Presence Of Formic Acid Research Articles

Carbon nanotubes covalent combined with graphitic carbon nitride for photocatalytic hydrogen peroxide production under visible light

The carbon nanotubes (CNTs) have been combined with graphitic carbon nitride (g-C3N4) through the amidation reaction. The hybrid catalyst of g-C3N4-CNTs with well-defined and stable structure exhibits efficient catalytic performance (32.6μmolh−1) for photocatalytic H2O2 production in the presence of formic acid under visible light. The value of electron transfer during the oxygen reduction reaction (ORR) process obtained from the Koutecky-Levich plot for g-C3N4-CNTs (n=1.96) is higher than that for g-C3N4 (n=1.29), suggesting that the CNTs covalent combined with g-C3N4 can promote the electrons generation. The p-benzoquinone (PBQ) scavenger experiments, the electron spin resonance (ESR) signal and quantitative experiment of O2− results reveal that the negative shifts of the conduction band (CB) level from g-C3N4 to g-C3N4-CNTs can enhance the single-electron reduction of O2 to O2− and further promote the sequential two-step single-electron O2 reduction reaction to H2O2.

SYNTHESIS, CHARACTERISATION AND ANTIFUNGAL ACTIVITYOF SOME NEWLY SYNTHESISED POLYSUBSTITUTED PYRAZOLES

A novel series of polysubstituted pyrazoles were synthesised by the cyclization of (α phenoxy/octyl) acetyl aryl hydrazones in presence of formic acid, by refluxing (α-phenoxy/octyl) acetic acid hydrazide and substituted aryl aldehyde, using C2H5OH as solvent. The newly synthesised compounds were characterised by IR, 1H NMR spectra and also screened for their promising biological activity i.e. antifungal activity.

Inhibition analysis of inhibitors derived from lignocellulose pretreatment on the metabolic activity of Zymomonas mobilis biofilm and planktonic cells and the proteomic responses.

Lignocellulose pretreatment produces various toxic inhibitors that affect microbial growth, metabolism, and fermentation. Zymomonas mobilis is an ethanologenic microbe that has been demonstrated to have potential to be used in lignocellulose biorefineries for bioethanol production. Z. mobilis biofilm has previously exhibited high potential to enhance ethanol production by presenting a higher viable cell number and higher metabolic activity than planktonic cells or free cells when exposed to lignocellulosic hydrolysate containing toxic inhibitors. However, there has not yet been a systematic study on the tolerance level of Z. mobilis biofilm compared to planktonic cells against model toxic inhibitors derived from lignocellulosic material. We took the first insight into the concentration of toxic compound (formic acid, acetic acid, furfural, and 5-HMF) required to reduce the metabolic activity of Z. mobilis biofilm and planktonic cells by 25% (IC25 ), 50% (IC50 ), 75% (IC75 ), and 100% (IC100 ). Z. mobilis strains ZM4 and TISTR 551 biofilm were two- to three fold more resistant to model toxic inhibitors than planktonic cells. Synergetic effects were found in the presence of formic acid, acetic acid, furfural, and 5-HMF. The IC25 of Z. mobilis ZM4 biofilm and TISTR 551 biofilm were 57 mm formic acid, 155 mm acetic acid, 37.5 mm furfural and 6.4 mm 5-HMF, and 225 mm formic acid, 291 mm acetic acid, 51 mm furfural and 41 mm 5-HMF, respectively. There was no significant difference found between proteomic analysis of the stress response to toxic inhibitors of Z. mobilis biofilm and planktonic cells on ZM4. However, TISTR 551 biofilms exhibited two proteins (molecular chaperone DnaK and 50S ribosomal protein L2) that were up-regulated in the presence of toxic inhibitors. TISTR 551 planktonic cells possessed two types of protein in the group of 30S ribosomal proteins and motility proteins that were up-regulated.

