JPH055818B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing formaldehyde by dehydrogenating methanol in a gas phase flow reaction. More specifically, the present invention relates to a method for producing formaldehyde characterized by using a catalyst consisting of zinc and synthetic mica. Common industrial methods for producing formaldehyde include the catalytic oxidation dehydrogenation method using a silver catalyst and the catalytic oxidation method using a mixture of iron oxide and molybdenum oxide as a catalyst. In these methods, formaldehyde is usually produced as an aqueous solution. It has been obtained. The former uses a large amount of expensive silver as a catalyst, and the reaction takes place at a high temperature of 650° to 720°C, and is extremely sensitive to trace amounts of metals such as halogen and sulfur in the raw methanol. Therefore, the raw material methanol must be sufficiently purified, and a large amount of water vapor must be mixed in to extend the life of the catalyst.
In the latter case, although the reaction temperature is relatively low at 350° to 450°C, a large excess of air and methanol vapor must be passed over the catalyst, requiring a large investment in equipment and energy costs, and water is produced as a by-product. However, the waste gas after purification cannot be used as fuel and requires special treatment. In both cases, the gas after the reaction is absorbed into water and formaldehyde is recovered as a formaldehyde aqueous solution with a concentration of 30% to 50%, so formaldehyde is used in large industrial applications such as polyacetal resin, urea resin, phenol formaldehyde resin, etc. The reality is that when used for production, processes such as concentration and purification are required, resulting in a large amount of energy loss. On the other hand, several methods have been proposed for the production of formaldehyde by so-called dehydrogenation of methanol. For example, a method using a catalyst consisting of copper, silver, and silicon (Japanese Patent Publication No. 41-11853),
A method using molten zinc, gallium, indium, aluminum, or an alloy thereof (Japanese Patent Publication No. 47-19251), a method of bringing methanol into contact with molten zinc containing carbon or an alloy containing zinc (Japanese Patent Publication No. 48-97808) ) have been proposed.
However, these methods have various drawbacks such as short catalyst life and low reaction rate, and are not satisfactory as industrial production methods. Furthermore, dehydrogenation of methanol is carried out while supplying gaseous sulfur compounds by using a method using a contact consisting of copper, zinc, and sulfur (Japanese Patent Application Laid-Open No. 1407-1987) and by using copper, zinc, or copper, zinc, and sulfur catalysts. The method (Japanese Unexamined Patent Publication No. 51-76209) causes various industrial problems because sulfur is mixed into the reaction product or the discharged gas. In order to improve this, a method using a catalyst consisting of copper, zinc, and selenium (Japanese Patent Application Laid-Open No. 1983-1999-
215) has also been proposed, but it is still unsatisfactory industrially in terms of catalyst life and selectivity. As a result of extensive research in order to improve these problems, the present inventor has found that by using a catalyst obtained from zinc and synthetic mica, formaldehyde can be produced in high yield and extremely stably by dehydrating hydrogen from methanol. The present inventors have discovered that the following can be obtained, and have completed the present invention. The main component of the synthetic mica used in the present invention is an oxide of a cation (Z) with a coordination number of 4 (for example, SiO ₄ regular tetrahedron), and mica crystals are based on such regular tetrahedrons. Tetrahedrons are connected in a hexagonal mesh plate. When octahedral coordination is taken between these upper and lower layers, cations (X, Y) with a coordination number of 6 (for example,
