US2370707A - Treatment of hydrocarbons - Google Patents

Description

'y Patented 6,1945 j TREATMENT or mmnocAnBoNs I Raymond C. Archibald, Berkeley, Calif., assigner to Shell DevelopmentCompany, San'Francisco, Calif., a corporation of Delaware Application November 2, 1942, Serial No. 464,289

11 claims. This invention relates to an improvement in the catalytic treatment ofhydrocarbons boiling in the gasoline boiling range with sulf-active catalysts consisting essentially of pilled dehydrogenating metal sulfides. More particularly,

the. invention relates to a method for increasing the eii/ective life of the catalyst in said processes by a periodic treatment of the catalyst in situ.

As is known, there is a great demand for an economical and` practical process for the catalytic dehydrogenation of the lighter hydrocarbons such as hydrocarbons boiling within the gasoline boiling range. Most of .the hydrocarbon materials which it is desired to treat by catalytic dehydrogenation are derived from petroleum and/or coal tar distillates and contain from traces to appreciable amounts of sulfur compounds. A practical catalytic process suitable for use with these hydrocarbon materials therefore lrequires the use of a sulf-active catalyst. Many processes have been developed wherein these various hydrocarbonmaterials are treated. using dehydrogenating metal oxide catalysts. In general, the dehydrogenating metal oxides are very active dehydrogenating catalysts at elevated temperatures and are employed -in relatively small amounts supported upon major amounts of suitable adsorptive carriers such, in

particular, asactive alumina. Some of these K proposed processes are suitable for certain-applications. All of them, however, have the great disadvantage that theyrequire so-called short and costlylbut materially decreases the production` capacity,A per catalytic converter. Furthermore, the periodic regenerationby burning carbonaceous deposits with air subjects the apparatus to frequent temperature change and alternate oxidizing and reducing conditions. This requires that these processes be effected in apparatus constructed of special steels or alloys. The rate of deposition of. carbonaceousn materials upon the catalyst in certain processes can be repressed to' a certain extent' by the use of hydrogen pressure. This, however, is generally considered impractical inasmuch as under high hydrogen pressures the dehydrogenation reaction is usually considerably repressed. Onthe lother hand, very excellent sulf-active catalysts which may be appliedunder very high hydrogen pressures have been developed particularly roruse in destruc-- tive hydrogenation ofA higherfboiling hydrocarbons. One type oi such catalysts consists essentially of a mixture of metal sulfldes. Under (CL 19e-5o) conditions for which these catalysts were inl tended, that is, for. destructive hydrogenation, considerable hydrogen pressures prevail and there is little deposition .of carbonaceous mate-q, rial. Consequently, under .these conditions-these catalysts have a very long active life. Further- `more, in the destructive hydrogenation when the catalyst is iinally spent, the valuable components are recovered and' regenerated. The regeneration in this case is, however, not similar to that employed in the above-mentioned oxide type catalyst but consists in an entire remaking of the catalyst.

It is found that the above-described sulf-active catalysts are very suitable for the catalytic devhydrogenation of lighter hydrocarbons, for example, dehydrogenatable hydrocarbons yboiling in the gasoline boiling range. In the use of these catalysts for this purpose, dehydrogenation rather than hydrogenation conditions prevail, carbonaceous 'materials gradually deposit upon the catalyst, and in time the dehydrogenation activity of the catalyst declines. Since, however, in the dehydrogenation of such hydrocarbons with catalysts of this type certain quantities of hydrogen, for instance 1 to 50 atmospheres, are suitably employed, the deterioration ofthe catalyst by carbonaceous deposits is very slow. These catalysts may therefore be employed for the de- 30 hydrogenation of these hydrocarbons over relatively long periods, for instance 400 hours, before regeneration of the catalyst is necessary. This, it will be seen, is a distinct:l advantage over the use of the above-described oxide type catalyst.

These snif-active metal sulde catalysts can be applied to carrier materials, as described, for the oxide type catalysts and, in such cases. can -be-regenerated by conventional means, thatv is, by burning oil the carbonaceous deposits with air. 40 During such regeneration, however, the metal suldes are converted to the corresponding oxides and after .the lcarbonaceous deposits have y been removed-it is necessary to subject the catalyst to a thorough sulfurization. This latter step is often diiiicult and costly. These sulf-active metal sulfide catalysts, however, are not as' active as the corresponding oxide catalysts for dehydrovated. The usualmethods involving burning on of the carbonaceous deposits with oxygen or owgen-bearingv gases cause the pellets to lose strength and crumble. Oxygen-containing gases oriljsuch as air. stomste. are furthermore unsuit 5 lytic -dehydrogenation could be readily reactiis advantageous.

