原料油中氮、硫体积分数及反应压力对加氢裂化催化剂积炭的影响

Effects of nitrogen or sulphide content and reaction pressure on coke deposited on hydrocracking catalyst

在高压连续流动微型反应器上对加氢裂化催化剂进行催速老化实验,用元素分析、傅里叶变换红外光谱(FTIR)、X-光电子能谱(XPS)、热重 /微商热重(TG/DTG)等手段考察了不同体积分数的噻吩、吡啶和操作压力对催化剂积炭行为的影响。结果发现:原料中吡啶和噻吩体积分数分别高于 0. 1%和 0. 6%时,会导致催化剂积炭明显增加。含吡啶的原料在进行加氢裂化时生成的积炭,主要集中在微孔( <6nm)中,并会削弱催化剂的酸性中心,尤其是强酸中心。含噻吩原料加氢裂化生成的积炭,存在于不同孔径的孔中,在催化剂表面形成少量机械孔。原料中噻吩体积分数低于 0. 6%时,噻吩中的硫可以提高催化剂的硫化度使积炭减缓。相同体积分数的吡啶对催化剂积炭的贡献大于噻吩,催化剂比表面积降低更多。提高压力可以显著地降低催化剂的积炭量,减缓比表面的降低,减少酸中心数目的损失,导致微孔( <6nm)中积炭增多,积炭中石墨型积炭的相对比例增大。

The coke deposition of various contents of nitrogen (sulphide) in toluene under different reaction pressures on hydrocracking catalyst has been obtained using accelerated aging experiment. Coke type and amount, acid strength distribution, pore structure, and dispersion of active metal of catalyst were measured by elemental analysis, FTIR, physical adsorption, XPS, and TG/DTG. The results showed that the amount of coke increases significantly when the content of pyridine or thiophene is higher than 0.1% or 0.6% in toluene. The coke deposited due to pyridine accumulated mainly in small pores ( less than or equal 6 nm), and it decreased the amount of acid center especially strong acid center. The coke deposited due to thiophene impenetrated into all the pores and some of them could form mechanical pore on catalyst surface. When the content of thiophene was higher than 0.6% in toluene, thiophene could enhance the active-metal sulphidation and weaken the coke production. Higher reaction pressure could make coke deposited less abruptly, decrease the loss of acid center, but result in the ratio of pseudo-graphite structure coke increasing relatively.