JPH0139418B2 - - 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. Many examples of ammoxidation reactions of organic compounds are known. These are prepared using metal oxide catalysts at temperatures between 300°C and 600°C to produce saturated or unsaturated aliphatic hydrocarbons, alcohols, aldehydes, alkyl-substituted aromatic hydrocarbons, and alkyls containing nitrogen, oxygen, or sulfur as heteroelements. This method produces nitrile compounds from substituted heterocyclic compounds. For example, Special Publication No. 36-5870, Special Publication No. 37-
Publication No. 14075, Special Publication No. 1911-1911, Publication No. 19111, Special Publication No. 37
-13460 Publication, Japanese Patent Publication No. 40-24367, Japanese Patent Application Publication No.
Metal oxide catalysts containing molybdenum-bismuth, etc., as described in Japanese Patent Publication No. 49-58100, Japanese Patent Application Laid-open No. 10200-1980, Japanese Patent Publication No. 33888-1988, Japanese Patent Publication No. 18014-1987, etc. , antimony and tin,
It is known that metal oxide catalysts containing iron, uranium, etc. are useful for ammoxidation of propylene, isobutene, methanol, etc. In addition, Japanese Patent Publication No. 15689/1989 shows that metal oxide catalysts containing vanadium are useful for ammoxidation of alkyl-substituted aromatic hydrocarbons and alkyl-substituted heterocyclic compounds.
It is described in Japanese Patent Application Laid-Open No. 13378/1983. In the ammoxidation reactions 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 and the conditions under which it is used. Most of them are a decrease in the yield of the desired product due to a decrease in the selectivity of the desired product. There are various causes for this, and countermeasures are being considered from various angles. However, in each case, the cause is not necessarily clear, and countermeasures include changing reaction conditions, replacing part or all of the catalyst, or removing the deteriorated catalyst from the reactor and regenerating it. All that has been proposed is a method that is complicated and economically incurs considerable losses. It would be very advantageous if the catalyst performance could be restored by some method while the reaction is being carried out. [] Summary of the Invention The present invention aims to solve the above-mentioned problems regarding these metal oxide catalysts by continuously or intermittently transporting these metal oxide catalysts from outside the reaction system into the reactor in the vapor phase while carrying out the reaction. The objective is to be achieved by introducing tellurium components. That is, the method for improving the activity of a metal oxide catalyst according to the present invention is a method for carrying out an ammoxidation reaction of an organic compound at a temperature of 300°C to 500°C using a metal oxide that does not substantially contain tellurium. This method is characterized in that the tellurium compound is continuously or intermittently charged into the reactor in the vapor phase from outside the reactor. Effects According to the present invention, it is possible to improve the selectivity of a metal oxide catalyst to a desired product, reduce changes over time, or improve the selectivity of a degraded catalyst to a desired product. In particular, the method of the present invention can be carried out safely while carrying out the reaction, so it is industrially extremely easy to implement and economical. Furthermore, surprisingly, the method of the present invention is sufficiently effective even when applied to catalysts that do not contain tellurium, and it is clear that the method has a wide range of applications. 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. Further, the tellurium component may be fed continuously or intermittently, and this selection may be made in light of the reaction results. However, care must be taken because excessive feed of the tellurium component will lead to a decrease in reaction results, especially a decrease in reaction rate. It is not clear why the effect is greater in the case of a fluidized bed than in a fixed bed, but in a fixed bed reaction, the concentration distribution of tellurium deposited on the catalyst occurs in the axial direction of the reactor, whereas In some cases, it may be important that the catalyst is well mixed within the reactor so that the tellurium concentration of the catalyst is averaged out without large deviations. Although the mechanism by which the method of the present invention exerts its effects is not necessarily clear, part or most of the tellurium alone or tellurium compound fed into the reaction zone is deposited on the catalyst, which produces by-products such as carbon dioxide. It may be possible to infer that by poisoning active sites that produce carbon, carbon monoxide, hydrocyanic acid, etc. and suppressing their production, the selectivity of the target product can be relatively increased. The effect of the present invention appears quickly, and the effect is long-lasting. [] Detailed Description of the Invention 1 Metal Oxide Catalyst The metal oxide catalyst used in the present invention is a variety of ammoxidation catalysts for organic compounds or improved catalysts thereof, as shown in the above-mentioned patent publications. The method described above can be equally applied to these known metal oxide catalysts that do not substantially contain tellurium. Specific examples include metal oxides containing at least one element selected from the group consisting of antimony, molybdenum, and vanadium. More preferably, the catalyst used in the present invention is
