High Formic Acid Research Articles

Heteropolyanion-based ionic liquids catalysed conversion of cellulose into formic acid without any additives

Heteropolyanion-based ionic liquids with –SO3H functionalized cations and PMo11VO404− anions were synthesized and applied in the conversion of cellulose into formic acid (FA). It was demonstrated that the as-prepared ILs showed enhanced activity for catalysing cellulose conversion to FA in the presence of oxygen in water compared to H4PMo11VO40. A high FA yield over 50% accompanied by a FA concentration of ∼10% in reaction solution was obtained at 180 °C and in an oxygen pressure of 1.0 MPa. The possible pathway of FA production from cellulose was investigated. It was indicated that the resulting ILs served as bifunctional catalysts with cations catalysing the cellulose hydrolysis to glucose and anions catalysing glucose oxidation to FA. These ILs may find more applications in cellulose conversion.

Liquid–Vapor Interface of Formic Acid Solutions in Salt Water: A Comparison of Macroscopic Surface Tension and Microscopic in Situ X-ray Photoelectron Spectroscopy Measurements

The liquid–vapor interface is difficult to access experimentally but is of interest from a theoretical and applied point of view and has particular importance in atmospheric aerosol chemistry. Here we examine the liquid–vapor interface for mixtures of water, sodium chloride, and formic acid, an abundant chemical in the atmosphere. We compare the results of surface tension and X-ray photoelectron spectroscopy (XPS) measurements over a wide range of formic acid concentrations. Surface tension measurements provide a macroscopic characterization of solutions ranging from 0 to 3 M sodium chloride and from 0 to over 0.5 mole fraction formic acid. Sodium chloride was found to be a weak salting out agent for formic acid with surface excess depending only slightly on salt concentration. In situ XPS provides a complementary molecular level description about the liquid–vapor interface. XPS measurements over an experimental probe depth of 51 Å gave the C 1s to O 1s ratio for both total oxygen and oxygen from water. XPS also provides detailed electronic structure information that is inaccessible by surface tension. Density functional theory calculations were performed to understand the observed shift in C 1s binding energies to lower values with increasing formic acid concentration. Part of the experimental −0.2 eV shift can be assigned to the solution composition changing from predominantly monomers of formic acid to a combination of monomers and dimers; however, the lack of an appropriate reference to calibrate the absolute BE scale at high formic acid mole fraction complicates the interpretation. Our data are consistent with surface tension measurements yielding a significantly more surface sensitive measurement than XPS due to the relatively weak propensity of formic acid for the interface. A simple model allowed us to replicate the XPS results under the assumption that the surface excess was contained in the top four angstroms of solution.

A study on the photosynthesis of formic acid using iron-doped titanium dioxide

Formic acid has attracted much interest owing to potential use in the direct formic acid fuel cells. Photosynthesised formic can be used as a hydrogen carrier because it is liquid at standard temperature and pressure. It is much safer and easier for handling and storing than hydrogen. It can be directly fed to the fuel cell and does not need to be reformed. In this paper, formic acid was artificially photosynthesised in a photocatalytical reactor by using iron ion-doped TiO2. Water was used as a hydrogen source. CO2 was introduced by using continuous bubbling. Highest formic acid yield was obtained at 600 W visible light irradiation by using a 3 g L−1 photocatalyst load and a 5 L min−1 CO2 gas flow rate at continuous stirring. The resultant acid was characterised by using UV–visible absorbance spectrophotometer.

No catalyst addition and highly efficient dissociation of H2O for the reduction of CO2 to formic acid with Mn.

The "greenhouse effect" caused by the increasing atmospheric CO2 level is becoming extremely serious, and thus, the reduction of CO2 emissions has become an extensive, urgent, and long-term task. The dissociation of water for CO2 reduction with solar energy is regarded as one of the most promising methods for the sustainable development of the environment and energy. However, a high solar-to-fuel efficiency keeps a great challenge. In this work, the first observation of a highly effective, highly selective, and robust system of dissociating water for the reduction of carbon dioxide (CO2) into formic acid with metallic manganese (Mn) is reported. A considerably high formic acid yield of more than 75% on a carbon basis from NaHCO3 was achieved with 98% selectivity in the presence of simple commercially available Mn powder without the addition of any catalyst, and the proposed process is exothermic. Thus, this study may provide a promising method for the highly efficient dissociation of water for CO2 reduction by combining solar-driven thermochemistry with the reduction of MnO into Mn.

