Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
  • C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
  • C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/24—Chromium, molybdenum or tungsten
  • B01J23/28—Molybdenum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0027—Powdering
  • B01J37/0045—Drying a slurry, e.g. spray drying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
  • B01J37/036—Precipitation; Co-precipitation to form a gel or a cogel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/50—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C57/00—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms
  • C07C57/02—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms with only carbon-to-carbon double bonds as unsaturation
  • C07C57/03—Monocarboxylic acids
  • C07C57/04—Acrylic acid; Methacrylic acid
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/64—Pore diameter
  • B01J35/647—2-50 nm

Definitions

• the present invention relates to the production of acrylic acid from propane in the presence or absence of molecular oxygen. It is known from European patent application No. EP-A-608838 to prepare an unsaturated carboxylic acid from an alkane according to a catalytic oxidation reaction in the vapor phase in the presence of a catalyst containing a metal oxide mixed comprising essential components, Mo, V, Te, O, as well as at least one element chosen from the group consisting of niobium, tantalum, tungsten, titanium, aluminum, zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony, bismuth, boron, indium and cerium, these elements being present in very precise proportions.
• EP-A-895809 describes catalysts based on oxides comprising molybdenum, vanadium, niobium, oxygen, tellurium and / or antimony, as well as '' at least one other element such as iron or aluminum. These catalysts can be used for the conversion of propane to acrylic acid, in the presence of molecular oxygen, as illustrated in Examples 9 and 10.
• Example 9 describes the oxidation of propane using a catalyst of formula Mo 1 No !
• the object of the invention is to propose a process for the production of acrylic acid from propane, in the presence or absence of molecular oxygen, which makes it possible to obtain a high propane conversion while retaining good selectivity for acrylic acid. .
• this object can be achieved by passing a gaseous mixture comprising propane, steam, and possibly an inert gas and / or molecular oxygen, over a particular catalyst.
• a gaseous mixture comprising propane, steam, and possibly an inert gas and / or molecular oxygen
• oxidation takes place under conditions such that the oxygen of the gas mixture is in sub-stoichiometric proportion relative to the propane introduced, which probably allows the catalyst to act as a redox system and to supply the missing oxygen so that the reaction is performed satisfactorily.
• the present invention therefore relates to a process for the manufacture of acrylic acid from propane, in which a gaseous mixture comprising propane, steam, optionally an inert gas and / or molecular oxygen, on a catalyst of formula (I):
• - x is the quantity of oxygen linked to the other elements and depends on their oxidation states, to oxidize propane to acrylic acid, and when operating in the presence of molecular oxygen, the propane / molecular oxygen molar ratio in the starting gas mixture is greater than 0.5.
• Such a process makes it possible to simultaneously obtain a selectivity for acrylic acid of almost 60% and a high propane conversion.
• it can be easily implemented in a fluidized bed or in a transported bed and the injection of the reagents can be carried out at different points of the reactor, so that one is outside the flammability zone while having a high propane concentration and, consequently, a high catalyst productivity.
• the method according to the invention comprises the following steps: 1 / In the absence of molecular oxygen
• the starting gas mixture is introduced into a first reactor with a transported catalyst bed, b) at the outlet of the first reactor, the gases are separated from the catalyst; c) the catalyst is sent to a regenerator; d) optionally the gases are introduced into a second reactor with a transported catalyst bed; e) where appropriate, at the outlet of the second reactor, the gases are separated from the catalyst and the acrylic acid contained in the separated gases is recovered; f) if necessary, the catalyst is returned to the regenerator; and g) reintroduced regenerated catalyst from the regenerator into the first reactor and, where appropriate, into the second reactor.
• the reactor or reactors are further provided with a cocatalyst.
• the process comprises repeating, in a reactor provided with the catalyst of formula (I) and, where appropriate, a co-catalyst, the cycle comprising the following successive steps: 1) a step of injecting the gas mixture as defined above; 2) a step of injecting steam and, if necessary, inert gas;
• the cycle comprises an additional stage which precedes or follows stage 1) and during which a gaseous mixture corresponding to that of stage 1 is injected but without molecular oxygen, the propane / molecular oxygen molar ratio then being calculated globally for step 1) and this additional step.
• the additional step precedes step 1) in the cycle.
• the propane / water volume ratio in the starting gas mixture is not critical and can vary within wide limits.
