JPS59193136A - Process for maintaining activity of oxidation catalyst containing molybdenum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to the oxidation of olefins in a fixed bed reactor.

The present invention relates to a method for stably maintaining the activity of a molybdenum-containing oxidation catalyst used in catalytic reactions of olefins such as ammoxidation and oxidative dehydrogenation over a long period of time.

Olefins such as propylene and imbutylene are oxidized in the gas phase at high temperatures in the presence of a molybdenum-containing oxidation catalyst to produce unsaturated aldehydes such as acrolein and methacrolein, and ammoxidation to produce unsaturated aldehydes such as acrylonitrile and methacrylonitrile. Many methods have already been proposed for producing conjugated diolefins such as butadiene and isoprene by oxidative dehydrogenation of saturated nitrile, butene, inbutylene, and the like. For example, there is a method for producing unsaturated aldehydes such as acrolein and methacrolein by oxidizing olefins such as propylene and isobutylene at high temperature in the gas phase in the presence of a molybdenum-containing oxidation catalyst.

For example, Japanese Patent Publication No. 36-3563 1% Publication No. 42-2
No. 2477, Japanese Patent Publication No. 43-20285, Japanese Patent Publication No. 44-62'46, Japanese Patent Publication No. 47-32052 Publications 1. Special Public Law No. 48-1645, Special Public Law No. 50-1
24.1 Publication + 49 Publication No. 57-50765,
Japanese Patent Publication No. 5B-4692 2 Japanese Patent Publication No. 58-4693, Japanese Patent Publication No. 58-4694, U.S. Patent No. 419
No. 0608, US L1 Grant No. 41'762'34
It is written on the name of the ship, etc. Further, a method for producing unsaturated nitriles such as acrylonitrile and methacrylonitrile by ammoxidizing olefins such as propylene and imbutylene is disclosed in, for example, Japanese Patent Publication No. 39-3670.

Special Publication No. 45-35287, Special Publication No. 48-4309
Publication No. 6, Japanese Patent Publication No. 57-5221.

Special Publication 'Sho 5'i'-4631 Publication 1% Publication Sho 5.7-5
220, JP 57-32618, JP 5'? -119837, U.S. Patent No. 4192'?
6, U.S. Pat. No. 4,190,556, U.S. Pat. No. 4,167,494, etc. Also, olefins such as butene and inamylene are oxidized and dehydrogenated to produce conjugated diolefins such as butadiene and inglene. The method of manufacturing is 1, for example, Japanese Patent Publication No. 46-33930.
Publication No. 49-3496, Special Publication No. 49-49
Publication No. 441, Japanese Patent Publication No. 53-44157, U.S. Patent No. 4174354, U.S. Patent No. 364293
No. 0, Mei #l, US Patent No. 3,414,631, Specification 1, and the like.

Molybdenum-containing oxidation catalysts are used for the oxidation of olefins.

It generally has excellent catalytic activity in catalytic reactions of olefins such as ammoxidation and oxidative dehydrogenation.

When a catalytic reaction of olefins is carried out in a fixed bed reactor, the catalyst becomes deactivated with the passage of reaction time, resulting in poor reaction results such as the reaction rate of the olefin, the selectivity of the target product, and the yield.

It is said that one of the reasons why molybdenum-containing oxidation catalysts become deactivated during use is that a portion of the molybdenum in the catalyst sublimes and escapes due to heat.

Recently, catalytic reactions of olefins have been carried out at as low a temperature as possible and with a uniform temperature distribution in the catalyst layer, but it is not easy to maintain the catalytic activity stably for a long period of time.

Modern fixed bed reactors, which are generally used industrially for the catalytic reaction of olefins, have a tube diameter of 20 to 501 njn and a length of 1. A multi-tube type reactor with a plurality of ~5m reaction tubes bundled together is used. However, in the reactor, the temperature difference between the heat medium and the catalyst layer may be 40 to 60°C, and the temperature of the catalyst layer is often as high as the cylinder temperature, for example, 400°C or higher. In addition, since the raw material gas introduction section has a high olefin concentration and a large amount of reaction heat, the temperature difference with the heating medium is especially large, and molybdenum in the catalyst is lost due to sublimation and escape, and the catalyst is deactivated quickly.

