WO2016024293A1

WO2016024293A1 - Metal catalyzed process for reduction of co2 to sodium formate and formic acid

Info

Publication number: WO2016024293A1
Application number: PCT/IN2015/050090
Authority: WO
Inventors: Sanjay Pandurag KAMBLE; Rupali Gundappa KALSHETTI; Venkataramasubramanian VAITHIYANATHAN; Arumugam Sudalai
Original assignee: Council Of Scientific & Industrial Research
Priority date: 2014-08-12
Filing date: 2015-08-12
Publication date: 2016-02-18

Abstract

The patent discloses a one step, one pot metal catalyzed process for synthesis of formic acid or sodium formate from CO₂ in the presence of reducing agent and a catalyst or without catalyst at moderate temperature and atmospheric pressure with high yields.

Description

METAL CATALYZED PROCESS FOR REDUCTION OF C0₂ TO SODIUM FORMATE AND FORMIC ACID

FIELD OF THE INVENTION

[001] The present invention relates to a process for the synthesis of sodium formate and formic acid from carbon dioxide. Particularly, present invention relates to a one step, one pot process for synthesis of formic acid or sodium formate from C0₂ or carbonate salt in the presence of a catalyst at low temperature and atmospheric pressure.

BACKGROUND AND PRIOR ART OF THE INVENTION

[002] Carbon dioxide (C0₂) is a major greenhouse gas, and it is also a nontoxic, abundant and inexpensive carbon source. Transformation of C0₂ into value-added chemicals is of vital importance. Different routes have been developed for the conversion of C0₂ into valuable products such as formic acid, methanol, urea, carbonate and dimethyl formamide. Among the formic acid, conveniently obtained by hydrogenation of C0₂, is highly attractive as formic acid is an important chemical used as preservative and antibacterial agent in food as well as the tanning of leather. The various methods such as are hydrogenation, hydrothermal and photocatalytic reduction are used for conversion of the C0₂ into value added chemicals. Photocatalytic C0₂ reduction with H₂0 is of significance importance for production of hydrocarbon fuels and value added chemical such as CO, C¾OH, CH₄, HCOOH and HCHO. In hydrogenation process H₂ gas is used as a hydrogen source for reduction of C0₂ & this reaction is performed at high temperature and high pressure. The yield of formic acid in this process was found in the range of 30-35%. In photocatalytic process C0₂ is reduced into formic acid using artificial or solar radiation. Transition-metal-catalyzed homogeneous hydrogenation of C0₂ often leads to either formic acid that is thermodynamically stabilized by a base or CO via the reverse process of the water-gas shift reaction. [003] In aqueous solution, the hydrogenation of C0₂ into formic acid is the thermodynamically unfavorable. Currently, the reduction of C0₂ into formic acid is predominantly focused on homogeneous catalysts. A variety of organometallic catalysts based on Ru, Ir, Rh, Fe has been developed for the hydrogenation of C0₂ into formic acid. Although homogeneous catalysts proved to be very successful in terms of achieving high catalytic activity, they are intrinsically associated with a few limitations. For instance, the ligand and the catalyst are sometimes not readily available and/or the costs are high. Removing the catalyst from product is also very difficult, which makes the recycle and reuse challenging. These limitations can be easily overcome by using heterogeneous catalysts. Various heterogeneous catalyst such as Raney nickel, copper zinc oxide, immobilized ruthenium complex catalyst on silica and polystyrene resin has been studied for conversion of C0₂ into formic acid. The limitation of this heterogeneous reaction is that reaction occurs at high temperature and high pressure.

[004] US 8791297 B2 discloses a process for preparing formic acid by reaction of carbon dioxide (1) with hydrogen (2) in a hydrogenation reactor (I) in the presence of a catalyst comprising an element of group 8, 9 or 10 of the Periodic Table, a tertiary amine comprising at least 12 carbon atoms per molecule and a polar solvent comprising one or more monoalcohols selected from among methanol, ethanol, propanols and butanols and also water, to form formic acid/amine adducts as intermediates which are subsequently thermally dissociated, with work-up of the output (3) from the hydrogenation reactor (I) in a plurality of process steps, where a tertiary amine-comprising stream (13) from the work-up is used as selective solvent for the catalyst. The temperature is in the range from 20 to 200 °C, pressure in the range from 0.2 to 30 MPa and yield <10%.

[005] EP 2763950 A2/WO 2013050367 A3 relates to a method for producing formic acid, comprising the following steps: (a) reacting, in a homogeneously catalyzed manner, a reaction mixture (Rg) containing carbon dioxide, hydrogen, at least one polar solvent and at least one tertiary amine in the presence of at least one coordination catalyst in a hydrogenation reactor in order to obtain a two-phase hydrogenation mixture (H) containing an upper phase (01), which contains the at least one coordination catalyst and the at least one tertiary amine (Al), and a lower phase (Ul), which contains the at least one polar solvent, residues of the at least one coordination catalyst, and at least one formic acid/amine adduct.

