US2308557A - Cracking process - Google Patents

Description

K. mwA'rsoN CRACKING PROCESS Filed sept. 2o, 1940 Jan. 19, 1943.

m, wm kuk um W Patented Jan. 19, 1943 CRACKING PROCESS Kenneth M. Watson, Chicago, Ill., assgnor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application September 20, 1940, Serial No. 357,523 7 claims. (cl. 19o-49) This invention relates to a process for converting hydrocarbon oil into substantial yields of gasoline and gas. More particularly it relates to the cracking of hydrocarbon fractions in the presence of a powdered catalyst to produce substantial yields of high antiknock gasoline.

The charging stock used in the present invention is normally from petroleum sources and includes distillate fractions of straight run and cracked hydrocarbon oils such as kerosene, gas oil, wax distillate and the like, as well as higher boiling fractions including topped crude oil, reduced crude oil, etc. Similar suitable charging stocks from other hydrocarbon sources may also be converted.

In one specific embodiment the present invention comprises treating a distillate fraction of hydrocarbon oil in a primary' cracking step with a powdered catalytic agent under cracking conditions of temperature and under a pressure adequate to maintain a major portion of the oil boiling above the gasoline range substantially in liquid phase, continuously recycling a portion of said oil containing catalyst in suspension to the catalytic reaction zone, passing a second portion of liquid reaction products substantially separated from said catalyst to a secondary cracking step wherein it is subjected to further treatment with a powdered cracking catalyst together with a higher boiling fraction of hydrocarbon oil ythan is used in said primary cracking step, continuing said treatment at a cracking temperature and under pressure adequate to maintain higher boiling reaction products substantially in liquid phase, separating and recycling a portion of said catalyst suspended in oil, separating a further fraction substantially free of catalyst, subjecting it to a vaporizing step and returning a portion of the vapors therefrom for further cracking in said primary step, separately fractionating the vaporous reaction products 'from said primary and said secondary stepsv and recovering the gasoline and gas formed.

The invention is further 'understood by reference to the accompanying drawing which is diagrammatic and should not be interpreted as limiting the process unduly.

A hydrocarbon oil fraction which may comprise a distillate fraction of petroleum oil such as naphtha, kerosene. gas oil, wax distillate, etc., is introduced to the primary cracking step through line I, valve 2, pump 3 and valve d to coil 5 which is contained in heater 6. A powtitanium, etc.

valve II. The quantity of catalyst introduced may be from approximately 0.1-10% by weight of the charge. and is preferably of the order of 0.12% although larger amounts may be used, for example, up to 10%. Any suitable cracking catalyst powder may be used, such as, for example, silica-alumina, silica-zirconia, silica-alumina-zirconia and similar catalysts 4as such or having deposited thereon relatively minor quantities of promoting compounds such as an oxide of chromium, molybdenum, tungsten, uranium,

the separate or simultaneous precipitation of the components under conditions such that a powder approaching colloidal dimensions is obtained. The powder may be further washed to remove sodium compounds.

Another type of catalyst which may be used comprises a relatively inert carrier such as alumina, silica, magnesia, titania, zinc oxide and* 'the range of approximately 500-1200 F. and pressure from approximately 50-1000-pounds per dered catalytic agent is introduced from catalyst i charger 'I through line 8, valve 9, pump I0 and square inch or higher. The heated products pass through line I2 and valve I3 to reaction chamber I4. The reactor is normally maintained at a temperature within the range of approximately 500-1200 F., the pressure being adequate to maintain a major portion of the liquid reaction products boiling above the' gasoline range substantially in liquid phase. A vaporous fraction consisting substantially of gasoline and gas i is removed through line I5 and valve I6 to fractionator II, from which gas and gasoline are recovered, through line I8 containing valve I9, condenser 20 and valve 2|. The gasoline is collected in receiver 22 and may b' removed to-a suitable stabilizer through line 23 containing valve 24. Receiver gases are passed to a gas recovery system through line 25 and valve 26. Higher boiling oil may' be withdrawn through line 21 and valve 28, but is normally recycled through line30, valve 3l, pump 32 and valve 33, Joining .with the charging stock to the primary These catalysts are prepared by Still another type `of catalyst is cracking step in line A portion of liquid reaction products are removed from reaction chamber I4 through line 34 and valve 35 to separator 36. This comprises a settling chamber maintained at superatmospheric temperature wherein the powdered catalyst is allowed to -settle and concentrate in a portion of the reaction products which are withdrawn through line 31, valve 38 and pump 39, a. portion being returned to the reaction zone through line 40 and valve 4| in order to build up and maintain a higher percentage of catalyst in the reaction zone than is charged with the incoming oil. A portion ofthe oil containing catalyst in suspension is remoyed through line 42 and valve 43 to a suitable catalyst recovery system. The catalyst may then be reactivated by contact with an oxygen-containing gas and may be used in this or in the secondary cracking step about to be described for further converting hydrocarbon oil to gasoline.

