【作者】 张秀玲；

【导师】 刘长厚； 宫为民；

【作者基本信息】 大连理工大学 ， 化学工艺， 2002， 博士

【摘要】 天然气的主要成分是甲烷。近年来，随着世界性石油资源短缺，开辟以甲烷为原料替代石油资源的基本有机化工合成路线是十分富有挑战性的研究课题之一。甲烷氧化偶联（OCM）反应因其所具有的潜在工业前景而倍受瞩目，虽然以氧气为氧化剂活化甲烷是行之有效的，但深度氧化难以避免。鉴于此，以弱氧化性气体CO₂为氧化剂的甲烷偶联反应研究逐渐活跃，但甲烷转化率较低，主要原因是CH₄和CO₂分子结构稳定难以活化。 高压脉冲电晕等离子体是一种新型等离子体技术，可在常压及低温下工作，具有电子能量适中、有利于CH₄和CO₂分子活化，操作简单、能量利用率高等优点，已在小分子活化研究领域得到应用。本论文采用脉冲电晕等离子体技术研究CH₄-CO₂转化反应，实现了等离子体催化共活化CH₄-CO₂一步制C₂烃反应，并对等离子体作用下CH₄-CO₂转化反应机理进行了较为深入的研究。本论文的主要研究内容和结果如下： 1．在脉冲电晕等离子体作用下实现了甲烷、二氧化碳共活化转化反应，反应的主要产物是C₂烃（C₂H₂、C_@H₄、C₂H₆）CO和H₂，另有少量H₂O生成；研究还发现反应器结构、进气方式及原料气组成可在一定程度上影响CH₄和CO₂转化率及C₂烃选择性；增加反应体系能量密度，反应物转化率、产物收率增加；当能量密度在800 kJ／mol-2200kJ／mol范围内变化时，甲烷、二氧化碳转化率分别为26.0％-43.6％和17.8％-58.4％，C₂烃收率为8.6％-20.6％。 2．较系统地考察了脉冲电晕等离子体与二十余种催化剂共活化CH₄-CO₂制C₂烃反应。结果表明部分负载型金属氧化物催化剂有利于C₂烃的形成，但活性不同。按C₂烃收率大小，活性较高的四种金属氧化物催化剂依次为；La₂O₃／γ-Al₂O₃＞CeO₂／γ-Al₂O₃＞Na₂WO₄／γ-Al₂O₃＞BaO／γ-Al₂O₃；当能量密度为1300kJ／mol时，等离子体与La₂O₃／γ-Al₂O₃作用下C₂烃产物收率是18.1％，比单纯等离子体作用下C₂烃收率净增加5.4％。负载型金属催化剂对反应物转化率影响不大，但Pd／γ-Al₂O₃催化剂对C₂烃产物分布有明显影响，当Pd负载量为0.01％时，C₂烃产物中C₂H₄的摩尔分数可达77％。 3．筛选出适于和等离子体结合共活化CH₄-CO₂制C₂H₄的优良催化剂Pd-La₂O₃／γ-Al₂O₃。摘要 大连理工大学博士学伎论文 （门 确立了活性组分L二。0。和H的最佳负载量分别为5％和0．0凋：考察了原 料气组成、空速、能量密度及进气方式对等离子体与Pdb刀山亿。0。催 化剂共同作用下CH。－CO。制C山。反应的影响。实验证明当反应气由等离 子体区流向等离子体－催化区有利于提高C。烃选择性和收率。 （2）比较了等离子体－催化法、催化法和等离子体法H种活化方式对CH。－CO； 制C。烃反应的影响，相比之下等离子体－催化共活化具有更高的C。产物 收率和能量利用率。 臼）运用热重、X－衍射等仪器分析手段初步分析了Pd1a刃卜叫山。催化剂积 炭成因。4．利用发射九谱原位诊断技术在250～670urn波长范围内检测等离子体作用下 CH个CO。转化反应中若干激发态物种，主要有：CH、C、CZ、CO。和CO。依 据反应过程中活性物种、反应主要产物及脉冲电晕等离子体特性，推断等离子 体作用下CH4( 转化反应为自由基历程，并提出转化反应机理模型。首次检 测到活性物种CZ，并据此提出CH4－COZ转化反应中主要产物CZH。和CO的新 反应机制。5．研究了纯CZH。在等离子体条件下发生的脱氢反应，主要产物是CZHZ和 CZH4；考察了等离子体注入功率、添加气体 HZ或 NZ对 CZH6脱氢反应的影 响；等离子体与催化剂共活化CZH6( 转化反应条件与CH4( 转化反应条 件相似，其反应产物也基本相同，这为温和条件下CH4和C刃。混合气不经分 离，直接转化利用提供了实验依据。更多还原

