New Octane Booster Molecules for Modern Gasoline Composition

In the framework of reducing GHG emissions and accelerating the decarbonization of the road transport sector, vehicle efficiency is a key factor for competitiveness. In this sense, the refining industry can make its contribution by reformulating high-octane petrol fuel. The impact of this type of gasoline from CO2 emission balance, technical feasibility, and economics standpoints has recently been assessed by the petroleum industry with promising results, and new potential boosters that could improve the octane number of standard gasoline are more needed than ever. The present work summarizes a comprehensive review aimed at collecting available data regarding chemical molecules that can be used in advanced gasoline formulations for modern spark-ignited car engines focusing on ash-free technologies. Potential boosters are divided into two categories: high-octane gasoline components and octane enhancer additives, with 2 vol % the considered frontier concentration between them. Targeted chemical compounds examined in the screening for high-octane components include isoparaffins, olefins, aromatics, alcohols, ethers, esters, ketones, furans, and carbonates. Chemical families assessed as additives were anilines, hydrazines, amines, pyridines, quinolines, indoles, N-nitrosamines, iodine compounds, selenium compounds, phenols, formates, oxalates, and, in lesser extension, other families. The scope of the analysis includes not only anti-knock effectiveness but also associated side effects for the engine, possible effects on both human health and the environment, current applications, and compatibility with existing infrastructure, among others. Promising opportunities in the medium- and long-terms for every family of chemical compounds that can potentially improve the anti-knock character of modern gasolines well beyond current specifications worldwide are presented. Furthermore, a few chemical families are identified as the most promising ones to be used in future gasoline formulations, either as high-octane components (such as ethers, ketones, and esters) or as octane booster additives (such as anilines, N-nitrosamines, and phenols).