US2087660A - Processes of making organic lead compounds and hydrocarbon liquids containing same - Google Patents

Description

y 1937 F. w. SULLIVAN, JR 2,087,660 I PROCESS OF MAKING ORGANIC LEAD COMPOUNDS AND HYDROCARBON LIQUIDS CONTAINING SAME Filed Jan. 15, 1932 Jazubbez Becea'vez/ N Becenreo 2 INVENTOR v ATTORNEY Patented July 20, 1.937

UNITED STATES PATENT OFFICE PROCESSES OF MAKING ORGANIC LEAD COMPOUNDS AND HYDROCARBON LIQ- UIDS CONTAINING SAltIE Frederick W. Sullivan, Jr., Hammond, Ind., as-

signor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application January 15, 1932, Serial No. 586,754

18 Claims.

Hydrocarbon compounds of lead, such as tetraethyl lead, have been known for a number of years and are used at the present time in great quantities as knock suppressors in motor fuels. 15 In general, these lead alkyl compounds are prepared by reacting an alkyl chloride or bromide with a lead alloy 'such as an alloy of sodium and lead. There are a number of other ways of makmg leadalkyl compounds all of which in general 30 require the use of an alkyl halide.

The various chemical methods now in use for' making lead alkyl knock suppressors are relatively expensive and it is highly desirable to have a cheaper method for this preparation. While tetra-ethyl lead is by far the most important of the alkyl lead derivatives used as anti-knock substances, other lead-alkyl compounds are eilective to a greater or lesser degree. It is not essential that an alkyl-lead compound be pure, but it must go be volatile and soluble in gasoline.

I have now found that hydrocarbon compounds of lead can be directly preparedunder certain conditions from metallic lead and the thermal decomposition products of hyrocarbons. I find 35 that it is possible to react free alkyl radicals such as ethyl radicals with-lead provided certain precautions are observed. I have also found that hydrocarbons can be dissociated by the application of heat to yield such free radicals and that 40 if the dissociation products are brought into immediate contact with metallic lead, the lead will unite with the free radicals in the reaction products to form hydrocarbon compounds of lead.

Generally speaking, in my process, I heat a 45 hydrocarbon for example, propane, butane, or

hexane to a cracking temperature and then, before the free radicals thus formed as reaction products of the heating have an opportunity to recombine, I bring the reaction products into 50 contact with metallic lead.

Advantageously, I cool the reaction products before contacting them with the lead. This is to prevent the decomposition of the lead-hydrocarbon compounds since these substances would 55 otherwise decompose if the temperature were appreciably above 150 0., the decomposition temperature of the compounds.

In my process I also, make use of a relatively high gas velocity, which is to say, I bring the gaseous hydrocarbon products resulting from the 5 thermal dissociation rapidly into, contact with the metallic lead by imparting a high velocity to the hydrocarbon reaction products. Alter- ,natively I may disperse metallic lead in the hydrocarbon vapors before or after undergoing thermal dissociation, whereupon the desired products are formed immediately the temperature is reduced to approximately 150 C.

In the appended single sheet of drawings, I.

have illustrated an advantageous form of apparatus for carrying out my invention.

In the drawing, the numeral] indicates a storage tank for hydrocarbon material. Vapors withdrawn from tank I pass by way of valved conduit 2, having valve 3, to a reactor 4. Reactor 4 is provided with electric heating coils 5 to heat the hydrocarbon vapors rapidly to such a temperature that they'are caused to dissociate into ,free alkyl radicals. Instead of electrical heating coils, I may use ordinary tubular heating elements supplied with hot heating fluid. Disposed within the reactor 4, and beyond the he ting coils 5, I provide a cooling coil 6 to rapi y cool down the dissociated hydrocarbon vapors. Cooling coils 6 contain a cooling fluid, for example liquid carbon dioxide, sulphur dioxide, propane, o'r brine, entering through pipe I 'and discharging through pipe 8. This coil may be constructed of any suitable material such as copper.

