Cyclic Oxygenates: A New Class of Second-Generation Biofuels for Diesel Engines?

Abstract

Combustion behavior of various oxygenated fuels has been studied in a DAF heavy-duty (HD) directinjection (DI) diesel engine. From these fuels, it is well-known that they lead to lower particle (PM) emissions; however, for a given fuel oxygen mass fraction, there are significant differences in PM reduction. Although this can be traced back to the specific molecular structure of the oxygenate in question, no consensus can be found in the literature as to the explanation hereof. In this study, the sooting tendency (smoke number) of three oxygenates [viz., tripropylene glycol methyl ether (TP), dibutyl maleate (DB), and cyclohexanone (X1)] was compared to that of commercial diesel fuel (EN590, D). The results suggest that the cetane number (CN) (i.e., fuel reactivity) may play an important role. More specifically, the low reactive oxygenate X1, with its cyclic carbon chain, was found to perform exceptionally well compared to the more reactive linear and branched oxygenates DB and TP, respectively. Cyclic oxygenates are abundant in nature. Cellulose, the most common organic compound on earth, is the best-known example. Although it is not trivial, liquid cyclic oxygenates can be made from lignocellulosic biomass. Particularly, the production of C 6 oxygenates (e.g., guaiacol, cyclohexanone, phenol, etc.), which can be derived from lignin, is the subject of current investigation. Fuels produced from such biomass (e.g., plant waste or the nonedible part of plants) are referred to as secondgeneration biofuels and are expected to play a pivotal role in the near future.

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

“…[311][312][313] However,t his type of application is still in development, requiring further improvements to minimise soot and gas emissions.…”

Experimental Study of Fuel Composition Impact on PCCI Combustion in a Heavy-Duty Diesel Engine

“…Results from earlier research with cyclic oxygenates show very promising results even for th combustion regime [17,18]. Using blends of diesel with these bio-derived oxygenates [19,20] might be an extremely interesting concept in combination with high EGR as this provides a unique platform to reduce CO 2 , soot and NO x at the same time. …”

Synthesis and utilization of catalytically cracked cashew nut shell liquid in a diesel engine

“…Certainly, the major constituent of CC-CNSL, as evident from figure 3, was found to be 2-methyl phenol, an aromatic oxygenate that is deemed to promote the combustion process. Reportedly, all aromatic oxygenated are deemed to promote fuel oxidation and combustion process [24,25], given the oxygen present in it is loosely bonded and would actively participate in the combustion process. Further, it also features the presence of few esters along with other hydrocarbons, so as to materialize as a potential fuel for diesel engine.…”