Direct epoxidation of propylene to propylene oxide on various catalytic systems: A combinatorial micro-reactor study

A combinatorial approach is used to investigate several bimetallic catalytic systems and the promoter effect on these catalysts to develop highly active and selective catalysts for direct epoxidation of propylene to propylene oxide (PO) using molecular oxygen. 2%Cu/5%Ru/c-SiO₂ catalyst yielded the highest performance with high propylene conversion and PO selectivity among the bimetallic catalytic systems including silver, ruthenium, manganese and copper metals. On the other hand, the most effective catalyst and promoter in the epoxidation reaction was determined to be sodium chloride promoted Cu–Ru catalyst supported over SiO₂ with 36% selectivity & 9.6% conversion (3.46% yield) at 300 °C and 0.5 feed gas ratio (propylene/oxygen).     

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。     

小型热虹吸环流反应器中丙烯环氧化工艺条件

引　言钛硅催化剂 (ＴＳ - 1)上的丙烯与Ｈ2 Ｏ2 环氧化过程是环氧丙烷 (ＰＯ)洁净生产的发展方向[1,2 ] ,但对于环氧化反应器的研究尚很不完备 .该反应是一个强放热的气液固三相反应 ,要实现该反应过程的连续化 ,可以采用搅拌釜式反应器或固定床反应器(滴流床反应器 ) .搅拌釜式反应器主要用于催化剂性能评价 ,由于搅拌釜内物料返混严重 ,反应器体积效率较低 ;固定床反应器是由美国ＡＲＣＯ公司的Ｊｕｂｉｎ[3] 等发明的 ,实际上为多段气液呈并流向下的滴流床反应器 ,该反应器结构复杂 ,操作压力较大 (在 1.2 5ＭＰａ以上 ) ,且为了便于控…     

Propylene Epoxidation Over Silver Supported on Titanium Silicalite Zeolite

Epoxidation of propylene to propylene oxide over Ag/TS-1 in the presence of oxygen and hydrogen was carried out in a fixed-bed, quartz flow reactor. The effects of Ag loading, Si/Ti ratio of TS-1 and calcination temperature and calcination method of Ag/TS-1 on the propylene epoxidation were investigated. The results show that Ag loading, the calcination temperature and calcination method of Ag/TS-1 as well as the Si/Ti ratio of TS-1 have a great effect on the catalytic properties. The optimum Ag loading, calcination temperature and calcination method of Ag/TS-1 and Si/Ti ratio of TS-1 are 2 wt%, 450 °C in air and 64 respectively. Over 2.0 wt% Ag/TS-1(n_Si/n_Ti = 64) catalyst, at a space velocity of 3000 h^-1, 0.92% propylene conversion with 91.21% selectivity to propylene oxide is obtained at 150 °C. The deactivation of Ag/TS-1 catalyst is not due to the changes of active species, but because of the coke of the catalyst, which can be easily regenerated by calcination at 450 °C in air.     

Surface-Initiated Gas-Phase Epoxidation of Propylene with Molecular Oxygen by Silica-Supported Molybdenum Oxide: Effects of Addition of C3H8 or NO and Reactor Design

The gas-phase epoxidation of propylene was studied over MoO _x /SiO₂ catalysts in a reaction system with a post-catalytic bed volume. In the reaction of a mixture of propylene and propane with oxygen below 578 K, propylene oxide (PO) was mainly formed from the oxidation of propylene. It was found that the oxidation reaction was very sensitive to the temperature of the post-catalytic space more than the temperature of the catalyst bed, strongly indicating that radical reactions occurring in the post-catalytic bed free space were responsible for the PO formation. The addition of NO increased propylene conversions and PO selectivity at low conversions, confirming that radical reactions were involved in the propylene reactions.     

