固相法合成铜铝尖晶石催化甲醇重整反应

以氢氧化铜和拟薄水铝石为原料(Cu/Al物质的量比为1/2),采用固相法经过不同温度焙烧后获得了一系列Cu-Al氧化物催化剂.当焙烧温度由500 ℃提高到900 ℃时,催化剂的主要铜物种由CuO渐变为CuAl₂O₄,比表面积由75.0 m²/g降低至16.6 m²/g.在甲醇重整反应过程中,以CuAl₂O₄为主要成分且具有较高比表面积的催化剂表现了优异的催化性能.另外,以CuAl₂O₄为主要成分的催化剂不经过预还原处理时,在反应过程中同时存在活性铜的释放和烧结,其催化活性呈现先增加后降低的趋势.在本研究催化剂制备条件下,优选800 ℃焙烧的催化剂,其催化性能优于商业Cu-Zn-Al催化剂,且具有可再生性.当催化剂不经过预还原处理时,在水醇物质的量比为1、240 ℃、1.01×10⁶ Pa、质量空速为1.75 h^-1的条件下,甲醇起始转化率为55.2%;反应进行288.3 h时,甲醇转化率升高至79.3%;反应继续运行至1 000.5 h时,甲醇转化率降低至63.9%.     

Hydrogen and syngas production from two-step steam reforming of methane using CeO2 as oxygen carrier

CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane (SRM). Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor. Methane is directly converted to syngas at a H2/CO ratio close to 2 : 1 at a high temperature (above 750 °C) by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 °C in methane isothermal reaction. CeO2?δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 °C; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction (C+2H2O→CO2+2H2). Slight deactivation in terms of amounts of desired products (syngas and hydrogen) is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.     

CuZnAlZr催化剂上甲醇氧化水蒸气重整制氢Ⅰ.催化剂组成的优化

 采用共沉淀法制备了不同配比的CuZnAlZr复合氧化物催化剂,并通过XRD和TPR等表征技术及活性评价,考察了催化剂各组分配比对活性的影响,从而对各组分配比进行了优化. 结果表明,组成为(Cu7Zn3)7(Al6Zr4)3的催化剂具有最高的催化活性,反应温度为200 ℃时,甲醇转化率可高达91%,而重整气体中CO的体积分数仅为0.12%. 具有较高分散性及高还原性能的表相Cu组分的增加有利于提高催化剂的活性,Zn可以起到隔离和分散Cu的作用,而Al和Zr的存在可以稳定表相Cu2+的存在形式.     

内燃机及其热电联产系统的典型变工况解析特性

通过大量实测数据总结出发电内燃机的典型变工况特性曲线,并给出相应的公式.结合饱和蒸汽余热锅炉的变工况特性解析解,对内燃机热电联产系统的变工况特性进行了分析:逼近温差ΔTa和相对蒸汽产量随负荷降低而减小,总能利用率、当量(火用)效率和经济(火用)效率随负荷减小先增后减,存在一个最佳值,该值对应内燃机最佳工作状态.余热锅炉蒸汽参数越高,变工况时ΔTa越低.与单轴燃气轮机热电联供装置相比,内燃机联产系统的ΔTa在低工况下更易变为负值,原因为前者在降负荷时烟气流量略增加,而后者降低.ΔTa变负会对余热锅炉有重要影响,内燃机进行热电联产时要注意其安全运转问题.     

Steam chromatography of aliphatic and aromatic amines on packed columns with aqueous potassium hydroxide as the stationary liquid phase

Aqueous alkali was proposed as the stationary liquid phase (SLP) for separation of amines by steam chromatography. Characteristic features of retention of amines of various structures were studied. The retention of primary and secondary amines on aqueous potassium hydroxide as the SLP differs fundamentally from that observed with common organic SLP. Primary amines are eluted in the following order,n-pentylamine <n-butyl-amine <n-propylamine <n-hexylamine <n-octylamine for secondary amines, the following sequence was established; diethylamine < dibutylamine < dimethylamine. Higher-boiling tertiary amines containing ethyl andn-butyl radicals are eluted ahead of diamines containing the same radicals. Translated fromIzvestiya Akademii Nau. Seriya Khimicheskaya, No. 8 pp. 1507–1509, August, 1999.     

