EtOH Oxidation Research Articles

Ethanol and Methanol Oxidation Activity of PtPb, PtBi, and PtBi2 Intermetallic Compounds in Alkaline Media

The electrocatalytic activities of a wide range of intermetallic bulk compounds in the ethanol (EtOH) and methanol (MeOH) oxidation reactions in alkaline media have been studied, and the results have been compared to those of pure polycrystalline Pt and Pd electrodes. The PtPb, PtBi, and PtBi2 intermetallic compounds appeared to be the most promising electrocatalysts among all of the examined bulk electrodes. The current densities at −0.2 V (vs. Ag/AgCl KCl satd.) for PtPb, PtBi, and PtBi2 in EtOH were 21.4, 7.73, and 6.03 mA cm−2, respectively. All of the other intermetallic bulk electrodes exhibited current densities less than 2.5 mA cm−2. PtPb had the lowest onset potential of −0.58 V for EtOH oxidation, which was 20–30 mV less than that of pure Pt and Pd. The current densities of PtPb were at least seventeen times larger than those of pure Pt and Pd. PtBi and PtBi2, which have onset potentials of −0.51 and −0.45 V, respectively, for the EtOH oxidation reaction exhibited extremely stable oxidation currents of 4.8 and 3.3 mA cm−2 during the constant-potential electrolysis of EtOH. The same behavior was also observed for the MeOH oxidation with PtPb, PtBi, and PtBi2 intermetallic compounds.

The effect of photon source on heterogeneous photocatalytic oxidation of ethanol by a silica–titania composite

The objective of this study was to distinguish the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the silica–titania composite (STC)-catalyzed degradation of ethanol in the gas phase. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp ( λ max = 365 nm) at its maximum light intensity or a UV-C germicidal lamp ( λ max = 254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO 2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s −1) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol CO 2 μmol photons −1). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV-A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy.

High performance microbial 3-D bionanocomposite as a bioanode for a mediated biosensor device

A novel bionanocomposite prepared by a direct mixing of bacterial cells of Gluconobacter oxydans and carbon nanotubes (CNTs) was applied for preparation of a mediated microbial bioanode for ethanol (EtOH) oxidation. The sensitivity of (162 ± 3) μA mM − 1 cm − 2 achieved is the highest among microbial based biosensor devices for EtOH oxidation published to date. Further, high performance of the oxidation process can be underlined by a short response time and a maximal current density of (261 ± 4) μA cm − 2 .

Electrocatalytic Activity for CO, MeOH, and EtOH Oxidation on the Surface of Pt-Ru Nanoparticles Supported by Metal Oxide

This paper describes the electrocatalytic activity for CO, MeOH, and EtOH oxidation on the surface of Pt-Ru nanoparticles supported by metal oxide (Nb-TiO2-H) prepared for use in a fuel cell. To prepare Nb-TiO2-supported Pt-Ru nanoparticles, first, the Nb-TiO2supports were prepared by sol-gel reaction of titanium tetraisopropoxide with a small amount of the niobium ethoxide in polystyrene (PS) colloids. Second, Pt-Ru nanoparticles were then deposited by chemical reduction of the Pt4+and Ru3+ions onto Nb-TiO2supports (Pt-Ru@Nb-TiO2-CS). Nb element was used to reduce electrical resistance to facilitate electron transport during the electrochemical reactions on a fuel cell electrode. Finally, the Pt-Ru@Nb-TiO2-H catalysts were formed by the removal of core-polystyrene ball from Pt-Ru@TiO2-CS at500∘C. The successfully prepared Pt-Ru electrocatalysts were confirmed via TEM, XPS, and ICP analysis. The electrocatalytic efficiency of Pt-Ru nanoparticles was evaluated via CO, MeOH, and EtOH oxidation for use in a direct methanol fuel cell (DMFC). As a result, the Pt-Ru@Nb-TiO2-H electrodes showed high electrocatalytic activity for the electrooxidation of CO, MeOH, and EtOH.

