US2405660A

US2405660A - Method of producing toluene

Info

Publication number: US2405660A
Application number: US462323A
Authority: US
Inventors: Norman F Linn
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1942-10-17
Filing date: 1942-10-17
Publication date: 1946-08-13
Anticipated expiration: 1963-08-13

Description

Allg. 1.3, 1945." v N F |NN l 2,405,660

METHOD OF PRODUCING'l TOLUENE Filed Oct. 17, 1942 2 Sheets-Sheet l mxocsn 5 7; 88 5o 5 mw .if

N. F. LINN @940,650

' METHOD oF PRoDUcING TOLUENE l Filed oct. 17,1942 2 sheets-sheet 2 Patented Aug. 13, 1946 METHOD OF PRODUCING TOLUENE Norman F. Linn, Mountainside, N. J., assignor to Standard Oil Development Company, a corporation of Delaware Application October 17, 1942, Serial No. 462,323

3 Claims.

The-present invention is directed toward the production of automotive fuel and, more particularly, it relates to a method of improving a hydrocarbon oil boiling in the naphtha and/or gas oil range, particularly as regards octane number, which naphtha or gas oi1 is of the Fischer type. By Fischer type naphtha or gas oil, I refer to hydrocarbons synthesized from CO and Hz in the presence of a known suitable catalyst and under known conditions of temperature, pressure, etc.`

As is generally known, hydrocarbons may be Fischer synthesized in the presence of suitable catalysts such as iron, nickel or cobalt either alone or deposited on a carrier such as kieselguhr or kaolin. This may be promoted and stabilized by alkalies and manganese and copper. These products, however, have a very low octane number since they are largely composed of normal parafns. Broadly speaking, my invention comprises improving the octane rating of such a hydrocarbon oil by subjecting it to a combined hydroforming, solvent extracting and catalytic cracking operation. It is also concerned with the production of substantially pure aromatics, e. g. toluene of so-calledl nitration grade. by subjecting selected fractions to a combination of processes which will be more Vcompletely described below. By hydroforming I mean to imply an operation in which the treated oil is subjected to elevated temperatures, say of the order of 9001000 F. and pressures of 10D-400 lbs. per square inch and in the presence of a catalyst, chromia or molybdena alone or supported on activated alumina, orother VI group oxide or a mixture of suldes, such as nickel and tungsten suldes, and also employed in the presence of added hydrogen. The hydroforming operation is, for the most part, one of dehydrogenation With the formation of aromatics and olens from paraiiins, accompanied also by some cyclization of paraiiins, aromatization, isomerization and cracking of parafns, but the operation generally is conducted under conditions such that there is a minimum changein the boiling range of the charging oil.

In the accompanying drawings, vIl have indicated diagrammatically a flow plan illustrating a preferred modification of my invention.

Referring tothe drawings fora better understanding of my invention, a Fischer synthetic Ahydrocarbon is introduced'into the present System through line l and thence distilled in a fractionator 3 into anv overhead fraction boil-k fraction is withdrawn through line 5, condensed in a cooler I and thence discharged through line 8 into a naphtha storage Vessel l0.

The bottoms from distillation zone 3 and boiling say from 440-650o F. are Withdrawn through line I5, condensed in a cooler Il, thence discharged through line I9 into a gas oil storage vessel 20.

The overhead fraction and the gas oil bottoms from the distillation zone 3 are treated as will be lmore fully explained hereinafter. At the outset it is explained that the naphtha is subjected to reforming in the presence of hydrogen, While the gas oil is cracked. The reforming operation results in the production of aromatics which may be solventl extracted to recover, for example, toluene with a degree of purity suitable for nitration.. The gas oil cracking also results in the production of an automotive fuel of high octane number, together with toluene of a high degree of purity.

Continuing the description of the process shown in the drawings, the naphtha in storage vessel I0 is 'Withdrawn through a line 35 and thence discharged into a heater 32, which may be a furnace or other suitable heating means, Where it is heated to reaction conditions, thence l discharged through line 35 into a reactor 45 containing a catalyst ofthe type previously indicated. Hydrogen from 50 is Withdrawn through line 52, heated in a red coil or other heating means `53, and thence discharged through line into reactor 40 so it is present with the oil undergoing treatment. vWith respect to operating conditions, the following give good results:

Hydrogen proportion is in the range of from say 2000-4000 cubic feet per barrel of cold oil. Under these conditions the naphtha undergoes reforming, and the reformed products are withdrawn through line and discharged through Within the range of fromvlZS-fize 1F., which .5 5 a cooler 62. and thence discharged'through line 13G-210 F. and representing about 44 volume' per cent of the oil in line 853 is withdrawn f through line 38 and discharged after cooling into condenser 90 and thencefintoa gasoline storage vessel |80. The bottoms fraction'representing about 39 volume per cent of the product fed to the fractionator 55 is Withdrawn'through line 55, condensed in a cooler 97 and thence discharged into line 88 where it mixes with the lighter ends from the iractionator and ow's with the latter into gasoline storage vessel |00. Thus from the reforming omration, the lighter and heavier ends are recovered as gasoline blending agents.

