Partial Oxidation Of Ethylene Glycol Research Articles

Ni-doped TiO2 supported Pt single-atom catalyst for partial oxidation of ethylene glycol to high-value chemicals in alkaline media

Pt-based electrocatalysts are usually used in several catalytic reactions. However, its high cost, scarcity, and susceptibility towards poisonous intermediate species highly limit these catalysts' large-scale applications. Downsizing catalysts to single-atom scale (SAC) have fascinated extensive research interests due to their higher activity, selectivity, and stability. Herein, we prepared highly active, selective, and poisoning-tolerant PtSACs on Ni-doped TiO2 support (PtSAC-Ni0.1Ti0.9O2). Ni in the catalyst creates a suitable environment to adsorb more OH− and make Pt accessible and ready for further oxidations. Thus, it exhibits higher electrocatalytic performance towards EGO than PtSAC-TiO2 does. It is also by far better than PtNP– Ni0.1Ti0.9O2. The higher catalytic performance by PtSAC-Ni0.1Ti0.9O2 is due to the synergistic effects of Ni and Pt. The catalyst selectively produces glycolate, formate, and hydrogen. Glycolate and formate are high-value chemicals for domestic uses or as inputs for industries to produce other chemicals. The catalyst also shows excellent Faradaic efficiency (>98 %) and stability towards EGO in alkaline media. The strong metal-support interactions between the catalyst and the support retard the agglomeration of the single atoms, thereby increasing their stability.

Electrochemical oxidation of ethylene glycol on TiO2-supported platinum single-atom catalyst into valuable chemicals in alkaline media

The application of single-atom catalysts (SACs) receives excellent attention in producing fine chemicals. SACs demonstrate higher activity, selectivity, stability and are more economical. Herein we designed and successfully synthesized an electrochemical catalyst consisting of Pt single atoms on titanium oxide support (PtSAC/TiO2) via hydrothermal assisted co-precipitation method, which is simple, fast, and efficient. The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image and FT- EXAFS spectra disclose that Pt atoms are well dispersed and show no Pt–Pt coordination. We are the first to apply SACs for partial oxidation of Ethylene glycol (EGO) using PtSAC/TiO2. The strong metal support interaction (SMSI) between Pt and TiO2 and the availability of identical Pt active sites enhanced catalytic selectivity of PtSAC/TiO2. These help EG oxidation on PtSAC/TiO2 to produce glycolate and formate selectively. The higher surface contacts between PtSAC and EG lead to an improved catalytic performance towards EGO. Our stability tests demonstrated that PtSAC/TiO2 showed a slower current decay rate and higher oxidation current density, thus providing better electrocatalytic activity and stability. Hence, PtSAC/TiO2 led to higher reactivity and provided a higher current density response. The as-synthesized PtSAC/TiO2 catalyst exhibits an excellent Faradaic efficiency of 99.7 % and remarkable stability, with a very minimal current drop within 12 h in an alkaline solution.

Silver catalysts for the partial oxidation of alcohols

The review analyzes state of the art in the partial oxidation of alcohols to carbonyl compounds over Ag catalysts, including the partial oxidation of methanol to formaldehyde, oxidation of ethylene glycol to glyoxal, and oxidation of ethanol to acetaldehyde. For the methanol oxidation process, conditions for implementing the BASF and ICI technologies are considered and the entire chain of transformations from natural gas to formaldehyde is estimated in terms of exergy. When considering modern kinetic studies for the partial oxidation of alcohols on silver, some recent publication are analyzed, particularly those devoted to the application of a ring-shaped reactor to suppress the homogeneous steps of formaldehyde decomposition, the development of a new approach to simulation of the process taking into account different reactivity of the catalyst, and the creation of a simulator to calculate the methanol oxidation process using a neural network with a genetic algorithm. Main steps in the development of a technology for the partial oxidation of ethylene glycol to glyoxal on Ag catalysts are briefly described. The author analyzes modern experimental and theoretical works devoted to the formation mechanisms of oxygencontaining active sites on the silver surface and their involvement in the conversion of alcohols to carbonyl compounds, as well as the new Ag-containing catalytic compositions.

