DE1593372C - Process for the preparation of diols or vinylbenzenes by catalytic dehydrogenation of monoolefins or of mono or diethylbenzene - Google Patents

Description

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The process of the reactor outer wall generally used up to now is practically at all

for the production of z. B. styrene or butadiene through not flowed through by the reactants catalytic dehydrogenation (both of which become highly endothermic.

Reactions) consists in the fact that the initial In contrast to the low pressure dehydrated hydrocarbon, such as monoolefins with 4 to 5 carbon atoms with self-regenerating catalysts or mono- or diethylbenzene, other catalytic conversions are achieved with th methods a suitable temperature heated water vapor lungs of hydrocarbons, especially the cavemixed and through the analytical reforming on platinum catalysts in a suitable fixed bed located catalyst conducts. Then the carrier materials, which are at significantly above the atmospheric reaction product mixture quenched, to un- io spherical pressure lying, z. B. 6.8 to desired secondary or subsequent reactions, such as The 47.6 atmospheres, usually To suppress polymerization of the product. In the all- carried out by generalizing the starting material Then the water vapor becomes, together with hydrogen, through a ring-shaped catastrophe above the temperature of the heated carbon catalyst bed from the periphery to a central one hydrogen starting material lying temperature 15 arranged axial manifold leads out. One of those heated. Then the two streams are immediate, the type of reactor is usually a radial reactor with a single-flow reactor when brought into contact with the catalyst, it is referred to as the downstream flow.

v / ground, mixed, thereby creating the one hand for the endo- · Surprisingly, it has been shown that the. pre-thermal dehydrogenation reaction necessary heat-related disadvantages by using a radial amount added and on the other hand, the time in which the 20 current reactor with special current management can be eliminated hydrocarbon undesirable, thermal reactions and is particularly subject to excellent selectivities, keep selectivities as low as possible leave,
(see U.S. Patents 2,414,816 and 3,118,006). The invention therefore relates to a process. These dehydrogenations are generally carried out in the presence of a self-regenerating catalyst containing iron oxide by catalytic dehydrogenation of monoolefins for the production of diolefins or vinylbenzenes. with 4 to 5 carbon atoms and one chain length

Although already appropriate procedures to; Manufacture of at least 4 carbon atoms or of mono of butadiene and styrene have been developed, or diethylbenzene, with the reaction temperatures constantly making new efforts to improve the heated mixture of the hydrocarbon starting process and thereby the production of cheap material with steam to shape in the presence of a self-confident. The aim of these efforts was, by and large, the production of effective cata- dehydrogenated catalysts containing iron oxide and the product then quenched and an improved utilization of the input, which is characterized in that the feed material, including the recovery, is not a mixture of starting hydrogen and water vapor converted hydrocarbons, which was again fed into the de-35 after a hydrogenation stage carried out in a manner known per se. It was also feed into a centrally arranged, axial effort to improve the bringing into contact of the input material and the direction of the catalyst extending and with axial recesses, in order on the one hand to provide the supply line of an annular catalyst by increasing the pressure drop across the catalyst bed radially through the annular To make the downtime caused by the catalyst bed as small as possible 40 flow and the product flow is withdrawn from its and on the other hand the heat input to the dehydrogenation peripheral surface,
zone, while maintaining the selectivity for the product preferably the linear entry rate is to make as high as possible. Flexibility in the annular catalyst bed 1.8 to thereafter should mean that the catalyst abrasion should be as small as 2.4 m / sec.

as possible to avoid the formation of ca 45 The following is the claimed method at

channels and bypass routes in the catalyst to which the starting material is fed in centrally, as

avoid. Radial flow method with central feed and

So you have, for example, for the dehydrogenation of the associated reactor as a radial flow reactor Butylenes to butadiene ring or radial reactors with central feed. The well-known recommended, in which the separate entrances 50, in which the feed of the starting material feed and product removal lines inside a line are made from the circumference and also with radial lines ring-shaped catalyst bed arranged flow guide works, is as radial flow, which to the outside of an effective heat drive with peripheral feed and the associated insulation is surrounded. In the feed line and in the reactor as a radial flow reactor with circumferential feeder Sampling lines are located diametrically opposite, while the method at overlying longitudinal slots or in the longitudinal direction to which the reaction participants in the axial direction ordered openings through which the treatment reactor flow as an axial flow process and well into the catalyst bed or through which the associated reactor is called an axial flow reactor converted reaction mixture from the catalyst is.

