Methods for Viscosity Reduction of Heavy Crude Oil with Focus on Nano Catalysts: A Review Study

Investigations on a variety of methods for reducing the viscosity of heavy crude oil show that conventional methods due to their high temperature and pressure are expensive, unsafe, costly maintenance with huge utility and low efficiency. Thermal cracking was the first method of reducing viscosity, which presence of catalysts could improve some of its problems such as instability and extremely high temperatures. But temperature was still high and due to these basic problems, efforts are continuing to achieve better result and more efficiency. Usage of dispersed nanocatalysts greatly increased the efficiency of these reactions so that at presence of hydrogen and nano dispersed catalyst viscosity reduced up to 99%. Many nanocatalysts have been studied so far, for example, nano zeolite, carbon, iron, and nickel which have yielded good results, but these methods also have some special problems such as synthesis of nanocatalysts with appropriate surface and bed and collecting them after reaction. Processes with modern technology such as irradiation, cavitation and electromagnetic waves at a laboratory scale have been able to produce good results at very low temperatures and low pressures. In one of these experiments, the microwave could reduce 99.7% viscosity of heavy oil at the presence of nanoparticles of carbon nanotubes. Of course, these methods have not been commercialized yet because of complicated conditions and special equipment so this way is very good for continuing research on them.