乙醇水蒸气重整制氢热力学分析

采用吉布斯自由能最小原理对乙醇水蒸气重整制氢的反应体系进行了热力学分析,考察了温度、压力、水醇比(H_2O/Et OH)和甲醇/乙醇比(MeOH/EtOH)对该体系平衡组成的影响。在压力为1×10~5~80×10~5 Pa,温度为700~1 300 K,水醇比为1∶1~11∶1,甲醇/乙醇比为0∶1~0.9∶1条件下,研究了H_2,CH_4以及C的平衡摩尔数。在选取的条件下,乙醇转化率达到100%。通过分析H_2,CH_4以及C的平衡摩尔数,得出最佳压力为1×105Pa,最佳温度为900 K,最佳水醇比为11∶1,最佳甲醇/乙醇比为0.9∶1。在所研究的条件范围内,通过调整反应条件可以避免积碳的生成。     

水热条件下催化还原CO_2生成甲酸的优化研究

采用金属Al为还原剂,金属Ni和Cu为催化剂,研究了水热条件下CO_2催化转化生成甲酸的特性.针对水热还原CO_2可能存在的4个反应途径进行热力学分析,计算表明,水热条件下反应途径HCO_3~-+2H HCOO~-+H2O在热力学上最易进行,还原氢的最佳存在形态为活性H原子.考察了铝镍和铝铜水热反应体系中Ni/Al摩尔比、Cu/Al摩尔比、Al/C摩尔比、反应时间和温度等对产物甲酸浓度和碳转化率的影响,实验表明,Cu催化剂水热转化CO_2生成甲酸的碳转化率优于Ni催化剂,当Al/Cu/Na HCO_3的3组分摩尔比为8∶8∶1、温度300,℃、反应120,min时,水热还原CO_2生成甲酸的碳转化率为29.1%,.     

运行参数对甲醇重整制氢的热力学特性影响研究

针对以氢气为燃料的动力系统运行条件需求,构建了甲醇重整反应热力学和化学平衡反应体系,以某功率型号燃料电池/燃气轮机(Solid Oxide Fuel Cell/Gas Turbine, SOFC/GT)混合动力系统为研究对象,分析其额定工况、变工况运行时,温度、水碳比和压力对各重整产物分布及产氢率的影响。结果表明:额定运行工况下,重整产物中H_2摩尔分数为49.8%,碳沉积现象消失;在变工况运行时温度对重整反应的热力学特性和化学平衡特性影响较大,当温度为912 K时产氢率达到峰值2.547,当温度为910 K时碳沉积现象消失,当温度高于912 K时不利于H_2的产生;水碳比增加有利于提升产氢率,降低H_2摩尔分数,减少积碳和CO的产生,当水碳比为2时产氢率达到2.48,当水碳比为1.25时碳沉积现象消失;压力对重整结果的影响相对较小,在温度为650～910 K时,降低压力有利于提高产氢率。     

甲酸甲酯和水共存下甲醇分解制燃气的化学平衡

建立了甲酸甲酯和水共存下的甲醇分解制燃气体系的热力学模型,以研究该体系的热力学平衡限度．考察了温度、压力、进料组成对体系的平衡限度影响,探讨了甲醇转化率、氢气和一氧化碳等产物的收率及选择性等．分析发现反应器温度在200℃、压力为0．1MPa时可以获得最佳的原料转化率．研究认为甲醇分解的副产物甲酸甲酯可明显提高氢气和一氧化碳的收率,采用循环工艺分解甲醇可行．进料中的水会导致体系吸热能力降低,且促进二氧化碳生成,应尽量降低进料中水的含量．     

甲醇制取烃类燃料的实验研究

采用固定床反应器对不同温度和压力下甲醇制取烃类燃料进行了研究。催化剂选用沸石分子筛HZSM-5,Si/Al比为25;反应原料为甲醇水溶液(83%)。在体积空速为8h-1的条件下,研究了300、350、400、450℃及常压、1、1.5、2、2.5 MPa压力下甲醇的转化率、油相得率和气体得率。研究结果显示,反应的最佳温度为400℃、压力为2 MPa,在此条件下,甲醇转化率接近100%,油相得率最高。     

生物质气一步法合成二甲醚化学平衡分析

对生物质基合成气合成二甲醚反应体系进行热力学参数计算.选取CO、CO2加氢合成甲醇及甲醇脱水生成二甲醚为独立反应,CO、CO2、二甲醚为关键组分,提出了合成气合成二甲醚的计算模型.讨论了温度、压力对生物质气合成二甲醚化学平衡的影响.结果表明:CO平衡转化率、DME平衡收率随温度的升高而下降;随压力升高,CO平衡转化率、DME平衡收率增加.     

