JP4484995B2 - Process for producing unsaturated nitriles - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention uses a fluidized bed reactor to carry out a gas phase catalytic ammoxidation reaction of propane or isobutane using a catalyst containing molybdenum, antimony, vanadium and niobium supported on a support and corresponding unsaturation. The present invention relates to a method for producing a nitrile.
[0002]
[Prior art]
In recent years, many catalysts have been proposed for producing a corresponding unsaturated nitrile by vapor-phase catalytic ammoxidation of propane or isobutane instead of propylene or isobutylene, and in particular, an oxide catalyst containing molybdenum has attracted attention. .
For example, Mo-Te-V-Nb-based oxide catalysts are disclosed in U.S. Pat. No. 5,049,692, U.S. Pat. No. 5,422,328, European Patent No. 529853B1, and JP-A-7-232011. JP-A-7-289907, JP-A-7-315842, JP-A-8-57319, JP-A-8-141401, and the like.
[0003]
Similarly, Mo-Sb-V-based oxide catalysts containing molybdenum are disclosed in Japanese Patent Laid-Open No. 10-330343, and examples thereof include Mo-Sb-V-Nb-based oxide catalysts.
Mo-Te oxide catalysts are disclosed in JP-A-7-215926, Mo-Te-Cr oxide catalysts are disclosed in US Pat. No. 5,171,876, and W-Te-V oxide catalysts are disclosed. Japanese Patent Application Laid-Open No. 6-228073 discloses V-Sb-Te oxide catalysts in US Pat. No. 5,079,207, European Patent No. 337028A1, and the like.
[0004]
It has been recognized that the molybdenum-containing oxide catalyst disclosed in the above publication deteriorates with the progress of the ammoxidation reaction, and the yield of unsaturated nitrile decreases.
U.S. Pat. No. 4,709,070 and JP-A-1-41135 disclose a tellurium compound or tellurium in the presence of an oxide catalyst containing tellurium in an oxidation reaction, ammoxidation reaction or oxidative dehydrogenation reaction of an organic compound. A method for activating a deteriorated catalyst by adding a combination of a compound and a molybdenum compound is disclosed.
However, these publications only describe examples of methanol ammoxidation reaction, propylene ammoxidation reaction, toluene ammoxidation reaction and butene oxidative dehydrogenation reaction, and are supported on silica used in the present invention process. There is no specific description of oxide catalysts containing molybdenum, antimony, vanadium and niobium, and no tellurium at the time of catalyst preparation, and the examples also describe the ammoxidation reaction of propane or isobutane using this catalyst. Not.
[0005]
U.S. Pat.No. 3,882,159, German Patent No. 3,331,521, WO97338863A1, etc. are not effective while adding a molybdenum compound as an activator in the presence of an oxide catalyst containing molybdenum. A method for producing a saturated nitrile is disclosed, but relates to a gas phase catalytic ammoxidation reaction of propylene or isobutylene.
In JP-A-10-137585, JP-A-11-285636, and JP-A-11-285637, propane reacts with a metal oxide catalyst composed of molybdenum, vanadium, antimony and niobium or tantalum, and acrylic acid is synthesized from propane. However, these publications only describe examples of the propane oxidation reaction, and do not describe the propane or isobutane ammoxidation reaction used in the inventive process of the present application.
[0006]
Japanese Patent Laid-Open No. 11-124361 disclosed by the present inventors is a specific technical disclosure capable of solving the yield reduction of the corresponding unsaturated nitrile by vapor phase catalytic ammoxidation of propane or isobutane in the prior art. Among these, a technique has been disclosed in which tellurium is an essential component and a tellurium compound is added to a catalyst system containing the element from the time of catalyst preparation to suppress a decrease in catalyst performance.
However, this technology has not disclosed any technology regarding a catalyst not containing tellurium as an essential component since the catalyst preparation. In addition, although there is a technical disclosure that improves the performance of a deteriorated catalyst by adding a tellurium compound, there is no technical disclosure regarding a technology that improves the initial catalyst performance by addition.
