JPH07155607A - Recovery and reuse method of phosphoric acid - Google Patents

Abstract

(57) [Summary] [Object] The present invention effectively removes metal ions, which adversely affect the catalytic activity, from waste phosphoric acid catalyst for reaction when producing alcohol by vapor phase hydration of olefin. However, it is an object of the present invention to provide a method for recovering and reusing phosphoric acid, in which the catalyst cost can be reduced by reusing it and the environmental pollution can be prevented and resources can be effectively used. According to the present invention, the phosphoric acid contained in the spent phosphoric acid catalyst, which has been used for a long time in the gas phase hydration reaction of olefin and has a decreased activity, is extracted with water, and the metal in the extract is then extracted. Ions are removed by an ion exchange method using a strongly acidic ion exchange resin, and this is used as phosphoric acid for the gas phase hydration reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering and reusing phosphoric acid from a spent phosphoric acid catalyst used in a gas phase hydration reaction of olefin, and more specifically, it is active for long-term use. Was removed from the aqueous phosphoric acid solution by extracting the spent phosphoric acid catalyst with reduced hydrogen content, using a strongly acidic ion exchange resin to remove metal ions, especially monovalent and divalent metal ions, by the ion exchange method. The present invention relates to a method of reusing as phosphoric acid for hydration reaction.

[0002]

2. Description of the Related Art As a catalyst for producing alcohol by vapor phase hydration of olefin, for example, mineral acids such as phosphoric acid and sulfuric acid, heteropolyacids such as silicotungstic acid and phosphomolybdic acid, tungsten oxide and silica. alumina,
Metal oxides such as niobate or zeolites are known. In industrial-scale gas phase hydration of ethylene or propylene, phosphoric acid is mainly used as a catalyst from the viewpoint of reaction activity and catalyst life. The phosphoric acid catalyst for the gas phase hydration reaction of olefin is obtained by impregnating a porous silicic acid carrier such as silica gel, diatomaceous earth, activated clay or bentonite with a phosphoric acid aqueous solution of about 40 to 80% by weight. A solid catalyst is prepared and used by packing it in a fixed bed reaction tower.

Industrial scale vapor phase hydration of ethylene or propylene using phosphoric acid catalysts usually has temperatures of about 130 to 3
00 ° C., pressure about 10 to 90 kg / cm ² G, water / olefin molar ratio about 0.2 to 2.0, space velocity of reaction gas about 5 to 50
It is carried out under reaction conditions of min ^-1 . During the operation of this reaction, a small amount of phosphoric acid constantly drips from the phosphoric acid catalyst bed along with the reaction stream (weeping). The amount of phosphoric acid carried in the phosphoric acid catalyst is reduced by this wiping and the catalytic activity is lowered. Therefore, about 3 to 15% by weight of phosphoric acid aqueous solution is usually continuously or intermittently supplied from the upper part of the reaction tower. A method of maintaining the catalytic activity for a long period of time by spraying is used.

Thus, the phosphoric acid used in the gas phase hydration process of olefins is about 40% for catalyst preparation.
~ 80 wt% phosphoric acid aqueous solution and about 3 for spraying
Two types of phosphoric acid aqueous solutions of up to 15% by weight are used. If a phosphoric acid catalyst is used for this reaction for about one year or longer, the catalyst will be agglomerated, the catalyst will be powdered, and the phosphoric acid will be supported. Change in quantity, accumulation of carbonized substances, accumulation of metal ions, physical change of physical properties of siliceous carrier, such as surface area, pore size, pore volume and crystallization, and / or silanol on the surface of siliceous carrier Since the catalytic activity is reduced in a complex manner due to the chemical change of the group (-SiOH), a new phosphoric acid catalyst must be prepared and replaced.

Among these catalyst deterioration factors, the cause of metal ion accumulation in the phosphoric acid catalyst is, firstly, alkali metal ions contained in water (ion-exchanged water) as a raw material, which is a few ppb to several tens ppb. For example, sodium and alkaline earth metal ions such as calcium and magnesium are brought into and accumulated in the catalyst bed with the reaction raw material gas over a long period of time, and secondly, equipment materials such as a furnace,
Corrosion of iron and steel used in heat exchangers and pipes, or copper used in the lining inside the reaction tower causes iron and copper to be brought into and accumulated in the catalyst bed.
Another cause is that aluminum and the like, which are relatively contained in the siliceous carrier, are gradually dissolved and accumulated in the phosphoric acid carried. Since the phosphoric acid catalyst is an acid catalyst, accumulation of metal ions, especially monovalent and divalent metal ions such as alkali metal ions and alkaline earth metal ions,
It is not preferable because it significantly inhibits the acid site which is the active site.

