DE1291734B - Process for the catalytic dehydrogenation of gaseous hydrocarbons - Google Patents

Description

1 2

The invention relates to a method for which conversion operating points work and catalytic dehydrogenation of gaseous carbons - this results in an uneven product distribution in particular for the production of Butalung results. This can lead to a loss of product in which in several, in temporal successive capacities lead and to a reduced subsequent reactors with fixed catalyst 5 lifetime of the catalysts, bed periodic hydrocarbon dehydrations, in a process for adjusting the water

Catalyst regeneration by means of a preheated amount of steam in air during the regeneration of a Air flow and in between cleaning for the de-catalyst, it is also already known that the removal of unwanted gases. Regenerating air through indirect Systems with which such processes can be heated through to heat exchange and then carried out are the desired final temperature for the production of butadiene by burning knows. These systems can self-heat three or more reactant coke oven gas in the air. Of the Have gates that are arranged in groups in such a way that the water vapor content in the heated gas is thereby and are connected to one another in such a way that they differ from 0.95 percent by volume to about 1.4 to 1.5 volume percentages Reactors can be “in the flow” at the same time. This is the result of burning d. H. in the reaction period, and that the coke oven gas is in the air, different other reactors at this time in the With this process it is not possible, however,

Regeneration phase are located and that finally the temperature remaining during regeneration Reactors or the remaining door, which fluctuates only within a few degrees, aufaktor is at any stage of a purification phase. ao right if it is in plants in which In general, the cyclical time control takes place several reactors, which are more or more such that if any particular group is separated from less roughly in a particular time sequence Reactors work in the same way, not all reactors are used industrially, gates of this group in the same operating state The temperature profile in large catalytic converters are. In some reactors, the operating state has 25 beds is undulating. The temperatures in these just started, in others it has just ended. Beds are therefore unequal and variable in time. the been or about to graduate. Temperature waves don't just run in one direction

The invention is primarily concerned with that of the gas flow, but also in the reaction area. Regeneration period of the cycle in which the reac- The oxidative regeneration of the catalyst by gates that were cleaned after their "in the stream" period 30 burning of coke generated temperature fluctuations, with a considerable amount of rain that does not allow the temperatures in the tion air are charged, the catalyst bed consistently or uniformly in a known manner has been preheated, for example by behavior. If it is also theoretically possible burning of heating gas in a duct heater. like, a constant tem path in a catalyst bed to maintain the extremely large dimensions 35 temperature, for example by the fact that a the process equipment and the extraordinarily large amount of heating gas is sent through the bed, borrowed large amount of air in the regeneration- so this would consume a very large amount of gas cycle is consumed, the pipelines are for conditions that would be uneconomical. Indeed it will the air supply, the distribution heads for the air and so far not the desired result in practice the individual lines received from the distribution heads 40.

lead to the various reactors, from behaving- According to the teaching of the invention, the tendency is

very large dimensions. For reasons that the mean bed temperatures of any the use of space and the economy is or more of the reactors in which the Regeneraes It is common practice to place the various boilers and tion below a desired optimum height the devices assigned to them are noticeable, counteracted by the fact that for compensation to be arranged differently so that intermediate lines, excess temperature differences within the den ducts and other auxiliary devices are fed to the shortest individual reactors for regeneration possible length. In the case of the air currents in front or the underlooked persons caused by them Pipes and distributor heads with large differences in the mean catalyst temperature, measurements and with the relatively short connection 50 controlled amounts of a gaseous fuel and supply lines and high air flows into the cooler portions of the reactors It is difficult to introduce large temperature differences of the flowing air currents and of the upper air currents burned in the heater or the heater to the surface of the respective catalyst bed avoid. The result is a laminar flow becoming hotter, whereby the quantities of gas to be supplied and cold air. The reactors can therefore each have under-shaped fuel in accordance with the different amounts of air of different Tem- temperature conditions in the catalyst bed in such a way temperature preserved. For example, some reac- tions can be regulated so that one without a catalyst works a larger amount of regeneration air forms a combustible fuel-air mixture, obtained high temperature, while others low- The addition of fuel gas according to the teaching of the

Get more amounts of air at a lower temperature. 60 invention leads to an increase in temperature Temperature measurements in the different flow of the catalyst bed, which in turn have a larger one proportions of the regeneration air have shown that yield of butadiene causes. An addition of temperature differences of the order of magnitude 0.30 percent by volume methane to the regeneration of For example, 100 ° C inside the air distribution heads results in a doubling of the air can. 65 Butadiene production (13 percent by weight) in the

