Process for hydrodesulphurizing gasoline employing a catalyst with controlled porosity

Abstract

A novel process is described which allows selective hydrodesulphurizing gasoline cuts containing sulphur-containing compounds and olefins. The process employs a catalyst comprising a support selected, for example, from refractory oxides such as aluminas, silicas, silica-aluminas or magnesia, used alone or as a mixture, a group VI metal, preferably Mo or W which may or may not be promoted by a group VIII metal, Co or Ni. The catalyst is characterized by a mean pore diameter of more than 22 nm. The process may comprise one or more steps.

Description

[0001] The present invention relates to a desulphurization process employing a catalyst containing at least one support, and an active phase comprising a metal, for example. The process allows hydrodesulphurizing gasoline, more particularly gasoline from a catalytic cracking process (fluid catalytic cracking, FCC). [0002] The production of reformulated gasoline satisfying new environmental regulations primarily necessitates substantially reducing their sulphur content. Current and future environmental regulations within the European community require refiners to reduce the sulphur content in the gasoline pool to values of 50 ppm or less by 2005 and 10 ppm by 1 Jan. 2009. The feed to be treated is generally a gasoline cut containing sulphur, such as a cut from coking, visbreaking, steam cracking or catalytic cracking (FCC). That feed is preferably constituted by a gasoline cut derived from a catalytic cracking unit with a typical boiling point range which extends from that of hydroca...

AI Technical Summary

Benefits of technology

[0012] The residual sulphur-containing compounds present in gasoline desulphurized by deep hydrodesulphurization comprise recombination mercaptans derived from the addition of H2S formed during the reaction to the olefins present and to unsaturated sulphur-containing compounds such as thiophene and alkylthiophenes. The presence of recombination mercaptans at least in part explains why, when seeking to deep desulphurize gasoline comprising an olefin fraction, a major increase in the degree of olefin hydrogenation is observed for high degrees of desulphurization. Thus, when the desired degree of desulphurization approaches 100%, the degree of olefin saturation is greatly increased. The use of more selective catalysts may, however, when degrees of desulphurizing close to 100% are desired, limit olefin hydrogenation or allow the formation of recombination mercaptans. One of the primary aims of deep desulphurization is thus to develop processes that can attain high selectivities, i.e. minimize olefin hydrogenation reactions while treating residual sulphur-containing compounds such as mercaptans.

[0018] The present invention describes a process that can reduce the total sulphur content of hydrocarbon cuts and preferably FCC gasoline cuts without losing the gasoline yield and minimizing the reduction in octane number.

Problems solved by technology

However, that process suffers from the major disadvantage of causing a very large drop in the octane number of the cut due to hydrogenation or saturation of a major portion or even all of the olefins under the hydrotreatment conditions.

The use of more selective catalysts may, however, when degrees of desulphurizing close to 100% are desired, limit olefin hydrogenation or allow the formation of recombination mercaptans.