Study On Coking On Catalyst During Catalytic Hydroprocessing Of Residue

Coking on catalyst during hydroprocessing of petroleum residues is an important issue that should be addressed to explore the principle of its formation behavior. This work studies reaction and coking behaviors of an atmospheric residue and a vacuum residue over a sulfided commercial NiMo/?-Al2O3 catalyst in the presence and absence of a hydrogen donor solvent, tetrahydronaphthalene (THN), in a micro-reactor at temperatures of 400-460 ? and reaction time of 0-60 min. It reports the changes in yields of gas, liquid and solid (coke) phase, as well as the changes in quantity of coke on the catalyst and in radical concentration of both the thermal and hydroprocessing reaction system. Radical concentration, g value and linewidth are also used to analyze the evolution of coke. The main results are described as followed:1. Compared with the quality control methods of each products, the radical concentration measured by paramagnetic resonance (ESR) can be more sensitive, fast and simple for monitoring residue cracking and hydroprocessing.2. The catalyst reduces the radical concentration, radical generating activation energy and promotes the hydrogen donation of THN. Initial coke deposition on the catalyst begins with the adsorption of the heavy component in the residue and is accompanied by the condensation reaction, indicated by the increase of radical concentration.3. The hydrogen donation of THN reduces the coking rate, the radical concentration, the activation energy of coking kinetics and the condensation degree.4. Radical concentration, linewidth and g value all change regularly with the residue reaction, mainly reflecting the condensation of coke structure and removal of the heteratom.