乙醇催化脱氢合成乙醛的工艺研究

采用共沉淀法制备系列CuZnAl催化剂,在固定床反应器考查了催化剂对乙醇脱氢制备乙醛并副产氢气的催化性能。研究了CuZnAl组分比例对催化剂活性的影响,并对工艺条件进行优化。结果表明:Cu∶Zn∶Al=4∶4∶2时,乙醇脱氢反应催化活性达到最高;在温度为280℃,压力为1MPa,床层空速为0.8h-1,n(乙醇)∶n(水)=2,乙醇转化率达53.6%,乙醛选择性达92.2%,副产氢气纯度高达97.5%。200h连续实验,CuZnAl催化剂催化乙醇脱氢反应转化率稳定在50%以上。     

乙酸异丙酯加氢催化剂的制备与性能研究

乙酸异丙酯通过催化加氢可以制备具有高附加值的异丙醇和乙醇。利用共沉淀法制备了一系列铜基催化剂,以锌为助剂,分别研究了催化剂制备方法、活性组分质量分数、反应条件对乙酸异丙酯加氢反应的影响。结果表明,将所制备的催化剂用于乙酸异丙酯加氢反应中,在反应温度为230℃、反应压力为7.0 MPa、液体空速为0.2 h~(-1)的反应条件下,乙酸异丙酯转化率可以达到98%以上,异丙醇和乙醇总产率达93%以上。     

活性炭负载乙酸钾催化邻苯二酚和乙醇合成邻羟基苯乙醚

以活性碳为载体,以乙酸钾为活性组分的固体碱催化剂对邻苯二酚与乙醇气固相催化合成邻羟基苯乙醚的过程,考察了乙酸钾负载量对催化剂活性的影响以及反应条件对该反应的影响。结果表明随乙酸钾负载量的增加催化剂的碱性先增加后减小,乙酸钾负载量为15%质量分数的催化剂对该反应有最好的催化性能,当反应温度为433 K,邻苯二酚和乙醇摩尔比为10时,反应时间为150 min较适宜。在此条件下,邻苯二酚的转化率和邻羟基苯乙醚的选择性分别为99%和97%。     

RuCl3一步催化氧化液相乙醇合成1,1-二乙氧基乙烷

首先考察了不同金属卤化物对乙醇一步液相氧化合成1,1-二乙氧基乙烷(DEE)的催化性能。结果表明,RuCl_3催化性能最好。然后考察了反应条件的影响,结果表明,以50 mL无水乙醇(0.86 mol)为反应物时,最佳催化反应条件为:反应温度120℃、氧气压力2MPa、反应时间3h、催化剂用量0.004%(以乙醇的物质的量为基准,下同)、搅拌速度600 r/min,此时乙醇转化率达到38.2%,DEE选择性达到78.9%。并且发现,Ru~(3+)不但对乙醇氧化成乙醛具有较高的催化活性,同时RuCl_3是一种温和的路易斯酸,可以较好地催化乙醇与乙醛的缩合反应。最后对RuCl_3催化剂的重复使用性进行了考察,催化剂重复使用20次后,依然有较高的催化活性。     

由复合硫酸盐催化剂催化合成乙酸乙酯

在硫酸盐复合催化剂的条件下,由乙酸和乙醇为原料合成了高收率乙酸乙酯。该文研究了硫酸盐复合催化剂使用量、乙醇使用量和反应的时间,带水剂的选择等因素对催化合成乙酸乙酯收率的影响。实验结果表明当乙醇:乙酸摩尔比为1.6:1和复合硫酸盐n(Fe2(SO4)3)∶n(K2SO4)为4.2:1、带水剂14m L时,回流反应分水110min,酯收率为87.57%,为最佳条件。     

改性树脂催化剂催化浆态鼓泡床合成乙酸正丁酯

以改性D001型阳离子交换树脂为催化剂,以乙酸和正丁醇为原料,在浆态鼓泡床多相反应器反应回流条件下催化酯化反应制备乙酸正丁酯,研究了反应器的技术优势及催化剂的特性和催化剂类型、用量对酯化反应的影响及其使用寿命. 结果表明,最佳反应条件为：正丁醇:乙酸=1.2:1(摩尔比),催化剂用量占乙酸量的40%(w),反应温度110℃,反应时间75 min,该条件下乙酸正丁酯产率达98%以上,纯度达99.5%,催化剂经洗涤活化、再生,可重复使用6次.     