甲醇水蒸气重整制氢Pd/ZnO催化剂的研究

采用并流共沉淀法制备Pd／ZnO甲醇水蒸气重整制氢催化剂,考察了Pd的质量分数和还原温度对催化剂性能的影响。结果表明,当Pd质量分数为15．9％,还原温度为573K时,催化剂有较好的甲醇转化率及二氧化碳选择性。TPR结果表明,PdO在室温下被还原为金属Pd,在440K开始有部分ZnO被还原。XRD分析结果表明,PdZn合金是甲醇水蒸气重整反应的活性中心;在21．9％Pd／ZnO催化剂上出现了Pd2Zn合金相,导致催化剂的活性下降;反应过程中还原催化剂形成PdZn合金,其活性不如相同条件下纯氢还原的。15．9％Pd／ZnO催化剂及工业铜基催化剂的初始稳定性结果显示,在8h内,15．9％Pd／ZnO催化剂上甲醇转化率保持在66％以上,而铜基催化剂的活性下降了14．4％。     

Novel Integrated Flow-Based Steam Distillation and Titration System for Determination of Volatile Acidity in Wines

Novel integrated flow-based steam distillation and titration system with spectrophotometric detection was developed for determination of volatile acidity in wines. Using the system, the distillation procedure was carried out in an automatic manner, starting with introducing into a heated steam distillation module a sample and subjecting it to steam distillation. Under selected conditions, all the analyte was transferred to the distillate; therefore, the system did not require calibration. The collected distillate and titrant were introduced into the next monosegments in varying proportions, in accordance with the developed titration procedure, and directed to the detection system to record the titration curve. The titration was stopped after reaching the end point of titration. Procedures for distillation and titration were developed and verified separately by distillation of acetic acid, acetic acid in the presence of tartaric acid as well as acetic acid, tartaric acid, and titratable acidity, with precision (relative standard deviation) and accuracy (relative error) for both procedures lower than 6.9 and 5.6%, respectively. The developed steam distillation and titration systems were used to determine volatile acidity in samples of white and rosé wines separately and as the integrated steam distillation and titration system, both with precision lower than 9.4% and accuracy better than 6.7%.     

聚合物阵列波导光栅的制作技术

研究了聚合物阵列波导光栅AWG制作的几个关键技术.首先,为了克服反应离子刻蚀过程中单独使用光刻胶作掩膜而导致的光波导形状和尺寸偏离设计的缺点,采用了光刻胶与金属掩膜相结合的双掩膜技术进行器件制作.详细介绍了双掩膜技术制备聚合物AWG的过程,并得出铝膜作为掩膜的最佳厚度为100nm左右.测试给出了使用和没有使用双掩膜的对比结果,该结果表明使用双掩膜技术制作的波导质量明显好于单独使用光刻胶作掩膜制作的结果.其次,采用蒸气回溶技术来减小反应离子刻蚀产生的波导表面和侧壁的起伏,从而降低了波导的散射损耗.结果表明,蒸气回溶技术使所制作的波导表面的均方根粗糙度从41.307nm降低到24.564nm.     

自发凝结流动数值模拟方法及其在Laval喷管中的应用

本文对存在自发凝结的湿蒸汽两相流动建立了完全欧拉坐标系统下的数理模型。采用考虑了真实流体性质的 LU-SGS-GE隐式时间推进算法和改良型高精度、高分辨率MuSCL TVD差分格式求解存在自发凝结的汽液两相流动控制方程组。文中水及水蒸汽性质数据全部取自IAPWS-IF97国际标准公式。对某Laval缩放喷管内的湿蒸汽自发凝结流动的数值模拟结果表明,本文所采用的数理模型及计算方法是有效和可靠的。