Selective Electrochemical Conversion of Glycerol to Glycolic Acid and Lactic Acid on a Mixed Carbon-Black Activated Carbon Electrode in a Single Compartment Electrochemical Cell

In recent years, the rapid swift increase in world biodiesel production has caused an oversupply of its by-product, glycerol. Therefore, extensive research is done worldwide to convert glycerol into numerous high added-value chemicals i.e., glyceric acid, 1,2-propanediol, acrolein, glycerol carbonate, dihydroxyacetone, etc. Hydroxyl acids, glycolic acid and lactic acid, which comprise of carboxyl and alcohol functional groups, are the focus of this study. They are chemicals that are commonly found in the cosmetic industry as an antioxidant or exfoliator and a chemical source of emulsifier in the food industry, respectively. The aim of this study is to selectively convert glycerol into these acids in a single compartment electrochemical cell. For the first time, electrochemical conversion was performed on the mixed carbon-black activated carbon composite (CBAC) with Amberlyst-15 as acid catalyst. To the best of our knowledge, conversion of glycerol to glycolic and lactic acids via electrochemical studies using this electrode has not been reported yet. Two operating parameters i.e., catalyst dosage (6.4–12.8% w/v) and reaction temperature [room temperature (300 K) to 353 K] were tested. At 353 K, the selectivity of glycolic acid can reach up to 72% (with a yield of 66%), using 9.6% w/v catalyst. Under the same temperature, lactic acid achieved its highest selectivity (20.7%) and yield (18.6%) at low catalyst dosage, 6.4% w/v

Enzymes in Biofuels Production

With the inevitable depletion of the nonrenewable resources of fossil fuels and due to their favorable environmental features, biofuels promise to be the preferred fuels of tomorrow. They can displace petroleum fuels and, in many countries, reduce the dependence on imported fuel. Biofuels, derived from biomass conversion, such as biodiesel, bioethanol, biohydrogen, and biogas, are sustainable and renewable sources of energy, which are also considered CO2 neutral. In addition, burning biofuels results in reduced levels of particulates, carbon oxides and sulfur oxides, emissions compared to fissile fuels

Production of lactic acid and glycolic acid in one-pot electrochemical cell

In recent years, due to the oversupply of glycerol globally, its price has dropped dramatically or become valueless. The aim of this study is to convert glycerol into high value-added compounds such as glycolic acid and lactic acid in one-pot electrochemical cell. The electrochemical process was carried out over platinum (as anode electrode) and activated carbon composite (as cathode electrode), with amberlyst-15 as reaction catalyst. The results obtained have proven that this simple method is applicable to produce glycolic acid and lactic acid in one step electrochemical process with a total product yield above 70 %. Finally, the overview reaction mechanism to the formation of these products was proposed. Please click Additional Files below to see the full abstract

Response surface optimization of conditions for clarification of carambola fruit juice using a commercial enzyme.

Response surface methodology (RSM) was employed for simultaneous analysis of the effects of enzymatic treatment conditions of incubation time, incubation temperature and enzyme concentration on physical characteristics such as turbidity, clarity, viscosity, and color. In this study, a two-factor central composite design was used to establish the optimum conditions for the enzymatic treatment for clarification of carambola fruit juice. Carambola fruit juice was treated with pectinase enzyme at different incubation time (20–100 min), incubation temperature (30–50 °C) and enzyme concentration (0.01–0.10 v/v%). These three variables were used as independent variables, whose effects on turbidity, clarity, viscosity and color were evaluated. Significant regression models describing the changes on turbidity, clarity, viscosity and color with respect to the independent variables were established with coefficient of determination, R2, greater than 0.70. The results indicated that the enzyme concentration was the most important factor affecting the characteristics of the carambola fruit juice as it exerted a significant influence on most of the dependent variables. The recommended enzymatic treatment condition from the study was at 0.10% enzyme concentration at 30 °C for 20 min

