US2416608A - Catalytic conversion of oils - Google Patents

Description

Feb. 25, 1947.

.1. M. BRACKENBURY CATALYTIC CONVERSION OF OILS Filed July 31. 1944 2 Sheets-Sheet l' k cnbur l omwmm uc=omsw cE20u rwznfo r: John M. brac Dg hi5 AHornzg:

cE2ou wciao Feb. 25, 1947.

J. M. BRACK ENBURY CATALYTIC CONVERSION OF OILS 2 Sheets-Sheet 2 Filed July 31, 1944 lnvenior I John M Brackznbur Bg hi5 Aflornag! best obtainable quality.

portant of the available tools-at the refiners- Patented Feb. 25, 1947 UNITED STATE CATALYTIC CONVERSION OF OILS,

John M. Brackenbury, Oakland, Calif., assignor' to Shell Development Company, San Francisco, Callf., a corporation of Delaware Application July 31', 1944, Serial No. 547,445

This invention relates to. the catalytic conversion of hydrocarbon oils with finely divided catalysts in fluid catalyst systems wherein the finely divided catalyst is continuously recycled through a conversion zone'and through a separate regeneration zone. A particular aspect of the inven-' tion relates to the catalytic cracking of various hydrocarbon oils to produce valuable normally gaseous and normally liquid hydrocarbon products of lower molecular weight. A preferred modification of the invention relates to a combination process for the treatment of petroleum by the means of which superior Diesel fuels and fuel oils may be produced without sacrifice in the production of quality gasoline.

The nature of the invention may be most conveniently set forth by first describing a specifi preferred modification thereof.

When petroleum oil is received at the refinery the gases and so-called straight run gasoline are removed leaving a. partly reduced crude. The refiner is then faced with the problem of pro- .6 Claims (Cl. 196-'-50) .2 I I V secondary products or treated by thermal methods, although ina few cases they are catalytically cracked along with the light gas oil. Also, the bottom fraction, or reduced crude cannot be com pletely vaporized and is not suited for vapor phase catalytic cracking. In practice the gas oil and .stoveoil are removed as completely as possible under ordinary fractionation conditions to leave a reduced'crude which is suitable for use as fuel ducing the maximum quantity of qualityproducts from this partly reduced crude. One of the considerable effort and attention has therefore been given to various ways and means for producing the maximum uantity of gasoline of the One of the most imdisposal is catalytic cracking. Due to the large demand for gasoline, catalytic cracking is becoming almost universally used. Even with the 1 best means available, however, it is not practical to convert all of this partly reduced crude to gasoline and there is left therefore a considerable volume of by-product materials of Jesser value. In the past the emphasis has been largely on the production of the maximum quantities of gasoline of the best quality and the byproducts formed or left have largely determined A eral the feeds preferred and used for catalytic cracking units are those fractions taken from the middle of the partly reduced crude. These fractions are of the nature of light gas oil or stove oil. The lower boiling components of the nature of heavy gasoline, naphtha and kerosene are more refractory and are generally used in oil- Ina few cases this reduced crude has been partl'yivaporized in 'a so-called contact vaporizer andthe vapors cracked along with'the gas oils:

of quality gasoline are generally produced,'but

only at the expense of the quantity and quality of various other petroleum products such as Diesel oil and fuel oil. A primary object of the particular modification of the invention about to be described is to provide a. method whereby the petroleum may be utilized to'better advantage by producing quality gasoline from the more refractory fractions of the partly reduced crude without sacrificing yield or quality of secondary products.

To the accomplishment of this and related objects the partly reduced crude is separated by fractional distillation into a naphtha (or heavy gasoline) fraction, a heavy reflux condensate including kerosene, gas oil and stove oil, and a reduced crude. The reduced crude is not however thermally cracked as is the general practice, but is subjected to a fiash distillation under reduced pressure to produce a heavy flashed condensate and a heavy tar residue. The naphtha fraction and the heavy flashed condensate are then simultaneously cracked catalytically. The naphtha and the heavy fiashed'condensate are both relatively refractory materials and are individually less suited for catalytic cracking than the intermediate gas oil and stove .oil fractions. It has been found, however, that these two refractory stocks may advantageously be catalytically cracked together under suitable conditions. By producing the major part of the cracked gasoline from these materials excellent yields of quality gasoline may be produced without sacrifice of taken or: via line l2.

quality Diesel fuel production and while afl'ording a superior fuel oil. However, because of the totally dif erent characters of these two feed stocks and the greater refractivity of the naphtha fractions the maximum eflicient production of gasoline is not obtained when cracking these mixed feeds simultaneously under the usual cracking conditions. The cracking of these two stocks simultaneously under optimum conditions is effected, according to the process of the present invention, as hereinafter described.

