Formate Salts Research Articles

Research Requirements to Move the Bar forward Using Aqueous Formate Salts as H2 Carriers for Energy Storage Applications

In this perspective on hydrogen carriers, we focus on the needs for the development of robust active catalysts for the release of H2 from aqueous formate solutions, which are non-flammable, non-toxic, thermally stable, and readily available at large scales at reasonable cost. Formate salts can be stockpiled in the solid state or dissolved in water for long term storage and transport using existing infrastructure. Furthermore, formate salts are readily regenerated at moderate pressures using the same catalyst as for the H2 release. There have been several studies focused on increasing the activity of catalysts to release H2 at moderate temperatures, i.e., < 80 °C, below the operating temperature of a proton exchange membrane (PEM) fuel cell. One significant challenge to enable the use of aqueous formate salts as hydrogen carriers is the deactivation of the catalyst under operating conditions. In this work we provide a review of the most efficient heterogeneous catalysts that have been described in the literature, their proposed modes of deactivation, and the strategies reported to reactivate them. We discuss potential pathways that may lead to deactivation and strategies to mitigate it in a variety of H2 carrier applications. We also provide an example of a potential use case employing formate salts solutions using a fixed bed reactor for seasonal storage of energy for a microgrid application.

Evaluation of Co/SSZ-13 Zeolite Catalysts Prepared by Solid-Phase Reaction for NO-SCR by Methane.

Co/SSZ‐13 zeolites were prepared by heating the finely dispersed mixture of NH4‐SSZ‐13 and different cobalt salts up to 550 °C. Investigations by thermogravimetry – differential scanning calorimetry – mass spectrometry provided new insight into details of the solid‐state reaction. Formation of Co carrying hydrate melt or volatile species was shown to proceed from chloride, nitrate, or acetylacetonate Co precursor salts upon thermal treatment. This phase change allows the transport of the Co species into the zeolite pores. The reaction of the NH4 + or H+ zeolite cations and the mobile Co precursors generates vapor or gas products, readily leaving the zeolite pores, and cobalt ions in lattice positions suggesting that solid‐state ion‐exchange is the prevailing process. The obtained catalysts are of good activity and N2 selectivity in the CH4/NO‐SCR reaction. The thermal treatment of acetate or formate salts give solid intermediates that are unable to get in contact and react with the cations in the zeolite micropores. These catalysts contain mainly Co‐oxide clusters located on the outer surface of the zeolite crystallites and have poor catalytic performance.

Scalable Total Syntheses and Structure-Activity Relationships of Haouamines A, B, and Their Derivatives as Stable Formate Salts.

Haouamines A, B, and their derivatives were synthesized via Suzuki-Miyaura coupling and three key cyclization reactions as follows: the newly developed palladium(0)-catalyzed arylative cyclization of phenylalanine-derived alkyne-aldehydes with 2-bromoarylboronic acid (an "anti-Wacker"-type cyclization); BF3 ⋅OEt2 -promoted Friedel-Crafts-type cyclization of symmetrical electron-rich aromatic rings adjacent to a tertiary allylic alcohol leading to the indeno-tetrahydropyridine skeleton; and (cyanomethyl)trimethylphosphonium iodide-mediated macrocyclization of amino alcohols to afford aza-paracyclophane precursors. The palladium-catalyzed reduction of mono- and di-triflate intermediates in the later stages enabled the alteration of both the position and number of hydroxyl groups on the C-ring. The instability of haouamine B was dramatically improved by salt formation with formic acid. An unambiguous evaluation of the cytotoxicity of the prepared haouamine derivative formates with and without hydroxyl groups at different positions on the C-ring indicated that the catechol structure in haouamine B produced weak cytotoxicity.

