scholarly journals Selective production of mono-aromatics from lignocellulose over Pd/C catalyst: the influence of acid co-catalysts

2017 ◽  
Vol 202 ◽  
pp. 141-156 ◽  
Author(s):  
Xiaoming Huang ◽  
Xianhong Ouyang ◽  
Bart M. S. Hendriks ◽  
O. M. Morales Gonzalez ◽  
Jiadong Zhu ◽  
...  
Keyword(s):  
Catalytic Performance ◽  
Fractionation Process ◽  
Catalytic Systems ◽  
Promising Alternative ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Speed Up ◽  
Metal Triflates ◽  
Pretreatment Technology ◽  
Glyceryl Trioleate

The ‘lignin-first’ approach has recently gained attention as an alternative whole biomass pretreatment technology with improved yield and selectivity of aromatics compared with traditional upgrading processes using technical lignins. Metal triflates are effective co-catalysts that considerably speed up the removal of lignin fragments from the whole biomass. As their cost is too high in a scaled-up process, we explored here the use of HCl, H2SO4, H3PO4 and CH3COOH as alternative acid co-catalysts for the tandem reductive fractionation process. HCl and H2SO4 were found to show superior catalytic performance over H3PO4 and CH3COOH in model compound studies that simulate lignin–carbohydrate linkages (phenyl glycoside, glyceryl trioleate) and lignin intralinkages (guaiacylglycerol-β-guaiacyl ether). HCl is a promising alternative to the metal triflates as a co-catalyst in the reductive fraction of woody biomass. Al(OTf)3 and HCl, respectively, afforded 46 wt% and 44 wt% lignin monomers from oak wood sawdust in tandem catalytic systems with Pd/C at 180 °C in 2 h. The retention of cellulose in the solid residue was similar.

scholarly journals Copolymerization of Phthalic Anhydride with Epoxides Catalyzed by Amine-bis(phenolate) Chromium(III) Complexes

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1785
Author(s):  
Wiktor Bukowski ◽  
Agnieszka Bukowska ◽  
Aleksandra Sobota ◽  
Maciej Pytel ◽  
Karol Bester
Keyword(s):  
Phthalic Anhydride ◽  
Styrene Oxide ◽  
Glycidyl Ether ◽  
Molar Ratio ◽  
Phenyl Glycidyl Ether ◽  
Cyclohexene Oxide ◽  
Catalytic Systems ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Organic Bases

The effect of ligand structure on the catalytic activity of amine-bis(phenolate) chromium(III) complexes in the ring-opening copolymerization of phthalic anhydride and a series epoxides was studied. Eight complexes differing in the donor-pendant group (R1) and substituents (R2) in phenolate units were examined as catalysts of the model reaction between phthalic anhydride and cyclohexane oxide in toluene. They were used individually or as a part of the binary catalytic systems with nucleophilic co-catalysts. The co-catalyst was selected from the following organic bases: PPh3, DMAP, 1-butylimidazole, or DBU. The binary catalytic systems turned out to be more active than the complexes used individually, and DMAP proved to be the best choice as a co-catalyst. When the molar ratio of [PA]:[epoxide]:[Cr]:[DMAP] = 250:250:1:1 was applied, the most active complex (R1-X = CH2NMe2, R2 = F) allowed to copolymerize phthalic anhydride with differently substituted epoxides (cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, phenyl glycidyl ether, propylene oxide, butylene oxide, and epichlorohydrin) within 240 min at 110 °C. The resulting polyesters were characterized by Mn up to 20.6 kg mol−1 and narrow dispersity, and they did not contain polyether units.

