Method of obtaining carbamide-formaldehyde concentrate

FIELD: chemistry.

SUBSTANCE: invention relates to method of obtaining carbamide-formaldehyde concentrate with mole ratio carbamide:formaldehyde 1:(4.9-5). Method includes oxidative dehydration of methanol in formaldehyde on silver or iron-molybdenum catalyst in one or several tubular or shelf-type reactors and chemical absorption of formaldehyde-containing gas in two successively placed column apparatuses. Abgas from first column apparatus is divided into two parts with ratio 1:4 with supply of smaller one to catalytic after-burning, and larger one into second column apparatus for chemical absorption by 15-25% carbamide solution with formation of prepolymer with molar ratio carbamide:formaldehyde, equal (0.1-0.5):1, mixed with 50-65% water solution of carbamide in flow mixer and supplied further for chemical absorption of formaldehyde-containing gas into upper section of first column apparatus.

EFFECT: invention makes it possible to optimise scheme of obtaining carbamide-formaldehyde concentrate in order to increase efficiency of production and reduce formaldehyde content in abgas, supplied into reactor of oxidative methanol dehydration.

1 dwg, 1 ex

 



 

Same patents:

FIELD: chemistry.

SUBSTANCE: method is carried out in multiple steps in a medium with variable acidity. The method comprises weakly alkaline condensation of carbamide and carbamide-formaldehyde concentrate in an aqueous solution at 20-95C and pH 7.2-9.2, wherein molar ratio of formaldehyde to carbamide is (1.8-2.2):1; holding the condensation solution for 10-20 minutes at 85-99C; acidifying the condensation solution to pH 4.7-5.5 with aqueous glyoxal solution with concentration of basic substance of not more than 50 wt % in amount of 1-20% with respect to formaldehyde. Further, polycondensation of the reaction mass is carried out in an acidic medium, followed by neutralisation to pH 7.5-8.5 and simultaneous cooling to 70-75C. Pre-condensation of the reaction mass is carried out with additional supply of carbamide to the final molar ratio of formaldehyde to carbamide of (1.0-1.25):1. The finished resin is cooled and packed.

EFFECT: invention reduces content of free formaldehyde in the finished urea formaldehyde resin and wood chipboard based thereon.

2 ex

FIELD: chemistry.

SUBSTANCE: invention relates to wood-processing industry and can be used in manufacturing carbamidoformaldehyde oligomers, used for production of chipboards. method of manufacturing carbamidoformaldehyde oligomers includes loading formaldehyde, its neutralisation to pH 8.0-9.0 with further loading of the first carbamide portion to its complete dissolution and introduction of parafolmaldehyde with heating with exposure to pH not lower than 6.5, introduction of the second carbamide portion with exposure at said stage to pH not lower than 6.5, after which in order to reduce mixture pH value to 4.5-5.0 ammonium chloride solution is added with heating and the end of the stage is checked by miscibility with water when miscibility 1:2-1:3 is achieved, after which mixture pH is increased to 8.0-8.5 with reduction of temperature to 70-75C and the third carbamide portion is introduced, after dissolution of which oligomer is subjected to vacuum-drying, and the fourth carbamide portion is introduced to mole ratio of carbamide to formaldehyde 1:1.4 with further oligomer cooling.

EFFECT: method will make it possible to reduce the content of free formaldehyde in carbamidoformaldehyde oligomers and reduce toxicity of chipboards, obtained on their base.

2 tbl, 4 ex

FIELD: woodworking industry.