[006] US 8946462 B2 relates to a process for preparing formic acid by reaction of carbon dioxide with hydrogen in a hydrogenation reactor in the presence of a transition metal complex as a catalyst comprising at least one element from group 8, 9 or 10 of the Periodic Table and at least one phosphine ligand with at least one organic radical having at least 13 carbon atoms, of a tertiary amine and of a polar solvent to form a formic acid-amine, adduct, which is subsequently dissociated thermally to formic acid and the corresponding tertiary amine, on unit.

[007] Article titled,"A Cobalt-Based Catalyst for the Hydrogenation of C0₂ under Ambient Conditions" by Matthew S. Jeletic , Michael T. Mock , Aaron M. Appel and John C. Linehan in J. Am. Chem. Soc, 2013, 135 (31), pp 11533-11536 reports a cobalt- based catalyst system for the production of formate from C0₂ and H₂. The complex Co(dmpe)₂H (dmpe is l,2-bis(dimethylphosphino)ethane) catalyzes the hydrogenation of C0₂, with a turnover frequency of 3400 h^"1 at room temperature and 1 atm of 1 : 1 C0₂:H₂ (74 000 h-1 at 20 atm) in tetrahydrofuran. [008] Article titled, "Mechanistic insights into hydride transfer for catalytic hydrogenation of C0₂ with cobalt complexes" by N. Kumar, D. M. Camaioni, M. Dupuis, S. Raugei and A. M. Appel in Dalton Trans., 2014,43, 11803-11806 reports the catalytic hydrogenation of C0₂ to formate by Co(dmpe)₂H via direct hydride transfer or via C0₂ coordination to Co followed by reductive elimination of formate. [009] Article titled, "Cp*Co(III) Catalysts with Proton-Responsive Ligands for Carbon Dioxide Hydrogenation in Aqueous Media" by Yosra M. Badiei et. al in Inorg. Chem., 2013, 52 (21), pp 12576-12586 reports new water-soluble pentamethylcyclopendadienyl cobalt(III) complexes with proton-responsive 4,4'- and 6,6'-dihydroxy-2,2'-bipyridine (4DHBP and 6DHBP, respectively) ligands. The cobalt complexes containing 4DHBP ligands ([l-OH₂]²⁺ and [1— Cl]⁺) display better thermal stability and exhibit notable catalytic activity for C0₂ hydrogenation to formate in aqueous bicarbonate media at moderate temperature under a total 4-5 MPa (C0₂:H₂ 1 : 1) pressure.

[010] Article titled, "A Cobalt Hydride Catalyst for the Hydrogenation of C0₂: Pathways for Catalysis and Deactivation" by Matthew S. Jeletic et. al in ACS Catal., 2014, 4 (10), pp 3755-3762. This article report the complex Co(dmpe)₂H catalyzes the hydrogenation of C0₂ at 1 atmospheric and 21 °C with significant improvement in turnover frequency relative to previously reported second- and third-row transition- metal complexes. New studies are presented to elucidate the catalytic mechanism as well as pathways for catalyst deactivation. The catalytic rate was optimized through the choice of the base to match the pKa of the [Co(dmpe)₂(H)₂]⁺ intermediate. With a strong enough base, the catalytic rate has a zero^th-order dependence on the base concentration and the pressure of hydrogen and a firstorder dependence on the pressure of C0₂. However, for C0₂:H₂ ratios greater than 1, the catalytically inactive species [(μ-dmpe)- (Co(dmpe)₂)₂] and [Co(dmpe)₂CO] were observed.

[011] Article titled, "Hydrogenation of Carbon Dioxide Using Half-Sandwich Cobalt, Rhodium, and Iridium Complexes: DFT Study on the Mechanism and Metal Effect" by Cheng Hou et. al in ACS Catal., 2014, 4 (9), pp 2990-2997, reports the hydrogenation of carbon dioxide catalyzed by half-sandwich transition metal complexes (M = Co, Rh, and Ir). All metal complexes are found to process a similar mechanism, which involves two main steps, the heterolytic cleavage of H₂ and the hydride transfer. The heterolytic cleavage of H₂ is the rate- determining step. The comparison of three catalytic systems suggests that the Ir catalyst has the lowest activation free energy (13.4 kcal/mol). In contrast, Rh (14.2 kcal/mol) and Co (18.3 kcal/mol) catalysts have to overcome relatively higher free energy barriers. The different catalytic efficiency of Co, Rh, and Ir is attributed to the back-donation ability of different metal centers, which significantly affects the H₂ heterolytic cleavage. The highest activity of an iridium catalyst is attributed to its strong back-donation ability, which is described quantitatively by the second order perturbation theory analysis. Our study indicates that the functional group of the catalyst plays versatile roles on the catalytic cycle to facilitate the reaction. It acts as a base (deprotonated) to assist the heterolytic cleavage of H₂. On the other hand, during the hydride transfer, it can also serve as Bronsted acid (protonated) to lower the LUMO of C0₂. This ligand assisted pathway is more favorable than the direct attack of hydride to C0₂. These finds highlight that the unique features of the metal center and the functional ligands are crucial for the catalyst design in the hydrogenation of carbon dioxide.