A sustainable valorization of neopentyl glycol salt waste containing sodium formate via bipolar membrane electrodialysis

Neopentyl glycol (NPG) is an important organic compound that has numerous applications. The standard preparation route via the formate sodium method is cramped by the generation of a large amount salt waste and the high consumption of acid, base and water. In this study, a sustainable valorization of NPG waste salt was developed using bipolar membrane electrodialysis (BMED). This technique allowed the direct conversion of NPG waste salt into high value formic acid and soda, which could be used as raw feeds for upstream hydrogenation and neutralization processes. To verify the feasibility of BMED for neopentyl glycol production, effects of current density and feed salt concentration on the separation performance were investigated. The conversion rates of formate salt were almost 100% for all the experiments. Current efficiency decreased with an increase in current density and the energy consumption increased with an increase in current density. A lowest energy consumption of 6.08 kWh·kg−1 was obtained at the current density of 100 A·m−2. The BMED performances were enhanced when the feed salt concentration increased from 0.1 mol·L−1 to 0.4 mol·L−1, but the performance decreased when the feed concentration further increased to 0.5 mol·L−1. The total process cost of BMED process was estimated at $1.304·kg−1 HCOOH under the optimal experimental condition. By considering the benefit of recycled formic acid and soda, the total running cost was about -$115.5 for produce 1 tons of NPG. The revenue of recycled chemicals was greater than the total process cost of the BMED process. Naturally, BMED is a sustainable, cost-effective, environment friendly technology for the valorization of NPG salt waste.

Experimental performance and energy efficiency investigation of composite superabsorbent polymer and potassium formate coated heat exchangers

The poor efficiency of vapor compression chillers emerges due to the simultaneous treatment of sensible and latent cooling loads. By employing desiccant coated heat exchangers (DCHEs) for removing latent loads, the energy efficiency is enhanced as the conventional cooling coil is used for high-temperature sensible cooling. Currently, DCHEs have limitations due to low sorption capacity, high regeneration temperature, short operating time, corrosion, and deliquescence of the desiccating material. To address these research gaps, we synthesized a composite polymer desiccant by combining a superabsorbent polymer and less corrosive potassium formate salt. Desiccant characterization experiments showed that the new desiccant exhibited 4–8 times gain in sorption capacity when compared to pure/composite silica gel. The dynamic performance studies showed that the cycle time could be extended up to 15 min and 40–50 °C was sufficient for regeneration in contrast to the previous constraint of 5 min and 60–80 °C, respectively. Further, the new composite desiccant removed 3 times higher cooling load than silica gel based DCHEs and recorded 2 times higher thermal efficiency. When integrated with conventional air-conditioners, DCHE could trim up to 50% of the electrical power, and short payback periods of less than 2 years were obtained.

Efficacy of sodium formate as a technological feed additive (preservative) for all animal species.

In 2015, the EFSA Panelon Additives and Products or Substances used in Animal Feed (FEEDAP) issued an opinion on the safety and efficacy of ammonium, calcium and sodium formate when used as a technological additive (preservative) for all animal species. Sodium formate was considered safe for all animal species at a maximum concentration of 10,000mg formic acid equivalents/kg complete feed (with the exception of pigs, for which a maximum concentration of 12,000mg formic acid equivalents/kg complete feed was considered safe). Sodium formate was also considered safe for the consumer and the environment. The Panelalso concluded that sodium formate is non-irritant to the skin, but mildly irritant to the eyes, and is a respiratory irritant with a potential for sensitisation. The Panelalso concluded that 'Sodium formate or solid sodium formate had no discernible effects on microbial numbers in the feed materials examined. The preservative effect of the three formate salts in water for drinking was not demonstrated'. In the current opinion, additional data to demonstrate the efficacy of sodium formate as a preservative in feed for all animal species were assessed. The Panelconcluded that sodium formate has the potential to be efficacious as a preservative in feedingstuffs for all animal species at the proposed use level. In the absence of data, the Panelcannot conclude on the efficacy of the use of the additive in water for drinking.

Efficacy of calcium formate as a technological feed additive (preservative) for all animal species.

In 2015, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) issued an opinion on the safety and efficacy of ammonium formate, calcium formate and sodium formate when used as a technological additive (preservative) for all animal species. Calcium formate was considered safe for all animal species at a maximum concentration of 10,000 mg formic acid equivalents/kg complete feed (with the exception of pigs, for which a maximum concentration of 12,000 mg formic acid equivalents/kg complete feed was considered safe). Calcium formate was also considered safe for the consumer and the environment. The Panel also concluded that calcium formate is non‐irritant to the skin, but mildly irritant to the eyes, and is a respiratory irritant with a potential for sensitisation. The Panel also concluded that ‘Calcium formate or solid sodium formate had no discernible effects on microbial numbers in the feed materials examined. The preservative effect of the three formate salts in water for drinking was not demonstrated’. In the current opinion, additional data to demonstrate the efficacy of calcium formate as a preservative in feed for all animal species were assessed. The Panel concluded that calcium formate has the potential to be efficacious as a preservative in feedingstuffs for all animal species at the proposed use level. In the absence of data, the Panel cannot conclude on the efficacy of the use of the additive in water for drinking.

