JPH0245499B2 - - Google Patents

Description

[Detailed description of the invention]

[] BACKGROUND OF THE INVENTION The present invention relates to a method for improving the activity of a tellurium-containing metal oxide catalyst. In other words, the present invention relates to a method for producing tellurium-containing metal oxide catalysts with improved activity, particularly catalyst beds of such catalysts. Many tellurium-containing metal oxide catalysts are known. For example, a catalyst comprising oxides of molybdenum, zinc and tellurium as described in Japanese Patent Publication No. 41-7774, a catalyst comprising oxides of tellurium and cerium as described in Japanese Patent Publication No. 42-18447, and a catalyst as described in Japanese Patent Publication No. 43-6045. A catalyst consisting of oxides of molybdenum, tellurium, manganese and phosphorus,
Catalysts comprising oxides of iron, antimony, vanadium, molybdenum, tungsten and tellurium as described in JP-A No. 46-2804, catalysts comprising oxides of molybdenum, tellurium, antimony, cobalt and phosphorus as described in JP-A-54-141724 ,Special Public Service 1977-
Tellurium and molybdenum and tungsten, vanadium, chromium, manganese, and
Catalysts made of oxides of iron, cobalt, nickel, zinc, tin, bismuth, etc., catalysts made of oxides of tin, antimony, copper, iron, tellurium, etc. described in JP-A-55-94322, etc. oxidation, ammoxidation, or oxidative dehydrogenation reactions. For example, an oxidation reaction of propylene (or isobutylene) produces acrolein (or methacrolein), and an ammoxidation reaction produces acrylonitrile (or methacrylonitrile). Furthermore, in the oxidative dehydrogenation reaction of butene-1 or butene-2, butadiene is produced. In the oxidation, ammoxidation, or oxidative dehydrogenation reactions of these hydrocarbons, a decrease in activity is often observed during long-term reaction use, although the degree varies depending on the type of catalyst and conditions of use. There are various causes for such a decrease in activity, and countermeasures are being investigated from various angles. Such a phenomenon sometimes occurs even in metal oxide catalysts containing tellurium, and a decrease in activity may be accompanied by a decrease in the tellurium content in the catalyst. During the reaction, the catalyst undergoes irreversible reduction,
As a result, it is assumed that it escapes as tellurium, organic tellurium compounds, tellurium hydrates, etc., which have relatively high vapor pressure. However, in many cases, there is no direct relationship between the decrease in activity and the decrease in tellurium content, and the cause is not always clear. Whatever the cause, from a practical standpoint, it is important to develop catalysts that do not easily deteriorate, establish methods of using catalysts that do not easily deteriorate, and regenerate deteriorated catalysts. Various methods have been proposed to regenerate deteriorated catalysts, but most of them involve taking the catalyst out of the reactor and then subjecting it to various treatments. For example, the method for regenerating an antimony-containing oxide catalyst containing tellurium described in Japanese Patent Publication No. 52-42552, the method for regenerating an iron-antimony-based oxide catalyst containing tellurium described in JP-A-54-62193, An example of this is the method for regenerating an antimony-based composite oxide catalyst containing tellurium described in Japanese Patent No. 55-67872. When regenerating a deteriorated catalyst using these methods, it is necessary to temporarily stop the reaction and extract the catalyst, and the economic loss due to production stoppage during this period is large. It would be very advantageous if the performance could be restored by some method while the reaction is being carried out, or even if the reaction is stopped, without being extracted from the reactor. [] SUMMARY OF THE INVENTION Summary The present invention aims to provide a solution to the above points regarding tellurium-containing catalysts, and achieves this objective by contacting the tellurium component with the tellurium-containing catalyst in the gas phase from a tellurium component source. This is what we are trying to achieve. Therefore, in the method for improving the activity of a tellurium-containing metal oxide catalyst according to the present invention, a tellurium-containing metal oxide catalyst and at least one tellurium-containing solid selected from the group consisting of tellurium alone and tellurium-enriched catalyst are heated in a gas atmosphere. heating at temperatures up to 900°C in