[012] Article titled, "C0₂ Fixation through Hydrogenation by Chemical or Enzymatic Methods" by Prof. Matthias Beller and Prof. Uwe T. Bornscheuer in Angewandte Chemie International Edition, Volume 53, Issue 18, pages 4527-4528, 2014 reports the simulaneous fixation of the greenhouse gas carbon dioxide and storage of the alternative fuel hydrogen can be accomplished with the formation of formic acid. In principle, this is now possible either with an enzymatic system based on a newly discovered bacterial hydrogen-dependent carbon dioxide reductase or by using organometallic catalysts at room temperature and ambient pressure.

[013] Article titled, "Germanium(II) hydride mediated reduction of carbon dioxide to formic acid and methanol with ammonia borane as the hydrogen source" by Anukul Jana in Dalton Trans., 2010,39, 9487-9489 reports LGeOC(0)H (3) (L = CH{(CMe)(2,6-iPr₂C₆H₃N)}₂), from the straightforward conversion of LGeH (2) with C0₂, reacts with LiH₂NBI¾ giving 2 and LiOC(0)H (4), while the corresponding reaction of 3 with H₃NBH₃ after aqueous workup releases 2 and CH₃OH (5). This opens the possibility to use hydride 2 as a mediator in the reduction of carbon dioxide to formic acid and methanol.

[014] Aricle titled, "A Study of Methyl Formate Production from Carbon Dioxide Hydrogenation in Methanol over a Copper Zinc Oxide Catalyst" by K. M. Kerry Yu, Shik Chi Tsang in Catalysis Letters, 2011, Volume 141, Issue 2, pp 259-265 reports the production of methyl formate (MF) from C0₂ hydrogenation in liquid methanol was carried out over a Cu/ZnO/A^C based catalyst which was synthesized by a precipitation technique following a well established route. The effects of amine concentration, hydrogen pressure, temperature, CO and water addition on the activity and selectivity of MF were investigated. It is of interest to note that the addition of 1% trimethylamine can dramatically increase the initial turnover frequency with the MF being the major product. It is evident that the formation of C0₂-amine adduct promotes the catalytic hydrogenation of C0₂ on the surface of the catalyst.

[015] No commercially available processes exist for the conversion of C0₂ to fuels and chemicals yet. The challenges presented are great, but the potential rewards are enormous. To address this challenging scientific problem, we need to advance our fundamental understanding of the chemistry of C0₂ activation and develop novel multifunctional catalysts or reducing system that could use electricity, solar energy or chemical energy to efficiently break C-0 bond and form C-H and C-C bonds. So storing energy in chemical bonds through the conversion of inexpensive substrates to fuels is one route to enabling the storage of carbon-neutral energy.

[016] Although some of the efforts was carried for the reduction of C0₂ to HCOOH still many various methods needs to be developed using effective and environmentally benign reducing system. Despite carbon dioxide an extremely attractive carbon source that is readily available, inexpensive, and inherently renewable, C0₂ is the most oxidized state of carbon and in its low energy level utilization becomes difficult. There are three main methodologies to transform C0₂ into useful chemicals: (i) to use high- energy starting materials, (ii) To choose oxidized low-energy synthetic targets, (iii) To supply physical energy such as light or electricity. However, due to the electron deficiency of the carbonyl carbons, C0₂ has a strong affinity toward nucleophiles and electron-donating reagents. Development of catalytic methods of chemical transformation of C0₂ into useful compounds is of paramount importance from stand point of Ci chemistry and so called green chemistry. Hence we were interested in accomplishing the utilization of C0₂ to convert it to HCOOH and in turn finally we wished to obtain the fuel such as methanol.

[017] However the reported process have limitations such as reaction rate is very slow, other sides products are also formed and yield of formic acid is very low. Therefore there is need to develop a process for transformation of C0₂ into formic acid and other useful products with high yield using cheap raw materials.

OBJECTIVE OF THE INVENTION

[018] The main object of the present invention is to provide a process for utilization of C0₂ or carbonate salt for the synthesis of formic acid or sodium formate.

[019] Another object of the present invention is to provide a process for the synthesis of formic acid or sodium formate under mild conditions.

SUMMARY OF THE INVENTION

[020] Accordingly, present invention provides a one step, one pot metal catalyzed process for the synthesis of HCOOR wherein R is selected from H or Na comprising the step of:

i. reacting the C0₂ source at a temperature in the range of 50-90°C for period in the range of 6-24 hours at atmospheric pressure in the presence of a reducing agent, a catalyst, a polarsolvent and optionally a base to obtain HCOOR wherein R is selected from H or Na.

