JPH0141135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION The present invention relates to an improved process for ammoxidation of organic compounds using tellurium-containing metal oxide catalysts. Many tellurium-containing metal oxide catalysts are known. For example, catalysts consisting of molybdenum and tellurium oxides described in Japanese Patent Publication No. 37-11008, molybdenum described in Japanese Patent Publication No. 41-7774,
Catalyst consisting of tellurium and zinc oxides, Tokkosho
Catalysts comprising oxides of tellurium and cerium described in Japanese Patent Publication No. 42-18447, catalysts comprising oxides of molybdenum, tellurium, manganese, and phosphorous described in Japanese Patent Publication No. 43-6045, catalysts comprising oxides of molybdenum, tellurium, manganese, and phosphorus described in Japanese Patent Publication No. 46-2804. Catalysts consisting of oxides of iron, antimony, vanadium, molybdenum, tungsten and tellurium,
Catalysts made of oxides of molybdenum, tellurium, antimony, cobalt and phosphorous described in JP-A-54-141724, catalysts made of oxides of molybdenum, tellurium and tungsten, vanadium, etc. described in JP-A-55-16971; are known to be useful in ammoxidation reactions of organic compounds. In the ammoxidation reaction of these organic compounds, a decrease in activity is often observed during long-term reaction use, although the degree varies depending on the type of catalyst or 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 in metal oxides containing tellurium, and a decrease in activity may be accompanied by a decrease in tellurium content in the catalyst.
It is assumed that the catalyst undergoes irreversible reduction during the reaction, and as a result escapes as tellurium alone, tellurium hydride, organic tellurium compound, tellurium hydrate, etc., which have a relatively high vapor pressure. However, there is often no direct relationship between the decrease in activity and the decrease in tellurium content, and the cause is not necessarily 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 for regenerating 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, etc. be. When regenerating a deteriorated catalyst using these methods, it is necessary to temporarily stop the reaction and extract the catalyst from the reactor, and the economic loss due to production stoppage during this period is large. It would be very advantageous if the performance of the catalyst could be restored in some way, either while the reaction is running or even when the reaction is stopped, without removing the catalyst from the reactor. [] Summary of the Invention In order to solve the above-mentioned problems regarding the ammoxidation catalyst of these tellurium-containing metal oxides, the present invention aims to provide a solution to the above-mentioned problems by continuously supplying the ammoxidation catalyst from outside the reaction system to the reactor in the vapor phase while carrying out the reaction. The objective is to be achieved by introducing the tellurium component either periodically or intermittently. Therefore, the method for improving the activity of a tellurium-containing metal oxide catalyst according to the present invention uses this catalyst to
A method for carrying out ammoxidation of organic compounds at a temperature of 500°C to 500°C, which is characterized by continuously or intermittently feeding tellurium alone or a tellurium compound into a reactor in the vapor phase. Effects According to the present invention, it is possible to improve the selectivity of the target product of a tellurium-containing metal oxide catalyst, reduce the change over time, or improve the selectivity of the target product of a degraded catalyst. In addition, the method of the present invention can be carried out safely while carrying out the reaction, and therefore is industrially extremely easy to implement and economical. The method of the present invention can be applied to both fixed bed reactions and fluidized bed reactions, but is particularly effective in fluidized bed reactions. The feed of the tellurium component may in any case be continuous or intermittent. It can be selected appropriately while checking the reaction results. It is not clear why the effect is greater in the fluidized bed reaction than in the fixed bed reaction, but in the case of the fixed bed reaction, there is a distribution in the concentration of the tellurium component deposited on the catalyst in the axial direction of the reactor. In the case of a fluidized bed reaction, it may be important that the catalyst is thoroughly mixed within the reactor, so that the concentration of the tellurium component in the catalyst is averaged out without large deviations. The mechanism by which the present invention exerts its effects is not necessarily clear. However, some or most of the tellurium alone or tellurium compound fed into the reaction zone is deposited on the catalyst, which leads to catalyst by-products such as carbon dioxide, carbon monoxide,