Metabolites in the milk of buffalo, Holstein cross, indigenous and Red Chittagong cattle of Bangladesh

Low molecular weight chemical compounds or intermediate products of a metabolism or other cellular processes are called metabolites. The objective of the present study was to investigate the variations in the metabolite concentration in the milk from crossbred water Buffalo (B), Holstein cross (H), Indigenous cattle (I) and Red Chittagong Cattle (R) and the relationships among those metabolites. The concentration of citric acid, ? -keto glutaric acid (?-keto GA), orotic acid, pyruvic acid, succinic acid, lactic acid, formic acid, uric acid and propionic acid were measured by using High Performance Liquid Chromatography. Pooled milk samples of nine B, fifteen I and twenty R cows were collected from the research farm of Bangladesh Livestock Research Institute, Savar, Dhaka, Bangladesh. The pooled milk samples of H were collected from twenty five cows of Central Cattle Breeding Station and Dairy Farm, Savar, Dhaka, Bangladesh. All the sampling was done from the morning milking. The samples were preserved by adding ‘bronopol tablet’ and frozen and stored at -20 °C. Except propionic acid, all the metabolites varied significantly (p<0.01) among the milk types and B milk had lowest concentration of them. The highest concentration of citric acid (ppm) was 2245.50±39.90 in I milk followed by 2156.60±26.60 in R, 1858.30±8.70 in H and 1366.70±33.70 in B milk. The H, I and R milk were found similar in their ?-keto GA content. Similarities were also found for succinic acid between H and R milk and so for H and I milk in uric acid content. Highest formic acid was found in H milk (392.78±2.23 ppm) and the lowest was 308.91±3.75 ppm in R milk while B and I milk was found similar. The lowest concentration of uric acid was found 0.44±0.26 ppm in B milk and R milk had the highest content (11.38±1.10 ppm). Pyruvic, formic and propionic acids showed no significant relationship among them and with others as well. The most highly significant (p<0.01) correlation was found between orotic and ?-keto GA (r=0.915) and between uric and succinic acid (r=0.914). So, the metabolites showed a considerable variation in their concentration in different types of milk and also some of the parameters showed significant relationship among them. DOI: http://dx.doi.org/10.3329/bjas.v42i2.18504 Bang. J. Anim. Sci. 2013. 42 (2): 152-157

Artificial Photosynthesis of Formic Acid Using Iron Doped TiO<sub>2</sub>

Formic acid has attracted much of interest due to potential using in Direct-formic acid fuel cells. Photosynthesized formic can be used as the hydrogen carrier because it is liquid at standard temperature and pressure. It is much safer and easier for handling and storing than hydrogen. It can be directly fed to the fuel cell and not need to be reformed. In this paper formic acid was artificially photosynthesized in photocatalytical reactor using Iron ion doped TiO2. Water was used as a hydrogen source. CO2 was introduced using continuous bubbling. Highest formic acid yield was obtained at 600W visible light irradiation using 3g/L photocatalyst load and 5L/min CO2 gas flow rate at continuous stirring. Resulted acid was characterized using UV-visible absorbance spectrophotometer and gas chromatography (GC).

Trichloroethylene Hydrodechlorination in Water Using Formic Acid as Hydrogen Source: Selection of Catalyst and Operation Conditions

This work studies the aqueous‐phase hydrodechlorination of trichloroethylene (TCE), using formic acid (FA) as hydrogen source, over different Pd‐based catalysts. Reactions have been performed in a batch reactor at mild conditions (300–340 K), using different FA/TCE ratios (from 10 to 450) and working with TCE concentrations close to saturation (1000 ppm). Different supports have been tested for Pd‐based catalysts: activated carbon (AC), carbon nanofibers (CNF), high surface area graphites (HSAG), alumina and ZSM‐5 zeolite, following their activity the order: 0.5%Pd/CNF > 0.5%Pd/HSAG> 0.5%Pd/Al2O3 > 0.5%Pd/ZSM‐5 > 0.5%Pd/AC. This alternative hydrogen source is confirmed to be technically feasible for TCE, determining an optimum FA/TCE ratio of 35. Thus, high FA concentrations inhibit the reaction due to competitive adsorption of both reactants. Furthermore, the support must be carefully selected, since supports presenting very strong interactions with the TCE (such as the ACs) hinder the hydrodechlorination. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 1217–1222, 2013