[021] In an embodiment of the present invention, yield of HCCOR is in the range of 0.90 to 98.98%. [022] In another embodiment of the present invention, the reducing agent used is selected from the group consisting of NaN0₃, LiAH₄, hydrazine hydrate, absorbic acid, NaBH₄.

[023] In yet another embodiment of the present invention, the catalyst used is selected from the group consisting of CoCl2,Ti02, ZnO, CuO, metal-doped-TiCh or ZrC>₂ or Cu nanoparticles.

[024] In yet another embodiment of the present invention, the CO₂ source is selected from the group consisting of CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃); K₂HC0₃, MgC0₃, MgHC0₃, BaC0₃, BaHC0₃, Rb₂C0₃, MnC0₃, CoC0₃, NiC0₃ direct CO₂ gas or atmoshpheric CO₂ gas.

[025] In yet another embodiment of the present invention, the polar solvent used is selected from water or ethanol.

[026] In yet another embodiment of the present invention, the base used is diisopropyl amine.

[027] In yet another embodiment, present invention provides a process for reduction of CO₂ from source such as calcium carbonate wherein Aeroxide P-90 T1O₂ catalyst loading is in the range of 0.17 to 0.29 (w/v %); sodium nitrite (reducing agent) concentration is in the range of 4.3 g/1 to 15.7 g/1; temperature is in the range of 70 to 100 °C and pH is in the range of 5.7 to 10.2.

[028] In yet another embodiment, present invention provides a process for the preparation of formic acid, wherein the source of CO₂ is atmospheric CO₂ gas or direct CO₂ gas; metal salt catalyst is C0CI₂; polar solvent is ethanol and base is diisopropyl amine.

[029] In yet another embodiment, present invention provides a process for the preparation of sodium formate, wherein source of CO₂ is carbonate salt selected from CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃); K₂HC0₃, MgC0₃, MgHC0₃, BaC0₃, BaHC0₃, Rb2C0₃, MnC0₃, CoC0₃, NiC0₃ the metal oxide catalyst is T1O₂ ZnO, CuO, metal-doped-Ti0₂ or Zr0₂ and polar solvent is water. BRIEF DESCRIPTION OF THE DRAWINGS:

[030] Fig 1 : depicts gas chromatogram of authentic HCOOH.

[031] Fig 2: depicts gas chromatogram of HCOOH observed in experiment.

[032] Fig 3 : depicts Mass spectrum of authentic HCOOH.

[033] Fig 4: depicts Mass spectrum of HCOOH observed in experiment.

[034] Fig 5: depicts high pressure liquid chromatogram () of sodium

formate. DETAILED DESCRIPTION OF THE INVENTION

[035] Present invention provides a one step, one pot process for synthesis of formic acid or sodium formate from C0₂ or carbonate salt in the presence of reducing agent and a catalyst or without catalyst at moderate temperature and atmospheric pressure.

[036] The present invention provides a one step, one pot metal catalyzed improved process for the synthesis of formic acid with yield ranging from 5 to 35% or sodium formate with yield in the range of 0.90 to 98.98%, from C0₂ source comprising reacting the C0₂ at 50-90 °C for 6-24 hours at atmospheric pressure in the presence of a reducing agent, a catalyst, a polar solvent and optionally a base.

[037] The present invention provides a process wherein catalyst used is selected from metal, metal salt or metal oxide catalyst.

[038] The present invention provides a process wherein the source of C0₂ is selected from CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃), K₂HC0₃, MgC0₃, MgHC0₃, BaC0₃, BaHC0₃, Rb₂C0₃, MnC0₃, CoC0₃, NiC0₃ direct C0₂ gas or atmoshpheric C0₂ gas; the reducing agent is selected from NaN0₃, LiAH₄, hydrazine hydrate, absorbic acid, NaBH₄; the metal salt catalyst is CoCl₂; the metal oxide catalyst is selected from Ti0₂ (Aeroxide^® P-25 Ti0₂ and Aeroxide^® P-90 Ti0₂ was purchased from Evonik India Pvt. Ltd, Mumbai), ZnO, CuO, metal-doped-Ti0₂, Zr0₂; the metal catalyst used is Cu° (copper nanoparticle); the polar solvent is selected from water or ethanol; the base is diisopropyl amine.

[039] The present invention provides a process for the preparation of formic acid, wherein the source of C0₂ is atmospheric C0₂ gas or direct C0₂ gas; metal salt catalyst is CoCl₂; polar solvent is ethanol and base is diisopropyl amine.

[040] The above process is represented in Scheme 1

con.HCI O

HCOOH - A₀.Co(BH₃)₂N'Pr₂ where Co₂B is cobalt-boron complex.

[041] The present invention provides a process for the preparation of Sodium Fomate, wherein source of C0₂ is carbonate salt selected from CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃); K₂HC0₃, MgC0₃, MgHC0₃, BaC0₃, BaHC0₃, Rb₂C0₃, MnC0₃, CoC0₃, NiC0₃ the metal oxide catalyst is Ti0₂ and polar solvent is water.