The present inventors have developed a method that can prevent the deactivation of molybdenum-containing oxidation catalysts and maintain the catalytic activity stably for a long period of time even when catalytic reactions of olefins are carried out in a fixed bed reactor. As a result of intensive research with the aim of doing this, we found that when carrying out catalytic reactions, we use molybdenum-containing oxidation catalysts.

The inventors discovered that the above object can be achieved by using a heat-resistant inorganic substance substantially inert to the catalytic reaction in combination with a support in which molybdenum oxide is supported, leading to the present invention.

The present invention is for carrying out a catalytic reaction of olefins in a fixed bed reactor filled with a molybdenum-containing oxidation catalyst.

A method for sustaining the activity of a 4-lybdenum-containing oxidation catalyst, which comprises carrying out a catalytic reaction together with a molybdenum-containing oxidation catalyst by filling a support in which molybdenum oxide is supported on a heat-resistant inorganic substance that is substantially inert to the catalytic reaction. It is.

In the present invention, it is not clear why the activity of the molybdenum-containing oxidation catalyst is sustained even more than before when a support in which molybdenum oxide is supported on a heat-resistant inorganic substance that is substantially inert to the catalytic reaction is used, but the oxidation Sublimation and escaping of molybdenum from the catalyst layer can be suppressed by using a support in which molybdenum is supported. It is speculated that this is to prevent

The amount of molybdenum oxide supported in the support, in which molybdenum oxide is supported on a heat-resistant inorganic substance that is substantially inert to the catalytic reaction, is not particularly limited, but a range of 10 to 90% by weight is generally appropriate. The size and shape of the support are also not particularly limited, but it is desirable that the size and shape be similar to that of the catalyst used.
Generally, a spherical or cylindrical shape with a diameter of 3 to 10 mm is used. Any heat-resistant inorganic material may be used as long as it is substantially inert to the catalytic reaction, but materials commonly used as carriers include silica, alumina, silica-alumina, carborundum, zirconia, Silicon carbide, titania, etc. are suitable.

For the preparation of a phase support in which molybdenum oxide is supported on a superthermal property that is substantially inert to catalytic reactions, 1, for example, a method of impregnating a molded heat-resistant inorganic material with a solution of a molybdenum compound dissolved therein; A method in which a solution of a molybdenum compound dissolved in a heat-resistant inorganic substance is sprayed, and a method in which a molybdenum compound powder and a heat-resistant inorganic substance powder are mixed and molded.

A method in which a molded heat-resistant inorganic material is moistened and mixed with molybdenum compound powder to adhere.

Any method known per se, such as a method of forming a co-precipitate from a solution containing a heat-resistant inorganic substance and a solution containing a molybdenum compound, can be appropriately adopted, and if necessary, the final product can be prepared by drying and baking. into a support containing molybdenum oxide. As the molybdenum compound for supporting molybdenum oxide, molybdate salts such as ammonium molybdate, molybdenum oxide, and the like are appropriately used.

In the present invention, the molybdenum oxide supported on a heat-resistant inorganic substance that is substantially inert to the catalytic reaction is not limited to MoC2 or M2O3,
It may be a mixture of these or a state in which molybdenum is combined with oxygen and a heat-resistant inorganic substance.

In the present invention, when filling a fixed bed reactor with a support in which molybdenum oxide is supported on a heat-resistant inorganic substance that is substantially inert to the catalytic reaction together with a molybdenum-containing oxidation catalyst, a mixture of the two may be used. Although the catalyst and the supported material may be packed so that their respective layers are formed without mixing them, the catalyst and the supported material may be packed so that the catalyst concentration gradually increases from the raw material gas inlet to the product gas outlet. is preferable. There is no particular restriction on the mixing ratio of the catalyst and the supported material, but in general, it is appropriate to mix the supported material so that the amount of the supported material is 1% to 90 voJ%, and the amount of the packed bed is 1%. When packing without making any difference in catalyst concentration, the supported material is 50 vof%.
It is desirable to mix and fill as follows.