A waste phosphoric acid catalyst which has been used as a phosphoric acid catalyst for a gas phase hydration reaction of olefin and has a reduced activity is
After extracting from the reaction tower and neutralizing with caustic soda, etc., it is discarded as industrial waste, or old phosphoric acid in the waste phosphoric acid catalyst is extracted with water, and new phosphoric acid is added to the siliceous carrier. A method of impregnating and reusing the siliceous carrier (Japanese Patent Publication No. 53-4).
No. 7800) has been made. Phosphoric acid extracted from the spent phosphoric acid catalyst with water has a phosphoric acid concentration of about 3 to 40% by weight. During the extraction operation, suspension of powdered siliceous carrier or carbonized material is obtained. Even if the substance is removed by filtration, etc., it cannot be reused as it is from the point of view of the purity and the type and content of the metal ions contained, and it is considered that it is difficult to remove the metal ions by the conventional technique. As a result, the current situation is that they are eventually disposed of as industrial waste. However, it is not only a social requirement to prevent environmental pollution by controlling the outflow of phosphorus to the environment such as sea areas, rivers, lakes and marshes, but it is also necessary to suppress and recover the emission of these phosphoric acids from the viewpoint of effective use of resources. Reuse is desired.

As a method for removing metal ions in the phosphoric acid aqueous solution, for example, a stock solution having a composition of 80% phosphoric acid, 3% nitric acid, 2.5% aluminum and 14.5% additive is added to a phosphoric acid solution with water. A method is known in which excess aluminum dissolved and accumulated by chemical polishing treatment in a chemical polishing liquid of an aluminum material adjusted to a range of 15 to 35% by weight is removed by an ion exchange method using an ion exchange resin (Yamaguchi Teruo). "Recovery and reuse of phosphoric acid-based chemical polishing liquid", Aluminum Products, April 1991, P.2-7). In this chemical polishing liquid, in order to prevent the aluminum material from being excessively dissolved during the surface treatment, several% to several thousand ppm are previously prepared.
In addition to containing a relatively high concentration of aluminum, additives such as a suppressor are also added. Therefore, this method only needs to remove a small amount of aluminum, which is contained in the chemical polishing liquid at a relatively high concentration from the beginning, by the ion exchange method. It can be said that the aluminum ion has a slow exchange rate by the ion exchange method and is a method that skillfully applies the property that it is difficult to remove highly.

As a similar known method, there is known a method of removing iron, which is dissolved and accumulated in a chemical polishing liquid for a steel material containing phosphoric acid as a main component, by an ion exchange method using a strongly acidic ion exchange resin. (Mitsubishi Kasei Co., Ltd., "Diaion Ion Exchange Resin / Synthetic Adsorbent Manual II Application", p.
135-136, 1991). This method is basically the same as the case of the chemical polishing treatment of the aluminum material, and the iron ion in the phosphoric acid aqueous solution having a concentration of several tens wt% is originally disclosed because the ion exchange resin has a slow exchange rate. Known literatures show that for equilibrium adsorption of 0.33% by weight iron in a 7-40% by weight phosphoric acid aqueous solution on a strongly acidic ion exchange resin, it must be soaked for as long as 70 hours. ing. Therefore, this method is also a method that skillfully applies the property that iron ions in a phosphoric acid aqueous solution having a concentration of several tens% by weight are not easily removed by a strongly acidic ion exchange resin. It has been confirmed by experiments by the present inventors that iron ions or aluminum ions in a phosphoric acid aqueous solution having a concentration of about 15% by weight or more are extremely difficult to remove even by using a strongly acidic ion exchange resin.

