It is imperative to develop more efficient processes for conversion of biomass to liquid fuels, such that the cost of these fuels would be competitive with the cost of fuels derived from petroleum. We report a catalytic approach for the conversion of carbohydrates to specific classes of hydrocarbons for use as liquid transportation fuels, based on the integration of several flow reactors operated in a cascade mode, where the effluent from the one reactor is simply fed to the next reactor. This approach can be tuned for production of branched hydrocarbons and aromatic compounds in gasoline, or longer-chain, less highly branched hydrocarbons in diesel and jet fuels. The liquid organic effluent from the first flow reactor contains monofunctional compounds, such as alcohols, ketones, carboxylic acids, and heterocycles, that can also be used to provide reactive intermediates for fine chemicals and polymers markets.

http://science.sciencemag.org/content/sci/322/5900/417.full.pdf

Catalytic conversion of biomass to monofunctional hydrocarbons and targeted liquid-fuel classes.

Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid-base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/cssc.201000054

Ceria‐Based Solid Catalysts for Organic Chemistry

Ketonization is a reaction in which two carboxylic acids convert into a ketone, carbon dioxide, and water. While this reaction once found its industrial application for acetone production, it is regaining interest for its value in the upgrading of biomass-derived oxygenates, for example, bio-oils obtained from the fast pyrolysis of biomass. Namely, ketonization is crucial to reduce the detrimental effects of carboxylic acids in bio-oil. This review addresses reaction mechanisms, families of materials that catalyze the reaction (metal oxides and zeolites), and current applications of ketonization in the upgrading of biomass-derived oxygenates. A variety of mechanisms have been proposed to explain the ketonization reaction, and these proposals are critically discussed. The role of the α-hydrogen has been proven as a critical requirement for ketonization over catalysts that are active for surface ketonization and serves as the initial basis for the discussion. The role of crucial reaction intermediates such ...

Ketonization of Carboxylic Acids: Mechanisms, Catalysts, and Implications for Biomass Conversion

Catalytic coupling of carboxylic acids by ketonization as a processing step in biomass conversion

Upgrading of pyrolysis oil from biomass offers great potential economic and environmental benefits for the production of sustainable and renewable energy sources. Meanwhile, challenges remain in the development of technical- and cost-effective catalysts and operating processes. One promising approach is liquid phase upgrading, which exhibits numerous benefits. This paper reviews recent progress and future possibilities for obtaining fuels from biomass using this approach. Key upgrading reactions for different oxygenated compounds in pyrolysis oil, including ketonization, aldol condensation, alkylation, hydrodeoxygenation, and oxygenation are discussed. Development of effective catalysts and efficient integration of multiple consecutive reaction steps in one single reactor make liquid phase upgrading competitively advantageous.

Evaluating strategies for catalytic upgrading of pyrolysis oil in liquid phase

The ketonization of propanoic acid to form 3-pentanone over CeO 2 -based composite oxides at temperatures of 300–425 °C was investigated. A CeO 2 -based solid solution, CeO 2 –Mn 2 O 3 , was effective for the ketonization. The citrate process was the most appropriate method for preparing a well-dispersed solid solution. In the ketonization of propanoic acid with another linear carboxylic acid, an asymmetric ketone together with two symmetric ketones was formed, and the ketone composition was approximated by a binomial distribution. The reactivity of the carboxylic acid was slightly decreased as its chain length was increased. In contrast to linear aliphatic acids, branched acids were less reactive. Methyl group substituents at the α- and β-positions of carboxylic acids decreased their reactivities in both homo- and cross-ketonization. The lack of an α-hydrogen or the increase in steric hindrance was surmised to be the cause of the decrease in reactivity.

Ketonization of carboxylic acids over CeO2-based composite oxides

Cycloketonization of dimethyl hexanedioate into cyclopentanone was investigated over pure CeO2 at a temperature between 350 and 475 °C The conversion of the diester increased with raising the reaction temperature The selectivity to cyclopentanone, however, decreased whenever the conversion increased The major by-product other than methanol was 2-methylcyclopentanone It was found that methylation of cyclopentanone with methanol into 2-methylcyclopentanone proceeded over CeO2 The decrease in the selectivity to cyclopentanone at high conversion was mainly caused by a consecutive reaction of cyclopentanone into 2-methylcyclopentanone due to alkylation with methanol

Osamu Nagashima

Papers

Ketonization of carboxylic acids over CeO2-based composite oxides

Formation of cyclopentanone from dimethyl hexanedioate over CeO2