Sodium-induced solid-phase hydrogenation of carbon dioxide to formate by mechanochemistry

Transforming carbon dioxide (CO2) into value-added fuels is an innovative way to address both the energy and the climate issues. In particular, formic acid, as formate salt, is recently attracting attention because this acid can be used as a chemical fuel in fuel cells. Here we present a novel method for hydrogenating CO2-containing industrially relevant salts, such as sodium bicarbonate ammonium bicarbonate and ammonium carbonate, to formate. Metal sodium (Na0) was used as the reducing agent to break the C–O bond and as a inducer of hydrogen transfer. A ball-milling mechanochemical method was used for the solid-phase reaction. Results show that reducing (NH4)2CO3(s) with sodium yielded 41.4% formate after 7 h under catalyst-free conditions. Our new method has thus promising potential applications in the emerging CO2 economy.

Hydroxide Based Integrated CO2 Capture from Air and Conversion to Methanol.

The first example of an alkali hydroxide-based system for CO2 capture and conversion to methanol has been established. Bicarbonate and formate salts were hydrogenated to methanol with high yields in a solution of ethylene glycol. In an integrated one-pot system, CO2 was efficiently captured by an ethylene glycol solution of the base and subsequently hydrogenated to CH3OH at relatively mild temperatures (100-140 °C) using Ru-PNP catalysts. The produced methanol can be easily separated by distillation. Hydroxide base regeneration at low temperatures was observed for the first time. Finally, CO2 capture from ambient air and hydrogenation to CH3OH was demonstrated. We postulate that the high capture efficiency and stability of hydroxide bases make them superior to existing amine-based routes for direct air capture and conversion to methanol in a scalable process.

Transfer hydrogenation of carbon dioxide via bicarbonate promoted by bifunctional C-N chelating Cp*Ir complexes.

Metal-ligand cooperative Cp*Ir(iii) complexes derived from primary benzylic amines effectively promote transfer hydrogenation of atmospheric CO2 using 2-propanol at 80 °C. Isotope-labelling experiments strengthen that active Ir species can preferentially reduce bicarbonate congeners formed from CO2. The powerful transfer hydrogenation catalyst exhibits remarkable activity for the conversion of bicarbonates into formate salts with a turnover number up to 3200, even without H2 and CO2.

A highly active copper catalyst for the hydrogenation of carbon dioxide to formate under ambient conditions.

Carbon dioxide (CO2) is an important reactant and can be used for the syntheses of various types of industrially important chemicals. Hence, investigation concerning the conversion of CO2 into valuable energy-rich chemicals is an important and current topic in molecular catalysis. Recent research on molecular catalysts has led to improved rates for conversion of CO2 to energy-rich products such as formate, but the catalysts based on first-row transition metals are underdeveloped. Copper(i) complexes containing the 1,1'-bis(di-tert-butylphosphino) ferrocene ligand were found to promote the catalytic hydrogenation of CO2 to formate in the presence of DBU as the base, where the catalytic conversion of CO2via hydrogenation is achieved using in situ gaseous H2 (granulated tin metal and concentrated HCl) to produce valuable energy-rich chemicals, and therefore it is a promising, safe and simple strategy to conduct reactions under ambient pressure at room temperature. Towards this goal, we report an efficient copper(i) complex based catalyst [CuI(dtbpf)] to achieve ambient-pressure CO2 hydrogenation catalysis for generating the formate salt (HCO2-) with turnover number (TON) values of 326 to 1.065 × 105 in 12 to 48 h of reaction at 25 °C to 80 °C. The outstanding catalytic performance of [CuI(dtbpf)] makes it a potential candidate for realizing the large-scale production of formate by CO2 hydrogenation.

