US2393288A - Process for the catalytic reforming of hydrocarbon mixtures - Google Patents

Description

Patented Jan. 22, 1946 PROCESS FOR THE CATALYTIC REFORMIN G F HYDROCARBON MIXTURES No Drawing. Application .nuys, 194s,

. Serial No. 493,631

12 Claims. (Cl. 196-24) UNITED STATES PAT-TENT OFFICE This is a continuation-in-part of Serial Nos. 252,594; 302,018; and 353,378, which have issued as U. S. Patents No. 2,369,432; 2,325,033 and 2,325,034 respectively. I

This invention relates to the treatment of impure hydrocarbon fractions, and especially to the conversion thereof and removal of impurities such as sulfur compounds therefrom, and also to catalysts for such processes.

Most petroleum fractions contain more or less sulfur which ordinarily is present principally in the form of organic sulfur compounds. In many instances the sulfur content in gases is so high as to render them objectionable for sale for fuel gas. In other instances crude oils and their ent. Furthermore, the phenols may be converted various residua and distillates are so high in sulfur as to render them objectionable for uses to which they are adapted, for example as cracking stocks, fuel oils, lubricating oils, aromatic solvents, motor fuels, or the like. Some such and similar materials including shale oil and coal tar fractions also contain oxygen and nitrogen in the form of phenols, nitrogen bases and p other compounds which are objectionable.

The principal object of the present invention is to provide a'process whereby impure hydrocarbon fractions, especially those boiling above the gasoline range, may be treated. and a very high degreeof conversion of the hydrocarbons to more desirable forms, and conversion of the non-hydrocarbons such as the organic sulfur compounds, phenols and high-boiling nitrogen bases, into readily removable forms such as hydrogen sulfide. water and lower boiling nitrogen bases, may be effected. A further object is to provide suitable catalysts for this process. as well as suitable processes for manufacture of such catalysts. A catalyst which will effect a high rate of sulfur conversion is of special value because of the fact. that some fractions, such as petroleum fractions, will contain as much as about 20% of organic sulfur compounds althoughthe actual sulfur content may be only about 3%, for example. 'Where sulfur conversion to hydrogen sulfide is effected. the organic compounds freed from the sulfur may be left in the fraction, these compounds frequently being especially valuable constituents of motor fuel, lubricating oil, etc. Therefore, sulfur conversion as distinguished from complete removal of the sulfur-bearing compounds is of great importance. Likewise, complete removal or conversion of phenols from aromatic fractions renders them more suitable as solvents, and'rthe removal of nitrogen compounds improves various hydrocarbon mixtures in which they may be presing hydrocarbon fractions in the liquid or vapor phase over or through a catalyst comprising cobalt molybdate. When the fraction is a gasoline or gas oil, it'is usually preferable to treat it in the vapor phase, heavier fractions generally being treated in the liquid phase. The operation is preferably conducted under pressure and in the presence of hydrogen;

' The catalysts for the above process may be cobalt molybdate either as such or on a canier. Where precipitated cobalt molybdate as such frequently effects a considerable degree of treatment and conversion, it is highly preferable to precipitate the cobalt molybdate in the presence of a hydrous gel, particularly an alumina gel which is a porous gel producible as herein described,

and it appears to be preferable that the catalyst consisting of hydrous alumina gel and cobalt molybdate contain only about weight of cobalt molybdate. A given weight of cobalt molybdate included in such proportions in such a catalyst is much more effective than an equal weight of the cobalt molybdate employed by itself. I have further discovered that the catalyst is, of outstanding value when the cobalt molybdate is preciptated in the presence of a washed wet aluminum hydroxide gelfolowing its precipitation but before the hydrous alumina.- gel has been allowed to dry. Under these conditions the molybdate is distributed through the gel and may even react chemically with the gel. The dried :catalyst is of such form that it is highly porous, active, and stable at high temperatures, and exhibits another characteristic distinct from the usual supported molybdate catalyst prepared by participating cobalt molybdate onto a'dried support, in that when first introduced into use,

