Green energy: Hydroprocessing waste polypropylene to produce transport fuel

Abstract

The research aims to produce a viable transport fuel from post-consumer polypropylene plastic. The post-consumer plastic pollution mitigation efforts have found solutions through the circular economy; however, the challenges of the addition of additives in the recycling process are yet to be addressed. Combustion addresses the need for an effective end of life solution to post-consumer plastics, but the search for a clean fuel through pyrolysis still eludes. This study has identified the research gap in the combustion of plastics and produced a clean fuel from polypropylene which meets the environmental requirements. The present study was conducted by hydroprocessing post-consumer polypropylene pyrolysis oil using Nickel-Gold metal embedded on mordenite support as catalyst at 70 bar hydrogen pressure and reaction temperature of 350 °C. Past studies have shown that hydroprocessing of synthetic plastics in upgrading the plastic pyrolysis oil to a transport fuel is viable; however, hydroprocessing of polypropylene pyrolysis oil utilizing a bimetal supported catalyst and the validation of the produced fuel through its combustion and emission performance in compression ignition engines has not been explored yet, so far. The physicochemical properties of the hydroprocessed fuel were within the limits of the European diesel standards. Gas chromatography and mass spectrometry studies facilitated the chemical composition analysis of the produced fuel. The hydroprocessed fuel possessed a composition containing aromatics, n-alkanes, isoalkanes, and each component showed a 90% match with commercial diesel. Diesel engine trials were conducted for the produced fuel, and the engine combustion results showed a 90% match with diesel. The engine emissions showed an 85% match with diesel. The hydroprocess results of this study strengthen the need to upgrade plastic pyrolysis oil and enable the production of clean fuel from polypropylene plastic. Hydroprocessing delivers the much-needed solution in the protection of the environment from post-consumer plastic pollution.