摘要
本文用积分固定床反应器对异丁烯-甲醛一步缩合制异戊二烯用Cr-P/SiO_2催化剂的失活动力学进行了研究,测定了在反应温度为260～340℃,常压及不同反应物组成时的反应速度。建立了失活动力学方程,估算出反应级数、活化能、以及失活级数和失活因子。所得失活动力学方程式为: r=1.07x10^(-6)exp(-35.2/RT)·P_1~0.9·P_2~1.5·a a=0.47+0.53exp(-4.83×10^(-4)t) -da/dt=2.56×10^(-4)exp(-4.83×10^(-4)t) 从上述方程式推测,在Cr-P/SiO_2催化剂上可能存在两种活性中心,一种是既能进行缩合反应同时又伴随积炭的中心,另一种中心则只进行缩合反应。催化剂的失活机理为反应物没有内扩散阻力的平行—串联失活,反应物与产物均能在催化剂表面形成焦炭,覆盖活性中心或堵塞洞口而导致失活。经烧炭催化剂活性可获得恢复。
The deactivation kinetics on the Cr-P/SiO2 catalyst for gas-phase condensation between formaldehyae and isobutylene into isoprene was investigated in an integral fix- bed reactor.The kinetic data were measured under atmospheric pressure and at 260-340℃. The reaction order, activation energy, deactive order and deactive factor were evaluated. The results obtained were as follows:
1.The reaction rate equation and the deactivation rate equation: r=1.07×10-8exp( -35.2/RT )P10·9·P21·5·a
a = 0.47 + 0.53exp ( - 4.83 · 10-4t )
-(da)/(dt)= 2.56· 10-4exp( -4.83·10-4t )
2.Based on the experimental results, it is possible that there are two active sites on the surface of the catalyst. One is effective not only for condensation but also for coking, the other is only for condensation.
3.It is easily to be seen from deactivatation equation that this type of catalyst decay is dependent on the time which the catalyst spends in reaction condition and is unaffected by the concentration of reactants in the system. As well as the deactive order in the deactivation equation is 1. Hence we suggested that the deactivation mechanism of this catalyst is parallel and series deactivation without pore diffusion resistance.
出处
《分子催化》
EI
CAS
CSCD
1990年第1期52-59,共8页
Journal of Molecular Catalysis(China)
基金
国家自然科学基金