. its activity builds up gradually and continuously as distinguished from the other catalysts whose activity builds up very rapidly to a maximum and then drops back in the early life of the cata- 10% to 30% by lyst to an effloiency value as measured by conratio of 1 moi meniach less than the maximum version rate of very mu sustained conversion ra prepared by precip initially formed we te of the preferred catalyst on in the presence of the t hydrous gel.

ay, therefore, treatment of impure pecially those heavier molybdate catar aspect of the lnv cobalt molybdate' ca port preferably conia, titania, thoria, are also very effective, cipitated in the p drous alumina or vention extends treatment above methods of trea The present invention in to be based broadly upon hydrocarbon frac than gasoline,,emp

In a narrowe ioying cobalt talyst is carried upon a supgel, although zirchromia and magnes and preferably is pree of the original wet hyzirconia or other gel. Theinonly to the-broad catalytic indicated, but also to specific ting specific stocks, such as liquid phase methods, for rean alumina methods, especially moving non-hydroca gen, and nitrog fractions such gas oils, and to concurre bons in such fractions by duction in mole polymerization an including hydroforming, arom erization in this cate tends to similar proce hydrocarbons, as well as and to the methods of pr bait molybdate cata processes of this inven ch involve pre a water solution of the nitrate or sulfate, by th ous solution of preferably conta a mixture of cob ferably dilute of paramolybdate to a mole of am- A cobal't molybdate cata'lyst was prepared as Cobalt nitrate Ammonium moly 1.1-mols=1365 Bra-ms Ammonium hydroxide w 12 mols=800 ml.

. The'cobalt nitrate was dissoived in liters of 10 water.

bdate and am-' of cold water. to'the cobalt The ammonium moly 'monia were dissolved in. 6 liters The moiybdate-solution' was added solution with s g and the grey pink precipiormed wasfiltered off. te was washed n tate which was i The precipita usinga total of 6 liters of cold resuspended-in tered. It was hours at 220' 6 liters of cold water and refildried in the oven for forty-eight I". The dried cake w It. was ground as light purple and pelleted in onefourth inch pellets. ent bulk density of a The product had an apparbout 138 grams per 100 ml. A cobalt molybdate on alumina catalyst was prepared as follows:

H2O (molecular.

Aluminum nitrate. alghoms dehydrogenation.

weight 3'75) Ammonium hydroxide The aluminum nitrate w 6 mols=2250 grams 18 mols=1200 ml.

as dissolved in 10 liters of hot water. The ammonium hydroxide was di- 0 luted to 4 liters withcold wa with stirring to The resultant precipita cessive suspension water. The filter was suspended in with the following:

Cobalt nitrates Ammonium molybdater" ter and added slowly nitrate solution. te was washed by two suc- 0 liter portions of hot cake, without further drying, l0 lltersof cold water and used the aluminum 0.! mols=200 grams 1 0.1 mols=i20 grams (0 Ammonium hydroxide 0.8 mols= ml.

The cobalt nitrate was dissolved in the above alumina suspension.

washing of soluble salts y such as ammonium n The ratio of cobalt to m equimolar, althou also be employed Catalysts of unusual v cipitating the cobalt m especially when the carrier i a m such as hydroxide of alu conium, thorium, um. It is preferred in the metal hydroxide be no precipitation of the co Under these circumstanc appears to be unusually a enter into some chemic carrier.v The catalyst nee free metal before use.

As specific examples of prefer preparation of two cataly following paragraphs. water refers to distilled water; refers to CO(NO3) 2.611

from the precipitate. olybdenum is preferably ght excess of cobalt may to advantage in some instances.

alue are obtained by preolybdate on a carrier, etal hydroxide titanium, zirium', or even chromithese preparations that t dried prior to the. alt molybdate thereon. es the cobalt molybdate ctive, and may actually combination with the d not be reduced to the red catalysts, the described inthe In the descriptions cobalt nitrate" :0 (molecular weight 291') ammonium molybdate refers to paramolybdate weight 1236); and to concentrated ammon approximately 15 norm tion of "normal ammon to above is prepared by dissolving the ammonium paramolybdate and ammonia in water, in the ammonium (NHO eMmOaAHzO I (molecular ammonium hydroxide refers ium hydroxide solution al. The aqeuous soluum molybdate referred The ammonium molybdate roxide were dissolved in 2 dded slowly with stirlt solution containing the sus- Thesol id material precipitated,

and ammonium hy'd ring to the coba pended alumina. 'which had a pinkish color, was filtered off and washed twice by resuspe water and filtering. The color dicated considerab nding in 10liters of hot of the filtrate inle loss of cobal The final composit t molybdate. ion of the solid material was weight of cobalt molybdate The cake was dried in the -two hours at 200 F., during which time it assumed a characteristic dark approximately 20% by and 80% of alumina. oven for seventy reenish bin e color and a vitreous appearance. broken up into 10-20 mesh be sumciently hard to when it was these were found to pelleting unnecessary.

