JPS5932447B2 - Method for producing olefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a corresponding aliphatic olefin by catalytically dehydrogenating an aliphatic hydrocarbon having 3 to 5 carbon atoms (paraffin).

More specifically, gaseous propane, n-butane, isobutene, pentane, etc. are dehydrogenated by contacting them with an alumina/chromia dehydrogenation catalyst in a fluidized bed method to produce the corresponding propene, n-butene/isobutene, pentene, etc. It relates to a manufacturing method. Olefins having 3 to 5 carbon atoms have conventionally been produced mainly as by-products of ethylene production plants or catalytic cracking gasoline production plants using naphtha as a raw material, and have been in excess until now.

However, recently, the demand for these olefins has increased, and the balance of these olefins is changing significantly. For example, isobutene, which is a raw material for methyl-tert-butyl ether and methyl methacrylate,
In addition, the demand for n-butene-1, which is a polyethylene modifier, is rapidly increasing. In addition, there is a significant shortage of butadiene and isoprene, and methods for producing butadiene and isoprene using n-butenes and isopentenes as raw materials are being considered. In order to respond to such changes in the balance, conventional co-production processes have limited production volumes, and it is desirable to develop a process that can efficiently produce only the desired olefin, and much research has been conducted on this topic. It's here. For example, various studies have been conducted on methods for producing olefins by catalytic dehydrogenation of lower paraffins, and numerous papers and patents are known.

Some of them have shown fairly good reaction results. However, in order to make these methods excellent industrial processes, it is necessary to have high reaction rate and selectivity, but in addition, there are also methods for replenishing the reaction heat, methods for regenerating the catalyst, and methods for regenerating the reactor. It is also necessary to solve problems such as materials. The Foodry process and the UOP process are known as typical industrial processes for producing olefins by dehydrogenating lower paraffins. The Foudrey process sequentially performs a dehydrogenation reaction in a fixed bed reactor filled with a catalyst, passing a raw material gas through it, purging with an inert gas, regenerating and heating the catalyst with air, and purging with an inert gas. This method replenishes the reaction heat by accumulating the combustion heat of carbon deposited and accumulated on the catalyst in the catalyst, so the reaction occurs intermittently, the switching time is short, and the operation is complicated. However, it has the disadvantage that the composition of the produced gas fluctuates. In addition, the UOP method uses a moving bed catalyst system, which allows dehydrogenation reaction and catalyst regeneration to be carried out continuously, and has the advantage of obtaining a product gas with a constant composition. It is necessary to carry out multiple stages, and skeletal isomerization of raw materials or products - e.g. n-butane←
→There is a problem that isobutane is easily generated. A fluidized bed reaction is a method for carrying out the dehydrogenation reaction and the regeneration of the catalyst continuously and efficiently replenishing the reaction heat.

Typical examples include Japanese Patent Publication No. 49-14721 and Soviet Patent No. 759119. The former concerns the structure of the dehydrogenation reactor, in which heated solid particles
This invention involves indirectly heating the reaction system and catalyst to supply heat to advance the dehydrogenation reaction. In addition, the latter method replenishes new catalyst according to the activity of the used catalyst according to instructions from the calculation unit to keep the activity of the catalyst in the reaction system constant. It is circulated through the elementary reactor. However, in the methods for producing olefins by catalytic dehydrogenation of paraffins in the fluidized bed method, as typified by these methods, the dehydrogenation reaction and the regeneration of the catalyst are carried out continuously, so a product gas of a constant composition is obtained. The reaction heat is efficiently and smoothly replenished, and the conversion rate and selectivity are both high, making it a mature technology for paraffin dehydrogenation.

