JPH0510371B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a polyether recovery method in which polyethers are concentrated and recovered from highly basic wastewater discharged from a polyether manufacturing process by a membrane separation method. be.

(Prior art) Polyether is made by using a compound having two or more active hydrogens such as glycerin, propylene glycol, sorbitol, ethylene diamine, etc. as a base, and adding ethylene oxide, propylene oxide, butylene oxide, etc. to this in the presence of a basic catalyst. Obtained by polycondensation. The crude product thus obtained is then subjected to processes such as decatalyst removal, drying, and blending of stabilizers to become a product. Among these, the decatalyst step is to separate bases such as alkali hydroxides and alkylamines used as reaction catalysts, and a multistage countercurrent water washing method is usually used. However, 0.1 to several percent of polyether is dissolved in the separated aqueous phase (washing liquid), and it is necessary to recover these polyethers in order to improve the basic unit consumption of the polyether manufacturing industry.

These recovery methods typically involve pentane, hexane,
Extraction methods using hydrophobic aliphatic hydrocarbons such as heptane and hexene have been used. In other words, a certain proportion of polyether washing water and hydrophobic hydrocarbons are mixed and left to stand, the organic phase is separated, the hydrophobic hydrocarbons in the organic phase are separated by a separation method such as distillation, and then the polyether is recovered and recycled. I am using it. However, this method requires a complicated process, and the amount of extraction solvent used must be approximately 1 to 5 times the amount of polyether to be extracted. Usually, separation is performed by distillation, which requires a large amount of energy. I need. Furthermore, the loss of extraction solvent cannot be ignored, and this is not economically preferable. In addition, membrane separation methods using reverse osmosis membranes or ultrafiltration membranes are known as methods for recovering valuables from wastewater, but the wastewater used in the present invention is extremely basic and cannot be used for general separation. Membranes could not be used for long periods of time. We tried membrane separation after neutralization, but when using a reverse osmosis membrane,
It was found that salts generated during the neutralization reaction accumulate, causing problems in product quality.

On the other hand, when an ultrafiltration membrane is used, a certain amount of polyether is discharged into the permeated water, so it was found that as the amount of wastewater treated increases, the loss of polyether increases rapidly.

(Objective of the Invention) An object of the present invention is to provide a polyether recovery method for efficiently recovering polyether from highly basic waste water during polyether production from alkylene oxide.

(Disclosure of the Invention) The present inventors have made extensive studies to achieve the above object, and have finally completed the present invention.

That is, the present invention uses a polyether liquid when producing polyether from alkylene oxide.
The highly basic polyether-containing wastewater discharged from the liquid separation process is neutralized, the neutralized liquid is treated with a reverse osmosis membrane to concentrate it 2.0 to 10.0 times, and then further treated with an ultrafiltration membrane. A part of the salt produced by neutralization is removed, and the wastewater is concentrated in a state containing substantially most of the polyether contained in the wastewater, and the wastewater is obtained as a polyether phase and an aqueous phase. , a polyether recovery method characterized in that the concentrated wastewater is recycled to the polyether separation step.

The present invention will be explained in detail below.

The wastewater discharged from the polyether manufacturing process contains 0.1 to several percent of polyether and 0.1 to several percent.
It contains a basic substance at a high concentration of 1.0%, and in order to maintain the performance of reverse osmosis membranes and ultrafiltration membranes for a long period of time, it is necessary to neutralize the wastewater by adding acidic substances. The acidic substance to be added may be any ordinary acid, examples of which include hydrochloric acid, phosphoric acid, and acetic acid.

Here, a reverse osmosis membrane is a membrane that can substantially separate polyether in wastewater and salts generated in the neutralization process, and an ultrafiltration membrane is a membrane that can substantially separate polyether but removes low-molecular-weight salts. indicates a permeable separation membrane. The separation device may be of any type, and for example, flat membrane type, spiral type, tubular type, and fiber optic type devices are applicable.

Next, an example of the present invention will be explained with reference to FIG.

A mixed solution of polyether and washing water sent from the polyether manufacturing process is introduced into a polyether separation tank 2 through a conduit 1. The separated polyether is sent through conduit 3 to further dehydration and purification steps. On the other hand, separated water (polyether-containing wastewater) containing 0.1 to several percent polyether and 0.1 to 1.0 percent of highly concentrated basic substances is taken out from conduit 4, and is almost completely removed by adding acidic substances from conduit 5. neutralized. Further, the neutralized liquid is supplied from the conduit 6 to the reverse osmosis device 7.

The reverse osmosis device is normally operated at a pressure of 10 to 60 kg/cm ² G, and a permeate substantially free of polyether and salts is discharged via conduit 8. On the other hand, a concentrated solution in which polyether and salts are concentrated 2.0 to 10.0 times is supplied to an ultrafiltration device 10 through a conduit 9. The ultrafiltration device is normally operated at a pressure of 1 to 20 kg/cm ² G, and the concentrated water that contains most of the polyether contained in the waste water is passed through the conduit 12 into a polyether phase and water. It consists of two phases and is circulated to the polyether liquid-liquid separation tank (separation step) 2. On the other hand, from the conduit 11, permeated water whose salt concentration is approximately the same as the concentration supplied to the ultrafiltration device and which contains a trace amount of polyether is discharged. In this way, polyether can be efficiently concentrated and recovered from polyether wastewater. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 The flow shown in FIG. 1 is used.