In the treating processes of this invention, the

' hydrocarbon feed stocks are contacted with the suitable means. In a conthe catalysts may be above catalysts by any tlliuous system, for example,

d bed in a reaction ch assed through this catalyst bed, or a moving catalyst bed or fluid catalyst system may -the. catalyst m r-current to or concurren through t e reaction zone; also be employed in which stock are mixed in a conis subjected to reaction be employed wherein streamcoil te hydrocar n stream Abatch system may the catalyst and feed tainer and the conditions. The

liquid or vapor phase dominate in any of these operations,

phase operation ma Y e ployed. The presence 3 898 988 i o I of hydrogen and/or carbon monoxide in the action mixture is greatly preferred. The reaction temperatures will depend largely on the treatment Q desired, but will generally be above 400 F. and below about 2000 1". When'it is desiredmerely to convert non-hydrocarbons to easily removable.

forms without substantial concurrent conversion of hydrocarbons, the lower temperatures are preferred, such as below about 900 F. Inthe con-.- version of hydrocarbons'by cracking and reforming, the higher temperatures, above about 800 F. and preferably above about 950 F. are generally employed. The lower temperature operations when used for non-hydrocarbon conversion, are generally carried out at pressures above about 150 lbs, and in the presence of at least about 1000 cu. ft. of hydrogen per barrel of feed. The higher temperature operations when used for hydrocarbon conversion, are generally accompanied by lower pressures and higher hydrogen ratios.

The following are examples of treating processes of this invention. In each instance in which sulfur-containing stocks were treated, the products were caustic washed .to remove the hydrogen sulfide formed.

Residua from distillation of crude oils containing various S, N and O- compounds may be treated to remove such compounds, by contacting these stocks in the liquid phase with the above catalysts. For example, by heating a residuum obtained by distilling the gasoline and gas oil from a high sulfur crude with. about 1% of its weight of cobalt molybdate on previously undried alumina gel, with hydrogen at a pressure of about 2000 lbs. and a temperature oi about 500 to 600 1". for about an hour the bulk of the sulfur, oxy

- gen, and nitrogen compounds contained in the stock may be converted to lower boiling compounds, largely hydrogen sulflde, water, and lower boiling nitrogen bases, which may be removed from the product by fractional distillation or washing with dilute caustic and with dilute mineral acid. The hydrocarbons are largely unaffected, but the product is greatly improved over the feed stock as regards suitability for use as fuel oil or as cracking stock.

Similar selective conversion of sulfur, oxygen, and nitrogen compounds may be obtained under the range of conditions outlined above for the lower temperature operations, i. e. at temperal tures below about 900 F'., and preferably below about 800 F., pressures above about 150 lbs. per square inch and up to about 10,000 pounds or more, hydrogen ratios above about 1000 cubic feet per barrel of liquid feed and up to 10.000 or more cubic feet per barrel, contact times of about 0.1

hour up to about 10 hours or more, and the same or other catalysts of this invention. For equivalent selectivity of conversion, operation at the higher temperatures in this range should be accompanied by lower contact times.

By. operation at somewhat higher temperatures, in the liquid or mixed phase, residual oils and the like may be treated with conversion of hydrocarbons as well as sulfur, oxygen, and nitrogen.

compounds. For example, by carrying out resid- 900 F. to 1000 F'. or more and lower pressures such as atmospheric to about 150 lbs., with contact times as low as about 0.1 second or less, with or without hydrogen, similar conversion of S, O. and N compounds takesv place, with concurrent production of substantial yields of fixed hydrocarbon gases, gasolines, and gas oils, which when period of about 18 hours.

freed of hydrogen sulfide, water, and low-boiling nitrogen bases, are improved motor fuels.