[042] The process for the synthesis of formic acid from C0₂ results in a yield of up to 35%. The yield of formic acid was calculated by derivatizing it to benzylformate through the addition of benzylbromide in THF/DMF to the crude reaction mixture obtained after passing C0₂ to CoCl₂/NaBH₄/ iPr₂NH and after the distillation of alcoholic solvent.

[043] In an aspect, the present invention provides a process with cheaper materials, moderate reaction conditions and high yield of sodium formate. [044] In another aspect, the present invention provides a process for reduction of calcium carbonate wherein Aeroxide P-90 Ti0₂ catalyst loading is in the range of 0.17 to 0.29 (w/v %); sodium nitrite (reducing agent) concentration is in the range of 4.3 g/1 to 15.7 g/1; temperature is in the range of 70 to 100 °C and pH is in the range of 5.7 to 10.2.

[045] In yet another aspect, the present invention provides a process for reduction of pure carbon dioxide gas with Aeroxide P-90 Ti0₂ catalyst loading of 0.26 g/l(w/v %); sodium nitrite (reducing agent) concentration of 12.9g/l at 90 °C. EXAMPLES

[046] The following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

EXPERIMENTAL PROCEDURE

[047] The reduction of alkaline metal salts was performed in jacketed three neck glass reactor. Three necks were used for connecting glass condenser having length 0.6 m, inserting the temperature indicator and deep tube for taking sample with regular interval of time respectively. The temperature of reaction was controlled by circulated hot oil in the jacket via Julabo heater. Initially known qualities of source C0₂ [i.e. CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃)], reducing agent [i.e. NaN0₃, LiAH₄, hydrazine hydrate, absorbic acid, NaBH₄] and metal oxide catalyst [i.e. Ti0₂, ZnO, CuO, metal-doped-Ti0₂, Zr0₂] in water were added into the reactor. The reaction solution was stirred at 650 rpm and subsequently solution was heated at desired temperature & atmospheric pressure for 6 hrs. When the desired reaction temperature was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube and analysed by HPLC.

ANALYTICAL PROCEDURE [048] The concentration of sodium formate in the samples was monitored by high performance liquid chromatography (Dionex P680 HPLC) fitted with a UV detector (Dionex UVD 170U) and a C-18 column (BISCHOFF, 0-8-35μπι particle size, 250x4.6 mm, and silica gel with CI 8 coating). The mobile phase was composed by: 0.004 M H₂SO₄. Sodium formate was detected at maximum UV absorbance set at wavelengths of 215 nm. Flow rate of mobile phase was 0.6 ml/min. Column temperature was 30°C. In order to remove the catalyst, samples were centrifuged and filtered with a polyethersulfone membrane filter of 0.45μηι before the HPLC analysis. A HPLC system with an auto sampler was used for the analysis. It is interfaced with the personal computer by chromeleon (version 6.8 sp2) solutions data handling system. The data was recorded using chromeleon version 6.8 sp2 solutions software. With the optimized chromatographic conditions, a steady baseline was recorded. The retention time of sodium formate (HCOONa) was found to be 5.0 min. A typical chromatogram of sodium formate is given in Fig. 5.

EXAMPLE 1

[049] The reduction of ammonium carbonate was performed using sodium borohydride as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P-90 Ti0₂; CuO, ZnO, and Cu as catalyst. Initially known quantities of ammonium carbonate (10 g/1), reducing agent sodium borohydride (10 g/1) and metal oxide catalyst (0.23 w/v%) were added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C and atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 1 shows the amount of sodium formate formed during the reduction reaction. [050] Table 1 : Amount of sodium formate formed during the reduction of ammonium carbonate using sodium borohydride as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 2

[051] The reduction of ammonium carbonate was performed using sodium nitrite as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P-90 Ti0₂; Aeroxide P-25 T1O₂, CuO and ZnO as catalyst. Initially known quantities of ammonium carbonate (10 g/1), reducing agent sodium nitrite (10 g/1) and metal oxide catalyst (0.23 w/v%) were added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 2 shows the amount of sodium formate formed during the reduction reaction.

[052] Table 2: Amount of sodium formate formed during the reduction of ammonium carbonate using sodium nitrite as reducing agent in the presence of various metal oxide catalyst. Time(hr)

Without Aeroxide P- Aeroxide P-

CuO ZnO catalyst 25 T1O2 90 T1O2

HCOONa cone, (mg/1)

0 554.33 428.26 505.33 228.12 193.67

1 699.76 465.45 661.62 348.8 286.59

2 835.79 656.45 789.78 152.69 387.09

3 954.71 924.41 1063.55 114.21 438.22

4 961.02 1058.32 1363.58 160.45 1113.11

5 1040.33 1448.33 1530.67 189.23 1339.56

6 1234.44 1670.64 1798.42 295.22 1637.97

% yield

of 18.29 24.76 26.65 5.85 24.27

HCOONa

EXAMPLE 3

[053] The reduction of calcium carbonate was performed using sodium borohydride as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P- 90 T1O₂; Aeroxide P-25 Ti0₂, CuO, ZnO and Cu as catalyst. Initially known quantities of calcium carbonate (10 g/1), reducing agent sodium borohydride (10 g/1) and metal oxide catalyst (0.23 w/v%) were added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 3 shows the amount of sodium formate formed during the reduction reaction.