As described above, the yield of the target unsaturated nitrile is insufficient in the prior art, and when producing the corresponding unsaturated nitrile by vapor phase catalytic ammoxidation of propane or isobutane, molybdenum, vanadium, antimony and It contains niobium and does not contain tellurium in the catalyst preparation, and it contains not only tellurium compounds or molybdenum compounds and tellurium compounds, but also contains molybdenum, vanadium, antimony and niobium, and tellurium is included in the catalyst preparation. No specific measures have been proposed to improve the performance of non-catalysts by additive technology.
[0008]
[Problems to be solved by the invention]
In the present invention, a gas phase catalytic ammoxidation reaction is carried out with propane or isobutane in the presence of an oxide catalyst containing molybdenum, vanadium, antimony and niobium and not containing tellurium in the catalyst preparation stage, and stable at a high yield. It is an object of the present invention to provide a process for the production of correspondingly unsaturated nitriles.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors carried out gas phase catalytic ammoxidation of propane or isobutane using an oxide catalyst containing molybdenum, vanadium, antimony and niobium and not containing tellurium at the time of catalyst preparation. result of intensive studies on a method for producing an unsaturated nitrile in high yield and stably for corresponding, by adding tellurium compound, or a motor Ribuden compound and tellurium compound to the reactor during the reaction, specifically the nitrile selectivity The improvement was found and the present invention was made.
[0010]
That is, the present invention is (1) using a fluidized bed reactor in the presence of an oxide catalyst containing molybdenum, vanadium, antimony and niobium supported on a carrier and not containing tellurium in the catalyst preparation stage. in producing the unsaturated nitrile corresponding isobutane perform ammonia and molecular oxygen and the gas phase ammoxidation addition, during the manufacturing, tellurium compounds, or the tellurium compound and a molybdenum compound in fluidized bed reactor A method for producing an unsaturated nitrile characterized by:
[0011]
(2) The method according to (1) above, wherein the oxide catalyst has a component composition represented by the following general formula supported on 10 to 60% by weight of silica;
Mo1VaSbbNbcXdOn
(In the above formula, X represents B, W, P, Sn, Cu, Cr, Re, Hf, Ta, Ti, Zr, Sb, Bi, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Zn. , Al, Ga, In, Tl and at least one element selected from alkaline earth metals, a, b, c, d and n are atoms of V, Sb, Nb, X, O per Mo atom A is 0.01 ≦ a ≦ 1.0, b is 0.01 ≦ b ≦ 1.0, c is 0.01 ≦ c ≦ 1.0, d is 0 ≦ d ≦ 1.0, N is an atomic ratio of oxygen determined by the oxidation number of the constituent metal element.)
[0012]
(3) The method for producing an unsaturated nitrile according to the above (1) or (2), wherein the added amount of the tellurium compound or the tellurium compound and the molybdenum compound is 0.1 or less per weight of the oxide catalyst. .
(4) The method for producing an unsaturated nitrile according to any one of (1) to (3) , wherein the tellurium compound is telluric acid and the molybdenum compound is ammonium heptamolybdate.
[0013]
The present invention will be specifically described below.
The main point of the present invention is to add an additive to the catalyst. The catalyst to which the addition of the additive of the present invention can be applied is an oxide containing molybdenum, antimony, vanadium, and niobium supported on a carrier and not containing tellurium at the time of catalyst preparation. It is an oxide expressed by a composition formula.
Mo1VaSbbNbcXdOn
(In the above formula, X is B, W, P, Sn, Cu, Cr, Re, Hf, Ta, Ti, Zr, Sb, Bi, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Zn. , Al, Ga, In, Tl and at least one element selected from alkaline earth metals, a, b, c, d and n represent atomic ratios per Mo atom, and a is 0.01 ≦ a ≦ 1.0, b is 0.01 ≦ b ≦ 1.0, c is 0.01 ≦ c ≦ 1.0, d is 0 ≦ d ≦ 1.0, preferably a is 0.2 ≦ a ≦ 0.6, b is 0.05 ≦ b ≦ 0.5, c is 0.05 ≦ c ≦ 0.5 and d are 0.005 ≦ d ≦ 0.05, and n is the atomic ratio of oxygen determined by the oxidation number of the constituent metal elements.)
