JPS5840931B2 - Method for producing alcohols - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing lower alcohols, which comprises hydrating lower olefins in an aqueous solution containing a chromium compound, phosphoric acid and germanotungstic acid.

Methods for producing alcohols by direct hydration of lower olefins include liquid phase methods and gas phase methods, both of which use acidic catalysts.

Compared to the gas phase method, the liquid phase method can use lower purity and cheaper olefin raw materials, and alcohol can be obtained at a higher conversion rate.
Moreover, it has great advantages such as low utility consumption.

However, since the strongly acidic catalyst is used as an aqueous solution under high temperature and high pressure conditions, there are problems such as significant corrosion of equipment materials and deterioration of the catalyst due to corrosion products.

For example, although phosphoric acid is known to have high hydration activity as a catalyst, it is highly corrosive in an aqueous solution state.

That is, phosphoric acid has not yet been industrially employed as a catalyst in a liquid phase process because there is no suitable corrosion-resistant material and no anti-corrosion method that is effective at high temperatures and in a strongly reducing atmosphere.

The present inventors have previously conducted extensive studies on a method for producing lower alcohols by liquid-phase hydration of lower olefins, and have disclosed an effective anticorrosion method for hydrating lower olefins in an acidic aqueous solution of phosphoric acid.

That is, it was discovered that dissolved chromium compounds are effective as anticorrosive agents (1) from oxyacids, oxyacids, oxides, and hydroxides of chromium, molybdenum, tungsten, and antimony, as well as nitrite and nitrate ions. phosphoric acid in an acidic aqueous solution containing one or more compounds selected from the group consisting of (JP-A-52-89604), and (2) phosphoric acid containing a chromium salt and/or a chromium complex compound. This is a method of hydrating lower olefins in an acidic aqueous solution.

These methods have the following characteristics: (1) They exhibit great corrosion prevention effects at high temperatures.

(2) It exhibits a remarkable anticorrosion effect even in a strongly reducing atmosphere where olefins and alcohols are present.

(3) Great anticorrosion effects can be obtained just by adding a small amount of anticorrosion agent.

However, even in these methods, the anticorrosive agent settles due to iron ions that dissolve and accumulate due to slight corrosion.

As a result, there are problems such as a reduction in the anticorrosive effect and the possibility of clogging of reactors and heat exchangers due to precipitates.

In order to solve these problems, there is a method of removing iron ions, but this method inevitably requires complicated operations.

Taking these circumstances into consideration, the inventors of the present invention have conducted repeated research in search of a catalyst system that can further suppress corrosion in the liquid phase hydration reaction of lower olefins and maintain a sufficient reaction rate even at the lowest possible temperature. , arrived at the present invention.

That is, the method of the present invention is a method for producing the corresponding alcohol by hydrating a lower olefin in an acidic aqueous solution containing a chromium compound, phosphoric acid, and germanotungstic acid.

According to the method of the present invention, (1) Corrosion of equipment materials is significantly suppressed by adding germanotungstic acid in an appropriate concentration range to a dilute aqueous solution of phosphoric acid, and the corrosion is less than when no addition is made.

That is, when germanotungstic acid in a concentration range of 0.5 to 2 wt% is added to an aqueous solution containing phosphoric acid adjusted to a concentration range of 0.5 to 2 wt%, corrosion is reduced.

Normally, it is expected that adding another strong acid to an aqueous phosphoric acid solution will increase the acidity and corrode the equipment materials.However, in the method of the present invention, the addition of germanotungstic acid, a strong acid, Corrosion is suppressed despite increased acidity.

(2) In addition to the fact described in (1) above, the presence of a dissolved chromium compound significantly improves the anticorrosion effect.

Although the mechanism of this corrosion protection is not clear, it is believed that the dissolved chromium compound has a chromium ion as the central atom, and combines with phosphate anions, hydrogen phosphate anions, germanotungsten acid anions, etc., to form an aco complex. is expected.

This complex appears to act on the walls of the equipment and is effective in inhibiting corrosion.

(3) The coexistence of phosphoric acid significantly improves the stabilization of germanotungstic acid.

