Cu/Si载氧体氧解耦反应动力学研究

通过机械混合法制备了Cu/Si载氧体并进行了表征,利用热重技术研究了5,10,15和20℃·min~(-1)的升温速率下载氧体的氧解耦反应特性,并采用Coats-Redfern和Starink两种方法进行了动力学分析.载氧体物相组成主要包括CuO和SiO_2,制备过程中Cu-Si的复合化合物未形成;颗粒中CuO和SiO_2交错分布,SiO_2的添加能有效抑制铜氧化物晶粒的长大,避免烧结团聚现象的发生;氧解耦反应达到起始反应温度后,始终维持较高的反应速率直至反应完成;随升温速率的增加,载氧体氧解耦反应起始、终止温度都往高温方向移动,最大反应速率数值逐渐增大.两种方法确定的反应机理函数相同,均为成核和核增长模型R3;Starink法求得的活化能较Coats-Redfern法数值偏大.

Oxygen uncoupling kinetics for Cu/Si oxygen carriers

In this work, Cu/Si oxygen carrier was prepared by mechanical mixing. Characterization measurements were used to characterize the prepared oxygen carrier. TG experiments were performed in STA409PC thermal analyzer with heating rates of 5, 10, 15 and 20 ℃·min-1 to investigate the reduction process. Reduction kinetics was determined by Coats-Redfern and Starink methods. XRD pattern showed that the main phases in oxygen carrier particles are CuO and SiO2 . SEM images showed that CuO and SiO2 are staggered. Adding SiO2 can inhibit the grain growth of copper oxides and agglomeration. TG results showed that with the increasing of heating rates the starting and ending temperatures as well as the peaks of DTG curves of the oxygen uncoupling reaction shift to high values. The oxygen uncoupling rate keeps in high levels when temperatures are higher than the starting temperatures. The oxygen uncoupling mechanism functions determined by the two methods are the same. Both of them is the nucleation and nuclear growth model R3 . The values of Eα calculated by Starink are bigger than that calculated by Coats-Redfern.