Further, in the present invention, the amount of the supported material supported by molybdenum oxide depends on the method of filling the catalyst and the supported material.

It varies depending on the type of catalytic reaction, the type of catalyst, the amount of molybdenum oxide in the support, etc., but in general, the amount of molybdenum oxide in the support filled in the reactor is equivalent to 1 gram of molybdenum in the catalyst filled in metal terms. 0.005 per atom
~0.6 gram atom, preferably 0.01-0.5 gram atom. If the amount of molybdenum oxide is too small, the effect of sustaining the catalyst activity will be insufficient, and if it is too large, a large amount of molybdenum oxide will adhere to the catalyst and reduce the activity. It is appropriate to make it a range.

The present invention relates to the oxidation of olefins in a fixed bed reactor.

Along with molybdenum, bismuth, tellurium, antimony, &a, iron, and cobalt are used in catalytic reactions of olefins such as ammoxidation and oxidative dehydrogenation.

Nickel, manganese, chromium, tungsten, vanadium, palladium, tantalum, niobium, phosphorus.

Arsenic, tin, zirconium, titanium, magnesium, calcium, barium, +-lead, strontium, cadmium, @, aluminum, silver, lithium, potassium, cesium, rubidium, thallium.

It can be applied to a molybdenum-containing oxidation catalyst containing one or more of indium, germanium, boron, rare earth elements, etc. as a catalyst component, and the catalyst activity can be maintained stably over a long period of time. For example, normally 1
According to the present invention, even if the catalyst has a lifespan of only about 1.5 years,
It has the great advantage of being able to maintain the initial catalytic activity for about three years with almost no decline.

Typical molybdenum-containing oxidation catalysts include the catalysts described in the above-mentioned patent publications (patent specifications), as well as the commonly known molybdenum, bismuth and antimony; molybdenum, bismuth and lead; molybdenum, bismuth and iron. Cobalt or nickel; molybdenum, antimony.

Examples include catalysts based on Te/L/L, Co, Balt, Di, Kel, etc., and catalysts in which the above-mentioned catalyst components are appropriately added.

When applied to a catalyst containing molybdenum as an essential component, the effect of sustaining the catalytic activity is remarkable.

In carrying out the present invention, when a fixed bed reactor is filled with a support in which molybdenum oxide is supported on a tetrathermal inorganic substance that is substantially inert to the catalytic reaction together with a molybdenum-containing oxidation catalyst, only both of them are charged. However, carriers commonly used in the past may be used.

For example, silica, alumina, alumina-silica, silicon carbide, carborundum, zirconia, f-a, etc. may be used in combination as appropriate with or without mixing. Further, it is also possible to use a molybdenum-containing oxidation catalyst containing a carrier.

The reaction conditions for carrying out the catalytic reaction of olefins vary depending on the type of catalytic reaction, such as oxidation, ammoxidation, oxidative dehydrogenation, etc., but conventionally known reaction conditions are employed for each.

For example, when producing unsaturated aldehydes such as acrolein and methacrolein by oxidizing olefins such as propylene and imbutylene, the amount of oxygen supplied to the olefin is 0.8 to 4 mol per mol of olefin, and the reaction temperature is is 250-500℃.

The contact time is 0.5 to 15 seconds, and when producing unsaturated nitriles such as acrylonitrile and methacrylonitrile by ammoxidizing olefins such as propylene and isobutylene, the ammonia and oxygen supplied to the olefin are Ammonia is 0.0% per mole.
5-3 mol, oxygen 0.8-4 mol, reaction temperature 300
~500℃, the contact time is 0.3 to 20 seconds, and when producing conjugated diolefins such as 3-butadiene and isoprene by oxidative dehydrogenation of olefins such as butene-1゜isobutylene, The amount of oxygen supplied is 0.5 to 4 moles per mole of olefin, the reaction temperature is 250 to 500°C, the contact time is 0°3 to 15 seconds, and all reactions are carried out at normal pressure.