It is characterized by: Effects According to the present invention, it is possible to reduce the change over time in the activity of a tellurium-containing metal oxide catalyst or to improve the selectivity of a degraded catalyst to a target product. Furthermore, surprisingly, the method of the present invention is effective even when applied to fresh catalysts (i.e., non-degraded catalysts), and therefore the method of the present invention goes beyond a mere catalyst regeneration method. Should. The method of the present invention can be applied when the catalyst is used in a fluidized reaction. That is, in a fluidized reaction, it is easy to extract a part of the catalyst or add the catalyst while the reaction is being carried out. This can be carried out continuously or intermittently, is easy to operate, and is routinely carried out industrially. Therefore, the tellurium-containing solid that is the catalyst activity improver of the present invention,
It is also possible and easy to add while carrying out a fluid reaction. Unlike the conventional catalyst regeneration method described above, this can be carried out while the reaction is being carried out, so there is no loss due to production stoppage. Of course, if the catalyst and the tellurium-containing solid according to the present invention are mixed before the start of the reaction and then the treatment according to the present invention is carried out, the same improvement in activity is observed. Such methods are also within the scope of the present invention. Further, even when the material is taken out from the reactor and subjected to the treatment according to the present invention, the activity is similarly improved, and such a method is also within the scope of the present invention. Although the mechanism by which the present invention exerts its effects is not clear, a small amount of volatile tellurium components are generated from tellurium-containing solids during heat treatment in a gas atmosphere (details will be described later), and this is caused by carbon dioxide and carbon monoxide on the catalyst. It may be possible to infer that the selectivity of the desired product can be increased by poisoning the active sites involved in the production of by-products such as, and inhibiting their production. When using the tellurium-containing solids of the present invention, the time required for the onset of effects is relatively short. Therefore, the poisoning of the by-product producing active site is
It appears to be effective by volatilizing a very small amount of tellurium component. Moreover, the durability of the effect is relatively good. Note that this mechanism is based on speculation, and its details are not yet sufficiently clear.
Accordingly, the means of achieving the object of the present invention, which involves contacting the aforementioned tellurium component from a tellurium component source with a tellurium-containing catalyst, should also be understood from this perspective. [] Detailed description of the invention 1 Tellurium-containing metal oxide catalyst The tellurium-containing catalyst targeted by the present invention is an unsaturated aldehyde produced by oxidation, ammoxidation or oxidative dehydrogenation of hydrocarbons and other organic compounds,
Particular preference is given to those used in the production of unsaturated nitriles or hydrogen cyanide, or diolefins. As mentioned above, various types of tellurium-containing metal oxide catalysts are already known. The method of the present invention can be equally applied to these known tellurium-containing metal oxide catalysts. Specifically, it is a tellurium-containing metal oxide catalyst represented by the following empirical formula containing at least one member selected from the group consisting of antimony, molybdenum, and vanadium and tellurium. A _a Te _b C _c D _d E _e O _x where A is at least one element selected from the group consisting of Sb, Mo and V, C is B, P,
At least one element selected from the group consisting of As, Bi, S and Se, D is Li, Na, K,
At least one element selected from the group consisting of Rb, Cs and Tl, E is Mg, Ca, Sr, Ba,
Y, La, Ce, U, Ti, Zr, Nb, Ta, Cr,
W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd,
Os, Ir, Pt, Cu, Ag, Zn, Cd, Al, Ga,
At least one element selected from the group consisting of In, Ge, Sn, and Pb and O represent oxygen, and subscripts a, b, c, d, e, and x represent atomic ratios, and when a=10 b=0.01-5 (preferably 0.05-3), c=0-10 (preferably 0.05-3)