Kinetics and related studies of the formation of 2,3‐dihydroquinazolin‐4(1H)‐ones in the presence of different benzaldehyde derivatives

AbstractThe kinetics and activation parameters for the reaction between 2‐amino‐benzamide and some benzaldehyde derivatives in the presence of formic acid have been reported and discussed. A linear plot of lnk vs l/T showed that the reactions obey the Arrhenius equation. Both the Arrhenius and the Eyring equations were used to calculate the activation energy. The effect of nitro groups was studied on different positions of benzaldehyde. For all substituents, the reactions followed second‐order kinetics, and the partial orders of reactions were recognized with respect to each reactant. Comparisons between the magnitudes of ΔH‡ and TΔS‡showed that the reactions were enthalpy controlled. The validity of the isokinetic relationship and the compensation effect was tested, and the isokinetic temperature (β) was obtained. A linear enthalpy‐entropy plot (ΔH‡versusΔS‡) showed that the compensation effect is established, and this process occurs via a same mechanism across a series of reactions. From the Van't Hoff and Exner's plots, the isokinetic temperature was obtained.

Palladium Nanoparticles Decorated Graphene Oxide: Active and Reusable Nanocatalyst for the Catalytic Reduction of Hexavalent Chromium(VI)

AbstractToday, the catalytic reduction of Cr(VI) to Cr(III) stands one of the most important challenges in the environmental chemistry and catalysis due to highly stable, contaminant and toxic nature of Cr(VI). In this study, we show that a new nanocatalyst system comprised of 3‐aminopropyltriethoxysilane (APTS) stabilized palladium(0) nanoparticles grafted onto the surface of graphene oxide (Pd/GO) efficiently works in the catalytic reduction of Cr(VI) to Cr(III) under mild reaction conditions. Pd/GO nanocatalyst was reproducibly prepared through two‐steps procedure: (i) H2 reduction of Pd(dba)2 (dba=dibenzylideneacetone) in the presence of APTS in THF to synthesize colloidal APTS stabilized palladium(0) nanoparticles and then (ii) the deposition of 3‐aminopropyltriethoxysilane stabilized palladium(0) nanoparticles onto the surface of graphene oxide (GO) by impregnation. The characterization of Pd/GO was carried out by advanced analytical techniques. The summation of the results acquired from these analyses reveals that the formation of well‐dispersed and highly crystalline palladium(0) nanoparticles on the surface of GO. The catalytic performance of the resulting Pd/GO in terms of activity and stability was assessed in the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid (HCOOH) as a reducing agent. We found that Pd/GO nanocatalyst exhibits high activity (TOF=3.6 mol Cr2O72−/mol Pd×min) and reusability (> 90% at 5th reuse) in this catalytic transformation at room temperature.

Speciation of As in environmental samples using the nano-TiO2/PCHG-FAAS online system

ABSTRACTThis work presents an alternative method for arsenic speciation using the nano-TiO2 hydride generation photocatalytic hydride generation (PCHG) system, which is easily separated from the medium. Nano-TiO2 was studied as photocatalyst to reduction of arsenic species by UV-induced with formic acid and atomic absorption detection of different forms of arsenic [As (III), As (V), dimethylarsinic acid (DMA)] in environmental samples (water, sediment and plant). The effect of the average pH, the organic acid concentration, the ultraviolet irradiation time and their amount were investigated. With the presence of formic acid, the process was more effective in the reduction of arsenic when compared to other organic acids, mainly acetic acid. In addition, the photocatalytic hydride generation and flame atomic absorption spectrometry (nano-TiO2/PCHG-FAAS) increased the identification and quantification of different arsenic species. The ultrasound extraction procedure was used as a method to prepare samples with solutions of 1.0 mol L−1 phosphoric acid. The accuracy of the measurements (n = 12), calculated as relative standard deviation, was less than 8.6%. The detection limits for As (III) and As (total) in samples were 0.418 and 0.574 μg g−1, respectively.

Further Observations on the Mechanism of Formic Acid Decomposition by Homogeneous Ruthenium Catalyst

AbstractFormic acid is well known as a hydrogen source and a hydrogen donor under thermal, catalytic and photocatalytic conditions. In this study, we generate hydrogen and carbon dioxide in a ratio of 1:1 by decomposing formic acid in presence of a homogeneous ruthenium catalysis under mild conditions. At 40oC TOF>600 h−1 was realized. The catalyst is stable and robust through numerous cycles of the decomposition reaction. Furthermore, maintaining the active catalyst system under ambient conditions for months caused no harm to its vitality. The catalytic activity could be restored instantly at any time simply by adding formic acid and heating to 40oC. Over the years, scientists have suggested different incomplete schemes for the decomposition reaction based on experimental and theoretical studies. In this paper we propose a novel molecular mechanism for this reaction.

