Selective oxidation of glycerol in a base-free aqueous solution: A short review

Catalytic transformation of glycerol to value-added products has attracted the attention of scientists all over the world. Among various transformations, selective oxidation of glycerol with molecular oxygen to dihydroxyacetone, glyceric acid, glyceraldehydes, and tartronic acid is challenging both from the viewpoint of academic research and industrial application. Herein, we review the recent progresses in the selective oxidation of glycerol under base-free conditions. Those catalysts widely reported for the selective oxidation of the terminal hydroxyl and secondary hydroxyl groups in glycerol, such as monometallic Au, Pt, and Pd NPs, and bimetallic Au-Pt, Au-Pd, Pt-Bi, Pt-Sb, and Pt-Cu, were compared and discussed in detail. The reaction mechanism over Pt-based catalysts, possible catalyst deactivation, and the corresponding improvements are presented. Further, the recent progresses in the continuous oxidation of glycerol in fixed bed reactors and its excellent selectivity in the formation of dihydroxyacetone are highlighted.

Selective oxidation of glycerol with oxygen in base-free solution over N-doped-carbon-supported Sb@PtSb2 hybrid

Selective oxidation of glycerol with molecular oxygen in base-free aqueous solutions has become a hot topic,as the rapidly increasing production of biodiesel is creating a surplus of glycerol.In this work,an N-doped-carbon-supported core-shell structured Sb@PtSb2 hybrid catalyst was prepared via a facile synthesis route,in which a mixture of glucose,melamine,and SbCl3(Sb-NC)was pyrolyzed,then impregnated with Pt by immersion in an aqueous solution of H2PtCl6,and further treated in hydrogen flow.Characterization of the catalyst products indicated that introducing SbCl3 can increase the surface area of the binary glucose+melamine pyrolyzed support(NC),and Sb@PtSb2 hybrids could be formed on the surface of an Sb-NC support during hydrogen treatment at 700℃.It was found that the Sb@PtSb2/NC catalyst was more active for the selective oxidation of glycerol in a base-free aqueous solution than Sb-free NC-supported Pt(Pt/NC).Further characterization also indicated that the promising performance of Sb@PtSb2/NC might be attributed to its enhanced oxygen activation.

Carbon film encapsulated Fe_2O_3: An efficient catalyst for hydrogenation of nitroarenes

Iron catalysis has attracted a wealth of interdependent research for its abundance,low price,and nontoxicity.Herein,a convenient and stable iron oxide(Fe2O3)‐based catalyst,in which active Fe2O3nanoparticles(NPs)were embedded into carbon films,was prepared via the pyrolysis of iron‐polyaniline complexes on carbon particles.The obtained catalyst shows a large surface area,uniform pore channel distribution,with the Fe2O3NPs homogeneously dispersed across the hybrid material.Scanning electron microscopy,Raman spectroscopy and X‐ray diffraction analyses of the catalyst prepared at900°C(Fe2O3@G‐C‐900)and an acid‐pretreated commercial activated carbon confirmed that additional carbon materials formed on the pristine carbon particles.Observation of high‐resolution transmission electron microscopy images also revealed that the Fe2O3NPs in the hybrid were encapsulated by a thin carbon film.The Fe2O3@G‐C‐900composite was highly active and stable for the direct selective hydrogenation of nitroarenes to anilines under mild conditions,where previously noble metals were required.The synthetic strategy and the structure of the iron oxide‐based composite may lead to the advancement of cost‐effective and sustainable industrial processes.

A highly active and stable organic-inorganic combined solid acid for the transesterification of glycerol under mild conditions

Solid acid catalyst plays a crucial role in the petroleum refinery industry and bio-refinery technology.In this work,p-phenolsulfonic acid(PSA)was successfully grafted onto the surface of KH560-modified zirconium phosphate(K-ZrP)in a facile routine.The structure and property of this organic-inorganic combined solid acid PSA/K-ZrP-x were characterized via XRD,FTIR,^(13)C solid-state NMR,TG,N_(2) adsorption-desorption,SEM,pyridine-adsorption FTIR and XPS technologies.The characterization results showed that KH560 can bond with ZrP and promote the grafting of PSA on the surface of K-ZrP via the condensation reaction between its epoxy ring and the phenolic hydroxyl group in PSA.Consequently,PSA/K-ZrP-2 exhibited excellent performance and stability in the transesterification between glycerol and methyl acetate among the tested H_(3)PW_(12)O_(40),Amber-lyst-45,HBEA,HZSM-5,ZrP,AlCl_(3) and FeCl_(3) catalysts.The calculated conversion of glycerol reached 81.3%with a 97.9%selectivity for monoacetin(MAG)and diacetin(DAG)with a 2.2%dosage of[H^(+)]at 100℃ for 4 h.The highest specific activity of PSA/K-ZrP-2 reached 24028.2 mg-glycerol/g-cat/h in a short reaction time(at 0.17 h),and it could be recycled five times without obvious deactivation.