Formic acid is a kind of organic matter, chemical formula HCOOH, molecular weight 46.03, common name formic acid, is the simplest carboxylic acid. It is a colorless and pungent liquid. is a weak electrolyte, but its aqueous solution is weakly acidic and corrosive, and can stimulate skin blistering. It is commonly found in the secretions of bees, certain ants, and caterpillars. It is an organic chemical raw material and is also used as a disinfectant and preservative.
formic acid Brief history of research
Formic acid was first produced by J. L. Gay-Lussac from the decomposition of oxalic acid. 1855-1856, M. Berthelot directly prepared sodium formate from sodium hydroxide and carbon monoxide, T. Goldschmidt was the first to produce formic acid from sodium formate by hydrolysis. This method began to be used for industrial production in Europe in 1896, and it is still used for small batch production today. In 1980, American Scientific Design Company, Bethlehem Steel Company and Leonard Company successfully developed methanol carbonylation to produce formic acid method, and has an annual output of 20 thousand tons of formic acid plant put into operation. In addition, formic acid can also be recovered from the by-product of the oxidation of light oil to acetic acid.
Formic acid Physical and chemical properties
1.Physical property
In hydrocarbons and gaseous states, occurs as dimers bonded by hydrogen bonds. In gaseous state, hydrogen bonding results in a large deviation between formic acid gas and ideal gas equation of state. Liquid and solid formic acid consists of continuous formic acid molecules bonded by hydrogen bonds. Because of the special structure of formic acid, one of its hydrogen atoms is directly connected to the carboxyl group. Or you could view it as a hydroxyformaldehyde.
2.Chemical property
1.Acidity of formic acid
Formic acid is the only acid in the carboxyl group connected to the hydrogen atom, the hydrogen atom repulsive electron force is much smaller than the hydrocarbon group, so that the carboxyl carbon atom electron density is lower than other carboxyl acids, and because of the conjugation effect, the carboxyl oxygen atom on the electron is more inclined to carbon, so the acid is stronger than other carboxyl acids in the same series. has the same properties as most other carboxylic acids in that it does not normally form an acyl chloride or anhydride. in aqueous solution is a simple weak acid, acidity coefficient (pKa)=3.75(at 20℃), 1% formic acid solution pH value is 2.2.
The following are the properties of formic acid:
Reaction with base
has the properties of acid, so it can be neutralized with alkali to form formates and water.
reacts with ammonia: HCOOH+NH3·H2O = =HCOONH4+H2O
and sodium hydroxide: HCOOH+NaOH = HCOONa+H2O
and copper hydroxide: 2HCOOH+Cu(OH)2 = Cu(HCOO)2+2H2O
and calcium hydroxide: 2HCOOH+Ca(OH)2 = Ca(HCOO)2+2H2O
React with salt
can also react with some salts.
and sodium carbonate: 2HCOOH+Na2CO3 = 2HCOONa+H2O+CO2↑
and calcium carbonate: 2HCOOH+CaCO3 = Ca(HCOO)2+H2O+CO2↑
React with metal
Due to the nature of weak acids, is corrosive to many metals, such as magnesium and zinc, which react to form hydrogen and metal-formates.
reacts with sodium: 2HCOOH+2Na = 2HCOONa+H2↑
reacts with zinc: 2HCOOH+Zn = Zn(COOH)2+H2↑
reacts with magnesium: 2HCOOH+Mg = Mg(COOH)2+H2↑
2.make potassium permanganate fade
Formic acid has a similar reducing property to aldehydes, and acid potassium permanganate has a strong oxidation property, so the two can REDOX reaction, so that the potassium permanganate solution fade.
3.Decomposition reaction
is heated and decomposed into CO and H2O under the catalysis of concentrated sulfuric acid.
4.Silver mirror reaction
is a strong reducing agent, it can initiate the silver mirror reaction, the silver ion in the silver ammonia complex ion reduction to silver metal, and itself is oxidized into carbon dioxide and water.
5.Addition reaction
is the only carboxylic acid that can be added to olefins. in the action of acids (such as sulfuric acid, hydrofluoric acid), and olefins quickly react to form formates. However, a side reaction similar to the Koch reaction can also occur, with the product being a higher carboxylic acid.
6.Esterification reaction
Formic acid and alcohols can be esterified under the action of concentrated sulfuric acid and heated. If formic acid and methanol are catalyzed by concentrated sulfuric acid and heated, esterification reaction can occur to form methyl formate.
7.Reduction reaction
Formic acid can be reduced to formaldehyde by hydrogenation under the action of catalyst.
8.Complete burning of formic acid
High purity can be completely burned in oxygen, will produce carbon dioxide and water.
