微介孔Ni/ZSM-5分子筛对甲苯催化重整的影响

文章通过水热法结合使用淀粉模板剂和碱处理合成了3种微介孔ZSM-5分子筛,并以Ni为活性组分制备了一系列Ni/ZSM-5催化剂用于甲苯(生物质气化焦油模型化合物)水蒸气催化重整实验。采用N2吸附-脱附、NH3-TPD和XRD对分子筛和催化剂进行表征,研究了催化剂酸性和孔结构对甲苯催化重整效果的影响,并深入分析了介孔体积以及孔径分布与碳转化率的相关性。研究结果表明:合成的ZSM-5分子筛具有较大的介孔体积,主要分布在2~4,4~8 nm和16~45 nm,其中2~4 nm的介孔体积与甲苯碳转化率有很好的相关性(R²>0.99);模板法合成的ZSM-5(ST)具有最大的2~4 nm介孔体积,相应的碳转化率接近100%;碱处理制得的ZSM-5(AT)的酸性增强,4~8 nm孔容大幅增加,但碳转化率仅有约70%;模板法改性可提升镍基催化剂的性能。

Effect of micro-mesoporous Ni/ZSM-5 zeolites on catalytic reforming of toluene

In this paper,three kinds of micro-mesoporous ZSM-5 molecular sieves were synthesized by hydrothermal method combining starch template and alkali treatment,and a series of Ni/ZSM-5 catalysts were prepared with Ni as the active component for catalytic steam reforming of toluene as a model compound of biomass gasification tar.The molecular sieves and catalysts were characterized by N2 adsorption-desorption,NH3-TPD and XRD.The effects of acidity and pore structure of the catalyst on the catalytic reforming of toluene were investigated.The correlations of the mesoporous volume and pore size distribution with the carbon conversion of toluene were deeply analyzed.The results show that the synthesized ZSM-5 molecular sieves have larger mesoporous volumes and their mesoporous sizes are mainly distributed in the ranges of 2~4,4~8 nm and 16-45 nm.Among them,the mesoporous volume of 2~4 nm has a good correlation with the carbon conversion of toluene(R²>0.99).The ZSM-5(ST)synthesized by the template method has the largest mesoporous volume of 2~4 nm,and its carbon conversion is nearly 100%.However,the carbon conversion of the ZSM-5(AT)after further alkali treatment is only about 70%in spite of stronger acidity and greatly increasing mesoporous volume between 4~8 nm.It is proved that template modification can improve the performance of the Ni-based catalyst for toluene reforming.