US2376191A - Chemical process - Google Patents

Description

May 15, 1945. B. E. ROETHELI Erm. 2,376,191

CHEMICAL PROCESS Filed sept. 12, 1942 2 sheets-sheet 1 SEPAPATOR May 15, 1945 B. E. ROETHELI E'rAL 2,376,191

CHEMICAL PROCESS Filed Sept. l2, 1942 2 Sheets-SheetI 2 QUNCHIIVG dHA MBE a /70 REAdTo7@-\ 29 700 Patented May 15, 1945 CHEMICAL PROCESS Bruno E.

Scharmann,

Roetheli, Cranford, and Walter G. Westfield, N. J., assignors, by

mesne assignments, to Jasco, Incorporated, a corporation of Louisiana Application September 12, 1942, Serial No. 458,086

(Cl. 26o-680) 2 Claims.

a continuation-in- Serial No. 407,550,

The present application is Dart of our prior application, filed August 20, 1941.

'I'he present invention relates to improvements in the art of dehydrogenating hydrocarbons and, more particularly, it relates to the dehydrogenation of hydrocarbons such as butylene to form butadiene under controlled conditions of temperature and contact time to enable the attainment of a high degree of selectivity.

In our prior application, Serial No. 407,550, We have disclosed means for obtaining very short contact times which may be less than 1 second in duration. We have no discovered that by operating at somewhat lower temperatures, say around 1100* F., we may extend the contact time between catalyst and reactants, and at these lower temperatures we prefer to operate the process in the range of from not less than 1 to not more than seconds contact time between the reactants and the catalyst in the reaction zone.

Our present invention may be suitably illustrated in a preferred modification by the accompanying drawings which are identical with those filed in our prior application, Serial No. 407,550, Iiled August 20, 1941.

Thus, in Fig. I we have shown a complete fiow diagram which discloses in connection with the specification, a preferred modification of our invention; and in Fig. II there is shown an enlarged view of our improved reactor. Throughout the views similar reference characters refer to similar parts.

Referring in detail tothe drawings, I represents a hopper in which the reaction takes place. The internal construction of our improved reactor is shown in detail in Fig. II and will be subsequently described in detail in discussing that figure of the drawings. Catalyst in the form of powder having a particle size of from 200-400 mesh is also discharged into the reactor from another hopper (I0) in a manner that will be presently explained. The hopper I0 contains a dehydrogenation powdered catalyst preferably in a heated and activated condition and is in communication at its lower end with a standpipe I2 projecting downwardly asshown. This pipe may be of any convenient dimension, such as 36 inches in internal diameter, and a vertical length of 40-60 ft. These dimensions are purely illustrative and are governed by the quantity of catalyst to be fed to the hopper in any particular case. The lower end'fo the pipe is provided with a control valve I4 which is adapted to control the rate of flow by gravity of powder in pipe I2 into the horizontal bend I6. Horizontal bend I6 is in communication with upwardly extending standplpe I8 which projects, as shown, into hopper I. In other words, the feed of catalyst to the reactor l is through a down-flow pipe I2 and an up-iiow standpipe I8. This flow may be accomplished by regulating the densities in pipes I2 and I8 respectively, by selecting the proper pipe dimensions, coupled with the introduction of fluidizing gas as follows. First, to cause catalyst to flow freely in pipe I2 a fluidizing gas is injected therein through pipes 2|. By the same token to .fluidize the catalyst in pipe I8, gas is injected through pipes 20 causing the density in pipe I8 to be less than that in pipe I2. Hence. catalyst will ilow by the means indicated, i. e., diierence in densities between the material in pipes I2 and I8, in the indicated direction. It is to be understood that the amount of gas injected into pipe I2 is much less than that injected into pipe I8, say one-fourth as much or less.

