【作者】 尚勤杰；

【导师】 赵崇军； 宁春利；

【作者基本信息】 华东理工大学 ， 材料工程， 2012， 硕士

【摘要】 乙烯和丙烯等低碳烯烃是现代工业发展不可或缺的基础原料,目前其主要来源于石油炼制工业。近年来的石油危机和国际政治经济的不稳定,使得寻求非石油路线生产低碳烯烃的工艺成为必要。甲醇可以通过煤、天然气或者生物质原料制取,来源广泛,生产技术成熟,因此以甲醇为中间产品生产低碳烯烃的技术被视为实现非石油路线生产低碳烯烃的关键环节。作为世界上最大的煤炭生产国和消费国,由煤经甲醇制低碳烯烃的技术在我国更具有非比寻常的意义。甲醇制烯烃(MTO)技术的核心环节就是催化剂的研究和开发。由于具有弱酸性、小孔等特性,SAPO-34分子筛在MTO反应中表现出很高的活性和低碳烯烃(C2-C4烯烃)选择性,对该催化剂的进一步研究和工艺的优化无疑有利于其更好地工业化应用。本文围绕SAPO-34的水热合成以及改性展开,重点从MTO反应工艺、水热合成条件、水热合成配方、催化剂的金属改性等几个方面进行了探索和研究,主要工作结果包括以下三个方面：(1)通过对MTO反应工艺进行探索和优化,研究了MTO反应的动力学和热力学特征,并确定了较适宜的反应工艺条件：反应原料为50%的甲醇水溶液,反应温度为400℃,甲醇液时空速1.5 h-1,常压反应体系。(2)采用水热法合成SAPO-34:以吗啡啉为模板剂,考察了水热合成条件和配方,合成出了纯相的SAPO-34分子筛。较适宜的合成条件为：晶化温度为180～200℃,晶化时间为24 h-48 h,动态晶化。原料成份比为：SiO2:Al2O3:P2O5:MOR:H2O=1.0:1.0:(0.8～1.2)：(2.0～3.0)：(30～90)。在单模板剂的基础上,采用三乙胺-吗啡啉双模板剂合成的催化剂比单模板剂合成的催化剂具有更好的MTO催化活性,TEA/MOR=3:1时合成的催化剂活性最好,乙烯选择性为48%,总低碳烯烃选择性达到87.9%。(3)研究了金属改性对于催化剂性能的影响。分别考察了多种金属改性的SAPO-34催化剂及其MTO反应催化性能。发现通过金属改性,可以有效地缩短反应诱导期,其中Mn、Ce、La改性的催化剂在缩短反应诱导期的同时,低碳烯烃选择性也得到提高；La、Ce改性SAPO-34在金属负载量为2%时具有最佳的低碳烯烃选择性。不同改性方法制备的催化剂,其组成、酸性特征以及金属负载量都有所区别。其中,过量浸渍法改性的SAPO-34分子筛催化效果最好,乙烯选择性比未改性前提高了10%左右；离子交换法次之,但其诱导期最短；浸渍法改性相对前两者影响最小。更多还原

【Abstract】 The light olefins, especially ethylene and propylene, are indispensable basic raw materials for modern chemical industry. They are generally produced by the crude oil cracking process, which is greatly dependent on the petroleum resources. So people are searching for methods to replace the conventional oil route to get light olefins. One of these is the methanol-to-olefin process (MTO), because methanol can be obtained from multiple sources, such as coal, natural gas and biomass, and by using methanol as starting material, olefins can be produced without the involvement of oil. It is of great significance to develop the MTO process, especially for China which is abundant of coal and lack of oil. And China has made considerable progress in the research and industrialization of MTO technology.The key technology of MTO process is the research and development of catalyst, which is demanded to give high methanol conversion and high light olefin selectivity. Due to its weak acidity and small pore, the SAPO-34 molecular sieve is supposed to be one of the most excellent catalysts.In this dissertation, the MTO reaction conditions including reaction temperature, pressure, methanol concentration and liquid hourly space velocity (LHSV) were firstly investigated, and the optimal reaction condition was as the follows:50% aqueous methanol as feedstock,400℃,1.5 h-1 LHSV, and atmospheric pressure.SAPO-34 molecular sieve was synthesized by hydro thermal method and the synthetic conditions as well as the gel compositions are studied. Pure SAPO-34 crystals can be synthesized as the following conditions:crystallized at 80～200℃for 24 h-48 h under dynamic condition. The suitable gel composition was as follows:SiO2:Al2O3:P2O5: Morpholine:H2O=1.0:1.0:(0.8～1.2):(2.0～3.0):(30-90). The as synthesized SAPO-34 showed excellent catalytic activity in MTO reaction.The multiple template hydrothermal systems were studied by using triethylamine (TEA) and morpholine (MOR) as template in the synthesis of SAPO-34. Catalysts synthesized by bi-template showed higher catalytic activity than that synthesized by single template. With TEA/MOR=3:1, selectivity to ethylene reached 48%, and the overall selectivity of light olefins reached 87.9%.Metal modification of SAPO-34 was also studied. The effect of different metals was compared in large scope including Fe, Mn, La, Ce, Zn, Co and so on. It turned out that the Mn, Ce and La modified SAPO-34 exhibited high selectivity to light olefins. The influence of modification methods was also investigated. And as a result, the wet impregnation method presents better catalytic performance than incipient-wetness impregnation method and ion exchange method. Selectivity to ethylene of catalyst synthesized by wet impregnation method had increased 10% compared with unmodified catalyst. And catalyst modified by ion exchange method had shorter induction period in the MTO process.更多还原