[054] Table 3: Amount of sodium formate formed during the reduction of calcium carbonate using sodium borohydride as reducing agent in the presence of various metal oxide catalyst.

HCOONa cone, (mg/1)

1435.6

0 26.31 978.03 1298.47 23.31 73.86 9

1078.2 1607.6

1 46.2 2 1382.61 46.21 198.13 1

181.9 1600.3

2 137.71 1130.9 1392.98 6 210.61 1

137.7 1667.3

3 181.96 1181.4 1390.82 1 217.11 2

201.5 1689.6

4 222.41 1306.6 1434.78 5 220.15 1

1367.6 222.4 1771.0

5 477.54 3 1454.57 1 278.06 4

1598.5 767.8 1776.2

6 788.9 9 1521.14 2 550.41 4

%

yiel

d of

12.18 24.69 23.49 11.85 8.50 27.43

HC

00

Na

EXAMPLE 4

[055] The reduction of calcium carbonate was performed using sodium nitrite as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P-90 Ti0₂; Aeroxide P-25 Ti0₂, CuO, ZnO, and Cu as catalyst. Initially known quantities of calcium carbonate (10 g/1), reducing agent sodium nitrite (10 g/1) and metal oxide catalyst (0.23 w/v%) added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 4 shows the amount of sodium formate formed during the reduction reaction. The motive of present invention is to enhance the yield of sodium formate by reduction of alkai metal salt using reducing agent in presence of metal oxide catalyst. Table 4 also shows that the yield of sodium formate in the presence of Aeroxide P-90 Ti0₂ after 6 hrs is about 79.32 whereas in the absence of Aeroxide P-90 Ti0₂ the yield is 45.59%. [056] Table 4: Amount of sodium formate formed during the reduction of calcium carbonate using sodium nitrite as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 5

[057] The reduction of sodium bicarbonate was performed using sodium borohydride as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P- 90 Ti0₂; CuO and ZnO as catalyst. Initially known quantities of sodium bicarbonate (10 g/1), reducing agent sodium borohydride (10 g/1) and metal oxide catalyst (0.23 w/v%) added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 5 shows the amount of sodium formate formed during the reduction reaction.

[058] Table 5: Amount of sodium formate formed during the reduction of sodium bicarbonate using sodium borohydride as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 6

[059] The reduction of sodium bicarbonate was performed using sodium nitrite as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P-90 Ti0₂; CuO and ZnO as catalyst. Initially known quantities of sodium bicarbonate (10 g/1) reducing agent sodium nitrite (10 g/1) and metal oxide catalyst (0.23 w/v%) added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 °C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 °C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 6 shows the amount of sodium formate formed during the reduction reaction.

[060] Table 6: Amount of sodium formate formed during the reduction of sodium bicarbonate using sodium nitrite as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 7

[061] The reduction of sodium carbonate was performed using sodium borohydride as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P- 90 Ti0₂; CuO and ZnO as catalyst. Initially known quantities of sodium carbonate (10 g/1) reducing agent sodium borohydride (10 g/1) and metal oxide catalyst (0.23 w/v%) added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 °C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 °C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 6 shows the amount of sodium formate formed during the reduction reaction.

[062] Table 7: Amount of sodium formate formed during the reduction of sodium carbonate using sodium borohydride as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 8

[063] The reduction of sodium carbonate was performed using sodium nitrite as reducing agent in the presence of various metal oxide catalyst such as Aeroxide P-90 Ti02; CuO and ZnO as catalyst. Initially known quantities of sodium carbonate (10 g/1), reducing agent sodium nitrite (10 g/1) and metal oxide catalyst (0.23 w/v%) added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 °C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 °C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 8 shows the amount of sodium formate formed during the reduction reaction. [064] Table 8: Amount of sodium formate formed during the reduction of sodium carbonate using sodium nitrite as reducing agent in the presence of various metal oxide catalyst.

EXAMPLE 9

Effect of catalyst loading on reduction of calcium carbonate

[065] The effect of catalyst loading (Aeroxide P-90 Ti0₂ as catalyst) on reduction of calcium carbonate was studied using sodium nitrite as reducing agent. The Aeroxide P- 90 Ti0₂ catalyst loading was varied from 0.17 to 0.29 (w/v%) in order to find its effect on reduction of calcium carbonate. Initially known quantities of calcium carbonate (10 g/1), reducing agent sodium nitrite (12.9 g/1) was added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 9 shows the amount of sodium formate formed during the reduction reaction.

