Synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification: Catalyst screening and reaction optimization

The synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification is reported. Firstly, a catalyst screening has been performed by studying the influence of different basic and acid homogeneous and heterogeneous catalysts on reaction results. Catalytic activity is extremely low for acidic catalysts indicating that reaction rate is very slow. On the contrary, high conversions and yields are obtained for basic catalysts. Catalytic activity increases with catalyst basic strength. The best heterogeneous catalyst is CaO. Calcination of CaO increases dramatically its activity due to calcium hydroxide removal from its surface. A reaction optimization study has been carried out with CaO as catalyst by using a factorial design of experiments leading to operation conditions for achieving a 100% conversion and a >95% yield at 1.5 h reaction time: 95 °C, catalyst/glycerol molar ratio = 0.06 and dimethyl carbonate/glycerol molar ratio = 3.5. Carbonate glycerol can be easily isolated by filtering the catalyst out and evaporating the filtrate at vacuum. Leaching of catalyst in reaction medium was lower than 0.34%. Catalyst recycling leads to a quick decrease in both conversions and yields probably due to a combination of catalyst deactivation by CaO exposure to air between catalytic runs, and a decrease in the catalyst surface area available for reaction due to particle agglomeration.     

Transesterification of karanja (Pongamia pinnata) oil by solid basic catalysts

The transesterification of karanja oil with methanol was carried out using solid basic catalysts. Alkali metal‐impregnated calcium oxide catalysts, due to their strong basicity, catalyze the transesterification of triacylglycerols. The alkali metal (Li, Na, K)‐doped calcium oxide catalysts were prepared and used for the transesterification of karanja oil containing 0.48–5.75% of free fatty acids (FFA). The reaction conditions, such as catalyst concentration, reaction temperature and molar ratio of methanol/oil, were optimized with the solid basic Li/CaO catalyst. This catalyst, at a concentration of 2 wt‐%, resulted in 94.9 wt‐% of methyl esters in 8 h at a reaction temperature of 65 °C and a 12 : 1 molar ratio of methanol to oil, during methanolysis of karanja oil having 1.45% FFA. The yield of methyl esters decreased from 94.9 to 90.3 wt‐% when the FFA content of karanja oil was increased from 0.48 to 5.75%. The performance of this catalyst was not significantly affected in the presence of a high FFA content up to 5.75%. The catalytic activities of Na/CaO and K/CaO were also studied at the optimized reaction conditions. In these two cases, the reaction initially proceeds slowly, however, leading to similar yields as in the case of Li/CaO after 8 h of reaction time. The purified karanja methyl esters have an acid value of 0.36 mg KOH/g and an ester content of 98.6 wt‐%, which satisfy the American as well as the European specifications for biodiesel in terms of acid value and ester content.     

Preparation and Characterization of CaO/MgO Catalyst and Its Application for Transesterification of n-Butyl Acetate with Methanol

This work reports the synthesis and characterization of CaO/MgO mixed oxide with different CaO/MgO mass ratios prepared by the co-precipitation method in a basic medium and subsequent calcination of the precursors. These mixed-oxide materials were characterized by XRD, FT-IR, SEM, and BET. The alkalinity of samples was determined by CO₂ temperature-programmed desorption (CO₂-TPD). Results show that the CaO/MgO samples contained mixed crystalline phases of cubic CaO and hexagonal MgO species. Decreasing the CaO/MgO ratio resulted in low average pore diameter and enhanced BET surface area.

Transesterification of n-butyl acetate with methanol was studied using a CaO/MgO catalyst at atmospheric pressure and 95°C, a model reaction to evaluate the potential of these catalysts for biodiesel production. The highest activity was found for a CaO/MgO mass ratio of 8:2 with conversion percentage of 83. The effects of calcination temperature, reaction time, reaction temperature, methanol/n-butyl acetate molar ratio, and catalyst recycling were investigated.     

Transesterification of Refined Sunflower Oil to Biodiesel Using a CaO/ZSM-5 Powder Catalyst

The production of biodiesel from refined sunflower vegetable oil over basic CaO/ZSM-5 catalysts was investigated. Several catalysts with various loadings of CaO on ZSM-5 were prepared, calcined at 800 °C, and characterized by N₂ adsorption-desorption, X-ray diffraction, Fourier transform infrared spectroscopy, and CO₂-temperature-programmed desorption techniques. Calcined catalysts were tested in the transesterification reaction and reaction conditions were optimized by varying the catalyst-to-oil ratio and reaction time. The most active catalyst was the CaO/ZSM-5 catalyst with a 35 wt % loading which gave the highest fatty acid methyl ester yield. The high catalytic activity was attributed to the active basic sites generated following CaO addition. Furthermore, the catalyst demonstrated stability against the leaching process.     