[0014]
Tellurium and molybdenum compounds used as additives in the present invention are telluric acid (H6TeO6), tellurium dioxide (TeO2), tellurium trioxide (TeO3), organic tellurium, ammonium heptamolybdate ((NH3) 6Mo7O24 · 4H2O), molybdenum Acid (H2MoO4), molybdenum dioxide (MoO2), molybdenum trioxide (MoO3), etc. can be selected, and telluric acid and ammonium heptamolybdate are preferred.
[0015]
The production of acrylonitrile or methacrylonitrile by the ammoxidation reaction of propane or isobutane according to the present invention is carried out using a fluidized bed reactor. Although the yield of the nitrile decreases with the progress of the reaction, the yield can be improved by adding the additive of the present invention to the fluidized bed reactor during the reaction. The addition can be carried out by pumping the powdered additive into the reactor together with an air stream such as air or nitrogen through a pipe. A good mixing contact between the catalyst and the additive can be obtained by pumping the additive to the dense layer portion of the fluidized bed reactor. This addition can be performed continuously or intermittently. Thus, since the addition of the additive can be performed without stopping the ammoxidation reaction, there is no loss of nitrile production due to the reaction stop. .
[0016]
Among the additives of the present invention, when a tellurium compound is used for addition, a substantially sufficient catalyst performance improving effect can be obtained. Molybdenum compounds can be used as auxiliary additives.
The additive amount of the tellurium compound or tellurium compound and molybdenum compound of the present invention is 0.1 or less, preferably 0.02 or less, relative to the catalyst 1 by weight.
[0017]
The addition frequency of the tellurium compound or the tellurium compound and the molybdenum compound is 1 to 30 days, preferably 1 to 7 days.
The amount and frequency of the tellurium compound can be determined simply by adding the tellurium compound little by little while tracking the results of the ammonic acid reaction.
During the ammoxidation reaction, the yield of the unsaturated nitrile after the addition of the additive is improved as compared with the case where the additive is not added.
[0018]
The improvement in the yield of the catalyst referred to in the present invention cannot be said to have a direct relationship between the tellurium content in the catalyst and the performance of the ammoxidation reaction. That is, even if the yield is improved by adding the tellurium compound or the tellurium compound and the molybdenum compound to the catalyst, simply adding the equivalent amount of the tellurium compound or the tellurium compound and the molybdenum compound to the catalyst preparation stage can increase the yield. The improvement effect is not seen.
The mechanism of the additive effect expression of the additive of the present invention is not sufficiently clear. During the fluidized bed ammoxidation reaction, the added powdered tellurium compound or powdered molybdenum compound comes into contact with the surface of the catalyst particles in the reactor to physically or chemically interact with the active sites of the composite oxide constituting the catalyst particles. It may be involved in the reaction.
[0019]
The oxide catalyst of the present invention is a supported catalyst supported on a carrier, but is preferably a silica-supported catalyst. The concentration of the alkali compound contained in the carrier is 5000 ppm or less, preferably 1000 ppm. When the oxide catalyst of the present invention is a silica-supported catalyst, it has a high mechanical strength and is suitable for an ammoxidation reaction using a fluidized bed reactor. The content of the silica support is preferably 10 to 60% by weight, more preferably 20 to 55% in terms of SiO2, based on the total weight of the silica-supported oxide catalyst composed of the oxide of the catalyst constituent element and the silica support. % By weight.
[0020]
Although the raw material of the component metal for manufacturing the oxide catalyst of this invention is not specifically limited, For example, the following compound can be used.
As the raw materials for Mo and V, ammonium heptamolybdate [(NH4) 6Mo7O24 · 4H2O] and ammonium metavanadate [NH4VO3] can be preferably used, respectively.
Niobium is preferably used as an organic acid salt of niobium, and dicarboxylic acid, preferably oxalic acid is used as the organic acid.
[0021]
As raw materials for Nb, niobic acid, niobium inorganic acid salt and niobium organic acid salt can be used. Niobic acid is particularly good.
Niobic acid is represented by Nb2O5.nH2O and is also referred to as niobium hydroxide or niobium oxide hydrate. Further, it is preferably used as an Nb raw material liquid having an organic acid / niobium molar ratio of 2 to 4.
