Support-Activity Relationship in Heterogeneous Catalysis for Biomass Valorization and Fine-Chemicals Production

Heterogeneous catalysts are progressively expanding their field of application, from high-throughput reactions for traditional industrial chemistry with production volumes reaching millions of tons per year, a sector in which they are key players, to more niche applications for the production of fine chemicals. These novel applications require a progressive utilization reduction of fossil feedstocks, in favor of renewable ones. Biomasses are the most accessible source of organic precursors, having as advantage their low cost and even distribution across the globe. Unfortunately, they are intrinsically inhomogeneous in nature and their efficient exploitation requires novel catalysts. In this process, an accurate design of the active phase performing the reaction is important; nevertheless, we are often neglecting the importance of the support in guaranteeing stable performances and improving catalytic activity. This review has the goal of gathering and highlighting the cases in which the supports (either derived or not from biomass wastes) share the worth of performing the catalysis with the active phase, for those reactions involving the synthesis of fine chemicals starting from biomasses as feedstocks.

Reaction Route Selection for Cellulose Hydrogenolysis into C2/C3 Glycols by ZnO-Modified Ni-W/β-zeolite Catalysts

A β-zeolite-supported nickel and tungsten catalyst (Ni-W/β) was employed to generate C2/C3 glycols (ethylene and propylene glycols) in a satisfactory yield from cellulose. After optimizing the acidity of the support, the Ni-W synergy and the co-catalyst, the yield of C2/C3 glycols reached 70.1% (C %), with propylene glycol accounting for 51.1% of the product. This performance was attributed to the effective control of the major reaction steps, namely, hydrolysis, isomerization, retro-aldol condensation and hydrogenation, by the tailored Ni-W-ZnO/β catalyst. The characterization and reaction results indicated that the cellulose hydrolysis step was promoted by the appropriate acidic sites of the β-zeolite, and the reaction routes to C2/C3 glycols were influenced by the mass loading of Ni-W through the synergy of nickel and tungsten oxide, in which Ni is effective in the hydrogenation while W facilitates bond cleavage via a retro-aldol condensation (C6 to C2/C3). Moreover, with the leaching of metal during four cycles of reuse, the catalytic performance was also influenced by the synergy of Ni and W. In addition, the isomerization of glucose to fructose was promoted by ZnO and afforded a high yield of propylene glycol.

A weakly basic Co/CeOx catalytic system for one-pot conversion of cellulose to diols: Kungfu on eggs

A controlled, weakly basic Co/CeO_x catalyst was designed for one-pot conversion of cellulose to ethylene glycol (EG) and 1,2-propylene glycol (1,2-PG) to achieve near-equivalent yield. The efficiency is mainly attributed to Coⁿ⁺-O_x-Ce³⁺ base-acid pairs that hindered humin formation by ensuring a precise balance across the various steps of the reaction.

From a Sequential Chemo-Enzymatic Approach to a Continuous Process for HMF Production from Glucose

Notably available from the cellulose contained in lignocellulosic biomass, glucose is a highly attractive substrate for eco-efficient processes towards high-value chemicals. A recent strategy for biomass valorization consists on combining biocatalysis and chemocatalysis to realise the so-called chemo-enzymatic or hybrid catalysis. Optimisation of the glucose conversion to 5-hydroxymethylfurfural (HMF) is the object of many research efforts. HMF can be produced by chemo-catalyzed fructose dehydration, while fructose can be selectively obtained from enzymatic glucose isomerization. Despite recent advances in HMF production, a fully integrated efficient process remains to be demonstrated. Our innovative approach consists on a continuous process involving enzymatic glucose isomerization, selective arylboronic-acid mediated fructose complexation/transportation, and chemical fructose dehydration to HMF. We designed a novel reactor based on two aqueous phases dynamically connected via an organic liquid membrane, which enabled substantial enhancement of glucose conversion (70%) while avoiding intermediate separation steps. Furthermore, in the as-combined steps, the use of an immobilized glucose isomerase and an acidic resin facilitates catalyst recycling.

Bio-based acrylic acid from sugar via propylene glycol and allyl alcohol

Propylene glycol is converted to acrylic acid via dehydration to allyl alcohol. A process flow scheme is proposed, based on distillation resistance.

Kinetics study of the Ru/C-catalysed hydrogenolysis of polyols – insight into the interactions with the metal surface

Kinetic analysis of stereoisomerization, decarbonylation and deoxygenation provides insight into the reactivity and dynamics of polyols on Ru-surfaces.

Lanthanum oxycarbonate modified Cu/Al2O3 catalysts for selective hydrogenolysis of glucose to propylene glycol: base site requirements

Moderate and strong base sites play a key role in glucose hydrogenolysis over bifunctional Cu–La₂O₂CO₃/Al₂O₃ catalysts.