Enhanced photocatalytic reduction of aqueous Pb(II) over Ag loaded TiO2 with formic acid as hole scavenger

In the present study, photocatalytic Pb(II) reduction over TiO2 and Ag/TiO2 catalysts in the presence of formic acid was explored to eliminate Pb(II) pollution in water. Ag/TiO2 catalysts were prepared by the photo-deposition method and characterized using UV-Vis diffuse reflectance spectra, X-ray reflection diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Ag deposition on TiO2 led to enhanced photocatalytic Pb(II) reduction and the Ag/TiO2 catalyst with a Ag loading amount of 0.99 wt.% exhibited the optimum photocatalytic activity. For Pb(II) reduction over Ag/TiO2 with a Ag loading amount of 0.99 wt.%, initial Pb(II) reduction rate was found to be dependent on the initial concentrations of formic acid and Pb(II). Increasing initial Pb(II) concentration led to linearly increased initial Pb(II) reduction rate. At low formic acid concentration, in parallel, initial Pb(II) reduction rates increased with formic concentration, but remained nearly identical at high formic acid concentration. Solution pH impacted the photocatalytic Pb(II) reduction and after irradiation for 100 min Pb(II) was removed by 11.8%, 91.2% and 98.6% at pH of 0.8, 2.0 and 3.5, respectively, indicative of enhanced Pb(II) reduction with pH in the tested pH range. The results showed that Ag/TiO2 displayed superior catalytic activity to TiO2, highlighting the potential of using Ag/TiO2 as a more effective catalyst for photocatalytic Pb(II) reduction.

Towards the development of a hydrogen battery

A novel Ru-catalyzed hydrogenation of carbon dioxide proceeds with an unprecedented high formic acid to amine ratio (AAR of 2.69), which results in an improved energy content. The presented catalyst system allows for reversible fast hydrogen loading (even at RT) and unprecedented unloading (TON for H2 liberation of 800000).

Formic Acid Tolerant Ir-Based Electrocatalysts for Oxygen Reduction Reaction

In this paper, carbon-supported Ir-Co, Ir-Ni, and Ir-Cr catalysts (Ir-Co/C, Ir-Ni/C, and Ir-Cr/C) were synthesized and characterized for the oxygen reduction reaction (ORR). Compared to both Pt/C and Pd/C catalysts, these Ir alloy catalysts demonstrated much higher formic acid tolerance capabilities during the ORR process in a 0.5 M H2SO4 solution containing both oxygen and formic acid. Rotating disk electrode measurements confirmed that if formic acid was present, these Ir alloy catalysts could still catalyze a complete 4-electron transfer ORR from O2 to H2O, while the Pt/C catalyst could only catalyze a reaction contributed by both 2- and 4-electron transfer processes, producing both H2O2 and H2O. These results strongly suggest that Ir alloy catalysts should be promising candidates for direct formic acid fuel cell applications.

Efficient fermentation of xylose to ethanol at high formic acid concentrations by metabolically engineered Saccharomyces cerevisiae

Recombinant yeast strains highly tolerant to formic acid during xylose fermentation were constructed. Microarray analysis of xylose-fermenting Saccharomyces cerevisiae strain overexpressing endogenous xylulokinase in addition to xylose reductase and xylitol dehydrogenase from Pichia stipitis revealed that upregulation of formate dehydrogenase genes (FDH1 and FDH2) was one of the most prominent transcriptional events against excess formic acid. The quantification of formic acid in medium indicated that the innate activity of FDH was too weak to detoxify formic acid. To reinforce the capability for formic acid breakdown, the FDH1 gene was additionally overexpressed in the xylose-metabolizing recombinant yeast. This modification allowed the yeast to rapidly decompose excess formic acid. The yield and final ethanol concentration in the presence of 20 mM formic acid is as essentially same as that of control. The fermentation profile also indicated that the production of xylitol and glycerol, major by-products in xylose fermentation, was not affected by the upregulation of FDH activity.