Examples of the raw material for Sb include Sb2O3, Sb2O5, and metal antimony, but it is preferable to use diantimony trioxide [Sb2O3].
[0022]
The manufacturing method of the oxide catalyst of the present invention can be prepared by a general method. For example, (1) a step of preparing a raw material mixture, (2) a step of drying the raw material mixture obtained in step (1) to obtain a catalyst precursor, and (3) a catalyst precursor obtained in step (2). It can be manufactured through three steps of baking the body.
The catalyst adjustment stage of the present invention refers to the above steps (1) to (3), and does not include the stage after the ammoxidation reaction is started in the fluidized bed reactor.
[0023]
Below, the preferable preparation example of the oxide catalyst of this invention which consists of process (1)-(3) is demonstrated. In the present invention, the term “not containing tellurium” in the catalyst preparation stage means a catalyst containing no tellurium in the raw material preparation step in this preparation example.
[0024]
(Process 1: Raw material preparation process)
A slurry in which ammonium heptamolybdate, ammonium metavanadate and diantimony trioxide powder are dispersed is heated under reflux conditions to prepare a mixed solution (A).
Niobic acid and oxalic acid are heated and stirred in water to prepare a mixed solution (B).
Oxide catalyst component X (B, W, P, Sn, Cu, Cr, Re, Hf, Ta, Ti, Zr, Sb, Bi, Mn, Fe, Ru, Co, Rh, Ni, Pd as required , Pt, Zn, Al, Ga, In, Tl, and alkaline earth metal) (C) is prepared.
According to the target composition, the mixed solution (A), the mixed solution (B), and the mixed solution (C) are suitably mixed to obtain a raw material preparation solution.
[0025]
When the catalyst for ammoxidation of the present invention is a silica-supported catalyst, the raw material preparation liquid is prepared so as to contain silica sol. Silica sol can be added as appropriate.
Furthermore, it is preferable to add hydrogen peroxide to the liquid mixture (A) or a liquid containing the components of the liquid mixture (A) being prepared. At this time, H2O2 / Sb (molar ratio) is preferably 0.1 to 2, and more preferably 1 to 1.5. At this time, it is preferable to continue stirring at 30 ° C. to 70 ° C. for 30 minutes to 2 hours.
The raw material mixture obtained in this way may be a uniform solution, but is usually a slurry.
[0026]
(Process 2: Drying process)
The raw material preparation liquid obtained in the raw material preparation step is dried by a spray drying method to obtain a dry powder. The atomization in the spray drying method can employ a centrifugal method, a two-fluid nozzle method, or a high-pressure nozzle method. As the drying heat source, air heated by steam, an electric heater or the like can be used. The dryer inlet temperature of hot air is preferably 150 to 300 ° C.
[0027]
(Process 3: Firing process)
An oxide catalyst is obtained by firing the dry powder obtained in the drying step. Firing is performed in an inert gas atmosphere substantially free of oxygen, such as nitrogen gas, argon gas, and helium gas, preferably at 500 to 800 ° C., preferably 550 to 700 ° C. while circulating the inert gas. . The firing time is 0.5 to 20 hours, preferably 1 to 8 hours.
[0028]
Firing can be performed using a rotary furnace, tunnel furnace, tubular furnace, fluidized firing furnace, or the like. Firing can be repeated.
Prior to the firing step, it is also preferable to pre-fire the dry powder at 200 to 400 ° C. for 1 to 5 hours in an air atmosphere or air circulation.
Acrylonitrile or methacrylonitrile is produced by subjecting propane or isobutane to a gas phase catalytic ammoxidation reaction with ammonia and oxygen in the presence of the oxide catalyst thus produced.
[0029]
The feedstock for propane or isobutane and ammonia does not necessarily have to be high purity, and industrial grade gases can be used.
Air, oxygen-enriched air, or pure oxygen can be used as the supply oxygen source. Further, helium, argon, carbon dioxide gas, water vapor, nitrogen or the like may be supplied as a dilution gas.
The molar ratio of ammonia to propane or isobutane supplied to the reaction is 0.3 to 1.5, preferably 0.8 to 1.0.