【Abstract】 Methane is a principal component of natural gas. With the lack of crude oil resources in the world, the development of methane utilization as the feedstock, instead of crude oil, for the production of chemical has been extensively studied. The oxidative coupling of methane (OCM) to C2 hydrocarbons is an attractive process for its potential industrial foreground. Although the OCM reaction over metal oxide catalysts by oxygen is effective, as shown that the oxidation products, CO: is unavoidable. In this regard, the oxidative coupling methane using CO: as a mild oxidant is becoming active. The conversion of methane is lower than that using 0: The difficulty in effective conversion is due to the high dissociation energy of methane and carbon dioxide.The pulse corona plasma represents a novel technology for generating a highly non-equilibrium cold plasma in which conditions the electron temperature is very high but the ionic or molecular temperature is low. So the great advantages of pulse corona plasma is that less energy goes into heating the gas at atmospheric pressure. In this paper, pulse corona plasma has been used as a new method for direct conversion methane into C: hydrocarbons using CO2 as an oxidant under low temperature and atmospheric pressure. First, the synergism of plasma and various catalysts in the reaction of CEU and CO2 was studied. Then, the reaction mechanism involved in CH4 and CO: reaction under pulse corona plasma was discussed. The main results are summarized as following:1. The reaction of CH4 and CO2 can be driven by means of pulse corona plasma without any catalyst. The main gaseous products consisted of C: hydrocarbons (C2H2, C2H6 and C2H4), CO and H2. Some little liquid products, such as water and liquid hydrocarbons were found in this reaction. The effects of reactor configuration, the ways of feed inflow and the composition of feed on the reaction were investigated. The conversion of CH4, CO2 and the yield of C2hydrocarbons, CO increased with increasing energy density, The yield of C2 hydrocarbons of 8.6%~20.6% with a methane conversion of 26.0%~43.6% and a carbon dioxide conversion of 17.8%~58.4% at energy density 800kJ/mol~2200 kJ/mol had been received.2. The synergism of plasma and various catalysts on the reaction of CH4 and C02 was investigated. Some metal oxide catalysts had high €2 yield. The order of four catalysts activities is: La2O3/Y-Al2O3> CeO2/Y-Al2O3> Na2WO4/y-Al2O3>BaO/Y-Al203. The largest C2 yield was obtained (18.1%) when using La2O3/Y-Al2O3 as catalyst at energy density 1300kJ/mol. The yield of C2 increased 5.4% than that in plasma without any catalyst. The Pd/Y-Al2O3 catalyst shows high C2H4 selectivity, C2H4 accounted for 77% of the carbon distribution of C2~C3 hydrocarbons under plasma and Pd/Y-Al2O3 catalyst loaded 0.01% Pd.3. The Pd- La2O3/Y-Al2O3 is an excellent catalyst for direct conversion CH4 and CO2 into C2H4 under pulse corona plasma. The optimum loading of Pd and La2O3 is 0.01% and 5% respectively. The effect of various factors including the composition of feed, space velocity and input power on the reaction of CH4/CO2 were investigated in detail with Pd- La2O3/Y-Al203 catalyst under plasma. The results indicate that formation C2 hydrocarbons are favored when the feed flows from plasma area to plasma-catalyst area. The activation method of plasma-catalyst shows the highest C2 hydrocarbons yield and energy efficiency than that catalytic method or plasma method. The reasons of coke formation were analyzed by TG as well as X- ray diffraction technique.4. Some active species, such as CH, C, C2, CO2 and CO, were determined by optical emission spectroscopy at the range of 250nm~670nm wavelengths. According to the active species and products of reaction, the possible pathwaysof reaction were established for CH4 and CO2 conversion under pulse corona plasma. New pathways for C2H2 and CO formation were suggested.5. Pulse corona plasma was used as an active method fo更多还原