It may be under any pressure including reduced pressure.

Next, the present invention will be explained with reference to Examples and Comparative Examples. Reaction rate (correspondence) 1 selectivity (φ) and yield excellent) on each side
are according to the following definitions.

Number of moles of olefin supplied Number of moles of product Example 1 Diameter: 4 rnnIφ, length: 4
〜8ηLmL cylindrical catalyst consisting of molybdenum, bismuth, antimony, lead, iron and oxygen:' (Mo,
0i3145b1Pb1Fe, oX: The subscript is the atomic ratio of each catalyst component).

15001n of hot water at 80℃, ammonium molybdate ((NH4)6 MO70□4・4H20)
Porous spherical alumina with a diameter of 5 mm [manufactured by Fujisho 11f Kazai Co., Ltd.] 1
After immersing 000g of water and evaporating the water while heating and stirring,
The product was calcined at 500° C. for 2 hours in an air atmosphere to obtain a supported material in which molybdenum oxide was supported on alumina (supported amount of molybdenum oxide was 30% by weight).

Next, 730 m
A mixture of 180 nt of the above catalyst 1'08 +r:ρ, diameter 5ηLmφ and 727 nt of the support supported by molybdenum oxide was filled to a height of 730 rli+n from this packed bed. A mixture of the catalyst 1807 + 144 mA of alumina support with a diameter of 5 tnn + φ and the support 36 + m of the molybdenum oxide supported was filled up to a height of 1460 nm, and the catalyst '720 m1 was filled to a height of 1460 nm from this packed bed. This three-layer packed bed (atomic ratio of molybdenum in the catalyst to molybdenum in the support is 1:0.03) is heated to 410°C, and propylene:ammonia: The molar ratio of water vapor and air is 1.04: 1.19: 3.46:, 11
．． A mixed gas of 59 t/min was flowed at a flow rate of 17.28 t/min, and the ammoxidation of propylene was 50 t/min with a contact time of 5 seconds.
The test was carried out continuously for 00 hours. The propylene reaction rate, acrylonitrile selectivity, and yield at 24 hours and 5000 hours after starting the reaction were as shown in Table 1.

Comparative Example 1 Example 1k was repeated except that a spherical alumina carrier having a diameter of 5υ1φ was used in place of the molybdenum oxide supported support in the packed bed of Example 1. 24th hour and 5000
Reaction rate of propylene at hour.

The selectivity and yield of acrylonitrile were as shown in Table 1.

Example 2 A catalyst with a diameter of 5 mη2φ and a height of 5 Tn was prepared according to the catalyst preparation method described in Example 1 of U.S. Pat. No. 4,278,614.
jnH columnar catalyst consisting of molybdenum, cobalt, nickel, iron, bismuth, tellurium, titanium and oxygen (
MO4oCO5N12Fe2B1o, TeoIT150
x) was prepared.

Further, molybdenum oxide CMoO2)] powder and α-alumina powder were mixed at a weight ratio of 40:60 for 1 hour using a V-type mixer, and then tableted using a tablet machine to a diameter of 5 mm.

It was molded into a columnar shape with a height of 5 nm to obtain a support in which molybdenum oxide was supported on alumina.

Next, the same reaction tube as in Example 1 was filled with 50 fnl of the support material supported by molybdenum oxide, and 60 parts by weight of the above catalyst and 40 parts by weight of a spherical alumina support with a diameter of 5 φ were placed on top of this packed bed. A uniformly mixed mixture 14407 was packed into a packed bed consisting of two layers (the atomic ratio of molybdenum in the catalyst to molybdenum in the support was 1:0.047).
) is heated to 420°C and the molar ratio of propylene:ammonia:steam:air is 1.48:
1. '70: 4.94:16:56 mixed gas 2
4.68 /-/min flow rate, contact time 3.
Ammoxidation of propylene was continuously performed for 7000 hours in 5 seconds. The propylene reaction rate, acrylonitrile selectivity, and yield at 24 hours and 7000 hours after starting the reaction were as shown in Table 2.