[0030]
The molar ratio of oxygen supplied to the reaction to propane or isobutane is 0.1 to 6, preferably 0.5 to 4.
The reaction temperature is 350 ° C to 500 ° C, preferably 380 ° C to 470 ° C.
The reaction pressure is 1 * 10 ^{4 to} 5 * 10 ⁵ Pa, preferably 5 * 10 ^{4 to} 3 * 10 ⁵ Pa.
[0031]
The contact time is 0.1 to 10 (sec · g / cc), preferably 0.5 to 5 (sec · g / cc). In the present invention, the contact time is determined by the following equation.
Contact time (sec · g / cc) = (W / F) × 273 / (273 + T) × (P + 1.013 * 105) / P
Where W = filled catalyst amount (g)
F = Raw material mixed gas flow rate (Ncc / sec) at standard condition (0 ° C., 1.013 * 10 ⁵ Pa)
T = reaction temperature (° C.)
P = reaction pressure (Pa)
It is.
[0032]
As the reaction method, a conventional method such as a fluidized bed or a moving bed can be adopted, but a fluidized bed reactor in which reaction heat can be easily removed is preferable.
The reaction of the present invention may be a single flow type or a recycle type.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
The oxide catalyst of the present invention will be described below with reference to examples of preparation of the catalyst and examples of production of acrylonitrile by the gas-phase catalytic ammoxidation reaction of propane. It is not limited.
Propane conversion (%) = (moles of propane reacted) / (moles of propane fed) × 100
Acrylonitrile selectivity (%) = (number of moles of acrylonitrile produced) / (number of moles of reacted propane) × 100
[0034]
[Example 1]
(Preparation of catalyst)
An oxide catalyst having a composition formula of Mo1V0.33Sb0.22Nb0.07 / 50 wt% -SiO2 was prepared as follows.
41.87 g of ammonium heptamolybdate [(NH4) 6Mo7O24 · 4H2O], 90.55 g of ammonium metavanadate [NH4VO3], and 74.47 g of diantimony trioxide [Sb2O3] were added to 2200 g of water for 3 hours 30 hours. After heating to reflux for minutes, the mixture was cooled to about 70 ° C. to obtain liquid mixture A-1.
[0035]
After adding 38.53 g of niobic acid containing 76.6% by weight as Nb2O5 and 69.98 g of oxalic acid dihydrate [H2C2O4 · 2H2O] to 275 g of water, the mixture was heated to about 60 ° C. with stirring and dissolved. The liquid mixture B-1 cooled to about 30 degreeC was obtained.
To the obtained mixed liquid A-1, 1666.7 g of silica sol containing 30 wt% as SiO 2 was added. The liquid temperature dropped to about 50 ° C. Further, 115.8 g of hydrogen peroxide containing 15 wt% as H 2 O 2 was added and stirring was continued at 50 ° C. for 1 hour. Meanwhile, the color of the liquid changed from dark blue to reddish brown. Next, the mixed solution B-1 was added to obtain a raw material preparation solution.
[0036]
The obtained raw material mixture was supplied to a centrifugal spray dryer and dried to obtain a microspherical dry powder. The dryer inlet temperature was 210 ° C and the outlet temperature was 120 ° C.
100 g of the obtained dry powder was filled in a glass tube having a diameter of 1 inch and calcined at 640 ° C. for 2 hours under a nitrogen gas flow of 600 Ncc / min to obtain a catalyst.
[0037]
(Propane ammoxidation reaction)
45 g of the catalyst obtained in a Vycor glass fluidized bed reaction tube having an inner diameter of 25 mm was charged, and propane: ammonia: oxygen: helium = 1: 0 under a reaction temperature of 440 ° C. and a reaction pressure of 1.507 * 10 ⁵ Pa. A mixed gas having a molar ratio of .85: 1.8: 5.0 was passed at a contact time of 3.0 (sec · g / cc), and the change in performance with time was followed.
[0038]
(Change with time and effect of addition)
The reaction results 24 hours after the start of the reaction were a conversion of 50.0% and a selectivity of 54.7%. 48 hours after the start of the reaction, 0.5 g of powdered telluric acid [H6TeO6] as an additive was injected into the reactor through a pipe together with a nitrogen stream during the reaction.
