Catalytic transfer hydrogenation of levulinate esters to γ-valerolactone over supported ruthenium hydroxide catalysts

Abstract

Production of g-valerolactone (GVL) from levulinate esters and several alcohols as hydrogen donors via a catalytic transfer hydrogenation (CTH) process was performed over supported ruthenium hydroxide catalysts. Among the catalysts examined, Ru(OH) x supported on high-surface-area, anatase TiO 2 containing highly-dispersed ultrasmall Ru(OH) x nano-clusters was found to be the most active catalyst, which converted levulinate esters to GVL in an almost quantitative yield under mild reaction conditions with low catalyst loading. Addition of heterogeneous bases could afford a faster reaction rate in GVL production by accelerating the following intramolecular dealcoholation step. The catalyst was reusable over repeated catalytic cycles without loss of catalytic performance, making this material a potential candidate for efficient GVL production under ambient reaction conditions.

Engineering UiO‐66 Metal Organic Framework for Heterogeneous Catalysis

“…[53] One of the ways to overcome these issues associated to the harsh reaction conditions needed for hydrogenation of carbonylic groups is the development of new catalysts for the CTH reaction using alcohols as hydrogen donors for this reaction. [54,55] In this context, UiO-66-SO 3 H (60 mol % of SO 3 H functionalized linker by post-synthetic sulfonation of parent UiO-66) exhibited the highest catalytic activity in the CTH reaction of methyl levulinate and 2-butanol to give GVL with 85 % yield at 140°C (Scheme 7). [56] Control experiments revealed that the high catalytic activity of this UiO-66-SO 3 H was the cooperative effect between "arrested" Lewis-basic Zr 6 O 4 (OH) 4 clusters and Brønsted-acidic -SO 3 H sites arranged in a confined nanospace and adjacent each other at close distance, but without undergoing neutralization.…”

Highly Active Catalytic Ruthenium/TiO2 Nanomaterials for Continuous Production of γ‐Valerolactone

“…[51,52,55] For example, 2-propanol wasr eported to be an active hydrogend onor in the transformation of alkyl levulinates, providing good conversion and selectivity. [51,55,56] Herein, we report on highly active, selective, and stable Ru/ TiO 2 catalysts for the continuous-flow conversion of biowastederived methyl levulinate (ML) from industrial activities of the company Avantium. TiO 2 was synthesized through the reversed microemulsion method, whereas deposition of different Ru contents( 1, 2, 3, 5wt%)w as performed by using NaBH 4 as a reducing agent under N 2 bubble production;t he obtainedc atalysts were denoted as1%R u/TiO 2 ,2%R u/TiO 2 ,3%R u/TiO 2 , and 5% Ru/TiO 2 accordingly.T he catalytic performance of the synthesized materials was tested by CTH of ML in aPhoenix reactor from ThalesNano.…”

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

“…The rutile-supported catalyst gave no LA conversion in neither ethanol nor ethanol-water, whereas Ru/TiO 2 (P25) showed much better performance. 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].…”

“…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.…”