CaO对CH4-CO2重整反应催化剂性能的影响

采用浸渍法制备了Ni/CaO-γ-Al2O3系列催化剂,并通过固定床连续反应考察了催化剂在CH4-CO2重整反应中的活性。结果表明：CaO助剂的加入能提高Ni基催化剂的活性,以CaO含量5%为最佳;采用共浸渍法制得的催化剂活性较高;焙烧温度723 K和还原温度823 K时催化剂活性较高;使用最佳条件下制得的催化剂,973 K下进行CH4-CO2重整反应,总碳转化率达到83.4%。     

非均相固体碱催化剂(CaO体系)用于生物柴油的制备

为解决生物柴油酯交换过程中的产物与催化剂分离问题,制备了负载型固体碱催化剂（CaO/SiO₂、CaO/Al₂O₃和CaO/MgO体系）,考察该系列催化剂在生物柴油制备中的不同反应特点,对制备的催化剂进行XRD表征,研究了反应条件对反应的影响。结果表明,CaO可以很好地分散在催化剂载体上,该体系催化剂是制备生物柴油的良好非均相催化剂。催化剂的最佳制备条件为：焙烧温度700 ℃,催化剂质量分数为原料油的1%,m（醇）∶m（油）＝18∶1,反应温度60～65 ℃,反应时间10 h。     

NaF/CaO固体碱催化制备生物柴油

采用等体积浸渍法制备了NaF/CaO催化剂,用于催化大豆油与甲醇酯交换反应制备生物柴油。考察了催化剂制备条件和反应条件对酯交换反应的影响。结果表明,通过等体积浸渍法、500℃焙烧4h和NaF与CaO的质量比6:1制得的催化剂,在70℃、催化剂用量为油质量的8%、醇油物质的量比9:1和反应2 h条件下,生物柴油收率可达95%。与单纯的CaO相比,NaF/CaO催化剂的催化活性明显提高。用共聚焦拉曼光谱考察了催化剂的表面特征。     

KOH负载的不同催化剂催化合成生物柴油

采用湿法浸渍法研究了五种KOH负载的催化剂催化合成生物柴油反应,并采用XRD﹑SEM﹑CO2-TPD等方法对其进行结构和性能表征。结果表明,15%(质量分数,下同)KOH负载的CaO催化酯化活性最高,在醇油摩尔比16∶1,反应温度65℃,催化剂加入量为4%条件下,反应1h,脂肪酸甲酯收率达到97.1%。KOH负载的CaO催化剂中出现了K2O的晶相,15%CaO/KOH催化剂有更多的活性位点,有利于生物柴油酯交换反应。     

Zn-Mg复合氧化物催化大豆油甘油解合成单甘酯

采用共沉淀法制备了一系列不同Zn、Mg物质的量比的Zn-Mg复合氧化物,将其用于催化大豆油甘油解合成单甘酯(MG),采用XRD、氮气吸附-脱附仪、SEM、TEM对Zn-Mg复合氧化物结构与性能进行了表征,并测定了催化剂的表面碱强和碱量。优化了合成单甘酯的工艺条件,并考察了Zn-Mg复合氧化物的重复使用性能。结果表明,改变Zn、Mg物质的量比不仅可以调控Zn-Mg复合氧化物的碱强与碱量,还可以调控其比表面积、孔容等结构参数;不同Zn、Mg物质的量比复合氧化物的催化活性变化趋势与其碱强度(H)在15.0H17.2间碱量变化趋势相一致;n(Zn)/n(Mg)=0.1时,复合氧化物(ZM0.1)具有最好的催化甘油解反应活性;使用该催化剂合成单甘酯的适宜条件为:n(甘油)∶n(大豆油)=3∶1,反应温度210℃,反应时间2 h,催化剂用量为大豆油质量的0.6%,该条件下大豆油转化率达95.6%,单甘酯收率为58.5%。ZM0.1催化剂重复使用4次时大豆油转化率仍达80.9%。     