Sator bed flows off. In this way, the pressure should be 60 The advantages of the radial flow method with central

waste should be kept as small as possible. With a sol feed-in compared to the radial flow method

Chen embodiment, however, it is neither possible to use circumferential feed and / or the axial flow method.

the product stream after leaving the catalyst consist in a lower pressure drop, one

Quench bed, nor can the residence time in the longer life of the catalyst bed and a

equalize the required dimensions, thereby reducing the volume of the feed room,

which affects the selectivity. The for is also the same type of catalyst and with the same

Catalyst loading unevenly, since the particle size of the catalyst is the pressure loss during

tvmI. · Apq K ";) tnlv / cp (nrlipttp <: \ νΛΪΗι <> near Rpo'iahtromreaktor mif central Eir.sneisuna gerineer

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than that of the axial flow reactor. The catalyst size is at least twice as high (perceived, that this is due to the comparatively lower (apparently many times higher) service life than an axial mean Gas velocity along the catalyst stream catalyst bed. The criterion for a practical bed is due. Accordingly, the useful life of the catalyst bed is that Central feed radial flow reactor at 5 measured selectivity for styrene at a given a given pressure difference a higher specific conversion. A decrease in selectivity is caused by a fishing throughput. Increase in thermal cracking (and in the styrene single radial flow catalyst bed with central dismantling) in the feed space and in the hollow catalyst feed has caused the same type of catalyst and the same spaces.

The measured styrene selectivity is defined as

discharged styrene (kg) - fed styrene (kg)

SS =

converted ethylbenzene (kg)

It is inevitable that some of the styrene contained in the starting material is caused by thermal decomposition is destroyed in the reactor. The actual styrene selectivity is used to account for this styrene decomposition defined as follows:

discharged styrene (kg) - (Φ) fed styrene (kg)

Zoo -

converted ethylbenzene (kg)

G means that part of the styrene in the premixed stream of steam and ethylbenzene

gangsmaierial, which is not decomposed in the reactor. (Weight ratio 2: 1) centrally in an annular,

Thermal cracking is favored by longer residence times arranged in an insulated radial flow reactor, which in turn are a sequence of increased catalyst bed fed in and this pressure drop is flowed through. In the case of the radial flow bed with zen- radial from the inside to the outside. The reactor consisted of a central feed, no increase in pressure was observed - an isolated, top and bottom closed cycle drop with the age of the catalyst. linder with an annular catalyst bed of In the axial flow bed, on the other hand, the pressure drop was 2.1 m high and about 56 cm radial thickness,
along the catalyst bed with increasing cat- 35 twenty-four perpendicular to the inner reaction lysator age considerably. This growth in the wall of the vessel, formed by a corrugated iron sieve, the pressure drop in the axial flow reactor as the pressure increased, surrounding the catalyst, which with age can be attributed to the accumulation of catalyst dust on a lower annular gas collector at the bottom of the catalyst bed. The same connections were used to collect the accumulation of catalyst dust from the radial gas stream. A power reactor surrounded by a sieve with no influence on the pressure drop. and arbitrarily perforated axially and centrally arranged

The volume of the feed channel is 2 m long and 25.4 cm in diameter in the Radialnetes pipe

power reactor with central feed essentially served to distribute the gaseous input material in

smaller, for example by a factor of 5 to 8, than the catalyst mass. One at some distance from the

that of the axial flow reactor or the separating plate arranged in the radial 45 reactor bottom with it

Power reactor with peripheral feed. As a result of this the arranged around the inner reaction vessel wall

smaller volumes of the feed duct can cause the catalysis to be carried out by openings covering the gas ducts

Radial flow reactor with central feed, shorter door bed. The reactor was at its top with a

Residence times can be achieved which provide a lower thermal manhole for filling with catalyst and

mixed decomposition. Since the by far 50 had a lower manhole on the side through which the

greatest. Part of the non-selective thermal reaction catalyst could be discharged. He was further-

takes place in the feed channel, where the operating temperature is provided with an upper input material inlet, the

is highest, a decrease in volume is associated with the axial manifold. When

this channel of great importance and extremely pre- catalyst was a catalyst with 0.475 cm middle-

partaking. The styrene degradation in the radial flow reactor 55 uses larger grain diameter, the 87.9 ge

with peripheral feed was not determined. One weight percent Fe ₂ O ₃ , 2.5 weight percent Cr ₂ O ₃ and

Another advantage of a small volume reactor was 9.6 weight percent K ₂ O contained. The superiority

of the feed channel is that it has a central feed compared to the radial flow method

Changes in the steam dilution ratio less compared to the radial flow method with circumferential

is sensitive, since a reduction in the steam feed-in was demonstrated by adding to the reactor

thinning a very small increase in residence time some minor changes were made

of the hydrocarbon feedstock in the inlet to the gas stream to be fed into a cavity

channel. on the top of the reactor above the through

_R. . . a separating plate covered catalyst bed

ß e 1 s ρ 1 eg ₅ f Q _to be able to and from there to the peripheral

In one embodiment of a baskets according to the invention to be initiated and from there to the inside through the

Reactor, which is particularly suitable for the dehydrogenation, to let the catalyst flow and from the axially approach

from ethylbenzene to styrene was found, an orderly tube was removed again.

