分子筛在甲醇制汽油反应中的构效关系研究及催化性能优化
文献类型：学位论文
| 作者 | 周小龙 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05-22 |
| 授予单位 | 中国科学院大学 |
| 授予地点 | 北京 |
| 导师 | 吴晋沪 |
| 关键词 | 甲醇,汽油,构效关系,ZSM-5,二甲醚 |
| 学位专业 | 化学工程 |
| 中文摘要 | 甲醇制汽油技术是以煤或生物质为原料制得高品质液体燃料的关键技术，ZSM-5是这一技术最为常用的催化剂。本文主要研究ZSM-5分子筛在甲醇制汽油反应中的构效关系及催化性能优化。 首先确定目标催化剂，对其对甲醇制汽油反应 (MTG) 的催化性能进行了评价，发现MTG反应可分为诱导期，稳定期和失活期三个时期。对目标催化剂于MTG反应中的结构，酸性和积炭的变化进行了系统的研究后发现：催化剂在反应过程中会脱铝形成一层硅氧层，结构发生改变；催化剂酸性在诱导期快速减弱，在稳定期和失活期基本保持不变，酸性影响着积炭物种的生成和积炭速率的变化，也影响双周期转换的产物分布，较强的酸性有利于裂解反应和烯烃循环的进行，芳烃循环此时受到抑制，因此在反应初期C3类产物的收率最高，而随着反应的进行，催化剂酸性快速降低，双循环达到稳定，C3产物收率降低，汽油品质趋于稳定；积炭首先是石墨炭在催化剂的外表面形成，然后逐渐向外层生长，之后孔道内的芳烃类物质会逐渐堵塞在分子筛孔道内成为积炭物种。在稳定期结束，积炭累积以及酸性减弱到一定程度，催化剂活性大大降低，甲醇转化率降低，油品变化较大。催化剂的结构，酸性和积炭三者相互影响，他们一同决定了MTG反应的产物变化。 对ZSM-5进行了铁，铜和镓的常规金属浸渍改性，发现Fe/ZSM-5相较于其他催化剂具有较高的油收率和较低的芳烃选择性。比较了原位合成改性同常规浸渍改性Fe/ZSM-5催化剂的催化效果，选择原位合成改性FeZSM-5为进一步改进催化剂，确定了FeZSM-5中铁含量同油收率的关系。 在FeZSM-5运用于MTG反应中的评价结果发现，充分的焙烧以及适当的水热对催化剂的活性和寿命有一定程度的提高，而催化剂粒度以及粘结剂含量在一定范围内对其活性和寿命影响均不大。对FeZSM-5催化剂在二甲醚制汽油 (DTG) 反应中的条件进行了初步探索，发现随着DTG反应温度的升高，甲醇转化率逐渐增高，油收率先增加后降低，催化剂寿命逐渐减短；空速对转化率影响不大，与油收率基本呈正相关，而寿命则随着空速的增加显著降低。 |
| 英文摘要 | Methanol to gasoline (MTG) is a key technology for the synthesis of liquid fuelwith high quality from coal or biomass, usingtraditional ZSM-5 zeolite as catalyst. In this study, the structure-function relationship and optimization of catalytic performanceof ZSM-5 were investigated in the MTG process. Firstly, target catalysts were chosen and evaluated in MTG process. And it is found that the MTG process can be classified into 3 periods, including induction, stationary, and deactivation period. The structure, acidity, and coke depositionof the catalysts were further studied systematically: The results indicated that a silicate-like shell formed during the reaction because of dealumination, resulting in the change of catalyst structure; The acidityof the catalyst decreased rapidly in the induction period and remained stable in the stationary and deactivation period. The acidity is responsible for the coke species and coke formation speedas well as product distributionin the dual-cycle conversion. Stronger acidity favors the alkene cycle and restrains the aromatic cycle, therefore, the yield of C3 products was high at first.With increase in reaction time, the acidity decreased rapidly and the dual-cycle reached its balance with respect to the lower yield of C3 products and thestable quality of oil .Furthermore, graphite-like coke initially formed in the outer surface of the catalyst, then graduallygrew to outer layer;then the aromatic speciesstarted to block the channels and cavities of catalyst and finally became coke. At the end of stationary period, the coke accumulation and low acidity made the catalyst activity decrease shaply, resulting in the decrease ofmethanol conversion and the quality of oil products. The interrelationship between structure, acidity, and coke depositionof the catalysts finally influenced the product distribution in the MTG process. The catalytic property of the zeolites impregnated with iron, copper and gallium for the MTG reaction was also investigated.The results indicated that zeolite impregnated with iron possessed relatively high oil yeild and low selectivity of aromatic. Moreover, The comparison in catalytic performance between thein-situ and traditionaldoping catalyst was also compared In-situ doping FeZSM-5 with different ratio of iron was used as catalyst to confirm the relationship between the content of iron and the oil yield. Further evaluation in the catalytic performance of ZSM-5 in MTG processshowed that sufficient calcination and proper hydrothermal treatment temperature can partly improve the catalyst activity and lifetime, however, the particle size of catalyst and the ratio of binder slightly affect the catalyst performance. The reaction conditions of dimethyl-ether to gasoline (DTG)were also initially explored.The results indicated thatthe conversion of methanol increased with increase in reaction temperature.However, oil yield increased first and then decreased, and catalyst lifetime gradually reduced.Space velocity slightlyinfluenced the DME conversion and had a positive correlation with oil yield, while the catalyst lifetimewas reduced sharply with the increase of space velocity. |
| 学科主题 | 化学工程 |
| 语种 | 中文 |
| 公开日期 | 2019-06 |
| 源URL | [http://ir.qibebt.ac.cn/handle/337004/8112]  |
| 专题 | 青岛生物能源与过程研究所_热化学转化事业部 |
| 作者单位 | 中国科学院青岛生物能源与过程研究所 |
| 推荐引用方式 GB/T 7714 | 周小龙. 分子筛在甲醇制汽油反应中的构效关系研究及催化性能优化[D]. 北京. 中国科学院大学. 2014. |
入库方式： OAI收割
来源：青岛生物能源与过程研究所
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