Alternating Ring-Opening Copolymerization of Cyclohexene Oxide and Maleic Anhydride with Diallyl-Modified Manganese(III)–Salen Catalysts

2016 ◽  
Vol 69 (1) ◽  
pp. 47 ◽  
Author(s):  
Dengfeng Liu ◽  
Zhao Zhang ◽  
Xingmei Zhang ◽  
Xingqiang Lü
Keyword(s):  
Maleic Anhydride ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Catalytic Performance ◽  
Chain Growth ◽  
Cyclohexene Oxide ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Polymer Chain Growth ◽  
Catalytic Performances

A series of diallyl-modified (salen)MnIII complexes have been designed, synthesized, and applied in the cyclohexene oxide and maleic anhydride ring-opening copolymerization. The experimental results show that these complexes are effective in the presence of co-catalyst 4-(dimethylamino)pyridine (DMAP). Of all the five catalysts, the catalyst (salcyen)MnCl (salcyen = 2-((E)-(2-((E)-5-allyl-2-hydroxy-3-methoxybenzylideneamino)cyclohexylimino)methyl)-4-allyl-6-methoxyphenol) exhibited the best catalytic performance under the conditions applied, and the cyclohexane of diimine bridge is conjugated with the two diallyl-salen-type moieties. This conjugation can increase the electron density of the centre MnIII cation so that catalyst (salcyen)MnCl favours the formation of reaction intermediates. Moreover, the anion effect of Cl– is proved to be the best in the catalytic performances. Among the three co-catalysts (DMAP, triphenylphosphine (Ph3P), and tetra-n-butylammonium bromide (n-Bu4NBr)) tested, DMAP is the most efficient towards monomer conversion and polymer chain growth.

Superior co-catalysis by bimetallic nanostructure for TiO2 photocatalysis

2020 ◽  
Vol 01 ◽  
Author(s):  
Bonamali Pal ◽  
Anila Monga ◽  
Aadil Bathla
Keyword(s):  
Visible Light ◽  
Catalytic Performance ◽  
Transition Metal Catalysts ◽  
Core Shell ◽  
Structural Morphology ◽  
Tio2 Photocatalysis ◽  
Co Catalysts ◽  
Bimetallic Nanocomposites ◽  
Bimetallic Nanostructure ◽  
Bimetallic Nanostructures

Background:: Bimetallic nanocomposites have currently gained significant importance for enhanced catalytic applications relative to monometallic analogues. The synergistic interactions modified electronic and optical properties in the bimetallic (M1@M2) structural morphology e.g., core-shell /alloy nanostructures resulted in a better co-catalytic performance for TiO2 photocatalysis. Objective:: Hence, this article discusses the preparation, characterization, and co-catalytic activity of different bimetallic nanostructures namely, Cu@Zn, Pd@Au, Au@Ag, and Ag@Cu, etc. Method:: These bimetallic co-catalysts deposited on TiO2 possess the ability to absorb visible light due to surface plasmonic absorption and are also expected to display the new properties due to synergy between two distinct metals. As a result, they reveal the highest level of activity than the monometal deposited TiO2. Result:: Their optical absorption, emission, charge carrier dynamics, and surface structural morphology are explained for the improved photocatalytic activity of M1@M2 loaded TiO2 for the hydrogenation of certain organic compounds e.g., quinoline, crotonaldehyde, and 1,3-dinitrobenzene, etc. under UV/ visible light irradiation. Conclusion:: It revealed that the use of bimetallic core@shell co-catalyst for hydrogenation of important industrial organics by M1@M2-TiO2 nanocomposite demonstrates beneficial reactivity in many instances relative to conventional transition metal catalysts.

Positive effects of a halloysite-supported Cu/Co catalyst fabricated by a urea-driven deposition precipitation method on the CO-SCR reaction and SO2 poisoning

2021 ◽  
Author(s):  
Wei-Jing Li ◽  
Shu Tsai ◽  
Ming-Yen Wey
Keyword(s):  
Co Oxidation ◽  
Catalytic Reduction ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Halloysite Nanotube ◽  
Co Catalyst ◽  
Reduction Of No ◽  
Co Catalysts ◽  
Positive Effects ◽  
So2 Poisoning

Cu/Co catalysts were prepared on halloysite nanotube supports by a urea-driven deposition-precipitation method for CO oxidation and the selective catalytic reduction of NO (CO-SCR). First, the Cu/NH3 molar ratio was...