Comparative Example 2 Example 2 was repeated except that the molybdenum oxide supported material of Example 2 was not filled.

The propylene reaction rate, acrylonitrile selectivity, and yield at 24 hours and 7,000 hours after starting the reaction were as shown in Table 2.

Example 3 According to the catalyst preparation method described in Example 1 of U.S. Pat. No. 4,267,385, the diameter was 5Tnjnφ and the height was 5+x.
+) (Cylindrical molybdenum, conolite, nickel, iron, bismuth, aluminum, titanium, potassium and oxygen catalyst (Mo.C06N12Fe2B 1
o2AA2 T 15 K o,. 50x) was prepared.

Next, 70 parts by weight of the above catalyst and 30 parts by weight of the supported molybdenum oxide prepared in Example 1 were placed in a carbon steel reaction tube having a diameter of 25 rrunφ and a height of 3500 mmH.
10001n1. This packed bed (atomic ratio of molybdenum in the catalyst to molybdenum in the support is 1:0.24) is heated to 380°C, and the molar ratio of inbutylene:steam:air is 1.3.
: 5.3 : 13.4 mixed gas at 20, Ot/m
Isobutylene was oxidized continuously for 5000 hours with a contact time of 3.0 seconds. The reaction rate of isobutylene, selectivity and yield of methacrolein at 24 hours and 5000 hours after starting the reaction were as shown in Table 3.

Example 3 Example 3 was repeated except that instead of the molybdenum oxide-supported support of Example 3, a spherical alumina support with a diameter of 5 +++jnφ was used mixed with the catalyst. Table 3 shows the butylene reaction rate, methacrolein selectivity, and yield at 24 hours and 5000 hours after starting the reaction.

Example 4 Diameter 5 trur+φ, length 5M, L according to the catalyst preparation method described in Example 1 of Japanese Patent Publication No. 49-3496
A catalyst (B15b04/C, Mo
04=171 (weight ratio)) was prepared.

Next, a supporting material 10 supported by molybdenum oxide prepared in Example 1 was placed in the lower part (raw material gas introduction part) of a stainless steel reaction tube with a diameter of 2'7wnφ and a height of 350 mmH.
- was filled. A mixture of 80 parts by weight of the catalyst and 20 parts by weight of the support was uniformly mixed onto this packed bed.
The packed bed (atomic ratio of molybdenum in the catalyst to molybdenum in the support was 1:0.35) was heated to 430°C, and the molar ratio of 1-butene:steam:air was 1:1:0. 1°: A mixed gas of 1. o A/min
sink at a flow rate of .

Catalytic oxidation reaction of 1-butene with contact time of 6.0 seconds
This was done continuously for Q hours. Table 4 shows the reaction rate of butene, selectivity of 1,3-butadiene, and yield at 24 hours and 5000 hours after starting the reaction.

Example 3 Example 4 was completely repeated, except that instead of the molybdenum oxide support of Example 4, a spherical alumina support with a diameter of 5 m and mφ was used mixed with the catalyst. At 24 hours and 5000 hours after starting the reaction, the reaction rate of butene, selection rate and yield of 1,3-butadiene were as shown in Table 4.

Table 4 Patent applicant: Ube Industries Co., Ltd. Continuation of page 1 0 shots clear person Hiroyuki Asada 5 U, 1978 Oaza Kogushi, Ube City Bukosan Co., Ltd. Central Research Laboratory 0 shots: Takeshi Yamao 5 U, 1978 Oaza Kogushi, Ube City Bukosan Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] When carrying out a catalytic reaction of olefins in a fixed bed reactor filled with a molybdenum-containing oxidation catalyst, a carrier in which molybdenum oxide is supported on a heat-generating inorganic substance that is substantially inert to the catalytic reaction is packed together with the molybdenum-containing oxidation catalyst. A method for sustaining the activity of a molybdenum-containing oxidation catalyst, characterized by carrying out a catalytic reaction.