More and more rigorous environmental regulations limiting the emissions of sulfur dioxide and the continuing decline in the quality of petroleum feedstocks have given rise to the need for investigation and development of high-performance hydrodesulfurization (HDS) catalysts. This paper provides a review of recent progress in the characteristics, active phase, synthesis, modification and HDS catalytic performance of Ni₂P catalyst. There are two types of initial active sites in Ni₂P. The Ni(1) initial active sites have a tetrahedral geometry, and which are involved in the direct desulfurization pathway in HDS. The Ni(2) initial active sites have a square pyramidal geometry, and which are responsible for the high catalytic activity in the hydrogenation pathway in HDS. A surface nickel phosphosulfide phase may be formed under HDS reaction, and which is considered as the real active phase. Ni₂P is mainly prepared by temperature-programmed reduction and liquid phase synthesis. The support, promoter and complex agent have important effect on the formation of Ni₂P active phase, as well as the catalytic activity. Compared with commercial sulfide catalyst, the Ni₂P catalyst shows higher HDS activity for thiophene, dibenzothiophene and 4, 6-dimethyldibenzothiophene.

Contents
1 Introduction
2 Crystal characteristics of Ni₂P
3 Active phase of Ni₂P in HDS
4 Synthesis of Ni₂P catalysts
4.1 Temperature programmed reduction
4.2 Liquid phase synthesis
4.3 Other synthesis
5 Modification of Ni₂P
6 HDS catalytic performance of Ni₂P catalyst
7 Summary and perspective