Catalytic Synthesis of Methylene Diphenyl Dicarbamate in AcOH/H2O Mixed Solvent

<正>In a mixed solvent of acetic acid(AcOH)/water,methylene diphenyl dicarbamate(MDC) was synthesized by the condensation of methyl phenyl carbamate(MPC) and formaldehyde in the presence of an inorganic acid catalyst. Based on the different solubilities to MPC and MDC,the mixed solvent showed higher catalytic performance than pure water.The mixed solvent not only promoted the condensation of MPC but aslo exhibited the advantage of the product separation with the reactants.Under the optimized conditions:a H_2SO_4 mass fraction of 31%,a reaction temperature of 95℃and reaction time of 3.5 h,the yield of MDC reached 74.3%.In addition,the recycle of the solvent was also investigated.     

钛酸酯催化碳酸二甲酯与苯酚酯交换反应

The transesterification of phenol and dimethyl carbonate (DMC) to diphenyl carbonate (DPC) was studied using tetrabutyl titanate and tetraphenyl titanate as catalysts. The main product was found to be methyl phenyl carbonate (MPC) which is an intermediate of the reaction. The selectivity for DPC was improved when increasing the phenol/DMC molar ratio or prolonging the reaction time. The phenol conversion, selectivity for MPC and DPC were 47 4%, 90 9% and 9 14%, respectively, when the transesterification reaction approached equilibrium under the conditions of 175 ℃, 25 h and DMC∶phenol∶ Ti(OBu) 4 molar ratio of 1 5∶1∶0 05. The selectivity for DPC could reach 12.2% when the reaction time was 30 h. The tetrabutyl titanate catalyst showed a higher catalytic activity than tetraphenyl titanate.     

Methanol Steam Reforming Reactions on CuZn（Zr）AlO Catalyst

The catalytic performances of methanol steam reforming reactions on CuZn(Zr)AlO catalysts were studied. When the ZrO2 promoter was added to a CuZnAlO catalyst, its methanol conversion, H2 production and H2 selectivity improved greatly. By using the (?)COPZr-2 catalyst as an example, which exhibited the best catalytic performance, the optimized reaction conditions were established to be:     

Carbon dioxide conversion to valuable chemical products over composite catalytic systems

This paper reports an experimental study on catalytic conversion of carbon dioxide to methanol,ethanol and acetic acid.Catalysts having different catalytic functions were synthesized and combined in different ways to enhance the selectivity to desired products.The combined catalyst system possessed the following functions:methanol synthesis,Fischer-Tropsch synthesis,water-gas-shift and hydrogenation.Results showed that the methods of integrating these catalytic functions played an important role in achieving the desired product selectivity.We speculate that if methanol synthesis sites were located adjacent to the C-C chain growth sites,the formation rate of C₂ oxygenates would be enhanced.The advantage of using a high temperature methanol catalyst PdZnAl in the combined catalyst system was demonstrated.In the presence of PdZnAl catalyst,the combined catalyst system was stable at 380°C.It was observed that,at high temperature,kinetics favored oxygenate formation.The results implied that the process can be intensified by operating at high temperature using Pd-based methanol synthesis catalyst.Steam reforming of the byproduct organics was demonstrated as a means to provide supplemental hydrogen.Preliminary process design,simulation,and economic analysis of the proposed CO₂ conversion process were carried out.Economic analysis indicates how ethanol production cost was affected by the price of CO₂ and hydrogen.     

Hydrogenation of coumarin to octahydrocoumarin over a Ru/C catalyst

The production of octahydrocoumarin, which can serve as a replacement for toxic coumarin, was investigated using 5% Ru on active carbon (Ru/C) as the catalyst for the hydrogenation of couma-rin. The hydrogenation was studied by optimizing the reaction conditions (pressure, solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for dif-ferent solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 °C, 10 MPa, 60 wt% coumarin in methanol, and 0.5 wt% (based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin, the selectivity to the desired product was 90%.     

