Method for synthesizing calcium formate by direct oxidation of methanol

Abstract

This invention discloses a method for the direct oxidation of methanol to synthesize calcium formate. The method mainly involves adding a catalyst, methanol, and calcium hydroxide to a reaction vessel and then pressurizing the reaction. Under the action of the catalyst, methanol is oxidized to formic acid, which then rapidly reacts with calcium hydroxide to produce calcium formate, achieving a yield of up to 63.4%. This invention directly oxidizes methanol to synthesize calcium formate. Subsequent operations can further produce formic acid and methyl formate derivatives to increase its added value. Simultaneously, the calcium ions in the calcium formate can be effectively recycled. This invention has advantages such as readily available and simple raw materials, mild reaction conditions, convenient catalyst preparation, low production cost, and recyclability, making it highly valuable for market applications.

Description

Technical Field

[0001] This invention designs a process technology for the direct oxidation of methanol to synthesize calcium formate, and then uses calcium formate to derive formic acid and methyl formate, as well as a specific method for determining the product yield. Background Technology

[0002] Calcium formate, a commonly used organic compound in industry, is widely applied in various industrial production fields such as food, chemicals, petroleum, building materials, and leather tanning. Its most common use is as a feed additive because it reduces feed acidity and gastrointestinal pH, and increases the activity of digestive enzymes. Its acidifying effect activates pepsinogen in animals, stimulating pepsin secretion and thus improving feed digestibility. Therefore, it is used as an acidifier in the feed of young animals. In the construction industry, calcium formate is also used as a fastening agent and lubricant to accelerate cement hardening and shorten setting time. As a major producer of calcium formate in the world, my country has strict quality standards for it, primarily classifying it into feed grade and industrial grade.

[0003] Existing calcium formate production processes are mainly divided into two categories: production as a byproduct and production as a main product. The main production methods as byproducts include those involving the production of polyhydroxy alcohols and chloroform, which produce calcium formate as a byproduct. For example, patent CN104387255A proposes using semi-water gas, after dust removal, desulfurization, compression, and carbonization, to react with calcium hydroxide suspension in the presence of ammonia to generate an aqueous solution of calcium formate containing ammonium formate. Concentration and displacement yield a solid precipitate of calcium formate. This method can be used for co-production of calcium formate with ammonia synthesis systems. Patent CN101659606B proposes using formic acid-containing waste liquid generated from the hydrolysis of nitromethane in the hydroxylamine hydrochloride production process as raw material, adding calcium carbonate powder, and reacting under acidic conditions to produce calcium formate as a byproduct. Its drawbacks are the unstable yield of the byproduct, making large-scale continuous production impossible, and the simultaneous production of other difficult-to-separate byproducts, making it difficult to guarantee purity.

[0004] The main production methods for the primary product include the neutralization method of formic acid and calcium carbonate, the neutralization method of formic acid and calcium hydroxide, the wet process for phosphoric acid production, the carbonylation method of calcium hydroxide, and the catalytic synthesis method of calcium hydroxide and formaldehyde. For example, patent CN101880223A proposes to preheat carbon monoxide and calcium hydroxide, synthesize calcium formate reaction solution in a tubular reactor under high temperature and pressure, and then separate calcium formate by vacuum concentration and crystallization. Patent CN114874090A proposes to obtain high-purity calcium formate by adding mother liquor, light calcium formate, and high-concentration formic acid to a reaction vessel and then neutralizing them. Patent CN108558639A proposes to react carbon monoxide with a water-soluble organic base solution to obtain a formic acid organic base salt solution, react it with lime milk to obtain a calcium formate solution, and then synthesize calcium formate by indirect carbonylation of calcium hydroxide. However, the disadvantages of these methods are that they all use relatively expensive raw materials such as formic acid, formaldehyde, and sodium formate, and they do not fundamentally solve the problems of formaldehyde carbonylation and incomplete reaction.

[0005] Methyl formate, as an important intermediate in many chemicals, occupies an extremely important position in bulk chemical products and is widely used in fragrances, solvents, organic synthesis, bactericides, and pesticides. Industrially, methyl formate is mainly synthesized through formate esterification, methanol carbonylation, methanol dehydrogenation, and direct synthesis from syngas. For example, formate esterification involves esterification, cooling, and distillation to obtain methyl formate. This method was the earliest production method for methyl formate, but it suffers from fundamental problems such as high production costs and high corrosivity. Methanol carbonylation uses metal carbonyl compounds as catalysts to react methanol and carbon monoxide to produce methyl formate. This method has relatively low requirements for carbon monoxide purity, but the methanol conversion rate is also relatively low. Methanol oxidative dehydrogenation can be carried out in both liquid and gas phases and is an irreversible reaction. However, this process also involves a competing reaction to formaldehyde, resulting in low selectivity for methyl formate production. The direct synthesis of syngas requires a liquid-phase metal catalyst containing precious metals, and the conversion rate of syngas can reach 50%, but the reaction conditions are more stringent and the production cost is high.