The process will be described in the following in connection with Figures I and II of the accompanying drawing in which this specific embodiment of the invention is set forth for purposes of illustration. In the accompanying drawing, Figure I is a simplified flow diagram wherein there is shown by means of diagrammatic figures, not drawn to scale, one suitable assembly of apparatus arranged for operation according to this particular embodiment of the invention. ure II is a diagrammatic illustration of a suitable reactor in section.

The charging stock is a crude petroleum or one from which the gasoline has been substantially removed. If a crude petroleum containing gasoline is used, the gasoline is preferably removed to leave a partly reduced crude havin an initial boiling point of at least 300 F. The feed is then separated by distillation into a naphtha fraction, 9. heavy reflux condensate and a reduced crude. The cut point between the naphtha and the reflux condensate may vary considerably, but is preferably between about 400 F. and 500 F.

.is charged by pump 2 to a stripping column 3 wherein gasoline and naphtha ar separated. The gasoline and naphtha are removed overhead In the modifil via line 4. Part of the condensate is returned as pheric pressure without substantial cracking are removed. Thqvarious products may be removed in a single stream or may be segregated into various fractions as desired. Thus, for example, in the arrangement shown, a heavy naphtha or kerosene fraction is removed via line H); a light gas oil fraction suitable for use as Dieselfuel is taken 01! via line I I; and a heavy gas oil fraction suitable for use as Diesel fuel or for stove oil is The bottom product is a reduced crude suitable for use as fuel oil.

The reduced crude is passed through heating coils in a suitable heater and then via line l3 and pressure .control valve l3a to a vacuum flash column M wherein it is vacuum flashed under conditions chosen to remove overhead from between about 40% and about 75% of a heavy flashed condensate having a molecular weight between about 2'70 and about 350. One set of typical conditions is, for example, a temperature of about 700 to 750 F. and 100 mm. absolute pressure. Steam may be injected via line It to aid in decreasing the residence time and prevent cracking. The flashing operation does not involve any appreciable amount of cracking. This is indicated by the average molecular weight of the flashed condensate. Thus, the average molecular weight of the flashed condensate when taking 45% overhead is about 280, and the average molecular weight when taking overhead is about 345. In general a condensate having an average molecular weight in this range is indicated. This flashed condensate, it is seen, represents the heaviest portion of the petroleum that can be vaporized with available equipment without substantial cracking. It is diflicult to vaporize, and invariably contains appreciable amounts of nitrogen compounds and other impurities.

The material removed from the bottom of the flash column I4 is a heavy viscous residue. This material is totally unsuited for fuel oil, but produces a superior fuel oil when combined with aromatic reflux condensate as hereinafter described.

In a preferred modification of the process of the invention the flashing operation is carried out under somewhat more severe conditions to effect a slight controlled amount of cracking. The

amount of. cracking is adjusted to give between about 50% and of a condensate having an average molecular weight between about 280 and 300. This may be and is preferably efiected with the formation of not more than 1% gas and not more than 1% of gasoline, i. e., normally liquid products boiling up to 405 F. This operation is effected at temperatures below about 840 F., for instance temperatures between about 780 F. and 800 F. The conditions of pressure and residence time to give this result cannot be stated with any degree ,of deflniteness due to the interrelation of these factors and the differences due to the particular petroleum source and apparatus effects. However, these conditions are adjusted in the known manner and may be readily arrived at in any particular case. The distillate obtained under such conditions is hereinafter referred to as flash cracked'condensate.

The naphtha fraction separated in column 5 is fed by line I to a suitable fluidized catalyst cracking reactor IT. This feed picks up and carries to the reactor a quantity of hot freshly regenerated catalyst from the standpipes l8 and IQ of the fluidized catalyst regenerator 20. In some cases the heat supplied by the hot freshly regenerated catalyst may be sufliclent to vaporize the naphtha and heat it to the .desired cracking temperature. The naphtha is however quite refractory and for best results is cracked at temperatures higher than those generally applied for the catalytic cracking of gas oils and similar stocks.