Preparation method
Laboratory preparation
Oxalic acid was heated in anhydrous glycerol and then steam distilled. Or obtained by hydrolyzing isoacetonitrile with hydrochloric acid.
Industrial law
1.Sodium formate method: carbon monoxide and sodium hydroxide solution react at 160-200 ℃ and 2 MPa pressure to produce sodium formate, and then acid hydrolysis by sulfuric acid, distillation to obtain the finished product.
2.Methanol carbonyl synthesis (also known as methyl formate method) : methanol and carbon monoxide react in the presence of sodium methanol as a catalyst to form methyl formate, and then hydrolysis to form formic acid and methanol. Methanol can be recycled into the methyl formate reactor, and then the formate can be rectified to obtain products of different specifications.
3.Formamide process: carbon monoxide and ammonia react in methanol solution to form formamide, and then hydrolysis to formic acid in the presence of sulfuric acid, while producing ammonium sulfate as a by-product. Raw material consumption quota: methanol 31 kg/t, carbon monoxide 702 kg/t, ammonia 314 kg/t, sulfuric acid 1010 kg/t.
4.The industrial grade is prepared by the reaction of sodium formate and concentrated sulfuric acid, and then the pure product can be obtained by vacuum distillation after adsorption by activated carbon.
5.Carbon dioxide method: In the palladium complex catalysis, in the triethylamine aqueous solution, carbon dioxide and hydrogen reaction at 140 ~ 160 ℃.
Refining method
1.Anhydrous can be obtained by direct fractionation under reduced pressure, during which it is condensed by freezing water. For aqueous formic acid, anhydrous copper sulfate can be used as a desiccant. For 88% of the reagent grade formic acid, the water in it can be removed by distillation of phthalic anhydride after reflux for 6 hours. Further purification can be done by fractional crystallization. When formic acid and acetic acid are mixed together, they can be separated by azeotropic distillation by adding aliphatic hydrocarbons.
2.The formic acid is mixed with phosphorus pentoxide, the vacuum distillation is carried out, and the anhydrous can be obtained by repeating 5-10 times, but the amount is low and time-consuming, which will cause some decomposition. The distillation of formic acid and boric acid is simple and effective. The boric acid is dehydrated at a medium high temperature until it no longer produces bubbles, and the resulting melt is poured on the iron sheet, cooled in a dryer, and then ground into powder. The fine borate phenol powder was added to the formic acid and placed for a few days to form a hard block. The clear liquid was separated for vacuum distillation and the distillate was collected as the product at 22-25 ℃/12-18 mm. The still shall be fully ground joint and protected by drying pipe.
Formic acid Application field
is one of the basic organic chemical raw materials, widely used in pesticides, leather, dyes, medicine and rubber industries. can be directly used in fabric processing, tanning leather, textile printing and dyeing and green feed storage, and can also be used as metal surface treatment agent, rubber auxiliary and industrial solvent. In organic synthesis, it is used to synthesize various formates, acridine dyes and formamide series of medical intermediates.
The specific categories are as follows:
1.Pharmaceutical industry: It can be used for the processing of caffeine, aminopyrine, aminophylline, theobromine borneol, vitamin B1, metronidazole, mebendazole.
2.Pesticide industry: It can be used for the processing of powder, triazolone, tricyclozole, triamidazole, triazophos, polybulozole, tenobulozole, insecticide, dicofol.
3.Chemical industry: Raw materials for manufacturing various formates, formamide, pentaerythritol, neopentanediol, epoxy soybean oil, epoxy octyl soybean oleate, valeryl chloride, paint remover and phenolic resin.
4.Leather industry: used as tanning agent, deashing agent and neutralizing agent for leather.
5.Rubber industry: for the processing of natural rubber coagulants, rubber antioxidant manufacturing.
6.Laboratory preparation of CO.
7.Verification of cerium, rhenium and tungsten. Aromatic primary amines, secondary amines and methoxy groups were examined. The relative molecular weight and crystalline solvent methoxyl group were determined. Used as fixative in microscopic analysis.
8.Formic acid and its aqueous solution can dissolve many metals, metal oxides, hydroxides and salts, and the resulting formate can be dissolved in water, so it can be used as a chemical cleaning agent. does not contain chloride ions and can be used for cleaning equipment containing stainless steel materials.
9.Used to prepare apple, papaya, jackfruit, bread, cheese, cheese, cream and other edible flavor and whiskey, rum flavor. The concentration in the final flavored food is about 1 to 18 mg/kg.
10.Other: can also manufacture dyeing mordant, fiber and paper dyeing agent, treatment agent, plasticizer, food preservation, animal feed additives and reducing agents.