Exploring the ruthenium catalysed synthesis of γ-valerolactone in alcohols and utilisation of mild solvent-free reaction conditions

Abstract

Levulinic acid and alkyl-levulinates have been hydrogenated using a range of supported catalysts. The different reaction outcomes obtained in alternate solvents have been rationalized and the influence of varying catalyst supports examined. A range of solvent free conditions have been investigated with complete LA conversion obtained at temperatures as low as 25 °C

Highly Selective Hydrogenation of Levulinic Acid to γ-Valerolactone Over Ru/ZrO2 Catalysts

“…All samples are basically agglomerates of more or less rounded nanoparticles, with relatively larger size for A and D compared to B and C. Note that B and C are prepared by the calcination of ZrOH after loading RuCl 3 while A and D were prepared by loading RuCl 3 on pre-calcined ZrOH. The results are analogous to the ones we reported elsewhere for WO x /ZrO 2 catalysts, [17] where the calcination of WO x doped ZrOH yielded smaller nanoparticles compared to the calcined, undoped ZrOH. More insight is obtained from a detailed analysis of selected representative high resolution images (see Fig.…”

“…We must ensure that we hydrogenate only the keto group, enabling the cyclisation to the lactone product. Previous studies have shown that both the size and the dispersion of the ruthenium sites are crucial, as well as the properties of the support [17,21,32,33]. This is because the hydrogenation of keto group is catalysed by a combined effort of both the ruthenium active site and the support.…”

“…Another parameter that influences catalyst performance is the metal dispersion on the surface. In general, smaller Ru particles are more active, but the catalyst is less robust [17,19,31,33]. Also, it is reported in literature that mixing acid catalysts with Ru metal catalysts promoted hydrogenation and bifunctional catalysts are active and recyclable in aqueous solution [18,34].…”

“…It is produced easily and economically from biomass, [10][11][12][13][14][15] and can be converted into many valuable chemicals. These include γ-valerolactone (GVL, 2), 1,4-pentanediol, methyltetrahydrofuran, and valeric acid and esters [16,17]. Of these, the stable and non-toxic GVL has already several applications: it can be used directly as a fuel additive or as a precursor for fuels and chemicals and as a renewable solvent [10,[18][19][20][21].…”

“…The problem is that small changes in any number of parameters often cause large variance in catalyst performance. Using different supports and even using different phases of the same compound [30][31][32] alters conversion and yield [17]. Another parameter that influences catalyst performance is the metal dispersion on the surface.…”