The resulting differences in the same to a process in which no fuel medium Bed temperature of the various reactors gas was added to the regeneration air with have the consequence that the reactors produce only 7.1 percent by weight of butadiene with different

could. This distinct advantage is used by the duct heater for preheating the re-

accompanied by a slight loss of selectivity, the generation air and the steam generation source do not

however, in view of the increased yield of the shown. It is sufficient to state here that the

desired substance is irrelevant. A hydrocarbon feed to the reactors, for example

also occurring increase in coke formation 5 is fed at 640 ° C, and that the regenerative

means an additional benefit. This coke is converted into the air duct heater to a temperature

burns by the air supplied in excess temperature of 610 to 700 ° C is preheated. In each

again and thereby enables a certain intake of the main inlet lines 9, 10 and 11 are blocking

saving of energy needed to heat the air in valves,

otherwise the air lines would have to be expended. to a second and smaller inlet line 12 leads

In addition, the coke formation is not at the expense of the side to the inlet head 6.

of the desired product takes place, such as the strong management of smaller amounts of methane or natural

shows increased yield. gas to control the bed temperature within the

In a preferred embodiment of the invention reactors 5 during the regeneration cycle. to

The gaseous fuel is a hydrocarbon fuel

substance, especially methane or a natural gas or a steam and the hydrocarbon in the pipeline

Mixing of one or more combustible compounds 11 and 10 control, closed while the

components of a refinery gas. The refinery gas is released from the valve that controls the air flow in line 9,

usually holds as combustible components C ₁ -C ₄ - is open.

Hydrocarbons, carbon monoxide and water - so. In the natural gas inlet line 12 there is a valve 13

material. for flow control, behind which a throttle valve

The supply of fuel is carried out individually by means of or a fixed throttle 14 and a shut-off valve conventional control means controlled so that the bed 15. As a safety measure can be in the line temperatures of different reactors are within 12 between the valves 14 and 15 an overpressure limits. The amount of gas delivery 25 should be provided.

Mild fuel, that of any air supply line That line 12 leads in the illustrated excerpt is, is generally well below the guide example leads directly to the inlet head 6, 5 percent by volume, measured at normal temperatures, is not essential for the invention. For example and well below 1 percent by volume, measured at can the pipe at any convenient location the temperatures generally found in the rain of the steam or air inlet ducts downstream ration air duct prevail. from their valves for the flow control

Further details of the invention can be concluded. If desired, an inert

from the following description of an execution diluent gas are added to the natural gas,

example with reference to the figures. This can be in the natural gas line 12 at any one

F i g. 1 shows a schematic view of a suitable place to be introduced so that it

location with several reactors for the conversion of continuously with the natural gas to the inlet head 6

Hydrocarbons, such as those used for the dehydrogenation of flows. Inert gas can also be used for cleaning

Butane to be used for the production of butadiene.

dung of the well-known cyclic adiabetic fixed- To prove the usefulness of the invention,

bed procedure; 40 were with a dehydration plant, which the pro

F i g. 2 shows a view of one of the butadiene reacted, test runs made. the

gates according to Fig. 1. It is a reactor system had eight reactors. Everyone had one

gate of the horizontal cylindrical type. This type of fixed bed made of granulated chromium aluminum catalytic

of reactors is not specific to the invention, sator. The system was controlled by suitable

however, especially for the implementation of the invention, it is set in such a way that each time

suitable according to the procedure. three reactors were running in the regeneration cycle, each

The horizontal cylindrical reactors 5 are not all three worked in unison. Select

essentially of the same construction and therefore a reactor in the middle of the regenerative *

■ arranged in a single row. The number the tion cycle worked on had someone else just come up with

Reactors can begin between three and ten or more of the regeneration, and the third was

lie beyond. Five to eight reactors have just completed the regeneration,

proved to be particularly suitable for most purposes. On different days, however, for example under the

proven. same environmental conditions, were 8 hours

Each of the cylindrical reactors 5 is with a test run while feeding natural gas to one

Inlet head 6, which has several inlets, is made of the reactors. Bed temperature data was

see lying on its upper side. Furthermore, the before and during the test runs are determined, and

Air and fuel gas outlet lines 7 and coal, although in front of locations across the upper part, the middle

hydrogen and steam outlet lines 8 at his and the bottom of the bed. The reactors were

Bottom connected. those with a regeneration cycle of about 8 to

The inlet head 6 is operated for connection of three 60 9 minutes. The natural gas was during

