Method of stabilizing selection process ethylene oxide

 

(57) Abstract:

The invention relates to a method for selection of the ethylene oxide absorption from the gas mixture obtained in the oxidation of ethylene with oxygen in the presence of silver-containing catalyst, and can be used in the production of ethylene oxide. A method of stabilizing selection process the ethylene oxide from the gas mixture formed during the oxidation of ethylene with oxygen in the presence of silver-containing catalyst, comprising the absorbance of aqueous solutions etilenglikola, desorption obtained saturated sorbent at an elevated temperature followed by treatment of the sorbent after the stage of desorption, a defoamer, an alkaline reagent and recycle sorbent to the stage of absorption, while additionally determine the content of surface-aktivnih substances in the sorbent after the stage of desorption of ethylene oxide and maintain their concentration is not higher than 0.02 wt.%. Technical result: the stability of the process of selection of the ethylene oxide from the contact of the gas and reducing the flow of antifoam. 3 table.

The invention relates to a method for allocation of ethylene oxide (MA) absorption from the gas mixture obtained in the process of oxidation of the oxide ethylene.

Despite large differences in the technology of conducting oxidation of ethylene by atmospheric air or pure oxygen in the presence of a silver catalyst known methods of allocation of ethylene oxide gas from the contact of these processes are conventional and include the stage of absorption of aqueous solutions of monoethylene glycol, desorption of ethylene oxide with subsequent recycling of the regenerated sorbent after heat recovery at the site of absorption (N. N. Lebedev. Chemistry and technology of basic organic and petrochemical synthesis. - M.: Chemistry, 1988, pp. 420-424).

Depending on the conditions of the oxidation of ethylene, the nature of the catalyst, its operating life, etc., in the oxidation process produces by-products such as organic acids and aldehydes. For full chemical binding of organic acids and aldehydes and maintain the neutral environment of circulating sorbent hold constant the treatment of the latter with an aqueous solution of alkali metal hydroxide. In addition, to control foaming of the used sorbent and, accordingly, a stable operation of the absorption column in the contact conditions “p the stage after desorption enter the antifoam in the form of aqueous emulsions of silicone fluids or high molecular weight unsaturated acids. Usually as antifoam silicone fluid used their emulsions containing emulsifiers are surface-active substances (surfactants) and polymethyl or polyethylsiloxane liquids with molecular weight of 500-10000. Also to avoid accumulation in the sorbent content of monoethylene glycol and heavy glycols part of the sorbent is continuously output to the node selection etilenglikola, thus the sorbent provide the content of monoethylene glycol depending on the oxidation of ethylene with air or oxygen in the range of 5.0-20.0 wt.%. (Patent England No. 1435848, IPC 07 D 303/04, publ. 19.05.1976; RF patent №1790179, C 07 D 303/04, 301/32, publ. 20.05.1995). To determine the efficiency of the antifoam and evaluation of stable operation of the absorption column continually determination of foaming properties of the sorbent after the stage of desorption of the ethylene oxide. If high values of spanelement and time of defoaming sorbent to prevent ejection of the liquid sorbent with a circulating gas from the absorption column usually reduce the load on the gas stream in the absorber, increase the amount of antifoam in the system and increase the output of the sorbent on the site selection process.

Fault is ment forecasting the stability of the absorption process and the timeliness of actions taken to ensure the stable operation of this site, leading to abrupt changes in the modes of operation of the installation and unjustified increase of consumption of antifoam.

The objective of the invention is to increase the stability of the process of separation of ethylene oxide from the contact of the gas and reducing the flow of antifoam.

In the proposed method, the stabilization process of the selection of the ethylene oxide from the gas mixture formed during the oxidation of ethylene with oxygen in the presence of silver-containing catalyst, comprising the absorbance of aqueous solutions etilenglikola, desorption obtained saturated sorbent at an elevated temperature followed by treatment of the sorbent after the stage of desorption, a defoamer, an alkaline reagent and recycle sorbent to the stage of absorption, additionally determine in the sorbent after the stage of desorption of the ethylene oxide content of surface-active substances, which are formed as a result of the reaction of oxidation of high molecular weight aldehydes and glycols, and maintain the concentration of the surfactants is not higher than 0.02 wt.%.

Additional determination of the content of surface-active substances, resulting from the reaction of oxidation of the high-molecular Alda is to predict the situation predisposition sorbent for pricing and to prevent a sharp increase in pressure drop in the column absorption due to foaming of the sorbent.

The term "surfactant" means defining the sorbent total content of sodium salts of high molecular weight acids, which are formed in the system as a result of the reaction of oxidation of high molecular weight aldehydes and glycols, but also come in the form of emulsifier in the emulsion used antifoam. Determining the concentration derivatives of high molecular weight acids is carried out by a known method periodicmaintenance destructive oxidation (Sakura Century A. Methods of analysis and control in the production of surfactants. M.: Chemistry, 1977, pages 152-155).

