Ionic Liquids (A Review): The Green Solvents for Petroleum and Hydrocarbon Industries

Ionic liquids can be considered as green solvents due to their very low vapor pressure and wide range of applications with unique physical and chemical properties. The potential of ionic liquids have been recognized worldwide. Scientists and engineers have been working in the advancement of preparation and applications of ionic liquid so that it can provide a range of options to industrialists looking to minimize the environmental impact of their chemical processes and processing cost. In petroleum and hydrocarbon industries, various solvents have been used such as ethers, amines, alcohols and other volatile organic compounds for the options like extraction, absorption, azeotropic distillation etc. These solvents have their own limitations as environmental issue, recycle ability etc. These limitations can be overcome by the use of ionic liquids. To minimize the negative health and environmental effects from automobile exhaust, many countries recently have mandated a drastic reduction in the sulfur content in transportation fuel. In petroleum industry, low-sulfur fuels are often obtained from hydrocracking processes or hydrotreating processes. Although hydrotreating processes have been highly effective for the reduction of sulfur levels, further improvement of the hydrodesulfurization efficiency is limited to increasing severe operational conditions at escalated cost with high energy and hydrogen consumption and other undesired side reactions. In present paper, the attempts are made to write a critical review on various aspects of ionic liquids with the aim of their applications in petroleum and hydrocarbon industries and the various factors affecting their activity in removal of sulfur from transportation fuels.