US2226531A - Production of valuable hydrocarbons - Google Patents

Description

N. K. CHANEY v PRODUCTION OF VALUABLE HYDROCARBONS Filed July 22, 1938 ken 7 Q? W Kl ENTOR.

ATTORNEY.

Patented Dec. 31, 1940 UETED STATES PATENT OFFICE.

CARB

ONS

Newcomb K. Chaney, Rose-Valley, Moylan, Pa.,

assignor to The United vGas Improvement Company, a corporation of Pennsylvania Application July 22, 1938, Serial No. 220,649

8 Claims. (01. 260-671) The present invention relates to the simultaneous production of manufactured gas and valuable hydrocarbons, and relates more particularly to increasing the yield of certain of said 6 hydrocarbons.

In the usual manufacture of oil gas or carburetted water gas, a step in the process comprises cracking of crude petroleum oil or its less costly portions, such as gas oil and residuum oil, under 10 conditions which yield relatively large quantities of fixed or difilcultly condensible gases, such as hydrogen, methane and ethylene together with other gaseous paraflines and olefines, and relatively small quantities of more readily condensible hydrocarbons comprising tar, drip oil and lower temperature condensates. Broadly stated the division between the gaseous and other products depends upon the severity of cracking and the severity of condensation.

It has been proposed to modify the usual conditions of cracking temperatures and time of contact and the temperature of condensation, to produce andrecover smaller proportions of the original oil as gaseous products for distribution as fuel and larger proportions as condensate containing hydrocarbons more valuable for other uses.

Among the hydrocarbons so recoverable are saturated and unsaturated compounds such as benzene, toluene, xylene, naphthalene, anthracene. indene, styrene, methyl styrene, cyclopentadiene, butadiene, isoprene, piperylene, etc.

The usual gas manufacturing condensation down to atmospheric temperature removes from the gas practically all of the xylene, naphthalene, anthracene, indene, styrene, and methyl styrene, a small part of the benzene, and possibly half of the toluene. For the recovery of the remainder of the benzene and toluene and for the recovery of the dienes much lower temperatures of condensation than usually employed in gas manufacture are required.

Among the aromatic hydrocarbons noted above, the alkylated aromatics are in general more vaiuable than the benzene. This is particularly true of the toluene, xylene and styrene.

The principal object of the present invention is to provide a method of increasing the yield of alkylated aromatic hydrocarbons relative to the yield of benzene.

Other features of the invention reside in the steps, combinations of steps .and sequences of steps, all of which together with other features will become more apparent to persons skilled in the art as the specification proceeds and upon reference to the drawing -which shows in elevation and partly in section, a conventional three shell carburetted water gas set chosen for illustration.

Referring more particularly to the drawing, I 5 indicates a generator, 2 a carburetter, 3 a super heater and 4 a wash box.

Generator I is illustrated as having a fuel bed 5, an up run air blast supply 6, and an up run steam supply I. 10

Superheater 3 is shown with a down run steam supply 8.

Generator l is provided at its top with an offtake 9 leading to the top of the carburetter 2, and carburetter 2 is provided at its base with an 15 off-take 10, leading to the base of the superv heater 3.

Superheater 3 is shown with a stack valve II and a gas cit-take I 2, the latter leading to wash box 4 through valve l3. 20

Generator I has a gas off-take I4 at its base provided with valve I5. Gas off-take I4 leads to wash box 4.

Wash box 4 is shown with the conventional gas The apparatus so far particularly described is entirely conventional in character. Any other gas making equipment employing a run with oil might have been substituted for the purposes of describing the invention. 30

The operation of the apparatus will be de-= scribed with a conventional cycle.

The fuel bed 5 is blasted with air supplied at 6. This raises the temperature of the fuel bed and generates producer gas which is burned as 35 it flows through the set by secondary air introduced at I! through pipe l8 controlled by valve I9.

The hot blast gases pass down through the carburetter 2 and up through superheater 3 rais- 40 ing the temperature-of the carburetter and superheater and storing heat therein, and finally escape through stack valve i l.

After the air blasting operation the set is purged of blast gases by steam admitted at I, whereupon 4.5 stack valve II is closed, valve I3 is opened and an up run is made with steam supplied at the same point. The blue water gas thus made passes through carburetter 2, superheater 3, wash box 4, and flows out through ofi-take I6. 50

During this up run with steam petroleum oil is introduced into the set for cracking and fixing in the carburetter and superheater.

Although-the point of introduction of petroleum oil may vary in ditferent gas making equipment,

- mospheric temperature.

a light oil by fractional distillation.

for convenience in description I have illustrated an oil spray 2| at the top of carburetter 2.

