The mechanism of catalytic desulfurization of thiophene on molecular sieve catalyst has investigated with quantum-chemistry by using the semi-empirical AM1 calculation method and the static theory. Reaction trends of catalytic desulfurization of thiophene were determined based on the reaction energy needed

which was obtained with the AM1 calculation results of thiophene and possible carbonium ions on transition state.It was validated that the hydrogen transfer reaction played an important role in the catalytic desulfurization process. While thiophene molecules were under the catalytic cracking conditions

their carbonium ions were very active and reacted easily with α-olefins from the paraffin cracking reaction. Further

the catalytic cracking desulfurization took place by hydrogen transfer reactions with paraffin molecules. The hydrogen transfer reactions were exothermic

so a reduced reaction temperature was in favor of the catalytic cracking desulfurization of thiophene.