SUBSTANCE: method of production of urea-formaldehyde oligomer comprises loading of formalin, its neutralisation to pH 7.0-7.5 with modifier-catalyst based on salt of polyfunctional acid, adding of urea, after dissolution of urea, if necessary, reduction of pH to 6.8-7.2 with ammonium chloride, followed by heating to 90-92C and keeping for 30 minutes. Further, reduction of pH of the mixture is carried out with a solution of ammonium chloride to 4.2-4.5 and kept at 90-92C with stirring for 30 min, cooled to 60-65C, adjusted to pH 6.7-7.0, the catalyst modifier is added while stirring based on salt of polyfunctional acid, urea is added, and kept at 60-65C while stirring for 30 minutes to obtain an oligomer, it is neutralised with modifier-catalyst based on salt of polyfunctional acid to pH 8.0-8.5. The catalyst-modifier based on salt of polyfunctional acid is used as modifier obtained by mixing caustic soda or potassium hydroxide, lactic acid or tartaric acid and water with the ratio of ingredients in parts by weight: caustic soda or potassium hydroxide 13-15, lactic or tartaric acid 16-19, water 68-69.

EFFECT: reduction of toxicity with improved physical and mechanical properties of plates obtained with the use of urea-formaldehyde oligomer according to the invention.

1 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: method of producing an amino plastic aqueous dispersion involves obtaining a dispersion by preparing a concentrated 50-70% urea solution or a mixture of urea and melamine with formaldehyde in molar ratio 1:2.0-2.2; holding the reaction solution while stirring for 50-60 minutes at 50-70C and pH 7.0-8.0; adding a new portion of urea to final ratio of 1:0.8-1.3; holding for 10-20 minutes; adding 0.01-0.5 wt % stabiliser in form of aqueous solutions of methyl cellulose or derivatives thereof; acidifying to pH 5.0-6.0; mixing at 50-70C for 10-30 minutes until loss of solubility, cooling and neutralising the system. To obtain dispersions in form of solid particles of a cured polymer, the dispersion system is continuously stirred at 40-50C and pH 3.0-4.0 for 1-2 hours until a loose powder is obtained.

EFFECT: reduced exothermic effect of the reaction mixture, providing storage stability, capacity for dilution with water and compatibility with solutions of dispersions of other polymers, obtaining aqueous dispersions of amino plastics in form of liquid, gel-like or solid condensation products.

5 cl, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to method of continuous production of aqueous solution of amino formaldehyde resin, solution of urea-formaldehyde resin or melamine-urea-formaldehyde resin. Method includes the following stages: a) preparation of reaction mixture of amino compound and formaldehyde in form of concentrated aqueous solution or in form of solid phase, b) addition of catalyst to reaction mixture, c) carrying out reaction of reaction mixture condensation in presence of catalyst. At stage a) amino compound and formaldehyde are added inform of concentrated aqueous solution or in form of solid phase to total content of solid phase in reaction mixture 40-85 wt % (dry mass relative to total mass of reaction mixture). At stage c) reaction of condensation occurs in continuous flow of reaction mixture in reactor of continuous plug flow reactor. At stage b) catalyst is continuously added and finely crushed into reaction mixture through one or several placed of addition. At non-obligatory stage d) addition of amino compound after condensation is carried out, and at non-obligatory stage e) removal of water to increase solid phase content is carried out. In the method reaction mixture is fed through static mixer of continuous plug flow reactor, which contains pipe, in which there are, at least, 4, preferably, at least, 6 static mixing elements, and it has one or more, preferably several places for addition, preferably, only in place of location of first or first two mixing elements for continuous crushing catalyst through said place (places).

EFFECT: obtaining highly concentrated solution of amino formaldehyde resin in continuous process.

25 cl, 1 dwg, 6 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing carbamide-formaldehyde concentrate. The method involves oxidative dehydrogenation of methanol to formaldehyde on a silver or iron-molybdenum catalyst in one or more flow- or deck-type reactors, as well as chemisorption and absorption of formaldehyde-containing gas in two series-arranged towers. For chemisorption in the first tower, 50-65% aqueous carbamide solution is used. The gas coming out of the chemisorption tower is divided into two portions, where the smaller portion is fed for catalytic after burning and the larger portion is fed into the lower section of the second tower for absorption of formaldehyde with demineralised water. The solution of methylene glycol formed in the second tower is taken for mixing with carbamide solution in a flow mixer to obtain a pre-condensate which is fed into the upper section of the first tower.

