DE1152685B - Process for the preparation of ªú¼ª-unsaturated aldehydes and ketones by partial oxidation of olefins having at least 3 carbon atoms in the molecule - Google Patents

Description

Process for the preparation of α, β-unsaturated aldehydes and ketones by partial oxidation of olefins with at least 3 carbon atoms in the molecule Die The invention relates to a process for the preparation of α, f-unsaturated aldehydes and ketones by partial oxidation of olefins having at least 3 carbon atoms in the molecule, especially the production of aerolein and methacrolein from propylene or isobutylene.

In the main patent application is a process for the production of a, fl-unsaturated aldehydes and ketones by partial oxidation of olefins with at least 3 carbon atoms in the molecule in the vapor phase by means of a free oxygen containing gas mixture in the presence of water vapor at elevated temperature and described under the influence of a heavy metal-containing oxidation catalyst. the reaction being carried out according to the dust flow process in such a way that that the olefin of a previously formed suspension of the catalyst in a free oxygen-containing gas is added and the mixture obtained by one of externally cooled tubular reaction zone of smaller cross-sectional area than that Catalyst cooling zone passes, which is kept at a temperature between 250 and 750 ° C being the catalyst during its passage through the reaction zone holds in suspended form a gas containing free oxygen into the reaction zone introduces the catalyst at several points along its length from the The vaporous mixture emerging from the reaction zone is separated off and transferred to a cooling zone leads, which is in open communication with the reaction zone, a free oxygen containing gas passes through the catalyst located in the cooling zone, whereby Catalyst particles are entrained and the suspension of the catalyst forms.

It has now been shown that this method is advantageous can be modified if, according to the invention, the catalyst cooling zone is also added Introduces water.

In a preferred forum for carrying out the invention, the Walls of the reaction zone cooled by indirect heat exchange, and here Evolved vapor is used to strip the catalyst exiting the reaction zone used.

The generation of steam with the help of a hot catalyst is known likewise the cooling of a catalyst layer by injecting water at the same time Generation of steam. Furthermore, the introduction of olefins is already part of the olefinic one Oxidation with oxygen known at several points in the reaction vessel. At the Process according to the invention, however, the water is not introduced into the reaction zone. but together with an oxygen-containing gas through a in a separate one Container existing fluidized bed passed.

Air can be used as the oxygen-containing gas, but a particular advantage of the method according to the invention is the possibility of Use gases with a high oxygen content. By cooling the catalyst with water in a zone in front of the reaction zone, is within the system so much steam is generated that the catalyst is suspended in by the reaction zone State is performed. For this reason, the inert gas components are not required a gas mixture containing oxygen in a low concentration, such as air. The use of the steam developed in the system to transport the catalyst through the system reduces the size and, consequently, the cost of implementation the reaction and to isolate the Reaction products necessary Investments. The generation of steam through indirect heat exchange with the catalyst in the system not only allows the elimination of the steam generation required for this outside the system, but allows the generation of the required amount of steam with the least amount of equipment.

The reaction is preferably carried out at a pressure of 3.5 to 10.5 kg / cm 2. The invention is illustrated by means of a flow diagram of a plant for the production of acrolein.

An oxygen-containing gas, e.g. B. obtained by fractionating air Oxygen of 95 per cent purity, is supplied through the valved line 10 in a zone containing catalyst of relatively large cross-sectional area, e.g. B. a chamber 11, initiated. The chamber 11 contains a bed of a heavy metal containing Oxidation catalyst, which accelerates the oxidation of propylene to aerolein, The catalyst is preferably an oxygen-containing compound of molybdenum, z. B. bismuth molybdate or a. Phosphomolybdate, optionally in combination with a catalyst support, preferably based on silica or aluminum oxide. The catalyst in chamber 11 exiting the reaction zone as follows is described is at an elevated temperature.

In general, the reaction system before the start of the partial Oxidation brought to the reaction temperature. The one to initiate the reaction required conditions can be obtained by bubbling hot gas therethrough.

Aqueous, at least partially, from the system through lines 14 and 50 resulting streams are also introduced into chamber 11. When they meet with the hot catalyst in chamber 11, the water is converted into steam. When passing through the catalyst bed in chamber 11, the molecular Oxygen and steam containing gas streams the catalyst in the form of a vortex dense bed and form one exiting from the chamber 11 into the reaction zone 15 Gas stream containing steam, molecular oxygen and entrained catalyst.

The chamber 11 is in open communication with the tubular reactor 15 with a smaller cross-sectional area. The tubular reactor is equipped with cooling jackets 16, 17 and 18 provided. The reactor 15 opens into a catalyst separation zone, e.g. B. a cyclone 23. The reactor 15 is of the type sometimes used in industry referred to as a riser reactor.