Polymorphisms in the promoter region of the human class II alcohol dehydrogenase (ADH4) gene affect both transcriptional activity and ethanol metabolism in Japanese subjects

Class II alcohol dehydrogenase (pi-ADH), encoded by alcohol dehydrogenase (ADH4), is considered to contribute to ethanol (EtOH) oxidation in the liver at high concentration. Four single nucleotide polymorphisms (SNPs) were found in the promoter region of this gene. Analysis of genotype distribution in 102 unrelated Japanese subjects revealed that four loci were in strong linkage disequilibrium and could be classified into three haplotypes. The effects of these polymorphisms on transcriptional activity were investigated in HepG2 cells. Transcriptional activity was significantly higher in cells with the -136A allele than in those with the -136C allele. To investigate whether this difference in transcriptional activity caused a difference in EtOH elimination, previous data on blood EtOH changes after 0.4 g/kg body weight alcohol ingestion were analyzed. When analyzed based on aldehyde dehydrogenase-2 gene (ALDH2) (487)Glu/Lys genotype, the significantly lower level of EtOH at peak in subjects with -136C/A and -136A/A genotype compared with subjects with -136C/C genotype indicated that -136 bp was a suggestive locus for differences in EtOH oxidation. This effect was observed only in subjects with ALDH2 (487)Glu/Glu. These results suggested that the SNP at -136bp in the ADH4 promoter had an effect on transcriptional regulation, and that the higher activity of the -136A allele compared with the -136C allele caused a lower level of blood EtOH after alcohol ingestion; that is, individuals with the -136A allele may consume more EtOH and might have a higher risk for development of alcohol dependence than those without the -136A allele.

An approach to elucidating photocatalytic reaction mechanisms by monitoring dissolved oxygen: Effect of H2O2 on photocatalysis

We present a method to analyze the photocatalytic oxidation of ethanol (EtOH) in an aqueous TiO2 suspension by measuring the consumption of dissolved oxygen (DO) as a function of varying EtOH and H2O2 concentrations in the suspension. The consumption of DO was analyzed by means of Langmuir–Hinshelwood (L–H) kinetics. The parameter KD-DO calculated from L–H kinetics, defined as (O2 consumption rate constant)(O2 reproduction rate constant)−1, reflects the adsorption equilibrium of EtOH and the photocatalytic reaction mechanisms. The observed KD-DO values for the photocatalytic oxidation of EtOH reflected to the proposed reaction mechanism measured by HPLC and starch–Iodine methods. By using this DO analysis method, we elucidated the photocatalytic reaction mechanism of EtOH oxidation and discussed the effect of H2O2 as active oxygen species on TiO2 photocatalysis.

Catalase mediates acetaldehyde formation in the striatum of free-moving rats

Using brain microdialysis, we measured both ethanol (EtOH) and acetaldehyde (AcH) levels in the striatum of free-moving rats following the inhibition of EtOH oxidation pathways. Rats received intraperitoneal EtOH (1 g/kg) alone or in combination with 4-methylpyrazole (MP, 82 mg/kg, an alcohol dehydrogenase inhibitor), and/or catalase inhibitor sodium azide (AZ, 10 mg/kg) or 3-amino-1,2,4-triazole (AT, 1 g/kg), and/or cyanamide (CY, 50 mg/kg, an aldehyde dehydrogenase inhibitor). Results revealed that both EtOH and AcH concentrations reached a plateau at 30 min after a dose of EtOH, and then gradually decreased for 4 h. AcH was identified in the CY + EtOH, CY + AT/AZ + EtOH, and CY + 4-MP + EtOH groups. The CY + EtOH-induced peak AcH level was 195.2 ± 19.4 μM, and this level was significantly higher than the values in other groups studied. The catalase or ADH inhibitor in combination with CY lowered considerably the AcH concentration in the brain. The EtOH level reached a maximum of 25.9 ± 2.3 mM in the CY + 4-MP + EtOH group, and this level was markedly higher than in the EtOH group. No significant difference in brain EtOH levels was seen in any of the other groups examined. The findings strongly support the assumption that the enzyme catalase plays a significant role in AcH formation directly in the rat brain.

