Formate to Oxalate: A Crucial Step for Conversion of ...

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Formate to Oxalate: A Crucial Step for Conversion of CO2 into Multi-carbon Compounds. Detailed Literature Background Jerry J. Kaczur[a] [a]

Liquid Light, Monmouth Junction, NJ

DETAILED LITERATURE BACKGROUND A literature search covering the decomposition of formates and oxalates yielded a number references, both journal articles and patents, ranging back to the 1880’s. Some of the references have conflicting experimental results when compared to other researchers, which could be explained due to the different experimental conditions that were used, such as the thermal reaction atmospheres, temperature ranges, and the addition of catalysts to the thermal reaction. Several mechanisms for the thermal reactions were proposed. A detailed summary of the literature is provided below. Formate Decomposition to Oxalate - Journal Articles Boswell(1) provides an early summary of previous literature and patents regarding the thermal conversion of sodium formate to oxalate. In some of the earliest studies, Merz and Weith(2) , cited in Boswell(1), produced residues containing of at least 70% oxalate with the remainder carbonate was obtained by heating sodium formate rapidly to above 400°C, but that at about 360°C, the formation of carbonate was much greater. They proposed that the use of an admixture of sodium formate with sodium carbonate would provide a quantitative yield to sodium oxalate. Their proposed mechanism was as follows: (1) (2)

2HCOONa < = > Na2CO3 + H2 + CO CO + Na2CO3 < = > Na2C2O4

Also in the Boswell(1) paper, Levi and Pita(3) were cited, who stated that formate began to decompose at 300°C, and that the decomposition is violent at 400°C, with the reaction complete at 550°C. In later work, they also claimed that the use of small amounts of sodium hydroxide had a beneficial effect, producing technical grade sodium oxalate below the melting point of sodium formate. Leslie(4) reported the experimental work in determining the factors in the conversion of sodium formate to sodium oxalate. Sodium formate was mixed with varying amounts of sodium hydroxide and thermally decomposed under carefully controlled conditions of temperature and pressure using a molten salt bath and a vacuum reservoir. Their data showed that for a given temperature and pressure, there is an optimum percentage of sodium hydroxide catalyst. For example, at 2 in. of Hg (6.8 kPa) at 26°C, 14 in. of Hg (47.4 kPa) at 300°C, and at atmospheric pressure (101 kPa) at 360°C, the optimum NaOH concentration ranged from about 1 to 2 wt% to obtain nearly quantitative conversion to oxalate. No gas analysis data was conducted. The reaction time was set for 15 minutes. In many cases, the reaction was vigorous producing puffed up, porous mass.

Fisher(5) described known CO reactions, and stated that it was known that under high pressure, CO and metal hydroxides react easily to yield formates. He also stated that formates were found to react differently upon heating, and cited examples where potassium formate yields potassium oxalate and hydrogen, whereas zinc formate provided formaldehyde, methyl formate, and methanol in good yields (citing work by K. A. Hofmann – no referenced citation). Additionally, tin formate, according to Goldschmidt (no citation given, although Goldschmidt has published patents – see patent section), stated that tin formate decomposed almost quantitatively to formaldehyde. Canning(6) studied the thermal decomposition of alkaline earth formates, Mg, Ca, Sr, and Ba based formates, using thermogravimetric analysis (TG) in air. The final products were carbonates or oxides. They also observed that formic acid was present in the reaction products as well as carbon during the reactions. Meisel(7) conducted thermal decompositions of lithium, sodium, potassium, rubidium, and cesium formates using a dynamic thermo-analytical method. Reactions: Potential reactions forming carbonates, oxalate, CO2, H2 (3a) (3b) (3c) (3d) (3e) (3f) (3g)

2HCOOM  M2CO3 + CO + H2 (carbonate formation) 2HCOOM  M2C2O4 + H2 (oxalate formation) 2CO  CO2 + C M2C2O4  M2CO3 + CO M2CO3  M2O + CO2 2H2 + O2  2H2O 2CO + O2  2CO2

