Abstract:

Hydrocracking is an important process for directional conversion of the polycyclic aromatic hydrocarbons (PAHs) in catalytic diesel into high value-added monocyclic aromatic compounds, which shows the features of simpler process, energy conservation and lower cost than thermal cracking process. This article reviews research progress on bifunctional catalysts for the hydrocracking reactions of PAHs to high-value chemicals (BTX, benzene, toluene and xylene). The effects of active metal components and acidic supports on the catalytic performance are discussed first. Transition metal sulfides, phosphides, carbides and nitrides catalysts exhibit high hydrogenation activity similar to noble metals. The combination of noble and transition metals or the use of transition bimetals not only exhibit superior hydrogenation activity and selectivity, but also saves the cost. The hierarchical silica-aluminum zeolites, modified mesoporous zeolites and the micro-mesoporous composites of acidic zeolites and silica are considered as the highly concerned support for hydrocracking catalysts as they possess acidic sites for the skeleton cracking of reactant molecules, and pore structure properties facilitating the diffusion and mass transfer. The effects of metal-acid equilibrium and synergism on product selectivity are also discussed, and the metal-acid sites at near nanoscale possess optimal bifunctional synergism. Finally, the influence of different catalyst loading methods on metal particle size, dispersion and catalyst structure and performance are explored. The highly dispersed metal nanoparticles are crucial to the preparation of efficient hydrocracking catalysts and the selectivity of target products.

Key words: bifunctional catalyst, active metal, acid support, polycyclic aromatic hydrocarbons, hydrocracking

摘要：

加氢裂化是将催化柴油中的多环芳烃定向转化为高附加值的单环芳烃化合物的重要工艺，与热裂解相比工艺简单，节能降耗并减少了加工成本。本文综述了多环芳烃加氢裂化制高值化学品（BTX，即苯、甲苯和二甲苯）反应的双功能催化剂的研究进展。首先讨论了活性金属组分和酸性载体的选择对催化性能的影响。过渡金属硫化物、磷化物、碳化物和氮化物催化剂具有类似贵金属的高效加氢活性，贵金属与过渡金属结合或使用过渡双金属能够节省成本，且表现出优异的催化加氢活性和选择性。多级孔硅铝分子筛、改性介孔分子筛和酸性沸石与氧化物的复合载体具有促进反应分子骨架裂解的酸性位点，以及利于扩散传质的孔结构性质，是加氢裂化催化剂备受关注的载体。同时讨论了金属-酸平衡和协同作用对产物选择性的影响，纳米级接近度的金属-酸位点具有最佳的双功能协同作用。最后探讨了不同催化剂负载方法对金属颗粒尺寸、分散度和催化剂结构及性能的影响，将金属纳米颗粒高度分散在载体上是制备高效加氢裂化催化剂和提高目标产物选择性的关键。

关键词: 双功能催化剂, 活性金属, 酸性载体, 多环芳烃, 加氢裂化