EFFECT OF l,2-CYCLOHEXANEDIAMINE-N,N, N', N'-TETRAACETIC ACID AS COMPLEXING AGENT IN A HYDRODESULFURIZATION NIWS/AL2O3 CATALYST

摘要

The NiW catalyst has demonstrated higher hydrogenating (HYD) capacity than typical hydrotreating (HDT) catalysts, NiMo and CoMo, therefore it possess potential for deep hydrodesulfurization (HDS) processes. Similar to Mo-based catalysts, NiW/Al2O3 solids exhibit surface phenomena that are detrimental to the formation of active phase, the so-called "Ni-W-S" phase. However, the concentration of Ni in the Ni-W-S phase has still not been optimized because NiS_x segregation and nickel migration occur. Furthermore, the dispersion and sulfidation of active phase components should be improved [1]. In this sense, addition of complexing agents has shown to be beneficial on the catalytic activity in sulfide HDT catalysts [2]. Firstly, the effect of 1, 2-cyclohexanediamine-N, N, N', N'-tetraacetic acid (CyDTA) incorporation in the synthesis of NiMo and CoMo catalysts has been studied, displaying significant increases in the promotion of MoS2 and consequently, obtaining improvements in HDS activity [2-4]. Meanwhile, Kishan et al [5] studied NiW/SiO2 catalyst prepared with CyDTA and observed similar improvements, which were associated with a delay in the sulfidation of nickel entities, simultaneous sulfidation with tungsten and resulting in close contacts that favored the promotion of WS2 edges. Recently, Suarez-Toriello et al [6] showed that control of pH of the nickel-citric acid solution had an important role over the modulation of metal-support interactions, achieving favorable conditions for the formation of the sulfide phase and reaching important increases in catalytic activity in the HDS of 4,6-dimethyldibenzothiophene (46DMDBT).