Lewis酸催化合成草酸二苯酯反应研究

研究了Lewis酸催化剂催化苯酚和草酸二甲酯酯交换合成草酸二苯酯(DPO)反应。考察了不同Lewis酸催化剂对DPO合成反应的催化活性和Lewis酸催化剂的酸性对催化性能的影响,确定了弱酸中心促进主产物甲基苯基草酸酯(MPO)和DPO的生成,而强酸中心有利于副产物苯甲醚的生成。以弱酸TS-1分子筛为催化剂,MPO和DPO总选择性为99.2%。以强酸AlCl3为催化剂,苯甲醚选择性达到60.4%。探讨了Lewis酸催化剂催化苯酚和草酸二甲酯酯交换合成草酸二苯酯反应机理。Lewis酸催化苯酚和DMO酯交换合成MPO反应是按酰氧键断裂的反应历程进行的,DMO中和羰基相连的给电子基的-COO-基团及较大的基团体积降低了苯酚和DMO酯交换合成MPO反应的反应活性。而苯酚和DMO甲基化反应生成苯甲醚是按烃氧键断裂的反应历程进行的。     

酯交换法制备草酸二苯酯催化剂研究进展

草酸二烷基酯与苯酚酯交换合成草酸二苯酯,然后草酸二苯酯脱羰制备碳酸二苯酯是近年来颇受关注的绿色工艺路线,其研究重点为催化剂。对近年来草酸二烷基酯与苯酚酯交换合成草酸二苯酯催化剂研究进展进行综述,认为研发高稳定性的改性分子筛催化剂和负载型MoO₃/SiO₂催化剂是未来主要发展方向。     

碳酸二苯酯的合成工艺新进展

评述了4种非光气法合成碳酸二苯酯的新工艺,包括草酸二甲酯与苯酚酯交换法、碳酸二甲酯与乙酸苯醑酯交换法、尿素酯化法以及二硫化碳合成法.重点讨论了催化剂和工艺条件对合成碳酸二苯酯的影响.同时还介绍了3种偶联新工艺,即氧化羰化合成草酸二甲酯和草酸二甲酯与苯酚酯交换相结合的偶联新工艺、尿素醇解与碳酸二烷基酯与苯酚酯交换偶联的新工艺、乙酸甲酯高温裂解与碳酸二甲酯与乙酸苯酯酯交换相结合的新工艺.这些偶联工艺均考虑了各种副产物的循环使用,原料的利用率高、操作费用较低、有较强的竞争力.     

草酸二异辛酯合成新工艺的研究

选用催化活性高、选择性好、后处理简单的有机锡作催化剂，以草酸二甲酯和异辛醇为原料合成草酸二异辛酯。考察了反应温度、原料摩尔比、催化剂质量分数和反应时间等因素对酯交换反应的影响。结果表明，最佳酯化反应工艺条件为：n(异辛醇)∶n(草酸二甲酯)=3.8∶1、w(催化剂)为2.0%、反应时间为6.5 h,在该反应条件下草酸二甲酯的转化率达到93.08%,收率为86.79%。催化剂重复使用5次后，草酸二甲酯的转化率仍可达到92.02%,收率为81.84%。     

醋酐与苯酚酯化合成醋酸苯酯的研究

采用醋酐、苯酚为原料酯化合成醋酸苯酯。无催化剂情况下,考察了原料摩尔比、反应温度对醋酸苯酯收率的影响。发现适当提高反应温度可以增加醋酸苯酯收率,反应温度在130℃,醋酐与苯酚摩尔比值为1.2条件下,醋酸苯酯收率达到99%(以苯酚计)以上。同时,还研究了自制固体酸催化剂在该反应中的催化性能。结果表明,该催化剂具有良好的催化性能,110℃下,醋酸苯酯收率达到99.3%。     