8), d=0-5 (preferably 0-3), e=0
~60 (preferably 0.1 to 50), x is the number of oxygen atoms in the oxide formed by combining each component. The above tellurium-containing metal oxide catalyst is silica,
It may be supported on various carriers such as silica/alumina, alumina, silica/titania, and titania. Particularly preferred tellurium-containing metal oxide catalysts to be targeted in the present invention are those in which the state of the contained tellurium is such that the presence of metal tellurium or tellurium oxide is recognized when the catalyst is subjected to X-ray diffraction. It is something that cannot be avoided. The tellurium-containing metal oxide catalyst targeted by the present invention is preferably in a form for fluidized reactions (in terms of particle size, it is preferably in the range of 5 to 200 microns). This is because it is easy to apply the method of the present invention during use in a fluid reaction and it is highly effective. Reactions to be carried out using such tellurium-containing metal oxide catalysts, particularly flow reactions, are typically hydrocarbon oxidation, ammoxidation, and oxidative dehydrogenation reactions. 2 Tellurium-Containing Solid The tellurium-containing solid that is the activity enhancer used in the present invention can be of various types. As mentioned above, in a preferred embodiment of the present invention, the target catalyst whose activity is to be improved is for a fluidized reaction, and the treatment of the present invention is carried out while the fluidized reaction is being carried out. Therefore, the tellurium-containing solid is also fluidized. It is preferable that the catalyst be in the form of fine particles or powder, and especially that it can be fluidized under the same conditions as the catalyst in question. 1) Type and Production Specific examples of the tellurium-containing solid of the present invention include tellurium alone or a tellurium-enriched catalyst. A tellurium-enriched catalyst is a catalyst containing an enriched tellurium component, and has a higher tellurium content than the catalyst used in the reaction. This tellurium-enriched catalyst can be produced by any known method. Furthermore, it can also be produced by using a catalyst prepared by any known method as it is or using it in the reaction, impregnating it with a liquid containing a tellurium component, drying and calcining it. A tellurium-containing metal oxide catalyst is impregnated with a tellurium component, dried and calcined to produce a tellurium-containing solid according to the present invention, i.e., a tellurium-enriched catalyst,
When producing the powder, for example, the method described in the above-mentioned Publication No. 52-42552 may be followed. However, in the case of the present invention,
For example, even if an antimony-based metal oxide catalyst is impregnated with a tellurium component, it is not a necessary condition that the tellurium component be solidly dissolved in the constituent crystalline phase of the base catalyst. The following method is preferred for preparing an impregnating solution containing the tellurium component necessary for impregnating the catalyst with the tellurium component. (1) Oxidation of tellurium metal with nitric acid (2) Dissolution of tellurium dioxide and tellurite acid in nitric acid (3) Dissolution of telluric acid in water or nitric acid (4) Oxidation of tellurium metal with ions selected from the following groups and (or) oxidation of hydrogen peroxide in the presence of a compound (a) ammonium ion (b) alkali metal ion (c) oxide of at least one metal selected from the group consisting of vanadium, molybdenum and tungsten, oxygen acid or oxygen (5) Oxidation of tellurium metal with hydrogen peroxide in the coexistence of nitric acid (6) Oxidation of tellurium metal with nitric acid and then oxidation of hydrogen peroxide in the coexistence of iron ions These solutions can be used alone or with some other components. The tellurium-containing solid used in the present invention can be obtained by impregnating the catalyst as a mixed solution and drying it, or by further calcining it. In this case, the firing temperature is effective from a relatively low temperature to remove moisture, and is preferably 850°C or lower, preferably 750°C or lower. In addition to these, a tellurium-enriched medium can also be prepared by mixing and heating tellurium and/or a tellurium compound or a substance containing the same and a catalyst. Many tellurium compounds, including tellurium alone, have relatively