Ru/C催化剂上香豆素加氢制八氢香豆素（英文）

The production of octahydrocoumarin,which can serve as a replacement for toxic coumarin,was investigated using 5% Ru on active carbon(Ru/C) as the catalyst for the hydrogenation of coumarin. The hydrogenation was studied by optimizing the reaction conditions(pressure,solvent and coumarin concentration). The activity and selectivity of the Ru/C catalyst were compared for different solvents. The mechanism of coumarin hydrogenation was deduced. The formation of side products was explained. The optimal hydrogenation reaction conditions were: 130 °C,10 MPa,60 wt% coumarin in methanol,and 0.5 wt%(based on coumarin) of Ru/C catalyst. At the complete conversion of coumarin,the selectivity to the desired product was 90%.     

钨酸钠催化芳香腈高选择性氧化制备芳香酰胺

 The preparation of aryl amides by selective oxidation of aryl nitriles using sodium tungstate as catalyst and sodium percarbonate or sodium carbonate-hydrogen peroxide as the oxidant in a methanol and water solution was studied. Aryl nitriles were converted to aryl amides with very high selectivity of 95%～100% at room temperature. The reactivity of aryl nitriles decreased with increasing their branched chain length. In the oxidation of tolunitriles, the oxidation rate of p-tolunitrile and m-tolunitrile was very fast, but the oxidation rate of o-tolunitrile was very slow. The oxidation rate of p-haloid aryl nitriles and p-nitro aryl nitrile decreased in the order p-nitrobenzonitrile＞p-chlorobenzonitrile＞p-bromobenzonitrile, while the selectivity for aryl amides was maintained at a high level of 98%～100%. The comparison of the two oxidants showed that when sodium carbonate-hydrogen peroxide was used as oxidant, the oxidation rate and selectivity were better than that when percarbonate was used. The sodium tungstate catalyst and carbonate can be reused and the catalytic activity and selectivity did not change if a suitable amount of hydrogen peroxide was supplied. This work provides a convenient method for the preparation of aryl amides from aryl nitriles under very mild reaction conditions.     

Study on the alkylation reaction of guanine and N-acetylguanine and the synthesis of 1''''-C alkylated carba-DHPG analogues

The alkylation reaction of guanine and N-acetylguanine with model compounds such as isopropyl bromide or 4-heptyl tosylate were studied. The reaction conditions such as temperature, solvent, base, and catalyst were examined for their effects on the reaction rate, and the yield and regioselectivity of the coupling reaction. The highest yield was obtained by using DMSO as the solvent. The reaction proceeded in a homogenous manner to give higher yield of 9-N and 7-N substituted product in a mole ratio of 1:1. The ratio could be raised to 2:1 if dibenzo-18-crown-6 was used as a catalyst. Using the above procedure, three carba-DHPG analogues bearing different 1'-C alkyl side chains were synthesized.     

Kinetics of Methanol Carbonylation to Methyl Formate Catalyzed by Sodium Methoxide

Kinetics of synthesis of methyl formate from carbon monoxide and methanol, using sodium methoxide as the catalyst and pyridine as the promoter in a batch reactor, was studied. Kinetic parameters such as the apparent reaction orders, the rate constant and the apparent activation energies were obtained. The experimental results showed that both the reaction orders with respect to CO and methanol equal to 1, the general reaction kinetic equation is (-r)=-dp(CO)/dt=k, p(CO).[MeOH], and the rate constant is k=8.82×10~6exp [-61.19×10~3/(R·T)] in the presence of pyridine. The apparent activation energies had decreased 6.44 kJ/mol and the rate constant had increased more than 1.5 times when pyridine was used as the promoter in the catalyst system.     

