Influence of Mg on Activity and Selectivity of ASA Catalysts in HDS of FCC Gasoline (Влияние Mg на активность и селективность алюмосиликатных катализаторов гидроочистки бензина каталитического крекинга
FCC gasoline is one of the most important components of blended gasoline. The main characteristic of FCC gasoline is high research octane number – 92-93 points. However it is also characterised by high sulfur content – 150-3500 ppm. Hydrotreating of full FCC gasoline fraction results in inevitable octane number loss. To avoid octane number loss, it is necessary to use catalysts with high activity in hydrodesulfurisation and high selectivity to conversion of high-octane components. It was shown earlier that catalytic activity and selectivity can be improved by the use of amorphous silica-alumina (ASA) supports . Also, it was defined that simultaneous incorporation of alkaline and alkaline earth metals, like Mg, into catalysts with ASA increases catalyst selectivity . However, it was not clear how metal should be incorporated into ASA catalyst to achieve the best activity and selectivity.
In present work Co-Mo catalysts based on ASA supports were studied. The catalysts differed in the method of Mg incorporation into catalyst structure. Influence of the method of Mg incorporation on catalyst structure, activity and selectivity was studied.
Mg was incorporated by three ways: 1. During preparation of ASA; 2. During preparation of a support; 3. By impregnation of a support with Mg-containing solution before (MgCoMo) or after (CoMoMg) impregnation by Co-Mo solution. Also the ASA catalyst without Mg (CoMoASA) and the catalyst based on alumina (CoMoAl) were prepared. Mg content in all samples was 1%wt. To introduce Co and Mo into catalyst, the solution containing ammonium heptamolibdate and cobalt nitrate was used to obtain 3.3±0.3% of Mo and 0.7±0.1% Co. ASA powders, supports and catalysts were studied by HRTEM, nitrogen adsorption, chemical analysis and XPS. Catalysts were tested in HDS of model fuel at 2,5 MPa, 220-260°C, LHSV=10 h-1, H2/feed=200.