Glycerol Hydrogenolysis to 1,2-Propanediol over Novel Cu/ZrO2 Catalysts

Giuseppina Luciani,Giovanna Ruoppolo,Almerinda Di Benedetto,Valentina Gargiulo,Michela Alfè,Gianluca Landi

doi:10.3390/catal12010072

Giuseppina Luciani, Giovanna Ruoppolo + Show 4 more

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https://doi.org/10.3390/catal12010072

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Abstract

Glycerol is the main by-product of biodiesel production; its upgrading to more valuable products is a demanding issue. Hydrogenolysis to 1,2-propanediol is one of the most interesting processes among the possible upgrading routes. In this study, we propose novel copper/zirconia catalysts prepared by advanced preparation methods, including copper deposition via metal–organic framework (MOF) and support preparation via the sol–gel route. The catalysts were characterized by N2 physisorption, X-ray diffraction, Scanning Electron Microscopy, H2-TPR and NH3-TPD analyses and tested in a commercial batch reactor. The catalyst prepared by copper deposition via MOF decomposition onto commercial zirconia showed the best catalytic performance, reaching 75% yield. The improved catalytic performance was assigned to a proper combination of redox and acid properties. In particular, a non-negligible fraction of cuprous oxide and of weak acid sites seems fundamental to preferentially activate the selective pathway. In particular, these features avoid the overhydrogenolysis of 1,2-propanediol to 1-propanol and enhance glycerol dehydration to hydroxyacetone and the successive hydrogenation of hydroxyacetone to 1,2-propanediol.

Highlights

Glycerol is the main by-product of biodiesel production, accounting for about 10 wt% of produced biodiesel [1].In order to be used for food and/or pharmaceutical applications, crude glycerol should be upgraded and purified to almost 100% purity
We propose novel copper/zirconia catalysts prepared by advanced preparation methods, including copper deposition via metal–organic framework (MOF) and support preparation via the sol–gel route
A non-negligible fraction of cuprous oxide and of weak acid sites seems fundamental to preferentially activate the selective pathway. These features avoid the overhydrogenolysis of 1,2-propanediol to 1-propanol and enhance glycerol dehydration to hydroxyacetone and the successive hydrogenation of hydroxyacetone to 1,2-propanediol

Summary

Introduction

Glycerol is the main by-product of biodiesel production, accounting for about 10 wt% of produced biodiesel [1].In order to be used for food and/or pharmaceutical applications, crude glycerol should be upgraded and purified to almost 100% purity. Glycerol valorization processes to added-value products have been proposed in order to improve the sustainability of biodiesel production [3,4,5,6,7,8,9] In this framework, the conversion of glycerol to 1,2-propanediol (1,2-PDO) has been receiving great attention due to the broad use of 1,2-PDO as a chemical platform [10], which is largely employed as a deicing additive, cosmetic solvent, and hydraulic fluid as well as reactant in polymer synthesis including unsaturated polyester resins and polyurethanes [11,12]. The conversion of glycerol to 1,2-propanediol (1,2-PDO) has been receiving great attention due to the broad use of 1,2-PDO as a chemical platform [10], which is largely employed as a deicing additive, cosmetic solvent, and hydraulic fluid as well as reactant in polymer synthesis including unsaturated polyester resins and polyurethanes [11,12]. 1,2-PDO is currently produced at an industrial scale by the hydrolysis of propylene oxide, which is a building block derived from non-renewable oil resources.

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