There is also discharged into the reactor a quantity of butylene, this material being supplied through line 5. The catalyst and the butylene are mixed in mixing device 24, and the mixture is then caused to ow upwardly in the reactor. The temperature of the gas in line 5 entering the reactor is about 1000 F., while the catalyst in line I8 is at a temperature of about l250 F. The gas and catalyst are mixed in proportions such that the temperature of the mixture is about 1150 F. with most catalysts and we prefer to maintain a density of the suspension in the region just above the mixing device 24 of from about 8-25 lbs/cu. it. which condition is attained by regulating the gas velocities between 1 and 10 ft. per second where the particle catalyst size is from 200-400 mesh. Also a gas pressure of about mm. of mercury is preferred within the reactor for the reaction. Under the conditions stated, the reaction occurs to form ordinarily, butadiene from normal-butylene, and then by means which will be subsequently explained more fully hereinafter, the bulk of catalyst. is separated from the reaction mass and gravitates from the bottom of the reactor from which it is withdrawn through standpipe 25, mixed with air in a mixing device 28, the air entering through line 30, and thence conveyed through pipe 3| into a regenerator 3,5. The dimensions of regenerator 35 and the gas velocities are such dimensions that when the catalyst is mixed with the required amount of air or other free oxygen containing gas, the density of the mixture is from about 8 to 25 lbs/cu; ft. The catalyst in line 25 is'at a temperature of 1050 F.1,150 F., and under these conditions when mixed with air at ordinary atmospheric temperature in mixer 28 active combustion takes place in regenerator 35 with the consumption of carbonaceous deposits produced on the catalyst as a result of the reaction taking place in reactor I. Ordinarily it is preferable to operate regenerator 35 under superatmospheric pressure, say pressures up to 1-5 lbs/sq. in,

gauge or higher, as dictated by economic considerations, ln order to accelerate the oxidation of the contaminating carbonaceous material. The ue gas and the regenerated catalyst are withdrawn from regenerator through line 40 and discharged into a cyclone separator 4| built into the top of hopper I0. The separator effects separation of the regenerated catalyst from the flue gas, and the latter is withdrawn through line 42 and, if desired, sent' to a second cyclone separater to remove further quantities of catalyst. In some cases, it is desirable to employ three cyclones or even more to insure complete removal and recovery of catalyst from iiue gas. The hot iiue gases substantially freed of catalyst may then be passed through a waste heat boiler to recover a portion of their energy content. The catalyst separated in cyclone separator 4| gravitates into hopper l and is recycled to the reactor in the manner previously described.

In the drawings, we have shown means for controlling the regeneration temperature of the catalyst in regenerator 35. As shown, catalyst, that is regenerated catalyst, may be withdrawn through hopper I0 through line 62, mixed with air from line 60 in injector 6I, thence discharged through cooler 63 and line 50 into regeneration vessel 35. The cooled regenerated catalyst may be at a temperature of say 30D-500 F. as it enters the regenerator, and may be in the proportions of say lo-2 or more parts by weight of regenerated catalyst per part of unregenerated catalyst. 'Ihe cooler regenerated catalyst serves to increase the heat capacity of the mixture and temper the exothermic reaction by absorbing heat released during regeneration.

Referring again to reactor l, it will be noted that a second chamber 10 is superimposed at the top of reactor. This chamber contains the reaction products and catalyst added to quench the reaction mixture. The manner of adding the catalyst will be presently described, but first let it be observed that the newly added catalyst plus the remainder of the original catalyst not separated, together with the reaction mass, are Withdrawn overhead through line 12 and passed into a cyclone separator 15 where the bulk of the quenching catalyst and the catalyst not previously removed are separated from the vapors. The separated catalyst passes into a receiving hopper 10 and in this hopper is at a temperature of about 950 F. One'streain' of catalyst is withdrawn from hopper 18 through line 80, communicating in its lower end with standpipe 25, as shown. The other stream of catalyst is withdrawn through line 82 carrying a flow control valve 83 at its lower end and thence discharged into bend 84 Where it is mixed with a gas such as methane discharged into 84 through pipe 85, and thereafter the catalyst is passed upwardly through line 90 through a heat exchanger 95 where the catalyst is cooled to a temperature such that when withdrawn through line |00 it is at a temperature of about 600 F., whereupon it is inJected into the reaction mass in reactor I after removal from the reaction mass of the bulk of the catalyst with which it was previously associated, and thereafter the quenching catalyst carried upwardly in suspension into quenching chamber 10 previously mentioned. The amount of catalyst recycled from hopper 18 to quenching chamber 10 will depend of course entirely on the amount of gas and catalyst iiowing into chamber 10 and the temperature thereof. We have found that good results are obtained by recycling to zone 10 from hopper 18 suiiicient rality of cyclone separators 28.

