CN1199921C - Clean Recovery Process of Glyphosate Acid by-product Methyl Chloride - Google Patents

Abstract

The tail gas discharged in the production process of glyphosate acid by the alkyl acid method of phosphorous acid contains 20-90% of methyl chloride, and also contains impurities such as methanol, methylal, water, hydrogen chloride and the like, and the high-purity methyl chloride is obtained by a method of absorbing the impurities by a solvent, condensing the impurities or adding part of the impurities such as methanol and methylal into a fluid containing the hydrogen chloride to convert the impurities into the methyl chloride. The process not only solves the problem of environmental pollution in the production of the glyphosate acid, but also can greatly reduce the production cost of the glyphosate acid.

Description

The clean reclaiming process of byproduct chloromethane of glyphosate acid

Technical field

The present invention relates to the method for purifying and recovering of hydrolysis tail gas in the glyphosphonic acid building-up process, more particular words is to produce the high yield recovery by product methyl chloride the tail gas that discharges from glyphosphonic acid, and this process does not produce secondary pollution.

Background technology

Glyphosate is the maximum and the fastest steriland herbicide of rate of growth of sales volume in the world, whole world glyphosate technicals ultimate production reaches 260,000 tons, and along with the succeeding in developing and promoting the use of of the genetically modified crops of resistance glyphosate, for the continuation development of glyphosate provides new opportunity.The two kinds of methods that mainly contain are produced in whole world glyphosate industrialization: the one, and the IDA method promptly is starting raw material with the diethanolamine, U.S. Meng Shan waits offshore company generally to adopt this technology; Another kind method is an alkyl esterification method, domestic big multiple enterprises adopts this technology, alkyl esterification method glyphosate preparation method is open at document DEOLSNO.P 2942898.6, method commonly used is with Paraformaldehyde 96 or formaldehyde in containing the methanol solvate of triethylamine heating for dissolving 5-15 minute, again glycine is added heating for dissolving in this solution, add dimethylphosphite after 30 minutes, under 60-70 ℃, carry out condensation reaction, finish through 30-120 minute afterreaction, adding hydrochloric acid then is hydrolyzed (being called hydrolyzing process), generate the hydrochloride of glyphosphonic acid, the glyphosphonic acid crystallization was separated out after underpressure distillation removed solvent methanol and excessive hydrochloric acid again, filter after scouring, filter cake is glyphosphonic acid, the glyphosate that contains triethylamine hydrochloride and minimal amounts of dissolved in mother liquor and the washing lotion is used to prepare 10% sodium glyphosate aqua in liquid caustic soda and after reclaiming triethylamine.With the solution rectifying (being called the solvent recuperation operation) that underpressure distillation steams, isolate wherein solvent methanol and by product methylal, raffinate carries out biochemical treatment.If produce glyphosphonic acid with trimethyl phosphite, technology is similar.

Employing is in the production of alkyl phosphite technology (comprising with the phosphorus trichloride being raw material synthesizing phosphorous acid dimethyl ester operation) synthesizing glyphosate acid of starting raw material with dimethylphosphite or trimethyl phosphite, produce a large amount of tail gas that contains methyl chloride at dimethylphosphite synthesis procedure and the synthetic hydrolyzing process of glyphosphonic acid, can be used as the production of products such as carboxymethyl cellulose, chloroprene rubber behind the methyl chloride reclaiming clean wherein.Patent of invention 99119970.7 (franchise the applicant) discloses a kind of industrial method that reclaims the methyl chloride that produces in the alkyl phosphite method glyphosphonic acid building-up process, adopt be hydrolysis tail gas through washing, alkali cleaning, dry tertiary treatment, the storage of recompression condensation liquefaction.But this technology comes with some shortcomings in the rate of recovery and environmental protection: 1. the rate of recovery is low.Owing to contain saturated or oversaturated methylal and methyl alcohol under the normal pressure in this tail gas, if can not when washing, be removed, bring dehumidification system into after, can cause the consumption of siccative higher, and the quality of methyl chloride is reclaimed in influence.But be subjected to the influence of methylal and methyl alcohol solubleness and rate of mass transfer in water, in order to guarantee to reclaim the quality of methyl chloride, need to wash with a large amount of water (6 tons of/ton methyl chloride), and there is certain solubility (0.38 grams per liter) in methyl chloride in water, the washing water yield causes that greatly the solution loss of methyl chloride in water increases, and influenced the rate of recovery; 2. contaminate environment.Though this technology can be with the most of recovery of the methyl chloride in the discharging tail gas, reduced the pollution of glyphosphonic acid production to environment, but making, the defective of this technology itself can not thoroughly solve environmental issue, organic compound such as the methylal in the tail gas, methyl alcohol, methyl chloride have been dissolved in a large amount of bath wateies, and these materials of low levels can't adopt economic method to reclaim, can only carry out biochemical treatment or discharging, cause pollution environment; If carry out biochemical treatment, because methylal is embarrassed biochemical substances with methyl chloride, it is higher that it is carried out processing cost.3. it is not good to reclaim the methyl chloride quality.The impurity (moisture content, methylal, methyl alcohol) that also contains in the byproduct chloromethane of glyphosate acid that adopts the described tertiary treatment technology of this technology to reclaim is too high, in methyl chlorosilane is synthetic, can form polymkeric substance or thermo-cracking at catalyst surface coking, knot charcoal with the target product reaction, thus influence production.

