硫酸氢钠催化甲醛与甲酸甲酯的偶联反应

在釜式反应器中研究了硫酸氢钠催化甲醛和甲酸甲酯的偶联反应,考察了反应温度、原料配比、催化剂用量、反应时间等因素对乙醇酸甲酯和甲氧基乙酸甲酯收率的影响,得到最佳反应条件为：反应温度160℃、反应物料配比n(甲醛):n(甲酸甲酯)=0.65、催化剂的用量为总反应物料质量的20.0％、反应时间4h,在此条件下,乙醇酸甲酯和甲氧基乙酸甲酯的收率最大,总收率达到42.15％。催化剂浓度和反应温度对活化甲醛分子,确保有效地进行羰基化反应,提高反应活性起重要作用。硫酸氢钠难溶于反应体系,后处理简单,副反应少,可重复使用,较其它相关催化剂具有突出的性能。     

氨基磺酸催化甲醛和甲酸甲酯偶联反应的研究

在釜式反应器中研究了氨基磺酸催化甲醛和甲酸甲酯偶联反应，考察了反应温度、反应时间、原料配比和催化剂用量等因素对乙醇酸甲酯和甲氧基乙酸甲酯生成量的影响，最佳反应条件为: 反应温度150～160 ℃，反应时间4 h，n（甲醛）：n（甲酸甲酯）=05，在此条件下得到最大的乙醇酸甲酯和甲氧基乙酸甲酯的生成量，总生成量达到2134 mmol·(g-cat)-1。与其他催化剂的性能进行对比发现，氨基磺酸对催化甲醛和甲酸甲酯偶联反应显示出较好的催化性能。     

甲酸甲酯合成工艺评述

介绍了合成甲酸甲酯的六种工艺方法 ,即直接酯化法、甲醇羰基化法、甲醇脱氢法、甲醛二聚法、合成气直接合成法及二氧化碳与甲醇加氢缩合法 ,并分别进行了评述。其中已经工业化的有直接酯化法、甲醇羰基化法和甲醇气相催化脱氢法 ,另三种方法正在研究中。认为甲醇液相脱氢法具备传统气相法的所有优点 ,且反应温度低 ,能耗少 ,甲醇转化率高 ,产率亦高 ,是今后研究的主要方向     

Prospects of non-catalytic supercritical methyl acetate process in biodiesel production

Conventional biodiesel production methods utilize alcohol as acyl acceptor and produces glycerol as side product. Hence, with escalating production of biodiesel throughout the world, it leads to oversupply of glycerol and subsequently causes devaluation in the market. In this study, methyl acetate was employed as acyl acceptor in non-catalytic supercritical methyl acetate (SCMA) process to produce fatty acid methyl esters (FAME) and side product of triacetin, a valuable fuel additive instead of glycerol. Consequently, the properties of biodiesel produced (FAME and triacetin) are superior compared to conventional biodiesel method (FAME only). In this research, the effects of reaction temperature, reaction time and molar ratio of methyl acetate to oil on the yield of biodiesel were investigated. Apart from that, the influence of impurities commonly found in waste oils/fats such as free fatty acids and water were studied as well and compared with methanol-based reactions of supercritical and heterogeneous catalysis. Results show that biodiesel yields in SCMA process could achieve 99 wt.% when the operating conditions were fixed at 400 °C/220 bar for reaction temperature, methyl acetate/oil molar ratio of 30:1 and 60 min of reaction time. Furthermore, SCMA did not suffer from adverse effect with the presence of impurities, proving that SCMA has a high tolerance towards contamination which is crucial to allow the utilization of inexpensive waste oils/fats as biodiesel feedstock.     

