US1930216A - Treatment of hydrocarbon oils - Google Patents

Description

Patented Oct. 10, 1933 TREATMENT OF HYDROCARBON OILS I Harold G. Weber, Milton, Mass., assignor to Universal Oil Products Company, Chicago, 111., a," corporation of South Dakota No Drawing. Application December 10, 1931 o Serial No. 580,221

3 Claims. (01. 196-30) This invention relates to the treatment of hydrocarbon oils and refers more particularly to the treatment of the lower boiling motor fuel fractions produced in the'straight run distilla- "5 tion of crude petroleums or from cracking the heavier portions thereof.

More specifically the invention has reference to the method of'treatme'nt of such low boiling motor fuel fractions to'reduoe their total sulphur content, though other beneficial refining effects may be produced at thesame time.

A limit has been placedonthe total sulphur allowable in minor'fuels for automobile engines owing to the tendencyof sulphur compounds of certain types to corrode feed lines, carburetor parts, etc., and the tendency of theseand other compounds to form traces of sulphuric acid when the fuel is burned in the engine, the acid leaking past the'piston rings sufficiently to cause some corrosion 'of the crank case. Since the majority of present day gasoline specifications have set a limit of approximately one-tenth of one percent as the maximum sulphur allowance in motor fuel, and since many straight run gasolines and the majority of cracked gasolines contain sulphur in excess of this amount, it has been necessary to devise treatments to reduce the sulphur content below the allowable limit.

The relative proportions of highly unsaturated or gum-forming compounds and sulphur derivatives' in cracked gasolines or naphthas produced from various charging stocks and under widely varying cracking plant operations makes the treatmentof each individual distillate a special problem.

'In some cases the problem may be primarily i one of sulphur removal and in other cases, such as in the caseof distillates resulting-from the high temperature cracking of low sulphur charging stocks, the problem may be rather the removal of the highly unsaturated olefinic hydrocarbons. v I

It is usual to find in treatments for. desulphurization that the sulphur content may be reduced to a certain point with comparative ease, after which reductions are effected with great difliculty owing to the form or combination of the remaining sulphur, which apparently is contained in heterocycliccompounds, such as thio phene. The present invention is concerned with an eflicient method of reducing the sulphur content of cracked gasolines below the point usually attained by the present commercialtreating processes, though the treatment'may also be effectively applied to the removal of the more easily reactive types of sulphur compounds such as'free hydrogen sulphide, mercaptans, sulphur eth'ers, etc. I 1 In one specific embodiment the invention comprises treatment of hydrocarbon oils in the presence of silver, an electro-positive metal and a solution of salts capable of producing hydroxyl and chloride'ions. v

It will be evident from the foregoing to those versed in the science of electro-chem-istry that under the conditions disclosed the particles-of silver and the electro-positive metals, which are preferably present in a finely divided condition, form an electric couple. The marked afiinity of silver for sulphur results in the rapid 'dissocia- 70. tion of the sulphur compounds with the fixation of sulphur on the surface of the silverr The innumerable small cell units which constantly generate hydrogen ions then act upon-the'superficial layer of sulphide to form gaseous hydrogen sulphide and renew the surface of the silver for further action, so that the process of desulphurlzation may be made substantially continuous under properly regulated conditions; i Of the-electro-positive metals which maybe 30 used to form electric couples with the silver particles it is preferred to use those which are relatively high in the electro-chemical series, and those which are capable of being readilyproduced in a finely divided condition; As metals meeting these requirements maybem ention'ed sodium aluminum, zinc, cadmium,-iron,*etc.

As salts capable of giving hydroxyl ions may be mentioned the ordinary caustic alkalis,'such as caustic soda, caustic potash, and the carbonates and bicarbonates of the alkali metals and ammonia. Chlorides on the same basis may be used to furnish chloride ions,'whose essential function isto prevent the precipitation offhydroxides such as those of aluminum or iron,'which precipitation removes the metal from the sphere of the reaction and eliminates it as one of the members of the electric couple.

The processof the invention may be applied to the desulphurizing of gasolines and to the light hydrocarbon, distillates in a variety of ways. As one mode of operation finely divided silver may be produced on an inert carrier, such as pumice, by the common steps of impregnating-the pumice particles with a solution of the nitrate of the metal, igniting the nitrate at a minimum temperature to produce the oxide, and reducing the oxide (also at a minimum temperature "to preserve the activity of thereduced mctallyand protecting the reduced material from oxidizing influences until it is ready for use.

Similarly the electro-positive metals essential to the process may be separately produced in a finely comminuted state and the silver and electro-positive metals mixed in proper molecular proportions. To the mixture of metals a strong solution of sodium carbonate and sodium chloride may be added to form a slurry or mud and the mass added to a pressure vessel provided with a mechanical stirring device. The oil to be treated is then added to the autoclave and heated to the proper temperature for the desulphurizing reactions with concurrent vigorous agitation.