Generally, the ion-exchange selectivity of a strongly acidic ion-exchange resin increases as the ion concentration increases and the ion valence number increases at room temperature. For example, Na ⁺ <Ca ²⁺ <Al ³⁺ <Th ⁴⁺
If the ionic valences are the same, the higher the atomic number, the higher the selectivity. For example, Li ⁺ <N
a ⁺ <Rb ⁺ <Cs ⁺ or Mg ²⁺ <Ca ²⁺ <Sr ²⁺ <Ba
The order of ²⁺ is well known to those skilled in the art (edited by Mitsubishi Kasei Co., Ltd., “Diaion Ion Exchange Resin / Synthetic Adsorbent Manual I Basic Edition”, p. 38, 1991). From such a general viewpoint, the removal of metal ions, particularly monovalent and divalent metal ions such as alkali metals and alkaline earth metals, in an aqueous phosphoric acid solution having a concentration of about 15 to 40% by weight with an ion exchange resin is not possible. As described above, since it is difficult to remove the trivalent metal ion, it is considered that the trivalent metal ion cannot be removed, and detailed studies have not been made to date. Therefore, it is considered difficult to purify the waste phosphoric acid catalyst used in the gas phase hydration reaction of olein from the aqueous phosphoric acid solution extracted with water, using an ion exchange resin to remove metal ions that adversely affect the catalytic activity. Since such phosphoric acid aqueous solution has no use, it is currently disposed as industrial waste.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a catalyst activity from a waste phosphoric acid catalyst for reaction when producing alcohol by gas phase hydration reaction of olefin is obtained. A method for recovering and reusing phosphoric acid that effectively removes metal ions that adversely affect the environment and reuses them to reduce catalyst costs, prevent environmental pollution, and effectively use resources. The purpose is to provide.

[0011]

In order to achieve the above object, the present inventors have found that various phosphoric acid aqueous solutions extracted with water from a waste phosphoric acid catalyst used in the vapor phase hydration of ethylene contain various kinds of phosphoric acid. As a result of diligent research on ion exchange removal of metal ions by a strongly acidic ion exchange resin, iron and aluminum are extremely difficult to remove at a phosphoric acid concentration of about 15% by weight or more, but relatively easily at a phosphoric acid concentration of less than about 15% by weight. Not only can it be removed, but, surprisingly, it overturns the conventional preconception and, at high concentrations of phosphoric acid concentrations of about 15-40% by weight, alkali metals such as sodium, calcium, magnesium, etc., which adversely affect the catalytic activity. It was discovered that alkaline earth metals such as the above can be easily removed using a strongly acidic ion-exchange resin, and this recovered phosphoric acid can be used as a catalyst for the olefin hydration reaction. It found that can be re-used without any trouble, has led to the completion of the present invention.

That is, the present invention provides a method for producing alcohol by gas phase hydration of olefin using a phosphoric acid catalyst,
After extracting the phosphoric acid contained from the waste phosphoric acid catalyst whose activity has been reduced for a long period of time with water, the metal ions in the extract are removed by an ion exchange method using a strongly acidic ion exchange resin. It is characterized in that it is used as phosphoric acid for the vapor phase hydration reaction.

First, the process for producing alcohol by the gas phase hydration reaction of olefin will be described with reference to FIG. The raw material olefin is compressed and supplied to the reaction tower R filled with the phosphoric acid catalyst C up to a predetermined pressure through the line 1 by the raw material gas compressor-C1. Pure water, which is the other raw material, is mixed with the unreacted olefin flow from the circulating gas compressor-C2 through the line 2 by the pure water pump P1, and the heat is exchanged with the reaction mixture flow in the heat exchanger E from the line 11. Is passed through a line 12 to be heated and evaporated to a predetermined temperature in a heating furnace F, and a reaction tower R is fed from a line 13 together with a source gas.
Is supplied to. Phosphoric acid for spraying is phosphoric acid pump P2
Through the line 3 and atomized together with the raw material mixed gas, and supplied to the upper portion of the phosphoric acid catalyst C in the reaction tower R.

