Low-temperature and atmospheric pressure plasma for palm biodiesel hydrogenation

Abstract

Partially hydrogenated fatty acid methyl ester (H-FAME) is conventionally produced through partial hydrogenation under high pressure and elevated temperature in the presence of a catalyst. Herein, a novel green, catalyst-free, non-thermal and atmospheric pressure dielectric barrier discharge (DBD) plasma was employed instead of a conventional method to hydrogenate palm FAME. H-FAME became more saturated with the conversion of C18:2 and C18:3 of 47.4 and 100%, respectively, at 100 W input power, 1 mm gas-filled gap size and 80% H2 in the mixed gas at room temperature for 5 h, causing a reduction of the iodine value from 50.2 to 43.5. Oxidation stability increased from 12.8 to 20 h while a cloud point changed from 13.5 to 16 °C. Interestingly, DBD plasma hydrogenation resulted in no trans-fatty acid formation which provided a positive effect on the cloud point. This green DBD plasma system showed a superior performance to a conventional catalytic reaction. It is an alternative method that is safe from explosion due to the mild operating condition, as well as being highly environmentally friendly by reducing waste and energy utilization from the regeneration process required for a catalytic process. This novel green plasma hydrogenation technique could also be applied to other liquid-based processes.

Upgrading palm biodiesel properties via catalyst‐free partial hydrogenation using needle‐plate dielectric barrier discharge plasma torch

“…The reactive species are found in the electrode gap, which is usually between 0.1 and 10 mm. 25 This result was analogous to the previous investigation by Kongprawes et al, 33 who found that a smaller DBD discharge gap resulted in denser micro-discharge filaments and higher plasma intensity. A small gap enabled…”

“…In plasma hydrogenation, hydrogenation, conjugation of double bonds, Diels‐Alder reaction and cracking reaction are considered probable mechanisms by H radicals/H ions as suggested by Kongprawes et al 33 and Wongjaikham et al 49 Figure 11 demonstrates the suggested DBD plasma torch mechanisms for FAME hydrogenation. For hydrogenation, the hydrogen radicals can populate unstable double‐bonded carbon atoms in the unsaturated FAMEs and convert them into stable simple bonds in the saturated FAMEs (Figure 11B).…”

“…The oxidation stability was increased by 3 hours in the case of the former catalyst, and 7 hours in the case of the latter catalyst. The previous investigation using parallel‐plate DBD plasma hydrogenation of palm biodiesel at 100 W input power, 80% H 2 in the H 2 /He mixed gas at ambient temperature showed that the oxidation stability was improved by 7.2 hours 33 . The previous experiment employing microwave plasma for palm FAME hydrogenation at 500 W microwave power and 8.5 L/min H 2 flow rate showed that the oxidation stability was increased by 9.1 hours 49 …”

“…On the contrary, the investigated needle-plate DBD plasma torch produced plasma that has to bubble through the FAME layer, allowing a significant portion of the produced hydrogen radicals to come into direct physical contact with FAME, significantly enhancing the plasma-FAME interaction. 61 Compared to the study of Kongprawes et al, 31,33 the investigated needle-plate DBD plasma torch can use pure H 2 , whereas the parallel-plate DBD plasma requires a mixture of H 2 and He to generate plasma, as well as the requirement to continuously maintain an optimal H 2 -He mix ratio. The advantage of employing only H 2 gas can reduce operating costs, as H 2 gas is about three times less costly than He gas.…”

A Review on the Recent Breakthrough Methods and Influential Parameters in the Biodiesel Synthesis and Purification

“…The Author(s). Published by CBIORE molecules (Kongprawes et al, 2021). Istadi and coworkers conducted a study of plasma assisted transesterification process using palm oil as a feedstock.…”