JP2756736B2 - Method for purifying hydrogen-containing CO gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying hydrogen-containing CO gas and a method for producing acetic acid using purified CO gas obtained by the method.

[0002]

2. Description of the Related Art Conventionally, as a hydrogen-containing CO gas as a raw material for producing acetic acid, a so-called synthesis gas obtained by a partial combustion reaction, a steam reforming reaction or the like using coal, petroleum, natural gas, or the like has been used. It is known to be used, this synthesis gas usually containing 20 to 60% by volume of hydrogen.

Conventional methods for purifying the hydrogen-containing CO gas include a membrane separation method, a copper ammonia method, and COSORB.
Method, cryogenic separation method, adsorption method utilizing carbon selective adsorption of adsorbent obtained by impregnating activated alumina with carbon and supporting CuCl and CuCl ₂ , that is, hydrogen-containing CO such as PSA (pressure swing adsorption method) Methods for removing hydrogen from gas are known, but it has been difficult to remove even trace amounts of hydrogen by any of the methods.

For example, Japanese Patent Publication No. 60-43767 discloses a catalyst for carbonylation of alcohol comprising nickel or cobalt or a compound thereof supported on a carbonaceous carrier, and further comprising a catalyst comprising the catalyst and an iodine compound cocatalyst. A method for producing acetic acid by reacting methanol and carbon monoxide in a gas phase is disclosed. However, the use of a hydrogen-containing CO gas, a so-called synthesis gas, as a raw material is not specifically described, but its effects are also described. There is no description enough to confirm
The selectivity and yield of the acetic acid obtained are also low and not satisfactory.

[0005] Chemistry Letters
ers), pp. 895-898, 1987, on the effect of accelerating hydrogen in the gas-phase carbonylation reaction of methanol in the presence of a nickel catalyst supported on activated carbon, the yield of acetic acid with an H ₂ / CO ratio of 0. It is reported that the maximum value is reached when the ratio is 1 or more, and carbon monoxide and hydrogen are present in an amount of H ₂ / CO ratio of 0.1 or more as compared with the case where carbon monoxide containing no hydrogen is used. As a result, the yield of acetic acid has been improved, but is not yet satisfactory.

[0006] Proceedi of Ninth International Catalysis Congress
ng of 9th International Catalysis Congress), vol.
3, p 1051-1058 (1988), that the activated carbon-supported rhodium metal catalyst has excellent activity in the production of acetic acid by the carbonylation reaction of methanol and, for example, 523 ° K, 11 atm, W / F = 5 g · h / mol (Rh: 1 g · h / mol) and CO / MeOH / Me
It is taught that the coexistence of hydrogen under the condition of I / H ₂ = 50/9/1 / (19) (mol) improves the activity of the acetic acid formation reaction as compared with the case without coexisting hydrogen. The details of the effect of the coexistence of the catalyst and hydrogen are not disclosed.

Japanese Patent Publication No. 47-3334 discloses a method for producing acetic acid in high yield by carbonylation of methanol in a liquid phase using a rhodium complex catalyst and methyl iodide or hydrogen iodide as an accelerator. However, it has disadvantages such as the fact that the reaction system is extremely corrosive and requires expensive corrosion-resistant materials, a special process is required for separating the product and the catalyst, and there are many by-products of methane. The use of hydrogen-containing CO gas, a so-called synthesis gas, as a raw material has neither a specific description nor a description sufficient to confirm its effect.

Conventionally, for example, in the synthesis of ammonia or the like, when a mixed gas of CO gas and hydrogen gas and the hydrogen gas content is as high as 99% by volume or more, at a relatively low temperature in the presence of a nickel catalyst or the like. It is known that the methanation reaction proceeds.

However, when a conventionally known catalyst such as a nickel catalyst is used when the content of CO is high and the content of hydrogen is low, carbon is precipitated due to decomposition of CO, the yield of CO decreases, and the Deterioration and clogging of the reactor occur, nickel catalysts cause sublimation due to formation of nickel carbonyl, and CO is strongly adsorbed on the catalyst surface to hinder the reaction.

The present invention provides a method for purifying a hydrogen-containing CO gas which does not precipitate carbon, does not cause sublimation due to the formation of a carbonyl compound, and can remove a very small amount of hydrogen in a CO gas containing a relatively small amount of hydrogen. And a method for producing acetic acid with high selectivity and high yield in which the corrosiveness of the reaction system is significantly reduced in a simplified production process using purified CO gas obtained by the method. It is the purpose.

