JPS6241584B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing methacrolein in high yield by using a specific catalyst when producing methacrolein by oxidizing isobutylene or tertiary-butanol with molecular oxygen. Many catalysts have been proposed so far as catalysts for gas phase catalytic oxidation reactions of isobutylene or tert-butanol. However, from an industrial standpoint, there are still many points to be improved. For example, when producing methacrolein, the yield of the product methacrolein from the raw material (isobutylene or tert-butanol) is still low, and even with what has been said to be an excellent catalyst,
The selectivity to isobutylene is about 82 to 86% at most, and a catalyst system with even higher selectivity is desired. Catalysts containing molybdenum as a main component and also tellurium may show quite high yields in the early stage of the reaction, but their activity decreases significantly due to structural changes and scattering of tellurium, resulting in long-term high yields. There are very few catalysts that can obtain methacrolein. In addition, especially when methacrolein is used as a raw material for a reaction that directly produces unsaturated esters using oxygen and alcohol, it is desirable for by-products such as methacrylic acid and acetic acid to be as low as possible in industrial applications. There are many problems when using it as a catalyst. As a result of our earnest efforts and detailed study to resolve the above issues, we have found that:
The present invention has been accomplished. That is, in the present invention, when producing methacrolein by oxidizing isobutylene or tertiary-butanol with molecular oxygen, the general composition Mo ₁₂ Fe _a Ni _b Te _c X _d Ti _f Y _g O _h (however, a, b, c, d, f, g represent the number of moles per 12 mol of molybdenum, X is Rb,
From Cs and Tl, Y represents at least one element selected from Cu, Pb, Nd, and Sm, a has a value from 0.2 to 6, and b has a value from 0.2 to 6. , a+b is a value from 1 to 10, c is a value from 0.1 to 4, and d is 0.1
f is a value from 0.1 to 4, g is a value from 0 to 5, and h is the number of oxygen atoms satisfying other valences present. ) The present invention relates to a method for producing methacrolein, characterized by using a catalyst having the following. A feature of the present invention is that when the catalyst is used, the selectivity for methacrolein is 90% or more, and methacrolein can be obtained with a higher selectivity than isobutylene or tert-butanol. Therefore, the amount of by-products such as methacrylic acid, acetic acid, acetone, carbon monoxide, and carbon dioxide is small. In addition, the catalyst exhibits extremely little decrease in activity and has the ability to maintain high activity and high selectivity for a long period of time. Molybdenum is an essential component in the catalyst of the present invention. In a system in which molybdenum is excluded from the catalyst composition, the activity is extremely low and no improvement in methacrolein can be expected. Also, tellurium is used as a promoter. Catalysts using tellurium as a promoter have been used in the past to increase catalytic activity and selectivity, but although their initial activity and selectivity are excellent, their activity quickly declines, making it difficult to put them into practical use. It has been. The present invention prevents a decrease in catalyst activity, which is one of the drawbacks of catalysts using tellurium as a promoter, and furthermore uses titanium in the catalyst system of the present invention in order to impart high activity. Contains both iron and nickel. Although a decrease in catalyst activity is fatal for industrial catalysts, it can be prevented by using appropriate amounts of titanium, iron, and nickel. The above-mentioned effects of titanium, iron, and nickel will be lost if any one of them is missing, and if the total amount of iron and nickel becomes larger than that of molybdenum, it will affect the function of the main catalyst of molybdenum, so it is preferable. do not have. Furthermore, in addition to the above-mentioned effects, the addition of titanium has the effect of particularly reducing by-products of water-soluble acids (acetic acid, methacrylic acid). Therefore, operations such as quench towers have been used to remove water-soluble acids from the reaction product gas, but when this catalyst is used, fewer acids are produced, so the amount of wastewater that needs to be treated is reduced. Therefore, it is possible to downsize the wastewater treatment facility. In addition, when this catalyst is used in a methacrolein production process for supplying raw materials for a reaction that directly produces unsaturated esters (for example, methyl methacrylate) from methacrolein, the yield of methacrolein is reduced because the amount of by-product methacrylic acid is extremely small. The cost of processing methacrylic acid is also very low. The X component in the catalyst of the present invention is a component that exhibits an effect even in a small amount, and is at least one element selected from rubidium, cesium, and thallium.
It is an essential component in the catalyst of the present invention. The selectivity of methacrolein cannot be improved in systems that do not contain the X component and systems that contain other alkalis (sodium, lithium). As the carrier for the catalyst of the present invention, known carriers such as silica, silicon carbide, and alumina can be used, but silica sol and silica gel are particularly excellent. The catalyst of the present invention can be prepared, for example, as follows. Add water-soluble iron, nickel, X-component compounds, titanium compounds, and water-soluble Y-component compounds to an aqueous solution of ammonium molybdate, then add tellurium oxide or acid, and then add silica sol as a carrier. The mixture is evaporated to dryness on a hot water bath, and pre-calcined in the presence of air or oxygen, followed by main firing. The pre-calcination temperature is usually 100-500°C, preferably 200-400°C. Main firing is usually 400-1000℃, preferably 500℃
The temperature range is 700°C to 700°C, more preferably 500 to 650°C. As the raw materials for each element used in the preparation of the present invention, not only oxides but also any material that forms the catalyst of the present invention by calcination can be used. Examples include inorganic acid salts such as ammonium salts, nitrates, and carbonates of each element, and organic acid salts such as acetates. The catalyst can be used in the form of powder, granules, or tablets. The reactor may be either a fixed bed or a fluidized bed. The reaction according to the invention is carried out at a temperature range of 250°C to 550°C, preferably 350°C to 450°C, and a pressure of 0.5 to 10°C.
The reaction is carried out at atmospheric pressure, preferably normal pressure to 2 atmospheres. The contact time of the mixed raw material gas of isobutylene or tert-butanol, air (or oxygen), water vapor and inert gas with the catalyst is at normal pressure.
It is 0.1 to 15 seconds, preferably 0.2 to 10 seconds.
The flow rate of the raw material gas to the catalyst is the cylinder velocity (SV)
Generally 100 to 5000Hr ^-1 , preferably 200
~2000Hr ^-1 . The composition of the gas mixture is 0.5 to 4 moles of oxygen per mole of isobutylene or tert-butanol;
The amount is preferably 1.4 to 2.5 moles, and although steam is not essential, it is advantageous in terms of yield to add 1 to 30 moles, preferably 2 to 15 moles, per mole of isobutylene or tert-butanol. The addition of other inert gases (for example, _N2 , He, Ar, CO2 _, etc.) can be freely changed according to changes in other compositions. When using the catalyst of the present invention described in detail above,
The selectivity of methacrolein reaches as high as 90-94%.
A catalyst that has such high selectivity and maintains its activity stably for a long period of time is extremely innovative. Examples are shown below, but the present invention is not limited thereto. Example 1 21.2g of ammonium paramolybdate in 200ml
Dissolve in distilled water, add 0.80 g of thallium nitrate, and dissolve. This is called liquid A. Furthermore, nickel nitrate
Dissolve 2.9g in 200ml of distilled water to obtain ferric nitrate 4.04
g, lead nitrate 6.6 g, titanium trichloride 1.54 g, and telluric acid 4.55 g. This is mixed with the liquid A shown above, and 52.43 g of silica sol (Snowtex) is added. This solution was then evaporated to dryness on a water bath and then
Calcining was performed in air at 250°C for 2 hours, and the fired product was pulverized to 10 to 28 mesh and air fired at 650°C for 4 hours. The catalyst composition was Mo ₁₂ Pb ₂ Fe ₁ Ni _{1 Tl 0.3 Ti 1} Te ₂ O _x . Example 2 5 g of the catalyst prepared in Example 1 was charged into a Pyrex reaction tube with an inner diameter of 5 mm and reacted at a reaction temperature of 400°C. Raw material gas composition is isobutylene/O ₂ /
The H ₂ O/He molar ratio was 3/6/20/71 and the contact time was 2.5 seconds. The analysis was performed using Shimaz 6APrTF gas chromatography, and Chromosolve 101 was used as the column. The results are shown in Table 1. Examples 3 to 4 A reaction was carried out under the same reaction conditions as in Example 2 using a catalyst having the composition shown in Table 1 under the same preparation conditions as in Example 1. The results are shown in Table 1. Comparative Examples 1-2 A reaction was carried out under the same reaction conditions as in Example 2 using the same preparation conditions as in Example 1 and using a catalyst having the composition shown in Table 2. The results are shown in Table 2.