The portion of oil at the top of the settler, being substantially free of catalyst, is passed through line 44 containing valve 45, pump 46 and valve 41, joining with line 48 containing valve 49 and being passed to coil 50 Which is disposed in heater' 5|. The oil is mixed with the charging stock for the secondary cracking step, l

entering through line 52 containing valve 53, pump 54, and valve 55. Powdered catalytic agent is introduced from catalyst charger 56 through line 51, valve 58, pump 59 and valve 60. The catalytic agent used in this step may, as previously indicated, be a portion of the reactivated catalyst from the primary step or may comprise any one of the catalysts previously mentioned or a mixture of such catalysts. It need not be the same catalyst employed in the primary step. Thus, for example, the highly active silicaalumina type catalyst may be used in the primary step for converting gas oil, While a less reactive catalyst such as a naturally-occurring earth may be used in the secondary cracking step. Furthermore, a catalyst Which has been used a number of times in the primary step and has been reduced in activity, may be used in the secondary cracking step. The conditions of cracking employed in the secondaryv cracking step are somewhat milder than those used in the primary step b ecause of the heavy character of the charging stock which may comprise heavy distillate fractions or such fractions of crude petroleum oil as topped crude oil orvreduced crude oil. The temperature is Within the range of approximately 500-1000 F. or slightly higher and the pressure is within the: range of approximately 50-1000 pounds per square inch, being, as in the primary step, adequate to maintain a substantial portionof the reactants in liquid phase.

The mixture passes through line 6| and valve 62 to reaction chamber 63, which is maintained within the region specified and vaporous reactants containing substantial quantities of gasoline may be removed through line 64 and valve 65 to fractionator 66. The gasoline and gas are recovered through line 61, valve 68, condenser 69 and valve 10, entering receiver 1.| from which the gasoline may be removed through line 12 and valve 13 to a suitable stabilizer not shown. Receiver gases may be removed to a gas recovery system not shown through line 14 and valve 15. The fraction boiling above the gasoline range is passed through line 16, valve 11, and valve 11 to line 48 containing pump 18 and thus returned through valve 49 to coil 50./ Liquid reaction prodl ucts are removed from reaction chamber 63 through line 19 and valve 80 to separator 8|. As in the case of separator 36, the catalyst separates by gravity, concentrating in the oil in the lower part of the separator. A portion may be removed through line 82 containing valve 83 and pump 84, being' recycled through line 85 and valve 86 to the reaction chamber in order to build up the amount of catalyst therein from the amount charged which is of the order of 0.1-l0%. A portion of oil may be removed through line 81 and valve 88, the catalyst being recovered therefrom and separately reactivated or discarded as the case may be. The portion of liquid reactants substantially free of catalyst is removed through line 89, valve 90, heater 9| and valve 92 to vaporizing chamber 93. A residue unsuitable i or further conversion maybe withdrawn through line 94 containing valve 95. The'vaporous fraction is removed through line 96 and may be recycled in part through line 91 containing valve 98 joining with line 48 and thus being returned to the coil. An additional quantity of oil suitable for fuel purposes may be removed through line 99 and valve |00.

As an alternative, a. portion of the reactants from lines 16 and 91 may be passed through line |0| containing valve |02, pump |03 and valve |04 to line 30l and thus passed to the primary crackingstep.

The following example is given to illustrate the practicability of the process, but should not be construed as limiting it to the exact conditions, catalysts, or oils indicated therein.

When cracking gas oil in the primary cracking step and reduced crude oil in the secondary cracking step at a temperature of 975 and 850 F., respectively, a total yield of of cracked gasoline having an octane number of 78 may be obtained. In addition, relatively minor amounts of products valuable for fuel purposes are produced.` `The catalyst employed in the primary cracking step may comprise silica-alumina and that employed in the secondary cracking step may be a naturally-occurring earth which has been ac- 3 tivated by treatment with mineral acid.

