Influence of Sulfuric Acid on the Performance of Ruthenium‐based Catalysts in the Liquid‐Phase Hydrogenation of Levulinic Acid to γ‐Valerolactone

Abstract

The presence of biogenic or process‐derived impurities poses a major problem on the efficient catalytic hydrogenation of biomass‐derived levulinic acid to γ‐valerolactone; hence, studies on their influence on catalyst stability are now required. Herein, the influence of sulfuric acid as feed impurity on the performance of Ru‐based heterogeneous catalysts, including Ru/ZrO2 and mono‐ and bimetallic Ru‐on‐carbon catalysts in dioxane as solvent, was investigated. The carbon‐supported Ru catalysts proved to be very sensitive to minor amounts of sulfuric acid. In stark contrast, Ru/ZrO2 showed a remarkable stability in the presence of the same impurity, which is attributed to the sulfate‐ion adsorption capacity of the support. Preferential sulfate adsorption onto the surface of ZrO2 effectively protects the Ru active phase from deactivation by sulfur poisoning. A simple catalyst regeneration strategy was effective in removing adsorbed impurities, allowing efficient catalyst recycling.

Phase‐Dependent Stability and Substrate‐Induced Deactivation by Strong Metal‐Support Interaction of Ru/TiO2 Catalysts for the Hydrogenation of Levulinic Acid

“…As part of the transition to a more sustainable chemical industry, the use of non‐edible biomass as feedstock for the production of renewable chemical building blocks, or platform chemicals, is desired . Two platform molecules of particular potential are biomass‐derived levulinic acid (LA) and γ‐valerolactone (GVL), both of which received much attention given their relative ease of synthesis and manifold potential applications ,. Indeed, LA can be obtained in one step from lignocellulosic biomass by a simple hydrolysis process and can be converted to GVL in another single step, with GVL finding possible application as a green solvent, food additive and as intermediate for the production of bulk polymers and advanced biofuels ,…”

“…Next to productivity, long‐term stability is equally important for a catalyst, but typically receives much more limited attention . When run in the liquid phase, the catalyst is exposed to highly polar, elevated temperature LA hydrogenation conditions, with the added difficulty of having an acidic substrate .…”

“…As a result of these harsh conditions, catalysts can be expected to deactivate as a result of metal sintering, leaching, support collapse or destruction . In addition, reactive intermediates can polymerize to form carbonaceous deposits and biogenic or process‐derived impurities can poison the catalyst, with both these processes also leading to deactivation …”

“…[1] Two platform molecules of particular potential are biomass-derived levulinic acid (LA) and γvalerolactone (GVL), both of which received much attention given their relative ease of synthesis and manifold potential applications. [2,3] Indeed, LA can be obtained in one step from lignocellulosic biomass by a simple hydrolysis process [4] and can be converted to GVL in another single step, with GVL finding possible application as a green solvent, [5] food additive [6] and as intermediate for the production of bulk polymers and advanced biofuels. [4,7] The production of GVL by hydrogenation of LA has received much attention, having been extensively studied both in the gas and liquid phase and with different reductants, including molecular hydrogen , formic acid and alcohols.…”

“…[19] Next to productivity, long-term stability is equally important for a catalyst, but typically receives much more limited attention. [3] When run in the liquid phase, the catalyst is exposed to highly polar, elevated temperature LA hydrogenation conditions, with the added difficulty of having an acidic substrate. [4] As a result of these harsh conditions, catalysts can be expected to deactivate as a result of metal sintering, leaching, support collapse or destruction.…”