Rational Design and Testing of Anti-Knock Additives

Andrew D Ure,Manik K Ghosh,Stephen Dooley,Roland Dauphin,Maria Rappo

doi:10.3390/en13184923

Abstract

An innovative and informed methodology for the rational design and testing of anti-knock additives is reported. Interaction of the additives with OH● and HO2● is identified as the key reaction pathway by which non-metallic anti-knock additives are proposed to operate. Based on this mechanism, a set of generic design criteria for anti-knock additives is outlined. It is suggested that these additives should contain a weak X-H bond and form stable radical species after hydrogen atom abstraction. A set of molecular structural, thermodynamic, and kinetic quantities that pertain to the propensity of the additive to inhibit knock by this mechanism are identified and determined for a set of 12 phenolic model compounds. The series of structural analogues was carefully selected such that the physical thermodynamic and kinetic quantities could be systematically varied. The efficacy of these molecules as anti-knock additives was demonstrated through the determination of the research octane number (RON) and the derived cetane number(DCN), measured using an ignition quality tester (IQT), of a RON 95 gasoline treated with 1 mole % of the additive. The use of the IQT allows the anti-knock properties of potential additives to be studied on one tenth of the scale, compared to the analogous RON measurement. Using multiple linear regression, the relationship between DCN/RON and the theoretically determined quantities is studied. The overall methodology reported is proposed as an informed alternative to the non-directed experimental screening approach typically adopted in the development of fuel additives.

Highlights

Over the past 30 years, concerns over anthropogenic greenhouse gas emissions have driven the need for new, more efficient combustion technologies for transportation [1]
In this paper, using knock as a case study, we describe our progress in creating a refined, small-scale, additive design/testing methodology which can resolve this impasse
Anilines display far superior effect on research octane number (RON) compared with phenols, the presence of nitrogen in anilines will result in the formation of NOx

Summary

Introduction

Over the past 30 years, concerns over anthropogenic greenhouse gas emissions have driven the need for new, more efficient combustion technologies for transportation [1]. Some legislative bodies, such as the European Commission, have introduced stringent emissions standards (e.g., Euro 6) [2] as well as directives that mandate introduction of alternative fuels [3]. Throughout this period, the chemical composition of fossil-derived liquid transportation fuels has remained relatively constant and alternative fuels have not been widely adopted. Finished fuels are the result of refining processes which ensure that the fuel conforms to the legislated chemical and physical property specifications required for the market These fuel specifications have remained largely unchanged for a number of years and the associated refinement processes are well established.

Methods

Results

Conclusion