The reaction mixture stream from line 4 is cooled in heat exchanger E, passed through line 5 and separated in high pressure separation tank D into unreacted olefin and crude alcohol aqueous solution. The crude alcohol aqueous solution separated in the high-pressure separation tank D is extracted through a line 7 to a distillation purification system (not shown).
The unreacted olefin stream separated in the high-pressure separation tank D is supplied to the lower stage of the absorption tower T through the line 6. Pure water is supplied from the line 8 to the upper stage of the absorption tower T and brought into contact with the unreacted olefin stream to absorb the alcohol entrained in the unreacted olefin stream. Alcohol absorbed in absorption tower T
The crude alcohol is extracted as a crude alcohol aqueous solution from the bottom of the absorption column through the line 9 to the distillation purification system. The unreacted olefin stream having absorbed the alcohol is withdrawn from the absorption tower T at the top through a line 10, and is circulated by a circulating compressor-C.
It is recompressed by 2 and mixed with pure water from line 2, heated through line 11, heat exchanger E, line 12, heating furnace F and line 13 and circulated and supplied to reaction tower R.

Next, a method for extracting phosphoric acid from the spent phosphoric acid catalyst used in the gas phase hydration reaction of the above olefin will be described. The waste phosphoric acid catalyst discharged from the reaction tower R is an acid-resistant material,
For example, the phosphoric acid is put into an extraction tank made of stainless steel or the like, and water, preferably pure water, is put to the extent that the spent phosphoric acid catalyst is sufficiently covered, and the water is circulated and stirred by using a pump or the like for about 1 to 100 hours. To extract. The first extraction yields an extracted phosphoric acid aqueous solution having a phosphoric acid concentration of about 25-40% by weight. After extracting the extracted phosphoric acid aqueous solution, add water again in the same manner to
Perform the extraction operation for the second time. Phosphoric acid concentration of about 1 in the second extraction
An extracted phosphoric acid aqueous solution of 0 to 25% by weight is obtained. Second extraction After extracting the phosphoric acid aqueous solution, a third extraction operation is performed in the same manner. Phosphoric acid concentration of about 3 to 1 in the third extraction
A 0% by weight aqueous solution of extracted phosphoric acid is obtained. Phosphoric acid in the spent phosphoric acid catalyst is usually recovered by about 90 to 95% by a total of three extraction operations, and even if the extraction number is increased more than that, the phosphoric acid recovery rate does not improve so much. The number of extraction operations is not particularly limited, but the number of extractions is preferably 1 to 3 in order to recover phosphoric acid efficiently and economically.

In the extracted phosphoric acid, usually, a small amount of a suspended substance consisting mainly of fine powder of siliceous carrier and a carbonized substance is present together with it. These suspended solids may cause various problems such as the deterioration of the resin due to the clogging of the pores of the ion-exchange resin and the reuse of the resin in the reaction system during subsequent ion-exchange treatment, such as clogging in piping and equipment. Therefore, sedimentation and / or suspension substance separation operations such as filter filtration and sand filtration are performed. Of course, if the suspended solids are very low, this separation operation is not necessary. In the phosphoric acid extracted and filtered with pure water for the first time, sodium is usually 100-500.
ppm, calcium 100 to 500 ppm, magnesium 50 to 50
0 ppm, 100 to 1000 ppm of copper, 100 to 500 ppm of iron, 100 to 500 ppm of aluminum, and other potassium, nickel, chromium, etc. are contained as metal ions of about 1 to 10 ppm.
Although depending on the water quality of the water used for the extraction treatment, the metal ion content in the extracted phosphoric acid after the second extraction is naturally lower than that in the first extraction in proportion to the decrease in the phosphoric acid concentration.

Although the metal ions contained in the phosphoric acid thus extracted and filtered are removed by ion exchange using a strongly acidic ion exchange resin, in the present invention, the extracted phosphoric acids having different phosphoric acid concentrations are individually separated. It is not limited whether the ion-exchange treatment is performed, or part or all of them are mixed and treated. Strongly acidic ion-exchange resin used in the present invention is a synthetic resin having a chemical structure obtained by introducing a sulfonic acid group (-SO ₃ H) in a three-dimensional polymer base, such as copolymers of styrene and divinyl benzene A polymer substrate into which a sulfonic acid group has been introduced is generally preferably used. The strongly acidic ion-exchange resin is packed in a fixed-bed type resin tower, made into an H-type by using an aqueous solution of dilute hydrochloric acid or dilute sulfuric acid by a conventional method, and washed with water
A flow type in which the treatment liquid is allowed to flow down from the upper portion is preferably used. The liquid flow direction in the resin regeneration treatment and the ion exchange treatment may be either a parallel flow type or an alternating current type.

