The molecular conformations of thiophene

3-methylthiophene and 2

5-bimethylthiophene were investigated by using the semi-empirical calculation AM1 method and the static theory. Their adsorption rate on the molecular sieve catalysts surface and the stability of their carbonium ions were then obtained based on the molecular simulation on these molecules from their dipole moment

2-dimensional electrostatic potential energy contours and 3-dimensional electrostatic potential energy isosurface. Also the curves of total potential energies for the further reactions of the carbonium ions of thiophene

3-methylthiophene and 2

5-bimethylthiophene were obtained by this way. This could be used as a criterion to determine which cracking desulfurization rate is faster than others among thiophene

3-methylthiophene and 2

5-bimethylthiophene. The results showed that the fastest one is 2

5-bimethylthiophene

and secondly 3-methylthiophene. This was in good agreement with the experimental data obtained in a fixed bed micro-reactor for catalytic cracking of thiophene

3-methylthiophene and 2

5-bimethylthiophene.