When conversion and a throughput of 2268 kg ethylbenzene per hour at a dilution with steam in a weight ratio of steam to ethylbenzene as 2 to 5O ° l _o \ Gex: was run 1, the styrene selectivity was in the radial flow method with peripheral feed for 100 days constant at 83, 2 percent by weight. In a comparison run with a standard axial flow method, the styrene selectivity was 84 percent by weight under otherwise identical conditions over a test duration of 100 days. If, on the other hand, the direction of flow in the radial flow reactor was reversed, i.e. using the radial flow method with central feed, with an axial distributor pipe 20.32 cm in diameter being used under otherwise identical conditions, the styrene selectivity was constant at 85.5 percent by weight for more than 100 days . In the latter experiment, the gas stream entering the catalyst bed had an actual linear velocity of 2.3 m / sec. If the distributor pipe with a diameter of 20.32 cm was replaced by an ao pipe with a diameter of 25.4 cm and the same length, the gas velocity on entry into the catalyst decreased to 1.8 m / sec, with a constant selectivity of 85.8 Weight percent was obtained. In the runs described above, the hydrocarbon feedstock was a mixture of fresh and recycled ethylbenzene, the latter containing about 4 to 8 percent by weight styrene. The ethylbenzene was preheated to 520-530 ⁰ C, then mixed with superheated steam 740-760 ⁰ C, the mixture had a temperature from 620 to 640 ⁰ C. This mixture was fed directly to the dehydrogenation zone.

The above selectivities are measured styrene selectivities.

The cause of the low measured selectivity of the radial flow reactor with peripheral feed is primarily the low Reynolds number, N _R s = 50, at the inlet of the radial catalyst bed. The suitability of a reactor decreases below a Reynolds number of about 100, since there is insufficient turbulence and thus also insufficient intimate contact between the flowing gases and the catalyst bed.

The slight difference between the measured Selectivities of the radial flow reactor with central feed, which can be achieved when using a pipe with 25.4 cm and a tube with 20.32 cm in diameter, there may be slight differences in the Composition of the starting material can be attributed, since the experimental results to different Times have been preserved. In addition, channeling in the catalyst bed was observed in the 8 inch tube, which was a consequence of the high velocity of entry of the gases and possibly something to the has contributed to different results.

The hourly space velocity of the gas was in the above experiments: with the axial flow method 127 vol / vol / h, with the radial flow method with central feed and 25.4 cm distributor pipe 167 vol / vol / h, with the radial flow method with central feed and 20.32 cm pipe 161 and for the radial flow method with circumferential feed of l40 vol / vol / h. The hourly space velocity of the gas is the number of normal m ^{3 of} ethylbenzene which ^{flow per m 3 of} catalyst bed per hour. The linear flow rates on entry and exit from the catalyst bed were as follows:

Linear Outlet reactor Flow velocity
(m / sec) 1.53 Incl Axial current feed .. 1.5 1.71 Radial flow circumference feed 0.3 Radial flow central 0.33 feed 0.33 8 '' pipe 2.3 25.4 cm tube 1.8

In the radial flow method with central feed, the outlet speed is accordingly V ₈ to ¹ J _{6 of} the inlet speed.

The residence times in the feed space and in the catalyst bed are important because they have an influence on the thermal Are cracking. These residence times for the various reactor types are listed below.

Axial current feed

Radial flow circumferential feed

Central radial flow feed

8 '' pipe

25.4 cm tube

Dwell time (see) Feed room

0.30 0.42

0.035 0.054

Catalyst-. bed

0.54 0.49

0.43 0.41

The following are typical compositions of feed material and product stream are listed as they occur when operating according to the inventive method with a 50% reaction, a temperature of the Eingabeguts of 640 ° C and the product stream of 570 ⁰ C.

component

Ethylbenzene

Styrene

benzene

toluene

Other

Not condensable
(H ₂ , COsj, CH ₄ etc.)

Enter weight percent

92.33 4.92 0.40 2.19 0.16

Product weight percent

46.52

44.14

1.72

4.70

0.14

2.78

The following pressures and pressure drops are used in comparative tests using a radial flow reactor with central feed and one

Axial flow reactor observed over the same period of time.

Pressure on
Attempt
beginning
(atm) Pressure after a
certain
Test duration
(atm) Radial flow central
feed
Inlet 0.86
0.83
0.03
0.99
0.81
0.18 0.86
0.83
0.03
1.43
0.81.
0.62 Outlet Δ Ρ Axial current
Inlet Outlet AP

The catalytic dehydrogenation of normal butane and 2-methylbutane produce the same results Advantages of the radial flow method with central feed compared to the radial flow method with Circumferential feed or for the axial flow process, as in the production of Ethylbenzene to styrene.

Claims (2)

Patent claims: 1. Process for the production of diolefins or Vinylbenzenes by the catalytic dehydrogenation of monoolefins with 4 to 5 carbon atoms and a chain length of at least 4 carbon atoms or of mono- or diethylbenzene, wherein the heated to reaction temperature mixture of the hydrocarbon feedstock with Dehydrated steam in the presence of a self-regenerating, iron oxide-containing catalyst and then quenching the product, characterized in that the mixture of starting hydrocarbon and water vapor in a manner known per se Feeding into a centrally arranged, axially extending and with axial recesses provided feed line of an annular catalyst bed radially through flowing the annular catalyst bed and the product stream from its peripheral surface is deducted. 2. The method according to claim 1, characterized in that the linear flow rate of the hydrocarbon-vapor mixture on entry into the catalyst bed is 1.8 to 2.4 m / sec.