` able for the reason that they convert the metal suldes to the corresponding metal oxides.

In copnding application Serial No. 434,893, filed March 16, 1942, of which the present application is a continuation-impart, there is described and claimed a method whereby these pelleted metal suliide catalysts may be advantageously reactivated. According to the method more fully described in said copending application, catalysts consisting essentially of the above-described dehydrogenating metal suldes', when deactivated in the catalytic dehydrogenation of hydrocarbons, are advantageously reactivated in situ by treatment with sulfur dioxide. Whereas regeneration by oxygen causes the catalyst pellets to immediately crumble, repeated reactivation of the catalyst with sulfur dioxide leaves the pellets substantially unaffected in physicall shape and strength. Furthermore, the use of sulfur dioxide to reactivate the above-described suliide catalysts does not cause substantial oxidation of the metal suliides and does not require a subsequent re-sulfurization of the catalyst. Furthermore, the reactivation of these catalysts with sulfur dioxide is very effective, may be effected in a very short time, and does not require substantial change in the temperature conditions in the reactor.

It is now found that a gas mixture comprising sulfur dioxide and hydrogen sulfide is particularly excellent for eiecting the reactivation. In the use of such gas mixtures all danger of oxidation of the catalyst or the reactor walls is eliminated. Also, due largely to the large heat capacity of hydrogen suliide, the reactivation may be eected at a more rapid rate without causing deterioration of the catalyst by local overheating. Furthermore, as will be described in more detail below, mixtures comprising these gases which are particularly suitable may be easily obtained as a by-product from'the conversion process.

The present activation treatment is applicable to any of the pelleted dehydrogenating metal sul-` de catalyst of the above-'described type. It is especially suitable for the treatment of dehydrogenating metal sulfide catalysts consisting essentially of a sulde of a metal selected from Group VI of the Periodic System and a sulfide of a metal selected from Group VIII of the Periodic System. For example. it is especially suitable for use with catalysts consisting .essentially of a pelleted mixture of tungsten sulfide and nickel sulide. These metal sulfides when pelleted inthe pure form often yield hard strong pellets having a metallic luster. In certain cases. however, the use of a small amount of one of the many known binders Also, the dehydrogenating metal sulfide or mixture of such suldes may be pelleted in admixture with a minor amount oi a relatively inert material such as a powder of alumina. kieselguhr, clay or the like. In the apjpended claims when referring to these catalysts'` the expression consisting essentially oiis not meant to exclude minor amounts of such extenders in the catalyst pellets.

These catalysts are especially suitableand may.

be employed for the dehydrogenation of dehydro- -genatable liquid hydrocarbons boiling in the gasoline boiling range such, inparticuiar, as -n aphthenic lhydrocarbons and naphthenic gasoline fractions. Suitable conditions applicable for the vlo catalytic treaiient otthese various hydrocar-Q- of this type are, i'or example. approximately as follows:

Temperature C 425-525 Total pressure atm lil-5G Ratio of hydrogen to hydrocarbon feed mois/mol-- 2-20 Liquid hourly space velocity 0.5-5 After the catalyst has been used on-stream for some time the activity gradually declines to a point where it is desirable to subject it to a regeneration or reactivation treatment. The hydrocarbon feed is discontinued and excess hydrocarbons purged from the catalyst, preferably with hydrogen or with an inertgas. The catalyst activity is then restored by a treatment with a gas mixture comprising sulfur dioxide and hydrogen sulfide. The ratio of sulfur dioxide to hydrogen sulfide in the gas mixture may vary widely. Even a small amount of hydrogen sulfide in the sulfur dioxide is sufcient to prevent oxidation of the catalyst by any contaminating air or oxygen. Larger amounts allow the gas mixture to be passed through the catalyst bedat high 4rates without danger of overheating the catalyst.