low melting points or high vapor pressures, so this method can be used in some cases. Another method for preparing tellurium-containing solids is to support the tellurium component on the catalyst by contacting the vapor of tellurium or a tellurium compound as it is or with other gas and bringing it into contact with the catalyst. obtain. The tellurium component in the tellurium-containing solid is usually a tellurium compound as described above, that is, one that does not contain metals or metalloids other than tellurium (oxides, oxygen acids, and organic compounds), but if necessary, metals or It may also contain metalloids and others. In other words, this tellurium-enriched catalyst contains, in addition to tellurium, alkali metals, alkaline earth metals, chromium, molybdenum, tungsten, vanadium, manganese,
Rhenium, iron, cobalt, nickel, palladium, copper, silver, zinc, cadmium, rare earth metals, boron, aluminum, gallium, indium, thallium, carbon, silicon, germanium, tin, lead, phosphorus, arsenic, antimony, bismuth, It does not matter if it contains oxygen, sulfur, selenium, etc. The types and contents of these components other than tellurium are permissible within a range that does not adversely affect the selectivity of the target product when mixed with the target catalyst and subjected to activity improvement treatment. Generally, when the desired reaction is carried out using such tellurium-containing solids alone, even if they have activity and the selectivity of the desired product is poor, if the reaction rate is lower than that of the catalyst used, Alternatively, even if the reaction rate is somewhat high at the beginning of use, if the reaction rate decreases quickly, it can be used without problems. With this in mind, therefore, the relative proportions of tellurium and these elements can be varied within a wide range. In other words, when these elements (or the sum of elements) are represented by A, A/
Tellurium (weight ratio) is 0 to 100, preferably 0
~50 (however, A excludes oxygen). 2) Tellurium content As mentioned above, during the treatment according to the present invention, the tellurium component seems to be converted into volatile compounds in the system to exert its effect, and in fact, the surface tellurium concentration of the tellurium-containing solid used is If it is too low, it will take time for the effect to appear,
The moderation of the effect also becomes smaller. If the tellurium content is too low, a large amount of tellurium-containing solid must be added in order to achieve the desired effect and maintain the effect. Moreover, since this is not the catalyst itself for the intended reaction, when carrying out the present invention while the fluid reaction is being carried out for the target catalyst, the catalyst may need to be diluted depending on the case.
It may happen that the reaction capacity is insufficient to sufficiently proceed with this fluid reaction. Taking these matters into consideration, it is preferable that the tellurium-containing solid has a tellurium surface concentration of 0.05 atomic % or more, preferably 0.1 atomic % or more, and a tellurium content of 1 weight % or more.
The surface concentration of tellurium in the tellurium-containing solid here was measured by X-ray electron spectroscopy (XPS). (Details later). 3) Physical properties The physical properties of the tellurium-containing solid are important when this activity enhancer is applied when the target catalyst is in a fluidized reaction system, or when the solid itself is used in a fluidized state. is an element. That is, if the tellurium-containing solid is too light compared to the catalyst, it will be more likely to scatter out of the system during the flow reaction and will be lost without effectively achieving the object of the present invention. On the other hand, if the tellurium-containing solid is too heavy compared to the target catalyst, there is no problem in terms of its own loss, but if too much is added to the fluidized reaction system of the target catalyst, the fluidization state will deteriorate and the reaction results will deteriorate. Caution is required as it may decrease. Therefore, especially when carrying out the method of the present invention while carrying out a fluid reaction with a target catalyst, the tellurium-containing solid should have a particle size relatively close to that of the catalyst used, and the tellurium-containing solid should have a particle size relatively close to that of the catalyst. bulk density) is in the range of 0.05 to 8, preferably 0.2.