Michaelis-Menten elimination kinetics of acetaldehyde during ethanol oxidation.

Acetaldehyde (AcH) is a toxic metabolite of ethanol (EtOH). The pharmacokinetics of blood AcH during EtOH oxidation was studied with or without the administration of aldehyde dehydrogenase 2 inhibitor (cyanamide) in rabbits. An bolus of EtOH saline solution (0.25, 0.5, 1.0, 1.5, and 2.0 g/kg) was injected intravenously. Cyanamide was administered intraperitoneally (25 mg/kg body weight) to the cyanamide-treated group. Blood EtOH and AcH concentrations were measured by using head-space gas chromatography. In the control group, the first peak of the blood AcH appeared immediately and the second elevation appeared 1 to 4 hr after administration at a high EtOH dose. The blood AcH levels other than the second elevation part were significantly correlated to the blood EtOH levels. In the cyanamide-treated group, a peak and a plateau formed at the time corresponding to the second peak in the control group. The peak and plateau concentration of AcH increased markedly. We attempted simultaneous curve fitting, using the five blood EtOH and AcH concentration-time curves, to determine the pharmacokinetic model. Consequently, the AcH elimination was best described by a Michaelis-Menten kinetic model in both groups. The blood AcH profile was suggested to consist of the first and second components that are related to the blood EtOH concentration itself and the metabolic formation of AcH, respectively. With higher EtOH doses or aldehyde dehydrogenase 2 inhibition, the second component becomes prominent as a result of the capacity-limited property of the metabolism of AcH, which is described by Michaelis-Menten elimination kinetics.

Detection of Ascorbic Acid in an Ethanol–Water Mixed Solution on a Conductive Diamond Electrode

Abstract Conductive boron-doped diamond thin-film electrodes have been shown to be highly suitable as electrochemical detectors in flow injection analysis (FIA) due to the lack of electrode deactivation due to fouling and the ability to withstand highly positive electrochemical potentials. In the present work, a diamond electrode was applied to the detection of ascorbic acid (AA) in an alcohol–water mixed solution. During FIA of AA in an ethanol (EtOH)–water solution including 0.1 M NaClO4, the interference from EtOH oxidation that would have been observed with a Pt electrode was avoided, and the amperometric response for AA was observed with the use of a conductive diamond as the electrode material. Moreover, The detection limit for AA that could be observed was lower than that for a glassy carbon electrode, because diamond exhibits a lower background current, smaller background noise, and smaller injection noise. These findings suggest that the diamond electrode may be applied in the detection of other redox-active impurities and added substances in alcohol or alcohol–water solutions, such as chlorophyll, nicotinamide, caffeine, riboflavin, and dl-α-tocopherol.

Michaelis‐Menten Elimination Kinetics of Acetaldehyde During Ethanol Oxidation

Background Acetaldehyde (AcH) is a toxic metabolite of ethanol (EtOH). The pharmacokinetics of blood AcH during EtOH oxidation was studied with or without the administration of aldehyde dehydrogenase 2 inhibitor (cyanamide) in rabbits.Methods An bolus of EtOH saline solution (0.25, 0.5, 1.0, 1.5, and 2.0 g/kg) was injected intravenously. Cyanamide was administered intraperitoneally (25 mg/kg body weight) to the cyanamide‐treated group. Blood EtOH and AcH concentrations were measured by using head‐space gas chromatography.Results In the control group, the first peak of the blood AcH appeared immediately and the second elevation appeared 1 to 4 hr after administration at a high EtOH dose. The blood AcH levels other than the second elevation part were significantly correlated to the blood EtOH levels. In the cyanamide‐treated group, a peak and a plateau formed at the time corresponding to the second peak in the control group. The peak and plateau concentration of AcH increased markedly. We attempted simultaneous curve fitting, using the five blood EtOH and AcH concentration‐time curves, to determine the pharmacokinetic model. Consequently, the AcH elimination was best described by a Michaelis‐Menten kinetic model in both groups.Conclusions The blood AcH profile was suggested to consist of the first and second components that are related to the blood EtOH concentration itself and the metabolic formation of AcH, respectively. With higher EtOH doses or aldehyde dehydrogenase 2 inhibition, the second component becomes prominent as a result of the capacity‐limited property of the metabolism of AcH, which is described by Michaelis‐Menten elimination kinetics.