Main lines set up, namely for a z- a 6-minute middle

central inlet line 9 for introducing preheated cuts of each cycle,

ter regeneration air, for a side inlet line The supply of all regeneration air to the

10 for the supply of the hydrocarbon feed system was carried out in an amount of about

Stream and for a further lateral inlet line 11 65 5 950 000 l / min, under normal conditions. Since each

for cleaning fumes. For reasons of simplicity, there are three reactors at the same time during regeneration

Representation are those not belonging to the invention, so was the amount of air flow to each

ovens to preheat the butane feed stream, a reactor about 1980,000 l / min. The reactor

following work steps of the reactors of the plant. More important is the productivity of the plant is lowered and its service life is determined by the catalysts of the hot reactors, 5 so that overall the catalysts are used uneconomically.

Although the temperature setting in the various reactors is primarily due to the temperature differences must take place between the

No. 1 of the eight-reactor plant was used for the experiments.

On the first attempt, the reactor was natural gas
in an amount of about 2630 l / min, supplied, and
although in an amount of 0.133 percent by volume
Regeneration air. It was observed that the
Temperature of the bed around 1.5 ° C at different
Cycles and around 1 ° C at various others
Cycles increased and then remained at the same level for the remainder of the respective experiment. With 100 regeneration air currents, which at the same time as the amount of fuel introduced, the three reactors to be regenerated could enter, the bed temperature rose by about 8 ° C - it is known that temperature differences are generated. also see through the various beds. In the second test, natural gas was used in an amount with slight differences in the loading of the catalyst from about 3820 l / min. supplied, corresponding to 15 sator beds due to differences in activation 0.193 percent by volume of the air. With this supply of the catalysts and due to differences in the natural gas, a rise in the temperature of the hydrocarbon bed resulted,
of about 11 ° C. As those referring to hydrocarbons. Even if the specified temperature increase data, in particular the volume throughput, but do not match the calculated, available heat ao also the catalyst activity and the aggregate increase due to the introduced fuel setting of the total charge are variables that agree, they are due to the heat - do not influence the plant or only slightly or explain the equilibrium setting, since at can control, the temperature control after higher temperatures changes the conversion rate of the invention is an important means to achieve optimal and accordingly also the production of the working conditions,
coking products. From the description of a further embodiment, from the specified bed temperatures, the method according to the invention was exemplified by the experiments to determine the effects of the advantage achieved by the invention Parts of the beds found that the 30 only increase at three of the total of four completely run-through bed temperatures in a fairly uniform manner in the cycles of hydrocarbon dehydrogenation of the whole bed, with the temperature measured in higher and catalyst regeneration in lower proportions of lower areas being slightly higher in gaseous form Fuel is the soil temperature during regeneration. A subsequent phase is added, as is seen according to the invention, a preliminary examination of the interior of the reactor after a complete inspection. In the fourth cycle carried out, it was found that there was no damage to the no gaseous fuel was supplied.
Bremigaseinleitungstelle the inlet head 6 on- The embodiment is used for the production of goods. From this one could conclude that butadiene was made from a mixture of 64% η-butane and that there was no flame front on the contact surface of 36% butylenes. As a fixed-bed catalyst, the incoming gas and the air stream are used to form 40 of the usual granulated chromium oxide (18%) on one. It could also be concluded that the aluminum oxide pad was used. The depth of the ignition of the natural gas only when it comes into contact with the catalyst bed is 89 cm. Inside the bed of the catalyst bed and when passing through are at intervals of about 13 cm along the sink this bed had occurred. The advantages of the method 45 according to the invention during the hydrocarbon dehydrogenation phase become clear when one considers the problems of measuring the temperatures in the various bed depths which arise when a temperature control is desired. The bed depth corresponds to the vertical in the individual reactors of the plant, the distance from the surface of the bed, ie from the resulting. Although, in general, suitable first contact area is available between the regeneration air directions that allow the regeneration air and the catalyst. After every complete supply of heat to the system, the butadiene production and the selectivity increased, so there was still the problem,
to carry out an additional amount of heat to be supplied to the individual reactors in individual adaptation according to their needs. The Invention 55
solved this extremely difficult problem,

by specifying means of distributing additional amounts of heat among the various reactors, which lead to an even temperature distribution among the various reactors. 60

Cold reactors are generally not as productive like hot reactors, so the catalysts in the cold reactors with one another Speed as the hot reactors age. air

The resulting differences in production 65 loading

output of the hot and cold reactors is volume percent CH ₄
require the use of different flow rates in regeneration quantities and compositions in the air on top of one another

and investigated the coke attack.