The steam, oxygen and entrained steam exiting chamber 11 Gas stream containing catalyst is passed upward through reactor 15. The catalyst-containing gas stream which enters the reactor 15 from the chamber 11, is combined with a normally gaseous olefin feed, e.g. B. Contains propylene. The olefin feed is the inlet of the reactor 15 through the Line 21 supplied.

The olefin feed from line 21 can enter reactor 15 below Use of a jet pipe, a nozzle, a ring provided with holes or similar injection devices are initiated. The combined gas flows, which contain the entrained suspended catalyst are in cocurrent passed upward through the reactor 15 and enter the cyclone 23, in from which the catalyst is separated off and returned to chamber 11 through line 25 will.

The reactor 15 is at a temperature between about 350 and about 550 ° C, preferably between about 400 and about 500 ° C. The pressures will in the reactor 15 between about normal pressure and about 35 kg / cm2, preferably between 3.5 and about 10.5 kg / cm2 held.

Steam, oxygen and olefin feed are fed into the system with such Velocity introduced that there is a flow velocity at which at least the greater part of the catalyst entrained into the reactor 15 does this in a suspended state. The respectively maintained flow velocity through the reactor 15 depends on the physical properties of the used Catalyst and the selected contact time. The contact time can vary widely vary. For example, a contact time of between approximately 0.05 and 30 is sufficient Seconds, in particular between about 0.05 and about 20 seconds. Shorter or longer However, contact times can be used. Preferably, however, the reaction with short contact time, e.g. B. in the range between about 0.05 and about 10 seconds, carried out.

The oxidation of propylene to acrolein-containing reaction products is exothermic. The desired reaction temperature is maintained in the reactor 15 by the controlled removal of the heat released in the reaction zone and by controlling the temperature of the catalysts and reactants introduced into the reactor 15. This is mainly achieved by bringing the hot catalyst in chamber 11 into direct contact with water. If larger amounts of water are required for introduction into the chamber 11 than can be supplied through the lines 14 and 50, these additional amounts of water can be supplied through the valve provided with line 13 and possibly in other ways not shown in the drawing. With the aid of the catalyst as a carrier, heat is transferred from the reactor 15 into the chamber 11. Here the catalyst is cooled to the desired temperature while water evaporates at the same time. The steam necessary to maintain the catalyst flow through the system and to suspend the catalyst in the reactor 15 as well as to properly control the reactor temperature conditions is thus retained in the system as a result of the method of heat removal according to the invention. Significant amounts of steam are generally required and the generation of this steam has heretofore been a significant cost of labor for such processes. The process of the invention now allows a considerable reduction in labor costs by utilizing the heat released in the system during the reaction in the manner described. An additional removal of the heat released during the reaction from the reactor 15 is carried out by passing a coolant, for. B. steam condensate, from the steam boiler 25 through one or more of the cooling jackets 16, 17 and 18 through the valved lines 26, 27 and 28 caused. The steam formed in the cooling jackets is returned to the steam boiler 25 through lines 30, 31 and 32. Cooling water is supplied to the system through line 33.

Line 43 is used to introduce a suitable deterrent, e.g. B. water, into the cyclone 23. The hot catalyst coming from the cyclone 23 is stripped with steam which exits the steam boiler 25 through the pipes 12 and 35 provided with valves. This stripping of the catalyst with steam removes at least considerable amounts of adhering residual organic material and thereby not only improves the efficiency of the operation of the reactor, but also extends the life of the catalyst.

If necessary, you can steam from the steam boiler 25 through the lines Introduce 35, 12 and 10 into chamber 11 to aid maintenance the desired reaction conditions. Any additional amounts of steam that may be required can fed into the system from outside by means not specified in the drawing will. Steam can also enter the reactor 15 at one or more points along its length z. B. through the valved lines 39 and 40 and others Lines not shown in the drawing are fed.

A considerable advantage of the process in which the heat released during the reaction is used in the manner described is that the process can be carried out at a relatively high oxygen concentration, not only at the inlet of the reactor 15, but also in its larger part, without the disadvantages occurring so far as a result of local overheating and the resulting degradation of the product occurring. Preferably, oxygen is added to the system in an amount such that the molar ratio of oxygen to olefinic hydrocarbon is at least 0.5: 1 and preferably between about 0.8: 1 and about 1.5: 1. In the process of the invention, oxygen gas, in addition to the oxygen introduced through line 10, is supplied at a plurality of locations along the length of the reaction zone. The oxygen is additionally introduced from line 10 through lines 37 and 38 into reactor 15 at a plurality of locations. The ability to supply oxygen in this manner at a plurality of locations along the length of the reaction zone in the process of the invention without simultaneous overheating, together with the relatively high reaction rate, allows the partial oxidation of propylene to aerolein at an unusually high reaction rate.

