Impacts of a Nanosized Ceria Additive on Diesel Engine Emissions of Particulate and Gaseous Pollutants

Abstract

Fuel additives incorporating nanosized ceria have been increasingly used in diesel engines as combustion promoters. However, few studies have assessed the impact of these nanotechnology-based additives on pollutant emissions. Here, we systematically compare emission rates of particulate and gaseous pollutants from a single-cylinder, four-cycle diesel engine using fuel mixes containing nanoceria of varying concentrations. The test fuels were made by adding different amounts of a commercial fuel additive Envirox into an ultralow-sulfur diesel fuel at 0 (base fuel), 0.1-, 1-, and 10-fold the manufacturer-recommended concentration of 0.5 mL Envirox per liter of fuel. The addition of Envirox resulted in ceria-concentration-dependent emission reductions of CO2, CO, total particulate mass, formaldehyde, acetaldehyde, acrolein, and several polycyclic aromatic hydrocarbons. These reductions at the manufacturer-recommended doping concentration, however, were accompanied by a substantial increase of certain other air pollutants, specifically the number of ultrafine particles (+32%), NOx (+9.3%), and the particle-phase benzo[a]pyrene toxic equivalence quotient (+35%). Increasing fuel ceria concentrations also led to decreases in the size of emitted particles. Given health concerns related to ultrafine particles and NOx, our findings call for additional studies to further evaluate health risks associated with the use of nanoceria additives in various engines under various operating conditions.

Effects of a nanoceria fuel additive on the physicochemical properties of diesel exhaust particles

“…From 0x to 10x, DEP sizes decreased by 40% from 194.6 nm to 116.3 nm. This trend was in agreement with previous findings with airborne DEPs (i.e., DEPs in the air of the test chamber before undergoing filter collection and subsequent extraction) by our group 9 and others 6 . This trend was mainly due to the fact that adding ceria nanoparticles increasing the soot oxidative process, which led to a reduction in the size of agglomerated particles by breaking them down into smaller particles.…”

“…Firstly, the soot oxidation may have facilitated the breakdown of larger particle agglomerates into smaller ones, leading to decreases in particle size. 9,[19][20][21] Secondly, this oxidation process was further revealed by the Raman spectra showing the process of preferentially oxidizing the disordered carbon structure rather than the ordered (graphitized) carbon structure. Thirdly, this oxidation may contribute to the increased organic carbon to elemental carbon ratio for the 10x Envirox TM condition.…”

Near-Road Modeling and Measurement of Cerium-Containing Particles Generated by Nanoparticle Diesel Fuel Additive Use

“…This reported CO 2 emission reduction is consistent with that of laboratory-based studies which range from no change in emissions to a 6% reduction. 6,7 The World Health Organization (WHO) has recently labeled outdoor air pollution a leading environmental cause of mortality (leading to 3 million premature deaths annually), particularly from particles with a diameter <2.5 μm (PM 2.5 ) which are linked to lung cancer and pulmonary disease. 8−10 In addition, the WHO's International Agency for Research on Cancer has classified diesel engine exhaust as carcinogenic to humans.…”

Synthesis of stable cerium zirconium oxide nanoparticle – Diesel suspension and investigation of its effects on diesel properties and smoke

“…Zhnag et al [25] studied the impact of dosing of cerium oxide nanoparticle additive (Envirox Ò ) in diesel, on engine performance and pollutant emissions. An improvement of fuel efficiency up to 5.6% was observed with the use of this additive.…”