Role of substrate utilization and thermogenesis on body-weight control with particular reference to alcohol.

Alcohol (ethanol; EtOH) provides fuel energy to the body (29.7 kJ (7. 1 kcal)/g, 23.4 kJ (5.6 kcal)/ml), as do other macronutrients, but no associated essential nutrients. The thermogenic effect of EtOH (on average 15 % of its metabolizable value) is much greater than that of the main substrates utilized by the body, i.e. fat and carbohydrates (CHO), suggesting a lower net efficiency of energy utilization for EtOH than for fat and CHO. EtOH cannot be stored in the body and is toxic, so that there is an obligatory continuous oxidation of EtOH and it becomes the priority fuel to be metabolized. In contrast to CHO, its rate of oxidation does not depend on the dose ingested. As with CHO intake, it engenders a shift in postprandial substrate utilization (decrease in fat oxidation), but by a non-insulin-mediated mechanism. A limited amount of EtOH can be converted to fatty acids by hepatic de novo lipogenesis (as occurs with high levels of CHO feeding) from acetate production, which inhibits lipolysis in peripheral tissues. There is no evidence that EtOH consumed under normoenergetic conditions (i.e. isoenergetically replacing CHO or fat) leads to greater body fat storage than fat or CHO. However, there is still a lack of experimental studies on the influence of EtOH on the level of spontaneous physical activity in man. This effect may well depend on the dose of EtOH consumed as well as other intrinsic factors.

Partial oxidation of light alkanes by reductively activated oxygen in Eu-catalytic system at 40°C

Oxidation of light alkanes, CH4, C2H6, and C3H8, could be performed at 40°C by using the EuCl3-catalytic system (EuCl3, O2, Zn0, and CF3CO2H). In the case of CH4 oxidation, MeOH was produced from CH4 but CO2 from CF3CO2H could not be avoided. However, selective oxygenations of C2H6 (89% selectivity) and C3H8 (91%) could be performed. In the oxidation of C2H6, EtOH was primary product and the successive oxidation of EtOH gave MeCHO and CO2. Regio-selectivities (1°:2°) observed in the oxidation of C3H8 suggested that an electrophilic active oxygen species was generated in the EuCl3-catalytic system. This active oxygen could not oxidize C-H bonds of MeOH (CF3CO2Me) because of a strong electron-withdrawing effect of CF3CO-group. Eu2+ species produced by the reduction with Zn0 was studied by UV-visible spectra. The spectral data proposed that O2 was reductively activated through the redox of Eu3+/Eu2+.

Electrocatalytic Oxidation of Small Carbohydrate Fuels at Pt−Sn Modified Electrodes