[0006] To address the problems of high production costs, low efficiency in large-scale production, and low product purity in existing calcium formate, formic acid, and methyl formate production processes, a new technology is proposed: direct oxidation of methanol to synthesize calcium formate, followed by the preparation of formic acid and methyl formate from calcium formate. Using readily available methanol as a raw material significantly reduces production costs, and the direct reaction utilizes simple and readily available raw materials, ensuring a safe and efficient reaction process. The prepared calcium formate is then further processed to yield formic acid under acidic conditions, or formic acid can be further reacted with methanol to produce the downstream product methyl formate. Furthermore, the calcium ions in the calcium formate can be collected by drying, replaced with sodium hydroxide solution, and then used to obtain the desired calcium hydroxide solid as a raw material, achieving effective calcium ion recycling. Summary of the Invention

[0007] To address the problems of high production costs, low efficiency in large-scale production, and low product purity in existing industrial production of calcium formate, formic acid, and methyl formate, this invention designs a process technology for the direct oxidation of methanol to synthesize calcium formate, and then for the derivatization of calcium formate to prepare formic acid and methyl formate, along with a specific method for determining the product yield, which can achieve effective recycling of calcium ions in the reaction system.

[0008] The main innovation of this invention lies in the direct oxidation of methanol to synthesize calcium formate. Subsequent processes can further yield formic acid and methyl formate derivatives, increasing their added value. This invention primarily involves adding a catalyst, methanol, and calcium hydroxide to a reactor and then pressurizing the reaction. Under the action of the catalyst, methanol is oxidized to formic acid, which then rapidly reacts with calcium hydroxide to produce calcium formate.

[0009] The technical solution of the present invention is as follows:

[0010] A method for the direct oxidation of methanol to synthesize calcium formate includes the following steps:

[0011] Methanol, Ca(OH)2, and catalyst were added to a high-pressure reactor, and air was introduced into the reactor. The temperature was raised to 120-200 °C and the mixture was stirred for 1-5 h. After cooling to room temperature, the reaction mixture was distilled under reduced pressure to dryness. The resulting solid was dissolved in water, and the insoluble substances were removed by filtration. The filtrate was distilled under reduced pressure to dryness to obtain the product calcium formate.

[0012] The preferred feeding ratio of methanol, Ca(OH)2, and catalyst is 10-50 mL: 0.1-1.0 g: 0.05-1.0 g, with a particularly preferred ratio of 20 mL: 0.4 g: 0.1 g.

[0013] It is preferable to purge the high-pressure reactor with air to 1-5 MPa to provide sufficient oxygen for the oxidation reaction of methanol;

[0014] The preferred reaction temperature is 180 °C, the actual reaction pressure is approximately 4.5 MPa, and the reaction time is 4 h.

[0015] The preferred temperature for vacuum distillation is 80 ~ 150 ℃;

[0016] In the above synthesis method, the catalyst is a Cu / SiO2 catalyst or a Cu-M / SiO2 catalyst prepared by the ammonia stripping method;

[0017] The Cu loading in the Cu / SiO2 catalyst is preferably 15-25 wt.%, more preferably 22-25 wt.%, and particularly preferably 24 wt.%.

[0018] The Cu-M / SiO2 catalyst preferably has a Cu loading of 10 wt.% and an M loading of 5 wt.%; M represents metals such as Mn, Mo, Bi, V, Zr, Ag, Ce, Al or La, preferably Mo, Bi, Zr, Ce, Al or La, and more preferably Mo or Al.

[0019] The product calcium formate obtained by this invention can be replaced with formic acid under acidic conditions. The formic acid further reacts with methanol to obtain methyl formate, a downstream product of formic acid, and calcium hydroxide, a byproduct that can be recycled. The specific steps include the following:

[0020] (1) Weigh the calcium formate solid obtained by the above synthesis method. Take 20 g of calcium formate sample as an example, put it into a 100 mL flask, add excess 30 mL of hydrochloric acid, stir for 15 min, and replace the formic acid in calcium formate by strong acid replacing weak acid.

