Studies of the Methane Steam Reforming Reaction at High Pressure in a Ceramic Membrane Reactor

The effects of temperature and pressure on the steam reforming of methane 3H2+CO) were investigated in a membrane reactor (MR) with a hydrogen permeable membrane. The studies used a novel silica-based membrane prepared by using the chemical vapor deposition (CVD) technique with a permeance for H2 of 6.0×l0-8 mol·m-2·s-1·Pa-1 at 923 K. The results in a packed-bed reactor (PBR) were compared to those of the membrane reactor at various temperatures (773-923 K) and pressures (1-20 atm, 101.3-2026.5 kPa) using a commercial Ni/MgAl2O4 catalyst. The conversion of methane was improved significantly in the MR by the countercurrent removal of hydrogen at all temperatures and allowed product yields higher than the equilibrium to be obtained. Pressure had a positive effect on the hydrogen yield because of the increase in driving force for the permeance of hydrogen. The yield of hydrogen increased with pressure and reached a value of 73×10-6 mol·g-1·s-1 at 2026.5 kPa and 923 K which was higher by 108% than the value of 35×10-6 mol·g-1·s-1 obtained for the equilibrium yield. The results obtained with the silica-based membrane were similar to those obtained with various other membranes as reported in the literature.     

Catalytic Combustion of Methane over CO1-xMgxO/Al2O3/FeCrAl Monolithic Catalysts

A series of CoxMgxO/Al2O3/FeCrAl catalysts （x=0-1） were prepared. The structures of the catalysts were characterized using XRD, SEM, and TPR analyses. The catalytic activity of the catalysts for methane combustion was evaluated in a continuous flow microreactor. The results indicated that the active washcoats adhered well on the FeCrAl foils. The phases in the catalysts were Co--xMgxO solid solutions, α-Al2O3, and γ-Al2O3. The surface particle size of the catalysts varied with variations in the molar ratios of Co to Mg. The Co component of the Co1_xMgxO/Al2O3/FeCrAl catalysts played an important role in the catalytic activity for methane combustion. In the Co1-xMgxO/AluO3/FeCrAl series catalyst （x=0.2-0.8）, the catalytic activity in terms of x was in the order of 0.5〉0.2〉0.8 under the experimental conditions. The presence of Mg in these catalysts could promote the thermal stability to a large extent. There were strong interactions between the Co1-xMgxO oxides and the AluO3/FeCrAl supports.     

甲烷在活性炭上裂解制氢研究

在连续流动石英固定床反应器上研究了甲烷在活性炭上裂解制氢的反应,并对反应前后活性炭的比表面积以及孔径分布等的变化进行了测定。结果表明,甲烷在五种活性炭上的裂解行为基本相同,反应初期转化率最高,随着反应进行转化率逐渐降低直至一个平稳的状态;降低甲烷分压和增加甲烷与活性炭的接触时间可提高甲烷转化率;温度的升高有利于初始转化率的提高,但不利于活性炭的稳定性;反应后活性炭比表面积、孔容及微孔孔容都明显降低,平均孔径增大,孔径分布向中孔方向迁移,说明甲烷的裂解导致了活性炭孔特别是微孔内的炭沉积以及进一步的孔堵塞。     

Fe、Mn掺杂六铝酸镧的微乳液制法及性能研究

以TX-100/正己醇/环己烷组成的反相微乳液为媒介,采用反相微乳 共沉淀法制备系列金属掺杂的六铝酸镧催化剂。用BET、XRD进行物性表征, 以甲烷燃烧为探针反应考察了催化剂的催化活性。结果表明,反相微乳液合成催化剂的最佳成晶温度可降至1100℃。 LaMx Al12－x O19－α 中M的最佳掺杂数为1(x1)。单金属Mn的存在可以降低甲烷的起燃温度,使催化剂具有良好的低温活性;单金属Fe掺杂的六铝酸镧催化剂具有较低的完全转化温度;而Fe、Mn共同掺杂的LaMnFeAl-10O19－α催化剂具有低、高温活性和高温稳定性。100h稳定性运转的转化率始终保持在99.7％,无失活现象。     

甲烷干气重整反应中镍基催化剂上表面积碳研究(英文)

镍基催化剂上积碳是甲烷干气重整反应急需解决的关键问题。实验采用ＴＰＳＲ、ＴＰＤ、ＸＰＳ和脉冲反应等方法系统研究了镍基催化剂表面积碳的形态和特点。热力学研究表明,在５７３ Ｋ到１２７３ Ｋ的温度范围内,催化剂的表面积碳是不可避免的。ＴＰＳＲ、ＸＰＳ和ＴＰＤ研究表明,甲烷在催化剂表面裂解将形成至少三种碳物种：Ｃα、Ｃβ和Ｃγ。这三种碳物种具有不同的表面迁移能力、热稳定性和反应活性。其中,Ｃα物种在甲烷干气重整反应中是一种非常活泼和重要的中间体;Ｃγ物种则可能是表面积碳的前驱物：部分脱氢的Ｃβ物种能够与Ｈ２或ＣＯ２反应生成ＣＨ４或ＣＯ。     

