Manishkumar S. Tiwari

Glycerol is a valuable feedstock, produced in biorefineries as a byproduct of biodiesel production. Esterification of glycerol with acetic acid yields a mixture of mono-, di-, and triacetins. The acetins are commercially important value-added products with a wide range of industrial applications as fuel additives and fine chemicals. Esterification of glycerol to acetins substantially increases the environmental sustainability and economic viability of the biorefinery concept. Among the acetins, diacetin (DA) and triacetin (TA) are considered high-energy-density fuel additives. Herein, we have studied the economic feasibility of a facility producing DA and TA by a two-stage process using 100,000 tons of glycerol per year using Aspen Plus. The capital costs were estimated by Aspen Process Economic Analyzer software. The analysis indicates that the capital costs are 71 M$, while the operating costs are 303 M$/year. The gross profit is 60.5 M$/year, while the NPV of the project is 235 M$ with a payback period of 1.7 years. Sensitivity analysis has indicated that the product price has the most impact on the NPV.

The manufacture of high-value products from biomass derived platform chemicals is becoming an integral part of the biorefinery industry. In this study, we demonstrate a green catalytic process using solvent free conditions for the synthesis of hydroxymethylfurfural (HMF) levulinate from HMF and levulinic acid (LA) over tin exchanged tungstophosphoric acid (DTP) supported on K-10 (montmorillonite K-10 clay) as the catalyst. The structural properties of solid acid catalysts were characterized by using XRD, FT-IR, UV-vis, titration, and SEM techniques. Partial exchange of the H⁺ of DTP with Sn (x = 1) resulted in enhanced acidity of the catalyst and showed an increase in the catalytic activity as compared to the unsubstituted DTP/K-10 as the catalyst. The effects of different reaction parameters were studied and optimized to get high yields of HMF levulinate. The kinetic model was developed by considering the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism, and the activation energy was calculated to be 41.2 kJ mol^-1. The prepared catalysts were easily recycled up to four times without any noticeable loss of activity, and hot filtration test indicated the heterogeneous nature of the catalytic activity. The overall process is environmentally benign and suitable for easy scale up.

The increase in biodiesel production has resulted in the oversupply of glycerol into the market. Purified and processed glycerol has found many direct applications in pharmaceuticals, food, etc. However, the cost of processing and market value of processed glycerol has driven the research of direct utilization of crude glycerol to industrially essential chemicals. Various methods and research have been devoted to using glycerol to produce value-added products separately. Glycerol can undergo several transformation reactions like hydrogenation, oxidation, alcoholysis, and etherification. Etherification of glycerol can be divided into three main reactions: self-etherification, using alcohol, and olefins and these products have vast applications such as fuel additives, plasticizer, etc. The current review presents a comprehensive summary of glycerol etherification to value-added products and their applications. The catalytic system developed along with reaction conditions and the factors responsible for the better activity is also discussed. Overall, the review presents a detailed discussion on the catalytic system developed, the utilization of different alcohols and olefins, and the application of products. Moreover, the environmental and economic aspects of the etherification of glycerol via various conversion routes while assessing the process parameters needs to be tackled to attain wider adoption of the process.