Optimization of Epoxidized Methyl Acetoricinoleate Synthesis by Response Surface Methodology

AbstractEpoxidized methyl acetoricinoleate (EMAR) was generated by epoxidation of methyl acetoricinoleate (MAR) in the presence of formic acid and hydrogen peroxide by using ionic liquids as catalysts, and the product was characterized by means of infrared spectroscopy and mass spectrometry. The efficiencies of four different catalysts, 1‐methylimidazole hydrogen sulfate salt ([Hmim]HSO4), 1‐methylpyrrolidone hydrogen sulfate salt ([Hnmp]HSO4), phosphoric acid, and sulfuric acid, were compared. The effects of the formic acid/MAR molar ratio, hydrogen peroxide/MAR molar ratio, reaction temperature, reaction time, and catalyst dosage on the epoxy value of EMAR were investigated by single‐factor experiments.

Photo enhanced detoxification of chromium (VI) by formic acid using 3D palladium nanocatalyst

The detoxification of Cr(VI) to Cr(III) at room temperature by formic acid is investigated in the presence of 3D urchin shaped monometallic palladium (Pdurc) nanocatalyst. The rate of detoxification reaction is found to enhance with the intensity of light. Kinetic analysis reveals that the detoxification of Cr(VI) in presence of Pdurc nanocatalyst is most efficient in sunlight with a pseudo-first-order rate constant of 0.274 ± 0.067 min−1 as compared to commercially available Pd/C nanoparticles and radiolytically synthesized spherical Pd nanoparticles. The synergistic effect of high surface area of porous Pdurc nanocatalyst and higher rate of photodecomposition of formic acid in presence of Pdurc is proposed for the photo enhanced catalytic conversion of Cr(VI) to Cr(III). The reaction mechanism is confirmed by increase in the evolution of carbon dioxide (CO2) in the presence of light, monitored using gas chromatography. The sunlight enhanced conversion of Cr(VI) to Cr(III) in aqueous media, under ambient reaction condition, room temperature, low catalyst loading and recyclability of the Pdurc nanocatalyst will be helpful in developing new strategies for the detoxification of waste water.

Ruthenium and Iridium Dipyridylamine Catalysts for the Efficient Synthesis of γ-Valerolactone by Transfer Hydrogenation of Levulinic Acid

The selective and efficient transfer hydrogenation of levulinic acid into γ-valerolactone was performed with new ruthenium and iridium catalysts bearing dipyridylamine (dpa) ligands. Reactions were performed in the presence of formic acid and triethylamine using catalyst loading as low as 0.05 mol % with a ruthenium complex (turnover number = 1980). Recyclability of a ruthenium catalyst was demonstrated by running 6 consecutive reactions in almost quantitative yields.

Polarized behaviour of lead anode with 0,8 % silver in synthetic solution for electrollytic zinc precipitation in presence of depolarized substances

At density current of 400A/m2, average voltage of electrolytic cell in zinc industrial production is approx. 3,7V, making anode potential approx. 2,0V. In the process of electrolysis, almost 80% of electric energy is spent, so there is a great economic interest to reduce specific electric energy consumption per zinc mass unit. The solution of this problem can be found in reducing anode potential (depolarization) by adding, in electrolyte, the substances that oxidize at potentials lower than the one of water oxidation. This paper examined the behaviour of anode potential by adding 1, 3, 5 and 8% (vol) methanol, i.e. 1, 3 and 5% (vol) formic acid in synthetic industrial electrolyte with 150g/dm3 H2SO4, as well as the influence of chloride presence in electrolyte on anode polarization effects. Lead anode alloyed with 0,8% silver was used, being a standard for zinc industrial production. Corrosion behavior of such an anode was examined in presence of methanol in synthetic industrial electrolyte with 150g/dm3 sulphuric acid. The results show that in the field of industrial relevant density current, depolarization effect while adding methanol exists, that the presence of methanol doesn't affect adversely on corrosion stability of anode, but the acceptable content of chloride in electrolyte cancels the effects of depolarization in the presence of methanol. The presence of formic acid in synthetic electrolyte doesn't show clear and uniform depolarization effects.