The thermo physical, HOMO, LUMO, Vibrational spectroscopy and QSAR study of morphonium formate and acetate Ionic Liquid Salts using computational method

Morphine is considered as the uncountable pain killer drug which is taken by both of mouth or injection. In this case, morpholinium ILs is the most applicable molecules due to liquid range so that the thermo-chemical, chemical reactivity and biological interaction of most expected morphonium formate and acetate ILs is considered under theoretical study by HyperChem 8.010 computer programming method. Some thermodynamic parameters such as free energy, entropy, dipole moment, binding energy, nuclear energy, electronics energy, heat of formation and QSAR properties of molecules like charge density, surface area grid, volume, LogP, polarizability, refractivity, molecular mass, and reactivity properties of molecule like HOMO, LUMO, HOMO-LUMO, ionization potential and electron affinity were determined using the HyperChem 8.0.10 programme. The morphonium formate is less biological active than morphonium acetate because LogP is 1.19 and -0.66 respectively. On the other hand, the HOMO LUMO gap in all transition level almost same that indicate similar chemical reactivity. The binding energy of both molecules is -3078.01 and -3351.25 kcal/mol respectively. The vibrational spectroscopy data provides them the identification and characterization.

Catalytic CO2 Reduction with Boron- and Aluminum Hydrides.

The previously reported dimeric NHI aluminum dihydrides 1 a,b, as well as the bis(NHI) aluminum dihydride salt 9 +[OTs]−, the bis(NHI) boron dihydride salt 10 +[OTs]−, and the “free” bis(NHI) ligand 12 were investigated with regard to their activity as a homogenous (pre)catalyst in the hydroboration (i. e. catalytic reduction) of carbon dioxide (CO2) in chloroform under mild conditions (i. e. room temperature, 1 atm; NHI=N‐heterocyclic imine, Ts=tosyl). Borane dimethylsulfide complex and catecholborane were used as a hydride source. Surprisingly, the less sterically hindered 1 a exhibited lower catalytic activity than the bulkier 1 b. A similarly unexpected discrepancy was found with the lower catalytic activity of 10 + in comparison to the one of the bis(NHI) 12. The latter is incorporated as the ligand to the boron center in 10 +. To elucidate possible mechanisms for CO2 reduction the compounds were subjected to stoichiometric reactivity studies with the borane or CO2. Aluminum carboxylates 4, 6, and 7 + with two, four, and one formate group per two aluminum centers were isolated. Also, the boron formate salt 11 +[OTs]− was characterized. Selected metal formates were subjected to stoichiometric reactions with boranes and/or tested as a catalyst. We conclude that each type of catalyst (1 a,b, 9 +, 10 +, 12) follows an individual mechanistic pathway for CO2 reduction.

Integrated CO2 Capture and Conversion to Formate and Methanol: Connecting Two Threads.

The capture of CO2 from concentrated emission sources as well as from air represents a process of paramount importance in view of the increasing CO2 concentration in the atmosphere and its associated negative consequences on the biosphere. Once captured using various technologies, CO2 is desorbed and compressed for either storage (carbon capture and storage (CCS)) or production of value-added products (carbon capture and utilization (CCU)). Among various products that can be synthesized from CO2, methanol and formic acid are of high interest because they can be used directly as fuels or to generate H2 on demand at low temperatures (<100 °C), making them attractive hydrogen carriers (12.6 and 4.4 wt % H2 in methanol and formic acid, respectively). Methanol is already produced in huge quantities worldwide (100 billion liters annually) and is also a raw material for many chemicals and products, including formaldehyde, dimethyl ether, light olefins, and gasoline. The production of methanol through chemical recycling of captured CO2 is at the heart of the so-called "methanol economy" that we have proposed with the late Prof. George Olah at our Institute. Recently, there has been significant progress in the low-temperature synthesis of formic acid (or formate salts) and methanol from CO2 and H2 using homogeneous catalysts. Importantly, several studies have combined CO2 capture and hydrogenation, where captured CO2 (including from air) was directly utilized to produce formate and CH3OH without requiring energy intensive desorption and compression steps. This Account centers on that topic. A key feature in the combined CO2 capture and conversion studies reported to date for the synthesis of formic acid and methanol is the use of an amine or alkali-metal hydroxide base for capturing CO2, which can assist the homogeneous catalysts in the hydrogenation step. We start this Account by examining the combined processes where CO2 is captured in amine solutions and converted to alkylammonium formate salts. The effect of amine basicity on the reaction rate is discussed along with catalyst recycling schemes. Next, methanol synthesis by this combined process, with amines as capturing agents, is explored. We also examine the system developments for effective catalyst and amine recycling in this process. We next go through the effect of catalyst molecular structure on methanol production while elucidating the main deactivating pathway involving carbonylation of the metal center. The recent advances in first-row transition metal catalysts for this process are also mentioned. Subsequently, we discuss the capture of CO2 using hydroxide bases and conversion to formate salts. The regeneration of the hydroxide base (NaOH or KOH) at low temperatures (80 °C) in cation-conducting direct formate fuel cells is presented. Finally, we review the challenges in the yet unreported integrated CO2 capture by hydroxide bases and conversion to methanol process.