[0021] (2) Add 36 mL of excess methanol to the above solution and react with formic acid at 80 °C for 6 h to produce methyl formate.

[0022] (3) By stepwise heating, the products with different boiling points in the liquid phase are collected by distillation. The temperature is raised to 35 °C and the methyl formate liquid is collected by distillation until there is no boiling or bubbling in the flask and no distillate flows out of the distillation port.

[0023] (4) The above solution is heated to 90 °C, and excess methanol is collected by distillation and can be reused as raw material;

[0024] (5) Remove the distillation apparatus, open the flask and heat it to 120 °C to evaporate the excess hydrogen chloride gas and water vapor in the reaction, and collect the solid product calcium chloride;

[0025] (6) Dissolve the calcium chloride solid collected in the above steps in a high concentration of excess sodium hydroxide solution. After the reaction is complete, a milky white calcium hydroxide suspension is formed. The by-product calcium hydroxide solid is collected by filtration and can be reused as a raw material.

[0026] This invention collects the obtained calcium formate solid product and then reacts it through subsequent steps to generate downstream derivatives including formic acid and methyl formate, thereby further increasing its economic added value. According to the above method, the yield of methyl formate in the final liquid product obtained from the continuous reaction of methanol and calcium hydroxide can reach 49.47%, while the recycling yield of calcium ions can reach 94.76%.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention presents a technology for the direct oxidation of methanol to synthesize calcium formate. The main process involves adding a catalyst, methanol, calcium hydroxide, and other raw materials to a reaction vessel and then pressurizing the reaction. Under the action of the catalyst, methanol is oxidized to formic acid and then rapidly reacts with calcium hydroxide to produce calcium formate, with a yield of up to 63.4%.

[0029] The calcium formate prepared by this invention can be further processed to obtain formic acid under acidic conditions, or the formic acid can be further reacted with the raw material methanol to obtain the downstream product methyl formate. The calcium ions in the calcium formate can be collected by drying, replaced with sodium hydroxide solution, and then used to obtain the required solid calcium hydroxide as a raw material, thus achieving effective recycling of calcium ions.

[0030] Compared with other production methods, this invention has advantages such as simple and readily available raw materials, mild reaction conditions, convenient catalyst preparation, low production cost, and recyclability, and has high market application value. Detailed Implementation

[0031] The present invention will be further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] In the following examples, the preparation method of the 24wt.% Cu-SiO2 catalyst is as follows:

[0033] (1) Weigh 1.825 g of Cu(NO3)2·3H2O solid, put it into a 100 mL beaker and add 40 mL of deionized water, stir and dissolve for 3 h.

[0034] (2) Add 2.0 g of gaseous SiO2 to the above solution, then add 20 mL of deionized water and stir for 12 h to fully dissolve and disperse it.

[0035] (3) Add an appropriate amount of ammonia water to the solution until the pH is 12, and stir thoroughly to form a copper-ammonium complex.

[0036] (4) Place the above solution in a 90 ℃ oil bath, heat and stir until all liquid is evaporated, and put the solid in an oven to dry at 100 ℃ for 4 h.

[0037] (5) After drying, the solid is ground and pulverized and then placed in a muffle furnace at 450 °C for 4 h. After grinding again, the catalyst required for the final reaction is obtained.

[0038] The method for preparing Cu / SiO2 catalysts with different Cu loadings is the same as described above; only the amount of Cu(NO3)2·3H2O solid needs to be changed.

[0039] Taking a 10wt.%Cu-5wt.%Al / SiO2 catalyst as an example, the preparation method of a 10wt.%Cu-5wt.%M / SiO2 catalyst is as follows:

[0040] (1) Weigh 0.760 g Cu(NO3)2·3H2O solid and 1.3903 g Al(NO)3·9H2O solid, put them into a 100 mL beaker and add 40 mL of deionized water, stir and dissolve for 3 h.

[0041] (2) Add 2.0 g of gaseous SiO2 to the above solution, then add 20 mL of deionized water and stir for 12 h to fully dissolve and disperse it.

[0042] (3) Add an appropriate amount of ammonia water to the solution until the pH is 12, and stir thoroughly to form a copper-aluminum-ammonium complex.

[0043] (4) Place the above solution in a 90 ℃ oil bath, heat and stir until all liquid is evaporated, and put the solid in an oven to dry at 100 ℃ for 4 h.

[0044] (5) After drying, the solid is ground and pulverized and then placed in a muffle furnace at 450 °C for 4 h. After grinding again, the catalyst required for the final reaction is obtained.