稀土固体超强酸催化合成草酸二丁酯

以稀土固体超强酸La^3 ／TiO2／SO4^2-为催化剂,催化酯化合成草酸二丁酯。考察了酯化温度、正丁醇与草酸物质的量比、带水剂苯用量、反应时间、催化剂用量等因素对反应的影响。结果表明：在120℃,正丁醇与草酸物质的量比为4,带水剂苯用量为15mL／0．1mol草酸,反应时间为2．5～3h,催化剂用量为0．8g／0．1mol草酸的条件下,草酸二丁酯收率大于93．7％。     

碳酸乙烯酯酯交换合成碳酸二苯酯

为利用碳酸乙烯酯固定的CO2,拓展碳酸二苯酯的合成方法,对碳酸乙烯酯酯交换合成碳酸二苯酯的反应进行了热力学分析,并考察了催化剂、反应温度、催化剂质量分数和反应时间对合成碳酸二苯酯的影响。结果表明:碳酸乙烯酯与苯酚的酯交换反应在热力学上是不可行的,而将苯酚乙酰化后可以实现由碳酸乙烯酯经酯交换合成碳酸二苯酯;不同催化剂催化酯交换反应时,n-Bu2SnO显示了最高的酯交换选择性。当反应温度为190℃,碳酸乙烯酯与乙酸苯酯的摩尔比为1∶2,n-Bu2SnO质量分数8%,反应时间10 h时,碳酸乙烯酯的转化率为15.1%,酯交换选择性64.2%,碳酸二苯酯的收率7.5%。     

酸化膨润土催化合成草酸二丁酯

以酸化膨润土(SO₄^2-/Bentonite)固体酸为催化剂,草酸和正丁醇为原料,合成草酸二丁酯。考察焙烧温度对催化剂活性的影响。结果表明,焙烧温度500 ℃时催化剂活性较好。考察反应温度、原料配比、催化剂用量和反应时间等因素对酯化反应的影响,通过正交实验得到最佳酯化反应工艺条件：n(正丁醇)∶n(草酸)=3.5∶1,w(SO₄^2-/Bentonite)＝1.5%,反应温度130 ℃,反应时间3 h。最佳酯化反应条件下,草酸的转化率达到95.8%。催化剂重复使用6次后,草酸转化率达到93.6%。     

利用纳米SO42-/SnO2催化合成草酸二异戊酯

采用沉淀-浸渍法合成了新型催化材料纳米SO42-/SnO2,并利用SO42-/SnO2为催化剂,催化合成草酸二异戊酯,考察了催化剂焙烧温度、反应物配比、反应时间、催化剂质量、带水剂用量对草酸二异戊酯收率的影响,同时也考察了催化剂的重复使用性能。实验结果表明:SO42-/SnO2在由草酸和异戊醇反应生成草酸二异戊酯过程中,具有良好的催化活性,在最佳条件下,草酸二异戊酯收率达到了95.4%。     

碳酸二甲酯与苯酚酯交换合成碳酸二苯酯研究

选择Lewis酸催化剂、分子筛催化剂、有机钛和锡化合物催化剂和不同负载型金属氧化物催化剂用于碳酸二甲酯(DMC)与苯酚酯交换合成碳酸二苯酯(DPC)的过程。试验结果表明,：MoO3/SiO2和TiO2／SiO2催化剂对该反应具有相对较好的催化活性和选择性。以MoO3／SiO2为催化剂,DMC转化率和DPC选择性分别为24.3％和37.6％;以TiO2／SiO2,为催化剂,DMC转化率和DPC选择性分别为13.7％和20.0％。在该酯交换反应中,SiO2与Al2O3和MgO相比,是一种良好的催化剂载体。     

A bimetallic molybdenum (VI) and stannum (IV) catalyst for the transesterification of dimethyl oxalate with phenol

