过渡金属改性Mg-Al基固体碱催化剂上碳酸丙烯酯与甲醇合成碳酸二甲酯的研究

以共沉淀法制备了一系列不同价态过渡金属(Fe、Cu、Zr)改性的Mg-Al固体碱催化剂,考察了其对于甲醇与碳酸丙烯酯(PC)酯交换合成碳酸二甲酯的反应性能。采用XRD、N_2吸附-脱附、FT-IR、XPS、CO_2-TPD等手段对催化剂的物理化学性质进行了表征。结果表明,催化剂的碱强度、碱密度是影响催化活性的主要因素,不同价态过渡金属的加入可以调控Mg-Al固体催化剂的碱性。在考察的催化剂中,FeMgAl催化剂具有最高的表面碱密度,因此,表现出最好的催化性能。在温度为65℃、时间为4 h、甲醇与PC物质的量比为10∶1、催化剂用量为4%的反应条件下,PC转化率可达66.2%。     

以Ca-M-Al(M=Mg,La,Ce,Y)层状双氢氧化物为前驱体的固体碱用于 酯交换合成碳酸二甲酯

碳酸二甲酯(DMC)是一种环境友好型绿色化学品,可作为甲基化和羰基化试剂用于取代传统剧毒的硫酸二甲酯和光气.另外,DMC具有良好的溶解性能,可用于高级溶剂;DMC分子中具有高的氧含量,可用作汽油添加剂来提高汽油的辛烷值;DMC还可用作聚碳酸酯的原料.随着人们环保意识的不断增强,DMC的生产和应用呈现出巨大的吸引力和市场潜力.DMC合成方法主要有光气法、甲醇氧化羰化法、尿素醇解法及酯交换法等.酯交换法具有反应条件温和、产率高等优点,是目前工业制备DMC的主要方法.研究发现,相对于酸性催化剂,碱性催化剂更有利于酯交换法合成DMC.金属氧化物催化剂具有活性高、热稳定性高及可连续重复回收利用等优点,因而引起了广泛关注.CaO对于酯交换合成DMC反应具有良好的催化活性,但其稳定性差.因此,通常采用复合金属氧化物来促进CaO的分散,并增加金属间相互作用以防止CaO流失.研究发现,经煅烧后的Mg-Al,Ca-Al和Ca-Mg-Al催化剂对于酯交换反应具有高的活性和稳定性.此外,通过碱性稀土金属(La,Ce和Y)的引入可以修饰催化剂上的碱性位点,从而调变催化剂的碱性.本文合成了一系列以Ca-M-Al(M=Mg,La,Ce,Y)层状双氢氧化物为前驱体的固体碱催化剂,将其用于甲醇与碳酸丙烯酯酯交换合成DMC.通过X射线衍射、热重分析、红外光谱、X射线光电子能谱、电感耦合等离子体、CO2程序升温脱附和Hammett指示剂对催化剂进行了表征.研究发现,各催化剂的活性高低依次为:Ca-Y-Al相似文献   

以Ca-M-Al(M=Mg,La,Ce,Y)层状双氢氧化物为前驱体的固体碱用于酯交换合成碳酸二甲酯（英文）

碳酸二甲酯(DMC)是一种环境友好型绿色化学品,可作为甲基化和羰基化试剂用于取代传统剧毒的硫酸二甲酯和光气.另外,DMC具有良好的溶解性能,可用于高级溶剂;DMC分子中具有高的氧含量,可用作汽油添加剂来提高汽油的辛烷值;DMC还可用作聚碳酸酯的原料.随着人们环保意识的不断增强,DMC的生产和应用呈现出巨大的吸引力和市场潜力.DMC合成方法主要有光气法、甲醇氧化羰化法、尿素醇解法及酯交换法等.酯交换法具有反应条件温和、产率高等优点,是目前工业制备DMC的主要方法.研究发现,相对于酸性催化剂,碱性催化剂更有利于酯交换法合成DMC.金属氧化物催化剂具有活性高、热稳定性高及可连续重复回收利用等优点,因而引起了广泛关注.CaO对于酯交换合成DMC反应具有良好的催化活性,但其稳定性差.因此,通常采用复合金属氧化物来促进CaO的分散,并增加金属间相互作用以防止CaO流失.研究发现,经煅烧后的Mg-Al,Ca-Al和Ca-Mg-Al催化剂对于酯交换反应具有高的活性和稳定性.此外,通过碱性稀土金属(La,Ce和Y)的引入可以修饰催化剂上的碱性位点,从而调变催化剂的碱性.本文合成了一系列以Ca-M-Al(M=Mg,La,Ce,Y)层状双氢氧化物为前驱体的固体碱催化剂,将其用于甲醇与碳酸丙烯酯酯交换合成DMC.通过X射线衍射、热重分析、红外光谱、X射线光电子能谱、电感耦合等离子体、CO_2程序升温脱附和Hammett指示剂对催化剂进行了表征.研究发现,各催化剂的活性高低依次为:Ca-Y-AlCa-AlCa-Ce-AlCa-La-AlCa-Mg-Al,这与催化剂表面总碱量相一致.通过Mg和La的引入,催化剂表面出现了超强碱性位.其中,Ca-Mg-Al催化剂表面具有最高的(Ca+Mg):Al原子比,从而导致催化剂表面产生更多的不饱和O~(2-)离子,因而具有最高的碱性位数量.此外,通过Mg,La,Ce和Y的引入,催化剂的重复使用性能得到了提高.特别是Ca-Mg-Al催化剂,在10次循环后仍保持着高的活性,且其结构没有发生显著变化,表明其稳定性较高,因此该催化剂在非均相催化中具有高的应用价值.     