磷钼酸催化合成乙酸乙酯的动力学研究

在反应精馏过程所涉及的温度范围内对磷钼酸催化合成乙酸乙酯的化学反应动力学进行了实验研究,测定了两个温度(110℃,120℃)和四个磷钼酸浓度(0.20%,0.40%,0.60%,0.80%)下的反应速率数据,获得了该温度和催化剂浓度范围内的反应动力学表达式和反应速率常数.实验结果表明,实验条件下的反应速率对乙醇和乙酸均为一级反应.反应速率常数随磷钼酸浓度呈线性增长.     

硅胶固载氧化镓非均相催化合成乙酸丁酯

在氧化镓固载量为20%,500℃焙烧2 h的条件下制备了硅胶固载氧化物型非均相酯化催化剂Ga2O3/S iO2,用于催化合成乙酸丁酯,考察了催化剂用量、n(正丁醇)∶n(乙酸)、环己烷用量、反应时间、带水剂用量和催化剂重复使用性等因素对酯化率的影响。结果表明,该催化剂催化合成乙酸丁酯的适宜反应条件为:乙酸0.2 mol,n(正丁醇)∶n(乙酸)=1.8,催化剂1.25 g,回流反应1 h,酯化率达99.62%。     

乙醇催化氧化、缩合和酯化反应的研究进展

乙醇是一种重要的基础化工产品,随着生物乙醇和煤制乙醇的大规模发展,乙醇的过剩问题越来越严重,因此,将乙醇催化转化为高附加值化学品具有重要意义。乙醇经催化氧化制乙醛、乙酸,经催化脱氢-缩合制乙缩醛,经催化脱氢-酯化制乙酸乙酯等催化反应过程,不仅可以消化日益增多的乙醇产能,提高乙醇附加值,而且有效地延伸了乙醇产业链,并带来巨大的社会效益和经济效益。对近年来乙醇经催化氧化制乙醛、乙酸,经催化加氢-缩合制乙缩醛,经催化脱氢-酯化制乙酸乙酯等催化反应的催化剂体系、反应工艺和反应机理等方面的研究进展进行归纳、总结和评述,并对研究工作的发展趋势进行展望。     

La-HZSM-5催化乙醇脱水制乙烯

以HZSM-5分子筛改性得到的3%LA-HZSM-5分子筛为催化剂,在小型的固定床反应器中(φ45 mm×600 mm)考察了乙醇浓度、反应温度和液时空速对乙醇脱水制乙烯反应的影响.采用X射线衍射(XRD)、NH3程序升温脱附(NH3-TPD)、N2吸附-脱附和热重-差示扫描量热仪(TG-DSC)等手段对3%La-HZSM-5分子筛反应前后催化剂的物性变化进行分析,并考察了催化剂的稳定性.结果表明,该催化剂对乙醇脱水反应具有良好的催化性能,较好的再生性能、强度和稳定性.乙醇脱水反应的合适反应条件为催化剂180 g,乙醇质量浓度50%,液时空速1.1 h-1,反应温度260℃.在此条件下,乙醇转化率和乙烯选择性均高于98%,催化剂单程使用寿命达900 h.     