Novel application of metal-free graphitic carbon nitride (g-C3N4) in photocatalytic reduction—Recovery of silver ions

Metal-free graphitic carbon nitride (g-C3N4) photocatalyst was synthesized by simple pyrolysis of urea without additive assistance. The prepared photocatalyst was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and UV–Visible diffuse reflectance spectroscopy (DRS). The photoreduction and recovery of the precious silver metal from aqueous solution, in the presence of formic acid as scarifying substance, has been carried out using the prepared material under simulated sunlight. Different photoreduction conditions have been investigated in order to determine the optimal conditions. The best efficiency of Ag+ photoreduction has been achieved using 100ppm g-C3N4 photocatalyst and formic acid, as hole scavenger, when pH of the medium was set at 4. The low photocatalyst dose confirms that g-C3N4 is a promising photocatalyst for silver reduction and recovery.

Sustainable Transparent Conducting Oxide Nanomaterials; Aluminium- and Gallium-Co-Doped Zinc Oxide (AGZO)

Transparent conducting oxide (TCO) nanoparticles based on zinc oxide doped with aluminium and gallium (Al- and Ga-co-doped ZnO, AGZO) were synthesized using a continuous hydrothermal flow synthesis (CHFS) reactor by rapid hydrolysis and dehydration of aqueous metal salt precursors, in the presence of formic acid as an in-process reducing agent. The as-synthesised powders were characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The as-synthesised powders were pressed into ceramic compacts and heat-treatment to ensure phase-pure wurtzite structure. The electrical properties of the materials were evaluated by Hall Probe measurements on the compacts, showing resistivities as low as 4.55 × 10−2 Ω cm, which represents a very high conductivity for a pressed disc based on ZnO.

Hybrid Copper-Silver Conductive Tracks for Enhanced Oxidation Resistance under Flash Light Sintering.

We developed a simple method to prepare hybrid copper-silver conductive tracks under flash light sintering. The developed metal nanoparticle-based ink is convenient because its preparation process is free of any tedious washing steps. The inks were composed of commercially available copper nanoparticles which were mixed with formic acid, silver nitrate, and diethylene glycol. The role of formic acid is to remove the native copper oxide layer on the surface of the copper nanoparticles. In this way, it facilitates the formation of a silver outer shell on the surface of the copper nanoparticles through a galvanic replacement. In the presence of formic acid, the copper nanoparticles formed copper formate, which was present in the unsintered tracks. However, under illumination by a xenon flash light, the copper formate was then converted to copper. Moreover, the resistance of the copper-only films increased by 6 orders of magnitude when oxidized at high temperatures (∼220 °C). However, addition of silver nitrate to the inks suppressed the oxidation of the hybrid copper-silver films, and the resistance changes in these inks at high temperatures were greatly reduced. In addition, the hybrid inks proved to be advantageous for use in electrical circuits as they demonstrated a stable electrical conductivity after exposure to ambient air at 180 °C.

Peroxide oxidative desulfurization of a mixture of nonhydrotreated vacuum gas oil and diesel fraction

Oxidative desulfurization of a model mixture on the basis of vacuum gas oil and diesel fuel by hydrogen peroxide in the presence of formic acid has been studied. A technology of a two-phase system with a phase-transfer catalyst has been employed for the desulfurization. The optimum reaction time is 6 h and the hydrogen peroxide: sulfur molar ratio is 4: 1. As a result of successive triple oxidative desulfurization, 90% of total sulfur is removed from the model mixture.

An experimental investigation of substituent effects on the formation of 2,3-dihydroquinazolin-4(1H)-ones: a kinetic study

The effect of different substituents on the kinetics of the reactions between 2-amino-benzamide and some of benzaldehyde derivatives have been spectrally investigated in the presence of formic acid. The proposed mechanism were challenged due to the determination of rate-determining step (RDS) and also, to obtain the general rate law of the reaction. For all substituents, the reactions followed the second-order kinetics and the partial orders of reactions were recognized with respect to each reactant. Electron withdrawing substituents on benzaldehyde ring increased the rate of reaction. Kinetic values (k and Ea) and associated activation parameters (ΔH‡, ΔG‡ and ΔS‡) of the reactions were determined. Both the Arrhenius and the Eyring equations were used to calculate activation energy. Comparison of magnitude of and T showed that the reactions were enthalpy controlled. Isokinetic plots for the reactions were plotted and linear relationship between and recognized that relative contribution of enthalpy and entropy to the overall free energy was the same in the reactions.