Referring again to fractionator 85, a side cut representing about 17% of materialcharged to `85 and boiling within the range of from about 21d-259 F. is withdrawn as a side stream through line 55; This fraction is purified by solvent treatment, preferably, although other means may be employed. Thus, for example, thissfraction contains normally not only the toluene, but also parailins boiling within the range of 21e-250 F. and a minor amount of oleiins also boiling within this range, although the' presence of hydrogenf tends to saturate olens formed in reactor Ml, so that the final result of the reforming operation is to producej parafns andaromatics. As

i indicated, these paraiiins in the vboiling range of from 210-250 F. may be removed',y for instance,

by cracking them to products -whichwill boil lower` than the toluene so that aftercracking, the toluene maybeseparated kby simple distillation. In the drawings, however, I have shown solvent treating employing SO2 as the selectiveV solvent forthe aromatics. Toward this end, the

` SO2 is withdrawn from lthe source illand dischargedl intothe top of solvent extraction Vessel |5 Where it flows-countercurrently to the hydrocarbon oil fraction entering from 55. f Asa further aid to the process, a paraftlnicwash solvent such aspentane isV withdrawnffrom the storage vessel |25- andv discharged-through line z$22 into solvent extraction tower H5 ofcourse, in sol- "Vent extraction tower ||5 the usual formation of raffinate and extract phases takes place. 4The raffinate phase is withdrawn through line and discharged into a stripping tower |35. This rainate is stripped to remove the SO2 which is withdrawn through line |45 and pumped by pump |1i2 to storage vessel lill. The bottoms from stripper are withdrawn through line |45 and discharged into fractionating column |41. The overhead fraction comprising the paraiiinic wash vsolvent is Withdrawn from the fractionator |47 through line |49, condensed in condenser |55, vthence pumped backv through line |5| to the parafn storage .|2ll.. The bottoms from fractionator |41 are Withdrawn through line |55 and 'discharged into line |51 leading to gasoline stor` age vessel |55. The bottoms Withdrawn `from Yfractionator Ml through line |55 maybe discharged through line |55 to either the reforming lzone 4i) or the 'cracking zone 320. -I As previouslyindicated, there is"an"'e'Xtract 4 phase formed in extraction vessel ||5 and this is Withdrawn through line |69 and discharged into stripper |52 where the solvent is removed by distillation, withdrawn through line |63 and pumped by pump |54 into storage vessel I Hl. The substantially solvent-free extract is Withdrawn from stripper |62 through line |15 and discharged into.y a fractionating column |15.- The parafns still remaining or associated with the toluene cut are withdrawn through line |85, condensed in a condenser |32 and thence discharged through line |83 into paraninc wash solvent storage |20. The toluene is recovered from fractionator |75 through line and thence discharged into an acid treating vessel |92 where it is treated preferably with sulfuric acid of polymerizing strength, such as about 65% by Weight, or it may be treated with` a polymerizing clay to polymerize the olei'lns to convert them to heavier polymers which may be separated from the toluene by distillation. The thus treated material is Withdrawn through line |95 and discharged into fractionator 28|] from which lighter ends may be withdrawn through line 2id, While the heavier polymers are withdrawn through line 2 2. The desired toluene is withdrawn as a side stream through line 265 and delivered into a toluene storage vessel 258. The toluene in 268 has a degree of purity suii'icient for making trnitrotoluene or any other product requiring a high degree of purity. A

Referring to the heavy bottoms of the original Fischer product, it will be recalled that these were collected in storage drum 25. This material is to be subjected to-catalytic cracking and towards this end it is withdrawn through vline 350, discharged into a suitable fired coil or other heating means 3|0 where it is heated to cracking temperatures, say from S25-925 F. and thence withdrawn through line 3|2 and discharged into a catalytic cracking reactor 325 where it contacts a cracking catalyst such as an acid treated montmorillonite clay or a synthetic cracking catalyst consisting vof silica :and alumina or silica and magnesia. The catalysts,- as Well as cracking conditions for this operation are known to the art. Normally good results are obtained by operating ata temperature of 875 F; andat a relatively low pressure and permitting Ycontactbetween the catalyst and oil vapors at-reaction temperatures of from 15-25 seconds or more. Under these A- conditions the gas oil undergoes cracking to form catalytically cracked gasoline in good yields thereof amounting to 35-4070. The cracked products are withdrawn through line 335 and discharged into fractionating column 335. Unconverted gas is withdrawn from fractionator 335 through line 34B and thence discharged into storage Vessel 20 for further treatment. However, a portion vof this oil is Awithdrawn continuously through liney342, Yparticularly as it becomesincreasingly refractory, and the thus Withdrawn oil may be usedfor a heating oil or for some other purpose. The normally gaseous constituents are Withdrawn i overhead from fractionator 335 through line 358.

f 4`These gases contain butylene, isobutylene, normal butano and isobutane and they maybe processed `in means not illustrated to form by alkylation branchV k'chainV hydrocarbons boiling Within the gasoline range, or they may be'converted to syn- 'thetic rubber intermediates suchY as butadiene, or otherwise-rdisposedof.v q