The electrocatalytic oxidations of water-soluble alcohols and diols and some other small organic molecules (MeOH, EtOH, 2-fluoroethanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, CH2(OH)2, ethylene glycol, n-PrOH, i-PrOH, 1,4-butanediol, 1,3-propanediol, 1,2-propanediol, t-BuOH, neopentyl alcohol, benzyl alcohol, 2-Me-1-PrOH, formic acid, acetaldehyde, acetic acid, propionaldehyde, propionic acid, acetone, glycolaldehyde, glyoxal, glycolic acid, glyoxylic acid, oxalic acid) have been compared in aqueous 0.5 M H2SO4 at C and Au electrodes modified with an electrodeposited Pt−Sn catalyst at low (−0.1 to 0.5 V vs SCE) potentials. The Pt−Sn catalyst is electrochemically deposited and forms as a smooth deposit on Au electrodes. At a catalyst loading of ∼0.5 mg/cm2 the electrodeposition of the Pt−Sn catalyst results in formation of adherent ∼0.8 μm size particles on C electrodes. In general, for organic molecules containing only C, H, and O with two or more carbon atoms, the presence of H atoms on both the α- and β-carbon results in a relatively negative potential for onset of catalytic current (usually between −0.1 and −0.2 V vs SCE) at Pt−Sn compared to Pt alone. Of the alcohols and diols studied, formaldehyde (which exists in aqueous solutions as the hydrated form, CH2(OH)2) shows the highest electrocatalytic currents at the Pt−Sn catalyst. The ultimate product, via HCOOH, is CO2. EtOH is oxidized only to acetic acid on Pt−Sn electrodes. The EtOH and n-PrOH oxidation yields, determined by exhaustive electrolysis, are 4 e- per molecule, while i-PrOH yields only 2 e- per molecule. We confirmed the generation of acetic acid, propionic acid, and acetone as the final products for the oxidations of EtOH, n-PrOH, and i-PrOH, respectively, by 13C NMR and/or GCMS. The electron yield of the oxidation of ethylene glycol at Pt−Sn surfaces is only 4 e- per molecule instead of the value of 8 e- per molecule expected for the oxidation of ethylene glycol to oxalic acid. Glycolic acid (CHOCOOH) is the oxidation product by GCMS. This substance is not electrocatalytically oxidized on Pt−Sn at potentials negative of ∼ +0.4 V vs SCE in comparison to the −0.1 V vs SCE onset for ethylene glycol oxidation. MeOH, the molecule with the highest electron yield on Pt−Sn (6 e- per molecule), unfortunately shows the most positive potential onset for oxidation among the group of alcohols compared in this study, while the two intermediates along the path of oxidation to CO2, formaldehyde, and formic acid are oxidized on Pt−Sn at very negative potentials compared to MeOH. Thus, the conversion of MeOH to formaldehyde is the efficiency-determining step in the oxidation of MeOH to CO2.

Ethanol and acetaldehyde metabolism in cultured hepatocytes from chronic alcoholic rats

In this study the authors analyzed ethanol (Et-OH) and acetaldehyde (Ac-CHO) metabolism in cultured hepatocytes isolated from chronic alcoholic rats. Hepatocytes were isolated and cultured from two groups of rats, one was fed with a liquid diet containing Et-OH and another was pair-fed with a control diet for 4 weeks. After 48 hours of the primary culture, Et-OH was added to the culture medium at a final concentration of 5 mM with or without 2 mM 4-methyl pyrazole (Py). Serial changes of Et-OH and Ac-CHO levels in the medium for 48 hours were determined in 4 groups of the alcohol alone, alcohol-Py, control and control-Py groups. In the alcohol alone and control groups, Et-OH disappearance rates (EDR), which are roughly equivalent to Et-OH oxidation rates in the hepatocytes, were significantly higher than those in the corresponding Py treated groups. In the two alcoholic groups, the EDR was significantly higher than those in the corresponding control groups. In cultured hepatocytes, 75-80% of Ac-CHO produced from Et-OH was oxidized. The increasing rates of Ac-CHO (AcICR), a function of Ac-CHO production and oxidation rates in the hepatocytes, increased in parallel with the increase in the EDR. However, the AcICR/EDR rate, which is a parameter of the Ac-CHO oxidation rate in the hepatocytes, was not different among the 4 groups. These results indicate that the cultured cells maintain the characteristics of Et-OH metabolism in chronic alcoholic rats and may also be used for the study of Et-OH and Ac-CHO metabolism as an in vitro model.

