MXPA99011530A - Improved vapor phase oxidation of propylene to acrolein - Google Patents

Abstract

An improved method for the selective vapor phase oxidation of propylene to acrolein in a recirculating solids reactor system using a bismuth molybdate multimetal oxide involving specific reactant concentrations (preferably 5 mol%to 30 md%propylene, 0 to 20 mol%oxygen, and the remainder inert gas), particle size (1 to 300 micrometers), temperature (250 to 450°C) and gas (1 to 15 seconds) andsolids (2 to 60 seconds) residence times. Such a process leads to improved selectivity and propylene conversion.

Description

OXIDATION IN STEAM PHASE, IMPROVED, FROM PROPILEÑO TO ACROLEINA Technical Field This invention relates to a process vapor, improved process for the catalytic oxidation of propylene to acrolein using as oxidizing particulate solids reducible in an oxidized state, and wherein the solids reduced, resulting generated separately using molecular oxygen. BACKGROUND ART An important route for acrolein is the vapor phase oxidation of propylene over a multicomponent catalyst containing molybdenum and / or other metals, usually as its oxides. The reaction step involves the oxidation of propylene with air (oxygen) to form the acrolein, together with the oxides of carbon, water and smaller amounts of other oxidized byproducts. Typically, the reaction is carried out in fixed bed, multi-tubular reactors. The large exothermic heat of the reaction and the thermal sensitivity of propylene oxidation requires low feed concentrations, expensive heat transfer equipment, large handling REF: 032171 volume of gas, and good temperature control of the reactor. A low concentration of propylene is also required to avoid flammability conditions. The magnitude of some of these problems is reduced when a fluidized bed reactor is used. The temperature can easily be controlled within a few degrees due to the mixing of intensive solids and the good heat transfer characteristics. Higher propylene concentrations can be used because the flammability damage is reduced by introducing propylene directly into the reactor, preferably pre-mixing it with air (oxygen) . However, very high propylene concentrations and low oxygen to propylene ratios in the reactor can result in over-reduced solids and reduced selectivity to acrolein. Also, the significant back-mixing of the gases in the fluidized-bed reactor results in poorer contact between the gases in the bubbles and the solids, making it difficult to obtain a high propylene conversion. Modified forms of fluidized bed reactor are known as reactor solids recirculating reactor, transport bed reactor, transport line, riser reactor, reactor fluidization, the fluidized bed reactor of multiple cameras, and by other names, depending on the design and / or personal preference. In this application the term "transport bed reactor" will be used to mean any reactor in which the solid particles are injected at one end of the reactor and are carried along with gaseous reactants at high speeds and discharged at the other end. from the reactor to a solid-gas separation vessel. An ascending reactor, in which the reactor is a vertical pipe, where the solids and reactive gases are fed to the bottom, are transported in a piston-like expense and are essentially eliminated in the upper part, it is an example of a transport bed reactor. Another example is a pipe reactor, in which the flow of solids and gases is different from vertically upwards. A transport bed reactor, as defined herein, includes a riser reactor or pipe reactor which also incorporates a zone for fluidization; that is, an area where the gas velocities are sufficiently high to carry out a substantial portion of the solids feed, but with more back-mixing of solids than would occur in the piston-type expense. The term "recirculating solids reactor system" will be used to denote a general reaction system with two reaction zones, in which two separate reactions take place and which uses a particulate solid which circulates between the two reaction zones and take part in both reactions. Optionally, either or both of the reaction zones can take place in a transport bed reactor or a fluidized bed. Such reaction systems have found use in catalytic disintegration in petroleum refining and in other reactions. U.S. Patent No. 4,102,914 discloses a process for the preparation of acrylonitrile by passing a mixture comprising gaseous oxygen, propyl and ammonium, together with an oxidation catalyst, into a transport bed reactor while controlling the linear velocity of the surface gas and the speed of feeding solids at specific speeds. The Publication of the European Office of Patents No. 0 034 442 describes a process for the preparation of unsaturated aldehydes, by passing an unsaturated olefin and an excess of gaseous oxygen in a transport bed reactor with an oxidation catalyst, solid at a gas linear velocity of 1.5 to 7.5 meters / second to substantially achieve the piston-like expense inside the reactor. The reaction products are removed from the catalyst with steam in the elimination chamber. U.S. Patent No. 4,668,802 discloses a process for preparing maleic anhydride by the oxidation of butane using an oxidized vanadium-phosphoric oxide catalyst as an oxidant, preferably that oxygen where a resulting reduced catalyst is separately regenerated, and the use of a recirculating solids reactor system for this reaction. Certain examples use a transport bed or rising reactor for the butane oxidation reaction. Japanese Patent Kokai 3-170,445 describes a similar process for preparing acrolein and acrylic acid by oxidizing propane using an oxidized bismuth-molybdenum catalyst as an oxidant. The concept of using propylene in a similar process to make acrolein is described in a document entitled "Oxidation and Ammoxidation of Propylene Oveer Bis uth Molibdate Catalyst" JL Callahan et al., Ind. Eng. Chem. Prod. Res. Develop., Vol. 9 , No. 2 (1970). The use of a bismuth molybdate composition as a direct oxidant was tested, but under the conditions of its tests, this process was deemed unsatisfactory due to the large amount of solids required by recirculation. Instead, a process was selected to use the bismuth molybdate composition as an oxidation catalyst (preferably as a direct oxidant) for commercialization. This document does not describe the improved reaction conditions of the present invention. U.S. Patent No. 4,152,393 and 4,341,717 describes a specific design of the reactor which is said to be used, among a variety of applications, for the oxidation of propylene to acrolein using an oxidized solid as an oxidant and to regenerate the reduced solids, resulting in its regeneration zone. An example of the process shows the ammoxidation of propylene using ammonia and a catalyst based on oxidized molybdenum as an oxidant. The reactor consists of a single hull containing a reaction zone and a regeneration zone, which uses a specific design containing a first upper leg, a lower first leg, a second upper leg, a second lower leg and a return leg such that the fluidized solids can be transferred from one area to the other by a route and again by a second route, and in this way the gases from one zone are not transferred to the other zone. This reactor has a complicated design which offers numerous places for potential plugging, and which limits the capacity to the monitor independently and controls the conditions of the oxidation zone and the reduction zone. This patent does not disclose the improved reaction conditions of the present invention. The concept of using an oxidized catalyst to oxidize propylene is also described in a paper entitled "Modeling of Propylene Oxidation in a Circulating Fluidized Bed Reactor," GS Patience et al., At a conference named "New Developments in Selective Oxidation II", and published by Elsevier Science BV (1994). However, while the theoretical model of this system showed that it had potential use as an alternative reactor system for the oxidation of propylene, numerous objections and doubts were listed for the development of a work process. U.S. Patent No. 4,604,370 describes a process for the regeneration of a bismuth molybdenum multi-oxide, depleted catalyst that results from its use for the oxidation of propylene to acrolein by heating it in air at 380 to 500 ° C during the less 12 hours or at 500 to 540 ° C for at least 2 hours. An adverse folder prepared by E.I. DuPont in 1973 entitled "Chemical Technologies Worldwide" included an individual sheet entitled "Transport Bed Reactor Technology for Selective Processes", which describes the general advantages of a transport or rising bed reactor, which list among the typical applications, the reaction of propylene to make acrylic acid and the reaction of propylene and ammonia to make acrylonitrile. None of the references above describe the information necessary to enable the economic use of a vapor phase process for the oxidation of propylene to acrolein which uses as an oxidant the particulate solids in an oxidized state, and where the resulting reduced solids are regenerated separately using molecular oxygen. The preparation of multicomponent compositions containing molybdenum and / or other metals and their use as catalysts in the oxidation of propylene to make acrolein is well known in the art. For example, U.S. Patent Nos. 4,677,084 and 4,769,477 describe a process for making silica-based high-wear-resistant catalysts containing molybdenum, vanadium or other metals. The molybdenum catalyst composition described was established to show good catalytic performance in a conventional process for making propylene acrylonitrile and ammonia. Numerous other patents such as US Patent No. 3,631,099, GB Patent 1,490,489 or JP Patent No. 5,301,051 also describe specific catalyst compositions containing molybdenum for use in the oxidation of propylene to acrolein in a fixed bed or fluidized bed process.

