US2399751A - Process for producing aromatics - Google Patents

Description

May 7, 1946. w. J. MATTox 2,399,751

v PROCESS FR PRODUCING AROMATICS v Filed March'- 12, 1943 Cree/215:

Zarza y wf* r@ provided for withdrawing a selected fraction.

lwhich may be of relatively narrow boiling range or a full boiling gasoline. 'I'his fraction may be particularly suitable catalyst comprises` alumina,

composited with chromia or alumina composited with molybdena. It is understood that these catalysts are not necessarily equivalent in their activity for effecting the desired reaction. The temperatures normally employed with these catalysts are within the range of about 900 to about 1100 F. and preferably are between about 950 to about 1000 F. It is understood that the aromatization step includes not only the cyclization of the aliphatic hydrocarbons but also includes the dehydrogenation of any naphtlienic hydrocarbons contained in the charging stock to this step of the process.

The selected fraction to be separated from the products of the cracking and deolefination steps for processing in the successive step of the process will depend upon the flnal products desired. For example, if it is desired to produce primarily benzene as the final product of the process, the

fraction may comprise constituents boiling s'ubstantially within the range'of hydrocarbons containing seven carbon atoms to the molecule. Usually, however, the selected fraction will not be of supplied to the aromatization step of the process as will hereinafter be described in detail or all or a portion thereof may be withdrawn from the I process through an extension of line 4.

The material boiling abovethe selected frac'- tion may be withdrawn through line 6 and supplied to the cracking step of the process or, il

desired, the higher boiling material may be withof the process.

Cracking zone 9 may be either catalytic or noncatalytic as heretofore mentioned. If this zone,- is a non-catalytic cracking operatior`1,"the -total vhigher boiling material withdrawn through line 6 may be directed through lines 'I and 8 into zone 9 for conversion therein, When zone 'comprlses a catalytic cracking operation it' is preferable 4to supply a selected fraction'such as gas oil, which may be withdrawn lfrom zone 2v through line 5 and directed throughline 8 into zone 9 for conversion therein.

such narrow boiling range but will include constituents boiling above and below the particular hydrocarbons and may comprise for example.- a selected fraction boiling from about 185 to about 255 F. when toluene is the desired aromatic. If

motor fuels are the desired product, the vselected fraction may have a boiling range of from about 80 to 400 or even 500 F. more or less. Usually the boiling range of the fraction subjected to aromatization will be the same or of narrower boiling range than the fraction subjected to deoleiination. v

The olefin-containing charging stock to the deoleiination step of/ the process may suitably.

Aa non-catalytic operation.

'I'he invention is further explained, in connection with the attached diagrammatic flow drawing which illustrates one specific embodiment of v the invention.

Referring to the drawing. the charging stock in this case comprises crude oil and is introduced to the process through line I into separation zone 2 which may comprise -one or a plurality ofsuitable fractionation, distilling, absorbing andl separating zones whereby the material charged thereto may beseparated into the desired fractions.

Normally gaseous hydrocarbons may be withdrawn through line 3 from -zone 2. Line 4.15

Cracking zone 9 may comprise any ysuitable type of cracking operation. The products from zone 9 are directed throughline, I0 into separation zone II which may be similar to zone 2 as here-v tofore described. Line I 2 is provided for withdrawing normally gaseous hydrocarbons and any normally liquid hydrocarbons boiling lower than lthe components desired in the selected fraction which is withdrawn from vZone I I through line I3'. Line I4 is providedl for the withdrawal of material boiling above the components desired in the selected fraction,and all or a portion of the higher boiling material may suitably be recycled by way oiv lines I4, I5 and 4to'zone 9 for further conversion therein, while any material not so recycled may be withdrawn from the process through an extension of line Ill. I

The selected fractionvwithdrawn through line I 3is directed into deolennation zone I6 which may be of any suitable typeso that the products withdrawn therefrom will have a lower bromine number than the products introduced thereto. The

vbromine number of the products emitting from zone I6 is preferably reduced to less than half that of the charging stock supplied to zone I6. The reactions occurring in zone I6 are not completely understood but it is known thatthe products emitting therefrom will contain material vboiling :substantially within the same range as the chargwhich is withdrawn from zone I 8 through line 20. Products boiling above the selected fractionv are withdrawn from zone I8 through line 2| and may be removed from the process but preferably, in accordance with the features of the present invention, at least a portion'of the higher boiling material is directed through line 22 and recycled within the process for conversion into lower boilf 2 heretofore described.

