Z/M对RFCC催化剂反应性能的影响

Effect of Z/M on catalytic performance of RFCC catalyst

以稀土超稳Y型分子筛和拟薄水铝石为主要原料制备了重油催化裂化(RFCC)模型催化剂,通过N 2物理吸附和高级裂化评价装置研究了水热减活RFCC模型催化剂中Y型分子筛与基质比表面积之比(Z/M)及其对催化裂化反应性能的影响。结果表明,拟薄水铝石含量越高,Y型分子筛抵御高温水热破坏的能力越差,Z/M越小。拟薄水铝石质量分数为30%时,水热减活后分子筛比表面积仅为减活前的28.3%,Z/M仅为0.8。拟薄水铝石含量不仅影响催化剂的水热稳定性,还影响催化剂的形貌。拟薄水铝石含量越高,催化剂微球形貌规整性越差,当其质量分数为30%时,催化剂微球表面不仅产生了大量的孔洞,还出现了许多裂纹。随着模型催化剂Z/M下降,目标产物液化石油气和汽油产率之和逐渐降低,轻循环油产率升高,焦炭选择性变差。

A model catalyst for heavy oil catalytic cracking(RFCC)is prepared from rare earth super stable Y zeolite and pseudo-boehmite.The ratio of specific surface area of Y zeolite to substrate(Z/M)in hydrothermal RFCC model catalyst and its effect on catalytic cracking performance are studied by N 2 physical adsorption and advanced cracking evaluation equipment.The results show that the higher the content of pseudo-boehmite in RFCC model catalyst,the worse the ability of zeolite Y to resist high-temperature hydrothermal damage,and the Z/M ratio gets smaller.When the pseudo-boehmite mass fraction in the model catalyst reaches 30%,the specific surface area retention of zeolite Y is as low as 28.3%,and the Z/M ratio is only 0.8.The pseudo-boehmite content not only affects the hydrothermal stability of catalyst but also the morphology of catalyst.The higher the pseudo-boehmite content,the worse the morphology of catalyst microspheres.When the mass content of pseudo-boehmite is 30%,there were not only a lot of holes but also many cracks on the surface of catalyst microspheres.The evaluation results of RFCC model catalyst for residue catalytic cracking show that with the decrease of model catalyst Z/M ratio,the total yeilds of target liquefied petroleum gas(LPG)and gasoline gradually decrease,the light cycle oil yield increases,and the coke selectivity becomes poor.