Abstract
Biodiesel obtained from palm oil over an environmentally friendly catalyst is highlydesirable. For that matter, dolomite, a natural material was used as a catalyst in this work, and this included potassium oxide (K2O)-doped dolomite, 5 wt% K/D, 10 wt% K/D, 15 wt% K/D, and 20 wt% K/D. X-ray diffraction analysis of dolomite revealed the CaO and MgO phases with high crystallinity, in which intensity reduced after doped with varying concentrations of K2O. When the catalysts were evaluated, the K2O-doped dolomite exhibited a better catalytic activity for palm oil transesterification. In the presence of K2O, the methyl ester reached 98.7%, with the highest being displayed by 15 wt% K/D as compared to 87% over dolomite at reaction temperature of 60 °C, 12:1 methanol to palm oil ratio, 1 wt% catalyst amount and 1 h reaction time. SEM revealed that as more K2O was doped on dolomite, the particles became more agglomerated, with a reduced BET surface area of 1.3 m2/g in 20 wt% K/D as opposed to homogeneously small-sized MgO and CaO particles in dolomite with a high BET surface area of 19.0 m2/g. However, the high activity of the doped catalyst was dictated by the high amount of basic site, as evidenced in TPD-CO2 which showed an increase in the capacity of the basic site with an increased amount of K2O. The catalyst was also reusable up to six times with a negligible decrease in activity due to K+ leaching.
Highlights
The rise in energy demand and price, environmental concerns and fossil fuel depletion have triggered the search for an alternative energy source that is renewable [1]
Dolomite exhibited peaks at 2θ = 32.4°, 37.6°, 54.2° 64.6° 67.9° (JCPDS = 01-074-1226) which is Dolomite exhibited peaks at 2θ = 32.4◦, 37.6◦, 54.2◦ 64.6◦ 67.9◦ (JCPDS = 01-074-1226) which is attributed to quicklime (CaO) and at 2θ = 43.5°◦ and 62°◦ (JCPDS = 01-075-1525) ascribed to periclase attributed to quicklime (CaO) and at 2θ = 43.5 and 62 (JCPDS = 01-075-1525) ascribed to periclase (MgO) with cubic as their crystal structure
Researchers have concentrated on the production of biodiesel through individual quicklime and researchers have concentrated on the production of biodiesel through individual quicklime and periclase (CaO and magnesium oxide (MgO)), as they increase the basic active site for methyl ester production [25]
Summary
The rise in energy demand and price, environmental concerns and fossil fuel depletion have triggered the search for an alternative energy source that is renewable [1]. In this respect, due attention is given to biodiesel due to its numerous merits over petroleum-based fuel [2]. Biodiesel can be obtained via a reaction of triglyceride of vegetable oil or animal fats with the low chain alcohol, preferably methanol with the aid of catalyst (acid or base) through a process known as transesterification reaction [6,7]. It was revealed that the transesterification reaction using a basic homogeneous catalyst is 4000 times faster than acid homogeneous catalyst [8,9]. The reaction showed numerous weaknesses, which include generating a colossal volume of wastewater, Catalysts 2020, 10, 791; doi:10.3390/catal10070791 www.mdpi.com/journal/catalysts
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