尿素和甲醇反应制氨基甲酸甲酯的研究

尿素和甲醇在自制催化剂作用下制备氨基甲酸甲酯（MC）,通过测试分析计算MC的收率,比较不同方法制备出的负载型金属氧化物催化剂的催化活性,并对活性好的催化剂进行SEM和XRD表征。实验结果表明,金属氧化物负载型催化剂中ZnO-KOH对合成氨基甲酸甲酯具有较高的催化活性,其反应优化条件为：n(甲醇)∶n(尿素)＝60、催化剂ZnO-KOH用量为甲醇和尿素质量的4％、反应时间为8 h和反应温度为185 ℃,MC的收率可达84.46％。     

Transesterification of soybean oil to biodiesel using CaO as a solid base catalyst

In this study, transesterification of soybean oil to biodiesel using CaO as a solid base catalyst was studied. The reaction mechanism was proposed and the separate effects of the molar ratio of methanol to oil, reaction temperature, mass ratio of catalyst to oil and water content were investigated. The experimental results showed that a 12:1 molar ratio of methanol to oil, addition of 8% CaO catalyst, 65 °C reaction temperature and 2.03% water content in methanol gave the best results, and the biodiesel yield exceeded 95% at 3 h. The catalyst lifetime was longer than that of calcined K₂CO₃/γ-Al₂O₃ and KF/γ-Al₂O₃ catalysts. CaO maintained sustained activity even after being repeatedly used for 20 cycles and the biodiesel yield at 1.5 h was not affected much in the repeated experiments.     

Ultrasonic-assisted biodiesel production process from palm oil using alkaline earth metal oxides as the heterogeneous catalysts

The ultrasonic-assisted transesterification of palm oil in the presence of alkaline earth metal oxide catalysts (CaO, SrO and BaO) was investigated. Batch process assisted by 20 kHz ultrasonic cavitation was carried out to study the effect of reaction time (10-60 min), alcohol to palm oil molar ratio (3:1-15:1), catalysts loading (0.5-3%) and varying of ultrasonic amplitudes (25-100%). The activities of the catalysts were mainly related to their basic strength. The catalytic activity was in the sequence of CaO < SrO < BaO. At optimum conditions, 60 min was required to achieve 95% yield compared to 2-4 h with conventional stirring. Also, the yields achieved in 60 min increased from 5.5% to 77.3% (CaO), 48.2% to 95.2% (SrO), and 67.3% to 95.2 (BaO). Fifty percentage amplitude of ultrasonic irradiation was deemed the most suitable value and physical changes on the catalysts after the ultrasonic-assisted reaction were successfully elucidated. BaO catalyst underwent relatively more severe activity drop in the catalyst reusability test. Catalysts dissolution was found to be mainly responsible for activity drop of the reused catalysts, especially with BaO catalyst.     

Zn–Ca–Al mixed oxide as efficient catalyst for synthesis of propylene carbonate from urea and 1,2-propylene glycol

A series of Zn–Ca–Al oxides with different CaO and ZnO contents have been prepared and evaluated in the synthesis of propylene carbonate(PC) from 1,2-propylene glycol(PG) and urea in a batch reactor. The effect of catalyst composition, basicity and reaction process parameters such as temperature, catalyst dose, molar ratio of PG to urea, purge gas flow and reaction time has been studied to find suitable reaction conditions for the PC synthesis. The PC selectivity and yield under the desired conditions could reach 98.4% and 90.8%, respectively. The best performing catalyst also exhibited a good reusability without appreciable loss in the PC selectivity and yield after five consecutive reaction runs. In addition, a stepwise reaction pathway involving a 2-hydroxypropyl carbamate intermediate was proposed for the urea alcoholysis to PC in the presence of Zn–Ca–Al catalysts, according to the time dependences of reaction intermediates and products.     

Methane Dehydroaromatization on Mo/HMCM-22 Catalysts: Effect of SiO2/Al2O3 Ratio of HMCM-22 Zeolite Supports

Zn/I₂ was found to be a practical and effective catalyst for the transesterification of soybean oil with methanol. A study for optimizing the reaction conditions such as the molar ratio of methanol to oil, the reaction time and the catalyst amount, was performed. The highest conversion of 96% was obtained under the optimum conditions. Further, the effect of free fatty acids and water in the soybean oil on the catalytic activity of the catalysts was also investigated.     