Also, the gas mixture may contain one or more inert gases such as nitrogen, carbon dioxide or the like. Very suitable gas mixtures may, if desired, be prepared by burning hydrogen sulfide with an insufcient amount of air. The concentration oi hydrogen sulfide and sulfur dioxide in the gas vmay be adjusted and controlled by adjusting and controlling the concentratiomof oxygen in the oxygen-containing gas, for instance,

by adding a diluent to air, and by adjusting and.

controlling the ratio of hydrogen suliide to oxygen-containing gas. Also, if desired, the concentrations of sulfur dioxide and hydrogen sulfide in the combustion gases may be reduced to any desired low concentration by adding a diluent gas. such as recycled spent regeneration gas, .flue gas,

or the like. This can also be effected, if desired,-

by burning a suitable quantity of a hydrocarbon such as natural gas with the hydrogen sulfide.

The time required for the reactivation treatment depends upon several factors such, in particular, as the amount of catalyst, the length of the catalyst bed, the concentration of sulfur di- 1 oxide in the gas mixture, the rate of addition of-the gas mixture, and the temperature. One ofthe advantages of the present process, however, is that the activation may be eiected in a very short time. Thus, the reactivation requires, in general, only a fraction of the time required to regenerate oxide catalysts with oxygencontaining gases. For example, converters of conventional size and design may usually be' reactivated in one-half to four'hours. Longerperiods of reactivation such as ve to ten hours are, however, in no way detrimental. During reactivation treatment very little sulfur dioxide is usually found in the exit gas. When the sulfur dioxide passes through the catalyst mass and appears in .the exit gas the reactivation is usually substantially complete. A

The reactivation of the above-described pelleted catalysts according to the present process is exothermic. When applying the process to large masses of the catalyst the rate of passage of the gas mixture through the catalyst bed is therefore controlled to avoid deactivation of the catalyst by local overheating.

A great advantage of the present process is bcn; a/nd/cr hymocgrbon mixtureswith` 55mg 7gg-.that the reactivation may be eiiected in situ over -a wide range of temperatures.`

" causes lowered conversions.

The reactivation according to the present process may therefore bev conveniently eiected at the temperature at which the catalyst is employed in the dehydrogenation. Thus, for example, when effecting the dehydrogenation process in the abo-mentioned temperature range of 425 C.525 C., the reactivation may be eiected at the reaction temperature. Thus, the delaysl in bringing the reactor from the reaction temperature to a different reactivation temperature, and vice versa, are avoided. Also, the cost of heating and cooling and the detrimental effect of substantial temperature changes on the reactor and the catalyst are avoided. 'I'he temperature of the reactivatfon may, howeverr if desired, be above or below the The maximum reactivav reaction temperature. tion temperature depends upon the thermal stability of the catalyst. With most catalysts o1' the type inquestion, temperatures up to about 750 C. may be applied.. In general, however, no advantage 'is gained in applying temperatures above about 600'C. The minimum applicable temperature also depends somewhat upon the catalyst. In the reactivation of the spent catalyst described inconnection the description of `an operation within the scope of the invention.

Referring to the drawing, the hydrocarbon feed to be treated, 'for instance a mixture of a'straight run naphthenic gasoline fraction and an olnic reformed gasoline fraction, said mixture containing about 0.1%-0.5% sulfur, is passed vialine I to a coll 2 in furnace 3 wherein vit is vaporized and heated to a suitable temperature. Recycle hydrogen is preheated in coil 4 in the furnace and then mixed with the hydrocarbon vapors in a ratio'oi, for instance, about 3:1 to 7:1. The terny peratures of the hydrocarbon vapors and recycled 'hydrogen are adjusted such that the mixture is at' about the Vdesired reaction temperature, for instance 430 C.500 C. The mixture oi' hydrogen and `hydrocarbon vapors under a .pressure of, for instance, 600-700 p. s. i. passes via line 5 to a series of catalytic converters 6 and 1 the liquid hourly space velocity of the hydrocarbon being, for instance, between about 1 and 4.

. .(Liquid hourly space velocity, for the purpose of with the sulfur dioxide-hydrogen sulde mixture,

a pronounced heat eiect is observed. The minimum applicable temperature is the lowest temperature above 400 C. at which this heat effect is observed. In case itis desired to eiect the reactivation at the lowest possible temperature, the gas mixture may be passed through the catalyst mass at a low temperature and the temperature gradually raised until the heat effect is observed. The reactivation is, in general, preferably eii'ected at temperatures above 400 C. where the reactivation is considerably faster.

