Síntese e caracterização de 1,2,3-triacetoxipropano (triacetina) utilizando propan-1,2,3-triol obtido de tratamento de fase glicerina de processo produtivo de biodiesel

Abstract

In this work, a study was carried out of the conversion reaction of glycerol, contained in the glycerin phase of biodiesel, into triacetin, through an esterification reaction using the Fischer-Speier method. 1,2,3-triacetoxpropane (triacetin) is an important product that can be used as an additive that improves the quality of biodiesel, in terms of reducing the emission of polluting gases, among other application possibilities. On a preliminary basis, 4 reactional study tests were started using glycerin and acetic acid through homogeneous acid catalysis, using concentrated sulfuric acid. The best result protocol in the triacetin phase (test by TLC), obtained in this step, was adopted as a standard for obtaining triacetin in subsequent reactions. Initially, the decanted glycerin phase of the biodiesel production process was treated with residual oil obtained from transesterification, using methanol in homogeneous catalysis with KOH, to obtain a glycerin phase with a high glycerol content (blonde glycerin). The treatment of the glycerin phase was carried out by acid application, decantation, centrifugation, treatment by adsorption on activated carbon and filtration. Blonde glycerin was subjected to esterification with excess acetic acid/sulfuric acid (catalyst), neutralization with CaO and drying with silica. Proof of obtaining triacetin was performed by: Thin Layer Chromatography (TLC), Gas Chromatography Coupled to Mass Spectrometry (GC/MS), Absorption Spectroscopy in the Infrared Region (IR) and Yield by Energy Balance Process Masses (by GC/EM). The results obtained were considered satisfactory, the absorption bands (mean axial stretch absorptions (C – O), between 1000 and 1300 cm-1) distinct from esters were verified in the IR, it was proven that triacetin was obtained, characterized by the spectrum of mass obtained at the peak in 8,47 min and quantified by analytical curve with a yield of 6.78% (w/w) in relation to the blonde acetin phase (monoacetins, diacetins and triacetin), acylium ion characteristic of esters as the base peak of the spectrum w/z = 43 and other fragments in w/z = (103; 145; 116; 115; 73; 74; 86), by GC/MS. The overall yield in triacetin conversion rate was considered promising when compared with other process results found in the literature (results with 5 to 8% yield).