US2450724A - Conversion of sulfur containing hydrocarbons - Google Patents

Description

0st. 59 w48, H. w. GROTE 2,450,724

CONVERSION OF SULFUR CONTAINING HYDRQCARBONS Filed nec. 2a. 194s en/Z7 Zl/ (i170 fe @f Mandy@ Patented Oct. 5, 1948 VUNrrED STATESv PATENT OFFICE CONVERSION 0F SULFUR CONTAINING HYDROCARBONS Henry W. Grote, Downers Grove, Ill., assignor to Universal Oil Products Company, Chicago, Ill.,

a corporation oi Delaware Application December 28, 1946, Serial No. '118,930v

This invention relates to the conversion of hydrocarbons. It is more4 particularly concerned with a combination desulfurization-cracking process in which a high-boiling hydrocarbon is desulfurized and is then converted to lower-boiling hydrocarbons in the presence of a single cracking catalyst.

It is generally recognized that the availability of low-sulfur crudes is diminishing, which fact forces reners to process higher sulfur crudes. The result is that the average over-all sulfur content of the crudes being processed is constantly increasing. Crudes of this nature are relatively undesirable because the sulfur compounds present therein not only are odoriferous, but because they are also corrosive and. in the case of gasoline, detrimentally affect the susceptibility to the addition of tetraethyl lead. It has been .found that the fractions of such crudes that boil above the gasoline range are relatively poor catalytic cracking charge stocks because, in general, they give lower yields of gasoline at a given conversion and because the gasolines produced therefrom at the usual high temperature cracking conditions contain very appreciable amounts of stable sulfur. compounds. The sulfur contents of gasolines produced from such charging stocks appears to be a function of the amount of sulfur in the charge and a function of the olefin content of the gasoline. That is, the more unsaturated 'the gasoline the higher the sulfur content. This relationship apparently is due to the fact that hydrogen sulfide is the initial product formed from the decomposition of the original sulfur compounds in theieed stock, and this hydrogen sulde then combines in part with the olens produced by the cracking reaction to form stable sulfur compounds that boil in the gasoline range. Therefore, it can be seen that it would be advantageous to remove most of the sulfur from the feed to the catalytic cracking unit and to remove the sulfur in such a manner that substantially no oleiins are present when the hydrogen sulfide is present. I have invented such a process.

In one embodiment my invention relates to a combination desulfurization-cracking process which comprises supplying solid cracking catalyst and a sulfur-containing hydrocarbon to a desul` furization zone at a temperature and pressure and for a time sulcient to effect at least partial desulfurization of said hydrocarbon, supplying the desulfurized hydrocarbon and another portion of the solid cracking catalyst to a cracking .zone maintained at cracking conditions, commingling the catalyst from the desulfurization zone with said other portion of catalyst, subjecting the commingled catalyst to stripping to remove at least a portion of the hydrocarbons fadsorbed thereon, and regenerating c the stripped catalyst.

In a more vspecific embodiment my invention relates to a combination cracking and desulfurization process Which comprises subjecting a suly fur-containing hydrocarbon to the action,of a solidcracking catalyst at a temperature of'irom about' 650 to about 850 F. to convert atleast a portion of the sulfur compounds in said hydrocarbon. to hydrogen sulde, separating the hydrocarbon and the hydrogen sulilde from the catalyst, separating the hydrogen sulde from the bulk of the hydrocarbon, commingling'the catalyst from the desulfurization step with vanother portion of the solidcracking catalyst, subjecting the last named hydrocarbon to the action of the commingled catalysts at cracking conditions, sep-l arating the catalyst from the cracked products, subjecting the catalyst to stripping to remove at least a portion of the hydrocarbons adsorbed.'

thereon, and regenerating the stripped catalyst.

Desulfurization of hydrocarbons occurs more completely at a somewhat lower temperature level u than in the 8501100 F. range used in the catalytic cracking of hydrocarbons. In the present process' I use a separate desulfurization reactor which operates in the approximate temperature range of 650 to 850 F. or just slightly above the dewl point of the hydrocarbon fed to this reactor.

At this temperature level, adsorption of heavy hydrocarbons on the catalyst occurs to an ap.

preciable extent, and if spent' catalysts from the desulfurization reactor were taken. directly viay a stripper to the regenerator where the hydrocar- -more adsorbed hydrocarbons removed therefrom `before the catalyst is passed to the regenerator.

One method of 'accomplishing' this in the process of my invention is to pass the catalyst from the desuliurization reactor to the cracking reactor where the used desulfurization catalyst is intimately mixed with and heated by the hot cracking catalyst in the cracking reactor. The commingled stream of hot catalyst from the cracking reactor is then passed to a single stripper and then to the regeneration zone. An alternative method of raising the temperature -of the used desulfurization catalyst is to commingle said catalyst with the hot used cracking catalyst that is being charged to the stripper.

