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。     

Liquid-phase epoxidation of propylene with molecular oxygen by chloride manganese meso-tetraphenylporphyrins

Propylene molecule owns two active sites, the direct epoxidation of propylene by dioxygen is still a challenge due to the limitation of selectivity. In this work, the direct liquid-phase propylene aerobic epoxidation protocol by chloride manganese meso-tetraphenylporphyrin (MnTPPCl) was developed. The conversion of propylene was 12.7%, and the selectivity towards PO (propylene oxide) reached up to 80.5%. The formation of PO was attributed to the mechanism via high-valent Mn species, which was confirmed by means of in situ UV–vis spectrum.     

TS-1催化丙烯环氧化反应及动力学研究

研究了丙烯环氧化反应条件,系统考察了反应压力、溶剂中水质量分数、TS-1质量分数以及反应温度对过氧化氢转化率以及环氧丙烷选择性的影响,采用非机理速率方程确定了主反应动力学参数。并采用该反应动力学模型对TS-1质量分数、溶剂中水质量分数对在不同温度下的双氧水转化速率常数进行了关联。为今后建立复杂动力学模型以及该工艺的工业化打下了良好的基础。     

Vanadium, niobium and tantalum modified mesoporous molecular sieves as catalysts for propene epoxidation

SBA-3 mesoporous molecular sieves doped with transition metal ions (Fe, V, Nb and Ta) have been applied for selective oxidation of propene towards propylene oxide in the presence of N₂O as an oxidant. The kind and amount of applied modifiers significantly affected the catalytic activity. V/SBA-3 was found to be the most active among the catalyst under study. In spite of relatively high selectivity towards propylene oxide (reaching up to 23%), the main oxidation product was still propionaldehyde. Surprisingly, CO_x was not formed over V, Nb and Ta modified SBA-3 catalysts. Additional modification of V containing samples (V/SBA-3) with iron complexes resulted in the further increase in the catalysts activity for epoxidation reaction. A PO selectivity of about 20% could be achieved at a propylene conversion of 17% over mixed Fe/V/SBA-3 catalytic system.     

两种体系合成的TS-1分子筛表征及其丙烯直接环氧化反应性能比较

采用SEM、XRD、微结构分析、IR等对以络合剂提高钛源稳定性体系和以传统体系合成的两种TS-1分子筛样品进行对比测试,并在高的双氧水浓度下考察了丙烯直接环氧化反应效果。结果表明,两种体系合成的TS-1分子筛样品的骨架结构、晶形、比表面积、孔径分布等基本一致,对丙烯直接环氧化的催化性能基本相当,但传统法合成的晶粒大小不一,而以络合剂提高钛源稳定性体系合成的晶粒为均一的均匀薄片状结构。这为较价廉体系合成TS-1分子筛的进一步研究、放大与工业应用提供了可能。     

Selective propylene epoxidation in liquid phase using highly dispersed Nb catalysts incorporated in mesoporous silicates

Selective propylene epoxidation to propylene oxide(PO) with hydrogen peroxide(H_2O_2) was carried out in a catalytic semi-batch reactor.High propylene epoxidation activity(44 h~(-1)) was observed over Nb based mesoporous silicate materials Nb-TUD-1 under mild operating conditions.The physical and chemical properties of the Nb based silicates characterized using BET,FTIR,TPD,TEM and UV–Vis revealed that the site isolation and surface acidity are crucial for PO production.Catalyst synthesis methods were investigated for their effects on PO productivity,PO selectivity and H_2O_2 utilization efficiency.It is found that Nb-TUD-1 material synthesized by the sol–gel method is more active and selective than impregnated materials for liquid phase propylene epoxidation.Surface characterization confirms that thus synthesized Nb-TUD-1 catalysts have more Lewis acidity and less Bronsted acidity compared to the catalysts by impregnation.     

苯乙烯分子氧环氧化多相催化剂研究进展

针对近年来国内外苯乙烯分子氧环氧化多相催化剂的研究进展进行了综述,主要介绍了钴系、金系、铁系及其他催化体系等催化剂。其中,钴系催化剂活性高,工艺条件温和,绿色环保,但价格昂贵;金系催化剂在低温条件下对苯乙烯分子氧环氧化表现出良好的活性;铁系催化剂活性低,但经济性好。指出负载型钴系、金系催化剂在苯乙烯分子氧环氧化研究中有潜在的应用前景。     

Gold nanoparticles stabilized in a novel periodic mesoporous organosilica of SBA-15 for styrene epoxidation

