Chemical Thermodynamics and Kinetics of Thiophenic Sulfur Removed from Coal by Microwave: A Density Functional Theory Study

Abstract

In this study, the feasibility of catalyzing removel of thiophenic sulfur from coal with microwave irradiation was evaluated by dielectric properties test, and the chemical thermodynamics and kinetics of thiophenic sulfur in coal with microwave irradiation was obtained by density functional theory calculation. Results suggested that the imaginary parts of dielectric constants ε" of benzothiophene and dibenzothiophene are higher than those of coal samples, meaning that thiophenic sulfur compounds in the coal can be selectively heated by microwave. Linear Synchronous Transit/Quadratic Synchronous Transit method indicated that the microwave field catalyzed the removel of thiophenic sulfur mainly affected the breaking of C−H and C-C bonds, thus reducing the energy barrier (Eb) and activation energy (Ea) and increasing the logarithm of rate constants (lnk) in the desulfurization process. Moreover, the optimal removel path of thiophenic sulfur changed from β(a) to α(b), and sulfur-containing products changed from carbon monosulfide (CS) to thioketene(C2H2S) after applied microwave field. These findings reveal the catalytic mechanism of microwave on the removel of thiophenic sulfur in coal from hydrogen migration and reaction changes, which is conducive to the clean utilization of coal.

Microwave absorption properties and quantum chemistry of organic sulfur compounds in coal

“…18 Currently, the application of quantum chemical calculations in coal is in the development stage, and some scholars use quantum chemical to study the reaction mechanism of action related to coal. Yin et al 19 analyzed the main interactions among the structures of ammonia nitrogen, phenol, and lignite by quantum chemical simulations and found the adsorption mechanism between lignite and typical fractions in wastewater. Du et al 20 studied the migration of thiophene sulfur under microwave irradiation based on density flooding theory calculations and found that both the energy potential and activation energy of the thiophene sulfur desulfurization limiting step are reduced, so that desulfurization may occur through catalytic C-H and C-C bond breakage.…”