Zahoor Ullah

Synthesis, characterization and the effect of temperature on different physicochemical properties of protic ionic liquids

In this work, eleven protic ionic liquids (PILs) containing different cations and anions were prepared and their physicochemical properties were measured. The structures of all the PILs were confirmed using NMR, and elemental analysis (CHNS) was carried out. The physicochemical properties such as density, surface tension, viscosity and thermal degradation behaviour were measured, and the effect of the cations/anions was investigated. The density and viscosity were measured within the temperature range of 293.15–373.15 K at atmospheric pressure. The thermal expansion coefficient values were calculated from the density data. Surface tension was measured in the temperature range of 293.15 to 353.15 K and the values were used to estimate the surface entropy and enthalpy of the ionic liquids at 303.15 K. The boiling and critical temperature are also estimated according to the Eotvos and Rebelo methods. The refractive indices were measured within the temperature range of 293.15 to 323.15 K. The thermal gravimetric analysis was performed in the temperature range of 373.15–773.15 K.

A new approach of probe sonication assisted ionic liquid conversion of glucose, cellulose and biomass into 5-hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) has been identified as a promising biomass-derived platform chemical. In this study, one pot production of HMF was studied in ionic liquid (IL) under probe sonication technique. Compared with the conventional heating technique, the use of probe ultrasonic irradiation reduced the reaction time from hours to minutes. Glucose, cellulose and local bamboo, treated with ultrasonic, produced HMF in the yields of 43%, 31% and 13% respectively, within less than 10min. The influence of various parameters such as acoustic power, reaction time, catalysts and glucose loading were studied. About 40% HMF yield at glucose conversion above 90% could be obtained with 2% of catalyst in 3min. Negligible amount of soluble by-product was detected, and humin formation could be controlled by adjusting the different process parameters. Upon extraction of HMF, the mixture of ionic liquid and catalyst could be reused and exhibited no significant reduction of HMF yield over five successive runs. The purity of regenerated [C4C1im]Cl and HMF was confirmed by NMR spectroscopy, indicating neither changes in the chemical structure nor presence of any major contaminants during the conversion under ultrasonic treatment. 13C NMR suggests that [C4C1im]Cl/CrCl3 catalyses mutarotation of α-glucopyranose to β-glucopyranose leading to isomerization and finally conversion to HMF. The experimental results demonstrate that the use of probe sonication technique for conversion to HMF provides a positive process benefit.

Efficient conversion of lignocellulosic biomass to levulinic acid using acidic ionic liquids

In the present research work, dicationic ionic liquids, containing 1,4-bis(3-methylimidazolium-1-yl) butane ([C4(Mim)2]) cation with counter anions [(2HSO4)(H2SO4)0], [(2HSO4)(H2SO4)2] and [(2HSO4)(H2SO4)4] were synthesised. ILs structures were confirmed using 1H NMR spectroscopy. Thermal stability, Hammett acidity, density and viscosity of ILs were determined. Various types of lignocellulosic biomass such as rubber wood, palm oil frond, bamboo and rice husk were converted into levulinic acid (LA). Among the synthesized ionic liquids, [C4(Mim)2][(2HSO4)(H2SO4)4] showed higher % yield of LA up to 47.52 from bamboo biomass at 110°C for 60min, which is the better yield at low temperature and short time compared to previous reports. Surface morphology, surface functional groups and thermal stability of bamboo before and after conversion into LA were studied using SEM, FTIR and TGA analysis, respectively. This one-pot production of LA from agro-waste will open new opportunity for the conversion of sustainable biomass resources into valuable chemicals.

Preparation of Biodiesel from Waste Cooking Oil Catalyzed by Basic Ionic Liquid

A basic ionic liquid tetra butyl phosphonium hydroxide was applied as a catalyst for biodiesel production from waste cooking oil by transesterification process and the yield 82% was achieved. The ionic liquid was used four times without any dramatic decrease in ester yield. And the methyl ester was checked by 1H NMR. Keywords: Biodiesel, waste cooking oil, transesterification, ionic liquid.

Swelling mechanism of urea cross-linked starch–lignin films in water

ABSTRACT Coating fertilizer particles with thin films is a possibility to control fertilizer release rates. It is observed that novel urea cross-linked starch–lignin composite thin films, prepared by solution casting, swell on coming into contact with water due to the increase in volume by water uptake by diffusion. The effect of lignin content, varied from 0% to 20% in steps of 5% at three different temperatures (25°C, 35°C and 45°C), on swelling of the film was investigated. By gravimetric analysis, the equilibrium water uptake and diffusion coefficient decrease with lignin content, indicating that the addition of lignin increases the hydrophobicity of the films. When temperature increases, the diffusion coefficient and the amount of water absorbed tend to increase. Assuming that swelling of the thin film is by water uptake by diffusion, the diffusion coefficient is estimated. The estimated diffusion coefficient decreases from 4.3 to 2.1 × 10−7 cm2/s at 25°C, from 5.3 to 2.9 × 10−7 cm2/s at 35°C and from 6.2 to 3.8 × 10−7 cm2/s at 45°C depending on the lignin content. Activation energy for the increase in diffusion coefficient with temperature is observed to be 16.55 kJ/mol. An empirical model of water uptake as a function of percentage of lignin and temperature was also developed based on Fick’s law.