catalyst so that a temperature of S50-1050 F. prevails in chamber 10. In any event, it is usually preferable to add suiiicient catalyst to lower the temperature of the reaction mass to about 1000 F. or lower because at this temperature undesired side reactions are prevented and the decomposition of the desired butadiene is substantially prevented. In other words, the selectivity is improved by quenching in the manner described, which means that the per cent of the material desired is high. The gases freed from catalyst in separator 15 are withdrawn through line 20 and these are preferably passed through a heat exchanger |22 where they are cooled to about 600 F., thence withdrawn through line |25 and passed into Cottrell precipitator |30 where a catalyst is separated and recycled to line 25 through line |32. The gases are drawn overhead from separator |30 through line |35 and pass through a Cottrell precipitator |40 where more catalyst is separated out and the separated catalyst is withdrawn through line |44 and recycled through 1ine3l to regenerator 35. The reaction products now containing only minor amounts of catalyst are withdrawn from Cottrell precipitator through line |50, thence further cooled in cooler |55, thence discharged through line |58 into an oil Washer |60 where the last traces of catalyst are removed, the scrubbing oil being discharged into the washer through line |62. The washed gases are withdrawn through line |65, passed through entrainment separator |10 and thence to a pump in which they are compressed land condensed prior to separation in a suitable system. The pressure conditions, i. e., the partial vacuum previously referred to in reactor is maintained through pump and suitable valves, in known manner.

Referring now to Fig. II for a detailed description of our improved reactor and its immediate accessory apparatus, it will be observed that the catalyst and the butylene enter the reaction vessel I and pass into the mixing chamber 24 and thence are delivered into the reaction chamber 25 where the main reaction takes place, the catalyst being in the form of a dense mass or phase thoroughly intermixed with the reactant. Disposed about the reaction chamber 25 are a plu- These separators are arranged contiguously in the form of a ring or circle about the reaction vessel, and in escaping from reaction vessel 25 the uidized mass and reactant gas are forced into the separators 20. The bulk of the catalyst, usually over A%, is separated from the gases and gravitates to the bottom portion 36 of the reaction vessel, while the gases flow upwardly through outlet pipes 29, thence through pipe 32 into quenching chamber 10. The catalyst which is separated in the separators 21 collects in the bottom of the reaction vessel, as indicated by the catalyst level line L, and is withdrawn from the said reactor and arranged such as to maintain the heated catalyst continuously in the said reaction vessel.

As is known by those familiar with this particular art, the types of cata-lyst which may be employed for dehydrogenations are many and varied. One of these catalysts is metallic nickel. Heretofore the diiiiculty withmetallic nickel has been that it is so reactive that it is not usable because it not only accelerates the formation of, say, butadiene from `butylene but attacks the butadiene to decompose it. In the type of operation which we have described herein, a very active catalyst such as nickel may be successfully employed because the combination of controlled contact time, finely divided catalyst and quenching features enables us to discontinue the reaction and to limit it to a very short period of time of contact between reactants and the nickel at reaction temperatures. In the case of other catalysts such as silica-alumina compositions, alumina-tungsten, alumina-chromium, alumina-molybdenum, the various metallic oxides, and the like, such as copper oxide, nickel oxide, cobalt oxide or mixtures of the same where the catalyst is less active, our process is also of value not only from the standpoint of quenching the reaction but also from the standpoint of supplying at least a portion of the heat necessary for the reaction by recycling hot regenerated catalyst to the reaction zone. Instead of using one of the foregoing catalysts, we may use a catalyst which is very effective for the dehydrogenation of butylene to butadiene, namely, a catalyst consisting of a major portion of magnesium oxide, a minor portion of iron oxide, a promoter such as KzO, and a stabilizer such as CuO. This catalyst was disclosed in the application of Kenneth K. Kearby, Serial No. 430,873, led February 14, 1942, and a preferred modification of that catalyst has the following composition in parts by weight; about '78.5 parts MgO, about 20 parts FeaOa, about 5 parts of CuO and about 1.5 parts KzO. This composition may be modified as disclosed in said application. The value of that catalyst is that itis insensitive to steam or not adversely affected by steam and, consequently, our present process could be operated to dehydrogenate butylene to butadiene employing the last-named catalyst in the presence of added superheated steam, which steam might supply a substantial quantity of the heat necessary to carry out the reaction. In other words, the butylene entering line of Fig. I might be heated to a temperature of say 900 F. and thence discharged into reactor I where it contacts'steam superheated to a temperature of say 1400 F. or higher, and mixed in such proportions with the hot catalyst, the butylene, and the steam as to provide a reaction mixture having a temperature of around 1100 F. Steam, of course, could be introduced through lines 20, thence through line I8 into reactor I, or steam could be injected directly into reactor I. The catalyst just mentioned is regenerated by'contact with steam at 1400 F. or thereabouts where according to the water-gas reaction, the carbonaceous contaminants on the catalyst form with said steam, CO and CO2.