[066] Table 9: Effect of catalyst loading on formation of sodium formate formed during the reduction of calcium carbonate using sodium nitrite as reducing agent

EXAMPLE 10

Effect of reducing agent concentration on reduction of calcium carbonate

[067] The effect of reducing agent (sodium nitrite) on reduction of calcium carbonate was studied using Aeroxide P-90 T1O₂ catalyst. The sodium nitrite concentration was varied from 4.3 g/1 to 15.7 g/1 in order to find its effect on reduction of calcium carbonate. Initially known quantities of calcium carbonate (10 g/1), Aeroxide P-90 T1O₂ catalyst (0.26 w/v%) was added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 9 shows the amount of sodium formate formed during the reduction reaction.

[068] Table 10: Effect of the effect of reducing agent (sodium nitrite) on formation of sodium formate formed during the reduction of calcium carbonate using Aeroxide P-90 T1O₂ catalyst Time(hr)

HCOONa cone, (mg/1)

Sodium nitrite Sodium Sodium nitrite Sodium nitrite 4.3 g/1 nitrite 10 g/1 12.9 g/1 15.7 g/1

0 1076.43 1502.05 2356.22 2559.33

1 1172.68 1899.45 2673.56 2450.21

2 1596.31 2258.12 3056.45 3121.96

3 1602.98 2540.12 4780.64 4338.09

4 1529.98 2904.42 5521.53 5175.17

5 1550.91 3691.56 6045.63 5522.07

6 1983.35 5135.95 6375.04 6240.23

% yield

of 30.63 79.32 98.46 68.38

HCOONa

EXAMPLE 11

Effect of temperature on reduction of calcium carbonate

[069] The effect of reaction temperature on reduction of calcium carbonate was studied using Aeroxide P-90 Ti0₂ catalyst and sodium nitrite as reducing agent. The reaction temperature was varied from 70 to 100 °C in order to find its effect on reduction of calcium carbonate. Initially known quantities of calcium carbonate (10 g/1), sodium nitrite (12.9 g/1) and Aeroxide P-90 Ti0₂ catalyst (0.26 w/v%) was added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 9 shows the amount of sodium formate formed during the reduction reaction.

[070] Table 11 : Effect of the reaction temperature on formation of sodium formate formed during the reduction of calcium carbonate using Aeroxide P-90 Ti0₂ catalyst

°C °C °C 100 °C

0 2436.78 2569.23 2356.22 2546.23

1 2647.55 2653.21 2673.56 2745.22

2 3214.33 3546.23 3056.45 3152.56

3 3689.27 4677.67 4780.64 4256.23

4 4176.75 5425.42 5521.53 5456.62

5 5319.46 5862.3 6045.63 5548.56

6 5616.28 6082.42 6375.04 6254.78

% yield

of 86.74 93.94 98.46 96.60

HCOONa

EXAMPLE 12

Effect of pH on reduction of calcium carbonate

[071] The effect of solution pH on reduction of calcium carbonate was studied using Aeroxide P-90 Ti0₂ catalyst and sodium nitrite as reducing agent. The pH of solution was varied from 5.7 to 10.2 in order to find its effect on reduction of calcium carbonate. Initially known quantities of calcium carbonate (10 g/1), sodium nitrite (12.9 g/1) and Aeroxide P-90 Ti0₂ catalyst (0.26 w/v%) was added into the water (350 ml). The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 12 shows the amount of sodium formate formed during the reduction reaction.

[072] Table 12: Effect of the solution pH on formation of sodium formate formed during the reduction of calcium carbonate using Aeroxide P-90 Ti0₂ catalyst

3

5018.3

3 4142.23 4325.56 4

5877.9

4 4853.66 4966.21 4

6141.3

5 5233.55 5621.22 3

6408.9

6 5642.33 6023.12 2

% yield of

87.14 93.02 98.98

HCOONa

EXAMPLE 13

Reduction of pure C0₂ using Aeroxide P 90 Ti0₂ catalyst and sodium nitrite as reducing agent

[073] The reduction of C0₂ was performed using sodium nitrite as reducing agent in the presence of Aeroxide P-90 Ti0₂ catalyst. Initially known quantities of reducing agent sodium nitrite (12.9 g/1) and Aeroxide P-90 Ti0₂ catalyst (0.26 %w/v) added into the water (350 ml). Then known quantity of C0₂ gas was taken in the high pressure reactor. The reaction solution was stirred at 650 rpm and subsequently solution was heated at 90 °C & atmospheric pressure for 6 hrs. When the desired reaction temperature (90 °C) was reached, then it was considered as the zero reaction time and sample was withdrawn through the sample tube as a zero time sample. Subsequently samples were withdrawn at specific time intervals through the sample tube. Table 13 shows the amount of sodium formate formed during the reduction reaction.

