The effect of calcination temperature on the activity of hydrodesulfurization catalysts supported on mesoporous activated carbon

The removal of sulfur compounds from petroleum is increasingly important because sulfur compounds poison catalysts (i.e. reduce the activity of the catalysts in oil refinery processes) and are a source of environmental pollution. On the other side, waste rubber tires contribute to environmental pollution. Here, the motive is the utilization of activated carbon (AC) from the waste tires as a support for bimetallic catalysts. Therefore, NiMo catalysts supported on waste tire-derived AC were prepared through an excessive wetness co-impregnation method and subjected to calcination at temperatures of 100, 200, 300 and 400 °C for hydrodesulfurization (HDS). A surface area analyzer, Fourier-transform infrared spectroscope, scanning electron microscope, and Raman spectroscope were used to characterize the prepared catalysts. The HDS reactions with the prepared catalysts were performed in a high-pressure reactor using a model fuel containing 1000 ppm dibenzothiophene at different reaction times. The results showed that the catalyst that is calcined at 300 °C (i.e. NiMo/AC300) is the most active for HDS as compared to the catalysts calcined at other temperatures (i.e. 100, 200 and 400 °C). This catalyst (i.e. NiMo/AC300) has a surface area of 352 m²/g, a 6 nm average pore diameter, a total acidity of 0.26 mmol ammonia/g and exhibits a moderate activation energy for NH₃ desorption (i.e. E_a = 102 kJ/mol). The developed catalysts show promising results with the advantage of having a dual benefit – eliminating waste tire disposal problem and producing valuable supports for HDS catalysts to yield sulfur-free fuels.