Homogeneous catalysts based on heteropoly acids (review)

Kozhevnikov, I. V.; Matveev, K. I.

doi:10.1016/0166-9834(83)80128-6

Cited by 284 publications

(148 citation statements)

References 33 publications

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“…Additionally, the reaction was carried out in the absence of HPA in wet solvent and also afforded 5a. However, the yield of 5a decreased and an inseparable mixture was obtained (entries 10,11). This indicates that the presence of water plays an important role in producing 5a, and the hydration water of HPA, which is present in the vicinity of the electrophilic site, has a stabilizing effect on the cation radical species due to the greater softness of the HPA anion, and may cause a preference for efficiently yielding 5a.…”

Section: Efficient Synthesis Of Morphinandienone Alkaloidmentioning

confidence: 97%

Development and Application of New Oxidation Systems Utilizing Oxometalate Catalysts

Hamamoto

2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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This review describes our recent efforts in the development and application of new oxidation systems utilizing oxometalate catalysts. The novel use of heteropoly acid (HPA), an acidic oxometalate catalyst, in hypervalent iodine-mediated oxidations provided an effective strategy to generate cation radical species that enables a variety of direct C-H functionalizations of aromatic compounds. This strategy brought a facile biaryl synthesis and new spirodienone syntheses in aromatic oxidation chemistry. Moreover, this strategy opens up a facile synthetic route to morphinandienone alkaloids. On the other hand, the use of oxometalate catalyst together with poly(N-isopropylacrylamide) (PNIPAAm)-based polymer in the development of new solid-phase catalyst provided a novel reaction system in water. Due to the characteristic temperature-responsive intelligence of PNIPAAm, this reaction system brought a remarkable acceleration of the reactivity and ease of catalyst recovering in catalytic oxidation that uses hydrogen peroxide or oxygen gas (O 2 ) as primary oxidant. In addition, the recovered solid-phase catalyst could be used for consecutive reactions without any significant loss of its catalytic efficacy.

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Section: Efficient Synthesis Of Morphinandienone Alkaloidmentioning

confidence: 97%

Development and Application of New Oxidation Systems Utilizing Oxometalate Catalysts

Hamamoto

2012

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…51 ) e elevada solubilidade em meio polar, o HPA necessita de suportes que possuem alta estabilidade térmica e alta área superficial que possam torná-lo insolúvel em solventes polares e aumentar ainda mais sua atividade catalítica que é atribuída a forte adsorção dos prótons nos suportes. [73][74][75][76] A escolha do suporte deve ser feita de maneira criteriosa, pois é possível a ocorrência de substituição parcial dos prótons no HPA por diferentes cátions em catalisadores suportados, resultando em seus sais correspondentes os quais tendem a formar suspensões coloidais em meio polar, aumentando ainda mais as dificuldades na separação do catalisador. 53,76 Os catalisadores suportados em metais estão entre os materiais mais importantes na catálise heterogênea.…”

Section: Catalisadores áCidosunclassified

Reutilization of Glycerol Derived from Biodiesel Production Using HPW-Based Catalysts Supported on Niobium for Obtention of Additives

Lacerda¹,

Souza²,

Essayem³

et al. 2014

Revista Virtual De Química

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Abstract:This review proposes the use of residual glycerol, generated in biodiesel production, as raw material for production of oxygenate additive to biofuel. Oxygenated additives, such as glycerol ethers, increase the value of fuel mixture and engine performance. This represents a new methodology in line with the green chemistry principles. The etherification reaction, responsible for the additives production (glycerol ethers), can be effected by the heterogeneous acid catalysts application due to their specificities, like the possibility of reusing, greater strength and higher acidity. It was found that the Keggin heteropolyacids (HPW) supported on niobia have a potential that can be exploited for further industrial application.Keywords: Oxygenate additive; biodiesel; acid catalyst; glycerol. ResumoEsta revisão propõe a utilização do glicerol residual, gerado no processo de produção de biodiesel, como matéria prima para a produção de aditivo oxigenado para o próprio biocombustível, que representa uma metodologia inovadora alinhada com o princípio da química verde. Aditivos oxigenados, como os éteres de glicerol, aumentam o valor agregado de misturas combustíveis e o desempenho de motores. A reação de eterificação, responsável pela produção dos aditivos (éteres de glicerol), pode ser efetivada pela aplicação de catalisadores heterogêneos ácidos devido as suas especificidades com relação à possibilidade de reutilização, maior resistência mecânica e maior acidez relativa. Após este levantamento, verificou-se que os heteropoliácidos do tipo Keggin (HPA), suportados em nióbia, apresentam potencialidades que podem ser exploradas para uma futura aplicação industrial deste catalisador.Palavras-chave: Aditivo oxigenado; biodiesel; catalisador ácido; glicerol.

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“…For heterogeneous systems, it is possible to control solid strength by supporting HPAs on different carriers [17]. An immobilization of HPAs on a number of porous supports such as silica, active carbon, montmorillonite K-10, zeolite, zirconium phosphate and so on [17][18][19][20][21][22] was, therefore, extensively studied.…”

Section: Introductionmentioning

confidence: 99%

Facile route for the synthesis of benzothiazoles and benzimidazoles in the presence of tungstophosphoric acid impregnated zirconium phosphate under solvent‐free conditions

Aliyan

Fazaeli

et al. 2009

Heteroatom Chemistry

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Homogeneous catalysts based on heteropoly acids (review)

Cited by 284 publications

References 33 publications

Development and Application of New Oxidation Systems Utilizing Oxometalate Catalysts

Development and Application of New Oxidation Systems Utilizing Oxometalate Catalysts

Reutilization of Glycerol Derived from Biodiesel Production Using HPW-Based Catalysts Supported on Niobium for Obtention of Additives

Facile route for the synthesis of benzothiazoles and benzimidazoles in the presence of tungstophosphoric acid impregnated zirconium phosphate under solvent‐free conditions

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