Al ³⁺ , Fe ²⁺ , Mg ^{3+ ,} etc.) are ionicly bonded. One set of these sanderch layers is called a tablet, and these layers are stacked one on top of the other. Between the tablets, cations with a coordination number of 12 called interlayer ions (W), such as alkali metal or alkaline earth metal ions, exist surrounded by oxygen and form very weak bonds. That is, the synthetic mica used in the present invention has the general formula W _1/3~1 (X, Y) _2.5~3 (Z ₄ O ₁₀ ) F ₂ (W: coordination number 12
cation, X, Y: cation with coordination number 6, Z:
It is a cation with a coordination number of 4, O: oxygen, F: fluorine). In the above general formula, W is, for example, Na ⁺ ,
K ⁺ , Ca ²⁺ , Ba ²⁺ , Rb ⁺ , Sr ²⁺ , Li ⁺ etc. X and Y include, for example, Mg ²⁺ , Fe ²⁺ , Ni ²⁺ ,
Mn ²⁺ , Al ³⁺ , Fe ³⁺ , Li ⁺ etc., Z includes (Al ³⁺ , Si ⁴⁺ ), Si ⁴⁺ , Ge ⁴⁺ , Fe ³⁺ , Al ³⁺ ,
Examples include B ³⁺ . Specifically, these synthetic micas include fluorine phlogopite [KMg ₃ (AlSi ₃ O ₁₀ ) F ₂ ], potassium tetrasilicon mica [KMg _2.5 (Si ₄ O ₁₀ ) F ₂ ] Na tetrasilisic mica
[NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ ] Na teniolite [NaMg ₂ Li (Si ₄ O ₁₀ ) F ₂ ] Li theiolite [LiMg ₂ Li (Si ₄ O ₁₀ ) F ₂ ] Na hectorite
[Na _1/3 Mg _{2 2/3} Li _1/3 (Si ₄ O ₁₀ ) F ₂ ] Li hectorite [Ni _1/3 Mg _{2 2/3} Li _1/3 (Si ₄ O ₁₀ ) F ₂ ] etc. There is. Among these synthetic micas, Na tetrasilismic mica, Na taeniolite, and Li taeniolite are particularly suitable in the present invention. The catalysts used in the present invention are these synthetic micas (general formula W _1/3~1 (X, Y) _2.5~3 (Z ₄ O ₁₀ ) F ₂ )
The interlayer ions W are ion-exchanged with zinc ions. Any known ion exchange method can be employed as a method for preparing the catalyst used in the present invention. Among these, it is preferable to prepare and add an aqueous solution of a divalent zinc salt such as zinc chloride, zinc nitrate, zinc acetate, zinc oxalate, zinc formate, or zinc sulfate to a suspension of purified Na tetrasilisilisilisilisicum squid. , preferably further NH ₃ per mol of zinc
Add 1mol to 20mol. The amount of zinc ions added at this time is about 0.05 to 5 mol, preferably 0.2 to 2 mol, per 1 mol of Na ions to be ion-exchanged. Thereafter, ion exchange treatment is carried out by stirring while heating to an appropriate temperature, followed by filtering the solid phase, washing thoroughly with water, repeating the filtering process, and finally drying at an appropriate temperature. Although the obtained powder may be used as it is as a catalyst in the present invention, it is preferable to perform a calcination treatment in air or nitrogen stream at a temperature of 400°C to 800°C. The reaction of the present invention is usually preferably carried out in a fixed bed gas phase flow system. Regarding reaction conditions, the catalyst layer temperature is usually 450 to 650°C, preferably 500 to 600°C. Further, methanol is usually supplied to the catalyst layer in vapor form together with an inert gas or hydrogen using a vaporizer or the like. The amount of methanol supplied depends on the size of the reactor,
Although it depends on the shape etc., it is appropriate to use 1 to 100 mol/hour per catalyst. If it is less than 1 mol/hour, it is not practical, and if it exceeds 100 mol/hour, the methanol reaction rate decreases. The product obtained by the present invention consists of 5 wt% or more of formaldehyde, 0 to 1 wt% of water, and the remainder methanol, and the water content in the product is extremely low, making it possible to obtain formaldehyde in high yield. Furthermore, since hydrogen can be obtained in high yield through the reaction, the off-gas from the reaction can also be effectively used as a heat source or other raw materials. The catalyst of the present invention has a high methanol reaction rate and can obtain formaldehyde in an extremely high yield. The catalyst remained active for more than 10 hours, and almost no carbonaceous material was deposited on the catalyst. Another major feature is that the blocking phenomenon caused by fusion between catalyst pellets, which tends to occur with copper-based catalysts, does not occur at all. EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. Examples 1 to 5, Comparative Example 1 (1) Catalyst Preparation Method Catalyst A 15.07 g of zinc nitrate (Zn(NO ₃ ) _{2.6H 2} O) was added to 200 g of
ml of pure water and add 26ml of 28% ammonia water to this.
