苯丙烯烷基化改性Beta沸石催化剂积炭的研究

【作者】 卞俊杰；

【导师】 刘靖；

【作者基本信息】 大连理工大学 ， 催化化学与工程， 2002， 硕士

【摘要】 本课题组研制开发的改性Beta沸石催化剂BPA-9711在苯丙烯烷基化反应中具有很高的活性、选择性。中试条件下稳定运转8000小时，催化剂因积炭失活。 本论文采用热重分析TG、程序升温烧炭TPO、¹³C CP-MAS NMR核磁共振、傅立叶变换红外光谱FT-IR、气相色谱-质谱联用技术GC-MS和N₂物理吸附等多种表征手段和研究方法对BPA-9711催化剂上积炭的组成、积炭的性质和积炭在催化剂上的分布进行研究。同时对新一代改性Beta沸石催化剂BPA-99H在苯和二异丙苯烷基转移反应中的积炭进行了初步的研究。 结果表明BPA-9711催化剂中试运转8000小时后的BPA-8000上的积炭主要是C／H＜1的富氢炭，由“易除炭”和“难除炭”两部分组成，前者氮气吹扫或苯冲洗即可去除，后者与催化剂失活的关系很大，须在含氧气氛中才能彻底烧除。随着反应时间的延长，催化剂上沉积的多异丙基苯进一步发生氢转移、缩合、芳构化等反应生成高C／H比、大体积的（烷基）稠环芳烃，造成沸石孔道阻塞，导致催化剂失活。失活催化剂BPA-8000上的积炭绝大部分沉积在沸石孔道内，阻碍反应物接近催化活性中心。BPA-99H催化剂上的积炭主要是沉积在沸石孔道内的多烷基苯和萘，此类积炭若进一步发生氢转移、缩合、芳构化生成稠环芳烃则会造成催化剂失活。更多还原

【Abstract】 Modified zeolite Beta catalyst, synthesized in our group, named BPA-9711, exhibits high activity, selectivity and stability under the optimal operating conditions for benzene alkylation with propene to produce cumene in pilot plant. The catalyst was deactivated after 8000 hours’ run due to coke deposition.In this dissertation, the nature of the carbonaceous deposit (coke) on BPA-9711 was studied in details. The amount and characters of the coke was determined by Thermal Gravimetric (TO) analysis and Temperature Programmed Oxidation (TPO), the ingredients of the coke was distinguished by 13C CP-MAS NMR, FT-IR and GC-MS. Solvent extraction and N2 physical adsorption were conducted to gain a clear understanding of the effect of coking on pore structure of the catalyst. It is clear that there are two types of deposit, soft coke and hard coke. The former, which can be removed either by benzene flush at the reaction temperature and or by oxidation, contributes a little effort to deactivation, while the latter, which can only be minimized by oxidation in high temperature, play a dominant role in the catalyst deactivation. The deposit on the decayed BPA-9711 consists mainly of multi-isopropyl benzene, alkyl-tetrahydronaphthalene, and a little amount of organic matters with high molecular weight. It is deduced that (multi-)isopropyl benzene underwent hydrogen transfer, condensation, and cyclation to form polynuclear aromatics which prevents reactants to access intracrystal active sites, and blocks products to diffuse outside. The deposit is located in pores and channels of the crystal instead of on the surface. The coke on BPA-99H, new catalyst for trans-alkylation was also investigated.更多还原