The ion exchange treatment temperature may be room temperature to 120 ° C. in view of the heat resistance of the resin, but is preferably 40 ° C. or lower from the viewpoint of the life of the resin. The liquid passing velocity of the treatment liquid is the liquid space velocity (LHSV) of 0.1 to 1 shown in the following formula (1).
Ion exchange treatment is performed at 00 hr ^-1 , but the phosphoric acid concentration is 15
In the case of up to 40% by weight, LH
SV of 0.5 to 15 is suitable. When the phosphoric acid concentration is less than 15% by weight, the ion exchange rate is relatively fast, so L
HSV 0.1 to 100, preferably LHSV 1 to 50 are suitable. Liquid space velocity (LHSV) = Treatment liquid supply amount (L / hr) / Ion exchange resin filling amount (L) (1)

By the ion exchange treatment of the method of the present invention, the metal ions in the recovered phosphoric acid are removed by ion exchange. That is,
The metal ion removal rate in the case of the recovered phosphoric acid having a phosphoric acid concentration of 15 to 40% by weight, as can be seen from the examples, sodium 85 to 97%, calcium 99% or more, magnesium 99% or more and copper 99% or more. In addition, monovalent and divalent metal ions such as alkali metals, alkaline earth metals and copper that interfere with the hydration activity of olefin are ion-exchanged and removed very efficiently. On the other hand, the iron removal rate is 10-15
%, The removal rate of aluminum is 70 to 82%, and the ion exchange removal rate is low. In the case of the recovered phosphoric acid having a phosphoric acid concentration of less than 15%, sodium, calcium, magnesium and copper ions are all efficiently ion-exchanged up to 1 ppm or less. On the other hand, the iron removal rate is about 30% when the phosphoric acid concentration is about 9% by weight, the aluminum removal rate is about 80%, and the iron and aluminum removal rate is about 5% by weight. Is about 96% or more, and the ion exchange removal rate of iron and aluminum increases as the phosphoric acid concentration decreases. At a phosphoric acid concentration of about 5% by weight, most of the metal ions were removed to 1 ppm or less. The metal ion content concentration was compared with the metal ion content concentration of commercial industrial phosphoric acid after correcting the phosphoric acid concentration. Then, it is refined to almost the same level.

The phosphoric acid thus recovered and purified has a chemical oxygen demand (COD) value of 50 to 10
Although it contains 00 ppm of organic impurities mainly consisting of alcohol, when it is used for the preparation of a phosphoric acid catalyst for the gas phase hydration reaction of olefin and / or for the spray at the upper part of the reaction column, these impurities are contained. Organic impurities are not an obstacle. The first extraction-purified phosphoric acid having a relatively high phosphoric acid concentration of about 25 to 40% by weight is prepared to have a phosphoric acid concentration of about 40 to 80% by mixing with commercially available industrial phosphoric acid having a concentration of 75 to 85%. Then, it is preferably used as phosphoric acid for preparing a phosphoric acid catalyst. Of course, it may be diluted with water and used as phosphoric acid for spraying having a phosphoric acid concentration of about 3 to 15% by weight. The extracted and purified phosphoric acid from the second time onward, which has a relatively low phosphoric acid concentration of less than about 25% by weight, was diluted with water to a phosphoric acid concentration of about 3 to 15% by weight, and was used as a phosphoric acid for spraying in the upper part of the reaction tower. It is preferably used. Of course, it may be used as a phosphoric acid for preparing a catalyst by mixing it with a commercially available industrial phosphoric acid, but since the amount of the phosphoric acid in the extracted and purified phosphoric acid is low, the amount of the phosphoric acid used will be small, so from a balance point, it is suitable for spraying. It is preferable to use.

Phosphoric acid prepared by mixing the extracted and purified phosphoric acid of the method of the present invention with commercially available industrial phosphoric acid to prepare a phosphoric acid concentration of about 40 to 80% by weight and impregnating the siliceous carrier. The gas phase hydration activity of olefin as a catalyst is equivalent to the reaction activity of a phosphoric acid catalyst prepared by preparing industrial phosphoric acid at the same concentration and impregnating it on a carrier. Further, even when used as the phosphoric acid for spraying in the upper part of the reaction tower, no particular difference in the reaction operation or reaction activity is recognized between the recovered purified phosphoric acid of the method of the present invention and the commercially available industrial phosphoric acid. I can't.