氧化钙室温催化碳酸丙烯酯和甲醇的酯交换合成碳酸二甲酯

 在室温条件下用氧化钙催化碳酸丙烯酯（PC）和甲醇的酯交换反应，高收率、高选择性地合成了碳酸二甲酯（DMC）．在假设羟丙基甲基碳酸酯（HPMC）是反应中间产物的基础上，计算了甲醇、PC和HPMC的电荷分布，并推论出可能的副反应PC的聚合．通过考察反应温度对DMC选择性和收率的影响，证明了关于中间体HPMC和副反应PC聚合的假设．考察了加料顺序、反应温度对DMC生成速率的影响，并在此基础上提出了氧化钙催化PC和甲醇酯交换合成DMC的可能机理．     

超声作用下KF/CaO催化酯交换反应制备生物柴油

等体积浸渍法制备了KF/CaO固体碱催化剂,用于催化大豆油与甲醇酯交换反应制备生物柴油,在反应体系中引入超声作为辅助条件。研究表明,KF/CaO催化活性高。在超声的辅助作用下,酯交换反应速率加快,生物柴油的收率提高。实验考察了反应条件对产品中脂肪酸甲酯含量的影响。醇油摩尔比为12∶1,反应温度65℃,催化剂与大豆油的质量比为3%,反应1 h,超声频率20 kHz,超声声强1.01 W/cm2,在此反应条件下,产品中脂肪酸甲酯的质量分数达到99.6%。     

过渡金属助剂改性Ca-Zr催化剂上甲醇与碳酸丙烯酯反应制备碳酸二甲酯

采用溶胶凝胶法制备了一系列由过渡金属助剂改性的Ca-Zr催化剂，对其低温下甲醇与碳酸丙烯酯(PC)酯交换反应合成碳酸二甲酯(DMC)的催化性能进行了研究。结果表明，系列过渡金属改性的Ca-Zr催化剂上DMC选择性的顺序依次为Co-Ca-Zr> Cu-Ca-Zr> Ca-Zr> Fe-Ca-Zr> Ni-Ca-Zr> Zn-Ca-Zr。其中，Co改性的Co-Ca-Zr催化剂在35℃、甲醇/PC物质的量比为15及催化剂用量为4%的条件下反应2 h,PC的转化率可达84.3%,DMC的选择性可达94.5%。结合XRD、FT-IR、XPS和CO₂-TPD等表征结果发现，催化剂的碱性位强度增加可以提高PC的转化率，而总碱性位含量提高则降低DMC的选择性。Co改性的Ca-Zr催化剂具有最少的碱性位和最高的强碱性位站比，因而表现出较高的PC转化率和DMC选择性。     

KNO3/AlSBA-15分子筛催化合成碳酸二丙酯的研究

研究了KNO3/AlSBA-15负载型分子筛催化剂用于碳酸二甲酯(DMC)与丙醇的酯交换合成碳酸二丙酯(DPC)反应.分别考察了载体的制备方法,活性组分的负载量,催化剂的活化温度及反应时间等因素对催化活性的影响,研究表明该催化剂对于这一反应具有较高的催化活性.当摩尔比DMC∶丙醇=1∶4,催化剂用量为反应物总质量的3%,反应温度为90℃,反应时间为6h时,DPC的选择性为96.0%,收率为90.2%.     

