异丙苯裂化催化剂ASTRA-MB1积炭失活机理

MECHANISM OF ASTRA-MB1 CATALYST DEACTIVATION FOR CUMENE CRACKING DUE TO COKING

通常催化剂的积炭失活由两种情况引起 :活性位被覆盖和孔被堵塞。在热重分析仪上以异丙苯裂化反应为模型反应 ,采用CCAP(恒碳Arrhenius关系图 )技术探讨了裂化催化剂ASTRA MB1的积炭失活机理 ,得到了反应速率常数和有效扩散系数随积炭量的变化规律。结果表明 ,当反应温度低于 5 73K时 ,孔的堵塞对催化剂的活性影响较大 ,当反应温度高于 6 2 3K时 ,积炭主要发生在催化剂的外表面 ,其上的活性位被覆盖是造成催化剂失活的主要原因。理论上 ,通过降低催化剂粒径以增加其外表面的活性位数目 ,是提高催化剂利用率的有效途径。

Deactivation of catalyst due to coking is known to occur by two reasons: active site suppression and pore blockage. This work is to investigate the deactivation of cracking catalyst during coking by using CCAP(Constant coke Arrhenius plots) technique. Cumene cracking on ASTRA MB1 zeolite was chosen as a model reaction. The thermogravimetric analyzer(TGA) was used as a continuous flow reactor to monitor coke levels. The intrinsic reaction rate constant and the effective diffusivity of cumene were obtained at different coke levels and temperatures. The experimental results showed that pore blockage was important only at temperatures lower than 573 K and low coke levels; at temperatures higher than 623 K, the coke reaction occurred mainly on outer surface of the catalyst and site suppression occurred at all levels. Theoretically, to decrease the particle size of the catalyst so as to increase the number of active sites on outer surface of the catalyst is more important and effective.