abstract
The discovery of heterogeneous catalysts synthesized in easy, sustainable ways for the valorization of olefins derived from renewable biomass is attractive from environmental, sustainability, and economic viewpoints. Here, an organic-inorganic hybrid catalyst formulated as [MoO3(Hpto)]center dot H2O (2), where Hpto = 5-(2-pyridyl-1-oxide)tetrazole, was prepared by a hydrolysis-condensation reaction of the complex [MoO2Cl2(Hpto)]center dot THF (1). The characterization of 1 and 2 by FT-IR and Raman spectroscopies, as well as C-13 solid-state NMR, suggests that the bidentate N,O-coordination of Hpto in 1 (forming a six-membered chelate ring, confirmed by X-ray crystallography) is maintained in 2, with the ligand coordinated to a molybdenum oxide substructure. Catalytic studies suggested that 2 is a rare case of a molybdenum oxide/organic hybrid that acts as a stable solid catalyst for olefin epoxidation with tert-butyl hydroperoxide. The catalyst was effective for converting biobased olefins, namely fatty acid methyl esters (methyl oleate, methyl linoleate, methyl linolenate, and methyl ricinoleate) and the terpene limonene, leading predominantly to the corresponding epoxide products with yields in the range of 85-100% after 24 h at 70 degrees C. The versatility of catalyst 2 was shown by its effectiveness for the oxidation of sulfides into sulfoxides and sulfones, at 35 degrees C (quantitative yield of sulfoxide plus sulfone, at 24 h; sulfone yields in the range of 77-86%). To the best of our knowledge, 2 is the first molybdenum catalyst reported for methyl linolenate epoxidation, and the first of the family [MoO3(L)(x)] studied for methyl ricinoleate epoxidation.
keywords
ACID METHYL-ESTERS; TRIAZOLYLMOLYBDENUM(VI) OXIDE HYBRIDS; CRYSTAL-STRUCTURE; OXIDATION; TETRAZOLE; ELUCIDATION; CHEMISTRY; EFFICIENT; BEHAVIOR; EU(III)
subject category
Chemistry
authors
Nunes, MS; Gomes, DM; Gomes, AC; Neves, P; Mendes, RF; Paz, FAA; Lopes, AD; Pillinger, M; Valente, AA; Gonçalves, IS
our authors
Ana Catarina Costa Gomes Alves
Assistant Researcher
Anabela Tavares Aguiar Valente
Principal Researcher
Filipe Alexandre Almeida Paz
Principal Researcher
Isabel Maria de Sousa Gonçalves
Associate Professor
Martyn Pillinger
Principal Researcher
Patrícia dos Santos Neves
Assistant Researcher
Ricardo Faria Mendes
Junior ResearcherProjects
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
CICECO - Aveiro Institute of Materials (UIDP/50011/2020)
Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)
Conversao catalitica de olefinas derivadas da biomassa (BiOle_AcidOxCat)
acknowledgements
This work was carried out with the support of CICECO-Aveiro Institute of Materials (FCT (Fundacao para a Ciencia e a Tecnologia) ref. UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020) and the COMPETE 2020 Operational Thematic Program for Competitiveness and Internationalization (Project POCI-01-0145-FEDER-030075), co-financed by national funds through the FCT/MCTES (PIDDAC) and the European Union through the European Regional Development Fund under the Portugal 2020 Partnership Agreement. This study received Portuguese national funds from the FCT through the operational programs CRESC Algarve 2020 and COMPETE 2020 through project EMBRC.PT ALG-01-0145-FEDER-022121. M.S.N. (grant ref. 2021.06403.BD) and D.M.G. (grant ref. 2021.04756.BD) acknowledge the FCT for Ph.D. grants (State Budget, European Social Fund (ESF) within the framework of PORTUGAL2020, namely through the Centro 2020 Regional Operational Program). A.C.G. (CEECIND/02128/2017) and R.F.M. (CEECIND/00553/2017) thank the FCT/MCTES for funding through the Individual Call to Scientific Employment Stimulus.