Irrespective of the construction of the inside of the carburetter, which may vary widely in different types of apparatus, it is customary to have a. substantial part of this petroleum oil come directly into contact with the heated surfaces,

whether they be of checkerbrick, or of other construction or comprise merely the side walls. However, whether coming into contact with the heated surfaces or not this oil is subjected to the temperatures of the carburetter and superheater as it is carried along by the stream of blue water gas, and is cracked into gas, coke, tar, drip oil and other condensates. The coke is usually deposited in the carburetter and superheater and the condensates. are usually carried out .of the superheater and are condensed at the wash box and cycle might be substituted.

After passing through the ofi-take it the gas usually goes to a relief holder and from thence through water cooled condensers to the purifiers.

for the removal of hydrogen sulfide, and thence to storage holders for release to the distribution system.

The wash box 6 in which the gas comes in contact with water, and the water cooled con' densers cool the gas down to approximately at- The tar and oil condensed out in these vessels comprises a residual tar fraction boiling above 300 C., a dead oil fraction boiling between 200 C. and 300 C., and a light oil fraction boiling up to 200 C. and containing practically all of the styrene, indene, and xylene, possible, half or more of the toluene and some of the benzene and other miscellaneous hydrocarbons or benzol forerunnings. The individual compounds may be recovered from the Usual carburetted water gas practice does not carry the condensation further. However, if after purification the gas is cooled by stages to approximately 65 C., the remainder of the benzene and toluene, as well as the dienes, cyclopentadiene, butadiene, isoprene and piperylene, may be condensed out and recovered separately by fractional distillation.

In the normal production of aromatics from the cracking of petroleum oils, the reaction is supposed to proceed generally as follows:

paraffines olefines and dioleflnes cyclic olefines and naphthenes aromatics Normally, the production of benzene is relatively high compared to the production of toluene and the higher individual aromatic derivatives such as thexylenes, styrene, indene, etc. The production of the alkylated aromatics probably proceeds at least in substantial part, by union of benzene with free alkyl radicals as troleum oil.

benzene+free radicals alkylated aromatics In the normal course of the reactions, through the set or other cracking apparatus, the production of benzene is a delayed reaction occurring in the later stages of the cracking operation. On the other: hand, the production of free radicals occurs largely in the initial stages of the cracking operation.

By increasing the concentration of benzene above that caused by the'concurrent formation of benzene in the petroleum oil cracking operation in its early stages, a greater benzene concentration is provided at the time of maximum free radical formation and the above reaction of benzene with free radicals to form alkylated aromatics is favored.-

Also the presence of an increased benzene concentration above the normal equilibrium concentration in the later stages of the cracking operation tends to oppose the formation of additional benzene by mass action. This tends to suppress the breaking up of alkylated aromatics formed in the earlier stages to form benzene in the later stages of the cracking operation.

Whether the theory above set forth be correct or not, I have found that increasing the benzene concentration above that produced by the normal formation. of benzene from the oil in the early stages of the cracking operation favors an .increase in the yield of alkylated aromatics Thus the increased concentration of benzene may be secured by introducing additional ben-' acne into the cracking chamber during the cracking of the oil.

All or part of the benzene may be separated I such as the carburetter and superheater above.

described, may be widely varied with different cycles and methods of operation, it may not be desirable to introduce the benzene at the point of admission of the petroleum oil, as the zone of maximum free radical production will necessarily vary with the variation in temperature distribution.

The, benzene recycled need not be refined benzene, but may be a crude benzol containing cut from the high or low temperature condensate or a mixture of crude cuts from the condensates. In fact, I have found that a very materially increased yield of styrene, a very valuable alkylatcd aromatic can be secured by recycling light cil containing considerable quantities of toluene, xylene, styrene, indene and residual tar, in addition to benzene. For the purpose of the claims benzol is defined as a mixture of hydrocarbons in which benzene is the principal constituent.

Benzene from any other sourcemay be employed if desirable.

Benzene may'be recycled by separating all or part of the benzene and adding it to the re sidual or stripped gas rich in ethylene and propylene, after condensation of the valuable but thermally unstable dienes, and recycling the mixture of benzene and residual or stripped gas through the cracking apparatus with the pe- III The conventional carburetted water gas apparatus and cycle earlier described were given merely forconvenient illustration of apparatus and process adapted for use with my invention, and are subject to vary wide modifications. It may bepreferable to curtail sharply or to omit the production of blue water gas, employing the fuel bed merely as a means of heating the carburetter and superheater. In such case, in the absence of the blue water gas and excess steam cracking atmosphere, it is desirable to admit steam or other diluent to the carburetter with the petroleum oil to reduce the partial pressures of the vapors and products of cracking. This steam may 'beadmitted through a supply means such as 23. other convenient means of heating'such as an oil, tar, or gas burner inwhich case it is also desirable to admit steam or other diluent with the oil. The above modifications are merely il lustrative. The invention is applicableto any cyclic process in which petroleum oil is thermally cracked under temperature and contact conditions yielding relatively fixed gas and more readily condensible hydrocarbons including benzene and alkylated aromatics.