Summary of the invention

The objective of the invention is to for solving the above-mentioned problem that exists, a kind of novel method of alkyl phosphite method glyphosphonic acid hydrolysis tail gas clean-up is provided, and whole recovery technology is environmental protection, can realize cleaner production, thoroughly solves the influence of glyphosphonic acid suitability for industrialized production discharging tail gas to environment.

Glyphosphonic acid production discharging tail gas consists of:

Methyl chloride	Air	Methyl alcohol	Methylal	Water	Hydrogenchloride	Other
							20-90	8-20	2-15	4-20	2-10	1-5	1-5

Methyl alcohol wherein, methylal are in saturated or hypersaturated state, the boiling point of methyl alcohol, methylal, methyl chloride is respectively 64.5 ℃ under normal pressure, 42.3 ℃,-23.73 ℃, the emergent pressure of methyl alcohol, methylal is 240 ℃, 215 ℃, far above 143 ℃ of methyl chloride, the method that therefore can adopt compression is with methyl alcohol in the gas phase and the most of condensation of methylal, thereby the absorption that can reduce subsequent handling is significantly loaded.Methyl chloride saturated vapor pressure at normal temperatures is 506.63kpa (absolute pressure), therefore tail gas can be compressed to 0.11-1Mpa (absolute pressure), for guaranteeing that methyl alcohol separates with the most economical of methyl chloride with methylal, preferred pressure is 0.45-0.55Mpa (absolute pressure), the separation that is liquefied of methyl alcohol more than 80% and methylal will be arranged this moment, this phlegma mainly contains methyl alcohol and methylal, can return the solvent recuperation operation in the glyphosphonic acid production, separate the 60-95% methylal, can be used as commodity selling, 〉=98% methyl alcohol can be as the solvent of synthesizing glyphosate acid.

To wash the methyl chloride solution loss that is caused with water or reduce contained organic substance influence problem of environment in the washing water that cause therefrom in order to reduce, also having a kind of technical scheme is that the tail gas that will contain methyl chloride makes its almost completely condensation except that contained non-condensable gasess such as air by pressurization and refrigerative method, this moment, pressure can be 0.4-2Mpa (absolute pressure), and temperature is-50-40 ℃ (technical professional can also adopt the combination of multiple pressure and temperature to reach same effect certainly).Components such as contained methyl chloride, methyl alcohol, methylal are separated from phlegma by the method for rectifying again, because the boiling point of methyl chloride is minimum, can at first obtain from cat head, bottom product is the mixture of components such as methyl alcohol, methylal, and this mixture is again through separating methyl alcohol and the methylal to obtain higher concentration.

Because most methyl alcohol and methylal separated (being called pre-treatment), can significantly reduce the consumption of washing water, in order to strengthen rate of mass transfer and to improve the content of methyl alcohol and methylal in the washing water, adopt the circulation absorption technique, single tower can be adopted according to tolerance in the absorption tower, perhaps multitower serial or parallel connection, working pressure is 0.08-0.3Mpa (absolute pressure).Contain methyl alcohol and methylal that weight concentration is 10-30% in the washing water, the solvent recuperation operation that also can return in the glyphosphonic acid production is separated.

Still contain carbonic acid gas, hydrogenchloride or vaporific hydrochloric acid in the gas after washing, can also be that potassium hydroxide, carbonate (sodium, the potassium) aqueous solution etc. of 10-40% absorbs with weight concentration except that the liquid caustic soda of patent of invention 99119970.7 disclosed 30% weight concentrations, factor preferred weight concentration such as comprehensive cost be the aqueous sodium hydroxide solution of 25-35%.

