US2345129A - Conversion of hydrocarbon oils - Google Patents

Description

March 28, 1944. W, E. KUHN CONVERSION OF HYDBOCARBON OILS F1ed`Aprl 10, 1941 2 Sheets-Sheet 1 Enma GZQOU N M U KR .im WV N Al. W

BY @af/K ATTORNEYS March 28, 1944. w. E. KUHN CONVERSION oF HYDRocARBoN oILs Filed April lO, 1941 2 Sheets-Sheet 2 m W@ MFM mm .M w ah m NamL NORQZOFUQNL ATTORNEYS Patented Mar. 28, 1944 UNITED STATT-:s PATENT OFFICE CONVERSION OF HYDROCARBON OILS Wayne E. Kuhn, Scarsdale, N. Y., assigner, by f mesne assignments, to The Terras. Company,

New York, N. Y., a corporation o! Delaware Application April 10, 1941, Serial No. 387,814

c claims.

A separate intermediate constituents from higher boiling and lower boiling components and such intermediate constituents subjected to catalytic cracking. V

While catalytic cracking can be applied advantageously to straight run stocks, the insufiiciently converted products of the reaction are not Well adapted for recracking catalytically, either for recycling to the catalytic cracking zone or for passage to a subsequent catalytic cracking zone. However, by thermally cracking the insufficiently converted products of the catalytic reaction, products higher boiling than gasoline are obtained which may then with advantage be subiected to catalytic cracking. In accordance with the invention therefore higher :boiling products obtained in the catalytic cracking of the straight run stock are subjected to thermal cracking and the products ci the thermal cracking are fractionated to separate intermediate constituents of the nature of kerosene or gas oil from lighter distillate products and from heavier products of the reaction and these intermediate constituents, which have been reconditioned by the thermal cracking and made suitable for catalytic cracking, are subjected to catalytic cracking either in a separate catalytic cracking zone or by being returned to the primary catalytic cracking zone for cracking together with the straight run stock. In practicing the invention recycling is avoided in the thermal cracking or reconditioning operation, since the kerosene or gas oil stocks obtained in recycling thermal cracking operations are of a relative refractory nature and do not give the superior results obtainable by catalytically cracking the product of the single pass thermal cracking.

'petroleum is distilled to obtain a residual stock and a condensate stock suitable for catalytic cracking. The residual stock is subjected to thermal cracking or viscosity breaking to produce additional quantities of gas oil and kerosene constituentS and by avoiding recycling in the viscosity breaking step kerosene and gas oil constituents which are well adapted for catalytic cracking may be obtained. The straight run condensate is subjected to catalytic cracking and higher -boiling products obtained from the catalytic cracking operation are subjected to single-pass thermal cracking, the products produced in the single-pass thermal cracking and viscosity -breaking opertaions are fractionated'and intermediate constituents of the nature of kerosene or light gas oil from the two single-pass cracking operations are combined for passage to the V'catalytic cracking operation while heavier constituents produced in the single-pass cracking operations are combined for cracking in thermal cracking zone.

The invention further contemplates that, in stead ofv subjecting'the crude residue to viscosity breaking, it may be subjected to delayed coking. In spite of the fact that coking is considered a drastic cracking operation and, as a matter of fact, is drastic particularly as regards the heavier components which are converted to coke, it is found that when subjecting the residue to delayed coking and carrying on the coking Without the recycling of gas oil, that intermediate constituents, gas oil and kerosene constituents, may be obtained which are of a character adapted for catalytic cracking and, in accordance with the invention these intermediate constituents from the coking operation are subjected to catalytic cracking. f

For the purpose of more fully disclosing the invention reference is now had to the drawings wherein:

Fig. 1 -is a diagr 1.. atic drawing illustrating iapparatus,adapted for the practice of the invenion. v

Fig.' 2` is a diagrammatic drawing showing apa nal recycling paratus adapted for practicing certain modiii@ g the separated vapors are subjected to fractionation in the upper sections of the tower wherein the vapors are fractionated to produce the various cuts desired. A trapout tray I4 is indicated for the collection of a condensate suitable for catalytic cracking. Light vapors such as gasoline are removed from the tower to a condenser i5. A tray I6 `is indicated for the collection of gasoline fractions, such as a heavy naphtha cut, which it may be desired to reform.