It may be possible to infer that by poisoning active sites that produce hydrocyanic acid and suppressing their production, the relative selectivity of the desired product may be increased. In addition, the effects of the present invention appear quickly;
Moreover, the sustainability of the effect is also good. [] Detailed description of the invention 1 Tellurium-containing metal oxide catalyst The tellurium-containing metal oxide catalyst used in the present invention is:
Various ammoxidation catalysts for organic compounds or improved catalysts thereof are disclosed in the above-mentioned patent publications, etc., and the method of the present invention is equally applicable to these known tellurium-containing metal oxide catalysts. can do. 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, and C is B, P, As,
At least one element selected from the group consisting of Bi, S and Se; D is at least one element selected from the group consisting of Li, Na, k, 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,
At least one element selected from the group consisting of Zn, Cd, Al, Ga, In, Ge, Sn and Pb and O
indicate oxygen, and the subscripts a, b, c, d, e
and x indicates the atomic ratio; when a=10, b=0.01
~5 (preferably 0.05-3), c=0-10 (preferably 0.05-8), d=0-5 (preferably 0-3),
e=0 to 60 (preferably 0.1 to 50), and x is the number of oxygen atoms in the oxide formed by combining each component. The above tellurium-containing metal oxide catalysts include silica, silica-alumina, alumina, silica-titania,
It may be supported on various carriers such as titania. The shape of the catalyst may be arbitrary, but in the case of a fixed bed reaction, catalysts of various shapes such as pellets or spheres of several millimeters are used. Additionally, in the case of fluidized bed reactions, catalyst particles having a particle size in the range of 5 to 200 microns are used. 2 Tellurium component 1 Form The tellurium component fed into the reaction zone in the vapor phase may be in the form of simple tellurium, tellurium monoxide, tellurium dioxide, tellurium trioxide, tellurous acid, telluric acid, hydrogen telluride, or telluriums, Examples include organic tellurium compounds such as alkyl tellurides and telluroxides. These tellurium elements and tellurium compounds are conveniently entrained in the feed gas for ammoxidation of organic compounds. The supply gas consists of organic compound vapor, oxygen, ammonia, and other diluting gases such as nitrogen, water vapor, helium, and exhaust gas after recovering the desired product from the reaction product gas. It can be entrained in one or more mixed gases. Oxides and hydrates of tellurium have relatively low vapor pressures, but hydrates of tetravalent tellurium oxides (tellurium dioxide) have somewhat high vapor pressures. For this reason, it may be convenient to use water vapor or a water vapor mixed gas as the entrained gas. In addition, simple tellurium, hydrogen telluride, organic tellurium compounds, etc. have high vapor pressures and are therefore easy to use. Various methods can be considered for introducing the tellurium component into the reactor, but a predetermined amount of the tellurium component may be flowed down or sprayed into the flow path of the above-mentioned supply gas. Alternatively, it is also possible to set the amount of inflow by placing tellurium alone or a tellurium compound as is or supported on a suitable support in the flow path of the entrained gas, and adjusting its vapor pressure. It is also possible to apply a method of converting the compound into a compound having a higher vapor pressure by reacting with a portion of the supplied gas and then supplying the compound. For example, by making tellurium oxide exist under the necessary temperature conditions and introducing a reducing gas into it, hydrogen telluride, methantellol, ethantellol, propanetelol, which has a high vapor pressure, can be extracted. This is a method in which organic tellurium compounds such as rolls are generated and delivered. As the reducing gas used for this purpose, an organic compound serving as a raw material for the desired reaction or ammonia may be used, or a small amount of hydrogen, olefins, alcohols, etc. may be used for this purpose only. Further, the tellurium component is fed into the reactor in a vapor phase, but there is no problem even if part of the tellurium component is mixed with liquid droplets or powder. In many cases, the temperature inside the reactor is higher than that in the supply gas line, so even if a small amount of these substances are mixed in, there is no problem because they will immediately turn into vapor when they enter the reaction system. 2. Amount of tellurium fed The amount of tellurium alone or a tellurium compound fed can be varied depending on the metal oxide catalyst used, the target reaction, and the reaction conditions. If the amount fed is small, the effect will be small and it will take time for the effect to appear, while if it is too large, negative effects will occur. The most reliable way to adjust the amount of feed is to feed tellurium alone or a tellurium compound little by little.