[0045] The method for preparing 10wt.%Cu-5wt.%M / SiO2 catalysts with different metal M loadings is the same as described above, only requiring changes to the amount of nitrate solids corresponding to different metal M.

[0046] Example 1

[0047] This embodiment proposes a process technology for the direct oxidation of methanol to synthesize calcium formate, and the specific steps are as follows:

[0048] (1) Use a 50 mL high-pressure reactor as the reaction vessel, add 20 mL of raw material methanol liquid, 0.4 g Ca(OH)2 powder, and 0.1 g 24wt.% Cu-SiO2 catalyst.

[0049] (2) Purge 2.0 MPa of air into the high-pressure reactor to provide sufficient oxygen for the oxidation reaction of methanol.

[0050] (3) The internal temperature of the reactor is raised to 180 °C, and the reaction is carried out under this condition by stirring for 4 h.

[0051] (4) After the reaction is complete, allow the reactor to cool to room temperature and vent the gas inside the reactor through the exhaust port. Collect the solid and liquid products from the reactor after the reaction is complete into a 500 mL flask. When collecting the solid products, some solid products that are insoluble in methanol will adhere to the inner wall of the reactor. These products need to be repeatedly rinsed with deionized water to dissolve them and all solid products in the reactor should be collected.

[0052] (5) Distill the product collected in the flask under reduced pressure at 120 °C to distill off all the liquid phase products.

[0053] (6) Add 200 mL of deionized water to the solid product in the flask, heat and stir to dissolve it completely in the deionized water, filter out the insoluble solid product with filter paper, collect the solution into a volumetric flask and make up to 250 mL.

[0054] (7) Distill the solution in the volumetric flask under reduced pressure at 120 °C, distill off the liquid phase, collect the solid product, dry the product to remove excess water, and obtain calcium formate with a purity >99%.

[0055] Example 1 was titrated using the potassium permanganate-potassium iodide titration method. The final measured consumption of sodium thiosulfate solution was 69.9 mL, and the yield of calcium formate was calculated to be 63.4%.

[0056] The yield of the reaction product, calcium formate, can be determined during the reaction process using a potassium permanganate-potassium iodide titration method. According to a reported method for determining calcium formate content, patent CN112684074A proposes that after ultrasonic extraction of the calcium formate solution, the peak area of ​​each standard sample is measured using high-performance liquid chromatography (HPLC), and a linear regression equation is calculated using the peak area of ​​the standard samples. Finally, the peak area of ​​the calcium formate solution to be tested is substituted into this equation to calculate its calcium formate content. According to the People's Republic of China Chemical Industry Standard HG / T 5614—2019 "Industrial Calcium Formate," the potassium permanganate-potassium iodide titration method is used to determine the mass of industrial-grade calcium formate. Therefore, considering the above methods comprehensively, we used the titration amount of industrial-grade calcium formate of different concentrations as the ordinate and fitted a standard curve.

[0057] The method of the present invention for determining the specific yield of calcium formate is a potassium permanganate-potassium iodide titration method, which includes the following steps:

[0058] (1) Use the 250 mL calcium formate solution in the above operation step (6) as the test solution for titrating the yield of the final product.

[0059] (2) Take 25 mL of the solution to be tested into an iodine flask, add 0.2 g of anhydrous sodium carbonate to make the solution slightly alkaline.

[0060] (3) Add an excess of potassium permanganate standard solution and heat in an oil bath at 80 °C for 30 min. The excess potassium permanganate standard solution ensures that the oxidation reaction is completed quantitatively after heating.

[0061] The excess potassium permanganate solution is a 50 mL standard solution with a concentration of C(1 / 5 KMnO4) = 0.1 mol / L.

[0062] (4) Filter the solution in (3) using a conical funnel, wash the excess solid on the filter paper with deionized water several times, and rinse all the residual potassium permanganate solution on the filter paper into the collection beaker until the filtered liquid is colorless.

[0063] (5) Add 6 mL of sulfuric acid solution and 2 g of potassium iodide, stir well and place in the dark for 5 min, so that potassium iodide reacts with excess unreacted potassium permanganate in the acidic solution and releases iodine.

[0064] The 6 mL sulfuric acid solution is 10% sulfuric acid.

[0065] (6) Titrate free iodine with sodium thiosulfate standard solution. Near the endpoint, add 3 mL of starch indicator (0.5%) to react with the free iodine to produce a color reaction. Continue titrating until the solution becomes colorless. Calculate the yield of calcium formate based on the actual titration volume of sodium thiosulfate solution.