Add to obtain Solution A. On the other hand, sodium tetrasilisilisilismic acid (NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ )
Add 1.8 g of pure water to 200 g of a 10 wt% aqueous sol solution, mix, and heat and mix in a 40°C water bath to obtain Solution B. Add solution A to solution B and continue heating and stirring at 40°C for 90 minutes. Thereafter, the operation of filtering the mixture and washing with pure water was repeated three times, and the obtained solid was dried in an oven at 150°C for 20 hours, and then calcined at 600°C for 5 hours in an air stream. Catalyst A thus obtained had a BET surface area of 13.2 m ² /g and a Zn content of 14.0 wt%. Catalyst B Zinc nitrate (Zn(NO ₃ ) ₂・6H ₂ O) 7.53g at 200
ml of pure water and add 13ml of 28% ammonia water to this.
Add to obtain Solution C. Add solution C to solution B, which has the same recipe as that used when preparing catalyst A, and heat at 40°C.
Continue heating and stirring for 90 minutes. After that, the process of filtering this mixture and washing with pure water was repeated three times, and the resulting solid was placed in an oven at 150℃ for 20 minutes.
After drying for an hour, it was fired at 600°C for 5 hours in an air stream. The catalyst B obtained in this way
BET surface area is 8.8m ² /g, Zn content is 7.8wt%
It was hot. Catalyst C Zinc nitrate (Zn(NO ₃ ) ₂・6H ₂ O) 22.60g
28% ammonia water dissolved in 39 ml of pure water
ml to obtain Solution D. Add solution D to solution B, which has the same formulation as that used when preparing catalyst A, and add 40
Continue heating and stirring at °C for 90 minutes. After that, the process of filtering this mixture and washing with pure water was repeated three times, and the resulting solid was placed in an oven at 150℃.
After drying for 20 hours, it was fired at 600°C for 5 hours in a stream of air. The catalyst B obtained in this way
BET surface area is 17.2m ² /g, Zn content is 18.9wt
It was %. Catalyst D Zinc nitrate (Zn(NO ₃ ) ₂・6H ₂ O) 15.07g at 200
Dissolve in ml of pure water to obtain Solution E. Add Solution E to Solution B, which has the same recipe as that used when preparing Catalyst A, and continue heating and stirring at 40°C for 90 minutes. After that, the mixture is filtered and further washed with pure water for 3 steps.
The resulting solid was dried in an oven at 150°C for 20 hours and then heated to 600°C in a stream of air.
Perform time baking. Catalyst D thus obtained
BET surface area is 10.5m ² /g, Zn content is 2.5wt
It was %. Catalyst E 3.5 g of zinc chloride (ZnCl ₂ ) was dissolved in 200 ml of pure water, and 13 ml of 28% aqueous ammonia was added to obtain solution F. Add solution F to solution B, which has the same recipe as that used when preparing catalyst A, and heat and stir at 40℃.
Continue for 90 minutes. Thereafter, the operation of filtering the mixture and washing with pure water was repeated three times, and the resulting solid content was dried in an oven at 150°C for 20 hours, and then calcined in an air stream at 600°C for 5 hours. The BET surface area of catalyst E thus obtained was 9.1 m ² /
g, Zn content was 7.1 wt%. Catalyst F 8.61 g of silver nitrate (AgNO ₃ ) was dissolved in 200 ml of pure water, and 13 ml of 28% aqueous ammonia was added thereto to obtain Solution G. Add solution G to solution B, which has the same formulation as that used when preparing catalyst A, and heat and stir at 40℃ for 90 minutes.
Continue for minutes. After that, the operation of filtering this mixture and washing with pure water was repeated three times, and the resulting solid was dried in an oven at 150°C for 20 hours.