The present invention relates to platinum, palladium and rhodium.
A hydrogen-containing CO gas is introduced into a reactor filled with a catalyst in which a platinum group metal selected from the group consisting of A method for purifying hydrogen-containing CO gas, which comprises removing hydrogen contained in the gas by the method.
You . The purified CO gas obtained by the method is obtained by converting the purified CO gas having a hydrogen content of 2% by volume or less to a carbonaceous carrier rhodium metal catalyst and a methyl iodide promoter.
It is used in a method for producing acetic acid, which comprises reacting with methanol in a gas phase .

The hydrogen-containing CO gas used in the hydrogen-containing CO gas purification method of the present invention includes, for example, coal, petroleum,
A so-called synthesis gas obtained by partial combustion, steam reforming reaction, or the like using natural gas, having a hydrogen content of 20 to 75% by volume, or obtained by reducing CO ₂ with hydrogen, Those having a content of 5 to 75% by volume are exemplified. The high-concentration hydrogen may be removed to some extent in advance by a hydrogen removal method such as a membrane separation method, a copper ammonia method, a COSORB method, or a PSA method.

[0013] The method for purifying hydrogen-containing CO gas in the present invention is a method of purifying a hydrogen-containing CO gas in a reactor filled with a catalyst comprising a platinum group metal, preferably platinum, supported on a heat-resistant carrier, preferably a gamma-alumina carrier. This is a method in which CO gas is introduced and a methanation reaction is performed catalytically to remove hydrogen in the hydrogen-containing CO gas.

The catalyst used in the hydrogen-containing CO gas refining method of the present invention may be appropriately selected from known catalyst production methods, and usually includes an impregnation method, a deposition method, an immersion method, an ion exchange method, a vapor deposition method, and a kneading method. After the platinum group metal is supported on the heat-resistant carrier, the temperature is 50 to 200 ° C., preferably 80 to 1 ° C.
A drying operation for evaporating water at 20 ° C. is performed,
After firing at 800 ° C., preferably 300 to 600 ° C., the firing is further performed at 100 to 700 ° C., preferably 200 to 5 ° C.
It is manufactured by a method of performing a hydrogen reduction treatment of reducing a catalyst by flowing a hydrogen-containing gas at 00 ° C. For the reduction, solution reduction with hydrazine, formalin and alkali can also be performed. In the case of the solution reduction, after the drying operation, the process may be shifted to the solution reduction without performing the firing. In addition, as the platinum group metal reagent used in the impregnation method or the like, chloride, nitrate, hydroxide, tetrachloroplatinic acid (II) (IV), platinum black and the like can be used. In the case of platinum, tetrachloroplatinic acid (IV) is preferred. Further, since the catalyst reduction is performed during the purification of the CO gas, the reduction treatment is not necessarily required.

The platinum group metals used in the method for purifying hydrogen-containing CO gas of the present invention include platinum, haradium and the like .
And rhodium , with platinum being particularly preferred.

The heat-resistant carrier used in the method for purifying hydrogen-containing CO gas of the present invention includes gamma-alumina, alpha-alumina, activated carbon, zeolite, silica, silica-alumina, titania, zirconia, and magnesia. Gamma alumina is particularly preferred.

The methanation reaction in the method for purifying hydrogen-containing CO gas of the present invention is carried out, for example, at a reaction temperature of 150 to 550 ° C.
Preferably 200-500 ° C, reaction pressure 0-200kg
/ Cm ² · G, ² · preferably 0~100kg / cm
G, W / F 0.1 to 100 g · h / mol, preferably 1
The reaction is performed under the conditions of 30 g · h / mol. However, the reaction pressure is not particularly limited and is preferably higher, but may be reduced.

In the method for purifying hydrogen-containing CO gas of the present invention, the purified CO gas obtained by the method can be used as a raw material for producing acetic acid. In this case, the hydrogen content is 2% by volume or less, preferably 1% by volume or less. It is necessary to purify to below volume%.

[0019] Examples of the carbonaceous carrier used carbonaceous support rhodium metal catalyst in the production of acetic acid method, activated carbon, carbon black, silica and other carrying carbonaceous in such coke, alumina, inorganic carriers such as zeolites mentioned Of these, activated carbon is preferred.

The carbonaceous support rhodium metal catalyst used in the acetic acid production process, typically impregnation method, after deposition method, a dip, a vapor deposition method, the Rh due kneading method was supported on a carbonaceous carrier, 50 to 200 ° C. , Preferably 80 to 120
Perform a drying operation to evaporate water at a temperature of 100 ° C.
It is manufactured by a method in which a hydrogen-containing gas is passed at 700 ° C., preferably 200 to 400 ° C. to perform a hydrogen reduction treatment for reducing the catalyst. For the reduction, solution reduction with formalin and alkali can also be performed. In addition, R used in the impregnation method
As the reagent h, rhodium chloride, sodium rhodate, ammonium rhodate, rhodium hydroxide and the like can be used. Particularly, rhodium chloride is preferred. Also,
Since the catalytic reduction is performed during the production of acetic acid, a reduction treatment is not always necessary.

