻合了实验结果,并通过检验证明其是适宜和可信的。从结果可知,该体系环氧化主反应表观活化能为86.698 k J/mol,完全氧化副反应表观活化能为110.57 k J/mol。     

用于丙烯环氧化反应的金催化剂

以氢气和氧气混合气为氧源的丙烯环氧化反应是金催化剂应用研究的主要反应。综述了金催化剂在丙烯环氧化反应中的载体材料影响、金纳米粒子作用以及金纳米粒子与载体之间的协同作用对催化性能的影响,提出气相直接氧化丙烯生产环氧丙烷尚待解决的技术问题和相应的研究新亮点。     

Uncalcined TS-2 immobilized Au nanoparticles as a bifunctional catalyst to boost direct propylene epoxidation with H2 and O2

Developing stable yet efficient Au–Ti bifunctional catalysts is important but challenging for direct propylene epoxidation with H₂ and O₂. This work describes a novel strategy of employing uncalcined titanium silicalite-2 (TS-2-B) to immobilize Au nanoparticles as a bifunctional catalyst for the reaction. Under no promoter effects, the Au/TS-2-B catalyst compared to the referenced Au/TS-1-B catalyst delivers outstanding catalytic performance, that is, exceptionally high stability over 100 hr, propylene oxide (PO) formation rate of 118 g_PO·hr⁻¹·kg_cat⁻¹, PO selectivity of 90% and hydrogen efficiency of 35%. The plausible relationship of catalyst structure and performance is established by using multiple techniques, such as UV–vis, high-angle annular dark-field scanning transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. A unique synergy of Au–Ti⁴⁺–Ti³⁺ triple sites is proposed for our developed Au/TS-2-B catalyst with the higher stable PO formation rate and hydrogen efficiency. The insights reported here could shed new light on the rational design of highly stable and efficient Au–Ti bifunctional catalysts for the reaction.     

Effect of triethylamine treatment of titanium silicalite-1 on propylene epoxidation

Titanium silicalite-1(TS-1) treated with triethylamine (TEA) solution under different conditions was characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectrum (FTIR), ultraviolet-visible diffuse reflectance spectrum (UV-Vis), nitrogen physical adsorption and desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results show that many irregular hollows are generated in the TS-1 crystals due to the random dissolution of framework silicon and the volume of the hollow cavities increase with increasing the TEA concentration, and the treatment temperature and time. The modified TS-1 samples improved in varying degrees the catalyst life for the epoxidation of propylene in a fixed-bed reactor probably due to the generation of the hollows to make it easy for the reactants and products to diffuse out of the channels.     

表面改性未焙烧TS-1固载金催化丙烯氢氧环氧化反应性能研究

采用四丙基氢氧化铵（TPAOH）溶液对未焙烧钛硅分子筛TS-1（TS-1-B）进行二次晶化改性,以尿素为沉淀剂通过沉积-沉淀法制备改性和非改性的TS-1-B固载Au纳米催化剂,对比研究这两种催化剂丙烯氢氧环氧化反应性能的差异,阐明二次晶化改性对TS-1-B表面结构及催化行为的影响。结果表明：二次晶化改性提高了TS-1-B结晶度,降低了缺陷位硅羟基数量;改性的TS-1-B表面疏水性的提高有助于抑制产物环氧丙烷（PO）在羟基位点上吸附,其固载的金催化剂表现出显著提高的稳定性和活性。此外,对该催化剂的动力学行为也进行了研究,并计算了主/副产物生成活化能。     

Bi2SiO5/SiO2的合成及催化丙烯气相环氧化反应

水热法合成了具有介孔特征的系列Bi2SiO5/SiO2催化剂（记为SBn,n为Si与Bi物质的量比,n=0.5、5、10、20、50）,并通过X射线粉末衍射、N2物理吸附-脱附和扫描电镜等技术对SBn催化剂进行表征。结果表明,以O2为氧源,SBn催化剂在气相丙烯环氧化反应中具有良好的催化活性。在温度330 ℃,SB20催化剂上环氧丙烷选择性达50%,对应丙烯转化率为0.6%;而在温度470 ℃时,SB20催化剂上丙烯转化率接近20%,但环氧丙烷选择性降至20%。     

丙烯氢氧环氧化动力学与反应器概念设计研究进展

环氧丙烷（PO）在全球产能最高的35种化学品中,是仅次于聚丙烯的第二大丙烯衍生物,主要用于生产聚醚多元醇、聚氨酯等。相比传统的氯醇法、共氧化法和双氧水直接氧化法（HPPO）等PO生产工艺,丙烯在氢氧混合气中一步环氧化制PO（HOPO）具有工艺简单、选择性高、产物易分离、能耗低等突出优势,是生产PO的理想工艺。重点介绍了丙烯氢氧环氧化反应动力学研究进展,包括主、副反应动力学模型以及催化剂失活模型。总结了基于该过程安全操作的反应器概念设计进展。分析了丙烯氢氧环氧化反应存在的挑战,从副产物生成途径、失活动力学及颗粒催化剂上的动力学等方面展望了可能的研究方向。     