Gold Nano-size Effect in Au/SiO2 for Selective Ethanol Oxidation in Aqueous Solution

Narrowly sized colloidal Au particles of varying average sizes (3–30 nm) were immobilized on an inert support (SiO₂) to study the Au size effect on the aerobic oxidation of ethanol in aqueous solution. Au particles with an average diameter of 5 nm showed an areal activity that was about three times that of the smaller (3 nm), and 15 times that of larger (10–30 nm) Au particles. Investigation on the dependence of product yields on ethanol conversion over these differently sized Au particles clearly uncovered that the yield of acetic acid increased always with the ethanol conversion, while that of acetaldehyde passed a maximum at an ethanol conversion of 20–30%, therefore well demonstrating that acetaldehyde is the intermediate product in the oxidation of ethanol to acetic acid.     

The Mechanism Studies of Ethanol Oxidation on PdO Catalysts by TPSR Techniques

The paper studies the direct oxidation of ethanol and CO on PdO/Ce_0.75Zr_0.25O₂ and Ce_0.75Zr_0.25O₂ catalysts. Characterization of catalysts is carried out by temperature-programmed desorption (TPD), temperature-programmed surface reaction (TPSR) techniques to correlate with catalytic properties and the effect of supports on PdO. The simple Ce_0.75Zr_0.25O₂ is in less active for ethanol and CO oxidation. After loaded with PdO, the catalytic activity enhances effectively. Combined the ethanol and CO oxidation activity with CO-TPD and ethanol-TPSR profiles, we can find the more intensive of CO₂ desorption peaks, the higher it is for the oxidation of CO and ethanol. Conversion versus yield plot shows the acetaldehyde is the primary product, the secondary products are acetic acid, ethyl acetate and ethylene, and the final product is CO₂. A simplified reaction scheme (not surface mechanism) is suggested that ethanol is first oxidized to form intermediate of acetaldehyde, then acetic acid, ethyl acetate and ethylene formed going with the formation of acetaldehyde, acetic acid, ethyl acetate; finally these byproducts are further oxidized to produce CO₂. PdO/Ce_0.75Zr_0.25O₂ catalyst has much higher catalytic activity not only for the oxidation of ethanol but also for CO oxidation. Thus the CO poison effect on PdO/Ce_0.75Zr_0.25O₂ catalysts can be decreased and they have the feasibility for application in direct alcohol fuel cell (DAFC) with high efficiency.     

The Oxidative Fermentation of Ethanol in Gluconacetobacter diazotrophicus Is a Two-Step Pathway Catalyzed by a Single Enzyme: Alcohol-Aldehyde Dehydrogenase (ADHa)

Gluconacetobacter diazotrophicus is a N₂-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH) and the aldehyde dehydrogenase (ALDH). We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa) of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2–C6) and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.     

Synthesis of Dimethyl Carbonate from Methanol and Carbon dioxide using Potassium Methoxide as Catalyst under Mild Conditions

Pd-supported on WO₃–ZrO₂ (W/Zr atomic ratio=0.2) calcined at 1073 K was found to be highly active and selective for gas-phase oxidation of ethylene to acetic acid in the presence of water at 423 K and 0.6 MPa. Contact time dependence demonstrated that acetic acid is formed via acetaldehyde formed by a Wacker-type reaction, not through ethanol by hydration of ethylene.     

The role of water in ethanol oxidation over SnO2-supported molybdenum oxides

The role of water in the oxidation of ethanol to acetic acid on Sn–Mo–O catalysts was studied by catalytic test and FTIR spectroscopy of adsorbed species. The reaction showed a typical behavior of series reactions involving oxidation of ethanol to acetaldehyde and of the latter to acetic acid and CO₂. Addition of water to the feed gas decreased the oxidation rate and significantly increased the selectivity to acetic acid, strongly contributing to decreasing the number of secondary products. FTIR analyses showed that water promotes desorption of ethanol and carboxylates, present as bridging and monodentate species. Decreasing catalytic rate values and increasing selectivity to acetic acid in the presence of water follow from site blocking by hydroxyl groups. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aqueous-Phase Processing of Bio-oil Model Compounds Over Pt–Re Supported on Carbon