Meisel’s(7) results showed a high variability with the shape and type of crucible holder substrates that were used, such as platinum, corundum, aluminum oxide, and others. Catalytic effects were also investigated, using a 2 – 5 wt% of alkali metal hydroxide added to the corresponding alkali metal formate. Also investigated were the effects of sodium amide, as well as finely powdered copper. Meisel(7) could not achieve the oxalate high conversion yields reported in the literature. One explanation that they provided was that their tests at ambient pressure versus those studies that conducted testing as a function of pressure. Baraldi(8) analyzed the IR emission spectra of twelve metal formates under heating in air at atmospheric pressure and under a dynamic vacuum of 10-2 Torr. The final products during the runs were carbonates, metal oxides, and a mix of metal and metal oxides at the ending temperatures for each formate compound. Sodium formate indicated the formation of oxalate in the IR spectra when heated in a vacuum at temperatures of about 300°C and 305°C. The intermediate oxalate product decomposed to carbonate when the temperature was run to 475°C. Górski (9) systematically studied the influence of gaseous and solid reactants on the yields of oxalates and carbonates in the thermal decomposition of alkali metal formates, those being lithium, sodium, and potassium formates. Thermal decompositions of various formates were conducted in a thermogravimetric apparatus, an OD 202 derivatograph (MOM) providing TG, TDTG, DTA data and operating under nitrogen, hydrogen, CO, carbon dioxide, and oxygen atmospheres. The yield of sodium oxalate was shown to decrease as the heating rate was lowered. Elemental carbon was found

in the solid residues under a nitrogen atmosphere for the lithium formate conversion, but only traces for the other formates. The formate yields to oxalate in the various atmospheres did not exceed 54% with no catalyst or with the addition of sodium carbonate for all three alkali metal formates. The addition of a base, such as NaOH to sodium formate, and KOH to potassium formate in a 1: 0.05 molar ratio achieved a 92 – 93% conversion to the corresponding alkali metal oxalate. Lithium hydroxide to lithium formate only produced a low 25% conversion to oxalate. The addition of LiOH to sodium formate only produced a 49% conversion yield. The addition of sodium borohydride to sodium formate resulted in an 88% conversion yield, which declined to a 0% conversion using a 1:1 molar ratio. Górski(9) described a mechanism based on a short-lived CO22- anion formation to produce an oxalate as follows: (4)

2HCO2-  H2 + CO2 + CO22-

(5)

CO22- + CO2  C2O42-

Górski(9) postulated that the experimental results indicate the occurrence of an acidbase reaction in the system, and that an increase in the concentration of basic species, such as hydroxide and hydride ions, favors oxalate formation. CO2 is an acid species in the reaction, as indicated by lower yields of formate to oxalate in a CO2 atmosphere. Górski(10) investigated the influence of the cation on the formation of free hydrogen and formaldehyde in the thermal decomposition of formates in this paper. Sodium borohydride, sodium formate and tin formate under a nitrogen atmosphere were used in the investigation of the mechanism for the thermal decomposition. The heterolytic cleavage of the H-C bond of the formate anion was proposed as the first stage in the thermal decomposition, causing the formation of carbon dioxide and a hydride anion as follows: (6)

HCO2-  H- + CO2

The thermal decomposition of tin formate produces carbon dioxide, formaldehyde, and tin oxide under a vacuum. Methyl formate was a product found under normal pressure using an inert gas. The proposed thermal decomposition stages by Górski(10) are as follows from their interpretation of the experimental results as three stages: Stage I, independent of the nature of the cation: (6)

HCO2-  H- + CO2

Stage II, dependent on the nature of the cation: a) For cations forming strongly polarized bonds (largely ionic) with the hydride ion (7)

H- + HCO2-  H2 + CO22-

b) For cations forming weakly polarized bonds (largely covalent)

(8)