It can be seen from the description of my process thus far given, that I accomplish desulfurization and cracking in separate zones with a single catalytic material employing a single stripper and producing a gasoline substantially uncontaminated with sulfur compounds. Other advantages and features of this process will be apparent from the following detailed description of the attached flow diagram which illustrates one method by which the objects of the present invention may be accomplished.

Referring to the diagram, a 30 A. P. I. gas oilof boiling range 437-739 F. containing 1.76 weight per cent sulfur, is charged through line I containing valve 2 and picks up regenerated catalyst from regenerator 3 which passes through line 4 containing valve 5. The mixture of hydrocarbon and catalyst passes upwardly through line I into desulfurization reactor 6. The temperature of the raw oil feed is adjusted to give a temperature within reactor E of from about 650 to about 850 F. and preferably from '700 to 800 F. Any suitable metal oxide cracking catalyst may be employed such as silica-alumina, silica-zirconia, silica-alumina-zlrconia, silicamagnesia, silica-alumina-magnesia, and the like. These catalysts may be prepared in any suitable manner including separate, successive, and coprecipitation methods. In some1 cases naturally occurring materials such as Iiiltroly Super Filtrol, acid-treated montmorillonite, etc., may be employed. The preferred catalysts are synthetic composites comprising silica-Zircone., silica-alumina, silica-alumina-zirconia and silica magnesia because these catalysts are less detrimentally affected by sulfur than the others. For the purposes of this description it will be assumed that the catalyst is iluldizable, i. e., it is in a finely divided state such as a powder or microspheres. However, it will be readily apparent as the description proceeds that my process is not limited to fluid-type operation but that the moving bed technique also may be employed in this process.

A dense phase bed of solid catalyst is maintained within desulfurization reactor 6 and is kept in a huid-like state of relatively high density by the hydrocarbons passing therethrough at a velocity which partially counteracts the force of gravity on the solid particles and brings about their hindered settling within the bed.

Above the dense phase bed is a relatively light phase region having reduced catalyst density.

At least a portion of the sulfur compounds in the charging stock are converted to hydrogen sulfide and the conversion products are passed through separation means such as a cyclone separator in the upper portion of reactor 6 wherein entrained catalyst particles are removed from said conversion products and returned to the dense phase. The conversion products are then discharged into line 'I containing valve 8 and are passed to suitable separation means 9 which in this illustration is a distillation column.

of the dense phase catalyst zone within said re- Column 9 may be a simple stripper wherein hydrogen sulde is removed from the hydrocarbons and discharged through line I0 containing valve II. On the other hand, if there has been some conversion of the high-boiling hydrocarbons to gasoline in desulfurization reactor 6, the gasoline and the, hydrogen sulide may be separated from the unconverted gas oil in distillation column Il and a subsequent separation eifected between the gasoline and the hydrogen sulfide. Such gasoline as is produced in reactor 6 is relatively saturated because of the low temperature and low conversion prevailing there.

The hydrogen sulfide-free hydrocarbon from column 9, which has a sulfur content of 0.30% is removed through line I2 containing pump I3 and valve I4 and is commingled with a stream of hot regenerated catalyst from regenerator 3, said stream of catalyst being supplied through line I5 containing valve I6. The mixture of catalyst and oil is directed into the lower portion oi' cracking reactor I'I and is substantially uniformly distributed over the cross sectional area of the reactor by means such as perforated plates or grids horizontally disposed therein. A dense phase bed of solid catalyst particles is maintained in cracking reactor Il. The temperature in said reactor is maintained within the range of 850 to l F. and preferably between 900 and 975 F. The temperature is maintained by the heat supplied thereto in the hot regenerated catalyst, but if necessary the hydrocarbon charged to` thecracking reactor may be preheated. In the reactor a portion of the high-boiling hydrocarbons are converted to lower-boiling hydrocarbons and the conversion products are directed from reactor I1 through line I8 containing valve I9 and into distillation means 20, which may comprise one or more fracticnators and absorbers, wherein separation is effected between the gas, gasoline, and recycle stock. For the purpose of this description, gaseous hydrocarbons are withdrawn through line 2l containing valve 22, gasoline is withdrawn through line 23 containing valve 24, and recycle stock is withdrawn through line 25 containing pump 26 and valve 2l. If desired, a portion or all of the recycle stock may be passed back to cracking reactor II through line 28 containing valve 29.