Zn-Al水滑石催化碳酸二甲酯与苯酚酯交换反应的研究

用共沉淀法制备了Zn-Al水滑石,并用于多相催化酯交换合成碳酸二苯酯的反应.研究了不同n(Zn)/n(Al)比的水滑石及其焙烧产物等对酯交换反应的催化活性.结果表明,Zn-Al水滑石催化剂对该反应的催化活性和选择性很高,当n(Zn)/n(Al)=3时,在150～180℃,n(PhOH)/n(DMC)=2,催化剂用量为反应物总质量的1.5%,在反应时间为12h的条件下,DMC的转化率达到55.9%,DPC和MPC的收率分别为25.3%和27.0%,酯交换产物的选择性达到93.6%.利用XRD,TG-DTA和TEM等手段对催化剂进行了表征.     

CaO@SiO_2纳米固体碱的制备、表征及其大豆油酯交换反应催化性能

采用溶胶-凝胶法合成Ca O@Si O_2固体碱催化剂,以聚苯乙烯有机聚合物为硬模板剂和以P123为软模板剂对Ca O的微观形貌进行调控。并将其应用于大豆油与甲醇的酯交换制备生物柴油的反应体系中。通过对Ca O@Si O_2纳米固体碱催化剂进行X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电镜(TEM)、CO_2-TPD及N_2的吸附-脱附(BET)表征发现,不仅制备得到了形貌归整的纳米固体颗粒,而且得到了Ca O包裹在Si O_2表面的核壳结构。进一步考察了不同的硅钙质量比、反应温度、催化剂的用量以及油醇物质的量比对生物柴油收率的影响,生物柴油的收率最高可以达到95.6%。     

淀粉基炭负载纳米铜催化合成碳酸二甲酯

以硝酸铜和可溶性淀粉为原料, 经过溶胶-凝胶化过程、高温炭化和KOH活化得到炭负载铜催化剂(Cu/C), 采用扫描电镜、透射电镜、X射线衍射、热重-差热分析仪、N₂吸附和CO程序升温脱附对催化剂结构进行了表征, 并考察了它在甲醇氧化羰基化合成碳酸二甲酯(DMC)反应中的催化活性. 结果表明, 活化温度和KOH用量对催化剂的表面结构及金属铜粒子尺寸影响显著, 当活化温度为850℃, KOH:C=1 (质量比)时, Cu/C催化剂的比表面积达到1690 m²/g, 铜纳米粒子平均晶粒尺寸为30.4 nm, 催化活性最高, DMC时空收率达到235.7 mg·g^-1·h^-1, 甲醇转化率和DMC选择性分别为1.6%和76.5%.     

甲醇和碳酸丙烯酯合成碳酸二甲酯的研究

采用浸渍法以ZrO2为载体，以碱金属氢氧化物和碳酸盐为前驱体制备了不同的固体碱催化剂，在温和反应条件下考察了催化剂的酯交换扳应性能，并通过BET、XRD和CO2－TPD等方法对催化剂进行了表征，结果表明：Na2CO3负载到不同载体上，其催化性能明显不同，Na2CO3/ZrO2催化剂获得了较高的酯交换活性。载体的比表面和孔结构与催化剂的反应活性无一定的依存关系。而催化剂表面的酸碱性是影响酯交换活性的重要因素。     

Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯酯交换反应的研究

ZnO、La₂O₃和Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯反应制备碳酸二甲酯和乙二醇。催化剂采用共沉淀法进行制备,并用BET、XRD、TG-DSC、CO₂-TPD和Hammett滴定等对催化剂进行表征。考察了Zn-La物质的量比、焙烧温度,反应条件（反应温度、反应时间、催化剂用量等）对催化剂活性的影响。结果表明,ZnLa复合氧化物物质的量比为2：1,焙烧温度为500℃时,催化剂表现了较好的催化效果。催化剂的活性与催化剂表面的碱性强度和碱量有关,碱量越多催化剂的活性越好。     

Dimethyl carbonate synthesis via transesterification catalyzed by quaternary ammonium salt functionalized chitosan

A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate （DMC） synthesis by the transesterification of propylene carbonate （PC） with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products.     

KOH/4A分子筛催化剂对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应的催化性能

 首次开发出对环氧丙烷、二氧化碳和甲醇合成碳酸二甲酯反应具有较高活性和稳定性的KOH/4A分子筛固体催化剂,考察了反应温度和催化剂活性组分KOH的负载量等因素对催化剂性能的影响. 在优化的实验条件下,环氧丙烷可以完全转化,碳酸二甲酯的收率为168%. 从实验结果推测,产物碳酸二甲酯是由环氧丙烷和二氧化碳加成生成碳酸丙烯酯,然后与甲醇发生酯交换反应生成的,甲醇对环氧丙烷和二氧化碳合成碳酸丙烯酯反应具有助催化作用.     