First-principles calculation of activity and selectivity of the partial oxidation of ethylene glycol on Fe(0 0 1), Co(0 0 0 1), and Ni(1 1 1)

To recycle ethylene glycol (HOCH2CH2OH) fuel in alkaline fuel cells, active and selective catalysts for partially oxidizing HOCH2CH2OH to glycolic acid (HOCH2COOH) and oxalic acid ((COOH)2) are required at the anode; in other words, complete oxidation of HOCH2CH2OH to CO2 prevents ethylene glycol recycling. We investigate catalyst activity and selectivity for oxidizing HOCH2CH2OH to HOCH2COOH on Fe(0 0 1), Co(0 001), and Ni(1 1 1) via first-principles calculations. We calculate the oxidation reaction path from HOCH2CH2OH to HOCH2COOH without CC bond dissociation to avoid CO2 generation. Partial oxidation of HOCH2CH2OH to HOCH2COOH without CC bond dissociation proceeds as follows: OH bond dissociation of HOCH2CH2OH to generate HOCH2CH2O; CH bond dissociation of HOCH2CH2O to generate HOCH2CHO; CH bond dissociation of HOCH2CHO to generate HOCH2CO; and OH addition to HOCH2CO to generate HOCH2COOH. The activation energies for OH bond dissociation of HOCH2CH2OH and CH bond dissociation of HOCH2CH2O and HOCH2CHO on Fe(0 0 1) are 20.2, 22.8, and 35.2 kcal/mol, respectively, which are the lowest of the three surfaces. Thus, Fe(0 0 1) is most active. To determine the selectivity, we compare the bond dissociation activation energies. The activation energies for CC bond dissociation of HOCH2CH2OH and HOCH2CH2O on Fe(0 0 1) (66.7 and 39.5 kcal/mol, respectively) are higher than those for OH bond dissociation of HOCH2CH2OH (20.2 kcal/mol) and CH bond dissociation of HOCH2CH2O (22.8 kcal/mol), implying that the OH bond of HOCH2CH2OH and CH bond of HOCH2CH2O dissociate before the CC bond dissociation during oxidation on Fe(0 0 1). In contrast, the activation energies for CH and CC bond dissociation of HOCH2CHO (35.2 and 32.8 kcal/mol, respectively) are similar. The CH and CC bonds therefore dissociate during HOCH2CHO oxidation. On Co(0 0 0 1) and Ni(1 1 1), the activation energies for CC bond dissociation of HOCH2CH2O and HOCH2CHO are lower than those for their CH bond dissociation. Therefore, Fe(0 0 1) is more active and selective than Co(0 0 0 1) and Ni(1 1 1) for the partial oxidation of HOCH2CH2OH to HOCH2COOH.

Nitride-based materials SHS-produced from ferroalloys: II. Silicon nitride as a support for Ag-Containing catalysts for partial oxidation of ethylene glycol

Ag-containing catalytic systems immobilized on SHS-produced and acid-leached Si3N4 supports showed good service parameters in partial oxidation of ethylene glycol to glyoxal. Compared to similar catalytic systems on aluminosilicate supports, our catalysts exhibit more uniform distribution of active centers over support surface, narrow size distribution of Ag particles, higher chemical resistance, and lower carbon deposition.

Ethylene glycol oxidation over Ag-containing catalysts: A theoretical study

A theoretical interpretation of the mechanism of ethylene glycol oxidation to glyoxal over Ag-containing catalysts is considered. A model system, reflecting the interaction of Ag cluster with process adsorbates and/or intermediates, is proposed. Both partial oxidation of ethylene glycol to glyoxal and CO2 formation routes are reconstructed, and the corresponding reaction profiles are represented. The roles played by the most important reaction intermediates participating in the process under consideration are discussed.

Active surface formation and catalytic activity of phosphorous-promoted electrolytic silver in the selective oxidation of ethylene glycol to glyoxal

Abstract Unpromoted and phosphorus-promoted electrolytic silver catalysts have been investigated in the partial oxidation of ethylene glycol (EG). It was shown that the addition of the phosphorus-containing promoter on the surface of electrolytic Ag catalyst led to 15–20% increase in glyoxal (GO) yield. The formation mechanism of the active P-containing surfaces of silver catalyst as well as polycrystalline Ag foil has been studied by means of X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD) and scanning electron microscopy (SEM) methods. It was shown that silver clusters located nearby the P-containing Ag surface participate in the ethylene glycol oxidation into glyoxal. The rise of glyoxal selectivity is explained by the absence of low temperature peak at 250 °C in TPD spectra of both P-promoted Ag foil and electrolytic Ag catalysts. This peak was assigned to the decomposition of surface oxide-like species (Ag 2 s O) responsible for deep oxidation of ethylene glycol.

Effect of iodine-containing promoter on the catalytic activity of silver in the course of ethylene glycol oxidation

Surface morphology and catalytic properties of electrolytic silver crystals in partial oxidation of ethylene glycol into glyoxal were studied.