In some instances, particularly when the cracking operation is conducted to yield a relatively saturated gasoline, it may be desirable to use` a common fractionator for the eilluent streams from both reactors. In such a case the hydrocarbon eilluent from desulfurization reactor 0 is passed through line 1 and into line 30 containing valve 3l and thence into line I8 and into distillation means 20.

Used catalyst from desulfurization reactor G may be withdrawn through line 32 containing valve 33 and passed into cracking reactor I1 where it commingles with and is heated by the hot cracking catalyst. The catalyst will ow from reactor E to reactor I1 Without the aid of a carrier fluid if the transfer line is inclined at an angle greater than the'angle of natural repose of the catalyst particles. However, if desired, the catalyst may be transported between the reactors by means of a carrier fluid. Used desulfurization catalyst may enter reactor I1 at any point, however, the point selected usually is in the region actor. If desired, the catalyst from reactor 6 may be mixed with the hot regenerated catalyst in line I2. This procedure results inl a substanthus making a more saturated product.

The mixture of used catalysts in reactor Il is withdrawn through line 34 and passed into stripper 35. A suitable stripping medium such as steam or other inert gas or vapor is passed into stripper 35 near the bottom through line 36 containing valve 31 and rises therethrough countercurrently to the descending catalyst therein. The upper portion of stripper 35 provides a separating or disengaging space for vapors and catalyst particles. Suitable plates and grids may be placed within stripper 35 to provide thorough rcontact between the countercurrently moving streams. The hydrocarbons desorbed from the 'catalyst vand the stripping medium pass from chamber 35 through line 45 and valve 46 into the upper portion of reaction chamber l1 where they combine with the conversion products and are discharged therewith.A In some instances,.it may be desirable to pass the used desulfurization catalyst from reactor 3 directly into line 34 via line 32 and line 38 containing valve 39.

The stripped catalyst is passed from stripper 33 through line 40 into regenerator 3 wherein it is contacted with an oxygen-containing gas at a combustion temperature, and the combustible material is burned therefrom. The oxygen-containing gas is supplied to the regenerator through line 4I containing valve 42 and the combustion products are removed from the regeneration -zone through line 43 containing valve 44.

I claim as my invention:

1. A combination desulfurization cracking process which comprises supplying solid cracking catalyst and a sulfur-containing hydrocarbon to a desulfurization zone at a temperature and pressure and for a time sumcient to effect at least a partial desulfurization of said hydrocarbon, supplying desulfurized hydrocarbon and another portion of the solid cracking catalyst to a cracking zone maintained at cracking conditions;

to a desulfurization zone at a temperature of from about 650 to about 850 F., supplying desulfurized hydrocarbon and another portion of the solid cracking catalyst to a cracking zone maintained at a temperature of from about 850 to about 1100 F.; withdrawing catalyst from said desulfurization zone and introducing said withdrawn catalyst int said cracking zone,

withdrawing catalyst from said cracking zone and subjecting the latter catalyst to stripping and regeneration, and supplying one portion of regenerated catalyst to desulfurization zone and another portion to the cracking zone as aforesaid.

, 3. A combination desulfurization-cracking process which comprises supplying solid cracking catalyst anda sulfur-containing hydrocarbon to a desulfurization zone at a temperature and pressure and for a time sufficient to convert at least a portion of the sulfur compounds in said hydrocarbon to hydrogen sulfide, separating the hydrocarbon and the hydrogen sulfide from the catalyst, separating the hydrogen sulfide from the bulk of the hydrocarbon, subjecting the last named hydrocarbon to the action of another portion of a solid cracking catalyst at cracking conditions; withdrawing catalyst from said desulfurization zone and introducing said withdrawn catalyst into said cracking zone, withdrawing catalyst from said cracking zone and subjecting the latter catalyst to stripping and regeneration, and supplying one portion of regenerated catalyst to desulfurization zone and another portion to the cracking zone as aforesaid.

4. A combination desulfurization cracking process which comprises supplying solid cracking catalyst and a sulfur-containing hydrocarbon to a desulfurization zone at a temperature of from about 650' to about 850 F. to convert at least a portion of the sulfur compounds in said hydrocarbon to hydrogen sulfide, supplying desulfurized hydrocarbon and another portion of the solid cracking catalyst to a cracking zone maintained at a temperature of from about 850 to about 1100 F.; withdrawing catalyst from said desulfurization zone and introducing said withdrawn catalyst into said cracking zone, with drawing catalyst from said cracking zone and subjecting the latter catalyst to stripping and regeneration, and supplying one portion of ,iregenerated catalyst to desulfurization 'zone and another portion to the cracking zone as aforesaid.

HENRY W. GROTE.

REFERENCES CITED The following references are of record in the ille of this patent:

UNrrED .s'raras 4PATENTS Nelson Jan. 28, 1947

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