H- + HCO2-  H2CO22-  HCHO + O2-

c) For cations forming complex type of bonds, a combination of the three reactions, 6, 7, and 8. Stage III, which is dependent on the metal oxide formed, and where formaldehyde undergoes other chemical transformations such as a Cannizzaro or Tishchenko reactions. Masuda(11) investigated the thermal phase transformations of lithium, sodium, and potassium formate using thermogravimetric (TG), differential thermal analysis (DTA), differential scanning calorimetry, and X-ray powder diffraction. The monoclinic phase of sodium formate transformed to a triclinic phase at 237°C and the orthorhombic phase of potassium formate transformation into a monoclinic phase at 135°C just before their melting points with a small endothermic peak. Kudo(12) investigated the synthesis of oxalate from CO and CO2 in the presence of cesium carbonate. Oxalate yields based on the charged cesium carbonate were as high as 90% at a temperature of 380 °C, using partial pressures of 50 atm for CO and 110 atm for CO2 at a reaction time of 2 hrs. Their mechanistic and 13C studies using 13C labeled CO2 and non-labeled CO showed that the 13C was incorporated into the oxalate carbonyl. They also found that cesium oxalate formed from labeled 13C cesium carbonate did not have any 13C incorporated into the oxalate. They concluded that the carbonyl origin in oxalate formation in these reactions took place between CO and CO2. Oxalate Thermal Decomposition Papazian(13) conducted a detailed experimental study of the decomposition of ammonium and potassium oxalate simultaneously using TGA and DTA. Potassium oxalate, as the monohydrate, lost its water of crystallization by 120°C, and the anhydrous potassium oxalate showed decomposition between 540°C and 630°C in air, and 610°C and 680°C in vacuum. An endothermic dip for potassium oxalate DTA/TGA seen in Fig. 2 at about 380°C corresponds to a phase change noted in the data in Dollimore(14) Table 3. Dollimore(14) conducted a literature review on the thermal decomposition of oxalates. The decomposition routes for oxalates are affected by the environment – reactions with nitrogen, air, or oxygen used in the DTA all were found to have a pronounced effect on the chemistry occurring on the surfaces of the oxalates being evaluated. The oxalate decomposition products for Co, Ni, Cd, Sn, Pb, and Ag oxalates all produce a metal product. Bi and Sb produce mixture of metal and oxide. Mg, Al, Cr, Mn, Fe, Ce, Th, Pr, La, and Zn oxalates all produce oxides. Li, Na, K, Ca, Sr, and Ba oxalates all produce carbonates. Górski(15) conducted a detailed study on the decomposition of alkali and alkaline earth metal oxalates, investigating whether the CO2-2 anion may be involved in the decomposition reactions. Górski(14) detailed the results of the decomposition of, for example, Li, Na, Ca, and Ba oxalates under various atmospheres, including He, Ar, N2,