Kinetics of Selective Oxidation of Dimethyl Ether to Formaldehyde Over Al2O3-Supported VO x and MoO x Catalysts

The object of this work is to study the effect of hydrothermal treatment on the TS-1/SiO₂ catalyst in propylene epoxidation in fixed bed. The TS-1/SiO₂ catalysts before and after hydrothermal treatment were characterized by means of XRD, XRF, BET, UV–Vis and EPR techniques. It was found by EPR characterization that two types of Ti(IV)-superoxide radicals, A (g _z = 2.0271; g _y = 2.0074; g _x = 2.0010) and B (g _z = 2.0247; g _y = 2.0074; g _x = 2.0010), were observed for the TS-1/SiO₂ catalyst. The superoxo species A was converted to B after the TS-1/SiO₂ catalyst was hydrothermally treated. The results show that hydrothermal treatment temperature and time have marked effects on the activity and the PO selectivity. The optimal hydrothermal treatment temperature and time are 170 and 4 h, respectively. In the long-term propylene epoxidation reaction, about 95% H₂O₂ conversion and above 94% PO selectivity are obtained over TS-1/SiO₂ catalyst hydrothermally treated at 170° C for 4 h.     

Reactions of Propylene Oxide on Supported Silver Catalysts: Insights into Pathways Limiting Epoxidation Selectivity

The reactions of propylene oxide (PO) on silver catalysts were studied to understand the network of parallel and sequential reactions that may limit the selectivity of propylene epoxidation by these catalysts. The products of the anaerobic reaction of PO on Ag/??-Al₂O₃ were propanal, acetone and allyl alcohol for PO conversions below 2?C3%. As the conversion of PO was increased either by increasing the temperature or the contact time, acrolein was formed at the expense of propanal, indicating that acrolein is a secondary reaction product in PO decomposition. With addition of oxygen to the feedstream the conversion of PO increased moderately. In contrast to the experiments in absence of oxygen, CO₂ was a significant product while the selectivity to propanal decreased as soon as oxygen was introduced in the system. Allyl alcohol disappeared completely from the product stream in the presence of oxygen, reacting to form acrolein and CO₂. The product distribution may be explained by a network of reactions involving two types of oxametallacycles formed by ring opening of PO: one with the oxygen bonded to C1 (OMC1, linear) and the other with oxygen bonded to C2 (OMC2, branched). OMC1 reacts to form PO, propanal, and allyl alcohol. OMC2 can give rise to acetone and PO. (DFT) calculations have verified accessibility to the two oxametallacycle structures from propylene and PO, and have provided energy barriers for each of the steps involved in PO isomerization. This work illustrates the complex manifold of sequential reactions that contribute to the difficulty of achieving high selectivity in direct propylene epoxidation with silver catalysts.     

Gas-Phase Propylene Epoxidation over Ag/TS-1 Prepared in W/O Microemulsion: Effects of the Molar Ratio of Water to Surfactant and the Reaction Temperature

Ag/TS-1 was prepared by microemulsion method in which dioctyl sulfosuccinate sodium salt (AOT) was used as the surfactant and n-heptane as the organic solvent. The synthesized Ag/TS-1 was characterized by UV–Vis and TEM and its catalytic properties in gas-phase propylene epoxidation were carried out in a fixed bed reactor. The results show that Ag is highly dispersed on TS-1 and the crystal size can be adjusted through the adjusting of the molar ratio of water to surfactant ([H₂O]/[surfactant] = R). The catalyst prepared with R = 4.74 exhibits the highest catalytic activity for propylene epoxidation in gas-phase, the optimal reaction temperature scope is between 363 and 383 K. Over the catalyst prepared with R = 4.11, propylene conversion and the selectivity to propylene oxide (PO) are 1.1% and 91.0%, respectively.     

Alkylation of benzene with propylene catalyzed by FeCl3-Chloropyridine ionic liquid

Alkylation of benzene with propylene was carried out with FeCl₃-chloro-butyl-pyridine (FeCl₃-[bpc]) ionic liquid as catalyst to obtain cumene. Significant improvements in propylene conversion and cumene selectivity under mild reaction conditions were attained by modification of the catalyst with HCl. Under 20°C, 0.1 MPa, reaction time 5 min, mole ratio of benzene to propylene 10:1 and mass ratio of FeCl₃-[bpc] to benzene 1:100, conversion of propylene can increase from 83.60% to 100.00% and selectivity of cumene can increase from 90.86% to 98.47%. If reaction is carried out in following two stages, the result will be very good. At the initial stage of the reaction, alkylation is the main reaction and a higher conversion of propylene is obtained at a lower temperature. At the later stage of the reaction, transalkylation is the main reaction and selectivity to cumene can be increased by appropriately raising the reaction temperature. Translated from Petrochemical Technology, 2006, 35(9): 819–823 [译自: 石油化工]     

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.     