EFFECT: invention increases efficiency of production and prevents formation of hard-to-dissolve products.

1 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing urea formaldehyde resin. The method involves condensation of carbamide and formaldehyde in initial and final molar ratio of 1:1.95-2.0 and 1:1.05-1.15, respectively, in a medium with variable acidity while heating, adding a polybacid alcohol as a modifying additive and post-condensation with an additional amount of carbamide. Formaldehyde is added as part of a low-methanol carbamide-formaldehyde concentrate with 600.5 wt% formaldehyde, 250.5 wt % carbamide, and water. Condensation is carried out at temperature 90-100C for 30-60 minutes while changing pH from 9.0-7.0 to 5.8-5.0, in the presence of an acid catalyst and pentaerythritol, which is taken as a modifying additive in amount of 0.35-2.0% of the total weight of the obtained urea formaldehyde resin. Further, carbamide is added at temperature 65-90C and post-condensation is carried out for 30-60 minutes, while changing pH to 7.5-8.5 and then cooling to 20-30C.

EFFECT: high technological effectiveness of the process of producing resin while simultaneously improving physical and mechanical properties of articles made from said resin.

1 cl, 1 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing urea formaldehyde resin, which can be used in wood processing industry when producing wood chipboards and fibreboards, plywood and laminated wood structures. The method involves condensation of carbamide and formaldehyde with initial and final molar ratio of 1:1.95-2.1 and 1:1.01-1.6, respectively, in a variable pH medium while heating, and post-condensation with an additional amount of carbamide. Formaldehyde is added in form of paraform and 37% formaldehyde solution. Condensation is carried out at temperature 90-100C for 30-60 minutes while varying pH from 9.0-8.0 to 5.8-5.0. Further, carbamide is added and post-condensation is carried out at temperature 65-90C for 30-90 minutes, while changing pH to 7.5-8.5. The mixture is cooled to temperature 20-30C.

EFFECT: low toxicity of the obtained urea formaldehyde resin.

2 cl, 1 ex

FIELD: chemistry.

SUBSTANCE: method involves condensation of formaldehyde to carbamide in molar ratio less than 2.0:1.0 in a medium with variable acidity at temperature not higher than 100C until achieving viscosity of at least 700 cP. Further, post-condensation at molar ratio of formaldehyde to carbamide 0.95-1.5:1.0 for not less than 30 minutes and final cooling are performed. Not less than 10 minutes after the beginning of the post-condensation step, alkali is added to the reaction mixture at temperature 40-65C in such an amount that pH lies in the range of 9.0-10.0.

EFFECT: obtaining reactive carbamide-formaldehyde resins with short gel time and stability during storage.

3 cl, 7 ex, 2 tbl

FIELD: chemistry.

SUBSTANCE: method involves oxidative dehydrogenation of methanol to formaldehyde on an iron-molybdenum catalyst in one or more flow- or deck-type reactors, as well as chemisorption and absorption of formaldehyde-containing gas in two successively lying towers. During chemisorption in the first tower, the absorbent used is 50-65% aqueous solution of carbamide and carbamide-formaldehyde concentrate is obtained during chemisorption. Non-absorbed gas coming out of the chemisorption column is divided into two parts. The smaller part is taken for catalytic burning and the larger part is fed into the lower section of the absorber. Demineralised water is used during absorption in the second tower and the methylene glycol solution formed is fed into the upper section of the first tower.

EFFECT: avoiding formation of methane-containing waste water.

1 cl, 1 ex, 1 dwg

FIELD: chemistry.

SUBSTANCE: method involves oxidative dehydrogenation of methanol to formaldehyde on an iron-molybdenum catalyst in one or more flow- or deck-type reactors, as well as chemisorption and absorption of formaldehyde-containing gas in two successively lying towers. During chemisorption in the first tower, the absorbent used is 50-65% aqueous solution of carbamide and carbamide-formaldehyde concentrate is obtained during chemisorption. Non-absorbed gas coming out of the chemisorption column is divided into two parts. The smaller part is taken for catalytic burning and the larger part is fed into the lower section of the absorber. Demineralised water is used during absorption in the second tower and the methylene glycol solution formed is fed into the upper section of the first tower.