However, it goes without saying that if both the reaction rate and selectivity can be further increased, olefins can be obtained industrially more advantageously. The present inventors have conducted intensive research to provide a process for selectively and efficiently producing the corresponding olefins using a fluidized bed method from paraffins with carbon numbers of 3 to 5, which are still abundant in resources. We have obtained new knowledge that both the reaction rate and selectivity can be increased by bringing the catalyst into contact with hydrogen gas or hydrogen-containing gas prior to use in elementary reactions, and based on this new knowledge, we have developed the present invention. Reached. That is, the present invention provides a method for producing a corresponding olefin by catalytically dehydrogenating a paraffin having 3 to 5 carbon atoms in a fluidized bed method using an alumina/chromia dehydrogenation catalyst.
A catalyst pretreatment step in which the catalyst is brought into contact with hydrogen gas or a hydrogen-containing gas, a paraffin dehydrogenation step, and a catalyst regeneration step in which the used catalyst is brought into contact with oxygen gas or an oxygen-containing gas are sequentially used. This is a method for producing an olefin. The raw material used in the present invention may be any paraffin having 3 to 5 carbon atoms, and specific examples thereof include propane, n-butane, isobutane, n-pentane, and isopentane, and the target olefins are these paraffins. Mono-olefins and diolefins corresponding to It is. The catalyst used in the present invention is an alumina-chromia dehydrogenation catalyst that is known per se.

The composition of an alumina/chromia dehydrogenation catalyst is generally 5 to 30 wt% of chromia (Cr2O3), with the balance being alumina (Al2O3). In addition, it may contain 0.3 to 10 wt% of alkali metals such as potassium and sodium and alkaline earth metals such as magnesium as oxides. The catalyst may be prepared by any method, such as a coprecipitation method, a supporting method, and a spray drying method. The prepared catalyst usually has an average particle size (by sieving method; the same applies hereinafter) of 2.
It ranges from 0 to 300 microns, with 30 to 200 microns being preferred. It is also necessary to have the strength to withstand long-term fluid circulation. As a representative example of a commercially available alumina/chromia catalyst used in the present invention, for example, 6Cr-1404p (Harsha
(manufactured by W company).

The hydrogen-containing gas used in the catalyst pretreatment step in the present invention is a mixed gas of hydrogen and, for example, hydrogen, methane, and/or ethane.

As for the treatment conditions in this catalyst pretreatment step, the temperature is usually 520 to 640 degrees Celsius, preferably 560 to 600 degrees Celsius, and the pressure is usually substantially normal pressure without any need to increase or reduce the pressure. , it is possible to reduce the pressure to about 0.5 to 2 atmospheres or to slightly increase the pressure. Conditions in the paraffin dehydrogenation step and catalyst regeneration step in the present invention are those that are known per se.

In other words, the conditions in the paraffin dehydrogenation step are as follows:
The temperature is 520 to 64°C, preferably 540 to 620°C, and the pressure is usually substantially normal pressure without any need to increase or reduce the pressure, but it can be reduced to about 0.5 to 2 atm. It can also be pressurized. Further, the feed rate of the raw material paraffin is 200 to 10,001 per hour, preferably 300 to 8,001 per hour in gaseous state (NTP) per 11 retained catalysts. The oxygen-containing gas used in the catalyst regeneration process is a mixed gas of oxygen and, for example, nitrogen, water vapor, and/or carbon dioxide, and the oxygen content is, for example, 3 to 3.
It is about 0V01%.

Note that gas containing water vapor and carbon dioxide obtained by burning practical soil, hydrocarbons, etc. can be mixed. Air is usually used as oxygen-containing gas. The conditions of the catalyst regeneration process change depending on the conditions of the paraffin dehydrogenation process, so they cannot be absolutely limited, but the carbon that is produced as a by-product in the paraffin dehydrogenation process and has accumulated on the catalyst surface is substantially completely combusted. Any condition is sufficient as long as it can be removed; in practice, the temperature is usually 550 to 750°C, preferably 600 to 750°C.
00° C., and the oxygen supply rate is 10 to 100 liters per hour per 11 retained catalysts. In addition, the pressure usually does not need to be particularly increased or decreased and is substantially normal pressure, but 0.
There is no hindrance to reducing the pressure to about 5 to 2 atmospheres or slightly increasing the pressure. In the present invention, the amount of catalyst retained in each of the catalyst pretreatment step and catalyst regeneration step and the average residence time of the catalyst in the paraffin dehydrogenation step are also important factors.