CO and CO2. The solid products were all carbonates and elemental carbon, and the main gaseous products being CO and CO2. Formate Decomposition to Oxalate – Patent Art Goldschmidt(16) in US Patent 659,733 describes a process for producing sodium oxalate formate from the thermal decomposition of sodium formate. Sodium carbonate was mixed with the sodium formate in a ratio of 4 parts of sodium formate with 5 parts of sodium carbonate, and processed at a temperature of about 400 - 410°C for 35-40 minutes. Proposed some potential decomposition reactions No formate to oxalate conversion data was disclosed. Weins(17) in US Patent 714,347 described producing sodium oxalate from a mixture of sodium formate and sodium oxalate thermally processed at a temperature between 360 - 410°C. No formate to oxalate conversion data was disclosed. Weins(18) in US Patent 973,832 described producing sodium oxalate with no catalyst additives, but operating the thermal reaction under a vacuum at a temperature of 280 360°C. No formate to oxalate conversion data was disclosed. Strauss(19) in US Patent 1,038,985 described a process converting sodium formate to sodium oxalate at temperatures of about 400°C for 15 – 30 minutes in a partial vacuum and using no catalyst additives. An equipment apparatus was also disclosed for conducting the reaction. No formate to oxalate conversion data was disclosed. Hempel(20) in US Patent 1,070,806 described a process for converting sodium formate sodium oxalate by reacting the formate in a 30% CO gas atmosphere at a temperature between 300 - 440°C. No formate to oxalate conversion data was disclosed. Lackman(21) in US Patent 1,274,169 described a process for converting sodium formate to sodium oxalate by reacting the formate in a CO gas atmosphere at a temperature between 360 - 440°C. equipment and operating conditions were described. No formate to oxalate conversion data was disclosed. Andrews(22) in US Patent 1,280,622 described a process for converting a mixture of sodium formate with the addition of sodium phosphate to sodium oxalate at a temperature of about 380°C. The mixture contained 2 – 3 wt% of tri-sodium phosphate in the sodium formate mixture. No formate to oxalate conversion data was disclosed. Andrews(23) in US Patent 1,281,117 described a process for converting a mixture of sodium formate with the addition of sodium arsenate to sodium oxalate at a temperature of about 380°C. The mixture contained 2 – 3 wt% of sodium arsenate in the sodium formate mixture. No formate to oxalate conversion data was disclosed. Andrews(24) in US Patent 1,281,118 described a process for converting a mixture of sodium formate with the addition of sodium aluminate to sodium oxalate at a temperature of about 380°C. The mixture contained 2 – 3 wt% of sodium arsenate in the sodium formate mixture. No formate to oxalate conversion data was disclosed.

Paulus(25) in US Patent 1,420,213 described a process and apparatus for first producing sodium formate from the reaction of sodium hydroxide with CO at 175°C, followed by passing the finely divided sodium formate into a heated zone to convert it to sodium oxalate. The thermal reaction temperature was between 360 - 440°C, with a 98% conversion of sodium formate to sodium oxalate in a reaction time ranging from seconds to minutes. Paulus(26) in US Patent 1,445,163 described a process and apparatus for converting sodium formate to sodium oxalate in the presence of air. The sodium formate is subjected to a temperature between 220 - 360°C to form a melt, which is then spread thinly as a liquid over hot surfaces heated to a temperature between 360 - 440°C, where the reaction to sodium oxalate takes place in 2 to 3 seconds with a quantitative yield conversion of formate to oxalate. Wallace(27) in US Patent 1,506,872 described a process in forming a sodium formate melt, and then subjecting the melt to a temperature between 380 - 440°C to produce a sodium oxalate product at a 90% yield without the addition of catalysts. A caustic alkali as well as other materials could be added when the formate is in a molten condition to improve yields. Reaction time was not disclosed. Wallace(28) in US Patent 1,602,802 describes a process for producing sodium formate from a mixture of calcium hydroxide and sodium oxalate at 130°C and addition of CO gas at a reaction pressure of 65 psig. The formate is melted to about 251°C, and then placed into a reaction vessel which is preheated to 440°C to produce sodium oxalate at a conversion yield of 90%. Enderli(29) in US Patent 2,033,097 describes a process for the preparation of potassium oxalate from potassium formate. A low partial pressure of hydrogen (0.1 atm) was found to produce potassium formate conversions of up to 97% at a temperature of 360°C with the addition of 0.5 – 1 wt% of KOH. Higher atmospheric hydrogen pressures were found to decrease the conversion yields to oxalate when reacted at a constant temperature. Other experimental results that were observed was that the injection of nitrogen at 300 350°C into a potassium formate melt containing 3 wt% free caustic gradually became a solid with the liberation of hydrogen and contained after 1.5 hours about 95% potassium oxalate. Alternatively, passing hot CO reduced the potassium oxalate yield to 20%. Nitrogen with 25% CO increased the oxalate yield to about 52%. A higher alkali hydroxide content of 10 wt% in the reaction mixture at a temperature of 400°C only had a conversion yield of 81%. Yu(30) in Chinese Patent Application CN1502599A describes a process for producing sodium oxalate from sodium formate adopting a spray-liquor type equipment. A sodium formate solution with a specific concentration, about 45 – 50 wt%, is first heated to 180 205°C, and then pumped through a heat exchanger at a temperature of 900 - 1050°C for adequate heat to achieve the dehydrogenation reaction, and sprayed into a hot blast furnace, with recovery of the sodium oxalate, water vapor, and hydrogen. Conversion yield of 90% is obtained and lower total energy expenditures. Yuejun(31) in Chinese Patent CN 100999462B describes a process for producing sodium oxalate from sodium formate utilizing continuous fluidized bed reactor. The sodium formate is fed to the fluidized bed using an auger, the fluidized bed has a hot gas stream entering the bottom of the fluidized bed at a temperature of about 500°C, and the sodium

