US2094128A

US2094128A - Chemical process

Info

Publication number: US2094128A
Application number: US732656A
Authority: US
Inventors: Wilbur A Lazier; John V Vaughen
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1934-06-27
Filing date: 1934-06-27
Publication date: 1937-09-28
Anticipated expiration: 1954-09-28

Description

Sept. 28, 1937' v w, LAzlER ET AL 2,094,128

CHEMICAL PROCESS Filed June 2'7, 1934 A IL RESERVQIR GIL FEED DISTRIBUTOR HEAD FUZED QUARTZ E FURNACE D Y HEATING ELEMENT a CATALYST BED FUZED QUARTZ GAS METER CDN NSER INVENTORS Wrlbur flrfhur Layer 'AITORNEY.

Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE CHEMICAL rnocnss Application June 27, 1934, Serial No. 732,656

Claims.

This invention relates to the production of low boiling hydrocarbons from petroleum fractions. More particularly it relates to the use of catalysts in such cracking or pyrolyzing operations.

5 The art of converting high molecular weight hydrocarbons into'more valuable products of lower molecular weight and correspondingly lower boiling point by thermal means, with or without the aid 01 catalysts, has been practiced for some time. The use of gaseous boron halides, and the use of solid catalysts have been recommended. One of the most efiicient processes for pyrolyzing hydrocarbons consists in heating the hydrocarbon mixture to a moderate temperature to cause almost complete volatilization and then conducting the vapors thru a relatively hotter zone which causes thermal decomposition. The gases and vapors are then quickly cooled and the products obtained are found to consist of gases such as acetylene, methane, ethylene, and ethane, and of intermediate liquid hydrocarbons useful as gasoline. It has been recognized that the substances of which the hot-zone walls are constructed may exercise a catalytic influence on the reaction. This influence is manifested in an activation of the higherhydrocarbons, which generally results in a lowering of the required cracking temperature, with accompanying decrease in the amount of wasteful gas formation, which in turn results in increasing the yield of valuable intermediate liquid hydrocarbon products.

- Various catalytic compositions have been sub- Jected to tests but none of the materials known to the prior art exhibit such pronounced activating tendencies toward hydrocarbons as the catalysts employed in the present invention. Indeed, certain so-called catalysts of the prior art are so low in activity that a comparatively long time 40 of contact of the hydrocarbons therewith is required, and this results in too severe cracking, i. e., the carbon chain is disrupted or broken into carbon and gaseous fragments which are too small for successful commercial utilization. Furthermore, the temperature at which certain thermally unstable catalysts may be used is limited to a range where the desirable type of cracking is thermodynamically impossible. This invention has as an object the provision of a process wherein high molecular weight bydrocarbons are pyrolyzed to lower molecular weight bons. A further object of the invention is the provision of catalysts for this pyrolyflnl operation. Other objects will appoarhercinafter.

(Cl. l9652) These objects are accomplished by the follow- V ing invention wherein a high molecular weight hydrocarbon in the vapor phase is brought in contact at an elevated temperature with a catalyst comprising a solid metallic element of the 5 sixth group intimately associated and preferably combined with a solid non-metallic element also of the sixth group.

It has been found that sulfide catalysts, particularly molybdenum sulfide and chromium sul- 1 i'omolybdate or similar substances, when used in gas-phase cracking processes, definitely activate the hydrocarbons undergoing pyrolysis. The following examples illustrate the methods of preparation of the improved pyrolysis catalysts and the 15 results obtained therewith in the cracking. of heavy petroleum oils. The examples are-not to be regarded as limitative, but merelyas illustrative.

Example 1 20 A solution of commercial chromium nitrate was first prepared by dissolving 1500 grams of chromium nitrate in 28 liters of water at a temperature of about 45 C. A second solution 25 containing 1720 gramsof ammonium molybdate in 9.0 liters of water was added to form an apple green precipitate of chromium molybdate. Hydrogen sulfide was then passed into the slurry for a period of about four hours, during which 30 time the precipitate was changed from-apple green to a dark brown color. By this treatment the chromium molybdate was converted in greater part to chromium sulfomolybdate. The prodnot was filtered from the mother liquor and 9 5 dried at C. After drying, the product was crushed to a suitable grain size for loading into the pyrolysis tube.

