开放性多级孔氧化铝的合成及其在渣油加氢脱金属反应中的应用

Because of the complexity of heavy oil feed-stocks, there are stricter requirements for the performance of residue demetallization (HDM) catalysts and their corresponding carriers. Traditional alumina with inkbottle-like pores cannot meet the requirements of accommodating metal sulfide and coke deposition and fail to adapt well with the effective diffusion and reaction of the macromolecules of heavy oil. To adapt to the characteristics of stepwise diffusion and reaction of heavy oil to the catalyst, a series of hierarchically organized bird-nest-like alumina with open channels are synthesized via hydrothermal synthesis without the assistance of surfactants. In this structure, the macropores consisted of hollow microspheres and the mesoporous consisted of nanowires, nanorods or nanosheet alumina in the hollow sphere surface, which has the advantage of open-channel pores and a large and centralized pore size distribution. If used as a carrier of HDM catalysts, this new hierarchical alumina would exhibit a higher catalytic activity and longer cycle life than commercial catalysts. Furthermore, the preparation mechanism and effects of different synthesis conditions on the morphology of hierarchical porous alumina will be systematically studied to achieve macroporous and mesoporous sizes of alumina that can be regulated within a certain range. Finally, the relationship between the materials in the synthesis, pore structure and catalytic performance will be studied, which provides a scientific basis for the design and preparation of new catalysts for residue demetallization.

鉴于当前渣油原料的复杂性，对渣油加氢脱金属催化剂载体的要求越来越高，传统载体氧化铝的孔道结构已难以满足渣油大分子的扩散传质及金属沉积等要求。本项目采用无模板剂水热法，以廉价的无机铝盐为原料，通过在水热过程中调变氧化铝空心球骨架结构(如纳米线、纳米棒、纳米片等)、长度、直径和缠绕方式，制备介孔孔径较大且分布集中、孔道通透性和热稳定性好的鸟巢状开放性多级孔氧化铝，作为渣油加氢脱金属载体具有较高的催化活性及稳定性。在此基础上，深入考察开放性多级孔氧化铝制备过程机理以及不同合成条件对其形貌的影响，实现大孔和介孔孔径在一定范围内可调控。然后将不同孔径大小的多级孔氧化铝应用于渣油加氢脱金属反应规律研究，探索材料合成-孔结构-加氢脱金属催化性能的本质关系，为新型渣油加氢脱金属催化剂的研制提供科学依据。

伴随着原油开采量的不断增加，呈现出原油资源劣质化加剧、渣油比例增加，传统载体氧化铝的孔道结构已难以满足渣油大分子的扩散传质及金属沉积等要求，具有高通透性、大孔隙率以及不同级别孔径分布集中等特点的多级孔氧化铝的研发已经成为未来加氢处理催化剂载体发展的趋势。本项目以廉价无机铝源和尿素为原料，通过水热法合成系列具有多级孔结构的氧化铝载体，实现氧化铝大孔和介孔孔径在一定范围内可调控。详细探究了不同形貌多级孔氧化铝形成的机理及其负载Ni和Mo活性组分所制系列催化剂在加氢处理中的应用，并采用诸多表征技术对催化剂进行表征，对多级孔结构催化剂的构效关系进行探讨。压汞仪测定结果显示，所制氧化铝样品具有两个孔径分布峰，峰值分别对应20 nm和900 nm，其中介孔由纳米丝线缠绕而成，而大孔则由微米球中空贡献，样品孔容达到0.93 cm3/g。由于其独特的鸟巢状孔结构特性，将其制备成NiMo/nest-like-Al2O3加氢脱金属(HDM)催化剂后，与传统的商业催化剂相比，表面活性金属分散度与催化剂的扩散性能有了明显的提升，并在HDM反应中表现出优良的催化性能特别是较长的使用寿命。通过深入研究载体合成-结构-扩散-催化性能的本质关系，为新型、实用渣油加氢催化剂的研制提供科学依据。