Selected from the following groups: These catalyst components may be used as they are, or supported on various types of simple substances such as silica, silica-alumina, alumina, silica-titania, and titania. (1) Sb ₁₀ A _a B _b C _c O _x (Atomic composition) A=Fe, Co, Ni, Mn, U, Ce, Sn, Cu B=V, Mo, W C=Mg, Ca, Sr, Ba, La, Ti, Zr, Nb,
Ta, Cr, Re, Ru, Os, Rh, Ir, Pd,
Pt, Ag, Zn, Cd, B, Al, Ga, In, Tl,
Ge, Pb, P, As, Bi, Se a=1~10 b=0~5 c=0~10 (2) Mo ₁₀ D _d E _e F _f O _x (atomic ratio composition) D=Fe, Ni, Co, Mn, Cr, Mg, Ca, Cu,
Zn,, La, Ce, Al, Sn E=Sb, Bi, As, P, B F=K, Rb, Cs d=0~10 e=0.1~10 f=0~3 (3) V ₁₀ G _g H _h O _x (atomic ratio composition) G = Li, Na, K, Rb, Cs, Tl, Mg, Ca,
Sr, Ba H=La, Ce, Ti, Zr, Nb, Ta, Cr, Mo,
W, Mn, Re, Fe, Ru, Os, Co, Rb,
Ir, Ni, Pd, Pt, Cu, Ag, Zn, Cd, B,
Al, Ga, In, Ge, Sn, Pb, P, As,
Sb, Bi, S, Se, g = 0 ~ 5 h = 0 ~ 10 (O represents an oxygen atom, and x represents the number of oxygen atoms corresponding to the oxide formed by combining each component element. ) The catalyst can be of any shape, but in the case of a fixed bed reaction, catalysts of various shapes such as pellets or spheres of several millimeters are used. Further, 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 forms of tellurium include simple tellurium, tellurium monoxide, tellurium dioxide, tellurium trioxide, tellurite acid, telluric acid, hydrogen telluride, or organic tellurium such as telluriums, alkyl tellurides, and tellurides. Examples include compounds. It is convenient for these tellurium element and tellurium compound to be entrained in the raw material supply gas for ammoxidation of an organic compound. 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 type of gas or in a mixture of several types of gas. Tellurium oxides and hydroxides have relatively low vapor pressures, but the 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, tellurium alone, hydrogen telluride, organic tellurium compounds, etc. have high vapor pressures and are therefore easy to use. Various methods can be considered for feeding the tellurium component into the reactor, but a predetermined amount of the tellurium component may be flowed down or sprayed into the above-mentioned supply gas flow path. Alternatively, tellurium alone or a tellurium compound as it is or supported on a suitable support may be placed in the flow path of the entrained gas, and the inflow amount may be set by 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, propentel, 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, it is good to use the raw material organic compound of the target reaction or ammonia,
For this purpose only, small amounts of hydrogen, olefins, alcohols, etc. may be used. 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 too 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 feed rate is to feed the tellurium or tellurium compound little by little, follow the progress of the reaction, and when the desired level is reached, reduce or stop the feed rate, and adjust as needed. The method is to repeat. 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 up to 10
The amount should be approximately [mg/g-catalyst/hour]. It is desirable that the introduced tellurium component uniformly catalyzes 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. Also, depending on the form of the compound, some are easy to deposit on the catalyst and others are not.
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 will deposit on the catalyst, unless the feeding amount is excessive,
The efficiency is good even if the feeding amount is somewhat large. 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 to be fed, the type of reaction, and reaction conditions. However, the approximate range is that the increase due to tellurium deposition on the packed catalyst as the tellurium component is fed is
0.001 to 15% by weight, preferably 0.01 to 10
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 Experimental Examples The effects of the present invention will be shown below using 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) Ammoxidation reaction of propylene 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 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)/propylene = 2.10 (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 of toluene A catalyst is packed in the same fluidized bed 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 An activity test was conducted under test conditions (1) using a fluidized bed catalyst having the empirical formula Fe ₁₀ Sb ₂₅ V _0.1 P _0.5 O _65.4 (SiO ₂ ) ₃₀ . Acrylonitrile yield was 74.2%. The vapor of tellurium alone was introduced into the ammonia supply gas line and sent to the reactor along with the ammonia gas. The concentration of tellurium in the total feed gas is 1.90
[mg/N]. With the start of feed of tellurium, the acrylonitrile yield increased and the carbon dioxide yield decreased. After 2 hours, the acrylonitrile yield was 76.1%. Therefore, the feed of tellurium was stopped and the reaction was continued for an additional 2 hours, but the yield of acrylonitrile remained unchanged. Example 2 Using a fluidized catalyst whose empirical formula is W _0.5 Co ₅ Fe ₁₀ Sb ₂₅ O _71.5 (SiO ₂ ) ₃₀ , an ammoxidation reaction of propylene was carried out under test conditions (1). The yield of acrylonitrile was initially 74.1%, but the activity of the catalyst decreased after 560 hours of reaction use, and the yield became 72.9%. On the other hand, tellurium elemental vapor was introduced into the ammonia supply gas line and sent to the reactor together with the ammonia gas. The tellurium concentration of the total feed gas is 3.1×
It was 10 ^-3 [mg/N]. The reaction was continued for 560 hours, during which time the yield of acrylonitrile did not decrease, but rather improved.
