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).