Application of mesoporous catalysts over palm-oil biodiesel for adjusting fuel properties

Biodiesel has superior fuel characteristics, including a higher flash point, better lubricity, and higher oxygen content, and is thus considered a promising alternative clean fuel to petroleum diesel. The cold filter plugging point (CFPP) is the most significant indicator of the low-temperature fluidity of biodiesel. The CFPP of biodiesel is generally higher than that of petroleum diesel primarily due to the longer carbon-chain structures of the fatty acids in the former. Raw materials such as palm oil and waste cooking oil are widely used as the feedstock to produce biodiesel because of their low cost, good availability, and stable lipid provision. However, they generally have a poor low-temperature fluidity, which limits their application in colder climates. In this experimental study, the catalytic dehydrogenation and cracking reaction technique was used to reduce the CFPP of palm-oil biodiesel with an initial CFPP of as high as 14 °C. The catalytic variables of the type of mesoporous catalyst and operating temperature are considered in this study. The resultant fuel properties of palm-oil biodiesel catalyzed by MCM-41 and SiO2/Fe3O4 were compared with biodiesel thermally cracked without a catalyst. The operating temperature of the catalyzed dehydrogenation and cracking reaction was controlled in the range between 400 and 600 °C. The CFPP decrease reached a maximum of 12 °C when the biodiesel was catalyzed by SiO2/Fe3O4 at 600 °C. The maximum water content was produced when the biodiesel sample was thermally cracked with no catalyst at 600 °C. Biodiesel that was catalytically dehydrogenated and cracked with MCM-41 or SiO2/Fe3O4 had a higher iodine value and a lower kinematic viscosity, specific gravity, and CFPP than biodiesel cracked thermally without a catalyst. Moreover, the rate of water formation was reduced when the catalysts were used in the dehydrogenation and cracking reaction. Palm-oil biodiesel catalyzed by SiO2/Fe3O4 at 600 °C was found to produce the lowest CFPP (2 °C), specific gravity, and kinematic viscosity and the highest iodine value of all of the biodiesel samples studied.