In general, when heteropolyacids are used in a reducing atmosphere such as in a direct olefin hydration reaction using a liquid phase method and at high temperatures at a high concentration as in the method of the present invention, they are significantly decomposed and deteriorated.

However, due to the coexistence of phosphoric acid, germanotungstic acid becomes extremely stable and does not lose its catalytic activity even after repeated use over a long period of time.

Furthermore, although it is said that heteropolyacids significantly lose their catalytic activity in the presence of trace amounts (10 ppm or more) of iron ions, in the catalyst system of the present invention, germanotungstic acid is catalytic even in the presence of 100 ppm of iron ions. Sufficient reaction rate can be maintained without loss of activity.

(4) Since the catalyst system of the present invention has extremely high hydration activity, a relatively low temperature range can be used as the condition for olefin hydration by the liquid phase method, and alcohols can be produced advantageously in terms of chemical equilibrium.

For example, in the production of isopropyl alcohol by propylene hydration using the industrially implemented liquid phase method, 240 to
Although the temperature range is 270°C, (catalyst vol.
18.46.180 to 184.1976), and in the present invention, high reaction rates can be obtained even at relatively low temperatures of 200 to 240°C.

As a result, direct hydration of propylene becomes advantageous in terms of chemical equilibrium, corrosion of equipment materials is alleviated, and side reactions such as propylene polymerization can also be suppressed.

Furthermore, (5) corrosion of equipment materials can be significantly reduced, so the concentration of dissolved and accumulated iron ions is reduced, and precipitation of the anticorrosive agent due to iron ions is extremely reduced.

Therefore, the anticorrosion effect is further enhanced and there are almost no problems with the equipment due to sediments.

The concentrations of phosphoric acid and germanotungstic acid used in the method of the present invention are adjusted to a range of 0.5 to 2.0 wt%.

Particularly preferably, the content is in the range of 0.5 to 1.5 wt%.

Outside this concentration range, alcohols can no longer be effectively produced.

That is, if the amount is less than 0.5 wt%, sufficient olefin hydration activity cannot be obtained.

On the other hand 2. If the content exceeds Owt%, corrosion of the equipment material becomes significant, which deteriorates the catalyst and increases mechanical loss, which is economically disadvantageous.

Any chromium compound used in the method of the present invention is effective as long as it is soluble in an acidic aqueous solution of phosphoric acid and germanotungstic acid.

For example, chromium salts such as chromium phosphate, chromium nitrate, chromium carbonate, chromium oxalate, and chromium sulfate; chromic acids such as sodium chromate, potassium chromate, chromic anhydride, sodium dichromate, and potassium dichromate; Preferred are chromium complex compounds such as chromate and dichromate, tetraacodiamine chromium sulfate, tripotassium hexaaminochromate, and chromium hydroxide.

The above-mentioned compound may be added directly to the phosphoric acid and germanotungstic acid aqueous solution of the catalyst solution, but in advance,
It may be added to an aqueous solution of phosphoric acid or an aqueous solution of phosphoric acid and germanotungstic acid with a higher concentration than the catalyst solution, heated to completely dissolve it, and this solution may be diluted for use.

In addition, after adding it to the phosphoric acid aqueous solution or the phosphoric acid and germanotungstic acid aqueous solution as described above, lower alcohols etc. are added and heated to dissolve the chromium compound.At the same time, if the added chromium compound is hexavalent. may be used after reducing hexavalent chromium to trivalent chromium.

The amount of chromium compound used is 1 to 110 chromium atoms.
A concentration range of 0.00 pp is suitable.

Even if more than this is added, there is no change in the anticorrosive effect, and it cannot be said to be economically advantageous.

Particularly preferred concentrations are in the range 1 to 500 ppm.

When the aqueous solution prepared to contain the chromium compound, phosphoric acid, and germanotungstic acid used in the method of the present invention is used at a high concentration within the above concentration range, side reactions such as olefin polymerization may be promoted. In cases where there is a risk of reducing the selectivity of alcohols, the pH of this aqueous solution should be adjusted to a range of 1.4 to 2.4 to suppress side reactions and maintain a good olefin consumption rate. I can do it.

Outside this range, that is, when the pH is lower than 1.4, olefin polymerization becomes noticeable, and when the pH is higher than 2.4, a sufficient reaction rate cannot be maintained.