Preparation of silica‐supported late transition metal catalyst and ethylene polymerization

A Correction has been published for this article in Polymer International 51(6) 2002, 561 The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si? O? Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst. The late transition metal catalyst 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine iron(II) chloride was supported on silica. Fourier transform infrared spectroscopy, scanning electronic micrograph and X‐ray photoelectron spectroscopy measurements were utilized to examine the process of supporting catalyst on silica and investigate the possible mechanism of support. Furthermore, ethylene polymerizations with the supported catalysts were carried out in various conditions such as different reaction temperatures and Al/Fe molar ratios. The results showed that MAO first reacted with the hydroxyl of silica forming Si? O? Al bonds and then the catalyst was bridged through MAO on the surface of silica. Compared with homogeneous catalysts, the supported catalysts show some decrease in catalyst activity. However, they can show good activity at a lower Al/Fe molar ratio with MAO as co‐catalyst and give rise to higher molecular weight and melting temperature of the polymer. Better morphology of polyethylene was obtained by a supported catalyst than by its corresponding homogeneous catalyst. © 2002 Society of Chemical Industry     

溴系阻燃剂五溴甲苯的合成新工艺研究

由甲苯经溴化制得五溴甲苯,重点考察了催化剂掺杂质量比、催化剂的用量、原料配比、反应时间等工艺参数对合成产物的影响.实验结果表明,m(Bu2SnCl2):m(AlCl3)=1:1作为复合催化剂,对合成五溴甲苯有着良好的催化活性,当m(复合催化剂):m(甲苯)=0.05,n(甲苯):n(溴)=1:7.5,n(溶剂CCl4)...     

Biodiesel production from soybean oil using modified calcium loaded on rice husk activated carbon as a low-cost basic catalyst

Activated carbon was obtained by hydrothermal process using rice husk as raw materials. The study in our lab had been developed to produce high-quality biodiesel from soybean oil with the activated carbon-base catalyst. The polyethylene glycol (PEG 400) modified calcium loaded on the rice husk activated carbon (CaO/AC) catalyst was prepared via the dipping method and then was used as a heterogeneous solid-base catalyst to produce biodiesel. The effects of CaO/AC ratio and calcination time on catalytic performance were researched according to the yield of biodiesel, and the optimum reaction conditions for biodiesel from soybean oil via PEG 400–modified CaO/AC catalyst were evaluated. The results showed that the yield of fatty acid methyl ester (FAME) achieved 93.01% at the reaction temperature of 342 K, methanol/oil molar ratio of 10:1, and reaction time of 6 h. All in all, modified CaO/AC catalyst showed very high activity for transesterification of soybean oil and had catalytic repeated availability.     

反应条件下多孔催化剂上有效扩散系数及曲节因子的分析计算

采用CDS－810微反系统,在实验条件为：常压、氢苯比3.0-8.0、温度363.15K-453.15K时,进行了在四种不同粒度Ni/Al2O3催化剂上的气相苯加氢反应,利用实验数据计算了不同反应组成、不同反应速率时苯的有效扩散系数、反应死区及催化剂的曲节因子。计算结果表明：有效扩散系数不随反应速率改变,多孔催化剂的曲节因子可以看作多孔催化剂的结构参数,不随反应条件变化。     

Transesterification of edible and non-edible oils over basic solid Mg/Zr catalysts

A series of Mg–Zr catalysts with varying Mg to Zr ratios was prepared by co-precipitation method. These catalysts were characterized by BET surface area, X-ray diffraction, X-ray photo electron spectroscopy and temperature programmed desorption of CO₂. The catalytic activity of these catalysts was evaluated for the room temperature transesterification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst with Mg/Zr (2:1 wt./wt.%) exhibited exceptional activity towards transesterification reaction within short reaction time. The effects of different reaction parameters such as catalyst to oil mass ratio, reaction temperature, reaction time and methanol to oil molar ratio were studied to optimize the reaction conditions. The reasons for the observed activity of these catalysts are discussed in terms of their basicity and other physico-chemical properties.     

稀土复合固体酸催化合成棕榈酸生物柴油的研究

用溶胶凝胶法制备稀土复合固体酸催化剂SO₄^2-/TiO₂/Ce⁴⁺,将其用于棕榈酸与甲醇的加压酯化反应.考察了不同制备条件对催化剂性能的影响,并对其结构进行表征.结果表明,在Ce⁴⁺浓度0.05 mol/L、H₂SO₄浓度1.38 mol/L、煅烧温度450 ℃和煅烧时间3 h的制备条件下,催化剂活性最高.棕榈酸与甲醇的加压酯化反应最佳工艺条件为:醇酸物质的量之比10:1、反应温度110 ℃、反应时间30 min、催化剂用量3%,此时转化率可达到96.33%.催化剂在重复使用4次后,转化率仍在50%以上.