The fraction collected in tray i4 is directed by a pump i1 to a heating coil I3 disposed in a furnace is adapted to heat the oil to a desired reaction temperature. The heated oil passes to a catalyst chamber 2li containing a suitable cracking catalyst. The catalyst consists advantageously of a synthetic silica-alumina type of catalyst. Various acid-treated and metal-substituted clays such as the Super-Flltrcls and acid-treated and metal-substituted natural or artificial zeolites, such as the artiilcial zeolite known as Doucil` constituents such as zirconium oxide or molybdenum oxide. The catalyst may either be disposed as a stationary or fixed mass through which the hydrocarbon vapors pass or as a powder in which case the hydrocarbon vapors are contacted with a stream of the powdered` catalyst.

The catalytically cracked products pass toa fractionating tower 2| wherein the desired gasoline or motor fuel product is separated from higher boiling products which are to be subjected to single pass thermal cracking. 'I'he overhead vapors pass to a condenser coil 22 and the gasoline or naphtha distillate is collected in a receiving drum or gas separator 23. Ordinarily the entire product higher boiling than the desired distillate may be passed to the thermal cracking zone and thisproduct may be withdrawn through a line 24. In some cases, however, it is desirable to make a separation of residual constituents from vapors, and subject the separated vapors to reflux condensation to separate a higher boiling condensate from gasoline or naphtha vapors; and in this case a trapout tray 25 is provided for the. collection of such condensate, the condensate b eing withdrawn through aline 28 and conducted to an intake line 21 of a pump 2l. When itis not desired to pass the residual constituents to the subsequent thermal cracking zone these residual constituents or polymers may be withdrawn through a branch line 23 of the line 24 and utilized as fuel oil.

The pump 28 directs higher boiling components of the catalytic cracking operation, as withdrawn either through line 28 or line 24, through a line 30 to a heating coil 3i disposed in a furnace 32 wherein the oil is subjected to cracking conditions of temperature and pressure to effect thermal cracking. 'Ihe resultant cracked products pass through a transfer line 33 into a separating and fractionating tower 34.

Crude residuum is withdrawn from the crude stripping tower i3 through a line 35 and is directed by a pump 38 to a heating coil 31. positioned in a furnace 38 wherein the residue is subjected to cracking conditions of temperature and pressure to effect cracking or viscosity breaking and the resultant cracked or viscosity broken products are delivered through a transfer line 39 to the separating and fractionating tower 34.

The cracked products from the single-pass thermal cracking coil 3i and from the single-pass viscosity breaking coil 31 are delivered to a primary separating section 40 of the tower 34 wherein separation of vapors from liquid residue takes place, the liquid residue or fuel oil being withdrawn through a line 4i. The separated vapors are subjected to fractionation in the upper sections of the tower 34, a heavy reflux condensate of the nature of heavy gas oil collecting in a tray 42 and a lighter reflux condensate of the nature of light gas oil or kerosene collecting in a tray 43, while gasoline or naphtha vapors pass overhead to a condenser coi144 thence to a distillate receiving drum or gas separator 45. The heavy reux condensate collecting in tray 42 is withdrawn from the system through a line 46. This cut will normally be too heavy to be well adapted for catalytic cracking and may be subjected to thermal cracking in a separate unit. The lighter reflux condensate collecting on the tray 43 is adapted for catalytic cracking and is withdrawn through a line 41 and conducted by a. pump 48 to the heating coil i8 of the catalytic cracking operation.

In an alternative operation the crude residue from the crude stripping tower, instead of being subjected to viscosity breaking, is subjected to coking and in carrying on the coking operation the residue is heated in the coil 31 to a cracking temperature sulicient to support coking upon discharge into a coking chamber, the heated oil being delivered through a branch line 49 to a heat insulated coking chamber 50 wherein coking takes place. The vapors evolved in the coking operation pass through a vapor line 5| to the separating zone 40. In this operation the products from the single pass thermal cracking coil 3l are also discharged intol separator 40 and the heavy tarry condensate from the coking operation is combined with the residual constituents of such thermal cracking operation to form a residue adapted for fuel oil which is withdrawn through the line 4 I.