• inert gas which can be helium, krypton, a mixture of these two gases, or nitrogen, carbon dioxide, etc., is also not critical and may also vary within wide limits.
• reactions (A) and (B) are carried out at a temperature of 200 to 500 ° C, preferably from 250 to 450 ° C, more preferably still, from 350 to
• the pressure in the reactor (s) is generally from 1.01.10 4 to 1.01.10 6
• the residence time in the reactor, or if there are several, in each reactor, is generally from 0.01 to 90 seconds, preferably from 0.1 to 30 seconds.
• the catalyst corresponds to the following formula (I):
• - b is between 0.006 and 1, limits included; c is between 0.006 and 1, limits included; d is between 0 and 3.5, limits included; and
• - x is the quantity of oxygen linked to the other elements and depends on their oxidation states.
• a is between 0.09 and 0.8, limits included
• - b is between 0.04 and 0.6, limits included; c is between 0.01 and 0.4, limits included; and - d is between 0.4 and 1.6, limits included.
• the oxides of the different metals used in the composition of the catalyst of formula (I) can be used as raw materials in the preparation of this catalyst, but the raw materials are not limited to oxides; among the raw materials which can be used, there may be mentioned, without limitation: - in the case of molybdenum, ammonium molybdate, ammonium paramolybdate, ammonium hepta-molybdate, molybdic acid, molybdenum halides or oxyhalides such as MOCI 5 , organometallic compounds of molybdenum such as molybdenum alkoxides such as Mo (OC H 5 ) 5, acetylacetone molybdenyl; - in the case of vanadium, ammonium metavanadate, halides or oxyhalides of vanadium such as VCl, VC1 5 or VOCl 3 , organometallic vanadium compounds such as vanadium alkoxides such as NO (OC 2 H 5 ) 3 ;
• antimony for example antimony oxide (antimony trioxide), in particular the Senarmontite variety, antimony sulfate (Sb 2 (SO) 3 ) or an antimony chloride (trichloride antimony, antimony pentachloride);
• antimony oxide antimony trioxide
• Sb 2 (SO) 3 antimony sulfate
• antimony chloride trichloride antimony, antimony pentachloride
• Bu) 5 the compounds capable of forming an oxide by calcination, namely, the metal salts of organic acids, the metal salts of mineral acids, complex metal compounds, etc.
• the source of silicon generally consists of colloidal silica and / or polysilicic acid.
• the catalyst of formula (I) can be prepared by mixing, with stirring, aqueous solutions of niobic acid, oxalic acid, ammonium heptamolybdate, ammonium metavanadate, antimony oxide, adding if necessary colloidal silica, then preferably by pre-calcining in air at a temperature between 280 and 340 ° C, preferably at about 300-320 ° C, and calcining under nitrogen at about 600 ° C.
• a is between 0.09 and 0.8, limits included;
• - b is between 0.04 and 0.6, limits included;
• - c is between 0.01 and 0.4, limits included; and - d is between 0.4 and 1.6, limits included.
• the process for preparing the catalyst of formula (I) is implemented by preparing a solution of niobic acid, oxalic acid, preparing a solution of molybdenum, vanadium, antimony and optionally silica, mixing the 2 solutions giving rise to the formation of a gel, drying the gel obtained giving rise to the formation of a precursor of formula (F) below, precalcination then calcination.
• the catalyst can be prepared by implementing the following steps: 4/024665
• step 10 10) calcination of the precalcined gel to obtain the catalyst.
• steps 1), 2) and 3 these steps are merged by introducing the sources of vanadium, antimony and molybdenum in cold water and stirring to obtain a solution .
• step 5 hydrogen peroxide is added until a clear orange-colored solution is obtained.
• the drying (for example of step 9)) can be carried out in a thin layer oven, by atomization, by lyophilization, by zeodratation, by microwave, etc .;
• the precalcination can be carried out under air flow at 280-300 ° C or under static air at 320 ° C, in a fluidized bed, in an oven rotating in a fixed so-called aerated bed, so that the catalyst grains are separated each other to prevent them from fusing during precalcination or possibly during calcination;
• the calcination is preferably carried out under very pure nitrogen and at a temperature in the region of 600 ° C., for example in a rotary kiln or in a fluidized bed and for a period which may be 2 hours.