Separated water discharged from polypropylene glycol separation tank 2 (polyether-containing wastewater) 20Kg/hr
(Polypropylene glycol molecular weight 1000-5000,
1.0%, potassium hydroxide 0.13%, PH>13)
An equivalent amount of phosphoric acid (75 percent aqueous solution) to the potassium hydroxide contained therein is continuously added through conduit 5. This neutralized liquid (polypropylene glycol 1.0%, potassium phosphate 0.3%) is 50Kg/cm ²
m ² is supplied to the reverse osmosis device 7. Further, polypropylene glycol was recovered from the bottom of the separation tank 2 through the conduit 3 to the outside of the system. Reverse osmosis device is DDS-HF40
The type (spiral type) and reverse osmosis membrane used were DDS-HR95. The permeable membrane is a system developed by DDS (DDS is the abbreviation for Denmark's De Denske Zutskärfabriker) based on the HR membrane developed by Filmtek, an American company.
A polysulfone layer was provided on a polyester support, and a separation functional layer made of aromatic polyamide was further provided on the polysulfone layer. Through conduit 9, 5 kg/hr of a concentrated solution containing 4.0% polypropylene glycol and 1.2% potassium phosphate was obtained. The polypropylene glycol in the permeate obtained from conduit 8 is less than 0.01%, and the potassium phosphate content is less than 0.01%.
It was hot. Concentrated liquid obtained from conduit 9 5Kg/Hr
is supplied to the ultrafiltration device 10 at 30°C and 20Kg/cm ² G. The ultraviolet device is DDS-HF40 type (flat membrane type),
DDS-GS90 was used as the ultrafiltration membrane. The ultrafiltration membrane had a separation functional layer made of polyvinylidene fluoride on a polypropylene support. A concentrated effluent containing 6.2% polypropylene glycol and 1.2% potassium phosphate was obtained through conduit 12 at a rate of 3.0 kg/hr. The concentrated wastewater is separated into a polypropylene glycol phase and an aqueous phase,
Polypropylene glycol separation tank (separation process) 2
It is recovered by circulating to.

On the other hand, permeated water was obtained from conduit 11 at a rate of 2 kg/hr. The polypropylene glycol in the permeate is
0.75%, potassium phosphate 1.2%, and the polypropylene glycol recovery rate was extremely high at 92%. As a result of circulating the concentrated solution, the potassium phosphate concentration was almost stabilized at 0.45%. At this time, no problem occurred in the quality of the polypropylene glycol recovered from conduit 3.

Comparative Example 1 The flow shown in FIG. 2 is an example of treatment using only an ultrafiltration membrane. A neutralized solution with the same composition as in Example 1 was used.
It was supplied to the ultrafiltration device 10 at 30° C. and 20 Kg/cm ² G through conduit 6' at 20 Kg/Hr.

The ultrafiltration device is DDS-HF40, which is the same as in Example 1.
The mold and the ultrafiltration membrane were the same DDS-
I used GS90.

Polypropylene glycol through conduit 12
Concentrate containing 4.7% and 0.3% potassium phosphate is 3.0
Kg/Hr obtained.

Meanwhile conduit 11 and more polypropylene glycol
The permeate containing 0.35% and 0.3% potassium phosphate is 17.0
Kg/Hr obtained.

Therefore, the polypropylene glycol recovery rate is 70.5
It was only %.

Comparative Example 2 The flow shown in FIG. 3 is an example of treatment using only a reverse osmosis membrane. 20% of the neutralized solution with the same composition as in Example 1
Kg/Hr was fed through conduit 6'' to reverse osmosis device 7'' at 30° C. and 50 Kg/cm ² G.

The reverse osmosis device used was a DDS-HF40 type similar to that used in Example 1, and the reverse osmosis membrane used was a DDS-HR95 similar to that used in Example 1.

Polypropylene glycol 6.6 through conduit 9″
%, 3.0Kg/concentrate containing 1.9% potassium phosphate
Hr obtained.

On the other hand, from the 8″ conduit, polypropylene glycol
0.02% potassium phosphate trace permeate is 17.0Kg/
Hr obtained.

Therefore, the polypropylene glycol recovery rate is 98%.
However, while the concentrated water was being recycled, the salt concentration in the polypropylene glycol recovered from the system through conduit 3'' increased significantly, and the product failed to meet the product specifications.

(Effects of the invention) The effects of this invention are listed below.

(1) Since membrane separation is performed after neutralizing polyether wastewater, common inexpensive membrane materials can be used.

(2) After performing one-stage concentration using a reverse osmosis membrane and reducing the amount of water processed by the ultrafiltration device, a second-stage concentration is performed using the ultrafiltration membrane, reducing the loss of polyether leaking into the permeated water. I can do it.
It also prevents salt from accumulating within the system.

(3) Separation is performed by simply applying pressure without adding a flocculant or heat to the processing solution, which greatly reduces the energy required for processing, and at the same time, the separated components are free from denatured and excess components. No contamination of impurities.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram showing an example of implementation of the present invention, and FIGS. 2 and 3 are flow sheet diagrams showing a comparative example. In the figure, 2, 2', 2''
Polyether liquid-liquid separation tank, 7, 7', 7''... Reverse osmosis device, 10, 10', 10''...
An ultrafiltration device is shown.

Claims (1)

[Claims] 1 Neutralize the highly basic polyether-containing wastewater discharged from the polyether liquid-liquid separation process when producing polyether from alkylene oxide, and treat the neutralized liquid with a reverse osmosis membrane. ~10.0
The wastewater is concentrated twice and then treated with an ultrafiltration membrane to remove some of the salts produced by neutralization, and is concentrated to a state that substantially contains most of the polyether contained in the wastewater. A method for recovering polyether, which comprises obtaining waste water consisting of a polyether phase and an aqueous phase, and circulating the concentrated waste water to the polyether liquid-liquid separation step.