New process of low-temperature methanol synthesis from CO/CO_2/H_2 based on dual-catalysis

A new process of low-temperature methanol synthesis from CO/CO2/H2 based on dual-catalysis has been developed. Some alcohols, especially 2-alcohol, were found to have high catalytic promoting effect on the synthesis of methanol from CO hydrogenation. At 443 K and 5 MPa, the synthesis of methanol could process high effectively, resulting from the synergic catalysis of Cu/ZnO solid catalyst and 2-alcohol solvent catalyst. The primary results showed that when 2-butanol was used as reaction solvent, the one-pass average yield and the selectivity of methanol, in 40 h continuous reaction at temperature as low as 443 K and 5 MPa, were high up to 46.51% and 98.94% respectively. The catalytic activity was stable and the reaction temperature was 80 K or so lower than that in current industry synthesis process. This new process hopefully will become a practical method for methanol synthesis at low temperature.     

苯基脲与甲醇合成苯氨基甲酸甲酯的研究

采用苯基脲与甲醇反应合成了苯氨基甲酸甲酯,考察了不同催化剂、原料配比及反应工艺条件的影响,确定了适宜的合成条件,并根据产物分布对催化反应机理进行了初步探讨.结果表明,以PbO为催化剂,于140℃反应4h后,苯基脲转化率为95.2%,苯氨基甲酸甲酯收率为80.6%.     

苯胺与氨基甲酸甲酯合成苯氨基甲酸甲酯反应研究

以无水氯化锌为催化剂,考察了温度、时间、催化剂含量及原料配比等条件对合成反应的影响,确定了最优化反应条件,并初步探讨了反应机理.最佳反应条件下MPC收率可达89.90%,选择性为99.76%.     

Catalytic synthesis of methylene diphenyl dicarbamate from methyl phenyl carbamate and trioxane over sulfuric acid catalyst

Methylene diphenyl dicarbamate (MDC) was synthesized from methyl phenyl carbamate (MPC) and trioxane using sulfuric acid (H₂SO₄) as catalyst. The effects of reaction temperature, reaction time, molar ratio of reactants and the content of catalyst have been studied in details. The results showed that H₂SO₄ exhibited high catalytic activity with the merits of moderate reaction velocity. Under the conditions of n(MPC)/n(trioxane) = 3:1, reaction temperature of 95°C, reaction time of 3.5 h and 30% H₂SO₄, the conversion of MPC reached 99.0% with the selectivity of MDC 81.6%. Moreover, the H₂SO₄ catalyst was reused five times without obviously activity decrease. Based on the identification of byproducts, a possible reaction mechanism was proposed.     

用于甲醇直接气相氧化羰基化的负载铜催化剂

 采用浸渍法制备了负载型铜基催化剂,并用其催化甲醇直接气相氧化羰基化合成碳酸二甲酯(DMC), 考察了浸渍溶剂、载体、助催化剂和铜含量的影响. 结果表明,以CuCl为活性组分原料、浓氨水为浸渍溶剂和活性炭为载体制得的负载铜催化剂显示出很高的催化活性,在特定的反应条件下,该催化剂上甲醇的转化率可达27.7%, DMC选择性可达95%. 分子筛负载的铜催化剂上甲醇的转化率低于1%, 但是生成DMC的选择性高达100%. 催化剂活性随着Cu负载量的增加而增大,但负载量过高可引起甲醇的过度氧化反应,导致DMC选择性下降. 催化剂中添加KOH或钯化合物,有利于提高以CuCl2为活性组分原料制得的铜催化剂的活性,但同时也促进了副反应的发生. 随着反应时间的延长,催化剂的活性组分流失,活性下降,但是生成DMC的选择性维持在95%左右.     

KF/Al2O3催化剂上苯脲醇解合成苯氨基甲酸甲酯的研究

采用浸渍法制备负载KF固体碱催化剂,应用于苯脲和甲醇制备苯氨基甲酸甲酯的反应,考察了氧化物载体、卤化钾种类对催化剂性能的影响,KF/Al₂O₃催化剂显示出良好的催化活性和苯氨基甲酸甲酯的选择性。通过对KF/Al₂O₃催化剂中KF的负载量和催化剂焙烧温度的研究发现,在500 ℃焙烧4 h、负载质量分数50%KF的催化剂能够更好地促进MPC生成,苯脲转化率和苯氨基甲酸甲酯选择性分别达到96.5%和86.3%。XRD分析表明,KF与Al₂O₃之间存在较强的相互作用,部分转化为K₃AlF₆。KF与K₃AlF₆分别对甲醇的活化和苯脲的选择性起促进作用,两者的协同效应共同促进了目标产物苯氨基甲酸甲酯的生成。     