• the catalyst obtained at the end of the calcination can be ground to give smaller particles. If the grinding is carried out until a powder consisting of particles of the size of a micron is obtained, the powder can subsequently be reshaped using a binder such as for example silica in the form of polysilicic acid, the suspension then being dried again, for example by atomization.
• the precalcination is carried out: either at a temperature below 300 ° C under an air flow of at least 10 ml / min g of catalyst; - Either at a temperature ranging from 300 to 350 ° C under an air flow of less than 10 ml / min / g of catalyst.
• the precalcination is carried out: at approximately 320 ° C. under an air flow rate of less than 10 ml / min / g; or - at around 290 ° C, under an air flow of around 50 ml / min / g.
• SOLLOE reduced it + O 2 - »SOLID oxidized (C) by heating in the presence of oxygen or an oxygen-containing gas at a temperature of 250 to 500 ° C, for the time necessary for the reoxidation of the catalyst .
• they are 1 / 1-5 / 0-5.
• dry air (21% O 2 ) can be used.
• humid air can then be used.
• the regeneration temperature is generally 250 to 500 ° C.
• the process is generally carried out until the reduction rate of the catalyst is between 0.1 and 10 g of oxygen per kg of catalyst.
• This reduction rate can be monitored during the reaction by the quantity of products obtained. The equivalent amount of oxygen is then calculated. It can also be followed by the exothermicity of the reaction. We can also follow the reduction rate by the amount of oxygen consumed in the regenerator. After regeneration, which can be carried out under conditions of temperature and pressure identical to, or different from those of reactions (A) and (B), the catalyst regains initial activity and can be reintroduced into the reactors.
• Reactions (A) and (B) and regeneration (C) can be carried out in a conventional reactor, such as a fixed bed reactor, a fluidized bed reactor or a transported bed reactor.
• Reactions (A) and (B) and regeneration (C) can also be carried out in the same reactor by alternating the reaction and regeneration periods.
• the reactions (A) and (B) and the regeneration (C) are carried out in a reactor with a transported catalyst bed, in particular in a vertical reactor, the catalyst then preferably moving from the bottom to the top.
• the propylene produced and / or the unreacted propane are recycled (or returned) at the inlet of the reactor, that is to say that they are reintroduced at the inlet of the reactor, in mixture or in parallel with the starting mixture of propane, water vapor and, where appropriate, inert gas (ies).
• inert gas ies
• the method according to the invention is implemented in an apparatus such as that shown in the appended figure.
• the starting gas mixture comprising propane, molecular oxygen, water vapor, as well as, if necessary, an inert gas, is introduced into a first reactor (Riser 1) containing the transportable catalyst bed.
• the catalyst is sent to a regenerator.
• the gases are introduced into a second reactor (Riser 2) also containing a transportable catalyst bed.
• the effluents are separated into gases and the catalyst transported.
• the catalyst is sent to a regenerator.
• the gases are treated in a known manner, generally by absorption and purification, with a view to recovering the acrylic acid produced.
• the regenerated catalyst is reintroduced into the first reactor as well as into the second reactor.
• the single regenerator can be replaced by two or more regenerators.
• the first and second reactors are vertical and the catalyst is transported upward by the flow of gases.
• a mode of operation with a single gas passage or with recycling of the products leaving the second reactor can be used.
• the propylene produced and / or the unreacted propane are recycled (or returned) at the inlet of the first reactor, this is that is to say, they are reintroduced at the inlet of the first reactor, as a mixture or in parallel with the starting mixture of propane, oxygen, water vapor and, where appropriate, inert gas (ies).
• the gas mixture also passes over a cocatalyst.
• the propionic acid / acrylic acid ratio is greatly reduced at the outlet of the reactor.
• the formation of acetone which is also a by-product of the manufacture of acrylic acid from propane, is reduced.
• the reactor or, if there are several, at least one of the reactors, comprises a cocatalyst having the following formula (II):
• - d is between 0 and 3.5, limits included
• - f is between 0 and 1, limits included;
• - g ' is between 0 and 1, limits included;
• Such a co-catalyst can be prepared in the same way as the catalyst of formula (I).
• the oxides of the various metals used in the composition of the cocatalyst of formula (II) can be used as raw materials in the preparation of this cocatalyst, but the raw materials are not limited to oxides; as other raw materials, mention may be made in the case of nickel, cobalt, bismuth, iron or potassium, the corresponding nitrates.