不同载体负载Pd双功能催化剂制备及其液相甲醇催化一步合成甲酸甲酯

以γ-Al_2O_3、ZrO_2、Bentonite(膨润土)、MIL-53(Al)和MIL-53(Fe)为载体,采用浸渍法制备负载Pd双功能催化剂,利用XRD、BET和NH3-TPD等表征催化剂结构,在微型高压反应器中评价催化剂的液相甲醇一步催化转化合成甲酸甲酯的反应性能,考察反应条件对催化剂性能的影响。结果表明,不同载体负载Pd催化剂未观察到Pd的XRD特征峰,表明催化剂表面的Pd是高分散状态。不同载体负载Pd催化剂的比表面积、酸强度和酸量差别较大,并且酸强度和酸量对甲醇转化率和产物选择性有较大影响。具有较多中强酸的2%Pd/Bentonite、2%Pd/MIL-53(Al)和2%Pd/MIL-53(Fe)催化剂比中强酸较少的2%Pd/γ-Al_2O_3和2%Pd/ZrO_2催化剂具有更高的甲醇转化率和甲酸甲酯选择性。2%Pd/Bentonite催化剂在每摩尔甲醇Pd用量为0. 030 mmol、反应温度150℃、O_2压力2 MPa和反应时间5 h条件下,液相甲醇一步催化转化合成甲酸甲酯反应中,甲醇转化率56. 08%,甲酸甲酯选择性55. 85%。     

K/SiO_2催化醋酸甲酯与甲醛合成丙烯酸甲酯

以K/Si O_2为催化剂,利用醋酸甲酯与甲醛合成丙烯酸甲酯,分别考察了活性组分来源、负载量、浸渍条件以及催化剂焙烧温度对反应的影响。研究结果表明:采用硝酸钾作为钾源,催化剂具有较好的性能,醋酸甲酯的转化率为19.94%,丙烯酸甲酯收率为4.56%。K负载量低于15%时,增加负载量有利于提高催化活性,负载量为15%时,催化活性最高,醋酸甲酯转化率为23.5%,丙烯酸甲酯收率为6.8%。此外,浸渍条件和焙烧温度对催化剂性能也有较大的影响,超声浸渍可以提高活性组分在载体表面的分散度,有利于催化活性的提高;升高焙烧温度可以促进硝酸钾的分解,增强催化剂碱性强度,提高催化活性。     

Free radical terpolymerization of butyl acrylate/methyl methacrylate and alpha methyl styrene at high temperature

The free radical initiated terpolymerization of butyl acrylate (BA), methyl methacrylate (MMA) and alpha methyl styrene (AMS) has been examined. Kinetic studies focused on elevated reaction temperatures (115 and 140 °C). The studies were made over the full conversion range and examined the effect of reaction temperature, feed composition and initiator level on reaction rates. The composition of terpolymer products and their molecular weights were also analyzed with respect to monomer conversion levels.     

Reaction mechanism of methyl nitrite dissociation during co catalytic coupling to dimethyl oxalate: A density functional theory study

Dissociation of methyl nitrite is the first step during CO catalytic coupling to dimethyl oxalate followed by hydrogenation to ethyl glycol in a typical coal to liquid process. In this work, the first-principle calculations based on density functional theory were performed to explore the reaction mechanism for the non-catalytic dissociation of methyl nitrite in the gas phase and the catalytic dissociation of methyl nitrite on Pd(111) surface since palladium supported on alpha-alumina is the most effective catalyst for the coupling. For the non-catalytic case, the calculated results show that the CH_3O–NO bond will break with a bond energy of 1.91 eV, and the produced CH_3O radicals easily decompose to formaldehyde, while the further dissociation of formaldehyde in the gas phase is difficult due to the strong C–H bond. On the other hand, the catalytic dissociation of methyl nitrite on Pd(111) to the adsorbed CH_3O and NO takes place with a small energy barrier of 0.03 eV. The calculated activation energies along the proposed reaction pathways indicate that(i) at low coverage, a successive dehydrogenation of the adsorbed CH_3O to CO and H is favored while(ii) at high coverage, hydrogenation of CH_3O to methanol and carbonylation of CH_3O to methyl formate are more preferred. On the basis of the proposed reaction mechanism,two meaningful ways are proposed to suppress the dissociation of methyl nitrate during the CO catalytic coupling to dimethyl oxalate.     

Formation of methyl methacrylate from methyl propionate and methanol

The formation of methyl methacrylate (MMA) was studied in a vapor-phase reaction between methyl propionate (MP) and methanol without using any sources of formaldehyde. Silica-supported CsOH doped with a small amount of silver Ag was found to be the best catalyst. The optimum Ag/Cs/Si atomic ratio was 4–10/20–25/1000. When the reaction was performed in the absence of oxygen in the feed, the main product was methyl isobutyrate (MIB) at the beginning of the reaction; MMA was not obtained. As the time-on-stream increased, the formation of MIB fell, while that of MMA increased, showed a maximum, and then decreased gradually. In the case of the reaction performed in the presence of oxygen, the catalytic activity was stable. As the amount of oxygen increased, the yield of MMA increased, while the selectivity fell. The performances were further improved by the combination of a small amount of Ag–Cs/SiO₂ catalyst and a large amount of Cs/SiO₂ catalyst.     