It is desirable that the value be in the range of 6 to 6. The fluid reaction catalyst to be used in carrying out the present invention as described above is preferably one having a bulk density of 0.1 to 3 [g/ml] and a particle size of about 5 to 200 microns. 3 Activity Improvement Treatment The activity improvement treatment of the tellurium-containing metal oxide catalyst according to the present invention is carried out by heating the catalyst and the above-mentioned tellurium-containing solid at a temperature of up to 900° C. in a gas atmosphere. Both the target catalyst and the tellurium-containing solid are preferably in a fluid state. In this case, it is most preferable that the fluidized state of the catalyst is achieved by performing a fluidized reaction on the catalyst. This is because in such an embodiment, the present invention can be carried out without stopping this flow reaction. The method of the present invention can also be commonly applied to cases where the target catalyst and tellurium-containing solid are mixed and heated to form a solid bed. However, the effect is particularly great when the treatment of the present invention is carried out in a fluidized state using a fluidized catalyst. Under fluidized conditions, catalyst movement can be quite extensive, which is thought to be the reason for the greater effect. The gas atmosphere for heating the target catalyst and the tellurium-containing solid (in the case of carrying out the process of the present invention in a fluidized state, it goes without saying that this becomes a fluidizing gas) includes nitrogen, oxygen, carbon dioxide, Examples include inert or oxidizing gases such as water vapor, mixed gases of oxygen and reducing gases such as hydrocarbons, ammonia, and carbon monoxide, and others. These gases may simply be heat treatment atmosphere gases, but in the case of activation with tellurium-containing solids during the flow reaction of the target catalyst in accordance with the preferred embodiment of the present invention. This is the reaction atmosphere for the fluid reaction. For example, a gas mixture of a hydrocarbon or alcohol (e.g. propylene or methanol), ammonia and oxygen (especially air) (and possibly water vapor) is a reaction gas during the ammoxidation of a hydrocarbon or alcohol, from which the ammonia is removed. This is the reaction gas during oxidation or oxidative dehydrogenation. This gaseous atmosphere must not be too reducing. That is, when using reducing gases such as hydrocarbons, ammonia, and carbon monoxide, these cannot be used alone. When the temperature is increased in the presence of only these reducing gases,
The catalyst itself undergoes reduction, resulting in deterioration of performance. These reducing gases must be used in the presence of enzymes. However, the term "reducing gas" here means a gas capable of reducing the catalyst. Therefore, depending on the temperature conditions, the reducing gases mentioned above may also be treated as inert gases.
For example, hydrocarbons and other organic compounds, ammonia, carbon monoxide, etc. are generally
Since its reducing power against the catalyst used in this type of reaction is small, it can be treated as an inert gas. In this case, coexistence of oxygen is not essential. As the hydrocarbons and other organic compounds, olefins, alcohols, aldehydes, etc. are preferably used. Saturated hydrocarbons should rather be placed in the category of inert gases for catalyzing reactions of this type. These reducing gases can be used as a mixture in the presence of oxygen or as a mixture with an inert gas. This tellurium-containing solid has the following effects on the target catalyst:
It is preferable to add 0.01% by weight or more, preferably 0.05 to 30% by weight. Within this range, the object of the present invention can be achieved without negatively impacting the performance of the catalyst used. When a tellurium-containing solid with a high tellurium concentration is used, a relatively small amount is used, and when a tellurium-containing solid with a low tellurium concentration is used, a relatively large amount is used. As mentioned above, when a tellurium-enriched catalyst is used as the tellurium-containing solid, it can be mixed and used in any proportion unless it has particularly abnormal activity. The activation treatment temperature is 900°C or lower.
This is because if the temperature exceeds 900°C, the catalyst itself will deteriorate due to sintering, crystallization, etc. Relatively high temperatures occur when the process is carried out in the presence of inert gases such as nitrogen, oxygen, carbon dioxide, and water vapor, while when the process is carried out in the coexistence of hydrocarbons, other organic compounds, reducing gases such as ammonia and carbon monoxide, and oxygen. A relatively low temperature is selected. However, if the form of tellurium in the tellurium-containing solid has a relatively high vapor pressure, such as gold metal tellurium or organic tellurium compounds, or contains these, treatment is effective at a low temperature and in a short time regardless of the type of gas. It is. In this case, care must be taken because if the temperature is too high, some negative effects such as a decrease in the reaction rate may occur. When using water vapor as the gas atmosphere,
If the temperature exceeds 700°C, the performance may deteriorate due to sintering of the catalyst, so care must be taken when selecting the temperature during implementation. The lower limit of the treatment temperature is arbitrary as long as the effects of the present invention are recognized, but it is generally about 200°C. In addition, the processing conditions (temperature and time) of the present invention
varies depending on the tellurium-containing solid used and the gas used, so the optimum conditions should be determined experimentally based on the combination. Further, when carrying out the present invention while carrying out the reaction on the target catalyst, the conditions may be the same as those commonly used in oxidation, ammoxidation, or oxidative dehydrogenation reactions of hydrocarbons. When carrying out the method of the present invention while carrying out oxidation, ammoxidation, or oxidative dehydrogenation of hydrocarbons or other organic compounds, the molar ratio of the supplied gas is such that the molar ratio of hydrocarbons or other organic compounds/oxygen/ammonia is: 1/0.3
~10/0~5, and the reaction temperature is selected in the range of 300~600°C. 4 Examples Hereinafter, the effects of the present invention will be shown by Examples and Comparative Examples. Note that the yield and selectivity of the target product in this specification are based on the following definitions. Yield (%) = Carbon weight of generated target product / Carbon weight of supplied raw material hydrocarbon x 100 Selectivity (%) = Carbon weight of generated target product / Carbon weight of reacted raw material hydrocarbon x 100 The activity test conditions are as follows. (1) Ammoxidation reaction of propylene 1200g to 1800g of catalyst is placed in a fluidized bed reactor with an inner diameter of 5cm (2 inches) and a height of 2m.