• the co-catalyst is present in the form of a transportable bed and preferably, it is regenerated and if necessary circulates in the same way as the catalyst.
• - f is between 0 and 0.4, limits included;
• - g ' is between 0 and 0.4, limits included;
• the mass ratio of the catalyst to the co-catalyst is generally greater than 0.5 and preferably at least 1.
• the cocatalyst is present in the two reactors.
• the catalyst and the cocatalyst are in the form of solid catalytic compositions.
• They can each be in the form of grains generally from 20 to 300 ⁇ m in diameter, the grains of catalyst and of cocatalyst being generally mixed before the implementation of the method according to the invention.
• the catalyst and the cocatalyst can also be in the form of a solid catalytic composition composed of grains, each of which comprises both the catalyst and the cocatalyst.
• x is the quantity of oxygen bound to the other elements and depends on their oxidation states.
• the conversion ratio is the mass of catalyst (in kg) necessary to convert 1 kg of propane.
• a catalyst was prepared in the following manner. In 30 ml of water heated to 80 ° C., 5.35 g of ammonium paramolybdate and 1.33 g of antimony sulphate (Sb 2 (SO) 3 ) are added successively, with stirring. Stirring is continued for 15 minutes. Separately, a solution containing 10 mmol of vanadium is prepared by dissolving 2.63 g of hydrated vanadyl sulphate in 10 ml of distilled water heated to 80 ° C. The second solution is added to the first and the mixture is stirred for 15 minutes before being introduced into a 70 ml autoclave coated with Teflon®.
• Sb 2 (SO) 3 antimony sulphate
• Example 2 (comparative) A catalyst was prepared as follows.
• the mixture is stirred for 10 minutes before being introduced into a 70 ml autoclave coated with Teflon®. Nitrogen is then bubbled for 5 minutes so that it replaces the air present in the autoclave, before closing the latter.
• the autoclave is then placed at 175 ° C for 48 hours.
• a catalyst was prepared in the following manner. In 20 ml of water heated to 80 ° C., 5.35 g of ammonium paramolybdate and 0.55 g of a 31% o hydrogen peroxide solution are added successively, with stirring. , 74 g of antimony trioxide. Stirring is continued for 60 minutes until the antimony oxide dissolves. Separately, a solution containing 9 mmol of vanadium is prepared by dissolving 2.37 g of hydrated vanadyl sulphate in 10 ml of distilled water heated to 80 ° C.
• a third solution containing 3 mmol of niobium is prepared simultaneously by dissolving, with stirring, 1.94 g of hydrated niobium oxalate in 10 ml of distilled water heated to 80 ° C. The second solution is added to the first and stirring is continued for 5 minutes. Finally, the solution containing niobium is added. The mixture is stirred for 10 minutes before introducing it into a 70 ml autoclave coated with Teflon®. Nitrogen is then bubbled for 5 minutes so that it replaces the air present in the autoclave, before closing the latter. The autoclave is then placed at 175 ° C for 48 hours.
• Example 4 A catalyst was prepared as follows.
• a third solution containing 1.5 mmol of niobium is prepared simultaneously by dissolving, with stirring, 0.97 g of hydrated niobium oxalate in 10 ml of distilled water heated to 80 ° C. The second solution is added to the first and stirring is continued for 5 minutes. Finally, the solution containing niobium is added. The mixture is stirred for 10 minutes before introducing it into a 70 ml autoclave coated with Teflon®. Nitrogen is then bubbled for 5 minutes so that it replaces the air present in the autoclave, before closing the latter. The autoclave is then placed at 175 ° C for 48 hours. After this time, the autoclave is cooled by water under the tap for 10 minutes.
• a catalyst was prepared in the following manner. In 45 ml of water, 2,0008 g of ammonium metavanadate are dissolved hot (90 ° C). Then, 1.2149 g of antimony trioxide (senarmontite phase) and 10.0142 g of ammonium heptamolybdate are added. The whole is refluxed under argon, the temperature is fixed at 70 ° C. and the solution is left under stirring for 14 hours. The resulting mixture is opaque blue-black. 2 ml of 30% hydrogen peroxide are added using a syringe, and the solution is allowed to stir. The color gradually evolves towards orange through green-khaki hues. There is then a slight precipitate in a dark orange solution.