Description of the Invention The present invention relates to an improved process for steam oxidation, selective from propylene to acrolein in a reactor system of recirculating solids using multiple metal oxide solids of bismuth molybdate in oxidized form, the improvement comprises : (a) contain a feed gas containing 1% mol to 100% mol (preferably from 5 mol% to 30 mol%) of propylene, 0 to 20 mol% of oxygen, 0 to 70 mol% of water, and the inert gas, remaining with an effective amount of an oxide of multiple metals of bismuth molybdate in oxidized form comprised of particles of 100 to 300 micrometers in size, in a transport bed reactor at a temperature of 250 to 450 ° C, a residence time of the gas in the reaction zone of 1 second to 15 seconds, and a residence time of solids in the reaction zone from 2 seconds to 26 seconds; (b) removing the effluent produced in the transport bed reactor of step (a) and separating the reduced solids, resulting from the effluent gases (preferably removing any effluent gas from the reduced solids), transporting the reduced solids to a regenerating zone of the recirculating solids reactor system, and recovering the acrolein from the effluent gases; (c) oxidizing the multiple metal oxide of bismuth molybdate, reduced in the regenerating zone using an oxygen-containing gas, at a temperature of 250 to 500 ° C at a residence time of solids in the regenerating zone of 0.5 minutes at 10 minutes, and at a residence time of the gas containing oxygen from 3 seconds to 30 seconds; and, (d) recirculating the oxidized bismuth molybdate multiple metal oxide produced in step (c) to the transport bed reactor. It is an object of this invention to provide a vapor phase process, improved using a transport bed rector for the oxidation of propylene to acrolein using the oxidized form of a wear resistant solid containing molybdenum, and where the resulting reduced solids they are regenerated separately using gaseous oxygen.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic drawing of a configuration of the recirculating solids reactor in which the reaction zone is comprised of two parts, a section of fluid bed and an ascending section and the regeneration zone is comprised of of a fluid bed section. Figure 2 shows a schematic drawing of a configuration of the recirculating solids reactor in which the reaction zone is comprised of an ascending section and the regeneration zone is comprised of two parts, an ascending section and a fluid bed section.

