Abstract
With the global biodiesel production growing as never seen before, encouraged by government policies, fiscal incentives, and emissions laws to control air pollution, there has been the collateral effect of generating massive amounts of crude glycerol, a by-product from the biodiesel industry. The positive effect of minimizing CO2 emissions using biofuels is jeopardized by the fact that the waste generated by this industry represents an enormous environmental disadvantage. The strategy of viewing “waste as a resource” led the scientific community to propose numerous processes that use glycerol as raw material. Solketal, the product of the reaction of glycerol and acetone, stands out as a promising fuel additive capable of enhancing fuel octane number and oxidation stability, diminishing particle emissions and gum formation, and enhancing properties at low temperatures. The production of this chemical can rely on several of the Green Chemistry principles, besides fitting the Circular Economy Model, once it can be reinserted in the biofuel production chain. This paper reviews the recent advances in solketal production, focusing on continuous production processes and on Process Intensification strategies. The performance of different catalysts under various operational conditions is summarized and the proposed industrial solketal production processes are compared.
Highlights
The growing interest in processes that can combine economical savings and environmental preservation has driven research groups and industry to find alternative technologies and methods that conform to Green Chemistry principles [1]
Even before the introduction of the concepts of Green Chemistry, stimulated by the international petroleum crisis from the 1970s, the search for renewable energy sources led to the discovery of biofuel as the most promising alternative to the use of fossil fuels, since it is appropriate for the transportation sector, responsible for 57% of the global oil demand and for 24% of direct CO2 emissions [4,5,6]
The results reported for the continuous processes are encouraging, showing much higher efficiency, with solketal being produced in less time [48]
Summary
The growing interest in processes that can combine economical savings and environmental preservation has driven research groups and industry to find alternative technologies and methods that conform to Green Chemistry principles [1]. Even before the introduction of the concepts of Green Chemistry, stimulated by the international petroleum crisis from the 1970s, the search for renewable energy sources led to the discovery of biofuel as the most promising alternative to the use of fossil fuels, since it is appropriate for the transportation sector, responsible for 57% of the global oil demand and for 24% of direct CO2 emissions [4,5,6]. Since ethanol is mainly employed as a blending agent for gasoline, mostly used in passengers’ cars, its market has felt more the effects of the pandemic, with a demand reduction of 15% [30] As for biodiesel, it is primarily used for rail transport of goods, a less-affected sector when compared to personal mobility, with an estimated contraction of 6%, less than half of the predicted contraction for ethanol [30]. It is completely miscible in water and in most organic compounds, which endows its solvent capacity [41,42]
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