Lubricating oils stocks treated as in the lower temperature operation above have been greatly improved in viscosity index (Dean 0; Davis method) without appreciable loss in yield. As an example of a modification of this process, hydro gen was bubbled through a mixture of 150 ml. of lubricating oil stock and 15 g. of an unsupported cobalt molybdate catalyst at atmospheric pressure and a temperature of about 700F., for a After Washing the product with dilute caustic and dilute sulfuric acid, it was found to have a sulfur content of 1.7 against 3.0% for the stock: a viscosity, 8. U. at I". of 298 as against 595 for the stock, and a viscosity index of 49 as against 20 for the stock. Even better results may be obtained by operation under pressure and/ or by employing more emcient means of contacting.

Gas oils and coking distillates may'be treated either in the liquid phase or in the vapor phase. The following are examples of vapor phase operation:

A heavy gas ,oil from Los Angeles Basin crude was vaporized in the presence of 3,400 cubic feet of hydrogen per barrel of feed, and the mixture was passed at a temperature of 750 F., a pressure of lb. and a rate of 1 volume (of liquid feed) per volume of catalyst per hour over a bed of cobalt molybdate on alumina catalyst prepared as described above. The sulfur content of the gas oil was reduced by this treatment from 0.9%

to 0.2% with a recovery substantially of 100% by I volume, and was an improved cracking stock or Diesel fuel. There was no substantial conversion of hydrocarbons such as production of gasoline. Over 23 volumes of liquid feed were treated with- .out catalyst regeneration, and without apparent feed treated yielded a product in an 89% yield' which had a sulfur content of only 0.2%, compared with 3.5% for the feed stock, a reduction of about 94%. There was substantial conversion of hydrocarbons as well as sulfur compounds in this operation, since-the product contained 56% of gasoline, while the feed stock contained 1 only 18% of gasoline. This indicates a converuum treating operations at temperatures about I sion of over 46% of the higher boiling material in the feed to gasoline. The sulfur content of the gasoline-in the feed stock was 2.65%, while that of the product gasoline was 0.04

In a similar run the feed stock mployed was the same stock employed in the previous example except that the 18% of gasoline-was removed prior to the treatment. The treating conditions were similar, except that the feed rate was doubled. The product obtained from the first 12 volumes of feed in a yield of 86% had a sulfur content of 0.76% and contained 38% of gasoline of 0.17% sulfur content. v

A straight-run gasoline from Santa Maria Valley crude was passed in the Vapor phase in adcatalyst prepared as above (without carrier) at volume of catalyst per hour.

of H28) was essentially unchanged except for the reduction of the sulfur content, which was-0.12

for the product. This raised the octane number of the gasoline containinga 4' I a temperature of 1b., and a rate of .4 volumes 600' F. and a'pressure of 250 of liquid feed per The product (freed for the feed, and 0.06

ml. of tetraethyl lead per gallon from for the feed to '18 for the product, although the octane number without tetraethyl lead, -61, was substantinny-unchanged by the treatment.

In a .hydroforming operation,- a gasoline of low sulfur content having a boiling range of 220 to 273 F. and containing no oleflns and 14% aromatic hydrocarbons was converted in a 71% yield to a product of slightly wider-boiling range containing 3% oleilns and 50% aromatics.- The catalyst was a cobalt molybdatealumina catalyst prepared as described above, the feed rate was 1 volume per volume of catalyst per hour, the hydrogen ratio was 3400 cubic feet per straight-run.

bases.

barrel of feed, the length of the run was 2 hours,

the temperaturewas 950 F. and the pressure was 1001b.

In another operation, employing a cobalt molybdate (no carrier) catalyst prepared as above, with a feed rate of 2.! volumes per volume of catalyst per hour, a hydrogen ratio of 10,000 cubic feet per barrel ,of feed, a temperature of, 950 F. and a pressure of 250 1b., the length of the run being nearly 20 hours, a 78% yield of product gasoline of 0.09% sulfur content was obtained from a cracked gasoline containing 0.6% sulfur. The octane numbers of the feed containingno tetraethyl lead and 3 ml. of tetraethyl lead per gallon were 72 and 78 respectively, while those of the product were 75 and 86, respectively.