[074] Table 13: Reduction of pure C0₂ using Aeroxide P-90 Ti0₂ catalyst and sodium nitrite as reducing agent

EXAMPLE 14

General experimental procedure for the preparation formic acid

[075] To a stirred solution of absolute ethanol added COCl₂ (lmol %)/NaB¾ (1 equiv.) at 0°C, black color solution was formed then added diisopropyl amine (20 mol%) and stirred for 10 min then passed carbon dioxide gas into the reaction mass, and heated to 80 °C for overnight (24 hr). After completion of reaction ethanol was distilled out, then the reaction was quenched with 5 % HC1 solution, and aqueous layer was washed with 20 ml of diethyl ether which was then washed with concentrated brine solution and filtered. Then the residue obtained was also washed as above mentioned way. The analysis of formic acid was done by using GC-MS (Fig 1 to 4). The results of authentic sample formic acid and formic acid formed during the reaction are given below. Table 14 shows the optimization of CoCl₂/diisopropyl amine catalyzed reduction of C0₂ to formic acid using NaBH₄.

Fomic acid (authentic) : - HCOOH

[076] RT-6.17 mm; MS m/z 47 (M+l), 46 (HCOOH), 45 (HCOO), 29 (HCO), 28 (CO);

Formic acid (from reduction of C0₂)

[077] Colorless liquid; GCMS Analysis: RT- 6.28 mm; MS m/z- 47 (M+l), 46 (HCOOH), 45 (HCOO), 29 (HCO).

[078] Table 14: Optimization of CoCl₂/diisopropyl amine catalyzed reduction of C0₂ to formic acid using NaBH₄:

[079] ^a20 mol% of secondary and tertiary amines were used as an additive. l equiv. of NaBH₄ used as reductant. ^cl mol% of CoCl₂ used as catalyst. ^d HCOOH has been converted as benzyl formate to calculate its yield. ^ePresence of HCOOH was confirmed by GC-MS analysis, nd-not determined.

EXAMPLE 15 General experimental procedure for conversion of formic acid to benzyl formate

[080] To a stirred solution of absolute ethanol added CoCl₂ (lmol %) NaBH₄ (1 equiv.) at 0°C black color solution was formed then added diisopropyl amine (20 mol%) and stirred for 10 min then passed carbon dioxide gas into reaction mass, and heated to 80 °C for overnight (24 hr). After completion of reaction ethanol was distilled out, into that added THF 20 ml and added benzyl bromide then heated the reaction mixture for overnight (24 hr). After completion of reaction (monitored by TLC), it was quenched with water and extracted with EtOAc (3 x 50 mL). The combined organic layers were washed with brine, dried over anhyd. Na₂S0₄, filtered and concentrated under reduced pressure to give the crude ester, column chromatographic purification [silica gel (230-400 mesh) and pet ether:EtOAc (99: 1) as an eluent given the pure benzyl formate.

[081] Benzyl formate

Yield: 32% colorless liquid; 1H NMR (200 MHz, CDC1₃): δ 5.18(s, 2H), 7.34 (s, 5H), 8.11 (br s, 1H); ¹³C NMR (200 MHz, CDC1₃): δ 65.67, 77.10 , 96.25, 128.47, 135.32, 160.57; Analysis: C₈H₈0₂ requires C, 70.58; H, 5.92, 0,23.50; C, 70.3; H, 6.1, 0,23.62.

ADVANTAGES OF THE INVENTION

[082] Present invention provide a one step process for the synthesis

of formic acid or sodium formate from C0₂ or carbonate salt in the presence reducing agent using catalyst or without catalyst at moderate reaction conditions.

[083] Present invention provide a viable process for conversion of C0₂ or carbonate salt into sodium formate using cheaper raw materials.

[084] The present process gives maximum yield (98.98%) of sodium formate.

Claims

We claim

1. A one step, one pot metal catalyzed process for the synthesis of HCOOR wherein R is selected from H or Na comprising the step of:

a. reacting the C0₂ source at a temperature in the range of 50-90°C for period in the range of 6-24 hours at atmospheric pressure in the presence of a reducing agent, a catalyst, a polar solvent and optionally a base to obtain HCOOR wherein R is selected from H or Na.

2. The process as claimed in claim 1 , wherein yield of HCCOR is in the range of 0.90 to 98.98%.

3. The process as claimed in claim 1 , wherein the reducing agent used is selected from the group consisting of NaN0₃, LiAH₄, hydrazine hydrate, absorbic acid, NaBH₄.

4. The process as claimed in claim 1, wherein the catalyst used is selected from the group consisting of CoCl₂,Ti0₂, ZnO, CuO, metal-doped-Ti0₂ or Zr0₂ or Cu nanoparticles.

5. The process as claimed in claim 1 , wherein the C0₂ source is selected from the group consisting of CaC0₃, Na₂C0₃, NaHC0₃, K₂C0₃, (NH₄)₂C0₃); K₂HC0₃, MgC0₃, MgHC0₃, BaC0₃, BaHC0₃, Rb₂C0₃, MnC0₃, CoC0₃, NiC0₃ direct C0₂ gas or atmoshpheric C0₂ gas.

6. The process as claimed in claim 1, wherein the polar solvent used is selected from water or ethanol.

7. The process as claimed in claim 1 , wherein the base used is diisopropyl amine.