Hydrogen storage using heterocyclic compounds: The hydrogenation of 2-methylthiophene

Alkyl substituted thiophenes are promising candidates for hydrogen carriers, as their dehydrogenation reactions are known to occur under mild conditions. Four types of catalysts, including supported noble metals, bimetallic noble metals, transition metal phosphides and transition metal sulfides, have been investigated for 2-methylthiophene (2MT) hydrogenation and ring-opening. The major products were tetrahydro-2-methylthiophene (TH2MT), pentenes and pentane, with very little C5-thiols observed. The selectivity towards the desired product TH2MT follows the order: noble metals > bimetallics > phosphides > sulfides. The best hydrogenation catalyst was 2% Pt/Al2O3 which exhibited relatively high reactivity and selectivity towards TH2MT at moderate temperatures. Temperature-programmed reaction (TPR) experiments revealed that pentanethiol became the major product, especially with HDS catalysts like CoMoS/Al2O3 and WP/SiO2.