10.2478/s11814-009-0173-z

Palladium particles supported on porous carbon of 20 and 50 nm pore diameters were prepared and applied to the direct formic acid fuel cell (DFAFC). Four different anode catalysts with Pd loading of 30 and 50 wt% were synthesized by using impregnation method and the cell performance was investigated with changing experimental variables such as anode catalyst loading, formic acid concentration, operating temperature and oxidation gas. The BET surface areas of 20 nm, 30 wt% and 20 nm, 50 wt% Pd/porous carbon anode catalysts were 135 and 90 m2/g, respectively. The electro-oxidation of formic acid was examined in terms of cell power density. Based on the same amount of palladium loading with 1.2 or 2 mg/cm2, the porous carbon-supported palladium catalysts showed higher cell performance than unsupported palladium catalysts. The 20 nm, 50 wt% Pd/porous carbon anode catalyst generated the highest maximum power density of 75.8 mW/cm2 at 25 °C. Also, the Pd/porous carbon anode catalyst showed less deactivation at the high formic acid concentrations. When the formic acid concentration was increased from 3 to 9 M, the maximum power density was decreased from 75.8 to 40.7 mW/cm2 at 25 °C. Due to the high activity of Pd/porous carbon catalyst, the cell operating temperature has less effect on DFAFC performance.

Gold supported catalytic layer: An intermediate step between fundamental and applied fuel cell studies

We report the preparation and electrochemical characterization of gold supported catalytic layer electrodes which have been prepared using a similar methodology to that employed in the preparation of conventional catalyst coated membranes. Consequently, the so-prepared catalytic layers have comparable properties (morphology and thickness) than those employed in direct liquid fuel cells. Using this working electrode configuration, and the so-called hydrogen adsorption–desorption region, fundamental electrochemical parameters such as electrochemically accessible Pt surface area, roughness factor and Pt-catalyst utilization of the catalytic layer have been evaluated. The electrochemically accessible Pt surface area, roughness factor and Pt-catalyst utilization have been found independent of the metal loading in the range of 0.1–0.5 mg Pt cm −2. However for 1 mg Pt cm −2, an important decrease on electrochemically accessible Pt surface area and Pt-catalyst utilization has been observed. On the other hand, when formic acid electrooxidation is used, a sudden decrease on the electrocatalytic activity has been observed as metal loading increases. These results clearly indicate that the formic acid electrooxidation process is strongly dependant of the accessibility of the reactant into the inner part of the electrodes, highlighting its mass-transport controlled reaction properties. These findings point out that, from an applied point of view, it is recommendable using catalytic layers as thinner as possible as well as high formic acid concentrations. These experimental conditions will maximize the Pt-catalyst utilization by minimizing the accessibility problems of the reactant into the inner part of the electrodes.

Performance characterization of direct formic acid fuel cell using porous carbon-supported palladium anode catalysts

Palladium particles supported on porous carbon of 20 and 50 nm pore diameters were prepared and applied to the direct formic acid fuel cell (DFAFC). Four different anode catalysts with Pd loading of 30 and 50 wt% were synthesized by using impregnation method and the cell performance was investigated with changing experimental variables such as anode catalyst loading, formic acid concentration, operating temperature and oxidation gas. The BET surface areas of 20 nm, 30 wt% and 20 nm, 50 wt% Pd/porous carbon anode catalysts were 135 and 90 m2/g, respectively. The electro-oxidation of formic acid was examined in terms of cell power density. Based on the same amount of palladium loading with 1.2 or 2 mg/cm2, the porous carbon-supported palladium catalysts showed higher cell performance than unsupported palladium catalysts. The 20 nm, 50 wt% Pd/porous carbon anode catalyst generated the highest maximum power density of 75.8 mW/cm2 at 25 °C. Also, the Pd/porous carbon anode catalyst showed less deactivation at the high formic acid concentrations. When the formic acid concentration was increased from 3 to 9 M, the maximum power density was decreased from 75.8 to 40.7 mW/cm2 at 25 °C. Due to the high activity of Pd/porous carbon catalyst, the cell operating temperature has less effect on DFAFC performance.

Suppression of growth rate of colony-associated fungi by high fructose corn syrup feeding supplement, formic acid, and oxalic acid.

Suppression of growth rate of colony-associated fungi by high fructose corn syrup feeding supplement, formic acid, and oxalic acid.