Reduction of nitrate by heterogeneous photocatalysis over pure and radiolytically modified TiO2 samples in the presence of formic acid

Heterogeneous photocatalytic reduction of nitrate (2mM) in the presence of formic acid (FA, 10mM) using pure and modified TiO2 samples under UV–vis irradiation was performed at pH 3, and the evolution of the intermediate and final products was analyzed. For this work, commercial samples (Evonik P25 and Cristal Global PC500 and PC10) were modified by γ-radiolysis with two noble metal nanoparticles known to behave differently in NO3− transformation, Ag and Pd. P25 was modified with Ag (0.5 and 2%w/w), while PC10 and PC500 were modified with Pd (1%w/w). The order of the photocatalytic activity of the materials for NO3− transformation was 2 Ag-P25>PC500>0.5 Ag-P25≈P25≫1 Pd-PC500>PC10>1 Pd-PC10. Nitrite formation was observed in all cases but at low amounts, and its concentration was negligible (≤1μM) after complete NO3− reduction. Ammonium was found as final product and remained in considerable amounts at the end of the irradiation. The nitrogen balance accounted for a large amount of non-identified nitrogen products formed during the photocatalytic reaction, probably N2 or NO; this amount was higher for the P25 and PC500 pure samples. The efficiency on the use of FA as donor was evaluated and PC500 was found to be the most efficient sample in this sense. A mechanism is proposed to clarify the still not well understood process of TiO2 heterogeneous photocatalytic transformation of nitrate, based on literature data and detected products.

Photoinduced Reduction of Nitroarenes Using a Transition-Metal-Loaded Silicon Semiconductor under Visible Light Irradiation

We investigated transition-metal-loaded silicon nanoparticles for the photocatalytic reduction of nitroarene derivatives in the presence of formic acid under visible light irradiation. Formic acid assumes the role of both a hydrogen source and a sacrificial reagent for the introduction of electrons into the generated holes of semiconductors. As such, in the presence of formic acid, photocatalytic reactions smoothly proceed under mild conditions without gaseous hydrogen. In particular, palladium-loaded silicon (Pd/Si) was the most suitable catalyst for the conversion of nitrobenzene to aniline, compared to Pt/Si, Ru/Si, and Pd/C.

Red-Light Initiated Decomposition of α-Hydroxy Methylperoxy Radical in the Presence of Organic and Inorganic Acids: Implications for the HOx Formation in the Lower Stratosphere.

Theoretical calculations have been carried out to investigate the gas-phase decomposition of α-hydroxy methylperoxy (HOCH2(OO)) radical in the absence and presence of formic acid, acetic acid, nitric acid, and sulfuric acid. The HOCH2(OO) radical decomposition represents a new source of the HOx radical in troposphere. The results suggest that sulfuric acid will be more effective than other acids in catalyzing the peroxy radical decomposition. However, the significant stability of prereaction and postreaction complexes in all the bimolecular reactions implies a new photomechanism for the acid-mediated decomposition of the HOCH2(OO) radical that involves the visible or near IR overtone excitation of the OH stretching modes or electronic excitation of the O-O peroxy moiety in the acid-bound radical. This new overtone or electronic excitation-based photomechanism for the peroxy radical decomposition may provide useful insight into the missing photolytic source of the HOx at high solar zenith angles corresponding to the dawn or dusk photochemistry.

Bio fuel production from crude Jatropha oil; addition effect of formic acid as an in-situ hydrogen source

The catalytic deoxygenation reaction of crude Jatropha oil (CJO) was carried out to produce oxy-free hydrocarbons in assistance with hydrogen in-situ produced from formic acid solution (30%) and addition effect of formic acid was discussed on the deoxygenation reaction and product distribution. Mixing of formic acid with reactant yielded higher oil conversion and higher selectivity to normal hydrocarbon (mainly C15 and C17) than those of the other cases (no mixing or water addition). Total surface area and total pore volume of used catalysts in the batch reactor followed the order Pd/C–formic acid solution>Pd/C–water>Pd/C–no co-reactant under constant conditions. Moreover, significantly higher degree of deoxygenation with a high initial resistance to catalyst deactivation was observed on Pd/C catalyst in the presence of formic acid during the continuous catalytic reaction. This means that addition of formic acid solution as the hydrogen donor is favorable the deoxygenation reaction and the initial deactivation of catalyst. As results of continuous deoxygenation reaction using the mixture of oil and formic acid, normal hydrocarbon in the liquid product was main product, about 97%, and the degree of deoxygenation was about 99.5%.