A plurality of lead baiiles, such as lead screens 9, disposed in the region of the cooling zone, are for the purpose of providing a source of metallic lead. This is one advantageous way of maintaining a body of metallic lead in the reactor so that free alkyl radicals formed as thermal dissociation 40 products of the hydrocarbons may unite there-- with. 1

Alternatively, adispersion of "metallic lead in an inert gaseous medium, for example hydrogen, can be supplied to the reactor. iently done by providing an electric arc chamber In wherein an electric arc is maintained between lead electrodes ll An inert gas is supplied to the chamber through pipe l2 and withdrawn through This is conventhe hot hydrocarbon vapors after they have passed over heating coil 5.

In that portion of the reactor generally indicated by the baiiles 9, free alkyl radicals, resulting from the thermal dissociation of the hydrocarbon material, unite with the metallic lead of the baiiies or with the lead fog or mist produced in chamber Ill and fed to the reactor through pipe. [3, forming lead alkyl compounds. These reaction products, together with any undecomposed hydrocarbon material, free hydrogen (one of the dissociation products) and any other reaction products pass out of the reactor through valved pipe l9 into scrubber 20. Scrubber 20 can take the form of any suitable gas scrubbing device and in the conventional showing on the drawing, the scrubber is provided with baflles or bubble trays and an inlet for scrubbing liquid 2|. The scrubbing liquid used is advantageously a petroleum oil fraction preferably of the intermediate viscosity range, for example, gas oil. During the counter-current flow of reaction products and scrubbing liquid, lead alkyl compounds are extracted from the reaction products and are absorbed in the scrubbing liquid.

Scrubbing liquid containing dissolved lead alkyl compounds flows from the scrubber by pipe 22 to a distilling apparatus 23 in the lower end of which a heating coil 24 is provided. In the distilling apparatus, the lead alkyl compounds are volatilized from the scrubbing liquid. The volatile products passby way of pipe 25 to cooling coil 26, wherein they are condensed, and thence flow to receiver 21 provided with valve outlet 30. Any uncondensed vaporized portions flowing through pipe 25 may be fed back to the inlet of the reactor through pipe 28 and pump 40. A valved vent 29 may be provided to periodically relieve the system of any accumulation of inert gases distilled out of the scrubbing liquid.

The scrubbing liquid is recycled back to the scrubbing column 20 by means of 'outlet pipe 31, pump 38, cooling coil 39 and distributor pipe 2|. There is thus provided a continuous cycle of scrubbing liquid so that losses thereof are minimized.

Any reaction products not absorbed in scrubber 20 are withdrawn from the top thereof through outlet 3|, vacuum pump 32 and returned to the reactor inlet through pipes 34 and 35.

Since one of the dissociation products flowing from the reactor is hydrogen, the unabsorbed gases are periodically vented through valve vent 33 to prevent an accumulation of hydrogen gas in the system. However, a certain amount of this hydrogen or other dissociation products which have neither reacted with the lead nor retained in the scrubbing liquid, is advantageously fed into arcing chamber l0 and is used as a dispersion medium for the lead fogformed in the chamber. Further portions of unabsorbed reaction products which have been cooled in scrubber 20, may also be returned to the reactor through valved pipe plicable to the treatment of low boiling hydrocarbons such as methane, ethane, propane,'or

butane. My process also ofiers a convenient way of directly introducing knock-suppressing agents into liquid hydrocarbons of the gasoline type such as hexane, pentane and commercial gasoline. In

this case the apparatus is somewhat simplified and I withdraw reaction products from the reactor through valved pipe 4la to cooling coil 4| and thence to receiver 42 having valved outlet 42a. Any uncondensed gases which collect in receiver 42 can be recycled to the inlet of the reactor through pipes 43 and 4311. or can be pumped back to the reactor inlet through valved pipe 44, pipe 28 and pump 40.

The reaction product collected in chamber 42 in this modification of my invention, comprises a motor fuel stock containing lead alkyl compounds in solution.

Product obtained from receiver 21 through outlet 30 consists mainly of lead alkyl compounds together with small quantities of condensed hydrocarbon material and the yield of lead compounds is almost theoretically based on the quantity of lead consumed.

The operation of theforegoing apparatus will be clear from the above description. Quantitative operating data are, of course, largely dependent upon the capacity of the apparatus. In general, the hydrocarbon vapors are heated by coils 5 to a temperature of 400 to 900 centigrade depending on the nature of the hydrocarbon.