The water that still contains the 100-20000ppm that has an appointment in the gas after above-mentioned processing, still do not meet the requirement of industry standard, patent of invention 99119970.7 adopts the vitriol oil to carry out drying, but only use this method, still contain the water that is about 30ppm in the methyl chloride after the processing, though meet the industry standard of methyl chloride, very harsh to the requirement of the used methyl chloride of synthesizing methyl-chloro-silane, water content is low more favourable more to synthesizing methyl-chloro-silane.It is considered herein that and can also adopt other method that can remove micro-moisture, simple to operate, effective as adopting the solid matter that can absorb moisture to absorb moisture.Therefore can adopt behind vitriol oil drying process again with or the solid adsorbent that directly can absorb moisture with copper sulfate, calcium sulfate, calcium chloride, yellow soda ash, water glass, Vanadium Pentoxide in FLAKES, calcium oxide, 3A aluminum oxide molecular sieve etc. dewater, moisture content can be reduced to below the 15ppm after this art breading.

Also the tail gas of tail gas or treated mistake can be absorbed methyl chloride by organic solvent, method by stripping or rectifying obtains comparatively purified methyl chloride again, used organic solvent can be halogenated hydrocarbons, as first chlorination carbon, ethylene dichloride chlorinated aliphatic hydrocarbon, chlorination aromatic hydrocarbons such as mono chloro benzene, dichlorobenzene, m-chlorotoluene; Alcohols is as methyl alcohol, ethanol etc.; Ketone such as acetone, butanone etc.Require solvent for use higher boiling point concerning methyl chloride has higher solubleness and relative methyl chloride, can think that tetracol phenixin is to select preferably.

Contain impurity such as more methyl alcohol, methylal in the synthetic discharging of the glyphosphonic acid tail gas, and the purpose product is high-load methyl chloride, except that the method for above-mentioned separating impurity, the method of another efficient and cost-effective is by chemical reaction impurity conversion to be become the purpose product, huge separating device can be save on the one hand, more purpose product can also be obtained on the other hand.Methylal can be converted into methyl chloride, formaldehyde and water in the presence of hydrogenchloride; Methyl alcohol also can be converted into methyl chloride in the presence of the zinc chloride in hydrochloric acid or hydrogen chloride gas.Therefore carry out other handle before earlier with described tail gas by containing zine ion hydrochloric acid soln or mix laggard promoting the circulation of qi solid catalysis reaction with hydrogenchloride methyl alcohol and methylal are converted into methyl chloride also be a kind of method preferably, used catalyzer is the particulate alumina that contains zinc chloride.

Embodiment

It is considered herein that easily the technical scheme of industrializing implementation is: (1) pre-treatment: after described hydrolysis tail gas is sent into the gas holder buffering, with compressor compresses and cooling, the control compressor delivery pressure does not liquefy with methyl chloride and is advisable, be generally 0.1-1Mpa (absolute pressure), methylal and methyl alcohol in the hydrolysis tail gas are liquefied because of being in hypersaturated state, separate with the methylal and the methyl alcohol of separator, get pre-treatment gas liquefaction.The present invention is preferably 0.35-0.4Mpa (absolute pressure), and the washing hydration of isolated methylal and methyl alcohol and a step operation is also handled.(2) circulation washing: pre-treatment gas is removed the not methylal and the methyl alcohol of liquefaction in the pre-treatment gas by single-stage washing or plural serial stage washing, must wash gas.The washing of should pressurizeing of this step to improve methylal and the solubleness of methyl alcohol in water, reduces washing water consumption (can reduce to 1-2 ton/ton), and working pressure is 0.08-0.3Mpa (absolute pressure), is preferably 0.15-0.2Mpa (absolute pressure).Methylal and methanol content are higher in the washing water after the absorption, can with send methanol recovery system to separate purification after the methylal of pre-treatment discharging and methyl alcohol merge with rectifying tower, the methyl alcohol of recovery is used for the synthetic of glyphosphonic acid, methylal is as commodity selling.(3) alkali lye absorbs: with the liquid caustic soda washing of above-mentioned gas by 10-40%, remove acidic substance, used absorption agent also can be the potassium hydroxide of 10-40% or yellow soda ash or the salt of wormwood of 10-40%, from considering economically, the present invention is preferably sodium hydroxide, and concentration is 25-35%.(4) drying: will handle that back gas passes through vitriol oil plural serial stage drying after molecular sieve adsorption or anhydrous metal salt drying through the last step, compressed again condensation promptly gets the methyl chloride finished product.