Select and fill as appropriate between g. A gas having the following composition is fed into this reactor so that the apparent linear velocity is 15 cm/sec. The reaction pressure is normal pressure. O ₂ (supplied with air)/propylene = 2.10 (mole ratio) NH ₃ /propylene = 1.15 (mole ratio) However, the contact time is defined as follows. Contact time = Catalyst packing volume [liters] ^* /Supplied gas flow rate [liters/sec] [sec] *Catalyst coarse density standard (2) Methanol ammoxidation reaction Use the same reactor as in the previous section for propylene ammoxidation. The apparent linear velocity of a gas of the following composition to this reactor is
Feed at a rate of 15cm/sec. The reaction pressure is normal pressure. O ₂ (supplied with air)/methanol = 2.10 (mole ratio) NH ₃ /methanol = 1.20 (mole ratio) H ₂ O/methanol = 2.00 (mole ratio) N ₂ /methanol = 5.00 (mole ratio) Definition of contact time is the same as the previous section. Example 1 A fluidized catalyst having the empirical formula Fe ₁₀ Sb ₂₅ W _0.25 Te _1.0 O _67.8 (SiO ₂ ) ₃₀ was used in the ammoxidation reaction of propylene. During the reaction, the resistance decreased due to a decrease in the (oxygen/propylene) molar ratio. That is, the initial acrylonitrile yield was 80.3
%, but it dropped to 78.6%. 10% of this catalyst was extracted and replaced with a separately prepared tellurium component enriched catalyst. Using the tellurium-containing solid and the tellurium-containing solid mixture thus obtained, a propylene ammoxidation reaction was carried out according to the activity test conditions (1) described above. As a result, the acrylonitrile yield improved and reached 80.1% after 3 hours. after that,
Although the reaction was continued for 5 hours, this level was maintained. The tellurium-enriched catalyst used here was prepared as follows. The experimental formula was Fe ₁₀ Sb ₂₅ W _0.25 Te _1.0 O _67.8 (SiO ₂ ) ₃₀ , and 2 kg of a fluidized catalyst whose activity had decreased due to long-term reaction was taken. 15.1 g of metallic tellurium powder was added and dissolved in 540 g of 45% nitric acid. 45% nitric acid was added to this to make 440 ml, which was poured onto the aged catalyst and mixed well for about 1 hour. This was fired at 200°C for 2 hours and then at 350°C for 4 hours. The tellurium content of this tellurium-enriched catalyst is 2.65% by weight
It is. Example 2 A fluidized catalyst with the empirical formula Fe ₁₀ Sb ₂₅ Cu _0.5 Mo _0.25 Te _1.0 O _68.3 (SiO ₂ ) ₆₀ was packed in a fluidized bed reactor with an inner diameter of 20 cm (8 inches), and a propylene ammoxidation reaction was carried out. I did this. Apparent linear velocity of gas supplied to reactor 18cm/sec Reaction pressure 0.5Kg/cm ² G Supply gas molar ratio O ₂ (supplied as air)/propylene
2.2 (molar ratio) NH ₃ /propylene 1.1 (molar ratio) Reaction temperature 450°C When the reaction was carried out under the above reaction conditions for 670 hours, the acrylonitrile yield decreased and the production of carbon dioxide increased. I pulled out this deteriorated catalyst and took 2 kg of it. Metal tellurium powder is added at 0.2% to this deteriorated catalyst.