固体强碱绿色催化环氧丙烷水解合成1,2-丙二醇

该文制备了不同碱强度的固体碱催化剂,并应用于环氧丙烷(PO)水解合成1,2-丙二醇的反应。结果表明:随着催化剂碱强度的增加,环氧丙烷的转化率不断升高;说明强碱催化剂有利于环氧丙烷水解反应。在此基础上,作者系统考察了催化剂用量、反应温度、原料摩尔比和反应时间对催化性能的影响。结果表明:当催化剂CaO-ZrO2质量为反应原料质量的1.0%,反应温度为120℃,反应原料配比为:n(H2O)∶n(PO)=5∶1,反应时间2h时,其催化效果较优,环氧丙烷转化率最高为92.3%,1,2-丙二醇选择性可达89.4%。     

Epoxidation of Propylene with Hydrogen Peroxide Over TS-1 Catalyst Synthesized in the Presence of Polystyrene

Titanium silicalite-1 (TS-1) catalyst was synthesized in the presence of polystyrene (PS) particles (denoted as TS-1_PS catalyst) for use in the epoxidation of propylene with hydrogen peroxide. For the purpose of comparison, TS-1 catalyst was also synthesized by a conventional method (in the absence of polystyrene particles). In the epoxidation of propylene, the TS-1_PS catalyst showed a higher conversion of hydrogen peroxide and a higher selectivity for propylene oxide (PO) than the TS-1 catalyst. Consequently, the TS-1_PS catalyst showed a higher yield for PO than the TS-1 catalyst. Characterization results showed that the high catalytic performance of TS-1_PS was attributed to the enhanced hydrophobic property of the catalyst and the suppressed formation of anatase TiO₂ in the catalyst.     

Catalytic performance of Ti-SBA-15 prepared by chemical vapor deposition for propylene epoxidation

Ti-SBA-15C catalysts were prepared by supporting Ti on SBA-15 with chemical vapor deposition (CVD) using TiCl₄ as titanium source, and were characterized by XRD, N₂ adsorption, FT-IR and ICP. The results show that SBA-15E prepared by ethanol solution extracting template has higher concentration of surface Si-OH groups than SBA-15 calcined at 550 °C, resulting in high Ti content on Ti-SBA-15EC prepared by CVD. The temperature and time of TiCl₄ deposition affect the Ti content and catalytic activity of Ti-SBA-15EC for the epoxidation of propylene with cumene hydroperoxide (CHP). Ti-SBA-15EC prepared by CVD at 700 °C for 1.5 h exhibits more excellent performance than Ti-SBA-15C, Ti-SBA-15 prepared hydrothermally and Ti/SBA-15 (impregnation method), and the 87.3% conversion of CHP and 96.4% selectivity to propylene oxide can be obtained at 80 °C for 4 h. The performance of Ti-SBA-15EC is decreased hardly for the epoxidation of propylene after used repeatedly 6 times.     

Water-tolerant graphene oxide as a high-efficiency catalyst for the synthesis of propylene carbonate from propylene oxide and carbon dioxide

Graphene oxide (GO) was found to be a metal-free, water-tolerant and high-efficiency catalyst towards the cycloaddition of carbon dioxide (CO₂) to propylene oxide (PO) for the synthesis of propylene carbonate (PC) at room temperature (RT) and atmospheric pressure without the need for a solvent. Using GO as catalyst and tetrabutylammonium bromide (Bu₄NBr) as co-catalyst, PO is rapidly converted to PC with 96% yield and 100% selectivity under relatively mild conditions (100 °C, 2.25 MPa, 1 h). The effects of catalyst amount, temperature, time and water (H₂O) addition on the reaction were investigated. It is found that the presence of a proper amount of H₂O enhances the conversion of epoxide remarkably. A comparison of the catalytic activities of a number of reduced graphene oxide (r-GO) samples under similar reaction conditions revealed that it is the hydroxyl groups (rather than the carboxyl groups) on GO that form hydrogen bonds with PO, and act synergistically with halide anions to promote the cycloaddition reaction. A possible mechanism is proposed.     

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。     

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.     