Propylene is co-settled under the conditions given above molecular oxygen in the reactor 15 with the formation of aerolein containing Reaction products. Catalyst storage facilities and lines are provided, through which the catalyst can be routed to and from the system.

The water vapor leaving the reactor, unreacted hydrocarbon gas including propylene, aerolein and some entrained catalyst Gases exit cyclone 23 through an indirect heat exchanger 47 line 46 provided to a suitable catalyst separation device for the catalyst slurry a, z. B. a chamber 48. When passing through the indirect heat exchanger 47, the hot gases coming from the reactor are cooled, with at least some of the water vapor condenses. The separating in the chamber 48 Aqueous catalyst slurry is returned to chamber 11 through line 50. Because of this partial condensation of the gases flowing out of the reactor in the heat exchanger 48 facilities must be available to remove the catalytic converter dust separate it and return it to the reaction zone as a slurry, at the same time water is returned to the chamber 11 for cooling.

Including the aerols and unreacted hydrocarbons Propylene containing gases are released from the chamber 48 by means of an indirect Line 51 provided with heat exchanger 52 is fed into a phase separator 53. At the Passing through the heat exchanger 52, the gas flow is cooled down to such an extent that that at least some of the reaction products condense. The unreacted, A vapor phase containing hydrocarbons and aerolein is extracted from the phase separator 53 led through line 55 into a device for the recovery of corsetry of product, which consists of an absorber 56. In the absorber 56 is the feed with a Combined absorption medium that selectively absorbs aerolein. As an absorption medium serves z. B. Water entering the system through the conduit provided with a cooler 58 57 is fed. The washing solution, consisting essentially of water and aerolein containing reaction products is from the absorber 56 through the line 64 guided into a scraper 65. The liquid separated off in the phase separator 53 Phase is also passed through line 63 into scraper 65. In the scraper 65 becomes a vapor phase containing aerolein from a liquid containing water Phase separated. The liquid phase comes out of the scraper 65 through the lines 68, 14 and 57 are guided into the upper part of the absorber 56. Containing the aerolein Vapor phase is overhead from stripper 65 through line 67 as the end product deducted. A portion of the liquid withdrawn from the scraper 65 is passed through the lines 68 and 14 led into the catalyst cooler 11. One with a valve Line 69 is used to supply water from the outside into the system.

At least a portion of the overhead product from the absorber 56, the Contains hydrocarbons including propylene is through line 60 in the propylene feed line 21 is returned. Part of the line 60 total circulated gas stream can, for. B. by indirect heat exchange with the gases flowing out of the reactor through line 46. A portion of the overhead product from the absorber 56 can be removed from the system through the line 61 provided with a valve can be tapped.

Paraffinic hydrocarbons, such as propane, can be of the olefinic Hydrocarbon feed can be added. That way is the procedure of the invention with advantage on the conversion of propylene in industrial accruing propane-propylene fractions to Aerolein applicable.

In addition to propylene, olefins higher than propylene can also be used in the corresponding a, ß-unsaturated aldehydes and ketones are converted. For example, isobutylene be converted into methacrolein.

In a variant of the method of the invention, at least one Part of the catalyst leaving the reactor 15 passed through a regeneration zone before it is returned to the catalyst cooling chamber 11. The catalyst regeneration zone can consist of a chamber which is provided with the usual facilities in order to to keep the catalytic converter in a fluidized state. In the I ', generation zone can the catalyst for removing carbon deposits with oxygen and / or Steam treated.

The invention is further illustrated by the example below.

Example Aerolein is made by the oxidation of propylene with molecular Oxygen in the presence of a bismuth molybdate catalyst in a 24.4 m long, vertical reactor manufactured with an internal diameter of 71.3 cm; which is arranged above a catalyst cooling container, as shown in the drawing emerges.