Erratum to “Metal triflates–methanesulfonic acid as new catalytic systems: application to the Fries rearrangement”

2003 ◽  
Vol 44 (43) ◽  
pp. 8037 ◽  
Author(s):  
Omar Mouhtady ◽  
Hafida Gaspard-Iloughmane ◽  
Nicolas Roques ◽  
Christophe Le Roux
Keyword(s):  
Methanesulfonic Acid ◽  
Fries Rearrangement ◽  
Catalytic Systems ◽  
Metal Triflates

scholarly journals Carbon-Involved Near-Surface Evolution of Cobalt Catalyst during Reaction: An in-situ Study

2020 ◽  
Author(s):  
Feng Yang ◽  
Haofei Zhao ◽  
Wu Wang ◽  
Qidong Liu ◽  
Xu Liu ◽  
...  
Keyword(s):  
Chemical Vapor ◽  
Carbon Diffusion ◽  
Deposition Process ◽  
Catalytic Performance ◽  
Surface Evolution ◽  
Near Surface ◽  
Co Catalysts ◽  
Transmission Electron ◽  
Walled Carbon Nanotubes

Abstract When carbon-containing species are involved in reactions catalyzed by transition metals at high temperature, the diffusion of carbon on/in catalysts dramatically influence the catalytic performance. Acquiring information on the carbon-diffusion-involved evolution of catalysts at atomic level is crucial for understanding the reaction mechanism yet also challenging. For the chemical vapor deposition process of single-walled carbon nanotubes (SWCNTs), we developed methodologies to record in-situ the near-surface structural and chemical evolution of Co catalysts with carbon permeation using an aberration-corrected environmental transmission electron microscope and the synchrotron X-ray absorption spectroscopy. The nucleation and growth of SWCNTs were linked with the partial carbonization of catalysts and the alternating dissolvement-precipitation of carbon in catalysts. The dynamics of carbon atoms in catalysts brings deeper insight into the growth mechanism of SWCNTs and also sheds light on inferring mechanisms of more reactions. The methodologies developed here will find broad applications in studying catalytic and other processes.

Use of (R)-Mandelic Acid as Chiral Co-Catalyst in the Michael Addition Reaction Organocatalyzed by (1S,4S)-2-Tosyl-2,5-diazabicyclo[2.2.1]heptane under Solvent-Free Conditions

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
C. Gabriela Ávila-Ortiz ◽  
Manuel López-Ortiz ◽  
Alberto Vega-Peñaloza ◽  
Ignacio Regla ◽  
Eusebio Juaristi
Keyword(s):  
Michael Addition ◽  
Mandelic Acid ◽  
Addition Reaction ◽  
Solvent Free ◽  
Reaction Intermediates ◽  
Michael Addition Reaction ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Solvent Free Conditions ◽  
The Michael Addition

AbstractThis article describes a study on the Michael addition reaction of cyclohexanone to nitroolefins catalyzed by the chiral secondary amine (1S,4S)-2-tosyl- 2,5-diazabicyclo[2.2.1]heptane. Reactions were carried out under solvent-free conditions to make them more environmentally friendly. Initially, the observed diastereoand enantioselectivities were moderate to good, but were significantly improved by lowering the reaction temperature. Furthermore, a variety of chiral acids were also tested as co-catalysts in both of their enantiomeric forms, which revealed that (R)-mandelic acid affords excellent results in terms of yield and stereoselectivity. Monitoring the reaction by MS-TOF allowed for the detection of key reaction intermediates, and a reasonable reaction mechanism in which both catalysts are involved is proposed.

scholarly journals Catalytic Performance of MgO-Supported Co Catalyst for the Liquid Phase Oxidation of Cyclohexane with Molecular Oxygen

Catalysts ◽  
2017 ◽  
Vol 7 (5) ◽  
pp. 155 ◽  
Author(s):  
Mingzhou Wu ◽  
Yu Fu ◽  
Wangcheng Zhan ◽  
Yanglong Guo ◽  
Yun Guo ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Molecular Oxygen ◽  
Catalytic Performance ◽  
Liquid Phase Oxidation ◽  
Co Catalyst ◽  
Phase Oxidation

scholarly journals Pt Nanocluster Co-Catalysts for Photocatalytic Water Splitting