[0022]

EXAMPLES Next, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Example 1] 41 m ³ of spent phosphoric acid catalyst, which was used for vapor phase hydration of ethylene for 1 year, was carried into a stainless steel phosphoric acid extraction tank until the waste catalyst was sufficiently covered. Add pure water and circulate and stir the water for 24 hours with a pump to extract phosphoric acid in the spent phosphoric acid catalyst.
3 m ³ of the first extracted phosphoric acid was obtained. Subsequently, the same extraction operation was repeated up to 3 times, and the same amount of 2nd time and 3
A second extraction of phosphoric acid was obtained. In order to prepare a sample for analysis and the next ion exchange treatment test, each extracted phosphoric acid was tested. 5B
The suspended matter was removed by filtration through filter paper. The phosphoric acid concentration, the metal ion concentration and the COD value were measured for each of the extracted phosphoric acid and the 2-fold diluted aqueous solution of the extracted phosphoric acid, and the results are shown in Table 1 below. About 94% of the phosphoric acid in the spent phosphoric acid catalyst was recovered by the three extraction operations.

[0023]

[Table-1]

[0024]

[Example 2] No. shown in Table 1 extracted and filtered in Example 1 using an ion exchange glass column filled with 50 ml of a commercially available strong acidic ion exchange resin (Diaion PK228: manufactured by Mitsubishi Kasei Co., Ltd.). ． Ion-exchange treatment was performed by flowing 500 ml each of 1 to 4 phosphoric acid aqueous solution at LHSV = 3 to 12 hr ⁻¹ , and the metal ion concentration in each ion-exchange treatment liquid was analyzed. The following Table 2 shows the liquid passing rate of each ion exchange treatment, the metal ion concentration in the ion exchange treatment liquid, and the metal ion removal rate. When the phosphoric acid concentration is 38.4% by weight, the removal rate of metal ions is 87.2% for sodium,
The calcium content is 99.5% or more, the magnesium content is 99.7%, and the copper content is 99.9%, and the monovalent and divalent metal ions contained are extremely efficiently ion-exchanged and removed. On the other hand, the iron removal rate is 12.1% and the aluminum removal rate is 70.7%, which is low in the ion exchange removal rate. When the concentration of phosphoric acid is reduced to less than 10% by weight, the removal rate of iron and aluminum increases, and when the concentration of phosphoric acid is 5.4% by weight, the removal rate of iron is 96.3% or more and the removal rate of aluminum. The ion exchange removal rate increases to 96.1% or more, any metal ions analyzed are removed to 1 ppm or less, and the metal ion content is almost equal to that of commercial industrial phosphoric acid. For reference, the Japanese Industrial Standard for Industrial Phosphoric Acid (JIS
K1449-1978) is shown in Table 3 below.

[0025]

[Table-2]

[0026]

[Table-3]

[0027]

[Example 3] A commercially available 75% by weight industrial phosphoric acid was mixed with the recovered purified phosphoric acid having a phosphoric acid concentration of 38.4% by weight subjected to the extraction ion exchange treatment in Example 2 to adjust the phosphoric acid concentration to 55% by weight. Then, a commercially available spherical silica gel (CARiACT-
10: Impregnated with Fuji Silysia Chemical Ltd.) and dried at 110 ° C. to prepare 500 ml of phosphoric acid catalyst. This was filled in a tantalum-lined stainless steel reaction tube having an inner diameter of 34 mmφ, and the temperature was 270 ° C. and the pressure was 6
When the reaction was carried out at 0 kg / cm ² G, a water / ethylene molar ratio of 0.6, and a space velocity of 28 min ^-1 , the single-pass conversion of ethylene to ethanol was 6.4%. This has the same reaction activity as the phosphoric acid catalyst prepared in the same manner from the commercially available 75 wt% industrial phosphoric acid of Comparative Example 1, and the catalyst prepared from the extracted phosphoric acid before the ion exchange treatment of Comparative Example 3. The activity is 20% higher than the reaction activity of.

