Experimental part

1-     Materials and experimental setup

The feed used for all experiments was heavy delayed coking gas oil, whose properties are presented in table 1. The precursor salts for each of the loaded metals were cobalt (II) nitrate hexahydrate, nickel (II) nitrate hexahydrate (sigma-Aldrich), heptamolbdate tetrahydrate (sigma-Aldrich), chloroplatinic acid hexahydrate and palladium (II) chloride. Gamma-alumina as a support for catalysts was used for all catalysts. The experimental program was carried out in a continuous system and fixed bed catalytic reactor. The process was carried out in isothermal conditions. Reaction conditions were at a temperature of 400°C, pressure of 100 atm with a volume hourly space velocity of coking gas oil (VHSV) of 1.0 h-1 and a volume ratio hydrogen/gas oil of 900Ncm3/cm3.

 2-     Catalysts Synthesis

The synthesis of catalysts were prepared by successive impregnation method using the pore filling method. The composition for the loaded metals were (4% Co, 10% Mo) for Co-Mo/γ-Al2O3, (1% Pd, 0.25% Pt) for Pt-Pd/γ-Al2O3 and (6% Ni, 3% Mo) for Ni-Mo/γ-Al2O3. Conditioning of the catalyst between impregnation was achieved by drying at 160°C for 4 h and the final conditioning was performed by drying at 160°C for 6 h, calcination at 450°C for 6 h and reduction by treatment with sodium borohydride in aqueous solution at a temperature of 80°C, followed by activation in a stream of hydrogen at 450°C for 6 h.
 

 3-     Catalyst characterization

The acid strength distribution of the active center has been determined by the method of thermal desorption of diethyl-amine on a DuPont Instruments “Thermal Analyst 2000/2100” coupled with a module “951 Thermogravimetric Analizer”.
The surface area and pore volume was calculated from adsorption–desorption isotherms using the multi-point Brunauer–Emmett–Teller (BET) method based on the data in the partial pressure P/P0 range from 0.01 to 0.95.
Characteristics
value
Density, g/cm³
0.9442
Total aromatics, %vol
64
Polyaromatics, % vol
34.1
Sulfur, %gr
0.1621
Aniline point,  ̊ʗ
2
Freezing point, ̊ʗ
-37
Flash point, ̊ʗ
97
Average molar mass, kg/kmol
210