A 'fraction boiling within the rangeolB` from "e-40|lfF. is withdrawn from fractionator 335 `throughiine-360 and discharged into a'fractonating 'column 310. AThe product entering 310 is divided preferably into three fractions as follows: first, an overhead fraction containing the lighter ends which is withdrawn through line 380 and condensed in a cooler 38| and thence discharged into stream 88 where it flows with the overhead from the reforming operation into gasoline storage vessel I. The bottoms from fractionator 310 may be withdrawn .through line 390, condensed in cooler 39| and also discharged into gasoline storage vessel |00. Finally, an intermediate cut boiling from 21o-250 F. and representing about 10% of the material discharged into fractionator 310 is Withdrawn as a side stream through line 400, and this may be discharged into line 99 to recover with the product from the reforming operation, its toluene content, in a manner which has already been described.

In an alternate modification, the intermediate cut boiling from 210-250 F. which is withdrawn from fractionator 310y through line 400 Vmay-be discharged into line |58 for ultimate reforming in zone G or passed through lines |56 and 305 to coil 3| and thereafter cracked.

Many modifications of the invention as above set forth may be made without departing from the spirit thereof. I have shown solvent extracting a toluene fraction with liquid sulfur dioxide. Instead of using this method, I may use another solvent such as phenol, in which operation the vapors to be extracted are treated with liquefied anhydrous phenol. This process or the process of extracting the liquid SO2 do not form per se the gist of my invention and any known method for recovering toluene by solvent extraction may be employed. If the solvent is SO2 the temperature maintained in the extraction zone I I5 should be from O to -60 F. or lower. The flow of SO2 with respect to the hydrocarbon should be from 1-3 parts by Weight of SO2 per weight of hydrocarbons and the volume of paraffinic wash solvent, for example, pentane from |20 should be from 1/2 to 11/2 volumes of the wash solvent per volume of liquid consisting of SO2 and the hydrocarbon in the extractor ||5.v Of course, it will be appreciated that in

reactors

40 and 320 the reactions therein taking place result in the deposition of cokey or tarry deposits on the catalyst and these operations must be interrupted intermittently to remove these deposits since they deactivate the catalyst. This can be accomplished in known manner by burning off the tarry or cokey deposits with an oxygen-containing gas.

In the foregoing disclosure, I have described my process in terms of fixed or stationary beds of catalyst. My process may be carried out using a suitable powdered catalyst suspended in the reaction vapors in the several reaction Zones. Thus, the reforming and/or cracking operations may be carried out by flowing the vapors to be cracked or reformed through a zone where they contact a uidized powdered catalyst which is suspended in said vapors.

Also, of course, in the operationsl described there will come a time when it is necessary to regenerate the catalyst in the reactionk zones. This may be accomplished, after discontinuing the flow of oil to the reaction Zones, by treating .the catalyst with an oxygen-containing gas, such as air, or air diluted with fiue gas, at temperatures elevated sufficiently to cause burning o-f the fouling deposits. This procedure is well known in the art. Where the catalyst in powdered form moves in and out of the reactors, it may be regenerated in separate regeneration zones and thus render the operation continuous.

Another ramification of my process as herein described involves -including the reproportionating of xylenes, formed during the reforming, with benzene in the presence of a suitable catalyst such as AlCla whereby additional quantities of toluene may be produced. The details of this process are generally known in the prior art.

What I claim is:

l. A method of producing toluene of high purity from a hydrocarbon product obtained by the hydrogenation of carbon monoxide which comprises fractionating the said hydrocarbon product into a naphtha fraction and a gas oil fraction, submitting the latter to a cracking treatment at a temperature of the order o f S25-925 F. in the presence of a catalyst suitable for promoting the cracking of aliphatic hydrocarbons, recovering a fraction boiling at about 210 to about 250 F. from the product of said cracking treatment, combining such fraction With the naphtha fraction obtained in the fractionation of the product of the hydrogenation of carbon monoxide, subjecting the combined `fractions to a reforming treatment at a temperature of the order of S50-1000 F. and under a pressure of the order of 1GO-400 lbs/sq. in. in the presence of hydrogen and a catalyst comprising an oxide of a group VI metal, recovering from the product of said treatment a fraction boiling at about 210 to about 250 F. and treating such fraction to selectively separate therefrom its aromatic content.

2. A process according to claim 1 in which the aromatic content of the fraction produced in the reforming treatment is separated therefrom by extraction with a solvent, followed by treatment of the extract phase with a parainic hydrocarbon solvent lighter than the parafnic hydrocarbon remaining in said extract phase to displace the latter, and distillation to remove the said lighter parafnic hydrocarbon solvent from the aromatic hydrocarbon product.

3. A'process according to claim 1 in which the aromatic content of the fraction produced in the reforming treatment is separated therefrom by extraction with a solvent, followed by treatment of the extract phase with pentane to displace the parafiinic hydrocarbon remaining in said extract phase, and distillation to remove the pentane from the aromatic hydrocarbon product.

NORMAN F. LINN.