[0021] The amount of methyl iodide promoter in the acetic acid production process, is not particularly limited, 0.1 to 50 mol relative to normal methanol 100 moles, preferably 1 to 20 mols is there. As the promoter, an iodine compound which produces methyl iodide in a device by reacting with methanol instead of methyl iodide, for example, iodine;
Hydrogen iodide and the like can also be used.

The catalytic reaction in the production of acetic acid method, the presence of the carbonaceous support rhodium metal catalyst and the methyl iodide promoter, methanol and hydrogen content 2% by volume, preferably a 1% by volume or less of CO gas , Methanol and C
Use ratio with O gas, CO: methanol molar ratio = 1: 1
00 to 100: 1, preferably 1:10 to 10: 1, reaction temperature 100 to 400 ° C, preferably 150 to 300
° C, reaction pressure 0.1-300 atm, preferably 1-10
The reaction is carried out in a gas phase under the conditions of 0 atm and W / F of 0.1 to 500 g · h / mol, preferably 1 to 30 g · h / mol.

The presence of water and methane as impurities in the hydrogen-containing CO gas does not hinder the catalytic action. If the reaction temperature exceeds 400 ° C., the amount of methane produced is undesirably increased. The reactor used for the catalytic reaction in the method of the present invention is not particularly limited, and may be any of a fixed bed, a fluidized bed and a moving bed.

The reaction between methanol and CO gas basically generates methyl acetate and water once, and further reacts the methyl acetate with water to form acetic acid and methanol, and the generated methanol is used as a raw material. However, when hydrogen coexists under the above reaction conditions, methyl acetate and hydrogen react with each other to produce methane at the same time as acetic acid, thereby lowering the yield of acetic acid. On the other hand, when hydrogen coexists, methyl iodide as a promoter reacts with hydrogen to cause decomposition of methyl iodide,
In addition to inhibiting the acetic acid production reaction, iodine and hydrogen iodide, which are methyl iodide decomposition products, are corrosive and cause corrosion of production equipment.

The flow chart of an example of the acetic acid production process is as FIG.

[0026]

FIG. 2

[0027]

According to the method for purifying hydrogen-containing CO gas of the present invention, there is no precipitation of carbon, no sublimation due to the formation of carbonyl compounds, and a very small amount of hydrogen in CO gas containing a relatively small amount of hydrogen. It is possible to obtain purified CO gas suitable as a raw material for producing acetic acid. Incidentally, the purified CO gas obtained in the method of the present invention, for example, by the carbonylation reaction of PhNO ₂ PhN
It can also be used when coexistence of hydrogen is not desirable, such as in the case of producing HCO ₂ R. According to the acetic acid production process, coupled with the use of the above purification CO gas,
(1) The consumption of methyl iodide as a promoter is reduced, the acetic acid production reaction is not hindered, and there is no by-product of iodine and hydrogen iodide, and corrosion of the production equipment is prevented. 2) the amount of by-products of methane is reduced, so that when recovering unreacted CO gas from the product, the recovered gas contains only a small amount of methane and can be reused as a raw material without a methane separation operation; and (3) The effect of being able to produce acetic acid with high selectivity and high yield is obtained together with the above advantages.

[0028]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

Example 1 Gamma-alumina 25 sized to 20-42 mesh
g was weighed. Next, chloroplatinic acid was weighed so as to carry 1% by weight of platinum, and dissolved in water to obtain a 25 cc aqueous solution. Immerse gamma alumina in this aqueous solution,
Evaporate and dry on a hot water bath using a rotary evaporator. After calcination at 500 ° C., hydrogen reduced at 400 ° C. for 2 hours was used as a 1 wt% Pt / Al ₂ O ₃ catalyst.

11.3 g of the obtained Pt / Al ₂ O ₃ catalyst
Into a 10 mm diameter reaction tube of a fixed bed flow type reactor,
CO gas containing 1% by volume of hydrogen was passed through the catalyst layer at a rate of 15 g · h / mol (W / F (catalyst weight divided by gas flow rate)), and the methanation reaction was conducted under the conditions shown in Table 1. Was performed to reduce the hydrogen content in the hydrogen-containing CO gas, and the results shown in Table 1 were obtained.

Examples 2 to 3 In the same manner as in Example 1, a Pd / Al ₂ O ₃ catalyst (Example 2) and a Rh / Al ₂ O ₃ catalyst (Example 3) were obtained. Example 1 under the conditions shown in Table 1.
The same experiment was performed. Table 1 shows the obtained results.