Fired at 600°C for 5 hours in an air stream. The BET surface area of catalyst F thus obtained is 13.1
m ² /g. Catalyst G 6.81 g of cupric chloride (CuCl ₂ ) was dissolved in 200 ml of pure water, and 26 ml of 28% aqueous ammonia was added thereto to obtain Solution H. Add Solution H to Solution B, which has the same recipe as that used when preparing Catalyst A, and continue heating and stirring at 40°C for 90 minutes. Thereafter, the operation of filtering the mixture and washing with pure water was repeated three times, and the resulting solid was dried in an oven at 150°C for 20 hours, and then calcined at 600°C for 5 hours in an air stream. The BET surface area of the catalyst G thus obtained is
It was 13.4m ² /g. Catalyst H Dissolve 5.10 g of cuprous chloride (CuCl) in 200 ml of pure water, add 26 ml of 28% ammonia water, and prepare I
Get the liquid. Add Solution I to Solution B, which has the same recipe as that used when preparing Catalyst A, and continue heating and stirring at 40°C for 90 minutes. Thereafter, the mixture was filtered and washed with pure water three times, and the resulting solid was dried in an oven at 150°C for 20 hours, and then calcined at 600°C for 5 hours in an air stream.
The BET surface area of catalyst H thus obtained is 18.0
m ² /g. The methods for preparing catalysts A to H have been described above, and the prepared catalysts were molded to a particle size of 24 to 48 mesh and then stored in a desiccator. The specific surface area was measured using Monosorb (manufactured by Quantachrome) after dehydration treatment at 200°C for 30 minutes in a nitrogen stream. On the other hand, the amount of Zn component (wt%) in the catalyst was measured by atomic absorption spectrometry. (2) Catalytic reaction test Fill a quartz tubular reactor with an inner diameter of 10 m/m with 2.0 g of catalyst. Then, 550% of a mixed gas of methanol and nitrogen (CH ₃ OH/N ₂ = 18/82 molar ratio), which had been vaporized and mixed in advance at 150°C, was added to this reactor.
The methanol dehydrogenation reaction was carried out at a furnace temperature of 550°C by flowing the mixture under normal pressure conditions of mmol/hr. The outlet gas of the reactor was collected using APS-201 20% Flusin by a gas sampler that was kept warm.
The reaction products, formaldehyde [HCHO], methyl formate, dimethyl ether [DME], hydrogen [ H ₂ ],
Carbon monoxide [CO], methane [CH ₄ ], unreacted methanol [outlet CH ₃ OH], and nitrogen were analyzed and quantitatively determined. The reaction results are shown in Table 1, and all values are after the reaction was maintained for 8 to 12 hours after reaching the set temperature, indicating steady activity. Analysis by gas chromatography revealed that almost no methyl dimethyl ether formate was produced. Therefore, the conversion rate, yield, and selectivity were calculated using the following formula. CH ₃ OH conversion rate (%) = (1 - [Outlet CH ₃ OH] / [HC
HO] + [CO] + [CH ₄ ] + [outlet CH ₃ OH]) × 100 HCHO yield (%) = [HCHO] / [HCHO] + [CO] +
[CH ₄ ] + [Outlet CH ₃ OH] × 100 HCHO selectivity (%) = [HCHO] / [HCHO] + [CO]
+ [CH ₄ ] × 100 (However, [HCHO], [CO], [CH ₄ ] are the production rates (mmol/hr) of each component, [CH ₃ OH]
is unreacted methanol (mmol/
hr). ) 【table】

Claims (1)

[Claims] 1 In a method for producing formaldehyde in a gas phase by dehydrogenating methanol in the absence of oxygen, the general formula W _1/3~1 (X, Y) _2.5~3 (Z ₄ O ₁₀ )
F ₂ (W is a cation with a coordination number of 12, X and Y are a cation with a coordination number of 6
cation, Z represents a cation with a coordination number of 4, respectively).
A method for producing formaldehyde, characterized by using a catalyst obtained by ion-exchanging zinc ions with zinc ions.