甲醇制丙烯催化剂的结构调控与性能研究

发布时间：2018-05-09 06:34

本文选题：甲醇制丙烯 + HZSM-5　；参考：《浙江大学》2015年博士论文

【摘要】：甲醇制丙烯(MTP)技术是一项相对独立的丙烯生产技术。MTP技术的成功开发与广泛应用,代表着非传统“煤基路线”或“天然气/页岩气路线”增产丙烯技术的日趋成熟与完善,对保障我国的能源安全以及奠定未来的化工产业格局具有十分重要的意义。MTP技术开发的首要指标与核心竞争力,是催化剂的高丙烯选择性以及稳定性。提高催化剂的丙烯选择性和稳定性的调控手段,主要基于改善催化剂的传质扩散性能以及构建或修饰分子筛酸分布,然而现有的调控手段普遍是“离线”调控,即未考虑或未结合反应因素对催化剂结构的“实时”调变,故不能很好地满足催化剂对高丙烯选择性与反应稳定性的双项要求。本文围绕MTP反应因素对HZSM-5催化剂结构的调变开展研究。通过建立孔道环境与分子扩散行为的相互联系,分别研究了水蒸汽老化对积炭的抑制作用、预积炭以及再生对二次积炭的导向作用,揭示了反应气氛、积炭、再生等因素对催化剂孔道及酸性的作用机制,提出了积炭调控协同水调控的技术路线。进一步地,研究了积炭与水协同调控在MTP两步法反应中的应用,并提出了移动床MTP工艺的“炭循环”技术方案。基于水蒸汽老化剂,建立了结合炭含量因子的MTP反应动力学,为MTP移动床反应器的开发与设计提供了指导。具体研究工作与结果如下：(1)通过建立孔道环境与分子扩散行为的相互联系,研究了水蒸汽老化对结焦的延缓机制。基于重量法研究了甲醇与甲苯分子在具有不同孔结构参数的老化剂内的扩散行为,提出了有利于改善传质扩散性能的介孔形态。通过对比考察以提高空速为手段与以延长时间为手段,两种蒸汽处理条件下催化剂的介孔网络分布与积炭速率,提出了构建“外向型”介孔网络以延缓催化剂积炭的方法。(2)考察了N2与H20作为稀释气对HZSM-5结构及其催化MTP反应性能的影响,并研究了水在分子筛酸性位的“化学吸附”随时间的作用规律,发现水促使分子筛脱铝主要发生在反应初期,且作用对象为不稳定的非骨架铝。基于水的这种作用机制,将新鲜催化剂进行短时间的蒸汽老化,通过水的快速脱铝作用降低催化剂的酸密度并减少水的吸附位点,以此提高催化剂对丙烯选择性与反应稳定性。针对催化剂的水热脱铝问题,研究了在线补酸与在线补磷技术对催化剂酸性的调控。考察了柠檬酸浓度、处理温度、以及时间对催化剂酸分布的影响,发现柠檬酸通过将部分非骨架铝转变为骨架铝从而增加了分子筛的酸性位。基于柠檬酸的这种作用机制,提出了结合在线补酸的水蒸汽老化技术。考察了磷含量、前驱液浓度、温度、处理时间对磷、铝形态及其分布的影响,发现在线补磷的高温环境是实现磷与骨架铝配位的直接诱导因素。通过进一步考察补磷催化剂的水热稳定性,验证了在线补磷对稳定骨架铝的作用及效果。(3)研究并建立了以积炭作为调控手段的催化剂改性方法。考察了低温炭形态与高温炭形态随温度与时间的变化,揭示了低温炭向高温炭的演变过程。设计了在不同温度、原料、时间下制备的积炭剂,研究了积炭对催化剂结构的修饰作用及其对二次积炭的导向作用,提出了以积炭调控辅助水调控的催化剂改性方法。通过研究高温积炭在低温下的二次积炭行为,与低温积炭在高温下的二次积炭行为,提出了移动床MTP两步法工艺的“炭循环”技术。(4)研究了不同反应-再生周期中焦的生长规律及催化剂失活规律。通过研究催化剂在高、低空速下反应的积炭分布,发现高甲醇空速致使其壳层积炭而失活,而低甲醇空速则致使其晶内积炭而失活,显示出不同的失活机理。通过跟踪甲醇、甲苯、异戊烷分子在不同程度积炭剂内的扩散行为,提出了积炭“由内而外”地生长过程。通过对比研究新鲜催化剂与再生催化剂的积炭行为与反应性能,揭示了第一周期水与第二周期积炭对催化剂失活的竞争作用。(5)采用水蒸汽老化剂为研究对象,在等温固定床反应器中考察了甲醇单独反应、甲醇分别与C2-C6烯烃耦合反应的产物分布随甲醇空速(3-40(gmethanol/ gcat·h)和反应温度(420～500℃)的变化规律,研究了甲醇平行反应、烯烃甲基化反应、以及烯烃叠合与裂化反应的竞争关系。在低甲醇空速(0.5～5 gmethanol/ gcat·h)下,通入丙烯作为烯烃氢转移与芳构化反应的促进剂,研究了MTP反应中芳烃与丙烷的生成路径。建立了可准确描述甲醇、乙烯、丙烯、丙烷、C4、C5、C6、C7+及芳烃等9种组分或集总组分生成与消耗速率的MTP反应动力学模型,并在模型中引入了炭含量因子以考虑催化剂的积炭失活。模型适用于预测MTP反应或醇烃共炼MTP反应在初始阶段以及不同积炭阶段的产物组成。
[Abstract]:The technology of methanol propylene (MTP) is a successful development and wide application of a relatively independent propylene production technology.MTP technology. It represents the increasing maturity and perfection of the non traditional "coal based route" or "natural gas / shale gas route" to increase the production of propylene. It will guarantee the energy security of our country and establish the future industrial pattern of chemical industry. The primary index and core competitiveness of.MTP technology development are very important. It is the high propene selectivity and stability of the catalyst. To improve the selectivity and stability of the catalyst, it is mainly based on the improvement of the mass transfer performance of the catalyst and the construction or modification of the distribution of molecular sieve acid. However, the existing regulation means It is "off-line" regulation, that is, the "real time" modulation of the catalyst structure is not considered or uncombined, so it can not meet the dual requirements of the catalyst for selectivity and stability of the catalyst. This paper studies the modulation of the structure of the HZSM-5 catalyst by the MTP reaction factors. The effects of water vapor aging on carbon accumulation, pre carbon deposition and the guiding effect of regeneration on two carbon deposits were studied, and the mechanism of reaction atmosphere, carbon accumulation, regeneration and other factors on the catalyst pore and acidity were revealed, and a technical route for regulating carbon accumulation and regulating water was proposed. The application of CO regulation with water in the MTP two step process and the "carbon cycle" technology of the mobile bed MTP process is proposed. Based on the water vapor aging agent, the MTP reaction kinetics with the carbon content factor is established, which provides guidance for the development and design of the MTP mobile bed reactor. The specific research work and results are as follows: (1) through establishment The interaction between the pore environment and the molecular diffusion behavior is studied. The diffusion behavior of methanol and toluene in the aging agent with different pore structure parameters is studied based on the gravimetric method, and the mesoporous morphology is proposed to improve the mass transfer diffusion properties. The air velocity is improved by comparison and investigation. Methods and the distribution of mesoporous network and carbon deposition rate of the catalyst under two steam treatment conditions, the method of constructing "export-oriented" mesoporous network to delay the catalytic carbon deposition was proposed. (2) the