Mechanistic Approaches toward Rational Design of a Heterogeneous Catalyst for Ring-Opening and Deoxygenation of Biomass-Derived Cyclic Compounds

Abstract

Technologies for the processing of lignocellulosic biomass into fuels and chemicals are generally focused on selective chemical transformation of the three different types of constituents: cellulose, hemicellulose and lignin. In this regard, heterogeneous catalytic reactions are employed to defunctionalize and upgrade the platform molecules obtained selectively from these constituents. Herein, a selection of studies are discussed which are adapted to deoxygenate and valorize the biomass-derived platform molecules with a specific focus on understanding the reaction mechanisms and rational design of a heterogeneous catalyst. The selection of the deoxygenation process constituted a combination of two or three reactions. For example, ring-opening reactions of the cyclic compounds are studied with decarboxylation, dehydration, hydrogenation and/or Diels–Alder reaction carried out on metal, acid and/or oxide catalysts. The platform molecules studied here include an array of saturated lactones, 2-pyrones, cyclic ethers, furans and phenolic compounds. In the study of lactones, mechanistic insights are provided to understand the selectivity trend over the Brønsted and Lewis acid catalysts for ring-opening and decarboxylation reactions leading to the formation of α-olefins. For 2-pyrones, the integrated bio- and chemo-catalytic process is studied in which a 2-pyrone molecule obtained from fermentation media may undergo Diels–Alder, hydrogenation combined with ring-opening, decarboxylation and dehydration reactions to yield the target product. Ring-opening studies on cyclic ethers, including furanic compounds, are focused on mechanistic observations in the C–O hydrogenolysis reaction, leading to the design of bimetallic alloys to produce terminal diols and carboxylic acids. In extension to this, rational thoughts on the design of bimetallic catalysts are elucidated in the hydrodeoxygenation of the phenolic compounds.

Tracing the reactivity of single atom alloys for ethanol dehydrogenation using ab initio simulations

“…For decades, researchers in reaction engineering have been intrigued by the idea of rational catalyst design to achieve the desired catalytic activity. [1][2][3][4][5] The century old Sabatier principle 6 has guided this quest in heterogeneous catalysis, wherein the key reaction descriptors are sought after on the catalyst surface, so as to design the surface for optimum binding of the descriptor species, yielding maximum turnovers. Towards this, in silico catalyst design is propelled by ab initio quantum mechanical simulations, to map turnover frequencies (TOFs) with simplified descriptors, such as the binding energy of the carbon or oxygen atoms on the transition metal catalyst surface.…”

Reductive Conversion of Biomass-Derived Furancarboxylic Acids with Retention of Carboxylic Acid Moiety

“…Other production methods of adipic acid from biomass include (i) conversion of hydrocarbons produced by BTL (biomass to liquid; combination of biomass gasification and Fischer-Tropsch synthesis) [77] in petrochemical processes, (ii) production of K-A oil by reduction of biomass pyrolysis oil (bio-oil) [78][79][80][81][82][83], (iii) direct production of adipic acid by fermentation [84], (iv) hydrodeoxygenation of sugar acids produced by oxidation of sugars [85][86][87][88][89][90][91][92], (v) extension of carbon chain of C5 biomass-derived platform chemicals such as γ-valerolactone by hydroformylation or carboxylation [93][94][95][96], and (vi) oxidative cleavage of 1,2-difunctionalized cyclohexanes produced by reduction of bio-oil [97][98][99][100]. Low yield from raw biomass (methods (i), (ii), (iii) and (vi)) and large number of steps (methods (i), (ii), (9) (v) and (vi)) are the main problems of these methods. The FDCA-based systems are highly competitive to these systems except (iv) in these views.…”

“…Furfural and HMF have reactive unsaturated furan ring and aldehyde group, and the conversion of furfural and HMF has been also intensively investigated by using various reactions such as reduction, oxidation, addition and condensation. While reductive conversion has been the most investigated because of the high unsaturation of furfural and HMF and variety of products [4,[6][7][8][9][10], oxidation of the side chain of furfural and HMF can give furancarboxylic acids, namely 2-furancarboxylic acid (furoic acid; FCA) and 2,5-furandicarboxylic acid (FDCA), respectively, relatively easily (Fig. 1).…”

Direct Oxidation of Cyclohexane to Adipic Acid by a WFeCoO(OH) Catalyst: Role of Brønsted Acidity and Oxygen Vacancies

“…Insights from the earlier works point to the combined use of acidic and redox sites on the catalyst to achieve a high selectivity to AA. , In addition to the well-established role of acidic and redox sites in the reaction, the oxidation of an aldehydic group (−CHO) to a carboxylic group (−COOH) that occurs as the last step can be catalyzed by a base. − Our hypothesis as shown in Scheme B is that a combination of acidic, basic, and redox sites on a single catalyst platform in a spatially isolated manner might be a promising candidate as an effective catalyst for the direct oxidation of cyclohexane to AA. To our knowledge, such a trifunctional catalytic approach has not been attempted for the synthesis of AA from cyclohexane.…”