'I'he reactivation may be effected at any desired pressure. Ordinary pressures are, however, quitesuitable and little advantage is gained in applying higher pressures.

As mentioned above, very suitable gas mixtures comprising sulfur dioxide and hydrogen sulfide `may be' advantageously obtained as byproducts of the process. As pointed out, most of the hydrocarbonaceous materials which it is desired to treat with the above-described catalysts contain from small to appreciable amounts of sulfur compounds'. Under the reaction conditions employed a considerable proportion of the sulfur is converted to hydrogen sulfide. This hydrogen sulfide which forms in the reaction accumulates in/the recycled hydrogen. Ajsmall.

amount of hydrogen sulfide in the recycled hydrogen is usually not detrimental and may in some instances be beneiicial. concentration of hydrogen sulfide in the recycled hydrogen, however, is detrlmentalsince it This hydrogen sulde may be advantageously recovered from the recycled hydrogen, thereby maintaining the conversion at an optimum level. Furthermore, the

recovered hydrogen suliide may be burned with an insumcient amount of oxygen to produce a gas mixture .comprising sulfur dioxide and hydrogen sulfide, which gas mixture is particularly excellent for effecting the reactivation of the catalyst.

' One application of this modication of the process of the invention is illustrated in the at-f tached drawing wherein there is shown by means ot conventional iigures not drawn to scale one assembly of apparatus wherein the process may be advantageously applied. The drawing will be Any appreciable the present description, is defined as the volumes `of hydrocarbon feed, measured as a liquid, passed through a given volume of catalyst per hour.) The converters 6' and l are filled with suitably supported beds of a sulf-active metal sulfide catalyst, for instance, consisting essentially of an intimate mixture of 2 mol par-.ts of nickel sulfide and 1 mol part of tungsten sulde, preferably in the form of pellets. i The reaction mixture of hydrocarbon vapors and recycled hydrogen, after y passing through the first bed of catalyst, are withdrawn via line', passed through heat exchanger 9, and then passed-through converter 1. The reaction mixture is withdrawn from converter 'l via line M, passed through heat exchanger l2,

Acondenser i3, and then passed to a separator I4,

wherein the'liquid hydrocarbon product is separated from the gaseous fraction consisting mostly of hydrogen. The liquid hydrocarbon fraction is withdrawn via line i5. The gaseous fraction contains hydrogen sulfide produced by desulfurization of the hydrocarbon charge. This fraction is withdrawn via, line I6 and treated to separate the hydrogen sulfide. This may be effected in a number of known manners. One excellent method-is, for example, by means of the Shell Phosphate Process (see Rener and Natural vGasoline Manufacturer, September 1941). Thus,

the gaseous fraction is scrubbed with a potassium phosphate solution in a scrubber il'. consisting mainly of hydrogen from which hydrogen sulfide has been substantially removed is recycled via-line i8 and compressor i9 to the heating coil i and back to the process. Line' 2| is .or directed to aunit not shown. Hydrogen sulde gas from the stripper 25 and/or from the accumu- 1ator42'l is passed via,line 28 to a sulfur dioxide. generator 29 wherein itis burned with air or oxygen introduced via line 3l. The ratio of hydrogen sulfide to air or other oxygen-containing sas- The gas ,hydrocarbons boiling in applied is adjusted such that after combustion there is an excess of hydrogen sulfide. The gas mixture comprising, for example, 5% sulfur dioxide and 4% hydrogen sulde is passed via compressor 32, line 33, and heat exchanger 36 to line n 5 leading'to converter 6. The ,exit vapors from converter 6 may be withdrawn via line 31 or may, if desired, be passed through converter l. A separate portion of the gas mixture. is passed via line 38, line 8 and heat exchanger 9 to converter m '1. The eiiluent gas may he withdrawn via line 39.

The assembly of apparatus illustrated in the drawing and described above may be modified in many ways. Thus, for example, three or more converters may be applied either in series or in 5 parallel, or two or more separate banks of converters may be used. Also, converters of various designs may be employed and the exchanger 9 may sometimes be eliminated. If desired, the

combustion of the hydrogen sulfide may be ef- 2U fected under pressure. Also, it may be effected continuously, if desired, and the gas mixture stored in an accumulator vduring the processing. Other variations and modifications will be apparent to those skilled in the art.

