(338b) Reaction Mechanism for the Conversion of ?-Valerolactone (GVL) over a Ru Catalyst

Conversion of biomass-derived gamma-valerolactone (GVL) to valuable chemicals has been studied extensively, and understanding the reaction mechanism is very valuable for improving turnover rates and selectivities. Recently, it was shown that, in an aqueous phase over a Ru/C catalyst, GVL could be converted to 1,4-pentanediol, 2-butanol and 2-pentanol in parallel paths¹. Here, we report first-principles density functional calculations, through which we show in detail the reaction pathways of GVL conversion on a Ru(0001) surface². We find that GVL undergoes a ring-opening reaction rather easily, and that the rate-limiting step towards the formation of 1,4-pentanediol and 2-pentanol is the hydrogenation step. The high energy barrier for this step is caused by a strong interaction between Ru and the unsaturated acyl intermediate that is formed after opening the ring. Among all the primary products, formation of the 2-butanol has the smallest activation barrier, while the slowest step is the C-C bond cleavage in the decarbonylation step. We further show that the same acyl intermediate after ring opening of GVL can also be formed by dehydrogenation of 1,4-pentanediol with a moderate activation barrier, which suggests both 2-pentanol and 2-butanol can also be produced in secondary steps.

Acknowledgements

The calculations were performed at NERSC and OU Supercomputing Center for Education and Research (OSCER). We appreciate support from the U.S. DOE through a DOE/EPSCOR grant (DESC0004600).

1. Rozenblit, A.; Avoian, A. J.; Tan, Q.; Sooknoi, T.; Resasco, D. E., Reaction mechanism of aqueous-phase conversion of γ-valerolactone (GVL) over a Ru/C catalyst. Journal of Energy Chemistry 2016, 25 (6), 1008-1014.

2. Bababrik, R. M.; Wang, B.; Resasco, D., Reaction mechanism for the conversion of γ-valerolactone (GVL) over a Ru catalyst: a first-principles study. Industrial & Engineering Chemistry Research 2017, 56 (12), 3217-3222.