Gas-phase epoxidation of propylene through radicals generated by silica-supported molybdenum oxide

It was found that silica-supported molybdenum oxide was high effective for the epoxidation of propylene among various silica-supported metal oxides. The post-catalytic bed volume played an important role in its formation. On a MoO_x/SiO₂ with 0.255 mmol/g-SiO₂, a propylene conversion of 17.6% and a PO selectivity of 43.6% were obtained at 5 atm, 573 K and flow rates of C₃H₆/O₂/He = 10/5/10 cm³ min⁻¹. The characterization studies indicated that crystalline MoO₃ nano-particle species was more effective for propylene epoxidation to PO than molecularly dispersed Mo oxide species. The reaction mechanism of propylene epoxidation on MoO_x/SiO₂ catalysts is hypothesized to involve gas-phase radicals generated at relatively low temperature by the dispersed molybdenum oxide species. These radicals participated in homogeneous reactions with molecular oxygen to produce propylene oxide.     

Highly effective ironporphyrin-immobilized catalytic systems for the processes of hydroxylation and epoxidation of lower alkanes and alkenes

The catalytic activity of the following samples in the hydroxylation reaction were studied: PPFe 3+ OH/AlSiCr, PPFe 3+ OH/AlSiMg, PPFe 3+ OH/Al 2 O 3 , and per-FTPhPFe 3+ OH/Al 2 O 3 . PPFe 3+ OH/AlSiMg-catalyzed methane hydroxylation yielded 46.5 wt% of methanol at a 48% methane conversion, at a maximum of 180°C. Per-FTPhPFe 3+ OH/Al 2 O 3 testing in propane hydroxylation by H 2 O 2 yielded 39.3 mol% of isopropanol. Per-FTPhPFe 3+ OH/Al 2 O 3 -catalyzed propylene oxidation by H 2 O 2 yielded 30 mol% of propylene oxide. PPFe 3+ OH/Al 2 O 3 -catalyzed propylene epoxidation yielded the following: the selectivity on the monooxygenase products is about 100%, the selectivity on propylene oxide - 59.2%, propylene conversion - 93.3%. The experimental research data revealed the fact that during the reaction of epoxidation per-FTPhPFe 3+ OH/Al 2 O 3 proved to be more stable under the influence of oxidizer and temperature than PPFe 3+ OH/Al 2 O 3 .     

HIGHLY EFFECTIVE IRONPORPHYRIN-IMMOBILIZED CATALYTIC SYSTEMS FOR THE PROCESSES OF HYDROXYLATION AND EPOXIDATION OF LOWER ALKANES AND ALKENES

The catalytic activity of the following samples in the hydroxylation reaction were studied: PPFe 3+ OH/AlSiCr, PPFe 3+ OH/AlSiMg, PPFe 3+ OH/Al 2 O 3 , and per-FTPhPFe 3+ OH/Al 2 O 3 . PPFe 3+ OH/AlSiMg-catalyzed methane hydroxylation yielded 46.5 wt% of methanol at a 48% methane conversion, at a maximum of 180°C. Per-FTPhPFe 3+ OH/Al 2 O 3 testing in propane hydroxylation by H 2 O 2 yielded 39.3 mol% of isopropanol. Per-FTPhPFe 3+ OH/Al 2 O 3 -catalyzed propylene oxidation by H 2 O 2 yielded 30 mol% of propylene oxide. PPFe 3+ OH/Al 2 O 3 -catalyzed propylene epoxidation yielded the following: the selectivity on the monooxygenase products is about 100%, the selectivity on propylene oxide - 59.2%, propylene conversion - 93.3%. The experimental research data revealed the fact that during the reaction of epoxidation per-FTPhPFe 3+ OH/Al 2 O 3 proved to be more stable under the influence of oxidizer and temperature than PPFe 3+ OH/Al 2 O 3 .     

高选择性合成1-甲氧基-2-丙醇固体催化剂的筛选和催化作用

对碱土金属氧化物和两性氧化物等10种氧化物作为合成1 甲氧基 2 丙醇固体催化剂进行了催化性能筛选。发现在碱土金属氧化物MgO、CaO和BaO中,中强碱MgO具有较高的环氧丙烷(PO)转化率(71 07%)和1 甲氧基 2 丙醇(PPM)选择性(92 53%)。在两性氧化物中,ZnO具有较高的PO转化率(55 26%)和PPM选择性(92 37%)。系统考察了反应温度、催化剂用量、反应时间和原料摩尔配比对MgO、ZnO的催化作用特点的影响,发现MgO在催化性能和1 甲氧基 2 丙醇选择性方面表现出的综合性能优于其他催化剂。