Suppression of growth rate of colony-associated fungi by high fructose corn syrup feeding supplement, formic acid, and oxalic acid

SummarySelect colony-associated fungi (bee isolates), Absidia sp., Ascosphaera apis, Aspergillus flavus, Fusarium sp., Penicillium glabrum, Mucor sp., showed a 40% reduction in radial growth rate with formic acid, a 28% reduction with oxalic acid, and a 15% reduction with fructose and high fructose corn syrup (HFCS) when grown on supplemented media at 30°C to mimic colony conditions. No effect, suppressing or promoting growth, was observed on other colony-associated fungi, Alternaria sp., Aspergillus niger, Cladosporium cladosporioides, Rhizopus sp. and Trichoderma sp., except 0.1M formic and oxalic acid. Sensitivity to these compounds did not correlate with the fungus species being a slow- or fast-grower and sensitivity to one compound did not translate to sensitivity to another compound. Given the competitive nature and high-sporing (conidia) activity of these species, our results suggest that alteration or disruption of the colony mycoflora can occur by use of these compounds. This may indicate a possible link between compound application and incidence of bee fungal pathogens.

Study of carbon-supported Au catalyst as the cathodic catalyst in a direct formic acid fuel cell prepared using a polyvinyl alcohol protection method

In this paper, it is reported for the first time that a carbon-supported Au (Au/C) catalyst for the cathodic catalyst in a direct formic acid fuel cell (DFAFC) was prepared using a polyvinyl alcohol (PVA) protection method. The results indicated that for oxygen reduction, the electrocatalytic activity of the Au/C catalyst prepared with the PVA protection method is much better than that of a Au/C catalyst prepared with the pre-precipitation method. This is due to the small average size and low relative crystallinity of the Au particles in the Au/C catalyst prepared by the PVA protection method, compared to that of the Au/C catalyst prepared by the pre-precipitation method, illustrating that the average size and the relative crystallinity of the Au particles has an effect on the electrocatalytic activity of the Au/C catalyst for oxygen reduction. In addition, because Au has no electrocatalytic activity for the oxidation of formic acid, the Au/C catalyst possesses a high formic acid tolerance. After the electrocatalytic activity of the Au/C catalyst for the oxygen reduction is improved, it is suitable to be used as the cathodic catalyst in DFAFC.

Performance characterization of Pd/C nanocatalyst for direct formic acid fuel cells

Previous work has demonstrated that unsupported Pd (Pd black) based direct formic acid fuel cells (DFAFCs) show unusually high power density at the ambient temperature. In this paper finely dispersed Pd particles have been deposited on carbon supports (Vulcan XC-72 ®). In particular, both 20 and 40 wt.% Pd on carbon supports (Pd/C) nanocatalysts have been synthesized and their performances, as an anode catalyst for DFAFC, with different formic acid feed concentrations at a moderate temperature have been evaluated. The 20 and 40 wt.% Pd/C based DFAFCs, with dry air and zero backpressure, can generate a maximum power density of 145 and 172 mW cm −2 at 30 °C, respectively. Their open cell potentials are 0.90 V. In comparison to the unsupported Pd, we found that the 20 wt.% Pd/C in the DFAFC shows a lower total current, but a higher current per gram of precious metal than the Pd black catalyst. The supported catalysts also show less deactivation at the high formic acid concentrations.

The oxidation of formic acid to carbonate at Cu(110) surfaces

The reaction of formic acid with pre-oxidised Cu(110) surfaces is re-evaluated on the basis of new temperature programmed desorption and X-ray photoelectron spectroscopy results. It is shown that at high oxygen coverages and for high formic acid exposures, or after co-adsorption of formic acid and dioxygen, a surface carbonate is formed. The carbonate appears to be very similar to that formed by the oxidation of CO 2, at higher pressures, which was reported in an earlier paper. The results also account for a number of unexplained observations on this system and provide further support for the involvement of carbonate in methanol synthesis on copper.

Thermodynamic Data for Complex Formation Between Cucurbituril and Alkali and Alkaline Earth Cations in Aqueous Formic Acid Solution

Complex formation, between alkali and alkaline earth cations and the macrocyclic ligands cucurbituril and 18-crown-6, was studied by calorimetric titration in aqueous formic acid solution (50 vol.%). The solubility of cucurbituril strongly depends on the concentration of formic acid. At low and very high formic acid concentrations, the solubility of cucurbituril is low. For both ligands the formation of proton complexes influence the complexation reactions with cations. Thus, the complex formation in most cases is favored by entropic contributions. Only in the case of the Ba2+ ion stability constants and reaction enthalpies could be measured at lower formic acid concentrations. Using a highly sensitive calorimeter, the stability constants and reaction enthalpies for the reaction of Na+ and Ba2+ with cucurbituril in aqueous solution could be determined.