As an example of increased yields of alkylated aromatic hydrocarbons relative to the yield of benzene in the performance of the invention in apparatus of the character described, the following may be given.

A mixture of Texas Coastal crude oil and refined benzol, in proportions of 2 parts 011 and 1 part benzol by volume, was cracked under the same conditions of temperature and contact as a control employing 100% Texas Coastal crude oil.

In each case steam was admitted with the material cracked, and the set maintained at the average temperature also given below in a table which shows the yields of benzene and alkylatedaromatics.

Tvlvo parts by vo ume eras Coastal crude gg g oil-one part crud: by volume 1 benzol Average temperature .'F. 1484 1490 Styrene .lbs./gal. of oil 0.103 0.073 ..do.... 0177 0.086 ..d0 -0.065 0.518 11 d0 0.397 0.362 Solvent naphtha ..do.. 0. 348 0.235 Residual tar "do" 1. 375 1. 654 Total alkylated aromatics (solvent naphtha calculated as xylene) 1.073 0.823

As above stated, I have further found that the yield of styrene, a very valuable alkylated hydrocarbon, may be very materially increased by recycling light oil separated from the atmospheric temperature condensate from the gas and containing benzene, toluene, a smaller quantity of xylene and still smaller quantities of indene and styrene.

As an example, light oil containing approxi mately 43.1% benzene, 31.5% toluene, 4.6% xylene 1.27% indene, 0.77% styrene and 3.3%

' residual tar was mixed with a Texas Coastal crude oil in proportions of two parts of crude oil to one part light oil by volume.

The mixture was sprayed into the carburetter of a conventional three shell water gas set, at a rate of approximately 3 gallons per minute with steam at the rate of 22.5 pounds per minute.

Temperatures taken at the top and middle of the carburetter and base, middle and top of the su- Also the fuel bed may be replaced by any v quire.

I claim:

1. In a cyclic process for making combustible gas which when practiced in a gas-making set includes in the cycle internally preheating said gas-making set by passage of hot blast gases therethrough and a gas-making run involving the introduction of petroleum oil into said set for vaporization and cracking, the step of increasing the yield of valuable hydrocarbons including alkylated aromatic hydrocarbons which comprises introducing benzene into said gasmaking set during the introduction of said petroleum oil.

2. In a cyclic process for making combustible gas which as practiced in a gas-making set includes in the cycle internally preheating said gas-making set and a gas-making run involving the vapor phase cracking of petroleum oil therein, the step of increasing the yield of valuable 'hydrocarbons including alkylated aromatic hydrocarbons which comprises introducing benzene into said gas-making set in addition to said petroleum oil during said vapor phase cracking of said petroleum oil.

3. In a cyclic process for making combustible gas which as practiced in a gas-making set includes in the cycle internally preheating said gas-making set and a gas-making run involving the vapor phase cracking of petroleum oil therein in the presence of diluent gas, the step of increasing'the yield of valuable hydrocarbons including alkylated aromatic hydrocarbons which comprises introducing benzene into said gasmaking set in addition to said petroleum oil during said vapor phase cracking of said petroleum oil in the presence of said diluent gas.

4. In a cyclic process for making combustible gas which as practiced in a gas-making set includes in the cycle internally preheating said gas-making set and a gas-making run involving the vapor phase cracking of petroleum oil therein in the presence of steam, the step of increasing the yield of valuable hydrocarbons including alkylated aromatic hydrocarbons which comprises introducing benzene into said gas-making set in addition to said petroleum oil during said vapor phase cracking of said petroleum oil in the presence of said steam.

5. In a cyclic process for making combustible gas which as practiced in a gas-making set includes in the cycle internally preheating said gas-making set and a gas-making runinvolving the vapor phasecracking of petroleum oil therein, the step of increasing the yield of valuable hydrocarbons includingalkylated aromatic hydrocarbons which comprises introducing benzol into'saicl gas-making set in addition to said pe-' troleum oil during said vapor phase cracking of said petroleum oil.

6. The process of claim 5 wherein after the process is in operation the benzol introduced into said gas-making set in addition to said petroleum oil isobtained by separation from the products of said vapor phase cracking or said petroleum oil.

7. In a cyclic process for making combustible gas which as practiced in a gas-making set includes in the cycle internally preheating said gas-making set and a gas-making run involving the vapor phase cracking oi petroleum oil therein, the step of increasing the yield of styrene which comprises introducing benzene into said gas-making set in addition to said petroleum oil during said vapor phase cracking of said petroleum oil.

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