MODES FOR CARRYING OUT THE INVENTION The present invention relates to an improved process for the selective vapor oxidation of propylene to acrolein in a recirculating solids reactor system which includes a transport bed reactor and a solids regenerator. The transport bed reactor is preferably a rising reactor in which the solid particles are injected into the bottom of a vertical pipe, brought up with gaseous reactants at high speeds and discharged into a gas separation vessel. solids, or a combination of a rising reactor with a fluidization zone. The reaction between gas and solids occurs in the riser tube in a matter of seconds, as distinguished from a conventional fluidized bed reactor where the reaction time is in a matter of minutes. The velocities of the gas in a rising reactor are approximately 2 to 15 times higher than in the fluidized bed reactors; the concentrations of the solids vary from 2 to approximately 40 times less. The products of the above reaction are then sent to a conventional processing unit where the desired acrolein is separated and recovered with any of the unreacted gases that are recirculated for further processing. The reduced solids are then reoxidized in a separate oxidation step to make possible their reuse for the oxidation of propylene. The reduced solids in the rising zone are first separated from the product gas, they are removed from any carbonaceous species in a remover zone, separated and return to the regenerator. This process allows the independent control of reactive gas concentrations, the residence time of the gas and the residence time of the solids in each zone for optimal operation. There are several advantages of the above reagent concept over the permanent bed or alternate fluidized bed. The high selectivity is achieved due to the piston type expense and the oxidative, optimum state of the solids. Significant reductions are made in product recovery costs because the regeneration of the discharge gas stream is kept separate from the product gas stream, resulting in a highly concentrated product stream. The high yield ratios are attributed to the independent control of variables for the two steps of the operation, which results in a reduced investment and a decreased solids stock. When a hydrocarbon oxidation reaction is carried out in the absence of molecular oxygen, the crosslinked oxygen of the surface layers of these mixed metal oxide solids is consumed very rapidly, typically in a matter of seconds. When that happens, the activity of solids decreases dramatically. If the solid is allowed to remain in the reduction atmosphere, the reduced surface layers are built in an oxidized core because the diffusion of the reticular oxygen in volume to the surface is generally very low in the most practical situations. These reduced layers decrease the selectivity and cause excessive yield losses when they are oxidized in the regenerator of solids to carbon oxides. The above processes for the processes of oxidation of propylene to acrolein which use an oxidant with a separate regeneration zone for the solids do not describe the surprising benefit of a short residence time in the propylene oxidation / solids reduction zone. In carrying out the inventive process, the feed gas for the propylene oxidation step contains about 1 mol% to 100 mol% propylene, preferably about 5 mol% to about 30 mol% propylene. Some of the propylene used in the feed may be provided by the unconverted propylene which is present in the recirculated reaction gas. In some cases, propylene may be available as the predominant component in a gas mixture that includes other hydrocarbons; for example, the technical propylene used in the industry may contain 95% mol of propylene and 0 to 5% mol of propane. Since none of the other gases present significantly and adversely affects the process, it may be more convenient to use this propylene-rich mixture in the feed gas as the source of propylene. The concentration of oxygen in the feed gas can be from 0 to 20 mol%. The air can be used as the source of oxygen. The remainder of the feed can be any inert gas, such as nitrogen or recirculated reaction gas containing mainly water, carbon monoxide and carbon dioxide, and possibly unconverted propylene. The present invention utilizes an effective amount of a multiple metal oxide of bismuth molybdate in oxidized form. Preferably, this is a solid particle, especially hardened, which resists wear, as described in US patents Nos. 4,677,084 and 4,769,477 previously referenced. Numerous other bismuth molybdate metal oxide compositions are described in the art for the vapor phase oxidation of propylene to acrolein and are also suitable for the operation of this invention. It should be further appreciated that other transition metal oxidizing systems known in the art that promote the oxidation of propylene to acrolein, such as, for example, but not by way of limitation, the iron oxide / antimony metal solids, should be consider equivalents for purposes of the process of the present invention. The solid particles are preferably from about 20 to about 300 microns in size. The oxidation step is carried out in the reaction zone at a temperature of about 250 to about 450 ° C. The outlet pressure of the reactor gas is typically 3.511 kg / cm2 (0-50 psig). The residence time of the gas in the reaction zone is from about 1 second to about 15 seconds, and the residence time of the solids in the reaction zone is from about 2 seconds to 60 seconds. The upper limit of residence time of the solids will depend on, of course, the activity of the solids. If they are still active, solids can be held in the reaction zone for more than 60 seconds. Preferably, the solids are removed from the oxidation step when the oxidative surface layer of the solids has been substantially reduced to a non-oxidized form. The solids in the reactor effluent are separated from the effluent gases, and the acrolein product is recovered from the effluent gases, both separations using conventional techniques and equipment. The separated solids are referred to herein as reduced solids because they are in a lower oxidation state than that of the new solids which enter the reaction zone. When suitable for the mode, the reduced solids are preferably removed from any of the reactor gases and then transported to the regeneration zone of the recirculating solids reactor system. The removed reactor gases are mixed with the effluent gases from the reactor. Acrolein is recovered from the effluent gases in the reaction zone, the remaining gases can be discharged or recirculated to the reaction zone. Any of the exhaust gases from the regeneration zone can be released after heat recovery. Since this reaction is highly exothermic, the removal of heat from the recirculation reactor system can be done through the use of cooling coils, preferably in the solids regenerator but if necessary also in the fluidization of the feed and / or eventually in the ascending section. The reduced solids are oxidized again in the regeneration zone using a gas containing oxygen such as air. The temperature of the