By carrying on either the viscosity breaking or the coking operation in a single-pass manner as described the light gas oil constituents collecting in the tray 43 will not be particularly refractory and will be adapted for catalytic cracking.

Referring now to Fig. 2 certain portions of the apparatus are the same as certain portions of the apparatus of Fig. 1, like elements in both drawings` being designated by like reference numerals. 'I'he crude oil stripping, the catalytic cracking and fractionation of the catalytically cracked products, the single-pass cracking zone for thermally recracking higher boiling products from the catalytic cracking operation and the viscosity breaking operation and coking operation of Fig. 2 are the same as in Fig. 1 and need not be redescribed. However, in the Fig. 2 operation the products from the viscosity breaking coil 31 and from the thermal recracking coil 3|, instead of being fractionated together in a common zone, are passed to separate fractionators.

The products from the Viscosity breaking coil 31 pass through a transfer line 39a into a separating zone 40a of a separating and fractionating tower 34a. The separated residue is Withdrawn through a line 4i a and the vapors are fractionated to form a heavy reflux condensate such as heavy gas oil collecting ina tray 42a and a lighter reflux condensate suchas light gas oil collecting in a tray 43a. The latter condensate is withdrawn through a line 47a and conducted by a. pump 8a to the heating coil I8 of the catalytic cracking operation. The overhead vapors from the tower 34a pass to a condenser coil 44a and the gasoline or naphtha distillate is collected in a receiving drum or gas separator 45a.

The products from the thermal recracking coil I I pass through a transfer line 33h to a separating and fractionating tower- 34h wherein separation of vapors from residue takes place, the residue being withdrawn through a line Mb. The separated vapors are fractionated to form a heavy reflux condensate such as heavy gas oil collecting in tray 42h and a lighter reflux condensate such u light gas oil collecting in tray 43h. The overhead vapors pass to a condenser coil 44h and the gasoline or naphtha distillate is collected in a receiving drum or gas separator 45h. Condensate from the tray 3b is withdrawn by a line 4'Ib and conducted by a pump 48h to the heating coil I8 of the catalytic cracking operation.

Condensate from the tray 42a of the tower 34a is withdrawn through a line 46a and directed by a pump 52 to a heating coil 53 disposed in a furnace 54 wherein the oil is subjected to cracking conditions oi temperature and pressure to effect thermal cracking. Condensate from tray 42h of tower ub is withdrawn through a line 55 and 'directed by a pump 56 to the cracking coil 53.

The resultant cracked products pass from the cracking coil 53 to a separating and fractionating tower-T wherein vapors separate from residue,

which residue is withdrawn through a line '58. The separated vapors are subjected to fractionation -to form a reilux condensate collecting in tray i9 which is withdrawn through a line S0 and cycled by the pump 56 to the cracking coil 53.

' Theoverhead vapors pass from the tower 51 to a condenser 6I and the distillate is collected in a receiving drum or gas separator 62.

Heavy naphtha collecting in tray I 6 of the crude tower I3 is withdrawn through a line 63 and directed by a pump 64 to a heating coil 65 positioned in a furnace 66 wherein the naphtha is subjected to cracking temperatures adequate to eect transformation of the hydrocarbons into hydrocarbons of increased antiknock quality. The resultant reformed products are discharged through a transfer line S1 and combined with the products from the cracking coil 53 for fractionation therewith in the tower 51. 1n some cases it is desirable to reform the gasoline distillate. produced in the viscosity breaking or coking operation and to accomplish this purpose a,

line Il serves to withdraw distillate from the receivingdrum 45a which distillate is directed by a pump 68 to the reforming coil 55. If desired, instead of sending the entire cut of gasoline from the viscosity breaking operation to the reformer the gasoline constituents may be fractionated and only ,the heavier fractions of the gasoline directed to the reformer. c

In. the combination process illustrated in Fig. 2 the crude residue from the crude stripping tower mayfbe subjected to coking, instead of viscosity breaking, in which case the products from the heating coil 31 are discharged through a line 49 to acoking drum 50. The vapors evolved in the coking operation pass through vapor line 5l to a primary dephlegmating zone a from which heavy tarry condensate is withdrawn through the line lla.