In other words, the catalyst retention amount (volume) in the paraffin dehydrogenation process
The ratio of the amount of catalyst retained in the catalyst pretreatment step to (the same applies hereinafter) is 0.05 to 0.5, preferably 0.1 to 0.5. If the amount of catalyst retained in the catalyst pretreatment step is smaller than the above range, the effect of the pretreatment will be small, and if it is larger than the above range, there is a risk that the selectivity of the target olefin will decrease. The amount of catalyst retained in the catalyst regeneration step can be varied depending on the conditions in the paraffin dehydrogenation step, but is generally 0.2 to 3 of the amount of catalyst retained in the paraffin dehydrogenation step.
Double is appropriate. The average residence time of the catalyst in the paraffin dehydrogenation process is usually 0.3 to 5 hours. Preferably it is 0.3 to 3 hours. When reaction conditions are harsh,
For example, when the reaction temperature is high or the feed rate of raw materials is high, the average residence time of the catalyst may be made relatively short, and when the reaction conditions are mild, the average residence time of the catalyst may be made relatively long.

A flow sheet of a process for producing olefins according to the present invention is illustrated in FIG.

That is, the catalyst pretreatment device 1, the dehydrogenation reactor 2, and the catalyst regenerator 3 are connected in series.

Each of the catalyst pretreatment device 1, dehydrogenation reactor 2, and catalyst regenerator 3 is provided with a metal sintered plate 4, and above the metal sintered plate 4 is a catalyst retention section 5 in which the catalyst is fluidized. , 6 and 7. The catalyst pretreatment device 1 and the dehydrogenation reactor 2 are connected by a pipe 8, one end of the tube 8 is connected to the catalyst retention section 5 of the catalyst pretreatment device 1, and the other end of the pipe 8 is connected to the dehydrogenation reactor 2. Each of the catalyst retention portions 6 is opened therein. The dehydrogenation reactor 2 and the catalyst regenerator 3 are connected by a pipe 9, one end of the pipe 9 is connected to the catalyst retention section 6 of the dehydrogenation reactor 2, and the other end of the pipe 9 is connected to the catalyst of the catalyst regenerator 3. Each of them opens into the retention section 7. The catalyst regenerator 3 and the catalyst pretreatment device 1 are connected to the pipe 10.
One end of the tube 10 opens into the catalyst retention section 7 of the catalyst regenerator 3, and the other end of the tube 10 opens into the catalyst retention section 5 of the catalyst pretreatment device 1. Therefore, the respective volumes of the catalyst retention sections 5, 6 and 7 of the catalyst pretreatment device 1, dehydrogenation reactor 2 and catalyst regenerator 3 are the same as those of the tubes 8, 9.
and 10 by adjusting the position of each open end. Pipes 11 and 12 are provided at the lower and upper parts of the catalyst pretreatment device 1, respectively, with the pipe 11 serving as a hydrogen-containing gas inlet and the pipe 12 serving as a gas outlet. A pipe 13 and a pipe 14 are provided at the lower and upper parts of the dehydrogenation reactor 2, respectively, with the pipe 13 serving as a source gas inlet and the pipe 14 serving as a product gas outlet. Pipes 15 and 16 are provided at the lower and upper portions of the catalyst regenerator 3, respectively, with the pipe 15 serving as an oxygen-containing gas inlet and the pipe 16 serving as a gas outlet. New catalyst is supplied from a branch pipe 17 provided in the pipe 10 as necessary. The catalyst from tube 10 is contacted with hydrogen and pretreated in catalyst pretreater 1.

The pretreated catalyst reaches the dehydrogenation reactor 2 through the pipe 7 and participates in the dehydrogenation reaction. The catalyst from dehydrogenation reactor 2 is in tube 9
The catalyst passes through the catalyst regenerator 3, where it is brought into contact with oxygen and regenerated. This regenerated catalyst is sent to the catalyst pretreatment device 1 via a pipe 10 either alone or together with fresh catalyst supplied from a branch pipe 17 as required. FIG. 1 shows only one concept such as the circulation order of the catalyst or the method of supplying raw material and sub-material gas, and does not specify the structure, size, etc. of the apparatus.

That is, the dehydrogenation reactor, catalyst pretreatment device, and catalyst regenerator can take various shapes such as vertical ones and flat ones,
The raw material gas, auxiliary raw material gas, and catalyst may be supplied in various ways. In addition, replenishment of reaction heat during dehydrogenation reaction and heat removal during catalyst regeneration can be done using only a heat exchanger installed outside the catalyst retention area if the device is small, but if the device is large, A heat exchanger may also be installed within the catalyst retention section if necessary. According to the present invention, a product with a constant composition can be stably obtained, reaction heat can be efficiently and smoothly replenished, and olefin can be efficiently produced with a higher conversion rate and selectivity than before. The industrial value of Honkoku Shumei is extremely high.