The study of the uncalcined Au catalyst and inorganic salts on direct gas-phase epoxidation of propylene

This paper presents the results of the propylene epoxidation in co-presence of hydrogen and oxygen on both dried and calcined Au catalysts, which were prepared by liquid grafting method using Me₂Au(acac) as a precursor and trimethylsilylated Ti-MCM-48 as a support. The calcined catalyst shows PO activity at temperatures much higher and wider than the dried one. Addition of inorganic salts greatly modified the catalytic behaviors. CsNO₃ could be a promising promoter whereas KBr led to the production of propionaldehyde instead of propylene oxide.     

Solvent-free gas-phase epoxidation of propylene in fluidized bed reactor

Industrial HPPO process suffers from the use of CH₃OH solvent, leading to energy-intensive and lengthy purification operations. Herein, by using a microspheric TS-1 catalyst and a fluidized bed reactor, we realized a solvent-free gas-phase epoxidation of propylene, in which, 18% C₃H₆ conversion and 97% PO selectivity have been achieved with 73% H₂O₂ utilization. Furthermore, the gas-phase epoxidation proceeds with an excellent stability, attributed to use of the fluidized bed reactor.     

丙烯氧化制环氧丙烷研究进展

环氧丙烷 (PO)是重要的有机化工原料和中间体 ,目前工业采用氯醇法和间接氧化法生产。这两种方法均存在严重缺陷 ,有待于改进。本文主要介绍丙烯直接氧化法制取PO的近期进展 ,指出了丙烯直接氧化法研究的难点和今后研究的方向。     

Explosion limits estimation and process optimization of direct propylene epoxidation with H2 and O2

Direct propylene epoxidation with H₂ and O₂, an attractive process to produce propylene oxide (PO), has a potential explosion danger due to the coexistence of flammable gases (i.e., C₃H₆ and H₂) and oxidizer (i.e., O₂). The unknown explosion limits of the multi-component feed gas mixture make it difficult to optimize the reaction process under safe operation conditions. In this work, a distribution method is proposed and verified to be effective by comparing estimated and experimental explosion limits of more than 200 kinds of flammable gas mixture. Then, it is employed to estimate the explosion limits of the feed gas mixture, some results of which are also validated by the classic Le Chatelier's Rule and flammable resistance method. Based on the estimated explosion limits, process optimization is carried out using commercially high and inherently safe reactant concentrations to enhance reaction performance. The promising results are directly obtained through the interface called gOPT in gPROMS only by using a simple, easy-constructed and mature packed-bed reactor, such as the PO yield of 13.3%, PO selectivity of 85.1% and outlet PO fraction of 1.8%. These results can be rationalized by indepth analyses and discussion about the effects of the decision variables on the operation safety and reaction performance. The insights revealed here could shed new light on the process development of the PO production based on the estimation of the explosion limits of the multi-component feed gas mixture containing flammable gases, inert gas and O₂, followed by process optimization.     

丙烯氧气氧化制环氧丙烷工艺开发进展

以分子氧为氧源的丙烯环氧化反应是近年来发展起来的一种清洁型环氧丙烷合成技术。综述了丙烯氧气氧化工艺的开发背景、开发进展及其经济性。丙烯与O₂氧化工艺以及丙烯与O₂、H₂氧化工艺因反应过程和反应机理不同而采用相异的催化剂和工艺条件,虽然丙烯氧气氧化工艺存在产率低、生产成本高的缺点,但作为具有最佳原子经济性和较低投资费用的新工艺路线,具有工业化应用前景。     

乙烯环氧化制环氧乙烷银催化剂研究进展

主要从载体、制备方法和助催化剂的改进等几个方面入手，对乙烯环氧化制环氧乙烷的银催化剂的进展情况进行了综述，并简述了我国环氧乙烷生产发展概况。     

载体孔结构对银基催化剂性能影响

乙烯氧化制环氧乙烷银催化剂所用载体为大孔惰性α-Al2 O3.载体孔道结构对金属银的分布有调控作用,通过选择适宜的孔道结构,采用银胺溶液浸渍,热分解可以获得特定尺寸分布的负载银催化剂.以不同粒度和晶相的氧化铝复配,添加不同的扩孔剂,制备了孔结构不同的三种载体负载银制得银催化剂.对银催化剂进行TGA和SEM分析,并考察其...