The peculiarity of these surfactants is a high foaming capacity and low efficiency of defoaming created water-glycol solutions of these products at concentrations above 0.02 wt.% conventional processes for the absorption of ethylene oxide with defoamers based on polymethyl-, polyethylsiloxane liquids or unsaturated alcohols of the type olejowego alcohol.

Evaluation of the effectiveness of the proposed method of stabilizing selection process ethylene oxide was carried out by determination of foaming properties of the model process is Rotanova acid, the oxidation product of triethylene glycol and real sorbent production of ethylene oxide.

The implementation of the method of stabilizing selection process ethylene oxide are illustrated in the following examples.

Example 1

For determination of foaming properties of the model solution sorbent prepare a water-glycol solution containing of 16.0 wt.% monoethylene glycol (MEG), 3.0 wt.% diethylene glycol (deg), and 1.0 wt.% triethylene glycol (TEG). In the resulting solution is injected pre-cooked 1,0% aqueous emulsion of antifoam obtained using polymethylsiloxanes liquid PMS-1000 as antifoam and sodium oleate as an emulsifier. The content of PMS-1000 in the solution ranges from 0.005 wt.%.

Definition of spanelement this model solution is conducted according to the following procedure: into a cylinder with a volume of 500 cm3pour 140 cm3the model solution to the bottom of the cylinder is lowered gazopromyvateli with a porosity of 40 and through him the model solution begin to barbthroat air. The air flow rate is 1.0 l/min After 10 min of bubbling determine the height of the foam, the amount of the formed foam is 50 cm3. After disconnecting the air supply Gazpromavia solution is injected to 0.001 wt.% sodium salt-crotonic acid, also give the definition of spanelement this solution under these conditions. The volume of foam is 55 cm3the time of defoaming 4,0 sec.

So spend the definition of spanelement model solution at varying concentrations of surfactants in the form of sodium salt-crotonic acid and change the content of antifoam solution. The results obtained are presented in table 1.

Example 2

Testing is carried out as described in example 1. During the tests as a surfactant in the model solution using sodium salt of the oxidation product of triethylene glycol, previously prepared by the following procedure: into a round bottom flask 500 ml pour 250 ml of triethylene glycol, then the contents of the flask with reflux condenser heated to 200-220°C and within 6,0 hours purge air consumption, the latter is 3.0 l/min as a result of this get the product acidity 256 mg KOH/g, which is then at 40-50°C and with constant stirring to neutralize 20,0% aqueous solution of sodium hydroxide to a pH of 7.8.

Thus obtained product is further used as a surfactant in the test model solutions of the sorbent. The obtained results and and content of the surfactant in terms of on-crotonic acid sorbent from the production of ethylene oxide, simultaneously estimated the pressure drop in the absorber. This site absorption of the production of ethylene oxide was operated under the following conditions:

- load reaction gas, nm3/h 340000-350000;

the content of ethylene oxide in the reaction gas, vol.% 0,9-11,0;

- consumption of sorbent for irrigation in the absorber, t/h 350-400;

- mass fraction of etilenglikola in the sorbent, % 15,0-18,0;

- the temperature of the sorbent at the entrance to the absorber°C 27-29;

- the amount of sorbent in the normal drop in the absorber, t/h 6,0-7,0;

range of pH values of the sorbent during the test 6,0-7,5;

During testing, the concentration of glycols ranged from 12 to 16 wt.%.

To adjust spanelement sorbent and ensure stable operation of the site of absorption and desorption of ethylene oxide in the sorbent constantly serves the antifoam emulsion based polymethylsiloxanes liquid PMS-1000 flow, ensuring the contents PMS-1000 sorbent in the range of 0.005-0.01 wt.%. The results are presented in table 3.

The analysis of the results of the site of absorption of ethylene oxide (table 3) shows that with increasing content poverhnosti in the absorber (the system parameters on the 19-th and 20-th day), while “the volume of foam and the settling time foam” sorbent does not reflect the real state of susceptibility of the sorbent to foaming. Comparison of the results of the tests of absorption on the 20th, 21st and 22nd days shows that the increase in output of the sorbent with increasing concentration of surfactant helps to stabilize the pressure drop in the absorber of ethylene oxide.

As seen from the above examples, the proposed method of separation of ethylene oxide from the gas mixture formed during the oxidation of ethylene with oxygen in the presence of silver-containing catalyst, allows to stabilize the process by predicting the state of node removals, to take timely measures to ensure the stable operation of the system and to prevent situations that lead to abrupt changes in the modes of operation of the installation and unjustified increase of consumption of antifoam.

The method of stabilization of the allocation process of the ethylene oxide from the gas mixture formed during the oxidation of ethylene with oxygen in the presence of silver-containing catalyst, the absorption of aqueous solutions etilenglikola, desorption obtained saturated sorbent at an elevated temperature with posledadu absorption, characterized in that it further determine the sorbent after the stage of desorption of the ethylene oxide content of surface-active substances, which are formed as a result of the reaction of oxidation of high molecular weight aldehydes and glycols, and maintain the concentration of the surfactants is not higher than 0.02 wt.%.

 

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