The apparatus for conducting the catalyzed pyrolysis of the high molecular weight hydro- 40 carbons consisted of a stainless steel tube wall by V bore and 36" in length) filled with crushed fused quartz and a central portion of granular catalyst. This reaction chamber was heated by a suitable electrical resistance furnace and the temperature controlled and recorded by means of thermo-elements fastened to the tube. The tube was mounted vertically, and the quartz and catalyst mass was supported by a 5 glass rod. The oil or hydrocarbon mixture entered at the top of the tube at a suitable rate and the products issued from the lower end' where a suitable condenser was attached.

In the attached drawing, oil from the. oil reservoir A.is fed through the distributor h B, and comes in contact with the fused qu C, then the catalyst bed D interposed between beds (2 and C of fused quartz. These are contained in a tube in a furnace E, the tube being heated by heating element F. The material passes through valve G and condenser E, whence the the furnace was heated to the desired temperature and a sample of a petroleum fraction boiling at 190-270 C. corresponding to a furnace oil was passed into-the top of the tube at a steady rate of about cc. per hour. The products were passed thru the water cooled condenser, to which there was connected a gas meter for determining the quantity of non-condensable gases. The liquid hydrocarbon mixtures obtained were conveniently analyzed by the Engler method, which consists in measuring the temperature at which successive fractions (percentages) of the oil distill. The same procedure was carried thru with an inexpensive grade of cracking stock or coke distillate, in which case a small quantity of steam was used with \the oil to prevent excessive carbonization.

In Table I there are recorded the comparative results, expressed as gasoline yields, obtained during the catalyzed and uncatalyzed pyrolysis of the above described furnace oil. poses of this example, the hydrocarbons boiling at 45-200 C. in the standard Engler distillation have been considered as gasoline.

TABLE I Gasoline yield in catalyzed and non-catalyzed Pyrolysis of furnace oil Yield of gasoline Temperature oi pyrolysis Non cam Catalytic lyflc Percent Percent 6. 0 5. 0 9. 5 6. 5 13v 5 10. 3 20. 0 17. 0 3D. 0 26. 0 30. 0 28. 5 28. 5 25. 0 ll. 0 21. 5

It is evident that with a catalyst it is possible to operate at a lower temperature while maintaining the gasoline yield, or to operate at a given temperature and obtainappreciably higher yields. Furthermore, when an account is made of the gas formation during pyrolysis (Table II) it is again evident that definite advantages are offered by the use of catalysts of the type utilized by this invention.

In the following table the volume of gas produced is recorded for each volume of liquid gasoline when the process is operated to produce the yield indicated in the first column.

For the pur- Tasun In this way it has been demonstrated that for a given yield of gasoline,'considerably more of the sto l: is lost in gas formation with the noncatalyze reaction than with the improved process of this invention.

As an alternative procedure, similar results may be obtained by employing a catalyst prepared as follows:

A 25% solution of ammonium molybdate is treated with hydrogen sulfide until the product is converted to soluble ammonium sulfomolybdate. To this solution there is added the theoretical amount of a solution of cobalt nitrate to cause complete precipitation of cobalt sulfomolybdate. The precipitate is filtered, washed and dried at 110 0., after which it is brought into suitable physical form by crushing and screening to the desired size, or by pulverizing and briquetting.

E'mample 2 A solution of ammonium sulfomolybdate is prepared as described in the preceding paragraph, which is then acidified slightly with mineral acid, preferably sulfuric acid. A precipitate of molybdenum sulfide is obtained which may be filtered off and dried. The physical form of the product is made suitable for use as described in Example 1. The furnace oil employed in the experiments of Example 1 was passed over 5 cc. of this catalyst at the rate of 57 cc. per hour at atmospheric pressure and a temperature of 660 C. The gasoline yield was 29.7% as compared with a yield of 26% and 28.5% recorded in Table I for the uncatalyzed reaction at 650 C. and 7 00 C.,-respectively.