Partial oxidation of polyvalent oxygen substituted compounds on nano-scale gold catalysts

Investigations of the properties of supported nano-scale Au catalysts in the partial oxidation of three different polyvalent oxygen substituted compounds are presented. The relations between Au particle size and catalytic properties of Au/Al2O3 in the partial oxidation of ethylene glycol to glycolic acid as model reaction are discussed. Moreover, influences of the nature of the alumina support and the applied precipitation agent on the catalyst properties were studied. Furthermore, the potential of these catalysts for the industrial interesting partial oxidation of glyoxal to glyoxylic acid was checked. However, it seems that the oxidation of glyoxal is dominated by a CC rupture leading to formic acid, mainly. Finally, the excellent selectivity of gold supported on alumina or titania in the partial oxidation of aldehyde groups of saccharides to carboxylic groups is briefly presented.

Role of the Surface Acid–Base Properties of Silver Catalysts in the Partial Oxidation of Ethylene Glycol

The acid–base properties of a bulk silver catalyst and silver catalysts supported on various carriers for the partial oxidation of ethylene glycol were studied. A relationship between the catalytic activity and the concentration of surface acid sites in the catalysts was found. A mechanism was proposed for the participation of Lewis acid sites in the reaction of partial ethylene glycol oxidation to glyoxal.

Morphological Characteristics of the Products from the Carbonization of the Copper Catalyst in the Partial Oxidation of Ethylene Glycol

The formation of carbonization products in the oxidation of ethylene glycol to glyoxal on a massive sample of copper catalyst was studied by electron microscopy, elemental CH analysis, X-ray phase analysis, and the catalytic flow method. Filamentary, dendritic, and polycrystalline morphological forms of the carbonization products were identified. It was shown that there is a relation between the morphological forms of the carbonization products and the catalytic activity of the copper.

Electrooxidation of ethylene glycol on bismuth-modified Pt(111)

The influence of predosed bismuth upon the electrooxidation kinetics and pathways of ethylene glycol on Pt(111) in 0.1 mol dm–3 HClO4 has been examined by means of voltammetry combined with real-time infrared spectroscopy. On both unmodified and bismuth-modified Pt(111), two major oxidation products, oxalic acid and CO2, are formed via distinct reaction pathways. The presence of predosed bismuth adatoms significantly alters the selectivity of the electrocatalyst in that the production of CO2 increases monotonically with the bismuth coverage at the expense of the oxalic acid yield. The formation of CO2 was also observed starting from oxalic acid and other partial oxidation products, yet bismuth exerts little effect on the reaction kinetics in these cases. Adsorbed CO was also seen to be produced at positive potentials prior to, and during, the electrooxidation of ethylene glycol and especially from aldehyde-containing partially oxidized species. While the presence of predosed bismuth efficiently eliminates adsorbed CO formation from ethylene glycol, it has little effect for the aldehyde reactants. Significantly and surprisingly, the results suggest that ensembles of contiguous active sites are required for the partial oxidation of ethylene glycol to form oxalic acid but not for the exhaustive electrooxidation pathway yielding CO2.

Carbon-carbon bond activation in the 1,2-ethanedioxy heterometallacycle by atomic oxygen on Ag(110)

The effects of coadsorbed oxygen atoms on the decomposition of the 1,2-ethanedioxy surface species (OCH 2CH 2O (a)) formed during the partial oxidation of ethylene glycol (CH 2OH) 2 on the Ag(110) surface has been studied using temperature programmed reaction spectroscopy (TPRS), isotope labelling and high resolution electron energy loss vibrational spectroscopy (EELS). Surface oxygen atoms react with OCH 2CH 2O (a) at 300 K to form gaseous water and formaldehyde, and surface formate (HCOO (a)), which decomposes at 415 K to yield CO 2 and H 2. Through the use of isotopic labelling it was found that the oxygen in the formaldehyde originates solely from the 1,2-ethanedioxy surface species, while in the surface formate one comes from OCH 2CH 2O (a) and the other from coadsorbed oxygen atoms. The kinetic isotope effect for the reaction of adsorbed d 4-1,2-ethanedioxy with surface oxygen indicates that the rate limiting step is the abstraction of a proton from a methylene carbon in OCH 2CH 2O (a) to form OH a and OCHCH 2O (a). Nucleophilic attack by surface oxygen at the carbonyl carbon of OCHCH 2O (a), followed by C-C bond cleavage then releases H 2CO and forms HCOO (a). This study underscores the importance of looking at a wide range of concentrations of the pertinent surface species in order to probe a wider variety of reaction channels.