- The temperature to which the hydrocarbon is heated must be such that thermal dissociation thereof to form free alkyl, radicals will occur. With normal hexane, this temperature is about 600 centigrade and hexane vapors can be formed, outside of the reactor by any suitable boiling apparatus. The storage tank I, for example, can be provided with a heating coil to vaporize the hexane. A temperature 01' 600 centigrade in the heating coils 5 will insure an appreciable yield of dissociation products containing free alkyl radicals. Cooling coils 6 must be operated at a temperature below that at which lead alkyl compounds decompose. This is about centigrade for tetra ethyl lead.

If methane is used as a source of hydrocarbon material the thermal dissociation temperature may be about 900 centigrade. With ethane, propane, butane, pentane, and unsaturated hydrocarbons such as propylene and butylene, the temperature in heating coils 5 should be somewhat above 500" centigrade. 500 to 700 centigrade is a suitable temperature.

Advantageously the whole system is maintained under a reduced pressure so that the gas velocity within'the reactor is rapid. Since the life of the free alkyl radicals is very brief, not'longer than one second, it is essential that the dissociation products be cooled and brought into contact with metallic lead within this brief interval. The

pumps 32 and 40 are therefore operated in such a manner as to create high velocity through the reactor and such a velocity is of the order of 10 to 20 metersper second. Best results are obtained when the gas velocity is such that the dissociation products are cooled and brought into contact with metallic lead within of one second after their formation. As' stated the effective life of the freealkyl radicals is so brief that they recombine with each other within a second after their production.

Any hydrocarbon liquidor gas which will yield free alkyl radicals on thermal dissociation is useml in my process so long as .care is taken to quickly cool the products of thermal dissociation before the-free alkyl radicals recombine. All of the aliphatic hydrocarbons both saturated and unsaturated, which are normally liquids or gases, can be used in my process.

The normally gaseous or highly volatile hydrocarbons are advantageously used when it is desired to prepare a condensed reaction product consisting almost entirely of lead alkyl compounds. Gasoline motor fuels can then be mixed with small quantities of the product .to impart anti-knock properties to the fuel.

In one characteristic operative example of my process wherein lead compounds were formed directly in a gasoline, I employed a gasoline with an octane number of less than 55 and, after vaporizing the gasoline and passing it into the re- 5 actor, and cooling and condensing the resulting product,\ I obtained in receiver 42 a product consisting of undecomposed gasoline containing lead alkyl compoundsand this product had an octane number above 65. This indicates that appreciable quantities of lead alkyl compounds were formed in the gasoline and the product was suitable as a fuel. When working with ordinary commercial gasoline having'an end point of 400 F. I advantageously heat the gasoline vapors to a temperature of about 500 centigrade in the reactor, cool them to a temperature of approximately 150 centigrade as rapidly as possible and simultaneously allow them to react with metallic lead asI have described. Having thus described my invention what I claim is: i

r 1. The .method of preparing a hydrocarbon liquid containing dissolved organic lead compounds which comprises subj ecting the hydrocarbon to thermaldissociation to form a gaseous reaction mixture containing free alkyl radicals, the hydrocarbon being one which yields such free alkyl radicals on such thermal dissociation, immediately bringing the hydrocarbon reaction mixture into contact with solid, metallic lead whereby organic lead compounds are formed, and then condensing the reaction products. 2. The method of preparing gasoline containing dissolved organic lead compounds which comprises thermally dissociating vapors of gasoline to form gaseous hydrocarbon reaction products containing free alkyl radicals, immediately reacting the gaseous hydrocarbon reaction products with solid, metallic lead whereby organic compounds of lead are formed, and then condensing the reaction products.

3. The method of preparing a hydrocarbon liquid containing dissolved organic lead compounds which comprises heatingvapors of a hydrocarbon liquid, of the type lfloerating free alkyl radicals on decompositiornto thermally dissociate the hydrocarbon and form free alkyl radicals, bringing the gaseous hydrocarbon reaction products into immediate contact with solid, me-

tallic lead whereby organic lead compounds are formed, and then condensing the reaction products.