[0039]
The reaction results started to recover immediately after the addition, and after 5 hours, the conversion was 50.0% and the selectivity was 56.6%. As for the reaction results after 100 hours, the conversion was 49.7% and the selectivity was 56.3%. Table 1 shows the reaction results 24 hours, 53 hours and 100 hours after the start of the reaction.
Thereafter, the reaction was continued, and 0.1 g of telluric acid was similarly added every 200 hours, 300 hours, 400 hours, and 500 hours from the start of the reaction. As for the reaction results after 510 hours, the conversion rate was 50.0% and the selectivity rate was 56.4%, so that high selectivity could be maintained.
The obtained results are shown in Table 1.
[0040]
[Example 2]
(Preparation of catalyst)
An oxide catalyst having a composition formula of Mo1V0.3Sb0.20Nb0.07 / 50 wt% -SiO2 was prepared in the same manner as in Example 1.
(Propane ammoxidation reaction)
Using the obtained catalyst, an ammoxidation reaction was carried out in the same manner as in Example 1.
(Change with time and effect of addition)
48 hours after the start of the reaction, 0.1 g of powdered telluric acid [H6TeO6] and 0.1 g of ammonium heptamolybdate [(NH4) 6Mo7O24 · 4H2O] were injected into the reactor through a pipe together with a nitrogen stream. did. Table 1 shows the reaction results 24 hours after the start of the reaction and 53 hours after the start of the reaction.
[0041]
[Comparative Example 1]
(Preparation of catalyst)
An oxide catalyst having a charged composition formula of Mo1V0.33Sb0.22Nb0.07 / 50 wt% -SiO2 was prepared in the same manner as in Example 1.
(Propane ammoxidation reaction)
Using the obtained catalyst, an ammoxidation reaction was carried out in the same manner as in Example 1.
(Change with time and effect of addition)
The reaction was evaluated immediately after the reaction, 24 hours after the start of the reaction, and 53 hours after the start without adding the telluric acid. The obtained results are shown in Table 1.
[0042]
【The invention's effect】
In the present invention, a gas phase catalytic ammoxidation reaction is carried out with propane or isobutane in the presence of an oxide catalyst containing molybdenum, vanadium, antimony and niobium and not containing tellurium at the time of preparation of the catalyst. It aims at providing the method of manufacturing the unsaturated nitrile corresponding to this.

Claims (4)

Using a fluidized bed reactor, propane or isobutane is converted to ammonia and molecular oxygen in the presence of an oxide catalyst containing molybdenum, vanadium, antimony and niobium supported on the support and not containing tellurium in the catalyst preparation stage. and in producing the corresponding unsaturated nitrile performing vapor-phase catalytic ammoxidation reaction, during the manufacture, tellurium compounds, it was or is characterized by adding a tellurium compound and a molybdenum compound in the fluidized bed reactor not Method for producing saturated nitrile. The method according to claim 1, wherein the oxide catalyst has a component composition represented by the following general formula supported on 10 to 60% by weight of silica;
Mo1VaSbbNbcXdOn
(In the above formula, X represents B, W, P, Sn, Cu, Cr, Re, Hf, Ta, Ti, Zr, Sb, Bi, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Zn. , Al, Ga, In, Tl and at least one element selected from alkaline earth metals, a, b, c, d and n are atoms of V, Sb, Nb, X, O per Mo atom A is 0.01 ≦ a ≦ 1.0, b is 0.01 ≦ b ≦ 1.0, c is 0.01 ≦ c ≦ 1.0, d is 0 ≦ d ≦ 1.0, N is an atomic ratio of oxygen determined by the oxidation number of the constituent metal element.) The method for producing an unsaturated nitrile according to claim 1 or 2, wherein the addition amount of the tellurium compound or the tellurium compound and the molybdenum compound is 0.1 or less per weight of the oxide catalyst. The method for producing an unsaturated nitrile according to any one of claims 1 to 3 , wherein the tellurium compound is telluric acid and the molybdenum compound is ammonium heptamolybdate.