橡胶籽油制备生物柴油的工艺研究

实验研究了乙醇钠催化下橡胶籽油与乙醇进行酯交换反应制备生物柴油的工艺条件。通过正交实验和单因素实验,发现酯交换反应的最佳工艺条件:催化剂用量为油重的1.0%,醇油物质的量比为15∶1,反应温度为78℃,搅拌时间为120 min,在此反应条件下,橡胶籽油转化率为92.14%。     

整体式催化剂上甘油水蒸气重整制氢

为改善甘油重整制氢反应在转化率、氢产率以及抑制积碳方面都与热力学平衡存在较大差距的问题,设计开发了整体式重整催化剂.考察了涂层组分、比例对整体式催化剂理化特性及其在甘油水蒸气重整制氢反应中催化性能的影响.通过考察Ce-Zr物质的量比及La的添加对催化剂活性的影响,确定了Ce-Zr-La物质的量比为1∶1∶1为最优条件.整体式催化剂的活性得到明显改善,在甘油质量分数为10%,空速为3.07,h-1时,在温度考察范围内甘油完全转化为气相产物,氢气选择性递增,并趋于平稳,最高可达90.85%;随着空速增大,甘油质量分数的增加,氢气选择性减小,甘油气相转化率降低,但仍可保持较好的转化效果.     

对甲苯磺酸催化麻疯树油甲酯化的实验研究

实验研究了麻疯树油在对甲苯磺酸催化剂的作用下与甲醇发生转酯化反应生成脂肪酸甲酯(生物柴油)的情况.实验结果表明,该转酯化反应的最佳操作条件为催化剂用量为麻疯树油量的5% 、油醇摩尔比为1∶ 3、反应时间为30 min、反应温度为70℃.     

CuO-ZnO-Al_2O_3/蒙脱土催化二氧化碳加氢合成二甲醚

采用盐酸酸化的蒙脱土负载共沉淀法制备的CuO-ZnO-Al2O3,制备了CuO-ZnO-Al2O3/蒙脱土催化剂,用BET、FT-IR和XRD对催化剂结构进行了表征,并在固定床微型反应器中研究了其对二氧化碳加氢制备二甲醚的催化活性,在反应混合气空速为1 600 h-1,蒙脱土∶CuO-ZnO-Al2O3=3∶7(质量比)的条件下,测定了酸化浓度、反应温度、压力和H2/CO2体积比对催化活性的影响。结果表明,用1 mol/L HCl酸化蒙脱土,反应温度为545K,反应压力为3 MPa,H2/CO2体积比为3时,CO2的单程转化率达到26.5%,二甲醚的选择性和收率分别为16.7%和4.4%,甲醇和二甲醚的总收率达到15.7%。     

Thermodynamic analysis of high‐temperature helium heated fuel reforming for hydrogen production

In order to take full advantage of the heat from high temperature gas cooled reactor, thermodynamic analysis of high‐temperature helium heated methane, ethanol and methanol steam reforming for hydrogen production based on the Gibbs principle of minimum free energy has been carried out using the software of Aspen Plus. Effects of the reaction temperature, pressure and water/carbon molar ratio on the process are evaluated. Results show that the effect of the pressure on methane reforming is small when the reaction temperature is over 900 °C. Methane/CO conversion and hydrogen production rate increase with the water/carbon molar ratio. However the thermal efficiency increases first to the maximum value of 61% and then decreases gradually. As to ethanol and methanol steam reforming, thermal efficiency is higher at lower reaction pressures. With an increase in water–carbon molar ratio, hydrogen production rate increases, but thermal efficiency decreases. Both of them increase with the reaction temperature first to the highest values and then decrease slowly. At optimum operation conditions, the conversion of both ethanol and methanol approaches 100%. For the ethanol and methanol reforming, their highest hydrogen production rate reaches, respectively, 88.69% and 99.39%, and their highest thermal efficiency approaches, respectively, 58.58% and 89.17%. With the gradient utilization of the high temperature helium heat, the overall heat efficiency of the system can reach 70.85% which is the highest in all existing system designs. Copyright © 2014 John Wiley & Sons, Ltd.     

