半焦炭催化甲烷裂解及动力学特性

Methane decomposition over carbonaceous catalyst and its kinetic characteristics

在平推流反应器上,考察了非催化和半焦炭催化条件下甲烷裂解。利用气相色谱分析研究了甲烷裂解的规律。结果表明,半焦对甲烷裂解具有明显的催化作用,不同种类的炭催化剂表现出相似的催化活性。半焦炭催化剂条件下,甲烷裂解转化率同时受两方面的影响:一方面甲烷裂解产生的积炭沉积在半焦表面及孔内,覆盖大部分的活性位,同时堵塞半焦内的孔道阻碍甲烷向半焦孔内扩散,使甲烷的裂解率降低;另一方面甲烷裂解生成的新物种反过来又对甲烷的裂解起催化作用,促进甲烷裂解。研究还表明,半焦中的灰分对甲烷裂解没有明显的作用,甲烷裂解主要受温度控制。采用简单的平推流模型对甲烷热分解动力学参数进行了计算,计算得到甲烷非催化和半焦催化裂解的表观活化能分别为154.02kJ/mol和82.06kJ/mol。

Methane decomposition is performed over different carbonaceous materials in a quartz tubular reactor with temperatures ranging from 900 to 1 100℃.The gas composition is detected by gas chromatograph with FPD and PID detector.All the carbon catalysts show similar deactivation pattern.Mass transport effect in the catalyst particles is observed and the pore mouth blocking appears to occur noticeably especially in large particles.It can be found that the methane decomposition reaction over carbon catalysts is controlled by two simultaneous processes.The methane decomposition rate decreases is due to the blocking of catalytic active sites by the carbon deposition produced by methane decomposition,on the other hand,the methane decomposition rate increases is due to the formation of catalytically active species by methane decomposition.The methane decomposition kinetic characteristics are investigated over blank and carbonaceous catalyst,the activation energies are 154.02 kJ/mol and 82.06 kJ/mol,respectively.Ashes in the activated carbons have little effect on the catalytic activity.