US2216470A - Catalytic conversion of hydrocarbons - Google Patents

Description

Patented Oct. l, 1940 y UNITED CATALYTIC CONVERSION oF HYDRO- f cARBoNs corporation of Maine Application July 9, 1936,` Serial No. 89,713

5 Claims.

This invention relates to a process for catalytically converting hydrocarbons of relatively low boiling point and relatively poor antiknock properties into hydrocarbons having high antiknock ratings and suitable for use as motor fuel in high compression engines. `More particularly the process of the present invention relates to the catalytic conversion of saturated hydrocarbons such as natural gas gasoline, straight run gasoline, propane, butane and similar hydrocarbons contained in natural gas into motor fuel gasoline of higher octane number than the original stock.

Many processes have been devised for the reforming of straight run gasolines', naphthas and similar hydrocarbon mixtures in order to produce gasolines of higher octane value. However, most of the processes employed in such operations involve the use of extremely high temperatures upwards of 1100 F. as well as high pressures. Some processes operate at slightly lower temperatures but excessively high pressures are vernployed. Temperatures of the order of 1300o F. and higher are used for the conversion of hydrocarbons of the type of butane and propane into constituents suitable as a gasoline motor fuel. Such processes require expensive vand elaborate equipment and are in many cases economically impracticable because of the loss occasioned from the conversion of the hydrocarbons-into substany tially fixed gases such as hydrogen and methane. In the conversion of straight run gasoline and natural gasoline to productsI of higher octane value, losses of this character make the resulting products tooexpensive to warrant production except for special purposes.

vThe `primary object of the present invention` therefore is to provide a catalytic process for converting hydrocarbons ofthe type referred to into high octane products in a relatively simple and inexpensive manner.

A further object of'` the present invention is to provide a process for catalytically converting relatively low boiling hydrocarbons into high octane motor fuel products by the use of relatively low conversion temperatures and moderate pressures.

Accordingly, the improved process of the present invention comprises the steps of heating the hydrocarbon to be converted to a moderate tem# perature of from 750 to 850 F. and intimately contacting the heated material with a catalytic metallic salt comprising the iron, aluminum, copper, zinc, molybdenum, chromium, manganese or, nickel salts of phosphoric acid, sulfuric acid,

hydrochloric acid, silicio acid or boric acid.

These catalytic materials may be for convenience deposited on inert carriers such as fullers earth, coke particles, or other similar material, or they may be used by themselves.

Other features and advantages of the process of the present invention will be apparent to those skilled in the art from'the following detailed description taken in connection with the accompanying drawing in which:

The single gure is a' diagrammatic ow sheet E@ illustrating an apparatusV particularly adapted for carrying out the improved process. f

Referring to the drawing the hydrocarbon to be converted which for vpurposes of illustration is natural gasoline, is introduced into the system B5 of the apparatus through a feed line 2 and forced by means of a pump 4 and a line 6 through a' high pressure heat exchanger 8 in which the charging stock is passed in heat exchange with a portion of the product produced in the cong@ version operation. The material discharged from the pump' should be at a pressure of from 550 toi800 pounds per square inch. The preheated charging stock isy conducted from-the heat exchanger at a temperature of labout 400 F'.y and passed by means ofl a line I0 through a second l"heat exchanger I2vin Whichfthe charging stock is heated to a higher temperature by heat exchange with high temperature vapors in the conversion process. lThe preheated voil leaves the g@ heat exchanger I2 at a temperature of labout 550 F. and is conducted through a line I 13 into and throughy a pipe coil heater mounted in a pipe still furnace I6. In passing throughthe pipe still furnace the natural gasoline charging stock is g5 raised to a temperature of from 750"to 850 F., and maintained at this temperatureflna portion of the coil' for a substantial period ,of time and then discharged through a transfer line I8'. At the temperatures and pressures given above the period of time referred'to is preferably from 8 to 14 yminutes. l

The pipe still heaterII may be of conventionally known Aconstruction in which tubes of Athree or four inch internal diameter are employed, and 5 in which the pressure drop" may be from 200 to 300 pounds per square inch, lso that the pressure in the transfer line I8 will be from 250 to 600 lbs. per square inch.'