[0028]

Comparative Example 1 Commercially available 75% by weight industrial phosphoric acid was mixed with pure water to prepare a phosphoric acid concentration of 55% by weight, which was impregnated with commercially available spherical silica gel in the same manner as in Example 3 at 110 ° C. It was dried to prepare 500 ml of phosphoric acid catalyst.
When this was filled in the same reaction tube as in Example 3 and reacted under the same conditions as in Example 3, the single-pass conversion of ethylene to ethanol was 6.4%.

[0029]

Comparative Example 2 A waste phosphoric acid catalyst used in the gas phase hydration reaction of ethylene used in Example 1 for one year was screened for powder using a 10-mesh sieve. When the reaction tube was filled and reacted under the same conditions as in Example 3, the single-pass conversion of ethylene to ethanol was 4.1%.

[0030]

Comparative Example 3 The extracted phosphoric acid having a phosphoric acid concentration of 38.4 wt% before the ion exchange treatment extracted in Example 2 was mixed with a commercially available 75 wt% industrial phosphoric acid to a phosphoric acid concentration of 55 wt%. It was adjusted, impregnated with commercially available spherical silica gel in the same manner as in Example 3, and dried at 110 ° C. to prepare 500 ml of a phosphoric acid catalyst. When this was filled in the same reaction tube as in Example 3 and reacted under the same conditions as in Example 3, the single-pass conversion of ethylene to ethanol was 5.3%.

[0031]

[Function] During ion exchange of metal ions in a phosphoric acid aqueous solution using a strongly acidic ion exchange resin, the ion exchange selectivity of iron or aluminum in a highly concentrated phosphoric acid aqueous solution has been considered to be the "ion valency". The higher the ion, the greater the ion selectivity, and if the valence is the same, the higher the atomic number, the greater the ion selectivity. ”
The opposite tendency is shown that iron or aluminum easily forms an anion complex with phosphoric acid in high-concentration phosphoric acid, and therefore ion exchange removal is possible even with a strongly acidic ion exchange resin. It seems impossible. On the other hand, since sodium, calcium, magnesium, copper, etc., which have a great influence on the reaction activity of the phosphoric acid catalyst, do not form a complex with phosphoric acid, it is considered that the higher the ion valence, the greater the ion selectivity. . It was found that the accumulation of metal ions, especially monovalent and divalent metal ions, which is one of the causes of deterioration of the phosphoric acid catalyst in the gas phase hydration of olefin, has a great influence on the reaction activity even in a small amount. It is considered that the phosphoric acid catalyst functions as an acid catalyst, and the monovalent and divalent metal ions strongly poison the acid site which is the active site.

[0032]

[Effect] According to the method of the present invention, the phosphoric acid in the spent phosphoric acid catalyst, which has been conventionally treated as industrial waste, is recovered and reused by using a simple and inexpensive facility called ion exchange treatment. Therefore, the catalyst cost for producing alcohol by gas phase hydration of olefin is 1/2 to
In addition to being able to reduce it to 1/3, it has many advantages such as being economical and meeting the requirements for resource saving, and suppressing the emission of phosphoric acid to the environment, thus preventing environmental pollution.

[0033]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a process for producing alcohol by gas phase hydration of olefin.

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Claims (4)

[Claims] 1. When producing alcohol by vapor phase hydration reaction of olefin using a phosphoric acid catalyst, the phosphoric acid contained in the spent phosphoric acid catalyst whose activity has been reduced due to long-term use is extracted with water. After that, the metal ions in the extract are removed by an ion exchange method using a strongly acidic ion exchange resin, and this is used as the phosphoric acid for the gas phase hydration reaction. How to Use. 2. The method for recovering and reusing phosphoric acid according to claim 1, wherein the metal ions are monovalent and divalent metal ions which adversely affect the reaction activity of the phosphoric acid catalyst. 3. The phosphoric acid concentration in the phosphoric acid extract is 15 to
The method for recovering and reusing phosphoric acid according to claim 1, which is 40% by weight. 4. The phosphoric acid concentration in the phosphoric acid extract is 3 to 1.
The method for recovering and reusing phosphoric acid according to claim 1, which is 5% by weight.