Epoxidation of Argemone mexicana oil with peroxyacetic acid formed in-situ using sulfated tin (IV) oxide catalyst: Characterization; kinetic and thermodynamic analysis.

In this study, sulfated tin (IV) oxide solid acid catalyst was prepared for the epoxidation of Argemone mexicana oil (AMO) with peroxyacetic acid formed in-situ. The catalyst was synthesized using the chemical co-precipitation method and characterized. The effects of various epoxidation parameters on ethylenic double bond conversion (%) and oxygen ring content were analyzed. The maximum ethylenic double bond conversion of 95.5% and epoxy oxygen content of 6.25 was found at the molar ratio of AMO to 30% of H2O2 = 1:2.5, molar ratio of AMO to acetic acid = 1:1.5, catalyst concentration = 12.5%, and reaction temperature = 70 °C at reaction time = 6 h. The kinetic and thermodynamic features of the epoxidation of AMO were also analyzed with appropriate models. The results of the kinetic study of the epoxidation reaction followed pseudo first order with the activation energy = 0.47.03 kJ/mol. Moreover, the thermodynamic constants of epoxidation of AMO were found as ΔH = 44.18 kJ/mol, ΔS = -137.91 Jmol-1k-1) and ΔG = 91.12 kJ/mol. The epoxidized product of AMO was further analyzed using FTIR, 1H NMR, and 13C NMR. The results of these analyses confirmed the successful conversion of the ethylenic double bond in the AMO to EAMO.

Valorization of indigenous Millettia ferruginea seed oil for biodiesel production: parametric optimization, physicochemical characterization, engine performance and emission characteristics.

The current investigation aimed to synthesis the biodiesel from an indigenous Millettia ferruginea seed oil (MFO) using methanol with alkali catalyst (NaOH). The factors affecting the oil extraction viz., extraction time, kernel size, solvent: solid, extraction temperature) was optimized via the parametric study. Response surface methodology was utilized to improve the transesterification reaction. The optimum temperature, catalyst concentration, and methanol to oil molar ratio to achieve maximum biodiesel production of 98.1 wt.% were 52.3 °C, 1.3 wt.%, and 8.8:1, respectively. FTIR, NMR, and GC-MS analyses have been used for extracted oil and fatty acid methyl ester (FAME). From the 1H NMR analysis, the conversion of MFO to FAME was 97.5%. Moreover, engine performance and emission characteristics of biodiesel blends and diesel were investigated using a single-cylinder diesel test engine. The specific fuel consumption of biodiesel blends was higher than diesel fuel whereas the thermal efficiencies were found to be lower. The results showed that the blend B5 provided superior performance next to diesel fuel. Besides, the CO and HC emissions of B5 at 80% load condition were 7.28 and 8.56% lesser than diesel, respectively. However, in comparison to diesel, CO2 and NOx emissions were higher for the biodiesel blends.

Reducing Sugar Production from Teff Straw Biomass Using Dilute Sulfuric Acid Hydrolysis: Characterization and Optimization Using Response Surface Methodology.

The present study evaluated first the characterization of Teff straw and then Box-Behnken design (BBD), and response surface methodology was adopted to optimize the parameters (hydrolysis temperature, dilute sulfuric acid concentration, solid to liquid ratio, and hydrolysis time) of dilute sulfuric acid hydrolysis of Teff straw in order to get a maximum yield of total reducing sugar (TRS). The chemical analysis of Teff straw revealed high amounts of cellulose (41.8 wt%), hemicellulose (38 wt%), and lignin (17 wt%). The morphological analysis using SEM showed that hydrolyzed Teff straw with dilute sulfuric acid has more pores and distorted bundles than those of raw Teff straw. XRD analysis also indicated that hydrolyzed Teff straw has higher crystallinity index and smaller crystallite size than raw Teff straw, which might be due to removal of hemicellulose, amorphous cellulose, and lignin components. Under the optimized conditions for dilute sulfuric acid hydrolysis of Teff straw (120°C, 4% v/v H2SO4 concentration, 1 : 20 solid to liquid ratio, and 55 min hydrolysis time), we have found a total reducing sugar yield of 26.65 mg/g. The results of validation experiment under the optimum conditions agreed well with model predictions.

