沥青质裂解反应选择性分析

Analysis for the Selectivity of Asphaltene Cracking Reactions

在703K下,考察了1种正戊烷不溶的沥青质的热裂解、临氢热裂解和NiMo/γ-Al2O3存在时的临氢催化裂解反应。结果表明,在相同的反应物转化率水平下,3种裂解反应按液体产物选择性从大到小的排列顺序为临氢催化裂解、临氢热裂解、热裂解反应,而按焦炭的选择性的排列顺序则相反。在热裂解反应中,沥青质中大量的硫被转化生成高硫焦炭;在临氢热裂解反应中,氢气分子对高硫焦炭的生成只起到有限的抑制作用;在临氢催化裂解反应中,催化剂充分激活氢气分子,使其有效地对沥青质及中间产物发生"加氢"(氢化)作用,显著地抑制了焦炭的生成,提高了液体产物的稳定性、选择性和品质(低相对分子质量和低硫含量)。

A pentane-insoluble asphaltene was processed by thermal cracking,thermal hydrocracking and catalytic hydrocracking over NiMo/γ-Al2O3 at 703 K,respectively.Analysis of selectivity showed that at the same level of asphaltene conversion and according to the selectivity of liquid products from high to low the three cracking reactions were in the order of catalytic hydrocracking,thermal hydrocracking,thermal cracking,while according to the selectivity of coke from high to low,the three cracking reactions were in the opposite order.In thermal cracking,a large amount of sulfur converted from the feed into coke,and in thermal hydrocracking,molecular hydrogen played a certain degree role in inhibiting formation of coke with high sulfur content,and in catalytic hydrocracking the catalyst effectively activated hydrogen molecules to hydrogenate the reactant and middle products,leading to a significant reduction of coke formation and remarkable improvement of liquid stability,selectivity and quality（lower average relative molecular mass and sulfur content）.