regeneration zone is maintained at about 250 to about 500 ° C. The residence time of the solids in the regenerator zone is approximately 0.5 minutes, typically, approximately 10 minutes. The residence time of the oxygen-containing gas is from about 3 seconds to about 30 seconds. The flow velocity of the total gas and the concentration of oxygen must be sufficient to provide the oxygen necessary for the reoxidation of solids to occur within the selected gas and the residence time of the solids. The oxidized solids are then recirculated to the reaction zone. The required amount of solids and the flow velocity of the solids required depend on the degree to which the oxidation reaction of solids is carried out in the regeneration zone (as opposed to the reaction zone), the amount of propylene for to be reacted, the amount of mobile (or reactive) oxygen contained by the solids, and the process conditions in the reaction zone that determine the amount of oxygen in the solids used per pass. When the concentration of oxygen in the reaction zone is low, or zero, and substantially all of the reoxidation reaction of the solids is carried out in the regeneration zone, a high solids circulation velocity is required. This speed can be reduced, to the extent that the reoxidation reaction of the solids is carried out in the reaction zone. A reactor system of recirculating solids can be operated continuously to oxidize propylene without any oxygen in the gas phase in the reaction zone. Such an operation results in that a higher selectivity can be achieved "to make the acrolein with conventional reactors, provided that an adequate rate of recirculation of the solids is maintained in order to supply the oxidized solids, necessary. gaseous phase in the reaction zone, the oxygen gas phase is removed from the oxidized solids before recirculating them to the reaction zone Alternatively, if a reactor system of recirculating solids is operated to oxidize the propylene under temperature conditions , partial pressures of oxygen and propylene and residence time in the reaction zone identical to those used in conventional reactors, a significantly higher conversion of propylene and a significantly higher yield of acrolein are obtained.The high selectivity to acrolein achieved in the transport bed reactor it is maintained even if the food tion to the reaction zone has a very high propylene concentration. The gas feed can be 100% propylene. The recirculating solids reactor systems can have many different reactor / regenerator configurations in general. For example, the reaction zone of the system may be comprised of a transport bed reactor, a fluidized bed reactor or other gas-solids reactors, as the regeneration zone may. The recirculating solids reactor system employed in this invention utilizes a transport bed reactor for the reaction zone. Optionally, the transport bed reactor may comprise a riser reactor, a pipe reactor, or a riser or pipe reactor combined with a fluidization zone. The regeneration zone of the regenerator may be comprised of a rising reactor, a pipe reactor, a fluidized bed reactor of any type, or a combination of the above reactors. It should be understood that the invention is not limited to the specific combination of the reactors listed above. A transport bed reactor are characterized by high gas velocities of approximately 1.5 m / sec. (approximately 5 feet / sec.) to more than 12 m / sec. (40 feet / sec.). At the lower end of the speed range there may be a significant amount of local back-mixing of the solids. Typically, the reactor line is mounted vertically with gas and the solids that flow upward in the piston-type run essentially; that is, an ascending reactor. Preferably, the velocity of the surface gas in the rising section is maintained at 1 to 10 meters / seconds. The flow can also be downward and the reactor line can be mounted different from vertically, ie a pipe reactor. The concentration of the solids in the reaction zone of the reactor can vary from, typically about 16 kg / m3 (about 1 lb / ft3) to, typically, about 160 kg / m3 (10 Ib / ft3), depending on the speed of the reactor. gas, size and density of the particles, and the speed of circulation of the solids. Preferably, the flow of the solids (mass flow rate per unit area) is 50 to 1000 kg / m2 'sec. FIGURE 1 is a schematic drawing of one of the recirculating solids reactor systems used in the examples. The reaction zone is comprised of a fluidization section 1 and an ascending section 2. The feed gas enters 1 and the oxidation of the propylene takes place in sections 1 and 2. The separating-removing unit 3 separates and removes the effluent gases of the reaction zone of the reduced solids. The acrolein product is recovered from the effluent gases from the leaving reactor 3. The reduced solids are transported to the regeneration zone which is comprised of the fluidized bed section 4. The reduced solids are oxidized again in section 4 and the oxidized (regenerated) solids are then recirculated to the fluidization section 1. The alternative / additional feed line 5 can be used to feed the additional oxygen to the rising section 2. The recirculating solids reactor of this embodiment can also be operated with only the ascending section 2 as the reaction zone. In this mode of operation, the feed may be introduced into the rising section 2 through the feed line 5. FIGURE 2 is a schematic drawing of another recirculating solids reactor system used in the examples. The reaction zone is comprised of an ascending section 11. The feed gas enters 11 and the oxidation of the propylene takes place at 11. The separating-removing unit 12 separates and removes the effluent gases from the reaction zone from the reduced solids. The acrolein product is recovered from the outgoing reactor effluent gases 12. The reduced solids are transported to the regeneration zone which is comprised of an ascending section 13 and a fluidized bed section 14. The reduced solids are oxidized in this. regeneration zone and the oxidized (regenerated) solids are then recirculated to the rising section 11. The reaction and regeneration zones may be within an individual reactor, although better process control is usually achieved if the two are in separate units. The conversion of propylene in percent is defined as 100 times the number of moles of propylene converted, divided by the number of moles of propylene in the feed. The selectivity for acrolein in percent is defined as 100 times the number of moles of propylene converted to acrolein divided by the total number of moles of propylene converted. The yield of acrolein in percent is defined as 100 times the number of moles of acrolein formed divided by the number of moles of propylene in the feed. As previously indicated, there are a number of bismuth molybdate oxidants described in the art as suitable for the oxidation of propylene to acrolein, the process of this invention is not limited to a particular method for making this solid, nor to a promoter particular. The following examples are presented to more fully demonstrate and further illustrate various