Characteristics of the present invention are the methyl chloride rate of recovery height in the glyphosphonic acid tail gas, quality better, and methyl alcohol in the tail gas and methylal can be made full use of.

The method that is used for removing the impurity component of the synthetic discharging of glyphosphonic acid tail gas described in the invention can be carried out multiple combination, do not do the limit explanation in the present invention, should be included within the present invention yet even the combination of the processing scheme of being done on basis of the present invention is different from the described scheme of embodiment.

Embodiment: it is 4M that the exhaust emissions point from glyphosphonic acid and dimethylphosphite production respectively draws pipeline to a volume ³Surge tank through spinner-type flowmeter, adopts down routine scheme to handle methyl chloride and methylal weight content in the usefulness gas spectrum analysis exit gas of back respectively, in each experimentation from surge tank sampling analysis methyl chloride content wherein.

Embodiment 1: adopt patent of invention 99119970.7 described tertiary treatment, both earlier through big water gaging spray washing, washing is to be 89mm at four groups of diameters, high 1000mm, in fill out in the packing tower of glass rectangular saddle ring and carry out, washing gas absorbs through 30% liquid caustic soda, 85% vitriol oil again.

Embodiment 2: be compressed to 0.3Mpa (absolute pressure) earlier, be cooled to 15 ℃ through condenser, gas phase washes with water through two groups of above-mentioned packing towers again, and washing gas absorbs through 35% liquid caustic soda, 90% vitriol oil again, keeps system pressure and is not less than 0.2Mpa (absolute pressure).

Embodiment 3: be compressed to 5Mpa (absolute pressure) earlier, be cooled to-5 ℃ with chilled brine, get rid of the experiment of again phlegma being introduced through being incubated processing behind the non-condensable gases and use in the distillation tower, keep tower still temperature and be no more than 5 ℃, the tower internal pressure is 0.2Mpa (absolute pressure), analyzes the overhead gas phase composite.

Embodiment 4: is the stainless steel tube of 25mm with exsiccant with the aluminium sesquioxide granular solids filling diameter that zinc chloride soaks, adopt the electric heating type of heating, gas is mixed the back feed this reactor with the hydrogenchloride that parses from hydrochloric acid, and to keep temperature of reaction be 120-180 ℃, adopts the method for embodiment 1 to handle exit gas again.

Embodiment 5: pass through the anhydrous cupric sulfate drying again after embodiment 2 handles.

Embodiment 6: adopt embodiment 1 described packing tower, replace water to absorb with tetracol phenixin, temperature is controlled at 20-30 ℃, pressure 0.6-1Mpa (absolute pressure).Through embodiment 3 described distillation tower distillations, the control tower internal pressure is 0.05Mpa (absolute pressure) to absorption liquid again, and cat head is controlled at 0-10 ℃ with chilled brine, adopts the method for embodiment 1 to handle exit gas again.

The experimental result tabulation

Sequence number	Methyl chloride weight content (%)		Impurity weight content ppm
					Surge tank	Outlet	Methylal	Water
	1	62.2	99.5	35					40
2					64.5	99.8	28	32
	3	62.3	98.1	80					68
4					63.7	99.7	30	35
	5	62.8	99.9	26					10
6					62.0	99.7	30	27

Claims (24)