EFFECT: avoiding formation of methane-containing waste water.

1 cl, 1 ex, 1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a gas-phase method of catalytic conversion of lower alkanes. A method is described for catalytic conversion of lower alkane, containing up to 5 carbon atoms, into at least one product which is chosen from a group consisting of alcohols, aldehydes and their mixture, involving bringing said lower alkane into contact with an oxidising agent in the presence of a catalyst, containing a platinum complex which is deposited on a carrier, with the following structure: in which: L is a ligand, which is chosen from amino-ligands, hydroxyl ligands and imidazolyl ligands; A is a ligand which is chosen from hydroxyl ligands, chloro-ligands and amino-ligands; M is a metal cation in the catalyst carrier, which is chosen from cations of aluminium, silicon, zirconium, titanium and molybdenum; and n is an integer, which is chosen from 4, 2 and 1, Pt in the catalyst is a cation in a valent state which is chosen from valent states (IV), (II) and (I), which correspond to numerical values of n, where the said platinum cation forms the central core of the platinum complex, ligands L and ligands A surround the central core and ligands L chemically bond the complex to the surface of the carrier, under which metal cations M are localised.

EFFECT: high conversion and selectivity of formation of methanol in direct oxidation of methane or natural gas with air or molecular oxygen in the presence of catalyst promoters.

15 cl; 4 tbl, 12 ex

FIELD: chemistry.

SUBSTANCE: invention pertains to the method of uninterrupted production of formalin and carbamide-formaldehyde concentrate. The method involves catalytic dehydrogenation of methanol with formation of formaldehyde-containing contact gases, in which there is separation of part of the formaldehyde in form of formalin, supply of contact gases for chemisorption of formaldehyde by a water solution of carbamide, obtaining of carbamide-formaldehyde concentrate with calculated molar ratios of formaldehyde to carbamide of (4.5-5.2):1. Separation of part of the contact gases in form of formalin is made by cooling the contact gases of dehydrogenation of methanol to temperature lower than the dew point of 50-80°C. The resulting condensate is removed in form of formalin, and the remaining part of contact gases is taken for chemisorption.

EFFECT: method increases quality and stabilisation of the mixture of formalin and carbamide-formaldehyde concentrate and simplifies the process.

1 dwg, 4 ex

FIELD: industrial organic synthesis.

SUBSTANCE: process comprises providing alcohol-water-gas mixture via evaporation of water-methanol mixture, combining the latter with air and emission gas, catalytic dehydrogenation of methanol on silver catalyst at elevated temperature followed either absorption of formaldehyde from reaction gases or chemisorption thereof from indicated gases with urea solution in column to produce and recover formalin in case of absorption or urea-formaldehyde solution in case of chemisorption. Into absorption/chemisorption stage, preheated emission gas is supplied in weight proportion to methanol (0.25-6,8):1. Generally, emission gas is preheated to 50-130°C.

EFFECT: increased concentration of produced formalin or urea-formaldehyde solution, widened concentration control range, simplified equipment, and reduced fire risk.

2 cl, 1 dwg, 4 ex

The invention relates to the technology of organic synthesis, and in particular to an improved process for the preparation of formalin used in chemical industry, medicine and agriculture

The invention relates to a continuous method of obtaining aqueous solutions of formaldehyde, in particular solutions having a concentration in the range from 53 to 57 wt.%, the method includes the following stages:

(a) the air supply and methanol in the evaporator, in which the methanol is evaporated, the formation of gas-phase mixture of methanol and air;

(b) interaction of gas-phase mixture of methanol and air over the catalyst at elevated temperature to obtain a reaction mixture containing formaldehyde formed by partial conversion of methanol and water vapors and noncondensable gases;

(c) passing the reaction mixture through at least one adsorption column where the above-mentioned mixture is absorbed in the aqueous solution flowing in the opposite direction;

(d) separation of the aqueous and non-condensable gases in the absorption columns;

(e) cooling and washing of non-condensable gases that carry small amounts of methanol and formaldehyde; and

(f) the fractional distillation of an aqueous solution with the appropriate Department of methanol

FIELD: industrial organic synthesis.