It is therefore generally necessary to preheat the naphtha feed prior to contacting it with the catalyst. ,Thus, the naphtha feed may .be passed through the coils of a suitable heater 2|- The naphtha containing suspended freshly regenerated catalyst is introduced into the fluidized catalyst reactor at or near the bottom in the conven- The preheated up and carried to the regenerator 20 by a stream] of regenerationgas entering via 'line 26. Spent V regeneration gas is withdrawn from the system by line- 21.

cracked products is passed, as a vapor substan-3 The mixture of cracked and ungasoline may be returned to the-column 29 for reflux. The remainder is withdrawn via line 33.

A heavy highly aromatic condensate'is removed via line 35, cooler 36, surge tank 31 and pump 38 and a heavy residue is removed vialine 34'. This heavy residue contains a small amount of catalyst and may be advantageously recycled back to the cracking reactor via-line 1. The condensate consists largely of highly refractory aromatic hydrocarbons produced in the cracking zone. This material is passed via line 39 to a tank 4| wherein it is blended with the hot vacuum flashed residue, coming from the vacuum flash column 14 via line 42. In view of the highly aromatic nature of the condensate it blends well with the veryv heavy.

vacuum flashed residue toproduce a stable and superior fuel'oil. Also due to its extreme .refrac small volume of material is capable of converting a relatively large volume of heavy vacuum flashed it requires only about 50 parts of the aromatic condensate to convert 100 parts of the heavy flashed residue into a superior 100 second (Say-' bolt-Furol-122 F.) fuel oil. When blended 1:1 the heavy flashed residue is converted to a-stable- 25 second (Saybolt-Furol-122 F.) fuel oilmeeting the Navy special grade specifications.

Figure II is a somewhat more detailed illustration of the fluid catalyst reactor IT. The naphtha and finely divided catalyst are introduced at the bottom via line 'I and the distributing manifold 45. Partially spent catalyst is withdrawn from the bottom via standpipes 24 and 25. The rates of addition and withdrawal of catalyst are so adjusted as to maintain in the reactor a substantial bed of the catalyst as illustrated. The rate of flow of vapors is so controlled that the catalyst is maintained in a pseudo liquid or fluidized state. The flashed condensate or flash cracked condensate entering via line 23 is injected into the fluidized bed of catalyst by means of a distributing manifold 46. The reactor at the height of the manifold 46 is preferably increased in diameter, as shown, so as to accommodate the increased volume of vapors contacting the upper half of the fluidized bed of catalyst. The space in the reactor above the catalyst bed is provided to allow separation of, suspended particles of the catalyst from the vapors leaving the catalyst bed.

A number of cyclone separators 4'! may advan- 65 tageously be provided in the upper disengaging space to afford a more complete removal of suspended catalyst pa'rticles. I l

The described embodiment of the invention .may be carried out using any of the solid refractory metal oxide or clay-type cracking catalysts.

Suitable catalysts are, ,for example, the synthetic 6 I mina-boric oxide, silica-alumina-boric oxide and silica gel promoted with one or more metal oxides adsorbed thereon. Also the natural or treated .1 clay catalysts such as material known as Filtrol comprise minor amounts of promoting compounds such as the oxides or sulfides of molybdenum, chromium, tungsten, vanadium and the like. These various cracking catalystsare not necessarily equivalent and by the proper choice of catalyst it is possible to obtain almost any desired balance of such factors asthe concentration of butylenes in the gaseous products, etc. A

balance of products particularly suitable for pres.. 1 5 entrefinery operation is obtained with the following proprietary cracking catalysts; boric oxide on peptized alumina, silica-alumina composite cracking catalysts, and. silica-magnesia composite cracking catalysts. r

As pointed out above the feed stocks cracked according to the described modification of the invention are relatively refractory, i. e., under normal cracking conditions such as used for cracking a clean naphthenic gas oil, the productivity of the two feeds are however different in nature. The nephtha feed is inherently refractory due to the relatively low molecular weight of the hydrocarbon constituents- The flashed condensate and flash cracked condensate on the other hand are composed of hydrocarbons of high molecular weight and the refractivity appears to be largely due to the presence of minor amounts of poisons such as nitrogen bases, etc.,