In practicing the invention the mixture of straight run gas oil and gas oil from the thermal recracking and viscosity breaking or coking operations is vaporized in the coil I8 and heated sumciently to maintain temperatures of the order of 850 F.-1050 F., preferablytemperatures of 910 F.1000 F. in the catalytic chamber 20. The operation is preferably conducted at pressures not in excess of lbs., pressures of 25-50 lbs.

being recommended. The higher boiling products from the catalytic cracking operation are subjected to single-pass thermal cracking in the coil 3I at suitable cracking temperatures such as 850 F.-950 F. under 200-600 lbs. pressure. The crude residue is subjected to single-pass viscosity breaking at temperatures of, for example, 880 F.- 950 F. under 300-600 lbs. pressure. The mixture of heavy condensate from the viscosity breaking or coking operation and from the thermal recracking operation is subjected in cracking coil 53 to cracking temperatures of, for example, 850 F.950 F. under 20D-600 lbs. pressure. When carrying on coking of the crude residue the residue is heated to a temprature approximating 900 F. and directed into the coking chamber wherein coking is carried on at temperatures approximating 825 F.850 F. under preferably low pressures such as pressures below 50 lbs.

In an example of the invention the straight run gas oil is heated to vaporize it and heat it to a desired cracking temperature and passed into the catalyst chamber wherein a temperature of 950 F. is maintained under 50 lbs. pressure. The resulting products are fractionated to recover gasoline distillate of 400 F. end-point and the higher boiling products are passed to the singlepass thermal cracking zone wherein the oil is subjected to cracking at a temperature of 910 F. under 400 lbs. pressure.

910 F. under 600 lbs. pressure. The products from the viscosity breaking and thermal recracking operations are fractionated together with the vapors being fractionated to form a heavy reflux condensate, an intermediate gas oil fraction and a gasoline distillate and the intermediate gas oil fraction is directed to the catalytic cracking zone for cracking together with the straight run gas oil.

In another example the operation is conducted as in the preceding example except that the crude residue is subjected to delayed coking with an outlet temperature in the heating coil of 910 F. and with coking being conducted at 30 lbs. pressure. In this operation light gas oil constituents from the coking operation are combined with light gas oil constituents from the thermal recracking operation for passage to the catalytic cracking zone.

In additional examples of the invention the process is conducted under conditions similar to those of the preceding examples except that the products :from both the viscosity breaking and coking operations are fractionated separately from that of the cracked products produced in the thermal .recracking or reconditioning operation, the vapors in all cases being fractionated to form a heavy condensate, an intermediate condensate and gasolinedistillate, with the passage of the intermediate condensates to the catalytic cracking zone and the passage of the heavy con- 'I'he crude residue is subjected to viscosity breaking at a temperature of densate to a separate recycling thermal cracking zone, the cracked products from which are fractionated entirely separately irm the other fractionators of the process. In certain of these additional examples the vapors from the coking and viscosity breaking operations are fractionated to form a? single cut oi gas oil including both light and heavy gas oil constituents and this gas oil cut is subjected to thermal recylcing cracking together with heavy gas oil from the thermal recracking operation while the light gas oil from the single-pass thermal recracking operation is directed to the catalytic cracking zone for cracking together with the straight run gas oil.

In additional examples of the invention, practiced with viscosity breaking and coking of the crude residue, heavy gas oils from the coking and viscosity breaking operations are subjected to cracking in the thermal recycling cracking zone together with heavy gas oil from the single-pass thermal recracking zone, while naphtha distillates including light gas oil constituents from the coking and viscosity breaking operations are combined with straight run naphtha and subjected to reforming. In another example of the invention the process is'oonducted similarly to the` preceding examples except that light gas oil fractions from the viscosity breaking and coking operations are directed to the catalytic cracking zone for cracking together with the straight run gas oil from the single-pass thermal recracking operation and naphth'a fractions from the viscosity breaking and coking operations are passed to the reformer for reforming together with straight run naphtha.