The method is to follow the progress of the reaction results, and when the desired level is reached, the amount of feed is reduced or stopped, and this is repeated as necessary. If the amount of tellurium component fed is too large, a decrease in reaction rate generally appears first. In the case of a decrease in activity due to excessive tellurium deposition on the catalyst, if the effect is mild, it can be gradually recovered by stopping the feed of the tellurium component and continuing the reaction. However, if the degree of decrease is large, it may be necessary to partially replace the catalyst, so care must be taken. The feed amount of the tellurium component relative to the total amount of reaction supply gas is preferably in the range of 10 ^-5 to 10 ² [mg/],
In addition, the amount of tellurium component fed at one time is limited to a maximum of
The amount should be about 10 [mg/g-catalyst/hour]. It is desirable that the introduced tellurium component comes into uniform contact with the packed catalyst, and the feeding rate should be determined with this point in mind. Even if a large amount is fed at once, there is no point in passing through the catalyst layer as it is and increasing the proportion of loss due to scattering outside the system. Furthermore, depending on the form of the compound, some are easily deposited on the catalyst and others are not, so this point should also be taken into consideration. Elemental tellurium, tellurium hydride, organic tellurium compounds, etc., which have a relatively high vapor pressure, are very easily oxidized, and when they come into contact with the metal oxide catalyst present in the ammoxidation reaction zone of organic compounds, they are immediately oxidized or decomposed by oxidation. Since it is deposited on the catalyst, efficiency is good even if the amount fed is somewhat large, as long as the amount fed is not excessive. As mentioned above, the optimum value for the total feed amount of the tellurium component varies depending on the catalyst used, the type and form of the tellurium component fed, the type of reaction, and the reaction conditions. However, the approximate range is that the increase in the tellurium content of the packed catalyst due to the feed of the tellurium component is
0.001 to 15% by weight, preferably 0.01 to 10
% by weight. 3 Ammoxidation method The activation treatment of the present invention is carried out while carrying out ammoxidation of an organic compound, and the conditions for the ammoxidation reaction are known. The approximate range is as follows. The molar ratio of the supplied gas is organic compound/oxygen/ammonia (molar ratio) of 1/0.3-10/0.5-5, and if necessary, nitrogen, water vapor,
Carbon dioxide gas, carbon monoxide, etc. can also be added. The reaction temperature is 300-500℃, and the apparent contact time is
It is 0.1~20 seconds. 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 organic compound x 100 Selectivity (%) = Carbon weight of generated target product / Carbon weight of reacted raw material organic compound x 100 The conditions for the activity test are as follows. (1) Propylene ammoxidation method A catalyst is packed into a fluidized bed reactor with an inner diameter of the catalyst flow section of 5 cm and a height of 2 m, and a gas having the following composition is fed so that the apparent linear velocity is 15 cm/sec. . The reaction pressure is normal pressure. O ₂ (supplied with air)/propylene = 2.1 (mole ratio) NH ₃ /propylene = 1.15 (mole ratio) However, the contact time is defined as follows. Contact time (sec) = Catalyst packing volume ^* () / Supply gas flow rate (/sec) (*Based on catalyst roughness density) (2) Methanol ammoxidation reaction Use the same reactor as the propylene ammoxidation reaction in the previous section . 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. (3) Ammoxidation reaction of toluene A catalyst is packed in the same fluidized reactor as in the previous section, and gas with the following composition is fed so that the apparent linear velocity is 15 cm/sec. The reaction pressure is normal pressure. O ₂ (supplied with air)/toluene 2.5 (mole ratio) NH ₃ /toluene = 1.5 (mole ratio) H ₂ O/toluene = 2.5 (mole ratio) The definition of contact time is the same as in 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 activity decreased due to a decrease in the oxygen/propylene molar ratio of the feed gas. In other words, initially the yield of acrylonitrile is
What used to be 80.3% dropped to 79.0%. Therefore, tellurium elemental vapor was introduced into the ammonia supply gas line and sent into the reactor together with the ammonia gas. Total tellurium feed gas (air +
The concentration in propylene + ammonia) is 0.25
It was [mg/Nl]. With the start of feed of tellurium vapor, the acrylonitrile yield increased and the carbon dioxide yield decreased. After 2 hours, the acrylonitrile yield was 80.0%. Although the feed of tellurium was stopped and the reaction was allowed to proceed for an additional 2 hours, there was no change in the acrylonitrile yield.