生物油-甲醇催化重整制氢的氢产率及碳转化率的研究

采用生物油-甲醇催化重整制氢。在微型固定反应装置上通过正交法试验设计,对生物油甲醇混合比例、反应温度、水碳比、进样流速等因素进行了系统的试验。在选择的最佳反应条件下,氢气产率和碳转化率分别为34.89%及63.34%。     

The role of surface reactions on the active and selective catalyst design for bioethanol steam reforming

In order to study the role of surface reactions involved in bioethanol steam reforming mechanism, a very active and selective catalyst for hydrogen production was analysed. The highest activity was obtained at 700 °C, temperature at which the catalyst achieved an ethanol conversion of 100% and a selectivity to hydrogen close to 70%. It also exhibited a very high hydrogen production efficiency, higher than 4.5 mol H₂ per mol of EtOH fed. The catalyst was operated at a steam to carbon ratio (S/C) of 4.8, at 700 °C and atmospheric pressure. No by-products, such as ethylene or acetaldehyde were observed. In order to consider a further application in an ethanol processor, a long-term stability test was performed under the conditions previously reported. After 750 h, the catalyst still exhibited a high stability and selectivity to hydrogen production. Based on the intermediate products detected by temperature programmed desorption and reaction (TPD and TPR) experiments, a reaction pathway was proposed. Firstly, the adsorbed ethanol is dehydrogenated to acetaldehyde producing hydrogen. Secondly, the adsorbed acetaldehyde is transformed into acetone via acetic acid formation. Finally, acetone is reformed to produce hydrogen and carbon dioxide, which were the final reaction products. The promotion of such reaction sequence is the key to develop an active, selective and stable catalyst, which is the technical barrier for hydrogen production by ethanol reforming.     

Transesterification of rapeseed and palm oils in supercritical methanol and ethanol

The results of the rapeseed and palm oils transesterification with supercritical methanol and ethanol were presented. The studies were performed using the experimental setups which are working in batch and continuous regimes. The effect of reaction conditions (temperature, pressure, oil to alcohol ratio, reaction time) on the biodiesel production (conversion yield) was studied. Also the effect of preliminary ultrasonic treatment (ultrasonic irradiation, emulsification of immiscible oil and alcohol mixture) of the initial reagents (emulsion preparation) on the stage before transesterification reaction conduction on the conversion yield was studied. We found that the preliminary ultrasonic treatment of the initial reagents increases considerably the conversion yield. Optimal technological conditions were determined to be as follows: pressure within 20-30 MPa, temperature within 573-623 K. The optimal values of the oil to alcohol ratio strongly depend on preliminary treatment of the reaction mixture. The study showed that the conversion yield at the same temperature with 96 wt.% of ethanol is higher than with 100 wt.% of methanol.     

Low-temperature alcohol-assisted methanol synthesis from CO2 and H2: The effect of alcohol type

Carbon dioxide (CO₂) conversion to higher-value products is a promising pathway to mitigate CO₂ emissions. Methanol is a high-value-chain chemical in industries that can be produced through CO₂ hydrogenation, which is an exothermic reaction. Due to thermodynamic limitations, a typical synthesis temperature between 250 °C and 300 °C results in a low conversion of CO₂ at equilibrium. To enhance the CO₂ conversion, high pressures of 50–100 bar are required, which inevitably causes the process to be energy-intensive. In this study, an alternative method called alcohol-assisted methanol synthesis is investigated. In this method, alcohol is used as a catalytic solvent and helps decrease the reaction temperature and pressure (150 °C and 50 bar) and significantly increases methanol yield. Ethanol is used as the alcohol due to its reactivity, providing a high methanol yield (47.80%) with 63.93% CO₂ conversion and 67.54% methanol selectivity. However, due to unwanted side reactions, ethanol generates ethyl acetate as a byproduct that forms an azeotrope with methanol, leading to difficulty in product purification. The effects of alcohol type (molecular weight and structure), including ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, tert-butanol and 1-pentanol, on CO₂ conversion, methanol yield and byproducts are investigated. It is found that smaller-molecule alcohols provide a higher methanol yield. Moreover, n-alcohols provide a higher methanol yield than branched alcohols, and the byproducts of the reaction with n-alcohols do not form an azeotrope with methanol. Therefore, 1-propanol is compared with ethanol providing 26.55% methanol yield, 69.02% CO₂ conversion and 70.82% methanol selectivity.     

Bimetallic catalysts performance during ethanol steam reforming: Influence of support materials

Ni–Cu catalysts supported on different materials were tested in ethanol steam reforming reaction for hydrogen production. These catalysts were evaluated at reaction temperature of 400 °C under atmospheric pressure. The reagents, with a water/ethanol molar ratio equal to 10, were fed at 70 dm³/(h g_cat) (after vaporization). Analysis of the ethanol conversion, as well as evaluation and quantification of the reaction products, indicated the catalyst 10% Ni–1% Cu/Ce_0.6Zr_0.4O₂ as the most appropriate for the ethanol steam reforming under investigated reaction conditions, among the studied catalysts. During 8 h of reaction this catalyst presented an average ethanol conversion of 43%, producing a high amount of H₂ by steam reforming and by ethanol decomposition and dehydrogenation parallel reactions. Steam reforming, among the observed reactions, was quantified by the presence of carbon dioxide. About 60% of the hydrogen was produced from ethanol steam reforming and 40% from parallel reactions.     

