HZSM-5分子筛改性及其在甲醇制汽油中催化性能研究

发布时间：2018-02-27 05:06

本文关键词： HZSM-5 MTG 汽油选择性芳烃含量失活再生　出处：《天津大学》2015年硕士论文　论文类型：学位论文

【摘要】：汽油是重要的能源消耗品,2014年我国汽油表观消费量超过1亿吨,其中绝大部分以石油为原料通过石化法获得。甲醇制汽油(MTG)是对石化法制汽油的重要补充,MTG工艺核心为,合成性能优良的HZSM-5分子筛,并对其进行改性,使其表现较高的催化活性和较长的催化寿命,同时提高甲醇转化率、汽油选择性。采用两段控温结晶法(无胺法)制备出粒径约为3μm的微米型M-HZSM-5,成品晶型规整,轮廓清晰,结晶度高;采用多级晶种诱导法(无胺法)制备出粒径约为500 nm的纳米型N-HZSM-5,成品晶型规整,结晶度高,存在团聚现象。纳米型HZSM-5较微米型HZSM-5拥有更高的比表面积、介孔含量及更强的酸性,在MTG反应中,表现出更好的催化性能,但存在催化寿命不高、汽油选择性低、汽油中芳烃含量超标等问题,需对其进行改性。用Ag和Zn对N-HZSM-5负载改性,负载量为4%(wt%),再用500°C水蒸气二次改性,与N-HZSM-5比较,AgH2O/N-HZSM-5和ZnH2O/N-HZSM-5催化寿命分别增加41.2%和52.9%,反应6 h,汽油选择性分别增加19.1%和15.5%,负载Ag或Zn均促进芳构化进程,汽油中芳烃含量分别为61.9%和55.4%,远超国V汽油标准,需调和后使用。将适用于甲醇制烯烃的负载P型HZSM-5改性为优良的MTG催化剂PH2O/N-HZSM-5,P负载量为0.8%(wt%),水蒸气二次改性温度为500°C,充分发挥L酸与B酸协同作用,与N-HZSM-5比较,改性后催化寿命增加64.7%,反应6 h,汽油选择性增加16%,汽油中芳烃含量降至39%,符合国V汽油标准,是较理想的MTG催化剂。失活再生分析,四段升温氧化积碳较完全,失活分子筛基本恢复催化活性。经高温水蒸气二次处理后,抗积碳失活能力明显提升。负载Ag或Zn均提高HZSM-5水热稳定性,减少失活-再生过程中的不可逆失活,增加循环使用次数。PH2O/N-HZSM-5抗积碳失活能力最强,失活-再生过程对分子筛造成的不可逆失活对PH2O/N-HZSM-5影响较大,限制其循环使用次数。
[Abstract]:Gasoline is an important energy consumable. In 2014, the apparent consumption of gasoline in China exceeded 100 million tons, most of which were obtained from petroleum through petrochemical process. The HZSM-5 molecular sieve with excellent performance was synthesized and modified, which showed higher catalytic activity and longer catalytic life, and increased methanol conversion at the same time. Gasoline selectivity. Micrometer M-HZSM-5 with grain size of about 3 渭 m was prepared by two-stage temperature-controlled crystallization (amine-free method). The finished product was characterized by regular crystal shape, clear outline and high crystallinity. Nanocrystalline N-HZSM-5 with a diameter of about 500nm was prepared by multistage seed induction (amine-free method). The finished product has regular crystal shape, high crystallinity and agglomeration. Compared with micron HZSM-5, nano-type HZSM-5 has higher specific surface area, mesoporous content and stronger acidity. In the MTG reaction, the catalytic performance of N-HZSM-5 is better, but it is necessary to modify N-HZSM-5 supported on Ag and Zn because of its low catalytic life, low selectivity to gasoline and the content of aromatics in gasoline exceeding the standard. The catalyst life of AgH _ 2O _ 3 / N-HZSM-5 and ZnH2O/N-HZSM-5 were increased by 41.2% and 52.9, respectively, and the selectivity of gasoline increased by 19.1% and 15.5in 6 h, respectively, and the loading of Ag or Zn promoted the process of aromatization, compared with N-HZSM-5 and N-HZSM-5, the catalytic life of AgH _ 2O and N-HZSM-5 was increased by 41.2% and 52.9, respectively, and the selectivity of gasoline was increased by 19.1% and 15.5 for 6 h. The aromatics content in gasoline is 61.9% and 55.4 respectively, which is far above the national V gasoline standard. The supported P type HZSM-5, which is suitable for methanol alkenes, is modified into an excellent MTG catalyst, PH2O-N-HZSM-5P, with a loading amount of 0.8W / T and a water vapor secondary modification temperature of 500 掳C. The synergistic effect of L acid and B acid is brought into full play and compared with N-HZSM-5. After modification, the catalytic life was increased by 64.7%, reaction time was 6 h, gasoline selectivity was increased by 16%, and the aromatics content in gasoline decreased to 39%, which was in line with the national V gasoline standard and was an ideal MTG catalyst. After secondary treatment of high temperature water vapor, the ability of resisting carbon deposition deactivation was improved obviously. The thermal stability of HZSM-5 was improved by loading Ag or Zn, and the irreversible deactivation in the process of deactivation and regeneration was reduced. The increase of recycling times. PH2O-N-HZSM-5 has the strongest ability to resist carbon deposition inactivation, and the irreversible inactivation caused by deactivation and regeneration process has a great influence on PH2O/N-HZSM-5, which limits the number of cycles.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE66

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