【摘要】 在常压、反应温度800—900℃和水碳比为1.5—1.6的条件下,分别用细粒度(0.045—0.047毫米)和工业粒度的低活性S-4镍催化剂在积分反应器和内循环无梯度反应器中,研究了甲烷水蒸汽反应的动力学。实验结果表明,该反应体系中的水煤气反应没有达到平衡,利用基本上不受扩散影响的细粒度催化剂所进行的实验,获得甲烷水蒸汽反应的速率表达(8)。其产物分布用(4)式进行关联。 对工业粒度催化剂,得到甲烷水蒸汽反应的速率表达式(10)。实验数据表明,工业粒度催化剂的效率因子或表面利用率随甲烷转化率的升高而降低。根据(8)式和(10)式可推算出,在850℃时催化剂的平均有效作用层厚度仅0.048毫米。更多还原

【Abstract】 The kinetics of methane steam reforming over a low activity catalyst was studied at 800- 900℃, H2O/CH4=1.5 and 1.5-1.6 atm in an integral and an internal recycle gradientless reactor respectively. Experimental data obtained indicate that the water gas shift reaction in the methane steam reforming is not in equilibrium, and the rate expression of methane consumption on a fine powdered (0.045mm) catalyst with negligible diffusion effects was found to be:The activation energy for expression (a) is 30.1 Kcal/mol.An empirical correlation for the product distribution was found as follows:where u is the percentage of CO2 in converted methane, x is the methane conversion and the values of a and b are linear with the temperature T(℃). On the other hand, the rate expression of methane consumption for an uncrushed commercial catalyst pellet (16×12mm, cylindrical) on which the reaction rate is controlled by internal diffusion was found to be:The power order of the partial pressure of methane is consistent with that of the theoretical relationship:where na is the reaction order controlled by internal diffusion effect and nt is the intrinsic reaction order.The results show that the effectiveness factor of uncrushed commercial catalyst decreases with the increase of methane conversion, and the average reaction boundary depth is only about 0.048mm at 1.5-1.6 atm, 850℃ and H2O/CH4=1.5. The value corresponds to that of the catalyst pellet size given in the previous paper, on which internal diffusion effect is negligible.更多还原