The catalyst chamber 11, in which there is a bed of bismuth molybdate is on silica as a support catalyst and the with this connected vertically standing reactor 15 are by passing hot Blast furnace gas preheated to a temperature of about 420 ° C. Then there is oxygen 950 / ciger purity introduced into the lower part of the chamber 11 and upwards passed through the catalyst bed. Water at least partially from the system originates, is introduced into the chamber 11 and evaporated. The oxygen, steam and gas stream containing entrained catalyst leaves the catalyst bed in the chamber 11 and rises upwards through the vertical reactor 15, which is arranged above the catalyst chamber 11. Propylene and in the system im Recycled propylene-containing gas is fed into the lower part of the reactor 15 introduced and upwards' through the reactor in cocurrent with the steam, Oxygen and the entrained catalyst passed from the catalyst chamber 11 exits, and introduced into the cyclone 23. This is where the catalyst is from the separated gaseous components. Quenching water is introduced into cyclone 23, to reduce the temperature of the products coming out of the reactor to about 290 ° C. The hot catalyst separated in the Zy-Idon 23 is transferred to the catalyst chamber 11 directed. Most of the catalyst flowing out of the reactor has been freed from it Products are used to condense most of the steam in an indirect The heat exchanger is cooled and the aqueous, practically the resulting form all slurry containing remaining entrained catalyst into the catalyst chamber 11 returned. That after separating off the catalyst and most of it of the water remaining behind, coming from the reactor, is then treated worked up to the desired product.

The reaction mixture rising up into the vertical reactor 15 contains about 7.5 mole percent oxygen, about 21.5 mole percent propylene and about 38 mole percent steam. The rest consists essentially of nitrogen, carbon monoxide and carbon dioxide. The reactor 15 is maintained at a temperature of about 435 ° C. The pressure in the reactor 15 and in the catalyst chamber 11 is adjusted to about 6.3 kg / cm =. Additional amounts of oxygen are introduced into reactor 15 at a plurality of locations along its length. The additional oxygen fed to the reactor in this manner corresponds to about 70 mole percent of the total olefin feed fed to the reactor. The reaction mixture is through the reactor 15 at a flow rate of about 6 to 8 m / sec. guided. The catalyst is circulating in the system in an amount of about 40 to 45 kg / sec.

The reaction temperature is maintained by introducing water into the catalyst chamber 11 and by cooling the reactor walls with water. The steam generated when the reactor walls are cooled with water is used in part for stripping off the catalyst which emerges from the cyclone 23 into the chamber 11. A further part of this steam is optionally introduced into the lower part of the chamber 11 in order to assist in maintaining the desired reaction conditions. The rate of feed of the reactants and water into the system is controlled so that the catalyst in chamber 11 remains fluidized and suspended as it passes through reactor 15 during the oxidation reaction.

In the facilities for obtaining the products, those from the catalyst and from most of the water, gases or gases coming out of the reactor Vapors washed with water and aerolein washed out here. Aerolein is off distilled off the aqueous washing solution. The remaining gas after washing is fed back to the inlet of the reactor 15. Aerolein is obtained in one yield of about 71% with about 91% oxygen conversion and propylene conversion of about 50%.

Claims (4)

PATENT CLAIMS: 1. Process for the production of α, ß-unsaturated aldehydes and ketones by partial oxidation of olefins with at least 3 carbon atoms in the molecule in the vapor phase by means of a gas mixture containing free oxygen in the presence of water vapor at elevated temperature and under the influence of a heavy metal-containing oxidation catalyst according to patent application S 71080 IV b / 12 o, the reaction being carried out according to the dust flow process in such a way that the olefin is added to a previously formed suspension of the catalyst in a gas containing free oxygen and the mixture obtained by an externally cooled tubular reaction zone of smaller cross-sectional area than the catalyst cooling zone, which is maintained at a temperature between about 350 and about 750 ° C, keeping the catalyst in suspended form during its passage through the reaction zone, a free oxygen-containing gas into the reaction zone introduces at several points along its length, separates the catalyst from the vaporous mixture emerging from the reaction zone and leads into a cooling zone which is in open communication with the reaction zone, a gas containing free oxygen passes through the catalyst located in the cooling zone, whereby catalyst particles are entrained and the suspension of the catalyst is formed, characterized in that water is also introduced into the catalyst cooling zone. 2. The method according to claim 1, characterized in that that one introduces an aqueous catalyst slurry into the cooling zone, which also still contains small amounts of reaction products and that from the reaction zone emerging, cooled by indirect heat exchange reaction mixture separated has been. 3. The method according to claim 1, characterized in that one in the The cooling zone introduces at least part of the aqueous solution obtained by the unsaturated aldehydes and ketones emerging from the reaction zone have been separated by washing with water and the dissolved aldehydes and ketones were distilled off from the aqueous washing solution. 4. The method of claim 1 to 3, characterized in that a catalyst is introduced into the catalyst cooling zone conducts, which is generated with steam, which was preferably generated within the system, has been stripped. In. References Considered: United States Patent Specification No. 2451485; Luxembourg Patent No. 36,201.