Besides the above, extract fractions obtained by selective solvent treatment of lubricating oils, transformer oils, kerosene, stove oils, gasolines, and like fractions have been treated in the presencevof the above catalysts, under conditions such as those described above, both in liquid and vapor phase, to obtain products much more suitable as aromatic solvents for use as thinners for lacquer, paint, varnish, and the like. Fractions from coal tar and shale oil are similarly improved by such treatment.

These catalysts, especially alumina catalyst, are particularly suitable for use at temperatures above about 950 F. up to 1500 the cobalt molybdate- F. and even 2000 1 Thus, they may be employed in fluid cracking, processes with or without hydrogen, or precombustion type crackingprocesse's,

as a substitute for, or in addition to, hydrogen,

and the presence of saturated low molecular weight hydrocarbons such as propane and butanes, is generally helpful.

ence of hydrogen sulfide, water, -ammonia,and the like. a

Although desulfurization and hydrocarbon conversion were emphasized in most of the speciflc examples given above, the feed stocks boiling above the gasoline range usually contain oxygen and nitrogen compounds such as phenols 7 As indicated, the cobalt molybdatecatalysts are effective even in the presiron; when I prepared by a,sos,aae

,and nitrogen bases, especially those of high molecular weight. These are rather dimcult to remove by ordinary extraction methods. BY treatments such as those shownin the above examples however, the phenol contents of such fractions have been reduced by 90% or more, apparently by carbons. By the higher temperature treatments, especially of verted to ammonia and to lower boiling nitrogen basessuch as pyrrole, pyridine, and quinoline homologs and the like, and by the lower temperature treatments, unsaturated nitrogen bases such as pyrrole and pyridine may be hydrogenated to saturated materials such as pyrrolidine and piperidine respectively, which are stronger All of theserelatively low-boiling converted nitrogen bases are useful chemicals. They are readily extractable from the products of the above treating processes by treatment with dilute mineral acids such as sulfuric or hydrochloric, and may be recovered from the acid extracts by making the extracts alkaline with a strong base such as caustic soda and skimming or distilling the, liberated nitrogen bases therefrom.

The treating processes of this invention may be employed in stages, or may be followed by other treating processes if desired. The nitrogen base extraction step described above may be considered as one such instance. It is sometimes desirable to treat products with concentrated sulfuric acid or clay or the like to provide further refinement; or a low temperature desulfurization treatment may be followed by a high temperature hydrocarbon conversion treatment of the types described above. Two or more treatinz processes of the types included in this invention may be carried on successively if desired.

By the term catalysts comprising cobalt molybdate it is intended to include cobalt molybdate itself, as well as cobalt 'molybdate supported on carriers such as clay, bentonite, ceramics, and metal oxides, especially hydrous metal oxide (including hydroxide) gels, and especially those gels which have not previously been dried. it has alsobeen found, however,

that catalysts comprising chromites of cobalt as.

well'as chromites and molybdates oi' the iron group elements related to cobalt, i. e., nickel and methods analogous to those described above for the catalysts comprising cobalt molybdate, are good catalysts for hydrocarbon treatment by the processes of this invention, the cobalt chromite and the catalysts supported on undried hydrous oxide gels especially those named above, being preferred. In the case of the chromites the method of preparation normally involves the precipitation of the metal (iron, cobalt, or nickel) chromate from a solution of a soluble metal salt and ammonium 'dichromate, preferably in the presence of the desired undried hydrous oxide. gel, by the addition of a slight excess of ammonium hydroxide, washing the product substantially free of soluble salts, and heating it to decompose the chromate to a lower form such asthe chromite.