Pt/C催化剂催化微晶纤维素加氢的研究

通过对Pt/C催化剂催化转化微晶纤维素的研究,探讨了纤维素催化转化的反应机理及反应温度、H2压力、反应时间对纤维素转化率和乙二醇选择性的影响,同时考察了超声波预处理微晶纤维素,讨论了超声时间对微晶纤维素催化加氢转化率的影响。试验结果表明,随着反应温度、H2压力的增大和反应时间的延长,纤维素转化率逐渐增加,在250℃,H2压力为4 MPa,反应2 h时,微晶纤维素的转化率可达到80.08%,乙二醇的选择性为70.02%。随着超声时间的延长,微晶纤维素的转化率逐渐增大,超声20 min后变化不明显。     

Characteristics of hydrogen production by a plasma–catalyst hybrid converter with energy saving schemes under atmospheric pressure

This paper investigated the production of hydrogen from methane under atmospheric pressure using a plasma–catalyst hybrid converter with emphasis on energy conservation. A spark discharge was used to ionize the hydrocarbon fuel and air mixture with a catalyst to enhance hydrogen production using two energy saving schemes, namely, heat recycling and heat insulation. The experimental results showed that higher methane feeding rate resulted in higher reformate gas temperature and a corresponding increase in methane conversion efficiency. The energy saving systems also enabled the oxygen/carbon ratio to be decreased to reduce oxidation of hydrogen and carbon monoxide and thereby improving the concentrations of hydrogen and carbon monoxide. By heat recycling, a lower methane feeding rate showed an 8.7% improvement in methane conversion efficiency whilst improvement was not apparent with higher methane supply rates due to the already high conversion efficiency. Moreover, it was shown that hydrogen production increased significantly with the reaction from water–gas shifting under the same operation parameters but with high methane selectivity. The best combination resulting in a total thermal efficiency of 77.11% was 10 L/min methane feeding rate and 0.8 O₂/C ratio. With water–gas shifting (S/C ratio=0.5), an 86.26% hydrogen yield, equating to 17.25 L/min hydrogen production rate could be achieved. The equilibrium production rate was calculated using the commercialized HSC Chemistry software (^©ChemSW Software, Inc.). Good correlation was obtained between the calculations and the experimental results.     

高酸值生物柴油原料的预酯化反应装置的实验研究

以固体酸为催化剂,对高酸值废弃油脂进行预酯化反应研究。讨论了不同降低水分含量的方法对反应的影响,并考察了反应条件(醇油摩尔比、反应时间)对预酯化效果的影响。实验结果表明:在反应体系中添加吸水剂分子筛可提高预酯化反应效率;反应体系中添加过量的甲醇能大大缩短反应时间,在反应温度75℃,催化剂加入量为10%(W/W),最佳醇油摩尔比8∶1,最佳反应时间4h的条件下,可将酸化油的酸值降至3.8mgKOH.g-1,满足酯交换反应酸值小于4.0mgKOH.g-1要求。     

Catalytic combustion of alcohols for microburner applications

The combustion of energy dense liquid fuels in a catalytic micro-combustor, whose temperatures can be used in energy conversion devices, is an attractive alternative to cumbersome batteries. To miniaturize the reactor, an evaporation model was developed to calculate the minimum distance required for complete droplet vaporization. By increasing the ambient temperature from 298 to 350 K, the distance required for complete evaporation of a 6.5 μm droplet decreases from 3.5 to 0.15 cm. A platinum mesh acted as a preliminary measurement and demonstrated 75% conversion of ethanol. We then selected a more active rhodium-coated alumina foam with a larger surface area and attained 100% conversion of ethanol and 95% conversion of 1-butanol under fuel lean conditions. Effluent post-combustion gas analysis showed that varying the equivalence ratio results in three possible modes of operation. A regime of high carbon selectivity for CO₂ occurs at low equivalence ratios and corresponds to complete combustion with a typical temperature of 775 K that is ideal for PbTe thermoelectric energy conversion devices. Conversely for equivalence ratios greater than 1, carbon selectivity for CO₂ decreases as hydrogen, olefin and paraffin production increases. By tuning the equivalence ratio, we have shown that a single device can combust completely for thermoelectric applications, operate as a fuel reformer to produce hydrogen gas for fuel cells or perform as a bio-refinery for paraffin and olefin synthesis.