甲醇/二甲醚制汽柴油新型催化剂的设计及催化作用机制的研究
文献类型：学位论文
| 作者 | 狄佐星 |
| 学位类别 | 博士 |
| 答辩日期 | 2013-07 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 吴晋沪 |
| 关键词 | ZSM-5/MCM-48 选控合成 MTG 积炭 碳链增长 |
| 学位专业 | 化学工程 |
| 中文摘要 | 全球石油资源日益枯竭，我国国民经济的发展也面临越来越严重的资源和环境压力。加快发展新型煤化工和生物质化工技术已经成为我国政府、企业和学术界的共识，煤/含碳生物质气化合成经由甲醇/二甲醚制取高品质液体燃料和化学品是当前国内外研究的热点。甲醇可以在酸性分子筛催化剂或分子筛类似物上先脱水生成二甲醚，然后转化成碳氢化合物（MTH）。通过调节分子筛的类型和结构可以达到选择控制烃类产物的目的，已经可以高选择性地合成汽油(MTG)、芳烃(MTA)、低碳烯烃(MTO和MTP)等石化产品，但还未见可直接合成柴油/航空煤油的报道。上世纪80年代，Mobil公司发现的ZSM-5分子筛以其独特的孔道结构在MTG反应中表现出良好的催化性能，但是由于分子筛催化的择形性，仍存在油品碳数范围仅限C11以下，其中芳烃特别是均四甲苯含量较高，且易积炭需要频繁再生等问题，限制了其工业应用和推广。本论文针对甲醇选控合成烃类液体燃料反应网络特点，将ZSM-5/MCM-48复合分子筛材料应用于MTG反应过程，主要研究内容包括：（1）采用两步晶化法合成出ZSM-5/MCM-48复合分子筛材料，在追踪制备过程中对晶化时间、晶化碱度、老化速度等合成条件进行了详细的考察，并通过XRD，SEM，HRTEM，FTIR，N2吸附，NH3-TPD，吡啶红外等表征方法进行系统研究。发现ZSM-5前驱体的晶化时间是合成ZSM-5/MCM-48复合分子筛的重要影响因素，具有完整的MFI微孔结构和介孔结构的复合分子筛基催化剂表现出良好的MTG反应性能，有效降低了油品中芳烃和均四甲苯的含量。（2）通过附晶生长法合成ZSM-5/MCM-48复合分子筛材料以实现了介孔MCM-48对微孔ZSM-5表面进行孔道结构和表面性质的修饰，从而更为显著的降低了油品中芳烃组分的含量，并使烃类产物碳链有效增长到C12以上，突破了传统MTG反应的概念。（3）对ZSM-5/MCM-48复合分子筛催化剂进行了稳定性、强制失活（穿透试验）与再生研究。实验结果表明复合分子筛基催化剂上的结炭类型与ZSM-5基催化剂存在较大差异，主要是一些链烃、低聚物或烷基取代的单芳香烃化合物，较易在低温燃烧，从而可以提高催化剂的抗积炭能力，延长催化剂的使用寿命。而对MTG反应进程中ZSM-5/MCM-48复合分子筛催化剂上的积炭行为进行动态跟踪研究发现：在反应的初始阶段仅有轻微积炭，主要是一些链烃、低聚物、烷基取代的单芳香烃化合物和具有无定型结构的游离炭；随着反应的进行这些非芳烃和单芳烃的积炭小分子逐渐形成烃类大分子或稠环芳烃；提高甲醇空速后改变了积炭的组成，使得反应中生成了更多较难消除的稠环芳烃，从而加速了催化剂活性下降。（4）将两步晶化法和附晶生长法分别制备的ZSM-5/MCM-48复合分子筛基催化剂与机械混合法制备的复合材料催化剂进行比较研究。反应活性和选择性结果都证明了H-ZSM5物相是MTG反应的活性中心，但介孔结构以特定方式与H-ZSM5的微孔结构结合可以对反应的历程产生重要的影响，较为明确的阐明了甲醇选控合成液体烃类产物的碳链增长机制、反应和结炭（消碳）机理模型。 |
| 英文摘要 | Global oil become increasingly depleted, development of the national economy also faced increasingly severe resource and environmental stress. Speeding up the development of new types of coal and biomass technology has become the consensus of the government, enterprises and the academic community, while much research has been focused on transportation fuels, such as gasoline and diesel production from coal or carbon-containing biomass gasification via methanol/dimethyl ether.Synthesis of dimethyl ether through methanol dehydration reaction occurred on acidic zeolite catalyst or molecular sieve analogues, and then transformed into hydrocarbons (MTH). Selection control of hydrocarbon products can be achieved by adjusting the type and structure of the molecular sieve, thus several process has been developed for gasoline (MTG), aromatics (MTA), olefin(MTO) and propylene (MTP) production, yet the direct synthesis of diesel/jet fuel has not been reported. In the 1980s, Mobil found ZSM-5 zeolite, which showed good catalytic performance in the MTG reaction due to its unique pore structure. However, the MTG process still suffers from high yields of aromatics, especially durene in oil phase, and carbon deposition thus requiring frequent regeneration. These limited its industrial application and promotion, except that the range of hydrocarbons in C11 only.In this thesis, we focused on the network of methanol transformation and introduced ZSM-5/MCM-48 composite material into MTG process with the main goal of selective-controlled synthesis of hydrocarbon liquid fuel. The main contents of our work are as follow:(1) ZSM-5/MCM-48 composite materials have been prepared using