By "catalytic reforming of hydrocarbon mixtures in the following claims it is intended to include, processes for conversion of compounds containing sulfur, oxygen or nitrogen to more readily removable compounds containing these elements, as well as processes involving reduction in molecular weight, dehydrogenation, polyconversion to water and hydro- 1 the higher-boiling fractions, the nitrogen bases in such fractions have been conmerization or alkylation, hydroforming or aromatization, and isomerization, of hydrocar-' stock is added thereto. By "hydrogenation it is meant to include only those processes in which there is a substantial net or overall consumption of hydrogen. Processes ,in which there may be incidental hydrogenation of molecular fragments, but the hydrogen may be supplied by concurrent dehydrogenation, aromatization, and the like, of the hydrocarbon mixtures, and which involve primarily conversion of sulfur, oxygen, and nitrogen compounds, without substantial overall consumption of hydrogen, are definitely within the scope of this invention. For example, we may desulfurize cracked gasolines under conditions such that some of the olefins therein are hydrous metal oxide gel.

hydrogenated or cyclized. The "hydrocarbon mixtures include fractions from petroleum, coal tar, or shale, which may result from distillation, pyrolysis and/or extraction, and like processes, and may or may not contain sulfur, oxygen and nitrogen compounds.

Although only certain sulfur, oxygen and nitrogen compounds have been disclosed specifically, thev above processes are applicable to all other non-hydrocarbons found in impure hydrocarbon fractions, such as naphthenic acids, and other compounds containing sulfur and/or oxygen, and or nitrogen.

Modifications of the invention which would occur to one skilled in the art are to be included in the scope of the invention as defined in the following claims:

I claim: I

l.'A process for the catalytic reforming of hydrocarbon mixtures which comprises contacting said mixtures at a temperature between a'bout 500 F. and about 1000" F. with a catalyst comprising a compound selected from the class consisting of chromites and molybdates of iron, cobalt and nickel precipitated on a previously undried hydrous metal oxide gel.

, 2. A process for the catalytic reforming of hy- I drocarbon mixtures boiling above the gasoline range which comprises contacting said mixtures in the presence of a reducing gas at a temperature between about 500 F. and about 1000' F. with a catalyst comprising a compound selected from the class consisting of chromites and molybdates of iron, cobalt and nickel precipitated on a previously undried hydrous metal oxide gel.

3. A process forthe catalytic reforming of hydrocarbon mixtures boiling above. the gasoline range which comprises contacting said mixtures in the presence of hydrogen at a temperature between about 500 F. and about 1000 F. with a catalyst comprising a molybdate of a metal selected from the class consisting of iron, cobalt and nickel precipitated on a previously undried hydrous metal oxide gel.

4. A rocess for the catalytic reforming of hytating said molybdate between about 500 drocarbon mixtures boiling above the gasoline range which comprises contacting said mixtures in the presence'of hydrogen at a temperature between about 500" F; and about 1000 F. with a catalyst comprising a chromite of a metal selected from the class consisting of iron, cobalt and nickel precipitated on a previously undried 1000 F. with a catalyst comprising cobalt molybdate precipitated on a previously undried alumina gel.

7. A process for the catalytic reforming of hydrocarbon mixtures boiling above the gasoline range which comprises contacting said mixtures in the presence of hydrogen at a temperature between about 500 F. and about 1000 F. with a catalyst comprising a molybdate of a metal selected from the class consisting of iron, cobalt and nickel precipitated on a previously undried hydrous metal oxide gel, said catalyst having been prepared by a method comprising precipifrom a solution containing a salt of said metal and ammonium molybdate in the presence of an undried hydrous metal oxide'gel, by th addition of. ammonium hydroxide.

8. A process for the catalytic reforming of hydrocarbon mixtures boiling above the gasoline range which comprises contacting said mixtures in the presence of hydrogen at a temperature F. and about 1000 F. with a catalyst comprising a chromite of a metal selected from the class consisting of iron, cobalt and nickel precipitated on a previously undried I hydrous metal oxide gel, said catalyst being prepared by a method comprising precipitating thechromate of said metal from solutions of a salt of said metal and ammonium dichromate in the presence of an undried hydrous oxide gel by the addition of ammonium hydroxide, washing the precipitate and heating it to decompose the chromate to the chromite.

9. A process according to claim 2 in which the reducing gas is carbon monoxide.

10. A process according to claim 2 in which the hydrous metal oxide gel is alumina gel.

11. A process according to claim 2 in which the catalyst is cobalt molybdate precipitated on previously undried alumina gel.

12. A process according to claim 2 in which the reducing gas is ydrogen and the hydrocarbon mixture is aresidual on stock.

- ALVA c. BYRNB.