individual aspects and characteristics of the present invention and the indications are proposed to further illustrate the differences and advantages of the present invention. As such, the examples are felt to be non-limiting and are intended to illustrate the invention but are not implied to be unduly limiting. Example 1 The wear resistant solids used in the examples of this invention were prepared by substantially following the procedure of US Pat. No. 4, 677,084 and in particular the process found in Example 10. The starting solids used to make the wear-resistant solids were obtained following the procedure described in the French patent application No. 97 0243 filed on February 27, 1997 in the name of ELF ATOCHEM SA and in particular when using multiple component molybdate obtained according to example 5 of the French patent application. The starting solids, prepared according to this French application, correspond to the formula: Mo? 2Co3.5Bi? .1Fe0.8Wo.5Si? .4Ko.o5? \. The procedure involves 60.9 grams of Co (N03) 2 * 6H20 that dissolves in 20 L of distilled water. Also, 20.2 grams of Fe (N03) 3'9H20 were dissolved in 15 mL of distilled water and 31.2 grams of Bi (N03) 3'5H20 were dissolved in 30 mL of distilled water, acidified with 6 mL of HN03 at a concentration of 68% in volume. Separately, 127.4 grams of (NH4) 6Mo702 '4H20 were dissolved in 150 mL of water with heating and stirring then 7.4 grams of W03 were added. The aqueous solution containing the cobalt was introduced dropwise during 20 minutes into the aqueous solution of the ammonium salts. The ferric solution was then introduced for 10 minutes and then the solution containing the bismuth for 15 minutes. A solution obtained by dissolving 0.2 grams of KOH and 12.8 grams of colloidal silica (at a concentration of 40% by weight) in 15 L of water was added for 10 minutes to the resulting gel. The gel thus obtained was mixed for 1 hour at room temperature and then 1 hour at 70 ° C. The gel was then dried for 18 hours at 130 ° C to obtain a solid precursor. The solid obtained was pre-calcined at about 225 ° C in air. This precalcined solid was then milled and mixed with a solution of polysilicic acid as described in Example 10 of the 4,667,084 patent. The slurry was then dewatered by spray and the resulting solids were calcined for 9 hours at about 450 ° C in air to produce the wear resistant solids used in the following test 1 to 34 of Example 1. A reactor system was used. recirculating solids of the type shown in FIGURE 1 to oxidize propylene to acrolein. The transport bed reactor consisted of a small fluidization section traced by an ascending pipe of 1.5875 centimeters (5/8") in diameter by 3.05 meters (10 ') high.The recirculating solids were transported to the riser with the Reactive gases and the product which are in the piston type expense The contact times of the reactive gas were in the order of 1-5 seconds The isothermal conditions were maintained by an electric furnace The temperatures were maintained in the range of 250-450 ° C. The reactor pressure was maintained from the atmospheric pressure to 0.140432 kg / cm2 (2 psig) .The surface gas velocity, rising was in the range of 2.016-3.203 meters / second (6.6-10.5 feet / second) The contact time of the rising gas was in the range of 1.3 to 1.5 seconds.The concentration of propylene feed was varied as shown in the tables below. They saw in the range of 9-33% in mol. All feed flows were controlled by thermal mass flow controllers. The propylene and nitrogen were fed either to the fl uidization zone or directly to the riser (short-circuiting of the fluidization zone). The solids and gas stream of the product were separated in a stripper and a series of cyclones. The remover was a fluidized bed of 1.22 meters (4 ') in diameter. After decoupling and removal of the solids, the gas leaving the product was fed to the product's abrupt cooling / absorption system. The contact time of the solids in the remover was in the range of 15 seconds to 10 minutes. Of the remover, the solids were then transported to the regenerator. The regenerator was a fluidized bed of 11. 43 centimeters (4.5") in diameter The bed height of the solids (contact time of the solids) in the regenerator was controlled by differential pressure control between the remover and the regenerator, the air was fed to the regenerator to return To oxidize the solids, the contact time of the solids was in the range of 1-21 minutes.The gas leaving the regenerator's exhaust gas was fed to the cooling system of the regenerator after the decoupling of the solids in a series of cyclones From the regenerator, the oxidized solids were then fed back to the fluidization section of the transport bed reactor.The circulation velocity of the solids was in the range of 15-250 kg / hr. The outlet gas for the product and regenerator gases were of identical design.A recirculating liquid served as a direct contact condenser / absorber to the products A caustic substance was used in the product's outlet gas to absorb the organic products and dimerize the acrolein produced. Water was used in the regenerator outlet gas. A hot gas sample stream was taken from the product outlet gas for two static water absorbers. The first was used to absorb the C2 / C3 aldehydes and the acids for quantitative analysis by off-line gas chromatography. The second one was used as a pre-treatment absorber to eliminate the aldehydes and acids which interfere with the analysis, before the gas chromatographic analysis in line of N2, 02, propylene, CO and C02 • A sample of the gas was taken out of the regenerator downstream of the water suddenly cooled and analyzed for N2, 02, propylene, CO and C02. The performance of the reactor was determined by the gas chromatographic analysis in line for the components not absorbed in each of the outgoing gas streams. The products absorbed by the water were measured by the off-line gas chromatographic analysis of the liquid sample absorber. The composition of the feed gases is present in the tables as% mol propylene, steam and nitrogen. If air was used, the quantity is identified in a footnote. In some of the tests the contact time may have increased by directing the gases to the bottom of the fluidized bed preferably than the base of the ascending section (see feeding line 5 of FIGURE 1). The primary process variables in the following tables are abbreviated as follows: Temp. Fluid. Bed ° C (temperature of the fluidized bed in ° C), Food Conc. C3H6% in mol (concentration of propylene feed in mol%), Time Cont. Gas sec (gas contact time in seconds), and Vel . Sun. Kg / hr (speed of circulation of solids in kilograms per hour). The primary responses were measured when the key variables of the process were changed, and were abbreviated in the tables later as follows: Conver. Propylene% (percentage of propylene conversion) and Select. C3 / C2% (percentage of selectivity for the reaction products C3 and C2). The tests were grouped into three sets (Tables 1, 2 and 3 below). The first set (Table 1) included tests where all secondary, ascending feeds went to the fluidization bed.