According to the analysis results immediately before the reaction was stopped, the acrylonitrile yield was 75.8%. Example 3 An activity test was conducted under test conditions (1) using a fluidized catalyst whose empirical formula was Sn ₁₀ Sb ₂₅ O ₇₀ (SiO ₂ ) ₃₀ . Acrylonitrile yield was 68.9%. Propylene feed line was fed with propanetellol vapor and entrained in propylene gas and sent to the reactor. The tellurium equivalent concentration in the total feed gas is
It was 0.90 [mg/N]. The yield of acrylonitrile was 72.1%. Example 4 Using a fluidized catalyst having the empirical formula U ₁₀ Sb ₃₀ O _86.7 (SiO ₂ ) ₆₀ , an activity test was conducted under test conditions (1). The acrylonitrile yield was 70.0%, but it decreased to 66.8% due to the long reaction time. Therefore, propanetellol vapor was introduced into the propylene supply gas line and sent to the reactor along with the propylene gas. The acrylonitrile yield gradually increased and reached 68.6% after 1 hour. After the reaction, tellurium analysis of the catalyst revealed that
The tellurium content was 0.08 (wt)%. It is thought that tellurium was deposited on the catalyst due to the feed of the tellurium component. Example 5 The empirical formula is P _0.5 K _0.1 Fe ₃ Ni _2.5 Co _4.5 Bi ₁ Mo ₁₂ O _50.3
Using a (SiO ₂ ) ₄₅ fluidized catalyst, methanol ammoxidation reaction was carried out under test conditions (2). The yield of hydrocyanic acid was 82.8%, but due to long-term use, the yield decreased to 80.1%. Methyl telluride was mixed with methanol and sent to the reactor at a tellurium concentration of 0.70 [mg/N] in the total feed gas. The hydrocyanic acid yield recovered to 82.2%. Example 6 Using a fluidized catalyst having an empirical formula of P ₁ V ₁₂ O _32.5 (SiO ₂ ) ₅₀ , an ammoxidation reaction of toluene was carried out under test conditions (3). The benzonitrile yield was 75.2%. The vapor of tellurium alone was fed into the ammonia supply line, and was sent to the reactor along with the ammonia gas. The tellurium concentration in the total feed gas is 0.30 [mg/N]
] It was. With the start of feed of tellurium, the benzonitrile yield increased and the carbon dioxide yield decreased. After an hour,
The benzonitrile yield was 76.5%. Summary of Results The contents of the above experimental examples are summarized as follows. 【table】

Claims (1)

[Claims] 1. A method for carrying out an ammoxidation reaction of an organic compound at a temperature of 300°C to 500°C using a metal oxide that does not substantially contain tellurium, in which tellurium alone or a tellurium compound is added from outside the reactor, A method characterized in that the vapor phase is continuously or intermittently fed into the reactor. 2. The method according to claim 1, wherein the metal oxide catalyst contains at least one element selected from the group consisting of antimony, molybdenum, and vanadium. 3. A method according to any one of claims 1 to 2, wherein the metal oxide catalyst is a fluidized catalyst with a particle size in the range of 5 to 200 microns. 4. According to any one of claims 1 to 3, the form of tellurium fed to the reactor is simple tellurium, tellurium hydride, organic tellurium compound, tellurium oxide, or tellurium hydroxide. the method of. 5. The method according to any one of claims 1 to 4, wherein the feed amount of tellurium is 10 ^-5 to 10 ² [mg/] relative to the total amount of reaction supply gas. 6. The method according to any one of claims 1 to 5, wherein the tellurium increment in the packed catalyst due to feed of tellurium into the reactor is 0.001 to 15% by weight.