Ayyagari V. Subrahmanyam

Bio: Ayyagari V. Subrahmanyam is an academic researcher from University of Massachusetts Amherst. The author has contributed to research in topics: Enyne metathesis & Carbon nanotube. The author has an hindex of 14, co-authored 18 publications receiving 1190 citations. Previous affiliations of Ayyagari V. Subrahmanyam include Indian Institute of Technology Bombay & McMaster University.

Production of renewable petroleum refinery diesel and jet fuel feedstocks from hemicellulose sugar streams

Abstract: We demonstrate how hemicellulose-derived C5 sugars can be converted into a high-quality petroleum refinery feedstock by a four-step catalytic process. The substitute petroleum consists of normal, branched and cyclic alkanes up to 31 carbons in length and is similar in composition to feedstocks produced in a petroleum refinery today from crude oil. This process can be tuned to adjust the size of the liquid alkanes. In the first step furfural is produced from the acid-catalyzed dehydration of hemicellulose-derived sugar streams in a biphasic reactor. The second step is the aldol condensation of furfural with acetone in a THF solvent and using a NaOH catalyst to produce highly conjugated C13 compounds along with some oligomeric adducts formed through Michael addition reactions. These compounds are then hydrogenated with a Ru/Al2O3 catalyst forming both the fully hydrogenated form of the C13 oligomers and also forming larger oligomers by Diels–Alder reactions. The extent of Diels–Alder reactions can be tuned by changing the temperature and feed concentration, thereby adjusting the distribution of liquid alkanes that can be produced. The final step in this process is hydrodeoxygenation using a Pt/SiO2–Al2O3 bifunctional catalyst to produce the liquid alkanes. A simple biorefinery model has shown that about 55% of a furfural–acetone mixture (10 : 3 wt ratio) can be converted into cycle oils while also producing other refinery products such as gasoline and natural gas.

C! C Bond Formation Reactions for Biomass-Derived Molecules

Abstract: There has been a tremendous interest in the utilization of biomass as feedstock to produce renewable fuels and chemicals. The major monomer building blocks of biomass are carbohydrates which are typically 5 or 6 carbons in length. Petroleumderived jet and diesel fuels are between 8 to 15 carbons in length. Therefore, to produce jet and diesel fuel from biomass, there must be a C!C bond formation from the biomass-derived molecules. However, direct C!C bond formation from carbohydrates (C5 and C6) is difficult due to the polyhydroxy functionalities on the carbohydrates. These polyhydroxy functionalities make the carbonyl group of the carbohydrates less reactive toward C!C bond formation because of its hemiacetal form. To overcome this problem, several research groups have converted C5 and C6 carbohydrates to aromatic aldehydes (Figure 1) such as furfural 1 and hydroxymethylfurfural (HMF) 2

Catalytic Transformation of Lignin for the Production of Chemicals and Fuels

Abstract: and Fuels Changzhi Li,† Xiaochen Zhao,† Aiqin Wang,† George W. Huber,†,‡ and Tao Zhang*,† †State Key Laborotary of Catalysis, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China ‡Department of Chemical and Biological Engineering, University of WisconsinMadison, Madison, Wisconsin 53706, United States

Chemicals from lignin: an interplay of lignocellulose fractionation, depolymerisation, and upgrading

Abstract: In pursuit of more sustainable and competitive biorefineries, the effective valorisation of lignin is key. An alluring opportunity is the exploitation of lignin as a resource for chemicals. Three technological biorefinery aspects will determine the realisation of a successful lignin-to-chemicals valorisation chain, namely (i) lignocellulose fractionation, (ii) lignin depolymerisation, and (iii) upgrading towards targeted chemicals. This review provides a summary and perspective of the extensive research that has been devoted to each of these three interconnected biorefinery aspects, ranging from industrially well-established techniques to the latest cutting edge innovations. To navigate the reader through the overwhelming collection of literature on each topic, distinct strategies/topics were delineated and summarised in comprehensive overview figures. Upon closer inspection, conceptual principles arise that rationalise the success of certain methodologies, and more importantly, can guide future research to further expand the portfolio of promising technologies. When targeting chemicals, a key objective during the fractionation and depolymerisation stage is to minimise lignin condensation (i.e. formation of resistive carbon–carbon linkages). During fractionation, this can be achieved by either (i) preserving the (native) lignin structure or (ii) by tolerating depolymerisation of the lignin polymer but preventing condensation through chemical quenching or physical removal of reactive intermediates. The latter strategy is also commonly applied in the lignin depolymerisation stage, while an alternative approach is to augment the relative rate of depolymerisation vs. condensation by enhancing the reactivity of the lignin structure towards depolymerisation. Finally, because depolymerised lignins often consist of a complex mixture of various compounds, upgrading of the raw product mixture through convergent transformations embodies a promising approach to decrease the complexity. This particular upgrading approach is termed funneling, and includes both chemocatalytic and biological strategies.

Furfural: a renewable and versatile platform molecule for the synthesis of chemicals and fuels

Abstract: The production of future transportation fuels and chemicals requires the deployment of new catalytic processes that transform biomass into valuable products under competitive conditions. Furfural has been identified as one of the most promising chemical platforms directly derived from biomass. With an annual production close to 300 kTon, furfural is currently a commodity chemical, and the technology for its production is largely established. The aim of this review is to discuss the most relevant chemical routes for converting furfural to chemicals, biofuels, and additives. This review focuses not only on industrially produced chemicals derived from furfural, but also on other not yet commercialised products that have a high potential for commercialisation as commodities. Other chemicals that are currently produced from oil but can also be derived from furfural are also reviewed. The chemical and engineering aspects such as the reaction conditions and mechanisms, as well as the main achievements and the challenges still to come in the pursuit of advancing the furfural-based industry, are highlighted.