Additionally, a fluidized bed reactor with an internal diameter of 5 cm (2 inches) was filled and fluidized using nitrogen gas. The temperature was gradually increased and kept at 300°C for 1 hour. The catalyst thus treated was subjected to the ammoxidation reaction of propylene. Under the above activity test conditions (1), the acrylonitrile yield of the degraded catalyst was 76.3%, but the acrylonitrile yield of the catalyst treated in this way was improved to 77.8%. Example 3 A propylene ammoxidation reaction was carried out using a catalyst whose empirical formula was Fe ₁₀ Sb ₂₅ Cu ₃ Mo _0.5 W _0.3 Te _1.5 O _73.4 (SiO ₂ ) ₆₀ . The catalyst deteriorated because the oxygen/propylene molar ratio decreased during the reaction. As a result, although the standard conditions were restored, the acrylonitrile yield had decreased to 83.2%. This catalyst was mixed with a separately prepared tellurium-enriched catalyst at a mixing ratio of 7%, and a reaction was carried out according to the activity test conditions (1) above. The acrylonitrile yield gradually increased and reached 85.0% after 3 hours of reaction. The tellurium-enriched catalyst used here was prepared as follows. 1.5 kg of the deteriorated catalyst generated in Example 2 was taken. Add approximately 13.5 g of metallic tellurium little by little to 45% nitric acid and dissolve. 3.75 g of ammonium paramolybdate in 10 g of pure water
ml and add this to the above tellurium nitric acid solution. After adding pure water and adjusting the liquid volume to 420ml,
In addition to the aged catalyst, the mixture was thoroughly mixed in a blender for 1 hour. After heat treatment at 200℃ for 5 hours and 400℃ for 2 hours,
It was baked at 550°C for 4 hours. Example 4 The following experiment was conducted using the same catalyst as in Example 3. The catalyst deteriorated because the oxygen/propylene molar ratio decreased during the reaction. As a result, although the standard conditions were restored, the acrylonitrile yield had decreased to 82.8%. To this catalyst, 3% of the same tellurium-enriched catalyst as in Example 3 was added and the reaction was carried out again. The acrylonitrile yield gradually improved and reaction 5
After hours, it was 84.8%. The contents of Examples 1 to 4 above are summarized in Table 1 below.

【table】

[Table] The tellurium surface concentration in Table 1 is determined by electron spectroscopy (X-
It was measured by line photospectroscopy) and expressed as atomic % of the detected element. A PH1550 type device was used for the measurement, and the sample was supported on a copper tape. Among the tellurium-containing solids used here, the activity test results for the tellurium-enriched catalyst alone are also listed in the table. In both cases, the acrylonitrile yield is lower than that of the catalyst, and the reaction rate is also lower. It was unexpected that when the reaction was carried out with the addition of such a tellurium-enriched catalyst, the reaction performance would be improved rather than degraded compared to when the catalyst was used alone. Example 5 A fluidized catalyst with the empirical formula Fe ₁₀ Sb ₂₅ Cu _0.5 Mo _0.25 Te _1.0 O _68.3 (SiO ₂ ) ₆₀ was packed into a fluidized bed reactor with an inner diameter of 20 cm (8 inches), and the ammoxidation reaction of propylene was carried out. I did it. Apparent linear velocity of gas supplied to reactor 1cm/sec Reaction pressure 0.5Kg/cm ² G Supply gas molar ratio O ₂ (supplied as air)/propylene
2.2 (molar ratio) NH ₃ /propylene 1.1 (molar ratio) Reaction temperature 450°C When the reaction was carried out under the above reaction conditions for 670 hours, the acrylonitrile yield decreased and the production of carbon dioxide increased. I pulled out this deteriorated catalyst and took 2 kg of it. This degraded catalyst was mixed with a separately prepared tellurium-enriched catalyst at a concentration of 10%, and a reaction was carried out according to the activity test conditions (1). The acrylonitrile yield gradually improved, reaching 78.1% after 3 hours of reaction. The yield of acrylonitrile was 76.3% when the reaction was carried out according to the activity test conditions (1) above using only the degraded catalyst. The tellurium-enriched catalyst used in this example was prepared as follows. Take 1 kg of a fluidized catalyst (undegraded before use) having the above experimental formula. 56g of telluric acid in water
