To meet the increasingly stringent sulfur and nitrogen content requirements, developing the hydrodesulfurization (HDS), hydrodenitrogenation (HDN) catalyst with excellent properties is an effective way. The active components of hydrodesulfurization catalysts are generally the transition metal of tungsten, molybdenum, cobalt and their oxides (e.g., tungsten trioxide). Supported and non-supported are the mainly two types of tungsten trioxide hydrodesulfurization catalysts; in addition, their performance affected by additives to some extent.

 

Phosphorus (the P), fluorine (F.), Boron (B) ect. are the commonly used additives of HDS catalyst, which is intended to regulate the nature of the carrier for weakening the strong interaction between the carrier and active metal, improve the surface structure, thereby increasing reducible of metal, prompting the active ingredient reduced to a lower valence state, and finally improving the catalytic property.

 

1. P is one of the most commonly used additives, which is usually as the thirdly component of HDS catalysts, playing a role in promoting the active of HDS, HDN, HAD. Its mechanism of action is P affecting with the carrier-aluminum oxide and generating aluminum phosphate on the carrier surface, thus to achieve the goal of improving the acidity of aluminum oxide.

 

2.B introducing surface acidity of the carrier increases and improves the dispersion of the metal, increase the active center, to improve the activity; moreover, B electronegative than aluminum (Al) is large, the generated surface of the support was added to promote more acid sites, HDS and activity center, thereby increasing the activity of the catalyst.

 

3. F also can increase the acidity of the carrier, enhance the ability of cracking and isomerization of catalyst, improve the activity of hydrogenolysis reaction of C-N, C-S and C-O, while reducing the isoelectric point of aluminum oxide, improving the distribution of the metal; Furthermore, the introduce of F will increase the dispersion of active metal and the hydrogenation activity.