When the feed was stopped, a small amount of the catalyst was taken out and analyzed for composition, and the increase in the tellurium content of the packed catalyst was 0.02%. Example 2 The experimental formula is Fe ₁₀ Sb ₂₅ Cu ₃ Mo _0.5 W _0.3 Te _1.5 O _73.4
A fluidized catalyst (SiO ₂ ) ₆₀ was packed in a fluidized bed reactor with an inner diameter of 20 cm, and an ammoxidation reaction of propylene was carried out. The test conditions in this case were as follows. Apparent linear velocity 18 cm/sec Reaction pressure 0.5 Kg/cm ² G Reaction temperature 450°C Supply gas molar ratio Air/propylene = 10.5 (molar ratio) NH ₃ /propylene 1.05 (molar ratio) Reaction was carried out under these conditions for 500 hours. , the yield of acrylonitrile decreased. When this deteriorated catalyst was extracted and an activity test was conducted under the activity test conditions (1), the acrylonitrile yield was 83.0%. Therefore, propanetellol vapor was introduced into the propylene supply gas line and sent to the reactor along with the propylene gas. The concentration of the tellurium component in the total feed gas in terms of tellurium was 0.42 [mg/Nl]. With the start of feeding propanetellol vapor, the acrylonitrile yield increased and the carbon dioxide yield decreased. After 3 hours, the acrylonitrile yield was
It became 84.7%. Although the supply of propanetellol vapor was stopped and the reaction was allowed to proceed for an additional 3 hours, the yield of acrylonitrile did not change. When the supply of propanetellurol vapor was stopped, a small amount of the catalyst was removed and the composition was analyzed, and the increment in the tellurium content of the packed catalyst was found to be
It was 0.07%. Example 3 The empirical formula is Te _0.5 Mo ₁₀ W ₁ Fe ₂ Co ₃ Ni ₂ Bi ₁ O _43.5
A fluidized catalyst (SiO ₂ ) ₅₀ was used for the ammoxidation reaction of methanol according to the activity test conditions (2). The yield of hydrocyanic acid was 84.1%, but the reaction content became strange due to the decrease in the flow rate of ammonia, and although normal reaction conditions were restored, the yield of hydrocyanic acid was 82.9%.
It has dropped to %. Therefore, telluric acid was mixed with the methanol to be supplied. The concentration of telluric acid in the total feed gas is:
It was 0.1 [mg/Nl] in terms of tellurium, and 2.53 [mg/mol] in terms of tellurium for methanol. The hydrocyanic acid yield improved and reached 83.9% after 1 hour. Example 4 Using a fluidized catalyst with an experimental formula of P ₁ Te _0.5 V ₁₂ O _33.5 (SiO ₂ ) ₅₀ , an activity test was conducted under test conditions (3). The benzonitrile yield was 76.4%. During the reaction, the amount of toluene fed was greater than the set value, so the yield decreased to 75.2%. Therefore, tellurium elemental vapor was introduced into the ammonia supply gas line and sent to the reactor along with the ammonia gas. The concentration of feed tellurium was 0.05 [mg/Nl] based on the total feed gas. The benzonitrile yield increased with the start of feed of tellurium vapor, reaching 76.8% after 2 hours. Example 5 Using the same catalyst as in Example 1, an ammoxidation reaction of propylene was carried out under test conditions (1). After 500 hours of reaction, the initial yield of acrylonitrile was 80.3%, but
It decreased to 79.8%. On the contrary, the yield of carbon dioxide gas increased slightly. On the other hand, propanetellurol vapor was introduced into the propylene supply gas line so that the tellurium concentration in the total supply gas was 2 × 10 ^-3 [mg/Nl], and the same reaction was carried out for 500 hours. . In this case, the yield of acrylonitrile remained almost unchanged even after 500 hours, and the yield of acrylonitrile was 80.5% according to the results of analysis immediately before the reaction was stopped. Summary of Results The contents of the above experimental examples are summarized in the following table. 【table】

Claims (1)

[Claims] 1. Using a tellurium-containing metal oxide catalyst,
A method for carrying out an ammoxidation reaction of an organic compound at a temperature between 500°C and 500°C, characterized in that tellurium alone or a tellurium compound is continuously or intermittently fed into the reactor in a vapor phase from outside the reactor. how to. 2 The tellurium-containing metal oxide catalyst has a particle size of 5 to
2. The method of claim 1, wherein the catalyst is a fluidized catalyst in the 200 micron range. 3. Claims 1 to 2, wherein the form of the tellurium component fed in the vapor phase to the reactor is simple tellurium, tellurium hydride, organic tellurium compound, tellurium oxide, or tellurium hydrate. Any method described. 4. The method according to any one of claims 1 to 3, wherein the feed amount of the tellurium component relative to the total amount of reaction supply gas is 10 ^-5 to 10 ² [mg/]. 5. The method according to any one of claims 1 to 4, wherein the tellurium content increase by feeding the tellurium component into the packed catalyst is 0.001 to 15% by weight.