In order to maintain the aqueous solution in such a suitable pH range, soluble basic substances such as NaOH, Al (OH
) 3, Mg(OH)2, Zn(OH)2, MgO,Z
Metal hydroxides or metal oxides such as nO can be added.

In addition to the above-mentioned compounds, all compounds that are soluble and can maintain a pH of 1.4 to 2.4 are effective.

Furthermore, the pH can be adjusted to 1.4 to 2.4 by dissolving a soluble salt of phosphoric acid and/or a soluble salt of germanotungstic acid in an acidic aqueous solution of phosphoric acid and germanotungstic acid.

The lower olefins used in the method of the present invention are ethylene,
These are propylene and butenes, and the alcohols are alcohols obtained by the hydration reaction of the above-mentioned olefins.

The method of the present invention is particularly effective in producing isopropyl alcohol by hydrating propylene.

The above-mentioned lower olefins are brought into contact with an aqueous solution containing a chromium compound, phosphoric acid and germanotungstic acid prepared as above, and a known batch or continuous direct hydration process is carried out under the above-mentioned reaction conditions. By using a reaction apparatus, the corresponding alcohols can be easily produced.

The reaction temperature is preferably in the range of ioo to 300°C, but an appropriate temperature can be selected depending on the olefin used.

For example, 240-280°C for ethylene, 200-240°C for propylene, 150-280°C for butenes.
40°C is generally preferred.

The reaction pressure must be such that the aqueous catalyst solution exists in a liquid state at the applied temperature, that is, the pressure must be higher than the saturated vapor pressure, but in order to obtain a sufficient reaction rate, a high pressure is generally required. A range of 300 kg/CrAG is preferred.

In order to carry out the reaction efficiently, a general-purpose absorption tower is used to effectively bring the aqueous catalyst solution and olefins into contact in co-current or counter-current flow, firstly separating unreacted olefins from the reaction liquid flowing out from the reaction tower, and then Alcohols are separated by distillation, extraction, etc.

By collecting the aqueous catalyst solution and circulating it to the reaction tower, it can be used repeatedly and stably without separating the catalyst.

In the method of the present invention, general-purpose stainless steel is sufficient as the equipment material usually used, but the chromium content is 30 to 2.
Particularly preferred is stainless steel with a nickel content of 0 wt% and a nickel content of 25 to 10 wt%.

Furthermore, stainless steel containing components that improve corrosion resistance, such as molybdenum, tantalum, and niobium, is also a preferred material.

As described above, since the present invention has many features, alcohols can be produced very effectively and economically advantageously when carried out industrially.

For example, (1) when producing alcohols by flowing a catalyst aqueous solution and an olefin in a reactor, relatively low temperature conditions can be used, so the alcohol concentration in the reaction solution increases in equilibrium.

Therefore, the circulation amount of the catalyst aqueous solution can be reduced, so that the utility consumption such as electric power and water vapor can be greatly improved.

(2) Due to the low temperature conditions and the effect of the anticorrosive agent, there is very little corrosion of the equipment materials, so maintenance is easy.

(3) Since the stability of germanotungstic acid is significantly improved by I nonacid, there is almost no catalyst deterioration and the catalyst consumption rate is good.

(4) Since inexpensive stainless steel can be used as the equipment material, there are significant economic effects such as lower construction costs.

Next, the present invention will be specifically explained using Examples and Reference Examples.

Reference Example 1 1. Germanotungstic acid (Gem2-12W03-30H20) was added to a phosphoric acid solution with an Owt% concentration, and an aqueous catalyst solution was adjusted so that the concentration was 0.5wt%.

At this time, the pH of the solution was 1.58.

On the other hand, test pieces for corrosion tests were insulated and fixed with a Teflon sheet to the stirring rod of a tantalum autoclave containing 5001 nl so as not to come into contact with each other.

Charge 300ml of the above test solution into this autoclave,
The space inside the autoclave was purged with nitrogen gas and filled with nitrogen.

The mixture was rapidly heated and raised while stirring, and when the temperature reached 230°C, propylene gas was supplied, and the pressure was adjusted to 200 kg/c4fG) while carrying out a hydration reaction.