Dimethyl carbonate synthesis catalyzed by DABCO-derived basic ionic liquids via transesterification of ethylene carbonate with methanol

Easily prepared DABCO-derived (1,4-diazobicyclo[2.2.2]octane) basic ionic liquids were developed for an efficient synthesis of dimethyl carbonate (DMC) via the transesterification of ethylene carbonate (EC) with methanol. 1-Butyl-4-azo-1-azoniabicyclo[2.2.2]octane hydroxide ([C₄DABCO]OH) exhibited high catalytic activity and 81% DMC yield together with 90% EC conversion was obtained under mild reaction conditions. Notably, the catalyst could be recycled for four times without loss of catalytic activity. Moreover, a possible mechanism was also discussed.     

Synthesis of dimethyl carbonate (dmc) from co2, ethylene oxide and methanol using heterogeneous anion exchange resins as catalysts

Summary A two-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol using heterogeneous anion exchange resins as catalysts is reported. The first step is the reaction of EO with CO₂ to form ethylene carbonate (EC), and the second one the transesterification of EC with methanol to yield DMC. Effect of various reaction parameters on the activity and selectivity of the catalysts used was investigated. After the first step, the crude mixture containing EC was directly reacted with methanol in the presence of a heterogeneous anion exchange resin catalyst to produce DMC in high yield and selectivity. Our process is highly economic.     

Dimethyl carbonate synthesis via transesterification of ethylene carbonate and methanol using ionic liquid catalysts immobilized on mesoporous cellular foams

Dimethyl carbonate (DMC) was synthesized via transesterification of ethylene carbonate and methanol with ionic liquid catalysts. For this reaction, 1,4-diazobicyclo[2.2.2]octane (DABCO), [Choline]OH, and [BMIM]Cl were used as a homogeneous catalyst, and hydrotalcite, [DABCO]OH@MCF, [DABCO]Cl@MCF, and DABCO/MCF were used as a heterogeneous catalyst. To support the ionic liquids, mesoporous cellular foam (MCF) was prepared and characterized by SEM, TEM and BET surface area analyzer. The average cell and window sizes of the prepared MCF were 34.4 and 21.3 nm, respectively. The prepared MCF had a well structured three-dimensional structure. Among the homogeneous catalysts used, DABCO showed the highest DMC yield about 84 %, and among the heterogeneous catalysts, [DABCO]OH@MCF showed the highest DMC yield about 77 %. In the reusability test of the used catalysts, there was only 8 % point decrease in DMC yield with [DABCO]OH@MCF, whereas 58 percent point decrease in DMC yield with DABCO/MCF after four times recycling tests. The effects of an anion on the catalytic activity were investigated. The optimum reaction condition for DMC synthesis was also investigated with [DABCO]OH@MCF catalyst.     

Synthesis of dimethyl carbonate and propylene glycol from transesterification of propylene carbonate and methanol using quaternary ammonium salt catalysts

Summary The synthesis of dimethyl carbonate (DMC) was investigated through the transesterification of propylene carbonate (PC) with methanol using quaternary ammonium salt catalysts. The reaction was carried out in an autoclave at 120-140 oC under carbon dioxide pressure of 250-400 psig. The main by-product was propylene glycol. The quaternary salts of larger alkyl group and more nucleophilic counter anion exhibited higher catalytic activity. Kinetic studies were also performed to better understand the reaction mechanism. Quaternary ammonium chlorides immobilized on polystyrene supports were also tested for their possible uses as heterogeneous catalysts.     

Heterogeneous synthesis of glycerol carbonate from glycerol and dimethyl carbonate catalyzed by LiCl/CaO

In this article, a CaO-based catalyst was prepared by impregnating chloride salts on CaO to develop a highly efficient heterogeneous catalyst for the synthesis of glycerol carbonate (GC) from glycerol and dimethyl carbonate. LiCl/CaO exhibited a high catalytic activity under moderate reaction conditions. The effects of the LiCl loadings, the amount of catalyst and the calcination temperature on the catalytic activity were investigated. The highest yield of 94.19% glycerol carbonate was obtained at 65 °C on CaO loaded with 10% LiCl after 1 h, and the catalyst had high stability in reusing work. Scanning electron microscopy (SEM), X-ray diffraction (XRD), BET, CO₂-TPD, XPS and thermalgravity (TG) were used to characterize the prepared catalyst. It was found that the high catalytic activity of CaO after modification with LiCl is associated with the structural aspects and the amount of basicity of the catalyst. The Li₂O₂ species, which is a strong basic site that is formed by the substitution of the Ca²⁺ in CaO lattice by Li⁺, has great activity for transesterification.