aseavc'l fing aromatic hydrocarbons. This may be accomplishcd by directinga portion of :the higher boiling 'material through lines 22, 23 and Il into zone Ilv wherein they are separated with the higher boiling products of the cracking operation and 'recycled by way of lines il, I 5 and 8 to cracking zone 9,' or the higher boiling material 'withdrawn through line 2| may be supplied through lines 22, 2l, 1 and 8 directly to zone 9.

Deolenation zone I6 not only serves to 'reduce to 255 F. and a bromi'rle number oi'77,'was separated 4from the products 'ofthermal cracking.'

th bromine number of the selected fraction but also serves to produce higherboiling aromatic hydrocarbons. which higher boiling aromatic hydrocarbons are recycled toi the cracking step and therein converted into vadditional quantities of lower boiling aromatic hydrocarbons desired as the ilnal product o f the process. Thus the dev sired aromatic hydrocarbons.

The selected fraction withdrawn through line 20' from zone` I9- ,is directed into 'aromatization zone 25.' When desired,V theselected fraction withdrawn through line 4 from zone 2 may be directedv through line 28 'into zone 25 for con' version therein -in commingled state with the "sel oleination step serves to increase the yieldof de- Eramp'le I A riaphtha having a boiling range of Vfrom -184 This-cracked naphtha was subjected to vdeolefina'- tion at a temperature 0155271 F. under a pressure of 800 pounds per square 4inch in the presence of a solid phosphoric acid cata1yst.` The liquid products recovered amounted to 97.3% by weight of the-chargearld these liquid products 'were fractionated to separate 58.5% by volume ofa selyst.-

i' the cracked naphthawithout thedeoleiina-tion lected fraction introduced thereto through' Vlirle 20. -Aromatization' zone 25 may be of any suitable type in order to effect the desired reaction.` The exact conditions of operation will depend uponv the particular selected -fraction introducedl through 'line 20, but the' condition of operation will be within then-ange heretoiore S'Pecied. The aromatization products are withdrawnjrom zone 2 5 through line 26f andaredirectedinto separation zone 21 which may'be'similar to zone Normally gaseous hydrocarbons may be vwithdrawn from zone. 21 through line 28:and may be' removed from the process or,'when desired. a

regulated'portionof these gases may be recycled by Way of dines 29 and 30 to zone.2ll. This re- 'cycling is usually employed when itis desired to conduct the aromatization stepin the presence of hydrogen. similarto' the process now known as lllydrofoi'ming. Hydrogen from an extraneous..

source may be introduced to this step or the process through an extension of line 30. When desired, the gaseous products withdrawn through line 28 may be subjected to'` any suitable pretreatment not illustrated in order to concentrate the hydrogen prior to recycling to zone25. It is also within the scope of' the invention to separate the hydrogen from the. gaseous products Jvwithdrawn through line l2 from zone H andsupply allor 'a portion of the hydrogen so separated to zone 25, as desired.

Material boiling above the range or motorffuel is withdrawn from zone 21 through line 29' and pretreatment was subjected toaroma-tizationfunf der the same conditions as ,described 'above 'I'he results of aromatization for both theuntreated and. the pretreatednaphthasare summarized be-v v low:

- untreated Treated naplltha naphtha Naphtha: y w

Boiling range, F. '184-255 185-254 Bromine number 77 l Yields, weight r cent of charge:

Total llqui hydrocarbons l 83.7 85 Gas 6.8 6 Carbon 11.2 5.

Grams, aromaties per gramof carbon.. 1.97 3.42 Aromatic fraction:

Boiling range, F' L '.r 122-275 122-279 w Weight .per cent ci totalliqy d recovery'. 94. 4 95.3 Weight per cent oi charge.; 79.0 81. 4

It is thus seen that the carbon produced during the aromatization step was 5.96% for the deole nated naphtha as compared to"11 .2 for the untreated naphtha.I

' Example II Y v JA crackednaphtha having a boiling range of 185 to 251i F. anda' bromine number of '77 was subiectedjto de olefination in the presence of a silicaalumina. catalyst at a 'temperature-of 572 F. under apressureof -900 pounds per square inch ing a boilingr range of' 185 to 257 F.and a bropreferably all or a portion thereof is recycledby 4 way of lines 24,'1 and 8 to crackingzonec for further conversion therein.