The transesterification of dimethyl oxalate (DMO) with phenol to methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO) was carried out in liquid phase under facile catalytic conditions. A series of bimetallic, MoO₃–SnO₂/SiO₂, catalysts with various Mo and Sn content were prepared by sequential impregnation of cationic Mo species and cationic Sn complexes using impregnation method. The effects of mass ratio of Mo:Sn, amount of Sn additive, and Mo(Sn) laoding amount on activities of transesterification of dimethyl oxalate with phenol were investigated. The evaluation results showed that MoO₃–SnO₂/SiO₂ catalyst with 14 wt% Mo(Sn) content performed best, giving 74.6% DMO conversion and 99.5% selectivity to MPO and DPO. This new heterogeneous catalyst provided not only an excellent selectivity (99% to MPO and DPO) and high yield of MPO and DPO but also a simple and practical protocol for DPC synthesis.     

Reactivity and surface properties of silica supported molybdenum oxide catalysts for the transesterification of dimethyl oxalate with phenol

A series of MoO₃/SiO₂ catalysts were prepared with Mo loadings ranging from 1 to 16 wt% and applied to the transesterification of dimethyl oxalate (DMO) with phenol. The results showed that the catalyst of MoO₃/SiO₂ with 1 wt% Mo content performed best, giving 54.6% conversion of DMO and 99.6% selectivity to target products, methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO). The surface properties were investigated by means of X-ray diffraction (XRD), X-ray photoelectron (XPS), BET specific surface area, temperature-programmed desorption (TPD) of ammonia, and FTIR analysis of adsorbed pyridine. XPS and XRD analyses indicated that Mo(VI) species was highly dispersed at low Mo loading and MoO₃ of the crystal structure appeared at higher loading. NH₃-TPD characterization and FTIR analysis of adsorbed pyridine demonstrated that only Lewis weak acids were present on catalyst surface and the amount of Mo loading has little effect on the strength of the surface acid on MoO₃/SiO₂. The catalytic results exhibited that the synergetic effect of Mo active centers with weak Lewis acid sites catalyzed transesterification of DMO with phenol.     

溶胶-凝胶法制备草酸二甲酯加氢Cu/SiO2催化剂及性能

以正硅酸乙酯为硅源,采用溶胶-凝胶法制备草酸二甲酯加氢合成乙二醇的Cu/SiO₂催化剂,并考察老化时间对Cu/SiO₂催化剂活性与结构的影响。用N2物理吸附、XRD、FT-IR和H₂-TPR等技术对Cu/SiO₂催化剂性能与结构进行表征。结果表明,溶胶-凝胶法制备的Cu/SiO₂催化剂中有层状硅酸铜形成,铜物种均匀分布在载体SiO₂上,易被还原,活性较高。合理的老化时间可抑制SiO₂对催化剂表面活性位的包覆,提高活性。在200 ℃、2.0 MPa、氢酯物质的量比60∶1、草酸二甲酯空速1.0 h^-1和老化时间1.5 h的条件下,草酸二甲酯转化率达99.51%,乙二醇选择性93.60%。
     

The catalytic activity of CuNi-containing hydrotalcites in the transesterification of dimethyl oxalate with phenol

Under microwave irradiation, a series of hydrotalcite-like compounds (HTL) were prepared in a short time of 10 min. The thus synthesized samples were applied to the catalytic transesterification of dimethyl oxalate (DMO) with phenol, CuNi-containing hydrotalcites (CuNi-HTLR) were found to exhibit good catalytic properties. When the reaction was performed with phenol/DMO molar ratio of 4:1 and 1.9% CuNi-HTLR based on the total weight of reactants as catalyst, at 180 °C for 10 h, the conversion of DMO and the selectivity of MPO + DPO reached over 66% and 95%, respectively.     