Ultrasonic enhancement of xylitol production from sugarcane bagasse using immobilized Candida tropicalis MTCC 184.

This study investigates ultrasonic enhancement of xylitol production from sugarcane bagasse using C. tropicalis MTCC 184 immobilized on PU foam. Initial xylitol yield of 0.53 g/g xylose improved to 0.65 g/g of xylose (in 36 h fermentation) after optimization of medium and fermentation parameters. Optimum values of experimental parameters for maximum xylitol were: yeast extract = 5.78 g/L, (NH4)2SO4 = 3.22 g/L, KH2PO4 = 0.58 g/L, MgSO4·7H2O = 0.57 g/L and temperature = 29.3 °C, initial pH = 6.2, agitation rate = 151 rpm and initial xylose concentration = 20.9 g/L. Application of 37 kHz sonication @10% duty cycle during fermentation at optimum conditions resulted in marked intensification of fermentation kinetics. Xylitol yield of 0.66 g/g of xylose has been obtained in ultrasound-assisted fermentation in just 15 h. Fitting of time profiles of substrates and products to kinetic model has highlighted actual physical mechanisms underlying 2-fold faster kinetics induced by sonication.

Mechanistic investigations in ultrasound-assisted xylitol fermentation.

This study has investigated ultrasound-assisted xylitol production through fermentation of dilute acid (pentose-rich) hydrolysate of sugarcane bagasse using free cells of Candida tropicalis. Sonication of fermentation mixture at optimum conditions was carried out in ultrasound bath (37 kHz and 10% duty cycle). Time profiles of substrate and product in control (mechanical shaking) and test (mechanical shaking + sonication) fermentations were fitted to kinetic model using Genetic Algorithm (GA) optimization. Max. xylitol yield of 0.56 g/g and 0.61 g/g of xylose was achieved in control and test fermentations, respectively. The biomass yield also increased marginally (∼17%) with sonication. However, kinetics of fermentation increased drastically (2.5×) with sonication with 2× rise in xylose uptake and utilization by the cells. With comparative analysis of kinetic parameters in control and test experiments, this result was attributed to enhanced permeability of cell membrane that allowed faster diffusion of nutrients, substrates and products across cell membrane, higher enzyme-substrate affinity, dilution of toxic components and reduced inhibition of intracellular enzymes by substrate.

Kinetic and thermodynamic analysis of dilute acid hydrolysis of sugarcane bagasse.

This study has investigated kinetic and thermodynamic features of dilute acid (2% v/v H2SO4, 1:30 w/v) hydrolysis of sugarcane bagasse. Time profiles of xylose formation in range of 100°-130 °C and treatment period of 0-120 min have been analysed with modified biphasic Saeman model. Generation of glucose, arabinose and inhibitory products (furfural, 5-HMF and acetic acid) have also been analysed. Easy-to-hydrolyse fraction of hemicellulose increased with temperature. Activation energies for hydrolysis and xylose degradation were 60.3 and 83.4 kJ/mol, respectively. Although maximum xylose yield (0.81 g/g hemicellulose) was obtained at 130 °C, significant fraction of xylose was converted to inhibitory products. Thermodynamic analysis revealed ΔH = 57.06 kJ/mol and ΔS = -1.05 kJ/mol for hydrolysis. Moreover, xylose formation is thermodynamically more favoured (ΔG = 468.53 kJ/mol) than degradation (ΔG = 482.17 kJ/mol). Optimum conditions for hydrolysis are: temperature = 120 °C, time = 30 min, xylose yield = 0.76 g/g hemicellulose.