effects of N2 and H20 as diluent on the structure of HZSM-5 and the catalytic performance of MTP were investigated, and water was studied in molecular sieve. The effect of "chemical adsorption" of acid sites on time has been found. It is found that water promotes molecular sieve dealuminum mainly at the beginning of the reaction, and the action object is unstable non skeleton aluminum. Based on this mechanism of water, fresh catalyst is used for a short time steam aging, and the acid density of the catalyst is reduced by the rapid dealuminum action of water. In order to improve the selectivity and stability of propylene with less water, in order to improve the selectivity and stability of propylene, the influence of the concentration of citric acid, treatment temperature and time on the acid distribution of the catalyst was investigated. Non skeleton aluminum is transformed into skeleton aluminum to increase the acid site of molecular sieve. Based on this mechanism of citric acid, a water vapor aging technology combined with on-line acid supplementation is proposed. The effects of phosphorus content, precursor concentration, temperature, treatment time on phosphorus, aluminum morphology and distribution are investigated. The high temperature environment of on-line phosphorus supplement is found to be the realization of phosphorus and bone. The effect and effect of on-line phosphorus supplementation on the stability of skeleton aluminum were verified by further investigation of the thermal stability of the phosphorus supplementing catalyst. (3) the modification method of catalyst with carbon accumulation as a control method was studied and established. The changes of the morphology of the carbon and the morphology of the high temperature carbon with the temperature and time were investigated. The evolution process of low temperature carbon to high temperature carbon was designed. The charcoal agent prepared at different temperatures, raw materials and time was designed. The modification of carbon deposit on the structure of catalyst and its guiding effect on the two carbon deposition were studied. The modified method of catalyst was put forward with the control of auxiliary water by carbon deposition. By studying the two carbon deposits of high temperature carbon deposited at low temperature. Behavior, and the two Coking Behavior of low temperature charcoal at high temperature, a "carbon cycle" technique of MTP two step process in moving bed was put forward. (4) the growth law of coke and the deactivation law of catalyst in different reaction and regeneration period were studied. By studying the distribution of coke deposited at high and low velocity, it was found that the velocity of high methanol resulted in the shell of the catalyst. The cocharcoal is deactivated, and the low methanol airspeed leads to the inactivation of the inner carbon deposit, showing different inactivation mechanisms. By tracking the diffusion behavior of methanol, toluene, and isopentane in different degrees of carbon accumulation, the carbon accumulation "from inside to outside" growth process is proposed. The carbon accumulation behavior of fresh catalyst and regeneration catalyst is studied by comparison. The competitive effect of the first periodic water and second periodic carbon deposition on the deactivation of the catalyst was revealed. (5) using the water vapor aging agent as the research object, the methanol reaction was investigated in an isothermal fixed bed reactor. The distribution of methanol to the C2-C6 olefin coupling reaction was followed by the methanol air velocity (3-40 (gmethanol/ gcat. H) and reaction. The parallel reaction of methanol, the methylation of olefin methylation, and the competitive relationship between olefin superposition and cracking reaction were studied at temperature (420~500 degrees C). Under low methanol velocity (0.5 ~ 5 gmethanol/ gcat h), propene was used as a promoter for hydrogen transfer and aromatization of olefin, and the formation path of aromatics and propane in MTP reaction was studied. A kinetic model of MTP reaction, which can accurately describe the 9 components of methanol, ethylene, propylene, propane, propane, C4, C5, C6, C7+ and aromatics, is established and the carbon content factor is introduced in the model to consider the deactivation of the catalyst. The model is suitable for predicting MTP reaction or alcohol hydrocarbon co refining MTP reaction at the initial stage. And the composition of the products in different carbon deposition stages.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ221.212;O643.36

【参考文献】