4. The method of preparing a hydrocarbon liquid containing dissolved organic lead compounds which comprises heating vapors of a hydrocarbon liquid, of the type liberating free alkyl radicals on decomposition, to thermally dissociate the hydrocarbon and form free alkyl radicals, cooling the gaseous hydrocarbon reaction '70 products to a temperature below the decomposi- I 5. The method of preparing gasoline containing dissolved organic lead compounds which comprises heating gasoline vapors to thermally dissociate the vapors and form a gaseous hydrocarbon mixture containing free alkyl radicals, bringing the gaseous hydrocarbon mixture into immediate contact with solid, metallic lead, and condensing the reaction products.

6. The method of preparinggasoline containing dissolved organic lead compounds which 10 comprises heating gasoline vapors to thermally dissociate the vapors and form a gaseous hydrocarbon mixture containing free alkyl radicals, cooling the gaseous hydrocarbon reaction products to a temperature below the decomposition l5 temperature of lead-alkyl compounds, bringing the gaseous hydrocarbon mixture into immediate contact with solid, metallic leadfand condensing the reaction products. j

7. The method as in claim 3 wherein the gase- 20 ous hydrocarbon reaction products are brought into contact with solid, metallic lead dispersed in an inert gas.

8. The method as in claim 5 wherein the gaseous hydrocarbon mixture is brought into contact 25 with solid, metallic lead dispersed in an inert gas.

9. In a process of preparing lead alkyl compounds the steps which comprise thermally dissociating an aliphatic hydrocarbon to yield gaseous dissociation products containing free alkyl 30 radicals, cooling the reaction products to a temperature at which lead alkyl compounds are stable, and contacting the cooled, gaseous reaction products with solid, metallic lead at least within one second after their formation. 35, 10. In a'process of preparing lead-alkyl compounds the steps which comprisethermally dissociating a normally gaseous aliphatic hydrocar-. bon to yield dissociation products containing free alkyl radicals, cooling the reaction products 40 to about C. or below, and contacting the cooled reaction products with solid, metallic lead within at least one second after theirformation.

11. The process of making lead alkyls which comprises subjecting an organic compound 'ca- 45 pable of yielding upon decomposition an .alkyl radical to a. temperature sufiicient to decompose said'compound and liberate free alkyl radicals, and contacting the decomposition products con taining free alkyl radicals with lead in a highly 50 dispersed state to form lead alkyls, the reaction being effected at a temperature above normal but below the decomposition point of the lead alkyls.

12. The process of making lead alkyls which- 55 comprises subjecting an organic compound capable of yielding upon decomposition an alkyl radical in the substantial absence of air to a temperature sufilcient to decompose said comto be formed with lead in a highly dispersed 65 state to thereby obtain lead alkyls.

13. The process of making lead alkyls which comprises subjecting a hydrocarbon of the paraflin series in the substantial absence of air to a temperature sufficient to decompose it and liberate free alkyl radicals, and contacting the decomposition products containing free alkyl radicals in the substantial absence of air and at a. temperature abovenormal but below the decomposition point of the lead alkyls to be formed Z5 temperature above normal but below the decomposition point of the leadhydrocarbons to be formed.

" 15. The process of making lead hydrocarbon compounds which comprises subjecting an allphatic hydrocarbon capable of yielding upon decomposition free alkyl radicals to a temperature suflicient to decompose said hydrocarbon and liberate free alkyl radicals, and contacting the decomposition products containing free alkyl radicals with a solid lead in the substantial absence of air to form lead hydrocarbon compounds, the reaction be'ing efiected at a temperature above normal but below the decomposition point of the lead hydrocarbons to be formed.

16. In the process of preparing hydrocarbon compounds of lead the step which comprises reacting metallic lead with free alkyl radicals derived from the dissociation of a hydrocarbon capable of yielding free alkyl radicals on dissociation.

' 1'7. The process of preparing lead alkyls which comprises dissociating a hydrocarbon yielding free alkyl radicals on dissociation'and contacting said free alkyl radicals with metallic lead at a temperature below the decomposition temperature of the lead alkyls.

18. The process as in claim 17 wherein the hydrocarbon is gasoline.

FREDERICK W. SULLIVAN, JR.

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