Formate-Catalyzed Selective Reduction of Carbon Dioxide to Formate Products Using Hydrosilanes

Formate salts were found to be active and selective homogeneous catalysts for the hydrosilylation of CO2. Counter cations and solvents strongly affected their catalytic activity. The use of toluene as a solvent rendered the recyclable catalyst system. Lewis basic polar solvents such as N-methylpyrrolidone and dimethyl sulfoxide significantly accelerated the reaction. The turnover number approached up to 1800. Analyses of the Fourier-transform infrared spectroscopy and in situ 1H nuclear magnetic resonance spectra suggested that the catalysis proceeds via electron donation from the solvent to hydrosilane, thereby accelerating the hydride transfer step.

Challenges and opportunities for using formate to store, transport, and use hydrogen

Abstract In this perspective article, the synthesis and thermodynamic properties of aqueous solutions of formate salts (FS, HCO2−) are described in relationship to the concept of H2 carriers. The physiochemical properties of solid FS, aqueous formate solutions, and aqueous bicarbonate solutions set the limitations for storage capacity, deliverable capacity, and usable H2 capacity of these H2 carriers, respectively. These parameters will help in the design of systems that use H2 carriers for storage and transport of H2 for fuel cell power applications. FS, as well as admixtures with formic acid (FA, H2CO2), have potential to address the goals outlined in the U.S. Department of Energy's H2@scale initiative to store in chemical bonds a significant quantity of energy (hundreds of megawatts) obtained from large scale renewable resources.

(Keynote) Electroreduction of CO2 on Pb and Bi Nanoneedles

The rise in atmospheric CO2 concentration since the beginning of the Industrial Age has raised concerns on its potential effect on global temperatures. While several factors such as natural climate changes, variations in solar activity, and volcanic eruptions may also contribute to observed variations in CO2 concentrations, it has been well established that anthropogenic emissions contribute to the annual emission of over 30 billion tonnes of CO2, only about half of which is recycled through natural pathways. CO2 conversion into value-added products is an avenue explored to mitigate environmental issues. Conversion methods appear promising, as they offer the potential to produce liquid and gaseous fuels for use either in the aeronautics industry, or as a chemical storage method for the intermittent energy produced by windmills and photovoltaic panels. Fuel synthesis may be achieved via either the production of a syngas mixture (H2 and CO) through the water gas shift reaction and subsequent conversion into hydrocarbon fuel through processes such as Fisher-Tropsch, or by direct electrochemical reduction of CO2. While all methods may result in similar conversion yields, depending on the catalyst used, direct electrochemical conversion of CO2 into value-added products is a low-temperature process, with the further advantage of requiring relatively simple equipment. Formic acid, or formate salts, are used in a variety of chemical processes such as electrowinning, leather tanning, and aircraft de-icing. Alternatively, formic acid and formate salts may be considered a hydrogen storage medium. Direct formic acid, and more recently, direct formate fuel cells, have been investigated in the literature as they demonstrate significant benefits over methanol fuel cells, including higher open circuit voltage and lower crossover. Among earth-abundant CO2 electrocatalysts, Sn, Pb and Bi are known to be highly selective for formate production, with faradic efficiency (FE) > 90%. However, several challenges need to be addressed for these materials to become viable alternatives for industrial applications based on an ERC process to become economically viable. In particular, issues related with large overpotential and low current densities need to be addressed, along with the long term stability of electrodes. In this study, we compared the activity and stability for CO2 electroreduction of high surface area metallic Bi and Pb nanoneedles (see Figure 1). In both cases, the materials films were prepared through a direct electrodeposition (potentiostatic method). Both types of films were extensively characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and x-ray diffraction (XRD), while electrochemical activities were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potentiostatic measurements. Figure 1

