Influence of surface acid and base sites on the Guerbet coupling of ethanol to butanol over metal phosphate catalysts

Hanspal, Sabra; Young, Zachary D.; Prillaman, J. Tyler; Davis, Robert J.

doi:10.1016/j.jcat.2017.04.036

Cited by 88 publications

(71 citation statements)

References 38 publications

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“…A deeper insight into the role of hydrogen atoms produced from alcohol dehydrogenation, one aspect still unclear, was obtained by Hanspal et al . They showed by dihydrogen co‐feeding experiments that H 2 formed in the first step is not responsible for the final hydrogenation step.…”

Section: Guerbet Condensation Reactionssupporting

confidence: 79%

“…Ad eeper insight into the role of hydrogen atoms produced from alcohold ehydrogenation, one aspect still unclear, was obtained by Hanspale tal. [26] They showedb yd ihydrogen cofeedinge xperimentst hat H 2 formed in the first step is not responsible for the final hydrogenation step. Thus, increasing the concentrationo fH 2 even to > 90 %o ft he feed in the reaction www.chemcatchem.org of ethanolo ver HAP at 340 8Ch ad no effect either on ethanol conversion rate or on butanol selectivity,s trongly suggesting a Meerwein-Ponndorff-Verley-type hydrogen transfer from ethanol.…”

Section: Guerbet Condensation Reactionsmentioning

confidence: 99%

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The Role of Copper in the Upgrading of Bioalcohols

2018

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Some recent results on Guerbet reactions are reported and a short review on dehydrogenative coupling of alcohols (DHC) is presented. The focus of this Minireview is on the role of acidic and basic sites and, in particular, on the role of Cu if it is present in the catalyst, taking into account that the two processes share the first step, namely alcohol dehydrogenation, whereas the second one is determining in driving selectivity towards self‐coupling or symmetrical ester formation. The main type of catalysts for the Guerbet reaction are based on hydrotalcites, hydroxyapatite and supported metal systems, whereas the catalysts for DHC are copper catalysts on different supports. The role of acidic and basic sites in determining activity and selectivity to Guerbet alcohols has been investigated and quite stringent requirements for the selectivity of the reaction have been highlighted. For DHC, we have focused on the role of the interaction of copper with the support, which in turn influences the distribution of acidic and basic sites. The morphology of the metallic phase has been suggested as a distinctive factor in promoting C−C coupling or C−O coupling in the second step for Cu‐containing catalysts.

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Section: Guerbet Condensation Reactionssupporting

confidence: 79%

Section: Guerbet Condensation Reactionsmentioning

confidence: 99%

The Role of Copper in the Upgrading of Bioalcohols

2018

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“…Finally,m ost of the hetero-or homogeneous reactions are carriedo ut in organic solvent, pure reactant, or diluted gas phase, rather than the aqueous phase, because the presence of water in the initial reactant mixture or resulting from the dehydration process is usually detrimental to catalysts. [67] On the other hand, the use of water as ar eaction mediumh as many advantages from economic, environmental, and safetys tandpoints, and thus, is greatly anticipated in the future. Moreover, bioethanol derived from am ature fermentation process in water is preferable for use directly as ar eactantf or the upgradingo fe thanol to n-butanol.…”

Section: Research Prospectsmentioning

confidence: 99%

Catalytic Upgrading of Ethanol to n‐Butanol: Progress in Catalyst Development

et al. 2017

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Because n‐butanol as a fuel additive has more advantageous physicochemical properties than those of ethanol, ethanol valorization to n‐butanol through homo‐ or heterogeneous catalysis has received much attention in recent decades in both scientific and industrial fields. Recent progress in catalyst development for upgrading ethanol to n‐butanol, which involves homogeneous catalysts, such as iridium and ruthenium complexes, and heterogeneous catalysts, including metal oxides, hydroxyapatite (HAP), and, in particular, supported metal catalysts, is reviewed herein. The structure–activity relationships of catalysts and underlying reaction mechanisms are critically examined, and future research directions on the design and improvement of catalysts are also proposed.

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“…Such a proposal remains uncertain when considering the structural properties of HAps, for which no evident Ca−O‐like species are present due to the facts that oxygen atoms in these materials belong to phosphate and hydroxyl groups, and the surface concentration in Ca 2+ is limited . In contrast, the potential involvement of surface terminated acidic POH and basic OH groups has not been considered yet to our knowledge, even if it was recently reported that HAps are much more active and selective in n‐ butanol compared to other calcium phosphates …”

Section: Introductionmentioning

confidence: 99%

Importance of the Nature of the Active Acid/Base Pairs of Hydroxyapatite Involved in the Catalytic Transformation of Ethanol to n‐Butanol Revealed by Operando DRIFTS

et al. 2019

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Operando DRIFTS is used to identify the nature and the role of the surface sites of hydroxyapatites (HAps) involved in the catalytic transformation of ethanol to n-butanol. The surface processes occurring upon a first reaction step followed by a step under He flow greatly influence the reactivity of HAps in a subsequent second reaction step. Ethanol is found to be mostly activated by the basic OH À groups of HAps, as indicated by the concomitant recovery of ethanol conversion and OH À groups under He flow. The drastic changes in selectivity observed during the second reaction step reveal the key role of acidic sites cooperatively acting with basic sites for basic reaction steps. Once the POH groups are poisoned by extensive formation of polymeric carbon species and the Ca 2 + sites are available, the production of acetaldehyde is drastically promoted at the expense of that of n-butanol. It is concluded that i) acetaldehyde acts as an intermediate in the formation of nbutanol, and ii) various active sites are involved in the key basic reaction steps such as Ca 2 + À OH À and POHÀ OH À acid-base pairs in the dehydrogenation of ethanol to acetaldehyde and the aldol condensation for n-butanol formation, respectively.

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Influence of surface acid and base sites on the Guerbet coupling of ethanol to butanol over metal phosphate catalysts

Cited by 88 publications

References 38 publications

The Role of Copper in the Upgrading of Bioalcohols

The Role of Copper in the Upgrading of Bioalcohols

Catalytic Upgrading of Ethanol to n‐Butanol: Progress in Catalyst Development

Importance of the Nature of the Active Acid/Base Pairs of Hydroxyapatite Involved in the Catalytic Transformation of Ethanol to n‐Butanol Revealed by Operando DRIFTS

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