1. a technique of reclaiming the methyl chloride produced in the production process of glyphosate acid is characterized in that: (1) Collect the tail gas discharged during the production of glyphosate acid; (2) Use the separation method of pressurizing or cooling or pressurizing and cooling the fluid containing methyl chloride to treat the collected tail gas, so that the methyl chloride, methanol, methylal, and water in it are partially or completely liquefied, and the chlorine in it is Methane content increased. 2. The process according to claim 1, wherein the recovered methyl chloride is characterized by: 1. the weight content of methyl chloride is 20-99.99%; 2. the characteristic impurity methylal is contained, and its weight content is 0.1 ppm-80%. 3. The process according to claim 2, wherein the methyl chloride is characterized by: 1. the weight content of the methyl chloride is 99-99.99%; 2. the weight content of the characteristic impurity methylal is 0.1-100 ppm. 4. according to the technology of claim 1, the feature of described glyphosate acid is: adopt dimethyl phosphite or trimethyl phosphite to be the alkyl phosphite method of one of main raw materials to produce. 5. according to the technique of claim 4, described glyphosate acid production technique comprises phosphorus trichloride synthesis dimethyl phosphite or trimethyl phosphite as one of glyphosate acid synthesis process. 6. The process according to claim 1, wherein said partial liquefaction is characterized in that the state of the gas containing chloromethane is adjusted to: the pressure is 0.1-1Mpa absolute pressure, the temperature is -30-50°C, and the easily liquefiable substance methanol therein is 10-99% of methylal is liquefied and removed by gas-liquid separation. 7. The process according to claim 1, wherein said complete liquefaction is to pressurize the gas containing methyl chloride to an absolute pressure of 0.4-2Mpa, and cool it to -50-40°C, wherein the methyl chloride and methyl chloride are more easily Other liquefied components such as methanol, methylal, and water are condensed, and the non-condensable gas is removed, and then the methyl chloride is separated from other components by rectification. 8. according to the process of claim 1, described separating method further comprises the method that the fluid containing methyl chloride is absorbed by solvent and makes the content of impurity methyl alcohol contained in the fluid, methylal, water, hydrogen chloride and hydrochloric acid mist drop . 9. The process according to claim 1 or 8, wherein said separation method further comprises passing the fluid containing methyl chloride through a solid adsorbent capable of absorbing water, and adopting an adsorption method to reduce the content of water contained therein. 10. The process according to claim 8, wherein said solvent absorption is characterized in that: the solvent used is water or an aqueous solution containing alkaline substances, or concentrated sulfuric acid. 11. according to the technology of claim 10, described alkaline aqueous solution is used for removing the acidic substance hydrogen chloride, hydrochloric acid mist, carbon dioxide that entrains in the chloromethane gas, it is characterized in that: the hydroxide that wherein contains sodium or potassium element or carbonates. 12. according to the technology of claim 11, the concentration of described aqueous solution containing sodium hydroxide or potassium hydroxide or sodium carbonate or potassium carbonate is: the sodium hydroxide of 10-40% or the potassium hydroxide of 10-40% or 10-40% sodium carbonate or potassium carbonate. 13. The process according to claim 10, wherein said alkaline aqueous solution is sodium hydroxide having a concentration of 25-35%. 14. The process according to claim 10, said concentrated sulfuric acid is used to remove entrained water in the gas containing chloromethane, and its concentration is 70%-99%. 15. according to the technology of claim 10, described water is used for removing the water-soluble impurity methyl alcohol, methylal, hydrogen chloride carried in the chloromethane gas, and the feature of this technology is: cycle operation, pressure is absolute pressure 0.08- 0.3 MPa. 16. The process according to claim 15, the pressure is 0.15-0.2 MPa absolute. 17. The process according to claim 9, wherein said solid adsorbent for removing water entrained in chloromethane-containing gas is a hygroscopic oxide or anhydrous metal salt. 18. The process according to claim 17, wherein said oxide or anhydrous metal salt is copper sulfate, calcium sulfate, calcium chloride, sodium carbonate, sodium silicate, phosphorus pentoxide, calcium oxide or 3A alumina Molecular sieve. 19. according to the technique of claim 1, 7 or 8, wherein the solvent recovery operation in the production of glyphosate acid is returned to the washing water, condensate and rectification raffinate that contain the substances such as methanol or methylal after the separation of methyl chloride. 20. The process according to claim 1 or 8, wherein the separation method further comprises passing the methyl chloride-containing fluid through an organic solvent to transfer the methyl chloride in the fluid into the solvent by absorbing it. 21. The process according to claim 20, said absorbing method further comprising desorbing and separating the absorbing solution containing methyl chloride and other impurity components. 22. The process according to claim 21, wherein said organic solvent is a halogenated hydrocarbon with 1-10 carbon atoms, a ketone, an alcohol or a hydrocarbon with 4-16 carbon atoms. 23. A process according to claim 20, wherein said organic solvent is carbon tetrachloride. 24. according to the technology of claim 1, it also comprises before carrying out described separation method, the tail gas that the collected chloromethane is passed into the solution that contains hydrogen chloride or enters reactor with hydrogen chloride and methyl alcohol and formaldehyde wherein are mixed The acetal is partially or completely converted to methyl chloride.