Example 4 An activated carbon carrier Rh catalyst was prepared in the same manner as in Example 1 except that activated carbon was used as the carrier and the calcination step was omitted. The same experiment as in Example 1 was conducted using the catalyst under the conditions shown in Table 1. Table 1 shows the obtained results.

Comparative Example 1 A precipitate was formed using aluminum nitrate, nickel nitrate and potassium carbonate as raw materials, washed with water, dried, and tableted.
C. and crushed and sized to 20-42 mesh.
A NiO / Al ₂ O ₃ catalyst containing 70% by weight of iO was prepared. Example 1 was prepared using the catalyst under the conditions shown in Table 1.
The same experiment was performed. Table 1 shows the obtained results. Comparative Example 2 In the same manner as in Example 1, a Ru / Al ₂ O ₃ catalyst was obtained.
An experiment similar to that of Example 1 was performed under the conditions shown in FIG. Profit
The results obtained are shown in Table 1.

[0034]

[Table 1]

Reference Example 1 Granular activated carbon (Shirasagi C2C, manufactured by Takeda Pharmaceutical Co., Ltd.)
After sizing to a mesh (particle size 0.35 to 0.84 mm),
5.21 g were weighed. Next, rhodium chloride was weighed so as to carry 2.5% by weight of rhodium metal as a metal, and dissolved in water to obtain a 100 cc aqueous solution. Activated carbon was immersed in this aqueous solution, evaporated on a hot water bath using a rotary evaporator, and further dried at 120 ° C. in a drier. This was reduced with hydrogen at 400 ° C. for 2 hours and used as a catalyst.

As the reactor, a fixed bed flow type reactor comprising a raw material gas and methanol supply equipment, a methanol evaporator, a raw material preheater, a reactor (inner diameter: 10 mm), a cooler and an acetic acid collector was used. 99.95% in advance
Was mixed with high-purity CO gas purified to a purity of 0.5% to prepare a raw material gas having a hydrogen concentration of 0.5% by volume, 1% by volume and 2% by volume, respectively.

Methanol and methyl iodide are supplied to an evaporator at a constant flow rate to be vaporized. Further, raw material gases are mixed at a constant flow rate, and the mixed raw material is heated to 160 ° C. by a raw material preheater. Was introduced into the reactor. The product discharged from the reactor was cooled and acetic acid was recovered by gas-liquid separation. The reaction conditions are as follows. Reaction temperature 200 ° C. Reaction pressure 9 kg / cm ² GW / F (a value obtained by dividing the weight of the catalyst by the amount of the raw material liquid) = 15 g ·
h / mol CO (including hydrogen): methanol: methyl iodide = 10
0: 20: 1 (molar ratio)

The results obtained are shown in Table 2 and FIG.

Comparative Example 3 The same experiment as in Reference Example 1 was performed under the conditions shown in Table 2. The results obtained are shown in Table 2 and FIG.

[0040]

[Table 2]

Reference Example 2 The same experiment as in Reference Example 1 was performed under the conditions shown in Table 3.
Table 3 shows the obtained results.

[0042]

[Table 3]

Comparative Example 4 An experiment similar to that of Reference Example 1 was carried out except that nickel acetate was used in place of rhodium chloride to prepare a nickel catalyst supporting 2.5% by weight of nickel as a metal, and this catalyst was used. Was performed. As a result, as compared with the activated carbon carrier rhodium metal catalyst, the acetic acid yield was as low as 9.6% by volume when the hydrogen content in the raw material CO was 0% by volume (methane by-product rate was 0.63%).
%). In the case of 9.4% by volume of hydrogen, the acetic acid yield is 3%.
Although improved to 8.8%, it was lower than the result of the activated carbon supported rhodium metal catalyst, and methane production increased to 3.33%.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the hydrogen content in CO gas and the yield of acetic acid in Reference Example 1 and Comparative Example 3 .

2 is a flowchart showing an example of the acetic acid production process.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ identification code FI C10K 1/34 C10K 1/34 (58) Investigated field (Int.Cl. ⁶ , DB name) C10K 3/02 C10K 1/34 C01B 31/18

Claims (3)

(57) [Claims] 1. A method comprising platinum, palladium and rhodium.
A hydrogen-containing CO gas was introduced into a reactor filled with a catalyst comprising a platinum group metal supported on a heat-resistant carrier selected from the group consisting of: A method for purifying hydrogen-containing CO gas, comprising removing hydrogen contained in the gas. 2. The method for purifying a hydrogen-containing CO gas according to claim 1, wherein said platinum group metal is platinum. 3. The method for purifying a hydrogen-containing CO gas according to claim 1, wherein said heat-resistant carrier is gamma-alumina.