The hydrogen sulphide produced and other fixed gases may be released intermittently or continuously to keep the pressure within safe limits.'

At the conclusion of the treating period the agitation may be stopped and the contents of the pressure vessel allowed to stratify, whereupon the, upper layer of gasoline or naphtha may be removed and distilled in separate equipment, partly by its contained heat, to produce an endpoint product needing only caustic washing to remove traces of dissolved hydrogen sulphide. I

The treating mass remaining in the pressure vessel may be used without further additions of metals or salts until its efilciency drops below an economical point, whereupon it may be renewed by well known chemical methods, involving water extraction of the mass to remove soluble salts and the further extraction by acids or alkalis of the metallic particles, and a repetition of the stepswhich produce them in the finely'divided condition necessary for their effective electrochemical action.

Another mode of operation which is frequently convenient when dealing with vapors arising from fractionators of crude stills or a cracking plant is to pass the vapors in a continuous stream upwardly through the. silver and electro-positive metals supported on the inert carriers counter flow to the electrolyte salt solutions, concentration of the solutions and the temperature and pressure of operation being so regulated that there is at all times an.aqueous electrolyte in contact with the metallic particles. To provide against the contingency of over-concentration ot the solution with resultant precipitation of P salts possible clogging of the apparatus steam may be introduced into the oil vapors undergoing treatment, the efiect of this addition being to depress vaporization of the solvent.

' Operators skilled in the art of treating hydrocarbons will be able to devise other forms of equipment adaptable for producing the results desired by the use of the process of the invention,

and since the invention is not limited to any form of apparatus in'which it may be conducted it will be unnecessary to suggest further types.

As an example of the results obtainable when employing the process of the invention to treat gasoline vapors from' a cracking plant, a case involving the use of a Mid-Continent gas oil as charging stock to the cracking plant may be cited. The cracking plant may be provided with a fractionator of suflicient capacity to produce vapors of approximate gasoline boiling point range at a pressureof '75 pounds per square inch and a top tower temperature of 400 -F., which temperature corresponds roughly to the end boiling point of the finished gasoline. The gasoline produced without chemical treatmentof the vapors in such a case may have the properties shown in the first column of the appended tabulation, these properties being shown in comparison with those of a gasoline made by interposing the treating step characteristic of the present invention as one stage in the fractionation of the gasoline. The details of the operation may be essentially those already described in connection with vapor phase treatment, the solutions of mixed sodium bicarbonate and chloride being substantially saturated under the conditions of operation and used at the rate of 10 pounds of solution per barrel of condensed gasoline.

Untreated Treated gasoline gasoline Gravity A. P. I 54. 5 54. 8 Endpoint F. 405 406 Color '(Saybolt) 8 +30 Color after 4 hrs. exposure to sunlight 25 Gums by copper dish 350 mgs 35 mgs. Total sulphur O. 3 0. 04

It may be possible to utilize the mixture of silver and aluminum continuously until an amount of gasolineeq'ual to10,000 barrels per tonof metal mixture has passed through the treater before any r'evivification is necessary to maintain the efiiciency of the process.

As another example of results obtainable, a pressure distillate produced by cracking 2. Cali-- fornia. residuum may be treated by the batch method, as described in the specification; By using approximately double the amount of electrolyte (that .is 20 pounds per barrel) that was used in the first example and treating for 15 to 20 minutes at a temperature of 3'OO''F'. and a pressureof 200 pounds per square inch, the pressure distillate maybe redistilled'to produce a finished gasoline needing only a light causticwash to ren der it in a stable andmarketable condition; The tabulation following again shows the relative properties of the gasoline practiced by simple fractionationof the pressure'distilla'te and that produced by. fractionation of the treated distillate: f v

I It will be evident fro'mthe foregoing descrip'-- tion of the invention and the examples of results obtainable by its use that the present invention furnishes an entirely practical and highly efii'cient method for the treatment of cracked distillates; However, since many other examples of operation and results might be given, andsince the process is also well adapted to the treatment or straight run distillates to produce results sub-' stantially equivalentto those given in the examples of use on cracked distillates, it is not intended that the foregoing specification shall act in a limitingsense upon the broad scope of the inven-' tion. r a

I claim as my invention:

- 1. A process for the refining of hydrocarbon distillates to desulphurize the same comprising subjecting the distillates to the simultaneous ac- 3. A process for the refining of hydrocarbon distillates to desulphurize the same comprising subjecting the distillates to the simultaneous action of aqueous solutions of sodium bicarbonate and sodium chloride while in the presence of metallic silver, and aluminum.

HAROLD C. WEBER.