therefore actually less refractory than the naphtha and is preferably cracked under different conditions. According to the process of the invention such less refractory materials are cracked under the optimum temperature conditions for the combined feeds but at a higher space velocity. This is accomplished by supplying all or the major part of the hot, fresh catalyst with the more refractory naphtha and introducing .the 5 flashed condensate or flash cracked condensate at an intermediate point in the reaction zone as described. By control of the ratesof oil flow and/or by control of the depth of the bed of fluidized catalyst maintained in the reaction zone a soconslderable variation of the space velocities for the individual feeds may be obtained. Thus, the naphtha fraction may be cracked at a weight hourly space velocity of, for example, 0.4 to 2 pounds of oil per pound of catalyst per hour and the flashed condensate or flashv cracked condensate may be simultaneously cracked at a higher,

pounds of upon the characters of the individual feed stocks,

the space velocities employed, etc. These are adjusted in the known manner to afiord the desired results for the particular operation at hand. The approximate ranges of the individual conditions for general operation are as follows:

Temperature F 825-1100 Pressure .'...p. s. i. g. 10-100 Catalyst/oil weight ratio 10:1-30:1 Steam per cent of oll 0-25 The relative amounts of the light naphtha and flashed condensate available froma given petroleum depends upon the particular petroleum.

., the boiling range of the naphtha fraction, and

may be used. These materials may furthermore tion of gasoline would be quite low. The refrac which are invariably present. This material is the depth of flashing, In some cases the available refractory naphtha, of say 3213-450 ,F. boiling range, may be more than enough to form a satisfactory blend with and may vary considerably.

increase the amount of flashed condensate. In

general ratios of flashed condensate to naphtha of from about 1:1 to about 10:1 are preferred.

It is to be noted that according to the prevalent belief in the art, the described mixture of flashed condensate and light naphtha would not be considered a desirable feed for catalytic cracking.-

The light naphtha, it will be noted, contains appreciable quantities, and may even consist essentially, of hydrocarbons which can properly be considered as gasoline components. In fact, the

light naphtha could in many cases also be called a heavy straight run gasoline. When crackin gas oil, stove oil,/and similar intermediate distiilates, it is known that the presence of gasoline constituents in the feed is quite harmful. The

prevalent belief in the art is that such gasoline components should be absent from all catalytic cracking stocks. In the present process this harmful effect of gasoline components isnot noticed, and, on the contrary, the light naphtha in the present process is distinctly beneficial in certain respects. Thus, the naphtha fraction is quite refractory and is preferably cracked at high cracking temperatures. When this material is cracked alone it is difllcult to maintain the optimum high cracking temperatures. Onthe other hand the flash condensates and flash cracked 1 large amounts of coke are formed and the conversions are low, apparently due to the poisoning effect of these impurities. When, however, the

naphtha fraction and the flashed condensate or flash cracked condensate are cracked together these disadvantages tend to cancel each other,

to a certain extent. Thus, the naphtha tends to reduce the concentration of nitrogen bases, etc. and the flashed condensate tends to increase the thermore, the flashed condensates and flash cracked condensates are quite heavy and difficult to maintain entirely in the vapor phase without the use of a large amount of'steam. The relatively light naphtha acts as a diluent and is very beneflcial in this respect also.

The above described modification of the present process, it will be seen, allows the production of considerable yields of excellent Diesel fuel from pressure and under mild cracking conditions to produce a heavy residue and between 50% and 75% of a heavy flash cracked condensate having a molecular weight between about 280 and 300 with the formation of less than 1% gas and less than 1% gasoline, mixing said naphtha fraction with a finely divided cracking catalyst and con-- veying the mixture to the bottom of a cracking zone containing fluidized cracking catalyst, introducing at an intermediate point in said cracking zone said heavy flash cracked condensate thereby to simultaneously crack said naphtha at a relatively low space velocity and said heavy flash cracked condensate at a relatively high space velocity separating the cracked product into a gasoline fraction and a heavy aromatic condensate, and combining said heavy aromatic condensate with said heavy residue to produce fuel oil. a

2. In the production of useful products including gasoline and fuel oil from petroleum the process comprising separating the petroleum by distillation into a naphtha fraction boiling between 300 F. and 500 F., a heavy reflux condensate, and a reduced crude, subjecting the reduced crude to a flash distillation under reduced pressure and under mild cracking conditions to produce a heavy residue andbetween 50% and 75% of a flash cracked condensate having a molecular weight between about 280 and 300 with the formation of less than 1% of gas and less than 1% gasoline, passing said naphtha through a catalytic cracking zone in contact with a fiuidized finely divided cracking catalyst, introducing into the partly cracked naphtha in said cracking zone said heavy flash cracked condensate, thereby to simultaneously crack said heavy flash cracked condensate in the presence of partly crcaked naphtha, separating the cracked products into a gasoline fraction and a heavier aromatic condensate and combining said heavier aromatic condensate with said heavy flashed residue to produce fuel oil.