The stabilization of gold nanoparticles (GNPs) by disulfide groups linked to imidazolium chloride units in a periodic mesoporous organosilica of SBA-15 and their catalytic performances in the epoxidation of styrene were investigated. The mesoporous organosilica (PMO-SBA-15) was synthesized via a one-pot condensation process involving the assembly of ionic liquid silsesquioxane organic precursor containing disulfide group and tetraethoxysilane (TEOS) in the presence of P123 (EO₂₀PO₇₀EO₂₀). Aqueous chloroaurate ions were in situ reduced by the silanol groups presented on the channel surface of the mesoporous organosilica to form GNPs that were subsequently captured by disulfide group to obtain Au-containing mesoporous organosilica (Au-PMO-SBA-15). The PMO-SBA-15 and Au-PMO-SBA-15 were characterized by XRD, ²⁹Si MAS-NMR, FT-IR, UV–vis, TEM and N₂ adsorption–desorption measurements. It was found that both PMO-SBA-15 and Au-PMO-SBA-15 had the typical characteristics of mesoporous SBA-15, and that the GNPs entrapped into the channels of Au-PMO-SBA-15 possessed mean size of ca. 1.8 nm. The Au-PMO-SBA-15 was used as a catalyst in the epoxidation of styrene. 95% of styrene conversion and 75% of selectivity to styrene epoxide were obtained over the novel Au-PMO-SBA-15 catalyst, which were higher than that over the reported nano-Au catalysts. Furthermore, the Au-PMO-SBA-15 could be conveniently recovered for recycled use without significant loss of catalytic activity and selectivity.     

Fluid phase equilibria during propylene carbonate synthesis from propylene oxide in carbon dioxide medium

In the present study the influence of the amount of carbon dioxide on the catalytic performance during the propylene carbonate synthesis from propylene oxide and CO₂ was investigated. The reaction was performed in high-pressure batch autoclaves using immobilized 1-hydroxyethyl-9-propyl-cyclic guanidinium bromide on SBA-15 (HEPCGBr/SBA-15) as catalyst in the absence of any co-catalyst. It was found that the yield was strongly dependent on the amount of CO₂ added to the system and that the phase behavior strongly changes along the reaction pathway. The Cubic-Plus-Association (CPA) equation of state was used to predict the phase behavior during the reaction and the number and composition of coexisting phases in the multicomponent reaction system were determined. In accordance with the experimental data, the maximum conversion was achieved in the transition region between the two- and the one-phase region where a CO₂-expanded reactant/product phase (larger volume due to the dissolution of carbon dioxide in the liquid phase) is present. Optimal conditions for performing the reaction have been derived which requires consideration not only of the phase behavior of the starting phase but also of the mixture during reaction.     

Effect of composition and promoters in Au/TS-1 catalysts for direct propylene epoxidation using H2 and O2

A series of Au/titanium silicalite-1 (TS-1) catalysts with different Si/Ti ratios and promoted with alkali and alkaline earth cations were prepared by deposition–precipitation (DP) and tested for direct propylene epoxidation. It was found that the gold loading and catalytic activity was highly dependent on the pH of the DP synthesis solution and the final composition of the catalyst. Addition of Group 1 metals such as K or Cs had little effect on the gold content, but increased activity, while Group 2 metals such as Mg, Ca, Sr, and Ba increased both the gold content and the catalytic activity. The highest improvement was provided by a Mg promoted catalyst, which at 443 K and 0.1 MPa with a H₂/O₂/C₃H₆/Ar = 1/1/1/7 feed mixture gave a propylene oxide (PO) formation rate of 88 gPO h⁻¹ kg_cat⁻¹, compared to 57 gPO h⁻¹ kg_cat⁻¹ for an unpromoted catalyst, corresponding to a 50% enhancement of activity. Ammonia temperature-programmed desorption (NH₃-TPD) measurements indicated little change in adsorption amount with promotion indicating that the yield increase was not due to the elimination of acidic sites on the catalyst. Instead, the improved catalytic performance was ascribed to increased Au capture efficiency and dispersion by the catalyst. The effect of Si/Ti ratio, pH of synthesis, and the promoter ions on the gold content could be understood from their effect on the surface charge of the support.     