Atmospheric hydrodeoxygenation of bio-oil oxygenated model compounds:A review

Hydrodeoxygenation (HDO) of various bio oil oxygenated model compounds in low H2 pressure has been discussed in this study. Because of the high yield of aromatic mixtures in bio-oil, they carry great potential for fuel efficiency. Nevertheless, due to its high viscosity, abundance of acid, and heteroatom contaminants, the bio-oil ought to be upgraded and hydrotreated in order to be applied as an alternative fuel. A continuous low H2 pressure HDO of bio-oil is favored as it could be simply integrated with conventional pyrolysis systems, functioning at low pressures, as well as supporting a flexible plan for serial processing in respective bio-refineries. Additionally, such a process is cheaper and safer in comparison with the high pressure set ups. This review meticulously elaborates on the operation conditions, challenges, and opportunities for using this process in an industrial scale. The operating temperature, the H2 flow ratio, the active site, and the catalyst stability are some important factors to be considered when it is intended to reach a high conversion efficiency for the HDO in low H2 pressure

Development of a Novel Hydrophobic ZrO2–SiO2 Based Acid Catalyst for Catalytic Esterification of Glycerol with Oleic Acid

The inevitably low value of glycerol has led to extensive investigations on glycerol conversion to value-added derivatives. The esterification of glycerol with oleic acid is currently a very important industrial process. In this work, a novel heterogeneous acid catalyst featuring hydrophobic surface is developed on modified ZrO2–SiO2 support as water-tolerant solid acid catalyst is vital for biphasic esterification reactions that produce water. The novel ZrO2–SiO2–Me&Et-PhSO3H catalyst was prepared through silication and surface modification with trimethoxymethylsilane and 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane. This work showed that it is possible to control the acidity and hydrophobicity of the catalyst by tailoring the amount of surface modification agents. It was found that the hydrophobicity of the catalyst decreased as its acidity increased. Furthermore, at constant catalyst acidity, the more hydrophobic catalyst showed a better yield

Catalytic role of solid acid catalysts in glycerol acetylation for the production of bio-additives: a review

Bio-additives obtained from the acetylation of biodiesel-derived glycerol have been extensively synthesized because of their nature as value-added products and their contribution to environmental sustainability. Glycerol acetylation with acetic acid produces commercially important fuel additives. Considering that the recovery of individual monoacetin, diacetin (DA), and triacetin (TA) is complicated, many endeavours have enhanced the selectivity and total conversion of glycerol using acetic acid during catalytic acetylation. In this work, we extensively review the catalytic activity of different heterogeneous acid catalysts and their important roles in glycerol acetylation and product selectivity. In addition, the most influential operating conditions to attain high yields of combined DA and TA are achieved by closely examining the process. This review also highlights the prospective market, research gaps, and future direction of catalytic glycerol acetylation

Structure–selectivity relationship of a zirconia-based heterogeneous acid catalyst in the production of green mono- and dioleate product

A novel catalytic technique is vital to produce mono- and dioleate (GMO and GDO) from bioglycerol: a renewable resource and by-product of biodiesel. The advantage of this invention is the direct production of GMO and GDO through catalytic approach compared to the conventional method that requires transesterification and distillation processes. In this paper, glycerol esterification with oleic acid using a catalyst was experimented. The process was carried out over a hydrophobic mesoporous zirconia–silica heterogeneous acid catalyst (ZrO2–SiO2–Me&Et–PhSO3H) with three types of sulphated zirconia catalysts (SO42−/ZrO2) to produce high-selectivity GMO and GDO products. The catalytic performance of the hydrophobic ZrO2–SiO2–Me&Et–PhSO3H catalyst was benchmarked with that of SO42−/ZrO2 which was developed from three zirconium precursors. Results showed that the pore volume and hydrophobicity of the designed catalyst greatly could influence the product selectivity, thus enabling smaller substrates GMO and GDO to be dominated in the synthesis. This finding was supported by characterisation data obtained through N2 adsorption–desorption, X-ray diffraction and scanning electron microscopy. In addition, a good correlation was found between pore volume (pore size) and product selectivity. High pore volume catalyst favoured GDO production under identical reaction conditions. Pore volume and size can be used to control product sensitivity. The hydrophobicity of the catalyst was found to improve the initial reaction rate effectively