Mo/HZSM-5催化剂上甲烷无氧芳构化反应——HZSM-5分子筛脱铝的影响

采用两种不同的脱铝方法对HZSM-5分子筛进行了预处理,并利用MAS NMR和吸附吡啶的FT-IR对分子筛的结构和酸性质进行了表征,考察了分子筛的脱铝程度对Mo基催化剂上甲烷芳构化反应性能的影响.结果表明,HZSM-5分子筛的酸性过强或B酸量不足,均会导致催化剂严重积炭,但积炭成因不同.母体HZSM-5分子筛上的强B酸中心的存在可促使催化剂上反应中间物种深度脱氢,造成催化剂在反应过程中严重积炭.经水热处理的HZSM-5分子筛,骨架铝脱出严重,造成B酸活性中心不足以及部分微孔阻塞,不利于C2中间物种芳构化,导致芳烃选择性显著降低.经高温N2处理的HZSM-5分子筛,骨架铝脱出相对缓和,在消除母体分子筛上强B酸中心的同时,保留了较多的弱B酸中心,既可满足C2中间物种芳构化反应的需要,又可有效抑制催化剂积炭,导致甲烷芳构化反应性能显著改善.     

天然气的组成与应用

由于我国天然气资源的大量发现以及原油可开采量的减少,利用天然气的技术和规模都获得快速发展,天然气的研究与开发越来越受到人们的关注。本文介绍了天然气的组成与最新的应用进展。     

Theoretical and Experimental Study on the Adsorption and Desorption of Methane by Granular Activated Carbon at 25 ℃

A theoretical and experimental study was conducted to accurately determine the amount of adsorption and desorption of methane by various Granular Activated Carbon(GAC)under different physical conditions.To carry out the experiments,the volumetric method was used up to 500 psia at constant temperature of 25℃.In these experiments,adsorption as well as desorption capacities of four different GAC in the adsorption of methane,the major constituent of natural gas,at various equilibrium pressures and a constant temperature were studied.Also,various adsorption isotherm models were used to model the experimental data collected from the experiments.The accuracy of the results obtained from the adsorption isotherm models was compared and the values for the regressed parameters were reported.The results shows that the physical characteristics of activated carbons such as BET surface area,micropore volume,packing density,and pore size distribution play an important role in the amount of methane to be adsorbed and desorbed.     

Promotion Effects of Nickel Catalysts of Dry Reforming with Methane

The promotion effects of nickel catalyst of dry reforming with methane were extensively investigated by means of XRD, SEM, EDX, N₂‐adsorption and H₂‐adsorption. XRD characterization indicated that good dispersion of nickel oxide and MgO promoter is achieved over γ‐Al₂O₃ support. Addition of MgO promoter effectively retards the formation of NiAl₂O₄ phase. SEM and EDX analysis exhibited that the addition of rare‐earth metal oxide CeO₂ effectively promotes the Ni metal dispersion on the surface of the catalysts despite of undesirable self‐dispersion of CeO₂ promoter. Furthermore, the nickel component is gradually dispersed on the surface of the support following the exposure to reaction gas mixture for a period of time. The addition of MgO inhibited the self‐dispersion and promotion effect of CeO₂ on Ni dispersion on the catalysts. H₂ chemisorption revealed that the addition of the alkaline oxide MgO promoter significantly prohibits the metal dispersion on the catalyst. Inappropriate promoter addition can result in sharp decrease of the metal dispersion, N₂‐adsorption indicated that oxide promoter was mostly concentrated on the outer layer of the alumina support while the nickel metal was generally dispersed in the support pores. Addition of promoters contributed to more reduction in mesopore volume.     

Conversion of natural gas to C2 hydrocarbons via cold plasma technology

The plasma technology served as a tool in unconventional catalysis has been used in natural gas conversion, because the traditional catalytic methane oxidative coupling reaction must be performed at high temperature on account of the stability of methane molecule. The focus of this research is to develop a process of converting methane to C2 hydrocarbons with non-equilibrium plasma technology at room temperature and atmospheric pressure. It was found that methane conversion increased and the selectivity of C2 hydrocarbons decreased with the voltage. The optimum input voltage range was 40-80 V corresponding to high yield of C2 hydrocarbons. Methane conversion decreased and the selectivity of C2 hydrocarbons increased with the inlet flow rate of methane. The proper methane flow rate was 20-40 ml/min (corresponding residence time 10-20 s). The experimental results show that methane conversion was 47% and the selectivity of C2 hydrocarbons was 40% under the proper condition using atmospheric DBD cold plasma technology. It was found that the breakdown voltage of methane VB was determined by the type of electrode and the discharge gap width in this glow discharge reactor. The breakdown voltage of methane VB,min derived from the Paschen law equation was established.