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[Table] Examples 5 to 23 A reaction was carried out under the same reaction conditions as in Example 2 using a catalyst having the composition shown in Table 3 under the same preparation conditions as in Example 1. The results are shown in Table 3. Comparative Examples 3 to 10 A reaction was carried out under the same reaction conditions as in Example 2 using a catalyst having the composition shown in Table 4 under the same preparation conditions as in Example 1. The results are shown in Table 4.

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[Table] Examples 24-26, Comparative Examples 11-12 Using the catalysts used in Examples 2-4 and Comparative Examples 1-2, continuous reactions were carried out for 100 hours under the same reaction conditions as in each example. . The results are shown in Table 5.

[Table] Examples 27 to 29 Under the same preparation conditions as in Example 1, 5 g of the catalyst having the composition shown in Table 6 was filled into a Pyrex reaction tube with an inner diameter of 5 mm, and the reaction was carried out at a reaction temperature of 380 to 440°C. Raw material gas composition is tertiary butanol/
The molar ratio of O ₂ /H ₂ O/He was 3/6/20/71 and the contact time was 2.5 seconds. The results are shown in Table 6. Comparative Examples 13 and 14 Under the same preparation conditions as in Example 1, a reaction was carried out under the same reaction conditions as in Examples 27 to 29 using a catalyst having the composition shown in Table 7. The results are shown in Table 7. Examples 30 to 48 Reactions were carried out under the same conditions as in Examples 27 to 29 using catalysts having the compositions shown in Table 8 under the same preparation conditions as in Example 1. The results are shown in Table 8.

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【table】

[Table] Comparative Examples 15-22 Reactions were carried out under the same reaction conditions as Examples 27-29 using catalysts having the compositions shown in Table 9 under the same preparation conditions as in Example 1. The results are shown in Table 9.

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[Table] Examples 49 to 51, Comparative Examples 23 to 24 Using the catalysts used in Examples 2 to 4, a continuous reaction was carried out for 100 hours under the same conditions as in each Example. The results are shown in Table 10.

【table】

Claims (1)

[Claims] 1. When producing methacrolein by oxidizing isobutylene or tert-butanol with molecular oxygen, the general composition Mo ₁₂ Fe _a Ni _b Te _c X _d Ti _f Y _g O _h (however, a, b, c, d, e, f, g represent the number of moles relative to 12 mol of molybdenum, and X is
Among Rb, Cs, and Tl, Y represents at least one element selected from among Cu, Pb, Nd, and Sm, a is a value from 0.2 to 6, and b is
The value is from 0.2 to 6, a+b is the value from 1 to 10, c is the value from 0.1 to 4,
d is a value from 0.1 to 3, f is a value from 0.1 to 4, g is a value from 0 to 5, and h
is the number of oxygen atoms that satisfy the other valences present. ) A method for producing methacrolein, characterized by using a catalyst having the following.