Hydrocracking of atmospheric residue feedstock in hydrotreating processes

Hydrotreating reactions are normally accompanied by hydrocracking reactions that upgrade the residue and yield naphthas, distillates, and gas oil fractions. An experimental study has been conducted to investigate the effect of operating conditions and catalyst type on hydrocracking of atmospheric residue (AR) feedstock during the hydrodesulfurization process. Experimental data were obtained using a micro-reactor pilot plant. AR feedstock and the catalyst are the same types used in atmospheric residue desulfurization (ARD) processes in local refineries. Three types of hydrotreating catalysts were tested at three different temperatures (T = 370, 390, 410 degrees C) and three liquid hourly space velocities (LHSV = 0.5, 1, and 2 hr(-1)). Experimental results demonstrated that the upgrading of residue fractions is achieved through both catalytic and thermal conversions. A discrete lumping approach has been used in developing a number of the kinetic models, for 4, 5 and 10 lumps, and assuming 1(st) and 2(nd) order reaction schemes. Such models provided a perfect fit to the experimental data, and accurately predicted the product yields of the proposed lumps. However, lumping models are only accurate for the product lumps for which they have been developed. The results proved also that ARD hydrocracking is sufficiently represented by 1(st) order kinetics.