The aqueous-phase processing (APP) of biomass-derived bio-oil model compounds such as ethanol, acetaldehyde, formic acid and acetic acid over Pt?CRe/C was examined. For the APP of ethanol at 250?°C, the product distribution was determined and quantified. H₂, CO₂, CH₄, C₂H₆, acetaldehyde, ethyl ether, ethyl acetate, acetic acid were found to be primary products and C₃H₈, methanol, butanol and acetal were found to be minor products. By also exploring the product distributions of acetaldehyde, acetic acid and formic acid under APP conditions with the Pt?CRe/C, the reaction network associated with the APP conversion of ethanol was determined. Using this reaction network, flux analysis was performed on the ethanol reaction system to determine the reaction pathway and relative rates (v₁?Cv₈) for each step. From this analysis, it was found that the dehydrogenation of the ethanol was the most active reaction in the reaction system.     

Electrooxidation of ethanol on a Pt electrode in acid solutions: in situ ATR-SEIRAS study

The electrooxidation of ethanol was investigated on a Pt thin film electrode in a HClO₄ solution using surface enhanced infrared absorption spectroscopy (SEIRAS) with the attenuated total reflection (ATR) technique. The spectra indicate that during this reaction acetate and CO adsorbates are formed. The intensity of symmetric OCO stretching band of adsorbed acetate correlates well with voltammetry in the potential range between −0.1 and 0.85 V. The CO stretching band for adsorbed acetaldehyde and/or acetyl also was observed; these compounds are the reaction intermediates whose oxidation generates CO_ad and acetic acid. We also explored the oxidation behavior of adsorbed residues. The oxidation of acetaldehyde was studied for comparison.     

醋酸生产的仿真研究(Ⅱ)氧化塔的仿真

在MATLAB下的SIMULINK环境中对醋酸氧化塔进行动态仿真。首先分析乙醛氧化制醋酸的实际生产过程，然后通过对乙醛反应进行简化处理，建立醋酸氧化塔的数学模型，并把建立的数学模型转变成相应的SIMULINK方框图和S－函数。最后将氧化塔模型与前文的原料系统模型连接，在计算机上进行动态仿真，给出仿真结果，并就此进行说明分析。     

In situ FTIR studies of the catalytic oxidation of ethanol on Pt(1 1 1) modified by bi-dimensional osmium nanoislands

This paper presents the study of ethanol electrooxidation on Pt(1 1 1) electrode modified by different coverage degrees of a submonolayer of osmium nanoislands, which were obtained by spontaneous deposition. The ethanol oxidation reaction was extensively studied by employing in situ FTIR. Collections of spectra of the ethanol adsorption and oxidation processes were acquired over a series of positive potential steps, in order to determine the intermediate species and the main products that are formed. It was shown that the increase in the catalytic activity of Pt(1 1 1) after osmium deposition for ethanol oxidation is greater than that observed on nonmodified Pt(1 1 1). It was also demonstrated that the mechanistic pathway for this reaction depends directly on the degree of osmium coverage. Thus, for low osmium coverage (θ_Os ≤ 0.28), the formation of CO as an intermediate is favored, and hence the full oxidation of adsorbed ethanol to CO₂ is increased, additionally, the formation of acetaldehyde is also observed in low degrees of osmium coverage. For intermediate osmium coverage (0.28 < θ_Os ≤ 0.40), the oxidation of ethanol to acetaldehyde and then to acetic acid is favored, although on Pt(1 1 1) the formation of acetaldehyde is promoted. For higher degrees of osmium coverage (θ_Os > 0.51), the catalytic activity of the electrode for ethanol oxidation decreases. For an almost complete osmium layer (θ_Os = 0.92), obtained by electrodeposition at 50 mV, catalytic activity for ethanol oxidation shows the lowest value. In addition, the direct oxidation of ethanol to acetic acid at lower potentials is observed.