formate is reacted to about 420°C in the fluidized bed for the dehydrogenation reaction. The sodium oxalate, steam, and hydrogen are separated using a cyclone separator. Anmin(32) in Chinese Patent CN1903821B describes a process for producing sodium oxalate from sodium formate utilizing a superheated steam gas stream for melting the sodium formate and then used as the gas carrier and heating in the dehydrogenation reaction using an injection mixer. The sodium formate conversion reaction occurs in a reaction pipe, and then enters cyclone separator to separate the oxalate product from the gases, steam and hydrogen.

REFERENCES Journal Articles 1. Boswell, Maitland, C., and Dickson, J. V., The Action of Sodium Hydroxide on Carbon Monoxide, Sodium Formate, and Sodium Oxalate”, J. Am. Chem. Soc., 1918, 40 (12), 1779-1786. 2. Merz and Weith, Ber., 15, 1507 (1882). Cited in Boswell(4) article. German Chemical Society, Vol. 13, p.721 3. Levi and Pita, Ann. Chim. Applicata I. pp 1-24. Cited in Boswell(4) article. 4. Leslie, E. H., and Carpenter, C. D., “Factors in the Conversion of Sodium Formate to Oxalate”, Chemical and Metallurgical Engineering, Jun. 30, 1920, 1195-1197. 5. Fischer, Franz, “Liquid Fuels from Water Gas”, Industrial and Engineering Chemistry, Vol. 17, No. 6, 1925. 6. Canning, R. and Hughes, M. A., “The Thermal Decomposition of Alkaline Earth Formates”, Thermochimica Acta, 6 (1973) 399-409. 7. Meisel, T., Halmos, Z., Seybold, K., and Pungor, E., “The Thermal Decomposition of Alkali Metal Formates”, Journal of Thermal Analysis, Vol. 7 (1975), 73-80. 8. Baraldi, Pietro, “Thermal Behaviour of Metal Carboxylates: Metal Formates, Spectrochimica Acta, Vol. 35A, 1979, 1003-1007. 9. Górski, A. and Kraśnika, A. D., “Formation of Oxalates and Carbonates in the Thermal Decompositions of Alkali Metal Formates”, Journal of Thermal Analysis, Vol. 32 (1987) 1895-1904. 10. Górski, A. and Kraśnika, A. D., “Influence of the Cation on the Formation of Free Hydrogen and Formaldehyde in the Thermal Decomposition of Formates”, Journal of Thermal Analysis, Vol. 32 (1987) 1345-1354. 11. Masuda, Yoshio, Hashimoto, Kazuhito, and Ito, Yoshio, “The Thermal Phase Transformation of Lithium, Sodium, and Potassium Formates”, Thermochimica Acta, 163 (1990) 271-278. 12. Kudo, Kiyoshi, Ikoma, Futoshi, Mori, Sadayuki, Komatsu, Koichi, and Sugata, Nobuyuki, “Synthesis of Oxalate from Carbon Monoxide and Carbon Dioxide in the Presence of Caesium Carbonate”, J. Chem. Soc., Perkin Trans. 2, 1997, 679-682. Oxalate Thermal Decomposition 13. Papazian, H. A., Pizzolato, P. J., and Partick, J. A., “Thermal Decomposition of Oxalates of Ammonium and Potassium”, J. American Ceramic Society, Vol. 54, No. 5, Mya 1971, 250-254. 14. Dollimore, D., “The Thermal Decomposition of Oxalates: A Review”, Thermochimica Acta, 117 (1987) 331-363.

