Production of Furfural From Lignocellulosic Biomass Using Sulfonated Carbon-Based Solid Acid Catalysts
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There is an aching desire to desist from the use of fossil fuel energy sources due to their major contribution to environmental degradation. Hydro, wind, and solar energy may serve as the much-needed alternative energy supply sources to fossil fuels however biomass will be the major alternative source for platform chemicals. Furfural is one of the 12 leading value-added chemicals identified by the US Department of Energy (DOE). It is of importance in the industrial sector, having applications such as; the removal of aromatics from diesel fuel and lubricant refining, and being a platform chemical from which a vast number of other chemicals are produced. The factors that influence furfural yield and selectivity are the catalyst used, solvent, catalysts loading, time, and temperature of the hydrolysis reaction. Farmers on the prairies have had a difficult time gathering and disposing of flax straws. Farmers burn this straw as a means of disposal due to its strong fiber and difficult decomposition. Every year, about 670,000 tonnes of flax straw are burned or destroyed on the prairies. This research work was aimed at the development of a sulfonated carbon-based solid acid catalyst for the production of furfural via hydrothermal hydrolysis of flax straw biomass. Glu-TsOH-Zr catalyst was developed, characterized by TGA, N2 -Physisorption, NH3-TPD, XRD, SEM, and FTIR, and then tested for its capacity in furfural production from flax straw biomass and pure xylose. Glu-TsOH-Ti and Glu-TsOH, replicated from literature were also characterized and applied for furfural production. The effect of residence time (0-120 mins), reaction temperature (170-210°), and the catalyst mass (0.25 -1g) on the furfural yield were also studied. Finally, the methyl tetrahydrofuran solvent ratio for optimal furfural production in a biphasic system was determined and a kinetic study was performed. The results presented that the Glu-TsOH-Zr catalyst had a good potential for improving furfural yield. The order of the catalysts based on the percentage of xylose conversion and furfural yield from pure xylose feed was Glu-TsOH-Ti > Glu-TsOH-Zr > Glu-TsOH. A reaction temperature of 190°C, a residence time of 120 minutes, and a catalyst mass of 1g (0.3 catalyst mass/flax straw mass) were found to be the best-operating conditions for furfural formation from flax straw biomass. The largest influence on furfural yield was determined to be temperature, followed by catalyst mass, and then reaction time. Furthermore, the catalyst with the highest overall acidity, surface area, and pore size (Glu-TsOH-Ti) also yielded the most furfural. The addition of an organic phase enhanced furfural yield, and the catalyst was reusable for up to three cycles with little drop in furfural yield; however, by the fourth cycle, there was a significant decrease in furfural yield. A first-order irreversible series reaction that started with the creation of furfural from xylose and ended with furfural degradation into degradation products was proposed as a kinetic model for the empirical rate data. The reaction leading to furfural production had higher activation energy (222.18kJ/mol) than the reaction leading to degradation products (104.56kJ/mol), showing that the furfural production reaction is more temperature-sensitive than the degradation reaction. Finally, the kinetic model's average absolute deviation (5.9%) indicated that it was an excellent fit for the reaction series.