a simple two step crystallization method. In tracking the proceeding of preparation, conditions of crystallization time, crystallization alkalinity and the aging rate were performed in detail. The structural and surface properties of the composite materials and the as-prepared catalysts were investigated by using of XRD, SEM, HRTEM, FT-IR, N2-adsorption, NH3-TPD and Py-FTIR techniques. It was found that ZSM-5 precursor crystallization time played an important role in the synthesis of ZSM-5/MCM-48 composite, which owned a complete microporous structure of ZSM-5 mesoporous structure of MCM-48 showed good performance in MTG reaction, effectively reducing the content of aromatic hydrocarbons and durene in the oil. (2) ZSM-5/MCM-48 composite molecular sieve material synthesized by the overgrowth method in order to achieve the mesoporous MCM-48 modifying the pore structure and surface properties of the microporous ZSM-5 crystal seed, which significantly reduced the aromatic content of in the oil product, making the product of hydrocarbon carbon chain effectively grow to more than C12, breaking the concept of traditional MTG.(3) The stability, forcing deactivation and regeneration on the composite molecular sieve catalyst were further to be tested. Experimental results showed that the type of coke deposition on composite zeolite-based catalyst and ZSM-5-based catalyst were quite different. Some chain hydrocarbons, oligomers or alkyl-substituted aromatic hydrocarbons were formed on the ZSM-5/MCM-48 catalyst, the coke was easy combustion in low temperature. It was concluded that the introduction of MCM-48 improve the resistance to coke deposition and extend the life of the catalyst. In the dynamic tracking study of carbon deposition: (i) only slightly coking in the initial stage of the reaction, it is chain hydrocarbon, oligomers or alkyl-substituted mono-aromatic hydrocarbon compound having an amorphous structure of the free carbon; (ii) as the reaction proceeding, these non-aromatic hydrocarbons and a single aromatic molecule gradually formed hydrocarbons macromolecule or polycyclic aromatic hydrocarbons; (iii) when improving the methanol feed speed, polycyclic aromatic hydrocarbons which is more difficult to eliminate is formed, thereby accelerating the deactivation of the catalyst.(4) A comparative study of the two-step crystallization method, overgrowth method and mechanical mixing of the composite were conducted. The catalytic performance of either activity or selectivity proved that the H-ZSM5 was the active center in MTG reaction, however the combination of the mesoporous structure with the microporous structure in H-ZSM5 by a definition method greatly influenced on the reaction pathway. Moreover, a mechanism model of methanol to hydrocarbon reaction was proposed to clearly explain the carbon chain propagation, reaction and coke deposition /elimination. |
| 学科主题 | 热化学转化 |
| 语种 | 中文 |
| 公开日期 | 2013-07-13 |
| 源URL | [http://ir.qibebt.ac.cn:8080/handle/337004/1505]  |
| 专题 | 青岛生物能源与过程研究所_热化学转化事业部 |
| 推荐引用方式 GB/T 7714 | 狄佐星. 甲醇/二甲醚制汽柴油新型催化剂的设计及催化作用机制的研究[D]. 北京. 中国科学院研究生院. 2013. |
入库方式： OAI收割
来源：青岛生物能源与过程研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。