In the exemplary embodiment, methane is used as the gaseous fuel.

The three cycles performed with the addition of methane to the regeneration air were as follows Regeneration conditions set:

Inlet temperature

( ⁰ C)

pressure

Cycle 1

580

Cycle 2

580

Cycle 3

580

1 atmosphere absolutely

6.9

0.27

7.0

0.16

7.0

0.30

7 8

The hydrocarbon dehydrogenation conditions in the same cycles were as follows:

cycle

Cycle 2

Cycle 3

Inlet temperature ( ⁰ Q

Pressure (mm Hg abs)

Volume velocity (liquid)

580
152
2.9

580
127
2.9

580
127
2.9

The following bed temperatures were measured in the different bed depths on the center line (in ⁰ C):

Bed depth (cm) Cycle 1 Beginning end Cycle 2 Beginning end Cycle 3 end 580 580 582 580 Beginning | 580 0 593 580 593 574 585 577 12.5 588 582 582 580 607 585 25th 596 580 585 580 602 590 38 593 582 582 577 610 590 50 593 580 582 577 610 593 63 593 582 582 577 613 590 76 596 588 582 577 613 602 89 616

The addition of small proportions of gaseous fuel to the regeneration air has the effect a significant increase in the catalyst bed temperature. The result of the combustion of the fuel gas generated heat is fairly evenly distributed over the whole bed.

In cycle 4, where the conditions during regeneration and during hydrocarbon dehydration fully corresponded to the conditions set in cycle 1, but in which No gaseous fuel was added to the regeneration air, the bed temperatures were as follows (° C) measured in the different bed depths:

40

45

Bed depth (cm) Beginning end 0 580 577 12.5 580 574 25th 577 568 38 577 566 50 568 563 63 568 563 76 566 563 89 566 563

50

The temperature in the catalyst bed therefore increases in this one which operates without the teaching according to the invention Procedure ongoing.

Like the comparison of the butadiene yield from the three working with the addition of methane Cycles and the cycle that works without the addition of methane to the regeneration air has an effect the higher catalyst bed temperature has an extremely advantageous effect on the yield. In the three with an addition cycles operating from methane to regeneration air were 9.8, 9.1 and 13.0 weight percent, respectively Butadiene formed. In contrast, the butadiene yield in cycle 4 was only 7.1 percent by weight. Adding 0.30 percent by volume of methane to the regeneration air, for example, practically adds a doubling of the butadiene production (cycle 3 = 13 weight percent) compared to cycle 4, in which no fuel gas was added to the regeneration air.

In addition, there is a slight advantageous increase in coke formation: in cycles 1, 2 and 3, respectively 0.7, 0.7 and 2.2 percent by weight of coke formed, while in the 4th cycle only 0.2 percent by weight of coke arises. The coke burns again due to the excess air supplied; increased coke formation thus enables energy savings. In addition, the coke formation is not at the expense of desired product takes place, as the sharp increase in butadiene yield shows.

The slight decrease in selectivity - the selectivity in cycles 1, 2 and 3 is 67.3, 70.4 and 64.2 percent by weight versus a selectivity of 71.3 percent by weight in cycle 4 - does not play a role, especially in view of the significantly increased production yield.

Claims (3)

Patent claims: 1. Process for the catalytic dehydrogenation of gaseous hydrocarbons, in particular for the production of butadiene, in which several, working in chronological order Fixed catalyst bed reactors, periodic hydrocarbon dehydrogenation, catalyst regeneration carried out by means of a preheated air stream and in between cleaning to remove unwanted gases are, characterized in that to compensate for temperature differences within the air flows fed to the individual reactors for regeneration or the air flows through them caused differences in the mean catalyst temperature controlled amounts of a gaseous fuel in the cooler parts of the air flows flowing into the reactors introduced and burned on the surface of the respective catalyst bed, where- 909 514/1603 with the quantities of the gaseous fuel to be supplied in accordance with the temperature conditions are regulated in the catalyst bed in such a way that an incombustible without a catalyst Forms fuel-air mixture. 2. The method according to claim 1, characterized in that the fuel in the air electricity is introduced in an amount exceeding 1 percent by volume of the regeneration air. 3. The method according to claim 1 or 2, characterized in that the fuel is a hydrocarbon, especially methane or a natural gas' or a mixture of one or more combustible components of a refinery gas. 1 sheet of drawings