Densification of biorefinery schemes by H-transfer with Raney Ni and 2-propanol: A case study of a potential avenue for valorization of alkyl levulinates to alkyl γ-hydroxypentanoates and γ-valerolactone

•A highly flexible approach for valorization of alkyl levulinates in regard to the control over the product selectivity is demonstrated.•The features distinguishing the energetics of the transfer vs. conventional hydrogenation of methyl levulinate is addressed.•The thermal stability of methyl γ-hydroxypentanoate in the absence and in the presence of solid catalysts is examined.•The stability of Raney Ni in the conversion of several alkyl levulinates is assessed.•A process concept based on H-transfer conversion of alkyl levulinates is also proposed.

Alkyl γ-hydroxypentanoates and γ-valerolactone are promising platform chemicals that can be produced from alkyl levulinates in the lignocellulosic biorefinery. Accordingly, this report aims to provide in-depth insight into the molecular aspects involved in the conversion of alkyl levulinates by H-transfer catalyzed by Raney Ni and using 2-propanol as an H-donor and solvent. We demonstrate this methodology as a highly flexible approach in regard to the high degree of control over the product selectivity. In fact, up to 90% yield of alkyl γ-hydroxypentanoates is obtained at temperatures as low as 298 K. In turn, 94% yield of γ-valerolactone is achieved at 393 K. In order to shed light on the fundamental aspects of this chemical route, we address: (1) the energetics of the transfer vs. conventional hydrogenation of methyl levulinate, (2) the thermal stability of methyl γ-hydroxypentanoate in the absence and in the presence of solid catalysts, and (3) the stability of Raney Ni in the conversion of several alkyl levulinates. Lastly, a process concept based on the current results is also proposed. This concept provides a comprehensive overview of the practical possibilities of this process as part of the lignocellulose-based biorefineries.

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