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Lignin, a readily available form of biomass with a potential source of aromatic chemical compounds, has not been fully utilized due to its complex structure. Hence, this study aims to elaborate and optimize the effects of parametric microwave conditions for the catalytic degradation of lignin model compounds. In addition to that, 41 types of imidazolium-based Ionic liquids were employed for the conversion of lignin model compounds such as guaiacol and benzyl phenyl ether. The microwave-assisted conversion of lignin model compounds in imidazolium-based ionic liquids was performed at optimum applied microwave power 700 W and 30-min irradiation time. The percentages conversion and yield were quantified using high-performance liquid chromatography (HPLC) analysis. Results revealed that the chloride anion-based ionic liquids exhibited better nucleophilic behavior and catalyzed the cleavage of ether-based compounds efficiently under microwave irradiation. Among the imidazolium-based ionic liquids, 1H-methylimidazolium chloride ([1H-MIM][Cl]) exhibited better performance with guaiacol conversion and catechol yield of 99% and 81%, respectively. Therefore, the microwave-assisted technique was found to be more promising than conventional methods for the ionic liquid-based catalytic degradation of lignin model compounds.

The dependence on fossil fuel in recent years has accentuated the importance of renewable resources such as biomass. Lignocellulosic biomass consisting mainly of cellulose, hemicellulose, and lignin, can be potentially converted into biochemicals and biofuels. Ionic liquid (IL) has been proven as an efficient and green solvent for biomass dissolution and further processing. Nonetheless, conventionally employed IL treatment requires a longer time and higher temperature making the overall process cost-intensive and time-consuming. The aim of the current research work is to develop a direct probe sonication assisted IL method for rapid biomass dissolution without any external heating. The effect of several experimental parameters on biomass dissolution such as acoustic power (20–60%), sonication time (10–70 min), biomass particle size (500–125 µm), initial sample loading (5, 7.5 and 10%), volume of sample (3, 6 and 9 mL), and types of IL were investigated and optimized. The lignocellulosic biomass and regenerated biomaterials were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, Fourier electron scanning electron microscope, and powder x-ray diffraction to study the effect of probe sonication assisted IL treatment. The ultrasonic cavitation had significantly shortened the time for complete lignocellulose dissolution and considerably altered the thermophysical properties of regenerated cellulose-rich materials. The acetate-based IL showed the best performance, able to fully dissolved bamboo biomass in just 40 min in the probe sonication. In conclusion, probe sonication is an efficient method at lab scale which might need further development in technology to make the process economical at the industrial level for lignocellulosic biomass treatment.

Due to the substantial usage of fossil fuels, the utilization of lignocellulosic biomass as renewable sources for fuels and chemical production has been widely explored. The dissolution of lignocellulosic biomass in proper solvents is vital prior to the extraction of its important constituents, and ionic liquids (ILs) have been found to be efficient solvents for biomass dissolution. However, the high viscosity of ILs limits the dissolution process. Therefore, with the aim to enhance the dissolution of lignocellulosic biomass, a series of new ether-functionalized ILs with low viscosity values were synthesized and characterized. Their properties, such as density, viscosity and thermal stability, were analyzed and discussed in comparison with a common commercial IL, namely 1-butyl-3-methylimidazolium chloride (BMIMCl). The presence of the ether group in the new ILs reduces the viscosity of the ILs to some appreciable extent in comparison to BMIMCl. 1-2(methoxyethyl)-3-methylimidazolium chloride (MOE-MImCl), which possesses the lowest viscosity value among the other ether-functionalized ILs, demonstrates an ability to be a powerful solvent in the application of biomass dissolution via the sonication method. In addition, an optimization study employing response surface methodology (RSM) was carried out in order to obtain the optimum conditions for maximum dissolution of biomass in the solvents. Results suggested that the maximum biomass dissolution can be achieved by using 3 weight% of initial biomass loading with 40% amplitude of sonication at 32.23 min of sonication period.

The search of new sustainable energy sources based on renewable biomass feedstocks from lignocellulose biomass constituents namely cellulose, hemicellulose and lignin is a global effort to replace fossil fuel sources. Several conventional methods that have been used for extracting constituents via biomass dissolution include acid and base hydrolyses. However, these processes offer several drawbacks and therefore cannot be considered as environmental-friendly. This study investigates the dissolution of bamboo biomass from species Gigantochloa scortechini in low-viscosity ether-functionalized ionic liquids (ILs) by employing direct probe sonication method. Two ether-functionalized ILs which are MOE-MImCl and MOE-BImCl have been synthesized and characterized and their performance towards biomass dissolution have been tested. Results show that both MOE-MImCl and MOE-BImCl are able to dissolve the biomass with percentage dissolution of 88.1% and 28.1%, respectively with 20 minutes dissolution time. FTIR analyses were also done on both untreated biomass and regenerated biomass. The recyclability of the ILs for dissolving biomass was also tested and results show that the percentage of biomass dissolved in the recycled ILs reduce by approximately 10% of the original values.

Ionic liquids (ILs) have been proven to be one of effective approaches for biomass dissolution. In this work, direct bamboo biomass dissolution in IL under probe sonication technique was studied. An ether-functionalized IL was synthesized and used in this study. Dissolution of biomass was observed under microscope. It was found that the presence of ether group in the IL decreased time up to 60% for complete biomass dissolution as compared to non-functionalized IL. Regenerated cellulose rich materials (CRM) recovered from both ether and non-functionalized IL treatment were characterized using FTIR, SEM and TGA. Regenerated biomass showed slight reduction on thermal stability following dissolution.

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 10 min. 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 3 min. 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.

Lignin, a heterogenous polymer which presents about 20-30 % in lignocellulose emerged as promising feedstock for the production of specialty chemicals. However, due to lignocellulose recalcitrance structure, the pretreatment is necessary to obtain efficient utilization of biomass. In this work, the preliminary study was carried out focusing on the properties lignin extracted from bamboo (Gigantochloa scortcheninii) using alkali and ionic liquid pretreatment. It was discovered that about 42% and 11% of acid-insoluble lignin has been extracted from alkali and IL pretreatment respectively. The degradation onset temperature of alkali and ionic liquid extracted lignin were found to be 262.20 and 172.41°C. FTIR spectra analysis showed the characteristic peaks of lignin for both samples. Desirable products such as aldehydes, phenol, hydrocarbons and aromatics were identified from pyrolysis GC-MS

A new class of dual functionalized imidazolium based ionic liquid (IL) namely 3-(2-cyano-ethyl)-1-(2-ethoxy-ethyl)-3-imidazolium bromide [CNEIM][Br], was synthesized and characterized to study their potential in bamboo dissolution. The chemical structure for the IL was characterized using NMR ( 1 H and 13 C). Thermal properties, surface morphology and functional group of the native bamboo and IL treated bamboo were analyzed by Thermal Gravimetric Anaylysis (TGA), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) respectively. The new IL was able to dissolve up to 5wt% of bamboo biomass within 48 hours and 100°C.