15. Górski, A. and Kraśnika, A. D., “The Importance of the CO22- Anion in the Mechanism of Thermal Decomposition of Oxalates”, Journal of Thermal Analysis, Vol. 32 (1987) 1229-1241. Patent Art 16. Goldschmidt, Martin, US Patent 659,783, “Process of Making Oxalates”, issued Oct. 16, 1900. 17. Wiens, Arnold, US Patent 714,347, “Process of Making Oxalates”, issued Nov. 25, 1902. 18. Wiens, Arnold, US Patent 973,832, “Process of Making Oxalates From Formates”, assigned to Electrochemische Werke G. M. B. H., Bitterfeld, Germany, issued Oct. 25, 1910. 19. Strauss, David, US Patent 1,038,985, “Manufacture of Oxalates”, assigned to the Society of Chemical Industry in Basel, Basel, Switzerland, issued Sep. 17, 1912 20. Hempel, Albert, US Patent 1,070,806, “Process of Making Oxalates”, issued Aug. 1913. 21. Lackman, Alexander, US Patent 1,274,169, “Manufacture of Formates and Oxalates”, issued Jul. 30, 1918. 22. Andrews, Launcelot W., US Patent 1,280,622, “Process for Manufacturing Oxalates”, issued Oct. 8, 1918. 23. Andrews, Launcelot W., US Patent 1,281,117, “Process for Manufacturing Oxalates”, issued Oct. 8, 1918. 24. Andrews, Launcelot W., US Patent 1,281,118, “Process for Manufacturing Oxalates”, issued Oct. 8, 1918. 25. Paulus, Herman. W., US Patent 1,420,213, “Manufacture of Oxalate”, assigned to Royal Baking Powder Company, NJ, issued Jun. 20, 1922. 26. Paulus, Herman. W., US Patent 1,445,163, “Manufacture of Oxalate”, assigned to Royal Baking Powder Company, NJ, issued Feb. 13, 1923. 27. Wallace, Walter, US Patent 1,506,872, “Producing Oxalates from Formates”, assigned to Oldbury Electrochemical Company, Niagara Falls, NY, issued Sep. 2, 1924. 28. Wallace, Walter, US Patent 1,602,802, “Manufacture of Oxalates and Oxalic Acids”, assigned to Oldbury Electrochemical Company, Niagara Falls, NY, issued Oct. 12, 1926. 29. Enderli, Max, and Schrodt, August, US Patent 2,033,097, “Process for the Preparation of Potassium Oxalate from Potassium Formate”, assigned to Rudolph Koepp & Co. Chemische Fabrik A. G., Oestrich, Germany, issued Mar. 3, 1936. 30. Yu, Xueping, Chinese Patent Application CN 1502599A, “Technological Process for Producing Sodium Oxalate by Liquid-Spraying Type Sodium Formate Dehydrogenation and Use Equipment”, Published Jun. 9, 2004. (Machine Translation into English). 31. Yuejun, Li, Qinglan, Ma, Anmin, Li, Fenglei, Li, ChenGcen, Liu, and Qiaoliang, Li, Chinese Patent CN 100999462B, “Process and Equipment of Continuous Dehydrogenating Producing Sodium Oxalate by Circulating Fluidized Bed (English Translation), issued Aug. 11, 2010. (Machine Translation into English). 32. Anmin, Li, Zhijun, Zhao, Aihua, Zhang, Zhong, Li, and Yueyun, Li, Chinese Patent CN 1903821B, “Technology of Producing Sodium Oxalate by Continuous Dehydrogenation of Sodium Formate and its Equipment”, issued May 23, 2012. (Machine Translation into English).