Kinetics of oxidation of ethanol, isopropyl alcohol, and benzyl alcohol by [ethylenebis(biguanide)]silver(III) cation in aqueous perchloric acid solutions

In aqueous acid solutions, the complex [Ag(H2L)]3+(H2L = ethylenebis(biguanide)] quantitatively oxidises ethanol, isopropyl alcohol, and benzyl alcohol to the corresponding carbonyl products at moderate rate. The experimental rate law is –d[complex]/dt=(k1+k2/[H+])[alcohol][complex]. At 40 °C and I= 1.0 mol dm–3, 105k1, (dm–3 mol–1 s–1) and 106k2(s–1) values are: EtOH, 4.2 ± 0.3 and 2.8 ± 0.1; PriOH, 7.5 ± 0.5 and 4.8 ± 0.2; PhCH2OH, 95 ± 6 and 32.5 ± 2 respectively. The upper limit for the rate of reaction of [Ag(H2L)]3+ with methanol, t-butyl alcohol, ethylene glycol, and glycerol is the rate of autodecomposition of [Ag(H2L)]3+ and is less than 10% of the rate of oxidation of EtOH, PriOH, or PhCH2OH. Deprotonation of the alcohols assisted by axial co-ordination to [Ag(H2L)]3+ is suggested as a source of the inverse acid dependence. The whole reaction course is e.s.r. silent and a rate-determining C–H bond cleavage in the –CHOH group appears reasonable. Compared to other metal-ion oxidants, [Ag(H2L)]3+ appears to be the most selective reagent for PhCH2OH.

Characterization of the cytochrome P-450 monooxygenase system of hamster liver microsomes: Effects of prior treatment with ethanol and other xenobiotics

The cytochrome P-450 monooxygenase system of hamster liver microsomes and its response to prior treatment with ethanol and other xenobiotics have been examined. Male Syrian golden hamsters were administered ethanol (ETOH), phenobarbital (PB), 5,6-benzoflavone (BF) or isoniazid (INH). Each treatment resulted in a moderate increase (20–60%) in the specific content of liver microsomal cytochrome P-450 along with a unique hemeprotein ferrous carbonyl Soret maximum. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of liver microsomes revealed distinctive changes in protein banding patterns in the cytochrome P-450 (45–60 kDa) region with each treatment. NADPH : cytochrome c reductase activity was increased by both PB and INH, whereas cytochrome b 5 content was increased by INH only. Microsomal oxidation of ETOH and aniline p-hydroxylation (expressed per nmol cytochrome P-450) were enhanced dramatically by ETOH and INH, whereas PB and BF had no effect on these enzymatic activities. Both ETOH and INH also increased zoxazolamine 6-hydroxylation but, in contrast to other rodent species, this drug-metabolizing activity was decreased in hamster liver microsomes after treatment with either PB or BF. Microsomal benzphetamine N-demethylation was decreased by ETOH, INH and BF administration and was only modestly enhanced after treatment with PB. ETOH and INH had no effect on the O-dethylation of 7-ethoxycoumarin, and enzymatic activity increased by BF but decreased by PB. These results demonstrate that the cytochrome P-450-dependent monooxygenase system of hamster liver microsomes responds to treatment with ETOH and other xenobiotics in a manner that is quantitatively and, in certain respects, qualitatively different from that reported for the rat, rabbit, and mouse.

Inhibition by nicotinic acid of hepatic steatosis and alcohol dehydrogenase in ethanol-treated rats

A single intoxicating dose of ethanol (6.0 g/kg) depressed the NAD: NADH 2 ratio and increased the NADPH 2: NADP ratio in rat liver. Nicotinic acid (NA) treatment prevented the accumulation of nonesterified fatty acid (NEFA), total fats, and neutral fats in the liver of rats given ethanol (EtOH); it also kept blood EtOH elevated. We postulate that NA acted by blocking EtOH oxidation—a block apparently exerted by inhibition of alcohol dehydrogenase (ADH), mediator of the principal oxidative pathway of ethanol metabolism. It was inferred that NA inhibits the enzyme by binding at the adenosine diphosphate ribose site since the addition of Zn 2+ in vitro failed to reverse the NA inhibition of rat liver ADH. Blockage at the aforementioned site would thus inhibit coenzyme (NAD) binding to the apoenzyme, resulting in a block in the EtOH oxidation.