0.27 liters and this solution was mixed well with the catalyst. Then, after drying at 120°C for 5 hours, it was fired at 350°C for 2 hours. The tellurium content in the tellurium-enriched catalyst thus prepared is 4.4%. Example 6 A fluidized bed catalyst of Te _0.5 Mo ₁₀ W ₁ Fe ₂ Co ₃ Ni ₃ Bi ₁ O _43.5 (SiO ₂ ) ₅₀ was used for the ammoxidation reaction of methanol according to the activity test conditions (2). The yield of hydrocyanic acid gradually decreased due to the reaction in which the oxygen/methanol molar ratio of the feed gas was lowered. Although this molar ratio was returned to the standard conditions for the activity test, the hydrocyanic acid yield, which was initially 84.0%, had decreased to 81.9%. To this deteriorated catalyst, 0.1% of metallic tellurium powder was added and the reaction was carried out again. The hydrocyanic acid yield improved with the passage of time, reaching 83.5% after 3 hours.

【table】

Claims (1)

[Claims] 1. A tellurium-containing metal oxide catalyst and at least one tellurium-containing solid selected from the group consisting of tellurium alone and tellurium-enriched catalyst in a gas atmosphere.
Characterized by heating at temperatures up to 900℃,
A method for improving the activity of tellurium-containing metal oxide catalysts. 2. The method according to claim 1, wherein the tellurium-containing solid is present in a proportion of 0.01% by weight or more based on the tellurium-containing metal oxide catalyst. 3. The method according to claim 1 or 2, wherein the tellurium content of the tellurium-containing solid is 1% by weight or more. 4 The tellurium-containing metal oxide catalyst has a particle size of 5 to
4. A process according to any of claims 1 to 3, wherein the catalyst is fluidized in the range of 200 microns and is mixed with the tellurium-containing solid in its fluidized state. 5. The method according to any one of claims 1 to 4, wherein the ratio of the bulk density of the tellurium-containing solid to the bulk density of the tellurium-containing metal oxide catalyst is in the range of 0.2 to 6. 6 The tellurium-enriched catalyst as a tellurium-containing solid is
The method according to any one of claims 1 to 5, wherein a metal oxide catalyst or a used metal oxide catalyst is enriched with a tellurium component. 7 The tellurium-enriched catalyst is obtained by impregnating a tellurium-containing metal oxide catalyst with a tellurium-containing solution prepared by any of the methods (1) to (6) below, and drying this.
Claims 1 to 6, which are prepared by firing at a temperature of 300°C to 850°C.
The method described in any of the paragraphs. (1) Oxidation of tellurium metal with nitric acid, (2) Dissolution of tellurium dioxide or tellurite acid in nitric acid, (3) Dissolution of telluric acid in water or nitric acid, (4) Tellurium metal selected from the following group. Hydrogen peroxide oxide in the presence of ions and/or compounds (a) ammonium ions (b) alkali metal ions (c) oxides and oxygen acids of at least one metal selected from the group consisting of vanadium, molybdenum and tungsten. or oxygen salt (5) Metal tellurium is oxidized with hydrogen peroxide in the coexistence of nitric acid (6) Metal tellurium is oxidized with nitric acid and then hydrogen peroxide is oxidized in the coexistence of iron ions. The method according to any one of claims 1 to 7, which is used for producing unsaturated aldehydes, unsaturated nitriles, hydrogen cyanide, or diolefins by oxidation, ammoxidation, or oxidative dehydrogenation reactions. Method.