钴基催化剂催化生物质合成气F-T合成的实验研究

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	钴基催化剂催化生物质合成气F-T合成的实验研究
其他题名	Experiment Study of Fischer-Tropsch Synthesis from Biomass Syngas over Cobalt-based Catalysts
	覃欣欣
导师	王铁军
	2009-05-31
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	硕士
关键词	生物质合成气钴基催化剂 F-t合成锰助剂
摘要	生物质能是仅次于煤炭、石油和天然气而居于世界能源消费总量第四位的能源，它不仅可用于取热和发电，而且也是可再生能源中唯一可以转化为液体燃料或化学品的碳源。第二代生物质液体燃料由于其原料来源稳定、不会和粮食相互竞争，具有非常巨大的发展前景，其中通过气化合成液体燃料的生物质间接液化技术被认为是最有效的方式之一。F-T合成（Fischer-Tropsch synthesis）是以煤、石油、天然气为原料的有机化工中常用的C1化学反应，是生物质合成液体燃料的原理基础，可将生物质合成气（CO+H2）转化为不同链长的碳氢化合物。我国的生物质F-T合成液体燃料技术尚处于实验研究阶段，开发适用于生物质气质特点的催化剂体系和F-T和合成工艺具有重要的科学和现实意义。本文侧重研究生物质合成气在传统F-T合成催化剂Co/SiO2上的反应性能，并通过添加助剂对催化剂进行改性，以提高生物质合成气F-T合成的转化率为目标，主要研究内容包括：（1）在传统F-T合成Co基催化剂，固定床微型反应器上考察并对比工业合成气（H2/CO=2）和生物质合成气（H2/CO=1，含有CO2）F-T合成反应的差别；（2）添加Mn助剂对Co/SiO2催化剂进行改性，考察不同含量的Mn助剂对工业合成气和生物质合成气F-T合成转化率及产物分布的影响。（3）采用X射线衍射（XRD），H2程序升温还原（H2-TPR），热重红外联用等手段对催化剂进行表征。通过实验研究得到以下主要结论： 1、在240oC，2.0MPa，1000h-1典型的F-T合成反应条件下，分别用工业合成气和模拟生物质合成气在Co/SiO2催化剂上进行反应。（1）所制备的20wt% Co/SiO2催化剂具有较高的F-T合成反应活性，工业合成气CO转化率可达90%以上。（2）生物质合成气可以在Co/SiO2催化剂上通过F-T合成反应生成液态烃类，且CH4选择性低。但与工业合成气相比，生物质合成气CO转化率低，小于30%，且催化剂失活较快。产物分布向高碳数迁移，C5+烃类选择性可达80.62%，24h后C5+收率平均值为131.30 g/m3 (syngas)。 2、在Co/SiO2催化剂中添加不同含量的Mn助剂进行改性，Mn助剂的添加量为：0.4，0.8，1.5，2.0，5.0，7.0 wt%，比较了Mn助剂对工业合成气和生物质合成气F-T合成的影响。（1）XRD、H2-TPR测试结果表明，Mn助剂的添加会影响Co/SiO2催化剂的分散度和Co3O4晶粒尺寸。Co和Mn可能生成低温难还原的CoMn氧化物，从而阻碍了Co的还原。（2）少量Mn的添加（0.4%，0.8%）可以提高生物质合成气CO转化率和C5+烃类选择性。Mn含量为0.8%时，CO转化率最高为52.55%，产物中CH4含量较低，CH4选择性为9.93%；随着Mn含量的增大，CO转化率变小，C5+烃类选择性降低，且产物中烯烃含量增大。（3）添加适量Mn有利于增加催化剂的稳定性及延长催化剂的寿命。Co-(0.8%)Mn/SiO2催化剂稳定性实验结果表明，24h后CO的平均转化率由29.13%（Co/SiO2）提高到42.38%，C5+烃类平均选择性为78.99%，平均收率为154.9 g/m3 (syngas)（4）催化剂的失活原因之一是由于碳的沉积以及少量蜡样产物沉积引起的。由于转化率不高，尾气具有一定热值，出口尾气流量约占合成气流量的50%，经过计算得到尾气热值为14.54MJ/Nm3。
其他摘要	Biomass energy is the forth in the world total energy consumption, coming only after coal, oil, and natural gas. As a carbon resource, biomass not only can be used for heat and power generation, but it also is the only renewable energy which can be converted into liquid fuels or chemicals. Compared to the first generation biofuels the second generation biofuels have greater prospects for development, because the feedstocks are non-food crops and are more stable in supply. Biomass indirect liquefaction through gasification is regarded as the most efficient way of utilizing biomass. The FTS (Fischer-Tropsch synthesis) is a commonly used reaction in organic chemical, which is taking coal, oil or natural gas as feedstocks. FTS is the basic principle of BTL (biomass to liquid) process and produces hydrocarbons of different length from a gas mixture of H2 and CO (syngas) from biomass gasification. At present, FTS using coal and natural gas is almost a well-established technology. However, as for FTS from biomass-derived syngas, it is still limited in laboratory stage. It is significant in science and practice to research & development proper catalyst systems and FTS processes for the