SUBSTANCE: process comprises providing alcohol-water-gas mixture via evaporation of water-methanol mixture, combining the latter with air and emission gas, catalytic dehydrogenation of methanol on silver catalyst at elevated temperature followed either absorption of formaldehyde from reaction gases or chemisorption thereof from indicated gases with urea solution in column to produce and recover formalin in case of absorption or urea-formaldehyde solution in case of chemisorption. Into absorption/chemisorption stage, preheated emission gas is supplied in weight proportion to methanol (0.25-6,8):1. Generally, emission gas is preheated to 50-130°C.

EFFECT: increased concentration of produced formalin or urea-formaldehyde solution, widened concentration control range, simplified equipment, and reduced fire risk.

2 cl, 1 dwg, 4 ex

FIELD: chemistry.

SUBSTANCE: invention pertains to the method of uninterrupted production of formalin and carbamide-formaldehyde concentrate. The method involves catalytic dehydrogenation of methanol with formation of formaldehyde-containing contact gases, in which there is separation of part of the formaldehyde in form of formalin, supply of contact gases for chemisorption of formaldehyde by a water solution of carbamide, obtaining of carbamide-formaldehyde concentrate with calculated molar ratios of formaldehyde to carbamide of (4.5-5.2):1. Separation of part of the contact gases in form of formalin is made by cooling the contact gases of dehydrogenation of methanol to temperature lower than the dew point of 50-80°C. The resulting condensate is removed in form of formalin, and the remaining part of contact gases is taken for chemisorption.

EFFECT: method increases quality and stabilisation of the mixture of formalin and carbamide-formaldehyde concentrate and simplifies the process.

1 dwg, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a gas-phase method of catalytic conversion of lower alkanes. A method is described for catalytic conversion of lower alkane, containing up to 5 carbon atoms, into at least one product which is chosen from a group consisting of alcohols, aldehydes and their mixture, involving bringing said lower alkane into contact with an oxidising agent in the presence of a catalyst, containing a platinum complex which is deposited on a carrier, with the following structure: in which: L is a ligand, which is chosen from amino-ligands, hydroxyl ligands and imidazolyl ligands; A is a ligand which is chosen from hydroxyl ligands, chloro-ligands and amino-ligands; M is a metal cation in the catalyst carrier, which is chosen from cations of aluminium, silicon, zirconium, titanium and molybdenum; and n is an integer, which is chosen from 4, 2 and 1, Pt in the catalyst is a cation in a valent state which is chosen from valent states (IV), (II) and (I), which correspond to numerical values of n, where the said platinum cation forms the central core of the platinum complex, ligands L and ligands A surround the central core and ligands L chemically bond the complex to the surface of the carrier, under which metal cations M are localised.

EFFECT: high conversion and selectivity of formation of methanol in direct oxidation of methane or natural gas with air or molecular oxygen in the presence of catalyst promoters.

15 cl; 4 tbl, 12 ex

FIELD: chemistry.

SUBSTANCE: method involves oxidative dehydrogenation of methanol to formaldehyde on an iron-molybdenum catalyst in one or more flow- or deck-type reactors, as well as chemisorption and absorption of formaldehyde-containing gas in two successively lying towers. During chemisorption in the first tower, the absorbent used is 50-65% aqueous solution of carbamide and carbamide-formaldehyde concentrate is obtained during chemisorption. Non-absorbed gas coming out of the chemisorption column is divided into two parts. The smaller part is taken for catalytic burning and the larger part is fed into the lower section of the absorber. Demineralised water is used during absorption in the second tower and the methylene glycol solution formed is fed into the upper section of the first tower.

EFFECT: avoiding formation of methane-containing waste water.

1 cl, 1 ex, 1 dwg

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