Metal-free bifunctional silica for conversion of waste glycerol from biodiesel: Sustainable production of formic acid

Chagas, Poliane; Thibau, Mariana A.; Breder, Samuel Moura; Souza, Patterson P. de; Caldeira, Gabriela Santos; Portilho, Márcio F.; Castro, Cínthia S.; Oliveira, Luiz C.A.

doi:10.1016/j.cej.2019.03.068

Cited by 20 publications

(5 citation statements)

References 38 publications

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“…In this context, catalytic oxidation of polyol/sugar emerges as a promising alternative for FA production 6 – 16 . However, the mainstream homogeneous catalysts including heteropoly acids, NaVO 3 , VOSO 4 , and others suffer from poor catalyst recycling, metal contamination, and/or the employment of non-benign oxidants 8 , 17 – 23 . Recently, several heterogeneous catalysts based on CuO x or VO x have been excavated using O 2 as oxidant 20 , 24 , but the attainment of a high FA yield with sufficient reaction rate using non-precious metal oxide catalyst remains a challenge 1 .…”

Section: Introductionmentioning

confidence: 99%

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

et al. 2023

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Oxidation of renewable polyol/sugar into formic acid using molecular O2 over heterogeneous catalysts is still challenging due to the insufficient activation of both O2 and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO2 catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO2, the tri-coordinated Mn in the defective MnO2 catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mnδ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O2, as well as C–C and C–H bonds. As a result, the defective MnO2 catalyst shows high catalytic activity (turnover frequency: 113.5 h−1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance.

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Section: Introductionmentioning

confidence: 99%

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

et al. 2023

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“…Chagas et al used mesoporous silica as the metal free catalyst to oxidize GLY to FA with high catalytic activity and selectivity in continuous flow, and it was found that the vacant oxygen sites on the silica surface can react with H 2 O 2 to generate highly active oxygen species, giving mesoporous silica an oxidizing character. 17 Another alternative to noble metals is copper, which was demonstrated to be active for GLY oxidation and cleavage of the C−C bonds. For example, Schunemann et al found that the ordered mesoporous Cu-Al 2 O 3 catalysts were active for GLY oxidation under basic conditions, yielding C3 products, such as GLA and TA, and also C2 and C1 products, such as glycolic acid (GA), OA, and FA.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Nevertheless, more abundant and cost-efficient catalysts are highly desirable. Chagas et al used mesoporous silica as the metal free catalyst to oxidize GLY to FA with high catalytic activity and selectivity in continuous flow, and it was found that the vacant oxygen sites on the silica surface can react with H 2 O 2 to generate highly active oxygen species, giving mesoporous silica an oxidizing character . Another alternative to noble metals is copper, which was demonstrated to be active for GLY oxidation and cleavage of the C–C bonds.…”

Section: Introductionmentioning

confidence: 99%

Facile Preparation of Nitrogen-Doped Carbon Spheres with Wrinkled Cage-Supported Single-Atom Copper Catalysts for Selective Oxidation of Glycerol to Formic Acid

Zhu

Yang

et al. 2022

ACS Sustainable Chem. Eng.

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Selective conversion of the surplus glycerol (GLY) to a hydrogen storage material, formic acid (FA), in heterogeneous catalytic systems is still challenging in the catalysis community. Herein, nitrogen-doped carbon spheres with wrinkled cagesupported single-atom Cu catalysts (Cu/NCSWCs) were prepared by wet ball milling of 5,5′-diamino-3,3′-bis(1H-1,2,4-triazole) (DABT) and copper nitrate with hydrothermal carbon-encapsulated dendritic fibrous nanosilica (DFNS) as the hard template in methanol. After the removal of DFNS, structural characterization revealed that single copper atoms with four nitrogen coordination were successfully immobilized on NCSWCs (CuN 4 /NCSWCs), which is attributed to the fact that DABT could act as the chelating agent and nitrogen source. Furthermore, due to their unique CuN 4 structures and large meso/macropore volumes derived from their wrinkled cages, CuN 4 /NCSWCs exhibited the highest catalytic activity and selectivity in oxidation of GLY to FA using H 2 O 2 as the oxidant. In contrast, only C3 and C2 products were produced when O 2 was used as the oxidant. Electron paramagnetic resonance measurements indicated that H 2 O 2 and O 2 can be activated to generate • OH and • O 2 − over CuN 4 /NCSWCs, respectively. Experimental studies and density functional theory calculations revealed that • OH adsorbed on CuN 4 structures reacted with GLY to produce FA through consecutive steps involving dehydrogenation, oxidation, and oxidative cleavage. Moreover, CuN 4 /NCSWCs also exhibited high catalytic stability during eight consecutive catalytic runs.

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“…Many studies have reported utilisation of preformed H 2 O 2 as oxidant for glycerol oxidation. These studies have focussed on a range of different catalysts, including various supported metal catalysts [19][20][21][22][23][24][25] and metal oxides [26][27][28][29][30][31][32][33][34]. McMorn et al [35] assessed metal-doped silicate (containing Ti, V or Fe) and aluminophosphate catalysts (containing Cr, V, Mn or Co) for oxidation of glycerol with H 2 O 2 , reporting low yields of the desired partial oxidation products.…”

Section: Introductionmentioning

confidence: 99%

Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

et al. 2021

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Low temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.

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Metal-free bifunctional silica for conversion of waste glycerol from biodiesel: Sustainable production of formic acid

Cited by 20 publications

References 38 publications

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Facile Preparation of Nitrogen-Doped Carbon Spheres with Wrinkled Cage-Supported Single-Atom Copper Catalysts for Selective Oxidation of Glycerol to Formic Acid

Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species

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