Kinetics of the oxidative dehydrogenation (ODH) of methanol to formaldehyde by supported vanadium-based nanocatalysts

The aim of the present contribution was to develop a detailed kinetic analysis of the oxidative dehydrogenation (ODH) reaction of methanol to formaldehyde on a nano-structured supported vanadium oxide catalyst, selected in a preliminary screening. The chosen vanadium catalyst, supported on TiO₂/SiO₂, has been prepared by grafting vanadyl alkoxide, dissolved in dioxane, and characterized by BET, XRD, Raman, XPS and SEM. An exhaustive set of experimental runs has been conducted in an isothermal packed bed tubular reactor by investigating several operative conditions, such as: temperature, contact time, methanol/oxygen feed molar ratio and water feed concentration. Depending on the operative conditions adopted, the main products observed were formaldehyde and dimethoxymethane while lower amounts of methyl formate and CO₂ were also found. At low contact time, the main reaction product was dimethoxymethane which was then converted into formaldehyde through the reverse equilibrium reaction with water. As a confirmation of this observation, a peculiar behaviour was detected consisting in an increase of selectivity to formaldehyde by increasing methanol conversion. The obtained experimental data of methanol conversion and selectivity towards products were modelled by means of an integral reactor model and the related kinetic parameters were determined by non-linear regression analysis. The adopted reaction rate expressions were of the Mars van Krevelen–Langmuir Hinshelwood type and a good agreement was found between the model theoretical prediction and the experimental data. A reaction mechanism and a detailed reaction scheme (rake-type) were proposed for methanol ODH on a nano-structured catalyst that were able to interpret correctly the collected experimental observations.     

An effective rhodium catalyst system on the synthesis of acetic acid from methyl formate

Rh/Lil/SnR₄ is an effective catalyst system for the conversion of methyl formate to acetic acid under carbon monoxide pressure. The effects of solvent and initial CO partial pressure on the turnover rate of the reaction were investigated. The possibility of replacing some of the iodide promoters by tin compounds has been probed.     

Bromination of methyl esters of soybean fat acids and methyl linoleate with N-bromosuccinimide

1. The reaction of N-bromosuccinimide with methyl esters of soybean fat acids and with methyl linoleate has been investigated, and the influence of changes in the conditions of reaction has been studied.
2. The reaction of brominated methyl esters of soybean fat acids with sodium methoxide produced both methoxylated products and a dimer-like substance.
3. The reaction of brominated methyl esters of soybean fat acids with sodium cyanide and cuprous cyanide did not result in significant replacement of bromine with the cyano group.

     

In situ FTIR studies of methanol adsorption and dehydrogenation over Cu/SiO2 catalyst

In situ FTIR spectroscopy was used to identify the adsorbed species and the intermediates during methanol dehydrogenation over Cu/SiO₂ catalyst, and a schematic reaction network was proposed. Methoxy species on copper, which were derived from adsorbed methanol, dehydrogenated into formaldehyde. Then several competitive pathways took place. The adsorbed formaldehyde could desorb to the gas phase, or react with another adsorbed methoxy group to form methyl formate, and/or undergo further dehydrogenation to CO and H₂. Carbon monoxide formed from the decomposition first adsorbed on high-index planes of copper, and then on low-index planes as the reaction progressed. With the increase of temperature, the concentration of formaldehyde and CO in gas phase increased, and that of methyl formate decreased.     

甲醇氧化酯化反应的Mo－Sb－O催化剂研究

探讨了采用Ｍｏ－Ｓｂ－Ｏ复合氧化物催化剂，由甲醇的氧化酯化反应合成甲酸甲酯。文中考察了反应温度、催化剂晶格、接触时间对甲醇转化率的影响，测试了催化剂性能，扼要探讨了该催化反应的机理。     

An efficient reaction protocol for the ruthenium‐catalysed epoxidation of methyl oleate

The transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide was investigated using Ru(acac)₃/dipicolinic acid as catalyst. Under optimised reaction conditions, the epoxidised methyl oleate 2 was obtained with a quantitative yield in short reaction time and under mild reaction conditions. Practical applications: Epoxidised fatty acids and their derivatives are produced by the Prilezhaev reaction and used in various applications in the chemical industry. Due to the known drawbacks of epoxidation with peroxy acids, such as hazardous handling of peracids in large quantities or the decrease of epoxide selectivity due to the formation of undesired by‐products in the acidic medium, the epoxidation of fatty acid derivatives using more convenient oxidants is still a subject of research interest. Herein, we present a simple procedure for the transition metal catalysed epoxidation of methyl oleate 1 by hydrogen peroxide in quantitative yields, and under mild reaction conditions, as a potential alternative for the production of epoxidised fatty acid derivatives.     

