Preparation of encapsulated Ni-based catalyst and its performance in-situ upgrading of coal pyrolysis tar
In order to realize the in-situ upgrading process of coal pyrolysis tar,Ni-based catalysts were prepared by in-situ encapsula-tion method and impregnation method respectively,and the effects of these two catalysts on the in-situ catalytic upgrading of pyrolysis tar were investigated.Compared with no catalyst,Ni/HZSM-5 with Ni content of 2％can increase the yield of light components in tar from 5.8％to 6.9％,while Ni@HZSM-5 with the same Ni content can increase the yield of light tar to 7.6％.The influence of Ni/HZSM-5 and Ni@HZSM-5 catalysts on the yield of each component of tar was further analyzed.The results shows that both catalysts significantly re-duces the heavy components in tar,and the asphaltene yield decreases from 5.4％to 1.3％and 2.0％,respectively.However,compared with Ni/HZSM-5,Ni@HZSM-5 increases the yield of light oil and phenol oil by 38.5％and 25.5％,respectively,and naphthalene oil also increases to a certain extent,indicating that the Ni based catalyst prepared by encapsulation method can maximize the retention of light components in tar.This is because in Ni/HZSM-5,both tar cracking and activation of hydrogen-rich components in pyrolysis gas oc-cur on the Ni surface,which promotes the activation of hydrogen-rich gas and also causes excessive tar cracking.The Ni in Ni@HZSM-5 is mainly distributed in the pore of molecular sieve.Its excellent shape selection catalytic performance enables hydrogen-rich gas mole-cules to enter into the HZSM-5 and contact with Ni,producing hydrogen-rich free radicals such as·H and·CHx,while large mole-cules in tar cannot enter into the pore of molecular sieve.The cracking can only occur on the acid site on the outer surface of HZSM-5,avoiding the participation of metal Ni in tar cracking,so as to regulate the amount of tar cracking fragments and hydrogen-rich free radi-cals,so as to achieve the balance of hydrogen and carbon in the system.As a result,the excessive cracking of tar fragments is effectively avoided and the yield of light tar is improved.
coal pyrolysiscatalytic upgrading of tarencapsulated catalystHZSM-5 molecular sieve
万方数据
维普