Line 32 is provided for desired to separate several particular. aromatic hydrocarbons as well as motor fuel, it is underthe 'withdrawal of selectea aromatic hydrocarbons'suchas benzene,

toluene, etc., from zone 21, whllefline 3l is provided for the'withdrawal of motor fuel. "II it is high yields of toluene.

-to yield' liquid products amounting' to over 99% byA weight ofl the charge. A selected fraction havmine number of 2 may be' separatedfrom the.

products of saiddeolefination 4and vmay then be subjected to aromatization' in the presence-oan aluminafchromia 'catalyst atatemperature`- of 980 F. under atmospheric I claim as my uivention:

1 A. process for producing aromatics 4which' comprises cracking hydrocarbon oil and separat-i' 4ing from the resultant cracked "products a dis# stood that the separation may be effected either in zone-21 or by any other suitable separation means. Y Thearomatieqhydrocarbons so separated will be of high purity, and-the motor fuel so sep i'lratedfwillY be of 'high aromaticcontent and oi?v low bremine number, and'thus'will lle-,particularly suitable for use in gasoline. 1

thep'roduction of aviation ltillate containing param'nic and olefinic 'hydrocarborls` having-'at least six carbon atoms in straight ychainarrangement, reducing'the'bromine number'oi said distillate b'y converting ole nns present therein into non-'olefinic hydrocar.- l

-' bons boiling, substantially/within the range ci 'said distillate and also inte hisnelf'bollmgerematic hydrocarbons, fractionating the distillatelto separateJ said 4higher boilingfaromatic hydro- The following examples are introduced for the i purpose of furtherillustrating thel novelty and utility ofthe present invention-but not with-the'- intention of unduly limiting the same.

For comparative purposes, anothersa mple of salaspressure to produce carbons therefrom and supplying at least a portion ofthe latter to the cracking step, andv subjecting, the fractionated distillate to aromatization in the\presence of an aromatizing catalyst under conditions such as to convert parans to aromatics.

2. The process as deiined in claim 1 wherein said olefin conversion treatment is conducted in the presence of a. phosphoric acid catalyst at a temperature of from about 250 to about 750 F.

3. The processlas defined in claim 1 wherein said olefin conversion treatment` is conducted in the presence of a catalyst containing silicaand alumina at a temperature of from about 400 to about 1000u F. Y

4. A process for producing toluene which comprises cracking hydrocarbon oil and separating from the resultant cracked products an olenic distillate boiling inthe range of from about 185 F. to about 255 F., reducing the bromine number of said distillate by converting olens present therein into non-oleiinic hydrocarbons boiling e. substantially within the range of said distillate7 and also into higher boiling aromatic hydrocarbons, fractionating the distillate to separate said higher boiling aromatic hydrocarbons therefrom and supplying at least a portion of the latter to the cracking step, and subjecting the fractionated distillate to aromatization in the presence of an aromatizing catalyst under conditions such as to convert parailns to aromatics.

5. A process for producing aromatics from crude oil which comprises fractionating the crude to separate therefrom a fraction boiling in the gasoline range and a fraction heavier than gasoline, cracking the last-mentioned fraction and separating from the resultant cracked products a. distillate containing paraflinic and olenic hydrocarbons having at least six carbon atoms in straight chain arrangement, reducing the bromine number of said distillate by`converting olens present therein into non-oleflnic hydrocarbons boiling substantially within the range of said distillate and also into higher boiling aromatic hydrocarbons, fractionating the distillate to separate said higher boiling aromatic hydrocarbons therefrom and supplying at least portion of the latter to the cracking step, commingling the fractionated distillate with said fraction boiling in the gasoline range, and subjecting the resultant mixture to the action of an aromatization catalyst under parain aromatizing conditions.

WILLIAM J. MATTOX.

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