The highly heated products discharged through 50. the transfer line I 8 areconducted into an ejector mixing nozzle 20 mounted at the bottom of an enlarged reaction chamber22. The products are then conducted from theejector 2|] through a line 24 and discharged tangentially into the up- 55 per part of the reaction chamber 22 through one or more vertically spaced lines 26.

The catalytic agent employed in the conversion operation which may, for example be anhydrous iron phosphate or anhydrous aluminum phosphate, is introduced into a catalyst mixing chamber 28 through a valved feet chute 30, and therein intimately mixed with natural gasoline introduced through a valved line 32. The mixture of oil and catalytic material in the chamber 28 may be made up continuously or in batch for use in the conversion operation,fand itmay be introduced into the conversion process by taking a part of the charging stock discharged from. the heat exchanger I2 through the line I 4 and passing it through a valved line 34 into an ejector'nozzle 36 at the bottom of the mixing chamber 28. 'I'he oil is passed at a high velocity from the line 34 and picks up the catalytic mixture in nozzle 36.`

The oil mixture may be introduced directly into the line 24 through a valved line 38 or passed through a valved line 40 to the inlet of the pipe still heater I6 with the preheating charging stock in line I4. In accomplishing the latter operation the ow of oil through the lines 34, 38 and 40 (including the bypass) may be controlled bythe valves in lines 34 and I4, or a pump 42 mounted in line 40 may be used to force the oil-catalyst mixture from the mixing nozzle 36 into the line I4, regardless of a lower pressure in line 38.I

In carrying out the process, it is not necessary to continuously introduce the catalyticmaterial into the reaction chamber 22 or into the pipe still heater, but a continuous operation may be effected by mixing a relatively small proportion of catalyst with the oil in the line I4 passing to the heater I6. The prpportion of catalyst may be adjusted by controlling the valve in line 34.

'I'he mixture of high temperaturel products and catalyst discharged through the line 26 into the upper part of the reaction chamber 22 tend to spiral'around the inside of this chamber sothat the catalyst together with any small amount of liquid which may be present flows down the walls of the chamber and collects in the conicalbottom from which the catalyst and anyv liquid passes immediately into the nozzle 2li.A The high velocity in the nozzle 20 remixes the catalytic material withthe products discharged from the transfer line and they are again passed into thev upper part of the reaction chamber.

At the temperatures employed, that is preferably 800" to 850 F. maintained in the reactiony chamber22, there will be substantially no yliquid .in this chamber so that the lcatalyst will fall to the bottom of the chamber or be suspended inthe vapors in the chamber. The vapor products are discharged from the reaction chamber 22 through a vapor transfer line 44`andintroduced tangentially into the Aupperpart of a cyclone type separator 46 in which the spent or partially spent catalytic material is separated from the converted hydrocarbon vapor mixture. The catalytic material is collected in the conical base of this separator anddischarged through a valved line 48, while the separated vapors pass downwardly through the separator 46 and out through a central enlarged conduit 50. These vapors are conducted on through a line 52y into the heat exchanger- I2 where they are substantially reduced in temperature to about 575 F., and then conducted through a line 54 into the base of a fractionating tower 56. i

In the tower 56 the vapors are rectified under a substantially high pressure to separate a light and gas separator 64. The separator 84 is main-r tained under a relatively high pressure so that substantially only the xed gases such as hydrogen, methane, ethane and ethylene are discharged through a valved gas line 68. The

y condensed product passes from the receiver through a valved line 68 and any portion of this product may be returned ,to the top of the tower '56 through a valved line 'I0 in which is mounted a pump 12 for controlling the cut temperature on the tower. l,The product discharged through the'line 68 will be a relatively light gasoline having an end point of about 325 F. and this product is preferably blended with heavier stock and stabilized to remove any excessive quantities of lighter materials such as a portion of its propane and butane content.