液相还原温度对草酸酯加氢制乙醇酸甲酯银硅催化剂性能的影响

以表面氨基功能化修饰的介孔二氧化硅纳米微球(AS)为载体,乙醇为还原剂,通过调变前体AgNO₃的还原温度,制得了四种不同银催化剂(Ag/AS),结合催化剂表征技术和催化性能研究,探讨了液相还原温度对银硅催化剂上草酸二甲酯(DMO)加氢制乙醇酸甲酯(MG)反应性能的影响规律。X射线衍射、氮气物理吸附、透射电镜、X射线光电子能谱等研究结果表明,Ag/AS催化剂随着还原温度的升高Ag颗粒的平均粒径呈指数型增大,对应的表面Ag原子配位数也随之增大。DMO吸附的原位红外光谱和DMO程序升温脱附实验表明,还原温度升高引起的表面原子配位数的增大,减弱了DMO在催化剂上的吸附进而降低了DMO加氢制MG的活性。     

Effect of alkyl nitrite decomposition on catalytic performance of CO coupling reaction over supported palladium catalyst

The syntheses of dimethyl oxalate (DMO) and diethyl oxalate (DEO) by CO coupling reaction in gaseous phase were investigated in a fixed bed reactor over Pd-Fe/Al₂O₃ catalyst. The catalytic performance was characterized by CO conversion, space-time yield (STY) and selectivity of DMO (or DEO). The results showed that over Pd-Fe/Al₂O₃ catalyst, the STY of DMO was higher than that of DEO under the same reaction conditions. The optimum reaction temperatures for synthesizing DMO and DEO were 403 K and 393 K, respectively, at the molar ratio 1 ∶ 1 of alkyl nitrite to CO. The difference in synthesizing DMO and DEO on the same catalyst was attributed to the decomposition performances of methyl nitrite (MN) and ethyl nitrite (EN), as density functional theory (DFT) calculation showed that EN decomposed more easily than MN.     

草酸二甲酯加氢制乙二醇Cu/SiO_2催化剂失活研究

采用沉积-沉淀法制备Cu/SiO_2催化剂,研究Cu/SiO_2催化剂在草酸二甲酯制乙二醇反应中的活性及稳定性。采用XRD、TG、SEM和EDS等对催化剂进行表征,分析催化剂的失活原因。结果表明,催化剂表面积炭和活性组分铜的烧结是造成催化剂失活的主要原因。在高空速1.5 h~(-1)下,对催化剂进行寿命考察,结果表明,运行350 h,草酸二甲酯转化率维持95%以上,乙二醇选择性下降至约60%。     

草酸二甲酯加氢制乙二醇Cu/SiO2催化剂的制备与改性

采用均匀沉淀沉积法制备Cu/SiO₂催化剂。考察了Cu²⁺浓度、洗涤条件及铜与硅物质的量比等的影响,并通过BET和XRD等表征手段研究分析,结果表明,前驱体制备过程及条件对催化剂结构和活性有较大影响。低Cu²⁺浓度、醇洗干燥均有利于形成大孔径高活性的催化剂。铜与硅物质的量比对反应活性的影响较大,存在一个最佳值,在0.4时活性最高。最优条件下制得的催化剂用于草酸二甲酯加氢制乙二醇,在反应温度205 ℃、压力2 MPa、n(H₂) ∶n(DMO)=80和空速1.0 h^-1条件下,草酸二甲酯的转化率为100%,乙二醇选择性为99.1%,乙醇酸甲酯选择性为0.9%,无其他副产物生成。     

Cu/SiO2催化剂上草酸二甲酯加氢反应的研究

对草酸二甲酯气相催化加氢反应体系进行了热力学分析和实验研究,考查了Cu／SiO2催化剂的最佳活化温度,对影响产物组成的因素和分布规律进行了讨论。结果表明,催化剂的适宜还原温度为523～623K;低氢酯比低压和高溶剂比有利于乙醇酸甲酯的生成;提高氢酯比或反应压力可以提高乙二醇的选择性,氢酯比和反应压力的适宜组合均能得到较好的草酸二甲酯转化率和乙二醇选择性。产物组成随草酸二甲酯转化率增加呈一定的变化规律,可根据市场需求调整产物结构,获得最佳的经济效益。