不同处理方法对煤焦上甲烷裂解制氢性能的影响

Effect of different treatments on the performance of coal char for methane cracking to hydrogen

在小型石英管固定床上,考察甲烷在小龙潭(XLT)褐煤焦以及处理煤焦:水洗煤焦、HCl-HF洗煤焦及硝酸洗煤焦上的裂解反应性能。结果表明,XLT煤焦上甲烷的初始转化率为64.7%,水洗煤焦和硝酸洗煤焦上甲烷初始转化率明显提高,分别为78.5%、72.4%,而经HCl-HF处理后,甲烷初始转化率下降到54.1%,煤焦的催化活性降低。随着反应时间的不断增加,甲烷裂解转化率和氢气收率逐渐降低,说明不同煤焦在反应过程中逐渐失活。通过扫描电子显微镜和比表面积测定仪对反应前后不同煤焦进行表征,BET数据表明,甲烷裂解后煤焦的比表面积和微孔容降低,平均孔径增大,分析其原因是反应生成的积炭堵塞煤焦的微孔。SEM结果显示甲烷裂解后,煤焦表面上有明显的积炭生成,最终导致煤焦催化活性逐渐降低。

The cracking reaction of methane on Xiaolongtan(XLT)lignite coal as well as on treated coal chars,including water treated coal char,HCl-HF treated coal char and nitric acid treated coal char were investigated in a small quartz tube fixed bed.The initial conversion of methane on XLT coal char was 64.7%,and the initial conversion of methane on water treated coal char and nitric acid treated coal char were significantly increased to 78.5%and 72.4%,respectively.Whereas the initial conversion of methane on HCl-HF treated coal char decreased to 54.1%,and the catalytic activity of the coal char was reduced.With the increasing reaction time,the methane cracking conversion and hydrogen yield also decreased gradually,indicating that different coal chars were gradually deactivated during the reaction process.The difference of coal chars before and after the reaction were characterized by SEM and specific surface area tester.The BET data showed that the specific surface area and microporous capacity of coal chars decreased and the average pore diameter increased after methane cracking,which was attributed to the reaction-generated carbon deposits clogging the micropores of the coal char.The SEM results showed that there was a significant generation of carbon deposits on the surface of the coal char after methane cracking,which ultimately led to the gradual decrease in the catalytic activity of the coal chars.