• Example 6 Catalyst 6 is prepared like catalyst 5, except that 0.75 g of niobic acid is dissolved in the oxalic acid solution, by heating it at 70 ° C. for 2 hours. This solution is centrifuged before being mixed with the solution containing the other elements. The results are collated in Table 4.
• Example 7 A catalyst was prepared as follows.
• the autoclave is cooled by water under the tap for 10 minutes.
• the black-blue solid obtained in the autoclave is separated from the solution by filtration, washed thoroughly with distilled water and dried for 12 hours at 80 ° C.
• the precursor thus obtained is then calcined under a stream of nitrogen (25 mFh / g) at 500 ° C for 2 hours.
• Catalyst 7 is thus obtained. This catalyst is tested under the same conditions as the other catalysts.
• test effluents are collected for 4 hours in an ice trap. 2 analyzes by chromatography coupled to a mass spectrometer are carried out per sample.
• the propionic acid / acrylic acid molar ratios are thus calculated for each sample, for reaction temperatures of 320 ° C. and 360 ° C.
• the average of the two analyzes carried out per sample is reported in Table 5 below.
• the molar ratio decreases with an increase in temperature and the presence of niobium in the composition of the catalyst.
• This synthesis makes it possible to prepare approximately 100 g of dry precursor.
• a solution D is prepared simultaneously with the solution A.
• the mixture is heated to 60 ° C with stirring for 2 hours, then brought back to 30 ° C.
• the solution is then centrifuged at 6200 rpm for 12 minutes to obtain a clear solution.
• the gel is then dried in a ventilated oven, on trays covered with Teflon®, overnight, at 130 ° C. 86.3 g of dry precursor are recovered.
• the precursor is in the form of leaves, black above and a thin green film below. A precursor is thus obtained.
• Example 10 Preparation of a catalyst C of formula: Mo 1 V 0 0 Sbo. 15 Nbo .10 Sio . g 3 O x and its precursor. Synthesis of the precursor
• a 10 liter jacketed reactor is used.
• the diagram of the installation is given in FIG. 2.
• the installation comprises the jacketed reactor 1, provided with a withdrawal orifice 2 and an oil bath 3 thermostatically controlled at 140 ° C (so as to the temperature inside the reactor is around 99 ° C), an agitator 4 designed to operate at 125 rpm, an inlet 5 for the reagents, an inlet 6 for the nitrogen, from a refrigerant 7 connected to a vent 8.
• Cold, with stirring and under a flow of nitrogen 2600 g of water, 123 g of ammonium metavanadate (1.052 mole), 77 g of oxide are introduced.
• a laboratory atomizer (ATSELAB® from the company Sodeva) is used. The atomization takes place in an air atmosphere. The operating parameters are globally:
• the increase in the dry matter content in the slip is carried out on a rotary evaporator up to 30.8% by weight.
• a fraction of between 40 and 160 ⁇ m is recovered in the chamber which corresponds to the precursor.
• laboratory simulations were carried out in a laboratory fixed bed reactor, generating propane pulses and oxygen pulses.
• the reactor is heated to 250 ° C and the vaporizer to 200 ° C.
• the electric priming of the water pump is activated.
• the water pump is activated and the temperature of the reactor is raised to 400 ° C and waiting 30 minutes for the hot spot to stabilize.
• the catalyst is considered to be completely oxidized when the temperature of the hot spot has stabilized, that is to say when there is no longer any exotherm due to the reaction (by following the temperature of the catalyst measured by means of 'a thermocouple placed in the catalytic bed, we can see the temperature fluctuations as a function of the pulses).
• Each small washing bottle (25 ml of capacity and filled with 20 ml of water) is equipped with a gas pocket, and when the bottle is connected to the outlet of the reactor (as soon as the liquid bubbles) , the pocket is opened and the stopwatch is started.
• Liquid effluents are analyzed on an HP 6890 chromatograph, after performing a specific calibration.
• a redox cycle represents:
• TA2 test It is also a propane oxidation test carried out in the absence of molecular oxygen.
• the duration of the propane pulse (as well as that of the oxygen) is modified during the assessment, thus making it possible to observe the behavior of the catalyst in the face of a more or less rich redox mixture.
• the duration of the oxygen pulse is always twice as long as that of propane, and with a double flow, to keep the catalyst oxidized.