To recapitulate, our present invention involves the concept of controlling accurately the contact time between a gaseous reactant and a solid catalyst, and while we in detail in connection with the specic problem of dehydrogena'ting an olefin, obviously the inventive concept is applicable to a great number of processes, such as gas oil cracking, desulfurization, aromatization, oxidations, simple and destructive hydrogenations, chlorinations, and numerous other gas phase reactions where contact time is an important consideration from the standpoint of yields or for other reasons. It will be noted that according to our process, we prefer to quench the reaction ass by means of a cooled solid, such as a solid c talyst added in sumcient quantity to lower the reaction mass to temperahave described the invention tures substantially below reaction temperatures, and since the process may be operated to quench the catalyst just above the reaction zone, very short contact times may be effected. On the other hand, if longer contact time between reactant and catalyst is desired, the quenching may be performed in a subsequent stage, say by adding cooled catalyst in line 12. It will be understood that instead of using catalyst to quench the reaction mass, we may use an inert solid such as sand, lime, or refractory material which is added in suicient quantity and at a sufficiently lower temperature to effect the desired result.

Other features of our invention involve, as heretofore set forth, an up-flow standpipe arrangement for adjusting pressure differentials between the reaction zone and the regeneration zone; another feature involves furnishing at least a portion of the heat required for endothermic reactions by supplying the proper amount of heated catalyst. Finally, the catalyst flowing in the various means may be uidized by steam in the case Where the catalyst is not affected by steam as heretofore mentioned, or by the introduction of other gases such as methane, CO2, CO, nitrogen, and the like; that is to say, these gases may be added through lines 60 and 20 and at other points in the system heretofore mentioned, to attain the desired fluidity of catalyst.

The pressure in reactor I may vary from about mm. of mercury to above atmospheric pressure, subatmospheric pressure being preferred. The temperature conditions prevailing within the reactor I may vary from about 900 F. to 1400 F. depending on the contact time between the reactants an. catalyst in dehydrogenation, and in the case of butylene dehydrogenation the contact times may vary from a fraction of a second up to 5 seconds, with temperatures of the order of 1300 F. to 1400" F. preferred and contact times of less than and up to 5 seconds.

Many modifications of our invention will be obvious to those skilled in this particular art.

What we claim is:

1. A continuous method for dehydrogenating butylene to butadiene which comprises discharging the preheated butylene into a reaction zone, simultaneously discharging into said reaction zone a dehydrogenation catalyst in the form of a udized powder, causing the butylene and the uidized powdered catalyst to remain in contact with each other at temperatures within the range of from 9501400 F. for a period of not less than 1 second and not more than 5 seconds by. adding a quantity of cooled catalyst to the reaction mass when they have been in contact with each other for the time period stated, withdrawing the reaction mass from the reaction zone, separating the catalyst from the reaction mass, recovering butadiene therefrom, regenerating the catalyst and returning the regenerated catalyst substantially uncooled to the reaction zone;

2. The method set forth in claim 1 wherein a portion of the catalyst separated from the reaction mass is cooled and recycled to the reaction mass where-it serves to quench said reaction mass.

BRUN() E. ROETHELI. WALTER G. SCHARMANN.

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