While I have described a particular embodiment of my invention for purposes of illustration, it should be understood that various modiiications and adaptations thereof which will be obvious to one skilled in the art, may be made within the spirit'of the invention as set forth in the appended claims.

I claim:

1. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight-run condensate stock to catalytic cracking, fractionating the resultant cracked products to separate higher boiling constituents from lower boiling products, passing such higher lboiling constituents to a single-pass thermal cracking zone where'in the oil is subjected to conditions of temperature and pressure to effect thermal cracking, separating the resultant thermally cracked products into vapors and residue, fractionating the separated vapors to separate intermediate constituents from higher boiling and lower boiling constituents, directing intermediate constituents so obtained to the catalytic cracking zone, subjecting a petroleum residual charging stock to thermal cracking in a second single-pass thermal cracking zone, separating the later thermally cracked products into vapors and residue, fractionating the latter separated vapors to separate intermediate constituents from higher and lower boiling constituents, directing sid intermediate constituents to the catalytic cracking zone, combining higher boiling constituents produced in the fractionation of the vapors from said singlepass thermal cracking operations and passing the mixture to a third thermal cracking zone wherein it is subjected to cracking conditions of temperature and pressure to effect thermal cracking, separating the latter thermally cracked products into vapors and residue, fractionating the latter separated vapors to separate al reflux condensate from lighter fractions and cycling the latter reux lcondensate' to the third thermal cracking zone.

2. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight-run condensate stock to catalytic cracking, fractionating the resultant cracked products to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass thermal cracking zone wherein the oil is subjected to conditions of temperature and pressure to effect-therma1 cracking, subjecting a petroleum residual charging stock to thermal cracking in. a second single-pass thermal,A

cracking zone, fractionating the vapors from said thermal cracking operations to separate intermediate constituents from higher boiling and lower boiling constituents, directing intermediate constituents so obtained to the catalytic cracking zone, passing higher boiling constituents so .obtained to a third thermal cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to eiect thermal cracking, separating the latter thermally cracked products into vapors and residue, fracticnating the latter separated vapors to separate a reflux condensate from lighter fractions and cycling the latter reux condensate to the third thermal cracking zone.

3. In the conversion of hydrocarbon oils, the process that comprises distilling crude petroleum to separate it into fractions comprising a residual fraction and a condensate fraction, subjecting the condensate fraction to catalytic cracking in a cracking zone, fractionating the resultant cracked products to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass -thermal cracking zone wherein the oil is sub jected to conditions of temperature and pressure to effect thermal cracking, subjecting said resid-v ual fraction to thermal cracking in a second singie-pass thermal cracking zone, fractionating the vapors from said thermal cracking operations to separate intermediate constituents from higher boiling and lower boiling constituents, directing intermediate constituents so obtained to the catalytic cracking zone, passing higher boiling constituents so obtained to a third thermal cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to effect thermal cracking, separating the latter thermally cracked products into vapors and residue, fractionating the latter separated vapors to separate a reflux condensate from lighter fractions and cycling the latter reilux condensate to the third thermal cracking zone.

4. In the conversion of hydrocarbon oils, the process that comprises distilling crude petroleum to obtain fractions comprising a residual fraction, a gas oil fraction and a naphtha fraction, subjecting said gas oil fraction to catalytic cracking, fractionating the resultant cracked products to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass thermal cracking zone wherein the oil is subjected to conditions of temperature and pressure to eiect thermal cracking,

subjecting said residual fraction to thermal4 gamigo ents so obtained to the catalytic cracking zone, passing higher boiling constituents so obtained to a third thermal cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to eilect tliermal cracking, separating the latter thermally cracked products into vapors and residue, fractionating the latter separated vapors to separate a refiux condensate from lighter fractions, cycling the latter reux condensate to the third thermal cracking zone, passing the aforesaid naphtha fraction to a reforming zone wherein the naphtha is subjected to a temperature adequate to effect transformation into constituents of increased anti-knock quality and combining the resultant reformed products with cracked products from said third cracking zone for separation and fractionation therewith.

5. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight run stock to catalytic cracking, fractionating the resultant cracked products in a fractionating zone to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass thermal cracking zone wherein the oil is subjected to conditions of temperature and pressure to eiect thermal cracking, separating the resultant thermally cracked products into vapors and residue, passing the separated vapors to a second fractionating zone wherein the vapors are subjected to fractionation to separate intermediate constituents from higher boiling and lower boiling constituents, directing intermediate constituents so obtained to said catalytic cracking zone, passing higher boiling constituents so obtained to a recycling thermal cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to eiect thermal cracking, separating the latter thermally cracked products into vapors and residue, passing the separated vapors to a third fractionating zone wherein the vapors are subjected to fractionation to separate a reflux condensate from lighter fractions and directing the latter reflux condensate to the recycling thermal cracking zone.

6. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight run stock to catalytic cracking, fractionating the resultant cracked products in a fractionating zone to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass thermal cracking zone wherein the oil is subjected to conditions of temperature and pressure to effect thermal cracking, separating the resultant thermally cracked products into vapors and residue, passing the separated vapors to a second fractionating zone wherein the vapors are subjected to fractionation to separate intermediate constituents from higher boiling and lower boiling constituents, subjecting intermediate constituents so obtained to catalytic cracking and fractionating the resultant cracked products to separate higher boiling constituents from lower boiling productsl passing higher boiling constituents from the second fractional-ting zone to a recycling thermal cracking zone wherein the`oil is subjected to.

latter reflux condensate to the recycling thermal cracking zone.

'1. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight-run condensate stock to catalytic cracking, fractionatingthe resultant cracked products to separate higher Iboiling constituents from lower boiling products, passing such higher` boiling constituents to a single-pass thermal cracking zone wherein the il is subjected to conditions of temperature and pressure to effect thermal cracking,

4separating the resultant thermally cracked products into lvapors and residue, fractionating the separated vapors to separate intermediate constituents from higher boiling and lower boiling constituents, subjecting a petroleum residual charging stock'to coking by passing it through a single-passi heating zone wherein the stock is subjected to )a cracking temperature and discharging it into a coking chamber wherein oonversion to coke occurs by means of contained heat, fractionating the evolved vapors from the coking operation to separate intermediate constituents from higher boiling and lower boiling constituents, directing said intermediate constituents obtained from the thermal cracking and coking operations to the catalytic cracking zone, directing higher boiling constituents obtained from the thermal cracking and coking operations to a recycling thermal cracking zone wherein the oil is subjected to cracking conditions of temperature and pressure to eiect thermal cracking, separating the latter thermally cracked products into vapors and residue, fractionating the latter separated vapors to separate a reflux condensate from lighter fractions, and passing said reflux condensate to the recycling thermal cracking zone.

8. In the conversion of hydrocarbon oils, the process that comprises subjecting a straight-run condensate -stoek to catalytic cracking, fractionating the resultant cracked products to separate higher boiling constituents from lower boiling products, passing such higher boiling constituents to a single-pass thermal cracking zone wherein the oil is subjected to conditions of temperature and pressure to eiect thermal cracking, separating the resultant thermally cracked prod-4 ucts into vapors and residue, fractionating the separated vapors to separate intermediate constituents from higher boiling and lower boiling constituents, subjecting a petroleum residual charging stock to coking by passing it through a heating zone wherein the stock is subjected to a cracking temperature and discharging it into a coking chamber maintained under a pressure below 50 pounds and wherein conversion to coke occurs by means of contained heat, fractionating the evolved vapors from the coking operation to separate intermediate constituents from higher boiling and lower boiling constituents, directin said intermediate constituents obtained from the 'thermal cracking and coking operations to the catalytic cracking zone, directing higher boiling constituents obtained from the thermal cracg l and coking operations to a recycling thermal"

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