biomass derived syngas. The aim of the present work is to study the FTS of biomass derived syngas on traditional FTS catalysts, and to improve the conversion by adding promoters, including: (1) under typical FTS reaction condition, comparing the reaction performances of industrial syngas (H2/CO=2) and biomass syngas (H2/CO=1, containing CO2) over traditional FTS catalyst, in a fixed bed microreactor; (2) investigating the effect of manganese promoter with different loadings on the conversion and product distribution of the syngas; (3) characterizing the catalysts by XRD, H2-TPR, and TGA-FTIR. The results obtained are listed as follows: 1. FT reactions were carried out under 240oC, 2.0MPa, 1000h-1, using industrial syngas and biomass syngas as feedgas.It was found that (1) the 20wt% Co/SiO2 catalyst used had higher activity and the CO conversion of the industrial syngas was over 90%; (2) FTS from the biomass syngas is possible to obtain liquid hydrocarbons over Co/SiO2 catalyst, and the selectivity of CH4 is lower. However, the CO conversion of biomass syngas (less than 30%) is much lower than that of industrial syngas. The product of biomass syngas tended to be higher carbon number hydrocarbons, and the selectivity of C5+ was 80.62%. The average yield of C5+ after 24h-reaction was 131.30g/m3(syngas). 2. The Co/SiO2 catalyst was promoted by impregnation with different amounts of manganese (0.4, 0.8, 1.5, 2.0, 5.0, and 7.0 wt%). (1) It was shown by XRD and H2-TPR that Mn made the particle size of Co3O4 be smaller and hampered the reduction of Co3O4 to Co0, which probably was caused by formation of CoMn oxides. (2) FT catalytic test revealed that small amount of Mn (0.4%, 0.8%) could increase the CO conversion and selectivity of C5+. On the cobalt catalyst promoted by 0.8% Mn, the CO conversion of biomass syngas was the highest (52.55%) and CH4 selectivity is lower(9.93%). Loading of more than 0.8% Mn resulted in a decrease in activity and C5+ selectivity and an increase in olefin content in light hydrocarbons. (3) Stability of the cobalt catalyst in the atmosphere of biomass syngas was improved by adding Mn. The average CO conversion after 24h-reaction was increased from 29.13% (over Co/SiO2) to 42.38% (over Co-(0.8%)Mn/SiO2).The average selectivity of C5+ hydrocarbons was 78.99%, and the average yield was 154.9g/m3(syngas) (4) The average flux of the off-gas accounted for about 50% of the syngas. Based on the composition, the heat value of the FT off-gas of biomass syngas over Co-(0.8%)Mn/SiO2 is about 14.54 MJ/m3. Deposition of carbon and small amount of heavy hydrocarbons on the catalysts surface was one of the possible reasons for the catalyst deactivation.
页数	79
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/4029
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	覃欣欣. 钴基催化剂催化生物质合成气F-T合成的实验研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2009.

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