Titania‐Supported Catalysts for Levulinic Acid Hydrogenation: Influence of Support and its Impact on γ‐Valerolactone Yield

Abstract

A series of titania-supported ruthenium and platinum catalysts was investigated in the levulinic acid hydrogenation towards γ-valerolactone, a key reaction for the catalytic transformation of biomass. It was shown that various morphologies and phases of titania strongly influence the physicochemical and catalytic properties of supported Ru and Pt catalysts in different ways. In the case of the catalyst supported on mixed TiO2 phases, Ru particles are exclusively located on the minority rutile crystallites, whereas such an effect was not observed for platinum. The platinum catalyst activity could be increased when the metal was dispersed on the large surface-area anatase, which was not the case for ruthenium as a result of its agglomeration on this support. The activity of ruthenium on anatase could be increased in two ways: a) when RuO2 formation during catalyst preparation was avoided; b) when pure anatase support material was modified so that it exhibited no microporosity. The obtained results allow a better understanding of the role of the support for Ru and Pt catalysts.

Hydrogenation of levulinic acid to γ-valerolactone over anatase-supported Ru catalysts: Effect of catalyst synthesis protocols on activity

“…The observation on the basis of TEM that well-dispersed Ru on TiO 2 (A100) with small average Ru nanoparticle sizes are attainable for some of the catalysts is surprising considering a recent study on Ru/TiO 2 (A100) [32]. Here, the wet impregnation of ruthenium (Ru(acac) 3 on large surface-area TiO 2 (A100, 83-336 m 2 /g), followed by calcination at 200°C in air and a reduction at similar conditions with hydrogen resulted in an inhomogeneous metal distribution with very large Ru nanoparticles (as seen by TEM) and small ones in the micropores.…”

“…Furthermore, a comparison of the catalytic transfer hydrogenation of levulinate esters using Ru(OH) x /TiO 2 [31], with anatase, rutile and anatase-rutile titanias, showed the anataserutile-based catalyst to perform best (86% for TiO 2 (A); > 99% for TiO 2 (R) and TiO 2 (A75:R25)). Recently, Ruppert et al reported a detailed study on the influence of various TiO 2 supports (anatase, rutile and mixtures thereof) on the Ru-catalyzed LA hydrogenation [32]. A Scheme 1.…”

“…The lower activity of the latter was attributed to the presence of larger Ru particles and agglomerates on the surface and relatively small Ru nanoclusters predominantly found in micropores, thought to be inactive in the hydrogenation reaction. Activity of the anatase-based Ru catalyst could be improved by implementation of either a calcination step of the anatase support before impregnation to reduce the micropore volume or by avoiding a high temperature reduction step during catalyst synthesis by using a mild chemical reduction step [32]. Besides variations in support phase composition, many different synthetic procedures for titania-supported Ru catalyst preparation have been reported varying in the choice of, e.g., metal precursor, impregnation method and activation procedure (Table 1), which all may affect catalyst performance.…”

“…Besides variations in support phase composition, many different synthetic procedures for titania-supported Ru catalyst preparation have been reported varying in the choice of, e.g., metal precursor, impregnation method and activation procedure (Table 1), which all may affect catalyst performance. Wet impregnation is most commonly used method for the synthesis of these Ru/TiO 2 catalysts [19,20,25,29], using Ru precursors such as RuCl 3 , Ru(NO)(NO 3 ) 3 , Ru(acac) 3 , Ru (NH 3 ) 6 Cl 3 or Ru 3 (CO) 12 [19,20,25,[29][30][31][32][33][34][35]. Limited information is available on the effects of these synthesis parameters on LA hydrogenation activity for Ru/TiO 2 catalysts.…”

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

“…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]. The nature of the support and the synthesis method influence the catalytic activity significantly in hydrogenation reactions [35]. Considering the relatively high cost and low availability of ruthenium, catalyst robustness is a key issue for any practical application [36].…”