Hydrogen Transfer Cracking of Arabian Residua in Tetralin - I

Abstract

Heavy Arabian vacuum residua were hydrocracked non-catalytically using tetralin as a hydrogen donor solvent. A bolted closure packless high temperature/high pressure autoclave with a magnedrive assembly was used batchwise for this purpose. The effects of temperature, pressure, and reactants ratio on the performance of the system were studied. The products were analyzed both qualitatively and quantitatively. Methods of analysis included: hydrocarbon group analysis using an HPLC, simulated distillation using a GC, sulfur determination and API gravity, asphaltene and carbon residue determination according to ASTM standards. Tetralin proved to be an effective donor for Arabian residua. HPLC and simulated distillation analysis showed that heavy compounds of the residuum were converted into lighter ones. When a ratio of tetralin to residuum less than 1/1 by weight was used coke formed in amounts proportional to tetralin. For ratios greater than 1/1 no coke formation was observed. A ratio of 2/1 was found to be a suitable ratio and was used in all runs. It was found that a minimum initial pressure of nitrogen gas (0.5 MPa) was sufficient to keep the reactants in the liquid state. Otherwise, pressure had no effect on the conversion. As the temperature was increased the conversion to lighter products increased. The relative percentage change of both asphaltenes and carbon residue increase with temperature. Degree of desulfurization also increased with temperature. This preliminary study was limited to use a maximum temperature of 435 °C. Increasing the temperature beyond this limit causes gas venting, and thus a loss of gaseous products. The system will be modified to work at higher temperatures by the method of rapid injection.