• the balance sheet is in this example of 60 cycles divided into six micro-balance sheets in the following manner: 2 first micro-balance sheets of 7 and 8 cycles:
• the duration of oxygen injection in the propane pulse is varied by keeping the propane and oxygen pressures constant.
• the balance of 40 cycles is broken down as follows:
• Catalyst B is tested under the same conditions and in the same manner as for the TAl test. ii) TB3 test
• Catalyst B is tested under the same conditions and in the same manner as for the TA3 test (presence of molecular oxygen). iii) TB4 to TB6 tests
• the catalyst B is tested under the same conditions and in the same manner as for the TA2 test, at 420 ° C.
• the duration of oxygen injection in the propane pulse is varied by maintaining constant propane and oxygen pressures.
• Oxygen is injected at the end of the propane pulse to see if there is an influence on the catalytic performance compared to an injection at the start of the pulse.
• the balance of 40 cycles is broken down as follows: 10 cycles of 30 s of propane + 20 s of O 2 (oxygen being injected at the end of the propane pulse), with Propane / O 2 / He proportions -Kr / HO of 30/30/45/45, with a flux of helium-krypton of 4.27 Nl / h.
• We then have an intermediate pulse composed only of the carrier gas flow He-Kr / HO of 60 s, then an O pulse with the proportions O 2 / He-Kr / H 2 O 20/45/45, for 60 s and again a carrier gas pulse of 60 s.
• propane is also oxidized in the presence of molecular oxygen.
• the effect of the injection of oxygen at the end and at the start of the propane pulse is compared by maintaining constant propane and oxygen pressures but also a constant oxygen injection duration in the propane pulse.
• the conversion ratio goes from 3300 to 2900 kg / kg from 400 to 420 ° C. b TB4 to TB6 tests
• Example 11 a The apparatus used is that described in Example 11 a).
• TC1 test Catalyst C is tested in the same way as for the TAl test. The conditions are identical except for the He-Kr flow rate which is 4.27 Nl / h and the test temperature which is 420 ° C.
• TC2 to TC4 tests are identical except for the He-Kr flow rate which is 4.27 Nl / h and the test temperature which is 420 ° C.
• the catalyst C is tested under the same conditions and in the same manner as for the TA2 test.
• the propane content is simply modified during the oxidation and the oxygen during the regeneration.
• Catalyst C is tested in the same way as for test TB7. The conditions are identical. v) TC7 test
• Catalyst C is tested in the same way as for the TB8 test.
• the conditions are identical except for the He-Kr flow rate which is 4.27 Nl / h and the test temperature which is 420 ° C. 2)
• catalyst B it is found, as for catalyst B, that the selectivity for propionic acid and for acetone increases with the partial pressure of propane, that is to say that the more the catalyst is reduced the less it is selective.
• Stage 1 dissolution - precipitation Solution A
• the assembly illustrated in FIG. 2 is used which comprises a reactor of the SVL type of 1 liter provided with an agitator connected to a motor and with a water cooler containing raschig rings.
• a nitrogen supply is installed on the reactor and a bubbler is placed at the outlet of the refrigerant. Heating is provided by a thermostatically controlled oil bath.
• 12.3 g of ammonium metavanade (MVA) ie 0.1052 mol of vanadium
• MVA ammonium metavanade
• HMA ammonium heptamolybdate
• solution B 6.1 g (0.0532 mole) of an aqueous solution of H O 2 at 30% by weight are dissolved in 98 g of water, are then added in 2 to 3 minutes to solution A. The solution becomes clear orange in 4-5 minutes. Then 40 g of ludox silica (0.2663 mole of Si) are added all at once and the solution becomes cloudy. The solution formed is called solution B.
• Solution C is prepared simultaneously with solution A: 13.2 g (0.1047 mole) of oxalic acid and 5.9 g of niobic acid (i.e. 0.0351 mole of Nb) are dissolved with stirring at 80 ° C, in 100 g of water, for 2 hours. This solution is then centrifuged at 6200 rpm for 12 minutes, to obtain a clear solution C.
• Step 2 drying The gel obtained above is dried in a ventilated oven, on teflon-coated trays, overnight, at 130 ° C. 104.2 g of dry precursor are recovered.
• This precursor hereinafter called PI, is in the form of leaves, black above, with a green film below.