桐酸甲酯酚类加成物的合成及表征

研究了桐酸甲酯和酚类的加成反应，研究表明，桐酸甲酯和酚类加成可得桐酸甲酯酚加成物。对该反应中的催化剂种类和用量、反应时间、反应温度、反应原料选择和配比作了系统的分析，找出了理想的反应条件。ＨＰＬ－ＭＳ分析表明，桐酸甲酯和酚以等摩尔加成物为主要产物，ＩＲ分析表明，桐酸甲酯加成至苯酚的对位。     

Formaldehyde,methanol and methyl formate from formic acid reaction over supported metal catalysts

The catalytic gas-phase decomposition of formic acid was studied over Au/Al₂O₃ and Pt/SBA-15 to investigate the formation of products other than H_2, CO₂, CO and H₂O. Formaldehyde, methanol and methyl formate were detected and identified as secondary products. Two calculation methods for H₂ selectivity (direct and indirect) were compared and assessed in terms of their validity at different temperatures, establishing that a direct quantification of H₂ is necessary for correct results. Based on selectivity trends of all the detected products a reaction scheme is proposed for the decomposition of formic acid and formation of formaldehyde, methanol and methyl formate.     

Analysis of a discontinuously operated chromatographic reactor

The principle of a discontinuously operated chromatographic reactor was studied experimentally and theoretically. The heterogeneously catalysed hydrolysis of methyl formate was chosen as a model reaction. An acidic ion exchange resin was used as catalyst and adsorbent. The relevant adsorption equilibrium constants were available from a previous study. In this work the reaction rates were quantified on the basis of batch reactor experiments. Subsequently, systematic experiments were carried out using a fixed bed. The influence of temperature, residence time, feed concentration and cycle time on the reactor performance was studied. It was attempted to analyse the observations using a simplified pseudo-homogeneous cell model. Since the model was found to be capable of describing the reactor behaviour over a wide parameter range, it was applied to perform extensive parametric calculations. Besides the achievable conversion other objective functions such as recoveries and production rates were also analysed. From the results obtained a few generally applicable rules to evaluate the potential of discontinuously operated chromatographic reactors could be derived.     

乙酰丙酸还原胺化制备5-甲基-2-吡咯烷酮

以甲酸铵为氢源和氮源,N,N-二甲基甲酰胺为溶剂,探讨了甲酸铵直接还原胺化乙酰丙酸制备5-甲基-2-吡咯烷酮的反应途径及机理。通过实验分别考察了反应温度、反应时间、乙酰丙酸与甲酸铵的总质量分数和物质的量比、体系pH值等反应条件对5-甲基-2-吡咯烷酮得率的影响趋势。结果表明,适当提高反应温度、延长反应时间、提高乙酰丙酸与甲酸铵的物质的量比和总质量分数、增加体系pH值均有利于提高5-甲基-2-吡咯烷酮的得率。同时,考察了不同溶剂和乙酰丙酸衍生物在该反应体系中的应用,结果表明极性非质子溶剂甲酰胺、N,N-二甲基乙酰胺、二甲亚砜亦可作为该中体系反应的反应溶剂,乙酰丙酸甲酯、α-当归内酯可作为反应底物在该体系下制备5-甲基-2-吡咯烷酮。     

改性粉煤灰对甲基橙废水的电化学氧化

以酸和碱为改性剂,制备改性粉煤灰。考察了不同反应条件改性粉煤灰作为粒子电极对甲基橙染料废水脱色率的影响。试验结果表明：在室温下反应时间为15min、甲基橙初始浓度为100mg／L、改性剂用量为10g／L、电流密度为95mA／cm^2、0．48gNaCl的最佳条件下,甲基橙的脱色率高达96．21％;在最佳反应条件下电解65min,COD去除率可达76.8％。