The heavier condensate which refluxes downwardly through the tower 56 andcollects in the bottom of the tower, is removed through a line `I4, passed through the high pressure heat exchanger 8 and finally discharged in a cooled condition through a valved line 16. This product contains some constituents which are heavier than thosedesired in the usual gasolines. They may be eliminated by a suitable distillation, the overhead products being available for blending with relatively-light gasolines such as the gasoline removed through the line 68. -The products removed through the-lines 68 and I6 however have octane ratings of from 76 tov 85, increased lead susceptibility and oxygen bomb stability, and therefore are particularly suitable for blending with lower octane numbered gasolines. The products are the result of molecular rearrangements and additions and not of decomposition. Therefore there is practically no tarry fraction formed.

'I'he pressures maintained in the receiver 64 and tower 56 will be substantially equalto that maintained in the reaction chamber 22 except for the usual pressure drop through the various intervening elements of the apparatus. vIt will also be apparent that the temperature and pressure in the separator 46will not be substantially different from that in the reaction chamberl 22 and ytherefore the conversion reaction in contact with the catalytic material will still proceed in theseparator 46. 'I'he tower 56 and the separator 46 may however be operated at lower'pressures if desired. All of the apparatus is heavily insulated.

yThe theory of the action of the catalytic material .on the conversion of the parailln hydrocarbons into constituents oi.' higher octane value is not definitely understood bu.: it may beexplained by the iniluence of the catalytic substances on the fected including the alkylation of straight chainV hydrocarbons forming branched chain as well as cyclic hydrocarbons.

The spent catalyst may be revivified by Wellknown methods, such as the heating of itin a stream of air or oxygen containing gas.

From the foregoing description of the process of the present invention, it will be apparent that certain modifications of the process may be made and that it may be carried out in apparatus substantially different from that described. Low boiling oleiin hydrocarbons may be converted to motor fuel either alone or when mixed with paraflins. Such features arev contemplated within the spirit andsscope of. the present invention.

Having thus described the invention in its preferred form, what is claimed as new is:

1. The process of catalytically converting a paramnic hydrocarbon containing from three to four carbon atomsrto the molecule into a mixture of hydrocarbons having a substantially` higher molecular Weight, which comprises carrying out the process in the absence of added hydrocarbons of other type and hydrogen at a superatmospheric pressure of from 400 to 600 pounds per square inch, preheating the aliphatic hydrocarbon to be converted and lmixing it with a relatively small proportion of a solid catalytic metallic salt which is adapted to catalyze isomerization and alkylation reactions, passing the resulting mixture in a stream of restricted cross-section through a long heating zone in the rst part of which the mixture is heated to a temperature of at least 750 F. and in the latter part of which the temperature is substantially maintained and raised to a point of approximately 850 F., discharging the resulting heated mixture into an enlarged reaction zone in which intimate contact is maintained between the hydrocarbons and the catalytic material, passing the mixtureinto a separator in which the catalytic material is separated from the resulting converted hydrocarbon, and recovering the condensable products resulting from the conversion reactions.

2. The process defined by claim 1 in which the preheated mixture is passed in a stream to a heating zone and in which said stream is divided and one portion thereof mixed with said catalytic material and againlunited with the other portion prior to its introduction into said heating zone.

3. The process defined by claim 1, in which catalytic material is withdrawn from one end of said enlarged reaction chamber and mixed with a stream of oil from the heating zone and reintroduced into the opposite end of said reaction chamber.

4. The process dened by claim 1 in which the catalyst salt is anhydrous iron phosphate.

5. In the process of catalytically converting paraflinic hydrocarbons containing from three to four carbon atoms to the molecule into a mixture of hydrocarbons having a substantially higher molecular weight, the improvement which comprises eectingsaid conversion at a temperature of 750 to 850 F. and at approximately a pressure of from 250 to 600 lbs. per square inch While intimately contacting the hydrocarbons to be converted with a catalyst adapted to catalyze isomerizatlon and alkylation reactions comprising anhydrous iron phosphate, 'and separating the desired liquid conversion products 'from the hot products resulting from the reaction by'cooling and condensation.

WILLIAM E. FORNEY.

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