I claim as my invention: A

1. In a process for the catalytic treatment of hydrocarbons boiling in the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of dehydrogenating metal sulfide, the improvement which comprises periodically restoring the activity of the catalyst by treatment with a gas mixture comprising suliur dioxide and hydrogen sulfide at a temperature between about 400 C. and 600 C.

2. In a process for the catalytic treatment of hydrocarbons boiling in the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of an intimate mixture ofV a suliide of a metal of Group VI of the 40 Periodic System and a sulfide of a metal of Group VIII of the Periodic System, the improvement which comprises periodically restoring the activity of the catalyst by treatment with a gas mixture comprising sulfur dioxide and hydrogen sulv4,5

fide at a temperature between about 400 C. and 600 C. i

3. In a process for the catalytic treatment of hydrocarbons boiling in the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of an intimate mixture of tungsten suliide and a sulfide of a metal -of Group VIII of the Periodic System, the improvement which comprises periodically restoring the activity of the catalyst by treatment with a gas mixture comprising sulfur dioxide and hydrogen sulfide at a temperature between about 400 C. and 600 C.

4. In a process for the catalytic treatment of the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of an intimate mixture of tungsten-suliide and nickel sulfide, the

improvement which comprises periodically restoring the activity of the catalyst by treatment with a gas mixture comprising sulfur dioxide and hydrogen suliide at a temperature between about 400 C. and 600 C.

5. Ina process for the catalytic treatment of hydrocarbons boiling in the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of an intimate mixture of cally restoring the activity of the catalyst by treatment with a gas mixture comprising sulfur dioxide and hydrogen suliide at a temperature between about 400 C. and 600 C.

6. In a.process for the catalytic treatment of hydrocarbons boiling in the gasoline boiling range with the aid of a sulf-active catalyst consisting essentially of pellets of dehydrogenating metal sulfide, the improvement which comprises periodically restoring the activity of the catalyst by treatment at a temperaturebetween about 400 C. and 600 C. with a gas mixture `comprising sulfur dioxide and hydrogen sulfide produced by burning hydrogen sulde with an insumcient amount of oxygen for complete combustion.

7. In a proeessfor the catalytic treatment of a sulfur-bearing hydrocarbon fraction boiling in the gasoline boiling range with the aid of a sulfactive catalyst consisting essentially of pellets of y dehydrogenating metal suliide wherein hydrogen is recycled through the reaction zone, the improvement which comprises continuously separating hydrogen suliide from the recycled hydrogen and periodically restoring the activity of the catalyst by treatment at a temperature between about 400" C vand 600 C. with a gas mixture comprising sulfur dioxide and hydrogen suliide produced by burning said separated hydrogen suliide with an insufiicient amount of oxygen for complete combustion.

8. The process for restoring the dehydrogenat- 5 ing activity of a suit-active catalyst consisting essentially of pellets of .dehydrogenating metal sulde which has been deteriorated by non-halogen containing deposits, which comprises treating said catalyst with a gas mixture comprising sulfur dioxide and hydrogen sulfide at a temperature between about 400 C. and 600 C.

9. The process for restoring the dehydrogenating activity of a snif-active catalyst consisting essentially of pellets of an intimate mixture of a sulfide of a metal of Group VI of the Periodic System and a sulfide of a metal of Group `VIII of the Periodic System which has been deterior- 1 ated by non-halogen containing deposits, which comprises treating said catalyst with agas mixture comprising sulfur dioxide and hydrogen sulde at a temperature between about 400 C. and

10. The process for restoring the dehydrogenating activity of a sulf-active catalyst consisting essentially of pellets of an intimate mixture of tungsten suliide and a sulde of a metal of Group VIII of the Periodic System which has been deteriorated by non-'halogen containing deposits, which comprises treating said catalyst o with a gas mixture comprising sulfur dioxide and hydrogen sulfide at a temperature between about 400 C. and 600 C.

11. The process for restoring the ydehydrogenating activity of a suit-active catalyst consisting essentially of pellets of an intimate mixture oi' tungsten sulfide and nickel sulfide which has been deteriorated by non-halogen containing deposits, which comprises treating said catalystwith a gas mixture comprising sulfur dioxide and hydrogen sulfide at a temperature between about 400 C. and 600 C.

RAYMOND C. ARCHIBALD.

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