title: Green acetylation of solketal and glycerol formal by heterogeneous acid catalysts to form a biodiesel fuel additive.
abstract: A glut of glycerol has formed from the increased production of biodiesel, with the potential to integrate the supply chain by using glycerol additives to improve biodiesel properties. Acetylated acetals show interesting cold flow and viscosity effects. Herein, a solventless heterogeneously catalyzed process for the acetylation of both solketal and glycerol formal to new products is demonstrated. The process is optimized by studying the effect of acetylating reagent (acetic acid and acetic anhydride), reagent molar ratios, and a variety of commercial solid acid catalysts (Amberlyst-15, zeolite Beta, K-10 Montmorillonite, and niobium phosphate) on the conversion and selectivities. High conversions (72-95%) and selectivities (86-99%) to the desired products results from using acetic anhydride as the acetylation reagent and a 1:1 molar ratio with all catalysts. Overall, there is a complex interplay between the solid catalyst, reagent ratio, and acetylating agent on the conversion, selectivities, and byproducts formed. The variations are discussed and explained in terms of reactivity, thermodynamics, and reaction mechanisms. An alternative and efficient approach to the formation of 100% triacetin involves the ring-opening, acid-catalyzed acetylation from solketal or glycerol formal with excesses of acetic anhydride.
authors.affiliation: Institute of Chemistry, Federal University of Rio de Janeiro, Cidade Universitária-Rio de Janeiro, 21941-909 (Brazil).
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Dodson
authors.forename: Thays d C M
authors.initials: Td
authors.lastname: Leite
authors.forename: Nathália S
authors.initials: NS
authors.lastname: Pontes
authors.forename: Bianca
authors.initials: B
authors.lastname: Peres Pinto
authors.forename: Claudio J A
authors.initials: CJ
authors.lastname: Mota
mesh_terms: D000080:Acetals / Q000737:chemistry; D019342:Acetic Acid / Q000737:chemistry*; D000089:Acetic Anhydrides / Q000737:chemistry*; D000107:Acetylation; D056804:Biofuels; D002384:Catalysis; D005742:Gasoline; D005990:Glycerol / Q000737:chemistry*; D055772:Green Chemistry Technology
chemical_list: D000080:Acetals; D000089:Acetic Anhydrides; D056804:Biofuels; D005742:Gasoline; C031800:acetic anhydride; D005990:Glycerol; D019342:Acetic Acid
keywords: acetylation; glycerol; heterogeneous catalysis; reaction mechanisms; waste prevention