3. In the production of useful products includnig gasoline and fuel oil from petroleum, the process comprising separating the petroleum by distillation into a naphtha fraction boiling be tween about 320 F. and 450 F., a heavy reflux condensate, and a reduced crude, subjecting the reduced crude to a flash distillation under reduced pressure to produce a heavy residue and between 40% and 75% of a heavy flashed condensate having a molecular weight between about 270 and 350,

mixing said naphtha fraction with a finely divided the virgin naphtha without impairing the quantity or quality of gasoline produced. The gasoline is produced largely from the flashed condensate or flash cracked condensate while taking advantage of some gasoline production from the refractory naphtha and at the same time producing therefrom a refractory aromatic condensate which is compatible with flashed residue and flash cracked residue and may be used to convert these residues to superior fuel oils. Thus, the process allows the petroleum to be utilized to better advantage without sacrificing'yield or quality of secondary products.

cracking catalyst and conveying the mixture to the bottom of a cracking zone containing fluidized cracking catalyst, introducing at an intermediate point in said cracking zone said heavy flashed condensate, thereby to simultaneously crack said naphtha at a relatively low space velocity and said heavy flashed condensate at a relatively high space velocity, separating the cracked product into a gasolinefraction and a heavy aromatic condensate and combining said heavier aromatic condensate with said heavy residue to." produce fuel oil.

4. In the production of useful products including gasoline and fuel oil from petroleum, the

tween 300 F. and 500 F., a heavy reflux condensate, and a reduced crude, subjecting the reduced crude to a flash distillation under reduced pressure to produce a heavy residue and between about 40% and 75% of a heavy flashed condensate'having a molecular weight between about 270 and 350, passing said naphtha through a catalytic cracking zone in contact with a fluidized finely divided cracking catalyst, introducing into the partly cracked naphtha in said cracking zone said heavy flashed condensate, thereby to simultaneously catalytically crack said heavy flashed condensate in the presence of partly cracked naphtha, separating the cracked products into a gasoline fractionand a heavier aromatic condensate and combining said heavier aromatic condensate with said heavy flashed residue to duce fuel oil.

5. In the production of useful products including gasoline and fuel oil from petroleum, the process comprising separating the pe r m y distillation into a naphtha fraction boiling between about 320 F. and 450 F., a heavy reflux condensate, and a reduced crude, subjecting the reduced'crude to a flash distillation under reduced. pressure to produce a heavy flashed con-v densate and a heavy residue, mixing said naphtha fraction with a finely divided cracking catalyst and conveying the mixture to the bottom of a cracking zone containing fluidized cracking cataprolyst, introducing at an intermediate point in said.

cracking zone said heavy flashed condensate, thereby to simultaneously crack said naphtha at process comprising separating the petroleum by 'distillation into a naphtha fraction boiling bea relatively low space velocity and said heavy flashed condensate at a relatively high space velocity, separating the cracked product into a gasoline fraction and a heavy aromatic condensate and combining said heavier aromatic condensate with said heavier residue to produce fuel oil.

.6. In the productionof useful products including gasoline and fuel oil from petroleum, the process comprising separating the petroleum by distillation into a naphtha fractionboilingibetween 300 F. and 500 F., a heavy reflux condensate, and a reduced crude, subjecting the reduced crude to a flash distillation under reduced pressure to produce a heavy flashed condensate and a heavy flashed residue, passing said naphtha through a catalytic cracking zone in contact with a fluidized finely divided cracking catalyst, in-

troducing into the partly cracked naphtha in said cracking zone said heavy flashed condensate,

thereby to simultaneously catalytically crack said heavy flashed condensate in the presence of partly cracked naphtha, separating'the cracked products into a gasoline fraction and a heavier aromatic condensate, and combining said heavier aromatic condensate with said heavy flashed residue to produce fuel oil.

' JOHN M. BRACKENBURY.

, I REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Bailey Sept. 25. 1945

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