Table 1 PROCESS VARIABLES ANSWERS Temp. Conc. Alim. Time C el. Circ. Conver. Select. of Fluid. C3H6 / vapor / N2 Gas Sol. Propylene c3 / c2 'Rueba Lecho ° C% in mol seg Kg / hr%% 1 351 10.5 / 8.8 / 80.6 2.0 25 22.5 85.0 2 352 10.5 / 8.9 / 80.6 2.0 23 20.2 82.2 3 359 11.1 / 9.9 / 79.0 2.3 131 46.4 85.1 4 355 11.6 / 10.0 / 78.4 2.4 252 61.3 83.7 351 10.6 / 9.3 / 80.1 2.2 30 15.5 87.7 6 352 10.5 / 9.4 / 80.1 2.1 78 26.2 82.9 7 353 10.4 / 9.3 / 80.3 2.1 72 30.4 83.5 8 350 10.6 / 9.3 / 80.1 2.2 72 27.2 82.5 9 351 10.6 / 9.3 / 80.1 2.3 72 24.9 83.5 351 10.4 / 9.1 / 80.5 2.2 68 37.0 87.9 11 352 14.7 / 8.7 / 76.6 2.0 58 27.1 89.3 12 347 6.6 / 9.2 / 84.2 2.2 53 31.4 85.2 13 350 9.6 / 8.4 / 82.0 2.0 40 26.9 88.0 14 350 10.5 / 9.3 / 80.2 2.2 135 57.0 84.3 333 10.2 / 8.8 / 81.0 2.2 39 12.7 82.4 16 * 363 10.6 / 8.7 / 73.8 2.0 25 48.5 86.0 17 373 10.6 / 9.3 / 80.1 2.1 23 17.9 81.4 * 10 SCFH of air supply to the fluidization bed (6.8% in mol in feed) The second set of tests (Table 2) includes the tests where the nitrogen feed was divided between the fluidization bed and the ascending section to increase the contact time of the gas and the concentration of propylene in the fludization bed.