杂多酸催化油酸甲酯环氧化的研究

研究了以磷钨酸-D1821(磷钨酸双十八烷基季铵盐)作催化剂,二氯甲烷作溶剂,30%过氧化氢存在下油酸甲酯的环氧化反应,考察了反应条件对油酸甲酯环氧反应的影响,得到的优化反应条件为:m(30%过氧化氢)∶m(油酸甲酯)=1∶1,m(二氯甲烷)∶m(油酸甲酯)=1.5∶1,m(催化剂)∶m(油酸甲酯)=25‰。在最优条件下得到的环氧油酸甲酯的碘值在4.3 g I2/100 g左右,环氧值在3.95 g/100 g左右,酸值在0.2 mg KOH/g左右,均达到了一等品的要求。     

低成本TS-1的制备及其在丙烯环氧化中的应用

综述了低成本钛硅分子筛TS-1的制备及其在丙烯环氧化反应中的应用研究进展。低成本TS-1制备过程实现工业化主要存在粉末状TS-1的回收和过氧化氢的生产、储存等问题。提高活性及进一步降低成本是研究的重点。过氧化氢的生产与丙烯环氧化过程的集成是未来的发展方向。     

修饰剂对磷霉素环氧化催化剂的影响

采用原位法制备活性炭负载磷钨酸催化剂,制备过程中加入环氧丙基磷酸盐（顺丙烯磷酸盐的环氧化产物）作为修饰剂,获得活性炭负载修饰型PW/C催化剂,并用于顺丙烯磷酸的环氧化反应。结果表明,加入5%的修饰剂可以使该催化剂环氧化收率提高58.4%,重复使用稳定性也明显改善。采用BET、IR和XRD方法表征证明,在活性炭负载催化剂上主要催化活性成分为H₃PW₁₂O₄₀磷钨杂多酸。     

Physico-chemical characterization and catalysis on SBA-15 supported molybdenum hydrotreating catalysts

SBA-15 supported Mo, CoMo, NiMo catalysts were prepared. The supports were characterized by surface area, pore size distribution, and X-ray diffraction. The finished catalysts in oxide state were characterized by surface area analysis and X-ray diffraction in the region where the molybdenum oxide lines are seen. The sulfided catalysts were examined by oxygen chemisorption at low temperatures. The catalytic functionalities of these catalysts viz hydrodesulfurization (HDS) and hydrogenation were evaluated on sulfided catalysts. The catalytic activities of these catalysts are compared with γ-Al₂O₃- and SiO₂-supported catalysts. An attempt is made to understand the relationship between oxygen chemisorption and catalytic activities with the help of other characterization results.     

环己烯液相环氧化催化剂的研究进展

烯烃环氧化是一类重要的有机合成反应 ,其中环己烯经催化环氧化制得的环氧环己烷可广泛用作合成精细化学品的原料。阐述了Mo(Ⅵ )、V(Ⅴ )、Ti(Ⅳ )络合物、过渡金属卟啉络合物等环氧化用催化剂以及无机过氧酸盐、过氧化氢、分子氧、有机过氧酸及烷基过氧化氢等常用氧化剂在环己烯液相环氧化中的应用研究进展。还介绍了无机固体负载催化剂和高分子负载催化剂的负载化方法。最后展望了烯烃环氧化的研究开发趋势。     

Highly selective propene epoxidation with hydrogen/oxygen mixtures over titania-supported silver catalysts

Silver supported on titania was found to be active for propene epoxidation using hydrogen/oxygen mixtures at 50°C. The dependence of the activity on the preparative method is pronounced, i.e., only catalysts prepared by using deposition–precipitation exhibit activity. Optimum performance was found for 2 wt% Ag/TiO₂ calcined at 400°C. The propene epoxidation activity, the activity in the low-temperature CO oxidation, in propane oxidation and deactivation behavior of these silver catalysts strongly resemble the results obtained for the Au/TiO₂ catalysts developed by Haruta.     

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.     

钼基催化剂在烯烃液相环氧化反应中的应用研究进展

介绍了钼络合物催化剂、固载化的钼络合物催化剂及MoO₃基的固体钼催化剂在烯烃液相环氧化反应中的应用。以有机过氧化物为氧化剂时,不同的钼基催化剂均表现出很好的催化性能,其中络合物中的配体对其催化性能有很大影响,并且可以通过引入手性配体实现对烯烃的不对称环氧化,而固体钼催化剂的性能则与载体上钼物种的种类密切相关。但绝大多数钼催化剂对H₂O₂参与的环氧化反应没有活性,开发对H₂O₂有催化活性的钼基催化剂是一个重要的研究方向。     

Reactivity of electrophilic oxygen species generated over mesoporous iron-containing catalysts

The vapour phase hydroxylation of toluene and epoxidation of propene and 1-butene with nitrous oxide over Fe/SBA-15 catalysts was experimentally investigated. Modification of these mesoporous catalysts by the addition of KCl resulted in a significant transfer from benzylic/allylic oxidation towards aromatic/vinylic oxidation by suppressing the reactivity of nucleophilic oxygen species. Analogous to the Fe/ZSM-5 system, highly dispersed iron species residing within the pore structure are responsible for generating the electrophilic oxygen species upon nitrous oxide decomposition. While substrate conversions are generally low (<4%), the catalysts offer phenolic/epoxide selectivities of 70% in an environmentally benign one-step reaction.     

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.