• the precalcinations and calcinations are carried out in nacelles respectively under air and nitrogen flow, in steel capacities. These capacities are directly installed in muffle furnaces and the air or nitrogen supply is through the chimney. An internal thermowell allows proper temperature control. The cover prevents the return of air to the catalyst, (see figure 3)
• the precursors PI to PI 5 obtained in Examples 12 and 13 are precalcined at 300 ° C, for 4 hours, under air flow, then calcined at 600 ° C, for 2 hours under nitrogen flow of 50 ml / min / g in a muffle oven.
• the catalyst is supplied with propane and oxygen simultaneously. Helium acts as a diluent gas and water is vaporized in the gas stream.
• the catalysts are tested at 380 ° C, 390 ° C and 400 ° C with a propane / O 2 / He- ratio
• Kr / H 2 O from 10/10/45/45.
• the total flow rate of the gas flow is 8.65 Nl / h.
• the reactor is placed in an isothermal oven. It is supplied with propane, oxygen and helium by mass flow meters. An HPLC pump and a vaporizer ensure the production of steam. Thermocouples are placed in the furnace to allow regulation, and in the reactor for the measurement of the "hot spot", that is to say the highest temperature in the catalyst bed. c) Test results
• the results of the tests are recorded in the following Tables 16 and 17 in which the yields are only calculated on the basis of the routine chromatographic analyzes.
• the selectivities are calculated as the yield of a given product over the sum of the yields of products. Carbon balances are used to ensure the homogeneity of the data. They are considered acceptable for values between 95 and 105%.
• the yield calculations are based on the krypton content of the gas. The measurement of the dry gas flow rate at the outlet of the reactor makes it possible to make calculations based on this gas flow rate. The yield calculations can thus be validated.
• the yields and selectivities in each of the dosed products are given, as well as the acid yield, obtained by dosing with 0.1N sodium hydroxide. It is a pseudo yield obtained by supposing that all the acids formed have 3 carbon atoms.
• the precalcination and calcination conditions for the precursor PI 6 are grouped in Tables 18 and 19 below.
• Stage 1 dissolution - precipitation Solution A
• the assembly illustrated in FIG. 2 is used which comprises a reactor of the SVL type of 1 liter provided with an agitator connected to a motor and with a water cooler containing raschig rings.
• a nitrogen supply is installed on the reactor and a bubbler is placed at the outlet of the refrigerant. Heating is provided by a thermostatically controlled oil bath.
• 30.75 g of ammonium metavanade (MVA) ie 0.2629 mole of vanadium
• MVA ammonium metavanade
• solution A 15.25 g (0.1346 mole) of an aqueous solution of H 2 O at 30% by weight are dissolved in 90 g of water, are then added in 5 minutes to solution A. The solution turns clear orange in 4-5 minutes. Then 100 g of ludox AS 40® silica (0.6667 mole of Si) are added all at once and the solution becomes slightly cloudy. The solution formed is called solution B.
• Solution C 15.25 g (0.1346 mole) of an aqueous solution of H 2 O at 30% by weight are dissolved in 90 g of water, are then added in 5 minutes to solution A. The solution turns clear orange in 4-5 minutes. Then 100 g of ludox AS 40® silica (0.6667 mole of Si) are added all at once and the solution becomes slightly cloudy. The solution formed is called solution B.
• Solution C 15.25 g (0.1346 mole) of an aqueous solution of H 2 O at 30% by weight are dissolved in 90 g of water, are then added in
• a solution C is prepared simultaneously with solution A: 33.0 g (0.2618 mole) of oxalic acid and 14.75 g of niobic acid (i.e. 0.0877 mole of Nb) are dissolved with stirring at 66 ° C, in 250 g of water, for 2 hours. This solution is then centrifuged at 6200 rpm for 12 minutes, to obtain a clear solution C.
• Solution C is added to solution B, all at once. We get a gel orange then yellow fluid. Stirring is maintained for 30 minutes under a flow of nitrogen, under reflux.
• the gel obtained above is dried in a ventilated oven, on teflon-coated trays, overnight, at 130 ° C. 259 g of dry precursor are recovered. This precursor is in the form of leaves, black above, with a green film below. The precursor hereinafter called PI 6 is thus obtained.
• Table 19 shows the carbon selectivities.

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