Thermal Stability of Sodium Formate in Polymer Drilling Fluids

The effects of formate salts on the rheological characteristics of water-based solutions were compared for two laboratory research methods, i.e., dynamic theological analysis at high temperature and high pressure (HTHP) and a static hot-roll aging test. Polymer muds were used for the measurements. HTHP rheology analysis showed that sodium formate retained effectively the dynamic viscosity at HTHP. Hot-roll tests showed that sodium formate had an obvious effect on the rheological characteristics of the polymer fluid at mom temperature after preliminary heating. The filtration loss of the polymer fluid with added sodium formate was slightly greater than that of pure polymer fluid although the filtration loss could be controlled by changing the formate concentration. Test results from both methods showed that sodium formate could be used successfully as a polymer drilling fluid stabilizer under HTHP operating conditions.

Mechanistic Insights into Ruthenium-Pincer-Catalyzed Amine-Assisted Homogeneous Hydrogenation of CO2 to Methanol

Amine-assisted homogeneous hydrogenation of CO2 to methanol is one of the most effective approaches to integrate CO2 capture with its subsequent conversion to CH3OH. The hydrogenation typically proceeds in two steps. In the first step the amine is formylated via an in situ formed alkylammonium formate salt (with consumption of 1 equiv of H2). In the second step the generated formamide is further hydrogenated with 2 more equiv of H2 to CH3OH while regenerating the amine. In the present study, we investigated the effect of molecular structure of the ruthenium pincer catalysts and the amines that are critical for a high methanol yield. Surprisingly, despite the high reactivity of several Ru pincer complexes [RuHClPNP R(CO)] (R = Ph/ i-Pr/Cy/ t-Bu) for both amine formylation and formamide hydrogenation, only catalyst Ru-Macho (R = Ph) provided a high methanol yield after both steps were performed simultaneously in one pot. Among various amines, only (di/poly)amines were effective in assisting Ru-Macho for methanol formation. A catalyst deactivation pathway was identified, involving the formation of ruthenium biscarbonyl monohydride cationic complexes [RuHPNP R(CO)2]+, whose structures were unambiguously characterized and whose reactivities were studied. These reactivities were found to be ligand-dependent, and a trend could be established. With Ru-Macho, the biscarbonyl species could be converted back to the active species through CO dissociation under the reaction conditions. The Ru-Macho biscarbonyl complex was therefore able to catalyze the hydrogenation of in situ formed formamides to methanol. Complex Ru-Macho-BH was also highly effective for this conversion and remained active even after 10 days of continuous reaction, achieving a maximum turnover number (TON) of 9900.

Effect of Calcium Formate on Hydrodeoxygenation of Biomass Model Compounds

Hydrothermal liquefaction of biomass model compounds (cellulose, xylan, and lignin) was carried out between 350 and 400 °C using calcium formate (Ca(HCOO)2) as the in situ hydrogen source. In this study, high temperatures have been adopted for liquefaction as calcium formate acts as a hydrogen donor in that range. Ca(HCOO)2 catalyzes lignin degradation toward liquefaction and, consequently, increases the biocrude yields by about 80%. Conversely, cellulose biocrude yields decreased when Ca(HCOO)2 was introduced due to pronounced gasification. It was also observed that Ca(HCOO)2 did not have any effect on xylan biocrude yield which remained almost the same. The maximum biocrude yields of cellulose, xylan, and lignin in the presence of Ca(HCOO)2 were 7, 13, and 32 wt %, respectively. The excess hydrogen from Ca(HCOO)2 was successful in upgrading the biocrude by removing oxygen which was confirmed by a significant decrease in atomic O/C ratio and increase in heating values (by 34.6%). The formate salt slightl...