The present invention will be explained in more detail with reference to examples.) Zero-poor Example 1 Catalyst used: In this example, a catalyst prepared by the following method was used.

That is, chromium acetate 446y1 magnesium acetate 19
57 and potassium acetate 777 were added to 1.251 of water and dissolved by heating.

To this aqueous solution, 1.0% of powdered alumina obtained by the dung fog drying method was added.
k9 (1600ml) was added and mixed. The above mixture was evaporated to dryness under reduced pressure in a rotary evaporator (inner volume: 101) with a bath temperature of 80°C. The obtained cake-like dried product was heated and baked in an electric furnace at 200°C for 4 hours, at 400°C for 4 hours, and at 700°C for 10 hours in a stream of air. After cooling down, sieve and 350 mesh (Japanese Industrial Standard J)
According to ISZ88Ol. (Similarly below) Fine powder from the bath and lumps from the 100 mesh stop were removed to prepare a dehydrogenation catalyst. The average particle size of the resulting catalyst was 61 microns;
The composition is Al2O382%, Cr2O3l2%, MgO,
3%, and K2O 3%. ω Experimental equipment: 1st
The process shown in the figure was used. The following containers were used in this process: Catalyst pretreatment device 1.5 inch φXl. OmH, catalyst retention amount 100m1 dehydrogenation reactor 2.0 inch φ x 2.0mH, catalyst retention amount 4
00ml Catalyst regenerator 2.0 inches φ x 2.0mH 1 Catalyst retention amount 400ml D Manufacturing conditions: The operating conditions for each step were set as follows, and the dehydrogenation reaction from isobutane to isobutene was carried out for a total of 10 hours.

Operating conditions Note that in each step, no particular pressure was applied or reduced.

We successively analyzed the flow rate and composition of the hydrogen produced from the dehydrogenation reactor.
Response performance was tracked.

Four hours after the start of the reaction, the reaction reached a steady state, and thereafter the value remained constant. The conversion rate of isobutane 10 hours after the start of the reaction was 40.6%, and the yield of isobutene was 38%.
7% and isobutene selectivity was 95.3%.
Comparative Example 1 Isobutene was produced in the same manner as in Example 1, except that the catalyst pretreatment device was omitted and the catalyst exiting the catalyst regenerator was directly circulated to the dehydrogenation reactor.

The reaction rate of isobutane 8 hours after the start of the experiment was 37.4%.
, iso5-butene yield was 33.8%, and isobutene selectivity was 90.5%. Example 2 Isobutene was produced in the same manner as in Example 1, except that the operating conditions in each step were set as shown below.

O operating conditions 6 hours after the reaction reached steady state,
The reaction rate of isobutane is 52.5%, and the isobutene yield is 4
7.6%, and the isobutene selectivity was 90.7%.

Example 3 According to the method described in Example 15, the composition was 87% Al2O3, 2% Cr2O3l and K2Oll.
% and an average particle size of 57 microns.

Using this catalyst, propene was produced from propane under the following operating conditions. The manufacturing conditions using the same apparatus as in Example 1 were the same as in Example 1 except that the operating conditions for each step were set as follows. Operating Conditions The reaction reached steady state 3 hours after the start of the experiment.

Six hours after the start of the experiment, the propane reaction rate was 42.
The yield of propene was 35.4%, and the selectivity of propene was 83.8%.

[Brief explanation of the drawing]

FIG. 1 is an example of a flow sheet of a process for producing olefins according to the present invention.

Claims (1)

[Claims] 1. A method for producing a corresponding olefin by catalytically dehydrogenating paraffins having 3 to 5 carbon atoms in a fluidized bed method using an alumina/chromia dehydrogenation catalyst, in which the catalyst is
A catalyst pretreatment step in which the catalyst is brought into contact with hydrogen gas or a hydrogen-containing gas, a paraffin dehydrogenation step, and a catalyst regeneration step in which the used catalyst is brought into contact with oxygen gas or an oxygen-containing gas are sequentially used. A method for producing an olefin.