Table 2 PROCESS VARIABLES ANSWERS Temp. Conc. Food Time Cont. Vel. Circ. Conver. Select. of Fluid. C3Hß / vapor / N2 Gas Sol. Propylene c3 / c2 Test Lecho ° C% in mol sec Kg / hr%% 18 352 49.4 / 9.1 / 41.5 3.9 17 7.9 40.3 19 345 26.9 / 9.1 / 64.0 3.1 107 12.1 69.2 333 33.0 / 9.2 / 57.8 2.6 95 23.9 89.8 21 328 49.1 / 9.1 / 41.8 3.9 13 4.5 32.5 22 326 25.6 / 9.1 / 65.3 3.0 13 2.9 20.2 23 380 26.9 / 9.3 / 63.8 3.0 164 43.0 67.6 24 383 17.0 / 9.5 / 73.5 2.5 30 40.4 80.6 372 16.7 / 9.5 / 73.8 2.5 16 26.3 89.0 26 373 10.6 / 9.3 / 80.1 2.1 23 17.9 81.4 The third set of tests (Table 3) included the tests where all the propylene feed went to the rising section (no propylene was fed into the fluidized bed).

Table 3 PROCESS VARIABLES ANSWERS Temp. Conc. Food Time Cont. Vel. Cyrus. Conver. Select. of Fluid. C3Hs / vapor / N2 Gas Sol. Propileno c3 / c2 Test Lecho ° C% in mol sec Kg / hr%% 27 350 21.1 / 9.5 / 69.3 1.5 18 21.3 92.3 28 348 21.1 / 9.5 / 69.3 1.5 21 15.9 95.5 29 347 24.0 / 9.6 / 66.3 1.5 22 15.7 94.6 347 23.8 / 9.5 / 66.7 1.4 19 13.1 89.2 31 348 5.4 / 9.8 / 84.8 1.5 18 13.7 77.6 32 345 21 .1 / 9.5 / 69.4 1 .4 17 17.8 91 .5 33 349 10.4 / 9.4 / 80.2 1.4 15 17.0 84.1 34 * 349 10.2 / 9.3 / 73.1 1 .4 18 21.0 82.1 * 10 SCFH of air supply to the fluidized bed (7.4% in mol of feed) The results were very good with the best results obtained with the propylene feed to the ascending section as in Table 3 (where there is a piston-type expense and no back-gassing). The best test results are as follows: Selectivity for C3 / C2 > 95% Conversion of the rising section + Fluidised bed > 60% Solids Conversion Ratio < 400 kg / kg Two tests (shown by *) with air supply to the ascending section were run. One test was conducted with all feeds to the fluidized bed, and one fed with propylene to the rising section. The fluidized bed feed test resulted in a significantly higher conversion of the rising section. The feed test to the rising section resulted in a somewhat higher conversion and little change for selectivity. The best performances were achieved when the completely oxidized solids were reduced in the rising section in such a way that essentially all readily labile oxygen is consumed and the solids are removed from the reducing atmosphere immediately.