[0066] The sodium thiosulfate solution is a 100 mL standard solution with a concentration of C(Na2S2O3) = 0.1 mol / L.

[0067] The potassium permanganate-potassium iodide titration method of this invention requires titration with calcium formate standard solutions of different concentrations and fitting of a standard curve for the calculation of actual calcium formate solution yield.

[0068] The potassium permanganate-potassium iodide titration method is a measurement method proposed by national standards. It uses an industrial-grade standard calcium formate sample to determine and fit a standard curve. The actual titration amount of the sodium thiosulfate standard solution measured in the sample is then mapped to the aforementioned standard curve to determine the actual calcium formate content in the sample. The specific calculation method for the standard curve is shown in the following formula:

[0069]

[0070] The meanings of the parameters in the formula are as follows:

[0071] X – Calcium formate content (%); V1 – Volume of sodium thiosulfate standard solution consumed in the blank experiment (mL); V2 – Volume of sodium thiosulfate standard solution consumed in the titration of the sample (mL); C – Concentration of sodium thiosulfate standard solution (mol / L); 0.03253 – Mass of calcium formate in grams equivalent to 1.00 mL of sodium thiosulfate standard solution; m – Mass of standard calcium formate sample (g).

[0072] The formula for the fitting curve of the standard sample is shown below:

[0073]

[0074] The meanings of the parameters in the formula are as follows: Y—volume of sodium thiosulfate standard solution consumed by the sample in mL; X—actual mass of calcium formate in the sample in g.

[0075] The potassium permanganate-potassium iodide titration method of the present invention involves titrating the calcium formate solution of the concentration to be tested on a fitted standard curve to obtain the actual mass of the calcium formate to be tested, and calculating the yield of the calcium formate sample by comparing it with the theoretically producible mass of calcium formate solids from a fixed amount of raw material.

[0076] Comparative Example 1

[0077] This comparative example is basically the same as Example 1, except that:

[0078] In step (1), the 0.1 g 24 wt.% Cu-SiO2 catalyst was replaced with 0.1 g Cu / SiO2 catalyst with different Cu loadings of 10-30 wt.%. The specific titration values ​​of sodium thiosulfate solution and the yield of calcium formate are shown in the table below:

[0079]

[0080] Comparative Example 2

[0081] This comparative example is basically the same as Example 1, except that:

[0082] In step (1), the 0.1 g 24wt.% Cu-SiO2 catalyst was replaced with 0.1 g 10wt.% Cu-5wt.% M / SiO2 catalyst (M = Mn, Mo, Bi, V, Zr, Ag, Ce, Al, La). The specific titration values ​​of the sodium thiosulfate solution and the yield of calcium formate are shown in the table below:

[0083]

Claims

1. A method for the direct oxidation of methanol to synthesize calcium formate, characterized in that, Includes the following steps: Methanol, Ca(OH)2, and catalyst were added to a high-pressure reactor, and air was introduced into the reactor. The temperature was raised to 120-200 °C and the mixture was stirred for 1-5 h. After cooling to room temperature, the reaction mixture was distilled under reduced pressure to dryness. The resulting solid was dissolved in water, and the insoluble substances were removed by filtration. The filtrate was distilled under reduced pressure to dryness to obtain the product calcium formate. The catalyst is a Cu / SiO2 catalyst or a Cu-M / SiO2 catalyst prepared by ammonia stripping; where M represents metal Mn, Mo, Bi, Zr, Ce, Al or La.

2. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 1, characterized in that, The feeding ratio of methanol, Ca(OH)2, and catalyst is 10 ~ 50 mL: 0.1 ~ 1.0 g: 0.05 ~ 1.0 g.

3. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 1, characterized in that, Air is introduced into the high-pressure reactor to a pressure of 1-5 MPa.

4. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 1, characterized in that, The temperature for vacuum distillation is 80 ~ 150 ℃.

5. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 1, characterized in that, The Cu loading in the Cu / SiO2 catalyst is 15 ~ 25 wt.%.

6. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 5, characterized in that, The Cu loading in the Cu / SiO2 catalyst is 22 ~ 25 wt.%.

7. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 1, characterized in that, In the Cu-M / SiO2 catalyst, the Cu loading is 10 wt.% and the M loading is 5 wt.%.

8. The method for direct oxidation of methanol to synthesize calcium formate as described in claim 7, characterized in that, In Cu-M / SiO2 catalysts, M represents the metals Mo, Bi, Zr, Ce, Al, or La.

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