2018 ◽  
Vol 4 (4) ◽  
pp. 64 ◽  
Author(s):  
Cameron Shearer ◽  
Jason Alvino ◽  
Munkhbayar Batmunkh ◽  
Gregory Metha
Keyword(s):  
Catalyst Activity ◽  
X Ray Diffraction ◽  
Co Catalyst ◽  
X Ray ◽  
Pt Nanoclusters ◽  
Co Catalysts ◽  
Transmission Electron ◽  
Degussa P25 ◽  
Commercial Source ◽  
Photocatalytic Reactions

Degussa P25 is a benchmark form of TiO2 used worldwide in photocatalysis studies. Currently, no such benchmark exists for co-catalysts, which are essential for many photocatalytic reactions. Here, we present the preparation of Pt nanocluster co-catalysts on TiO2 using an unmodified commercial source and equipment that is commonly available. Transmission electron microscopy reveals that the procedure produces TiO2 decorated with Pt atoms and nanoclusters (1–5 atoms). Optical reflectance and X-ray diffraction measurements show that the procedure does not affect the TiO2 polymorph or ultraviolet-visible (UV-Vis) absorbance. Gas phase photocatalytic splitting of heavy water (D2O) shows that the Pt nanocluster-decorated TiO2 outperforms Pt nanoparticle (produced by photodeposition) decorated TiO2 in D2 production. Pt nanoclusters, produced directly from a commercial source, with high co-catalyst activity, are prime candidates to be used in benchmark photocatalytic reactions.

Studien zum Vorgang der Wasserstoffübertragung, 71 [1] Tertiäre Phosphine mit ortho-ständigen chelatisierungsfähigen funktionellen Gruppen als Co-Katalysatoren der Homogenhydrierung mit Rh(I)-Komplexen/Studies on the Occurrence of Hydrogen Transfer, 71 [1] Tertiary Phosphines with Functional Groups in the ortho-Position Capable for Chelatization as Co-Catalysts of the Homogeneous Hydrogenation with Rh(I)-Complexes

1984 ◽  
Vol 39 (4) ◽  
pp. 504-511 ◽  
Author(s):  
Leopold Horner ◽  
Guido Simons
Keyword(s):  
Hydrogen Transfer ◽  
Phenyl Group ◽  
Steric Effects ◽  
Ortho Position ◽  
Homogeneous Hydrogenation ◽  
Compound A ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Tertiary Phosphines ◽  
Tertiary Arsines

By systematic variation of the structure of tertiary phosphines with ortho-phenyl substituted groups as co-catalysts of the homogeneous hydrogenation with Rhodium complexes and hexene-1 as a model compound a collection of data is obtained. By investigating the influence of the variation of the Rhodium/Phosphine-Ratio (Rh/P) (1:1,1 and 1:2,2) on the rate of the hydrogentransfer indirect conclusion can be drawn on the composition of the complexes in the equilibria responsible for the hydrogen transfer.Results: 1. Steric effects of substituents linked to the ortho-position of a phenyl group in the co-catalyst are very important (compare the Tables I-V especially Table VI).2. The rate of hydrogenation is strongly influenced by tertiary phosphines with substituents in a ortho-phenyl group capable for coordination like NR2 and SR. With Rh/P = 1:1,1 the rate of the hydrogenation of hexene-1 is mostly faster as with Rh/P = 1:2,2. Depending on steric effects the rate data can be invers.3. Tertiary arsines with o-dialkylaminophenyl groups are more effective co-catalyst as the corresponding phosphines (Table V).4. Tertiary phosphines with an ortho-alkylmercaptophenyl group (38-41) are weakly active cocatalysts using Rh/P = 1:1,1.The thioether 42 (in compounds 12 the diphenylphosphino group is exchanged by the methylmercapto group) is also a moderate active co-catalyst.5. As a conclusion: it is assumed that complexes of the structure A can coordinate with the substrates hydrogen and olefine . Complexes of the structure B seen to be to stable for the activation of the substrates.

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