I claim as my invention:

1. A conversion process which comprises cracking hydrocarbon distillate in admixture with powdered cracking catalyst under suicient pressure to maintain a substantial portion of the hydrocarbons in liquid phase, independently cracking a hydrocarbon oil of higher boiling point than said distillate in admixture with powdered cracking catalyst and under suilicient pressure to maintain a substantial liquid phase, separating from the unvaporized products of the firstnamed cracking step a light residual oil substantially free of catalyst and supplying the same to the second-mentioned cracking step, separating from the unvaporized products of the second-mentioned cracking step a hydrocarbon fraction substantially free of catalyst, supplying at least a portion of said fraction to the rstnamed cracking step, and recovering gasoline from the vaporous products of said cracking s eps.

2. The process as dened in claim 1 further characterized in that said fraction is subjected to vaporization and hydrocarbons thus vaporized supplied to said iirst-named cracking step.

3. A conversion process which comprises cracking hydrocarbon distillate in admixture with powdered cracking catalyst under sufficient pressure to maintain a substantial portion of the hydrocarbons in liquid phase, independently cracking a hydrocarbon oil of higher boiling point than said distillate in admixture with powdered cracking catalyst and under sumcient pressure to maintain a substantial liquid phase, separating from the unvaporized products oi' the firstnamed cracking tially free oi' catalyst and supplying the same to the second-mentioned cracking step,V separating from the unvaporized products of the secondmentioned cracking step a, hydrocarbon fraction substantially free of catalyst, vaporizing a portion of said fraction and supplying resultant va- Dors to the tiret-named crackingx step, and recovering gasoline from the vaporous products of said cracking steps.

4. A process for converting hydrocarbon oil into substantial yields oi gasoline which comprises treating a lower boiling fraction of hydrocarbon oil in a primary cracking step with a powdered catalytic agent under cracking conditions of temperature and a pressure adequate to maintain a substantial portion of oil boiling above the gasoline range in liquid phase. recovering gasoline and gas, subjecting thev liquid fraction of conversion products containing catalyst in suspension to a separating step, recycling to said primary step a portion or said liquid fraction containing catalyst in suspension, passing a further portion oi said liquid fraction substantially free of catalyst to a secondary cracking step together with a ,higher boiling fraction of petroleum oil and a powdered catalytic agent, maintaining the mixture at catalytic cracking conditions oi. temperature and under pressure adequate to maintain a substantial portion of higher boiling reactants in liquid phase, recovering gas and gasoline therefrom, subjecting unvaporized products of the secondary cracking to a separatingstep, recycling to said secondary crackingstep a portion of said unvaporized products containing catalyst in suspension, Apassing a por-,1.-v

tion of saidv unvaporized products substantially free of catalyst; to a vaporizing zone, withdrawing a residual fraction unsuitable for i'urther conversion and supplying hydrocarbons VDOl'iZed in said vaporizing zone to at least one oi' said cracking steps.

step alight residual oil substanl 3 5. A process for converting hydrocarbon oil into substantial yields oi' gasoline which com.

` aforesaid primary cracking step for further con? vpetroleum oil and a cracking prises treating a lower boiling fraction of hydrocarbon oil in a primary cracking step with a powder ed catalytic agent under cracking conditions o .temperature and a pressure adequate to mainta a substantial portion of voil boiling above the gasoline range in liquid phase, recovering gasoline and gas, subjecting the liquid traction of conversion products containing catalyst in suspension to a separating step, recycling to said primary step a portion of said liquid fraction containing catalyst in suspension, passing a further portion of said liquid fractions substantially free of catalyst to a secondary cracking step together with a higher boiling fraction of powdered catalytic agent, maintaining the mixture at catalytic cracking conditions oi' temperature and under pressure adequate to maintain a substantial portion of higher boiling reactants in liquid phase, recovering gas and gasoline therefrom, subjecting unvaporized products o! the secondary cracking to a separating step. recycling to said secondary cracking step a portion oi' said unvaporized products containing catalyst in suspension, passing a portion oi' said unvaporized products substantially free of' catalyst to a vaporizing zone, withdrawing a residual fraction unsuitable for further conversion and passing at least a portion of the vaporized product from said vaporimng zone to the version.

6. The process as set forth in claim 4 wherein the catalytic agent employed in the primary step has greater activity than that employed in the secondary cracking step.

7. The process as set forth in claim 4 wherein the temperature employed in the primary cracking step is from about 500 to about 1200 F., and the temperature employed in the secondary cracking step is from about 500 to about 1000 F., the pressures in each step being from about to about 1000 pounds per square inch.

KENNETH M. WATSON,

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