Example 2 In a manner similar to the procedure of Example 1, a series of four additional runs were performed in the recirculating solids reactor of the type shown in FIGURE 1. In these runs the propylene was converted to acrolein using the metal oxide solids. commercially purchased bismuth molybdate manifolds as the oxidant. The bismuth molybdate multiple metal solids, employed, had a history of being used commercially in a DuPont Beaumont facility for the manufacture of acrylonitrile and being rejuvenated after showing a decrease in manufacturing activity of acrylonitrile. The rejuvenation process involved the addition of molybdenum to the spent catalyst. The process variables and the data of the test results are presented in Table 4.

Table 4 PROCESS VARIABLES ANSWERS Temp. Conc. Food Time Cont. Vel. Cyrus. Conver. Select. of Fluid. C3Hß / vapor / N2 Gas Soi. propiieno Acroleína y Test Bed ° C% in mol sec Kg / hr% Acrylic Acrylic% 346 2.0 / 5.0 / 93 2.4 84 75.69 100 36 346 6.0 / 5.0 / 89 2.4 83 52.89 99.09 37 353 10 / 5.0 / 85 2.4 72.7 34.33 98.45 38 352 20 / 5.0 / 75 2.4 61 14.55 96.25 Example 3 In a manner analogous to the procedure of Example 1, a series of four additional runs were performed in the recirculating solids reactor of the type shown in FIGURE 1. In these runs, the propylene was converted to acrolein using essentially the same oxide composition. multiple metals of bismuth molybdate as used in Example 1. The only difference was that the salt precursor after drying was not pre-calcined at 225 ° C in air but instead was ground directly to the desired particle size range and mixed with a polysilicic acid solution. This slurry was then dewatered by spray and the resulting solids were preheated to 225 ° C in air and then calcined at 450 ° C for 9 hours in air to produce the wear resistant solids. The process variables and the data of the test results for these additional runs are presented in Table 5.

Table 5 PROCESS VARIABLES ANSWERS Temp. Conc. Food Time Cont. Vel. Cyrus. Conver. Select. of Fluid. C3H0 / vapor / N2 Gas Sol. Propylene Acrolein and Test Lecho ° C% in mol sec Kg / hr% Acid Acrylic% 39 353 2.0 / 5.0 / 93 2.4 62 67.66 93.44 40 348 6.0 / 5.0 / 89 2.4 75 51.69 90.90 41 349 10 / 5.0 / 85 2.4 59 42.22 88.52 42 350 20 / 5.0 / 75 2.4 71 21.03 86.84 Having thus described and exemplified the invention with a certain degree of particularity, it should be appreciated that the following claims should not be limited in this manner, but that a scope should be given in proportion to the text of each element of the claim and equivalents thereof.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (9)

1. An improved process for vapor phase oxidation, selective from propylene to acrolein in a recirculating solids reactor system using a multiple metal oxide of bismuth molybdate in oxidized form, the improvement is characterized in that it comprises: (a) putting in contact with a feed gas containing 1 mol% to 100 mol% propylene, 0 to 20% in mol of oxygen, 0 to 70% in mol of water and the rest of inert gas with an effective amount of the oxide of multiple metals of bismuth molybdate in oxidized form comprised of solid particles of 10 to 300 micrometers in size , in a transport bed reactor at a temperature of 250 to 450 ° C, a residence time of the gas in the reaction zone from 1 second to 15 seconds, and a residence time of the solids in the reaction zone of 2 seconds to 60 seconds; (b) removing the effluent produced in the transport bed reactor of step (a) and separating the multiple metal oxide of reduced bismuth molybdate resulting from the effluent gases, transporting the multiple metal oxide of bismuth molybdate, reduced to a regenadora zone of the recycling solids reactor system and recover the acrolein from the effluent gases. (c) oxidizing the multiple metal oxide of bismuth molybdate, reduced in the regenerating zone using an oxygen-containing gas, at a temperature of 250 to 500 ° C at a residence time of the solids in the regenerating zone of 0.5 minutes at 10 minutes, and at a residence time of the gas containing oxygen from 3 seconds to 30 seconds; and (d) recirculating the oxidized bismuth molybdate multiple metal oxide produced in step (c) to the transport bed reactor.

2. A process according to claim 1, characterized in that the feed gas contains from 5 mol% to 30 mol% propylene.

3. A process according to claim 1, characterized in that the transport bed reactor is a riser or pipe reactor.

4. A process according to claim 1, characterized in that the velocity of the surface gas in the rising section is maintained at 1 to 10 meters / sec.

5. A process according to claim 1, characterized in that the flow of the multiple metal oxide of bismuth molybdate (mass flow rate per unit area) is 50 to 1000 kg / square meter / second.

6. A process according to claim 1, characterized in that the regenerating zone is a fluidized bed, and the oxygen-containing gas for the regenerator is air.

7. A process according to claim 1, characterized in that the multiple metal oxide of bismuth molybdate was prepared from a slurry of multi-metal salt by drying the slurry to produce a solid, precalcining the solid at a temperature of about 225 ° C, grinding the precalcined solid to produce particles, adding the solid particles to a polysilicic acid solution, dehydrating by aspersion and calcining the dehydrated particles by spray at approximately 450 ° C.

8. A process according to claim 1, characterized in that the multiple metal oxide of bismuth molybdate is an acrylonitrile catalyst of commercial grade.

9. A process according to claim 1, characterized in that the multiple metal oxide of bismuth molybdate was prepared from a slurry of multiple metal salts by drying the slurry to produce a solid, grinding this solid to produce particles, adding the solid particles to a solution of polysilicic acid, dehydrate by aspersion, precalcinar and calcined in the air.