Solvent Effect and Reactivity Trend in the Aerobic Oxidation of 1,3‐Propanediols over Gold Supported on Titania: NMR Diffusion and Relaxation Studies

In recent work, it was reported that changes in solvent composition, precisely the addition of water, significantly inhibits the catalytic activity of Au/TiO₂ catalyst in the aerobic oxidation of 1,4‐butanediol in methanol due to changes in diffusion and adsorption properties of the reactant. In order to understand whether the inhibition mechanism of water on diol oxidation in methanol is generally valid, the solvent effect on the aerobic catalytic oxidation of 1,3‐propanediol and its two methyl‐substituted homologues, 2‐methyl‐1,3‐propanediol and 2,2‐dimethyl‐1,3‐propanediol, over a Au/TiO₂ catalyst has been studied here using conventional catalytic reaction monitoring in combination with pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) diffusion and NMR relaxation time measurements. Diol conversion is significantly lower when water is present in the initial diol/methanol mixture. A reactivity trend within the group of diols was also observed. Combined NMR diffusion and relaxation time measurements suggest that molecular diffusion and, in particular, the relative strength of diol adsorption, are important factors in determining the conversion. These results highlight NMR diffusion and relaxation techniques as novel, non‐invasive characterisation tools for catalytic materials, which complement conventional reaction data.     

有机锡催化苯氨基甲酸甲酯分解的研究

对几种锡化合物催化苯氨基甲酸甲酯(MPC)热分解制苯基异氰酸酯(PI)反应进行了研究, 发现二丁基氧化锡具有较高的催化活性. 用HPLC-MS确定了分解的未知副产物为二苯基碳化二亚胺(DPCD). 分析认为生成N,N'-二苯基脲(DPU)和DPCD的反应为合成PI的主要竞争反应. 常压下以Bu₂SnO为催化剂时的适宜反应条件为以邻二氯苯(ODCB)为溶剂, 溶剂用量为MPC用量的15倍(质量比), Bu₂SnO用量为MPC用量的0.075 (摩尔比), 反应时间1 h. 此条件下MPC转化率为85.17%, PI收率为67.65%.     

苯氨基甲酸甲酯分解催化剂Bi-Zn复合氧化物的制备及其催化性能

采用共沉淀法制备了一系列Bi-Zn复合氧化物催化剂并将其用于催化苯氨基甲酸甲酯(MPC)分解制备苯基异氰酸酯(PI).用热重、X射线衍射和傅里叶变换红外光谱考察了Bi/Zn摩尔比和焙烧温度对催化剂物相结构和表面性质的影响.结果表明,Zn的加入使Bi_2O_3由α晶相转变为活性更高的β晶相,500℃焙烧时Bi-Zn前驱体分解较为完全,析出Bi_2O_3粒子的同时伴生较多Bi_(7.65)Zn_(0.35)O_(11.83)晶相.在Bi/Zn摩尔比为2/1,焙烧温度为500℃条件下制得的催化剂活性最高,此时MPC转化率为86.O%,PI选择性为91.7%,优于单独使用Bi_2O_3时的催化性能.     

离子液体体系中1－丁烯二聚反应的研究

 研究了在强酸性AlCl3／Et2AlCl／［BMIM］Cl型离子液体体系中过渡金属化合物对1－丁烯二聚反应的催化作用．结果表明，［BMIM］Cl对强酸性AlCl3／Et2AlCl催化剂催化1－丁烯高聚反应有明显的阻聚作用，并显著提高了1－丁烯二聚的选择性．在过渡金属化合物中，含镍化合物对1－丁烯二聚反应有最好的催化效果．在最佳反应条件下，1－丁烯的转化率可达95．1％，二聚产物C8烯的选择性为85．8％．同时，对1－丁烯二聚反应的机理进行了初步探讨．