Ultrafast Glycerol Conversion to Lactic Acid over Magnetically Recoverable Ni–NiO_x@C Catalysts

Abstract

Lactic acid (LA), a key platform chemical from biomass, is an ideal feedstock for biodegradable plastic synthesis. The conversion of glycerol to LA was investigated over graphitic-carbon-layer-encapsulated Ni–NiO x core/shell (Ni–NiO x @C) catalysts, which were prepared by controlled oxidation from pristine Ni@C. The oxidation temperature greatly influenced the percentage of NiO x and thus the amount of Lewis acid. In the conversion of glycerol, the catalyst oxidized at 200 °C provided hitherto the highest LA formation rate (5.67 mol/(m3·gcat·s)), which is at least 15 times faster than those obtained over the reported Cu and noble metal catalysts under comparable reaction conditions. The excellent performance of Ni–NiO x @C was attributed to the synergistic effect of the homogenous base, metallic Ni, and acidic NiO x sites, which accelerates the bond cleavage of α-C–H and C–O and promotes ultrafast formation of LA within 30 min.

5-Hydroxymethylfurfural Hydrodeoxygenation Coupled with Water-Gas Shift Reaction for 2,5-Dimethylfuran Production over Au/ZrO2 Catalysts

“…This indicates that the balance of base (acid) and metal played an important role in the WGSR and hydrodeoxygenation of 5-HMF to 2,5-DMF, respectively. In our previous reports, a similar synergistic effect of metal and Lewis sites was also discussed. − In these cases, 5% Au/ZrO 2 had more basic sites as compared to the ZrO 2 support. CO adsorbed on the Au surface with negative charge, and then formed monodentate carbonate with H 2 O at the Au/base interface, the monodentate carbonate formed at the Au/base interface was beneficial for H 2 O dissociation, adsorption, and CO activation and oxidation, and was responsible for releasing CO 2 and hydrogen species at low temperature. , The active hydrogen species generated from WGSR was transferred to the Au/acid interface for 5-HMF hydrogenolysis to 2,5-DMF. , Meanwhile, the neighboring acidic sites generated by the oxygen vacancies could effectively activate the C–OH bond in 5-HMF and finally form 5-MF with the splitting of the C–O bond due to the attacking of H on Au particles. , The Au/acid interface on the catalyst surface could also effectively activate the CO group in 5-MF to form 5-MFA via hydrogenation, followed by forming the target 2,5-DMF by a similar synergistic hydrogenolysis .…”

Combined dehydrogenation of glycerol with catalytic transfer hydrogenation of H2 acceptors to chemicals: Opportunities and challenges

“…Currently, a series of homogeneous or solid metal catalysts, including Ir- ( Sharninghausen et al, 2014 ; Lu et al, 2016 ; Finn et al, 2018 ), Pt- ( Jin et al, 2013 ; Ftouni et al, 2015 ; Oberhauser et al, 2016 ; Tang et al, 2019b ; Zhang et al, 2019 ), Pd- ( Marques et al, 2015 ; Shen et al, 2019 ), Ru ( Deng et al, 2021 ), Au- ( Shen et al, 2017a ; Palacio et al, 2019 ), Cu- ( Roy et al, 2011 ; Moreira et al, 2016 ; Yang et al, 2016 ; Yin et al, 2016 ; Shen et al, 2017b ; Li et al, 2017 ; Yin et al, 2017 ; Palacio et al, 2018a ), Ni- ( Qiu et al, 2018 ; Yin et al, 2018 ; Abdullah et al, 2020 ; Tang et al, 2020 ; Xiu et al, 2020 ), and Co-based ( Palacio et al, 2018b ) systems, have been developed to promote the rate-determining step under relatively mild reaction conditions (lower reaction temperature and alkali concentration). For example, our previous report ( Zhang et al, 2019 ) indicates that Pt–Co bimetallic catalysts significantly enhance the rate of C–H and O–H bond cleavage, showing a good dehydrogenation activation for glycerol transformation at 200°C (glycerol conversion: 85%, LA selectivity: 88%).…”

Highly efficient Ni–NiO/carbon nanotubes catalysts for the selective transfer hydrogenation of 5-hydroxymethylfurfural to 2,5-bis(hydroxymethyl)furan

“…NiO is mainly responsible for the CTH of HMF to prepare BHMF, and the presence of Ni 0 is to assist NiO to further improve selectivity. It is well known that Ni 0 shows excellent performance in activating the C-H bond 29 and the metal site Ni 0 will preferentially adsorb H linked to alcohol hydroxyl αC (αH) rather than αC. 30 First, the strong base center O 2− in NiO adsorbed hydroxyl H and activated it.…”