Abstract
The critical problem arising from the depletion of fossil fuels has stimulated recent interests in alternative sources for petroleum-based fuel. An alternative fuel should be technically feasible, readily available, sustainable, and techno-economically competitive. Biodiesel is considered as a potential replacement of conventional diesel fuel, which is prepared from non-edible and high-acid feedstock via transesterification technology. The focus of this study is to investigate the catalytic activity of mixed metal oxides (MMOs) as catalysts for biodiesel production by using non-edible jatropha oil as feedstock. Various types of MMOs (CaO-MgO, CaO-ZnO, CaO-La2O3, and MgO-ZnO) were synthesized via a co-precipitation method. In this study, transesterification activities are closely related to the physicochemical properties of catalysts. The presence of different active metals in the binary system greatly influenced the surface area, basicity, and the stability of catalysts. The catalytic activity of MMO catalysts was increased in the order of CaO-ZnO (94% ± 1%) > CaO ~ CaO-MgO ~ CaO-La2O3 (~90% ± 2%) > MgO-ZnO (83% ± 2%) > MgO (64% ± 1%) > ZnO (41% ± 2%) > La2O3 (23% ± 1%). In addition, the MMO catalysts, especially CaO-ZnO, demonstrated high reusability and catalyst stability for four cycles of transesterification reaction of jatropha oil.
Highlights
Increasing crude oil demand, deleterious environmental impacts, and restrictions imposed by environmental agencies have created a desire to develop new sustainable fuel
Biodiesel feedstocks cost more than 75% of the overall manufacturing expenditure [6]
It was clearly shown that the alkaline-based mixed metal oxides (MMOs) catalysts possess higher catalytic activities compared to those of single-metal oxides
Summary
Increasing crude oil demand, deleterious environmental impacts, and restrictions imposed by environmental agencies have created a desire to develop new sustainable fuel. Biodiesel has been gaining attention as an alternative energy due to its similar combustion properties with petroleum. This type of biofuel is superior than that of petroleum diesel, with improved physical and chemical properties, such as higher flash point and cetane number, ultralow sulphur content, better lubricity, and smaller carbon footprint [1,2]. With regards to better economic efficiency for biodiesel production, there are three main interconnected factors that dictate biodiesel productivity and market demand: (i) availability of feedstock;. (ii) performance of catalyst, and (iii) production cost [5]. Biodiesel feedstocks cost more than 75% of the overall manufacturing expenditure [6]. Selecting the suitable biological feedstock is crucial as the price of feedstock is based primilary on the Energies 2016, 9, 611; doi:10.3390/en9080611 www.mdpi.com/journal/energies
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