Abstract
A model biomass-derived phenolic mixture was investigated for its solvent ability for extraction of a South African bituminous coal at temperatures of 300-360 °C. A previous study showed that phenol gave the highest extraction yield of 49.5 wt. % (daf) for bituminous coal at 360 °C, with an oil yield of 26.3 wt. % (daf). The phenolic products produced from sweet sorghum bagasse via an alkaline liquefaction process were identified and reported earlier and a model biomass-derived phenolic mixture was formulated, evaluated and results used in this study. The model mixture gave an extraction yield of 37.1 wt. % (daf) and oil yield of 16.9 wt. % (daf) at 360 °C. This solvent mixture was found to be less effective for high extraction yields when compared to phenol at mild temperatures. This could be due to phenol being a better hydrogen carrier than the solvent mixture during the internal redistribution of hydrogen in the coal. The infrared spectroscopy results of the coal and extraction products obtained using the model mixtures showed similar functional groups. These results demonstrate that the use of a model biomass-derived phenolic mixture has the potential to depolymerize coal and produce high-value chemicals from coal. Keywords: Coal extraction, bituminous coal, depolymerization, biomass-derived solvent.
Highlights
South Africa relies on its abundant coal reserves to meet much of its energy demand
We report in this paper on the utilization of a model biomass-derived phenolic mixture as a solvent for the bituminous coal in comparison to the use of phenol
Characterization of Samples The elemental analysis, X-ray fluorescence (XRF) and maceral composition results as reported earlier for the coal are summarized in Table 1.11 The proximate and ultimate analyses shows that the coal compromises of 34 wt. % volatile matter, 50 wt. % fixed carbon and 81 wt. % carbon content
Summary
South Africa relies on its abundant coal reserves to meet much of its energy demand. Coal provides 79 % of the country’s total energy needs.[1,2] The country’s synthetic liquid fuel production contributes 40 % to the total liquid fuel demand. The indirect coal liquefaction facility in South Africa produces approximately 160 000 barrels of crude oil equivalent a day.[1,7] the currently favoured approach to producing synthetic liquid fuels, coal gasification followed by the Fischer-Tropsch process, poses challenges.[8] For example, this includes the by-product of this process, namely carbon dioxide (CO2), a greenhouse gas associated with global warming.[9] a large amount of hydrogen is used for coal processing through coal liquefaction, which raises cost and energy consumption.[10] In this study, we examine the potential of solvent extraction for coal conversion This process is an alternative coal conversion process that can produce coal-derived liquids without hydrogen and at lower temperatures
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