When a corrosion test was conducted for 120 hours at 230°C and 200 kgycrr; t, q, the concentration of isopropyl alcohol produced in the reaction solution was 13 wt%, and 5
S-304,5uS-316 and SuS2310S
The corrosion rates were 0.85 mm/year, 9.55 m1/year and 0.07 mm/year, respectively.

In addition, when carried out for 100 hours under the above conditions without adding germanotungstic acid (at this time (7) PH 1,65), 5uS-304, 5uS-316 and SuS-
The corrosion rate of 31OS is 1.75mm/year and 1.3, respectively.
7 m1/year and 0.21 ton/year.

As described above, although the acidity has increased from PH1.65 to PH1.58 by adding germanotungstic acid to the phosphoric acid aqueous solution, corrosion of the material is not small.

Example 1 Test pieces of 5uS-304 and 5uS-316 were placed in a stirring rod of a 300ml zirconium autoclave so that they were insulated from each other.10wt% of chromium phosphate containing 10ppm of chromium atoms
phosphoric acid and 1. Owt% germanotungstic acid hydroxide aqueous solution 00rrLl/Ar, propylene 90f/
Continuously supplied at a rate of hr, rapidly stirred and heated,
The reaction was carried out while controlling the temperature to 230° C. and the pressure to 200 kg/cAG).

While continuously extracting unreacted propylene from the reaction solution,
The reaction was allowed to proceed for 24 hours.

After the reaction was completed, the test pieces were taken out from the autoclave and the corrosion rates of 5uS-304 and 5uS-316 were determined to be 0.02 mm/year and 0.015 yxi/year, respectively.

At this time, when the extracted liquid was analyzed using a gas chromatograph, the concentration of inpropyl alcohol was 11.4 wt%.
, and some isopropyl ether and acetone were produced.

In addition, analysis of chromium atoms in the extracted liquid revealed that 1
0 pp stones were present, and no consumption of chromium phosphate was observed.

On the other hand, when conducted for 24 hours under the above conditions without adding germanotungstic acid, 5uS-304, 5uS-3
The corrosion rates of 16 are 0.08ii/year and 0.05ii/year, respectively.
It was the year.

Example 2 20 ppm of an anticorrosive agent as chromium atoms was added to a phosphoric acid aqueous solution with a concentration of 1.0 wt%, and a material corrosion test was carried out using the method described in Example 3 using a catalyst aqueous solution whose germanotungstic acid concentration and pH were adjusted. It was carried out by

The results are shown in Table-2. Example 3 300rfLl of an aqueous solution in which phosphoric acid and germanotungstic acid containing iopm of anticorrosive agent as chromium atoms were adjusted to the concentration range of the present invention was charged into a 500TLl tantalum autoclave, and rapidly stirred and heated to reach a predetermined temperature. Incidentally, the stability of germanotungstic acid was tested for a predetermined period of time while supplying an olefin and performing a hydration reaction.

Germanotungstic acid in the reaction solution was measured by polarographic analysis to determine its decomposition rate.

The results are shown in Table-2.

For comparison, the results when phosphoric acid and anticorrosion agent were not added are also shown.

Example 4 1,O containing 20 ppm of corrosion inhibitor as chromium atoms
Germanotungstic acid was added to a phosphoric acid aqueous solution with a wt% concentration to a concentration of 1.0 wt%, and the direct hydration reaction of the lower olefins listed in Table 3 was carried out in the same manner as described in Reference Example 1. did.

The results are shown in Table 3.

Claims (1)

[Scope of Claims] 1. When producing lower alcohols by hydrating lower olefins in an aqueous solution, a lower olefin characterized in that the lower olefins are hydrated in an aqueous solution containing a chromium compound, phosphoric acid, and germanotungstic acid. Method for producing alcohol. 2 The concentration of the chromium compound, phosphoric acid and germanotungstic acid in the aqueous solution is 0.0001 to 0.1, respectively.
wt% (concentration as chromium), 0.5-2wt
% and 0.5 to 2 wt%. 3. The method according to claim 1, wherein the aqueous solution containing the chromium compound, phosphoric acid, and germanotungstic acid has a pH in the range of 1.4 to 2.4.