Although certain definite catalyst compositions have been described in the examples, the invention is not limited to the use of these catalysts. Suitable catalysts may be prepared from one or more metallic elements of the sixth group intimately associated with but preferably combined with the solid non-metallic elements also of the sixth group. The catalysts may also include one or more metallic elements of the first, fifth, seventh, and eighth groups intimately associated with but preferably so intimately associated as to be combined with one or more solid non-metallic elements of the sixth group. The sulfides of iron, cobalt, copper, silver, vanadium, nickel, and manganese may be used in conjunction with those of the sixth group metals. tallic sulfides, selenides, and/or tellurides, may be mechanically mixed with or chemically combined with the sixth group sulfides. Thus, a mixture of precipitated copper and molybdenum sulfides may be used. A further variation in the preparation of the catalysts of the present invention consists in mixing coprecipitated chromium and These complex memolybdenum oxides with sulfur. A still further variation is the admixture of dry active chromium oxide and/or dry active molybdenum oxide with sulfur, the whole being bound together with a suitable binding agent. Similar mechanical mixtures may be prepared with compounds of the other metallic elements and with selenium, tellurium, etc. Of the sixth group metal catalyst components chromium and molybdenum are perhaps the most useful, altho tungsten and uranium may also be used.

Active catalysts may also be prepared wherein the constituent elements are bound together in compositions of the characteristics of chemical compounds. This type of catalyst may be formed in the dry way or in the wet way. A compound having the chromium and molybdenum component in true chemical combination with oxygen, such as chromium molybdate, for example, may be formed and the non-metallic activating constituents, such as sulfur, introduced in several ways. The chromium molybdate may be treated with hydrogen sulfide, or mixed with sulfur or with some organic or inorganic sulfide in the wet condition. The substitution of the non-metallic solid element of the sixth group in the compound will take place either in the wet condition, as in the case of treating a solution or suspension with hydrogen sulfide, or in the dry condition as when the catalyst is brought up to reaction temperature, as in the case of the admixture of powdered sulfur. The oxygen may also be replaced by sulfur, selenium, or tellurium by heating the oxides in a current of the sixth group non-metal hydride such as hydrogen sulfide, hydrogen selenide, or

hydrogen telluride, or in a current of sulfur vapor.

Hydrogen selenide or hydrogen telluride may be substituted for hydrogen sulfide if the proper adjustments are made for the difference in characteristics of these gases. Atho the sulfides mentioned are preferred, the analogous selenium compounds are similarly active, and for some purposes have definite advantages over the sulfide catalysts.

In carrying out the wet method of catalyst preparation as outlined in the examples given above, it is not necessary to follow all the steps in detail. The use of chromium nitrate as the source of the chromium component of the various catalysts has been mentioned. Other salts of chromium may be used, for example the chloride, sulfate or acetate, necessary adjustments being made for the difference in molecular weight of the various salts. Ammonium molybdate may be replaced by other sources of molybdenum, such as sodium paramolybdate, care being taken in this case that the precipitated material is washed at least moderately well.

It is not necessary to follow the explicit directions for sulfiding the precipitates as outlined in the examples. sulfiding agents other than hydrogen sulfide, for example ammonium or sodium sulfide, or polysulfide may be used. In the case of the sodium salts it is desirable to wash out the excess of sodium salts before drying.

The sulfiding treatment is susceptible of wide variations. Various degrees of sulfiding may be used for certain purposes, altho it is preferred not to sulfide the catalysts completely, that is, not to convert all of the oxygenated metal to sulfided metal.

The recovery of dissolved molybdenum from the mother liquor by the addition of dilute acid is not limited to dilute nitric acid, but this step may be accomplished by other mineral acids.

The catalyst compositions are not necessarily confined to the ratios of the various constituents given in the examples. It is possible to obtain a catalyst'of high activity from preparations containing equivalent amounts of chromium and molybdenum, or of cobalt and molybdenum as well as from those containing either chromium or molybdenum in excess.

The process as described in the examples is not limited to the use of furnace oil, but any hydrocarbon mixture capable of being cracked and handled as described may be used. It is often desirable to 'pyrolyze lighter hydrocarbon mixtures than furnace oil for the production of lower boiling substances. Kerosene and virgin light crude distillates may be treated in the manner described, and not only are lower boiling hydrocarbons formed, but these when used as gasoline are found to have acquired high anti-knock rating as a result of the pyrolysis. Other petroleum fractions known as coke distillate, gas oil, paraffin wax distillate, or the foots oil obtained therefrom may be used in the process of the present invention. With these substances, as also when crude oil'is used, an auxiliary flash distilling operation may be desirable. When distillates from high-sulfur crudes are pyrolyzed, it is found that the products are relatively free from the sulfur compounds present in the original crude oil.

With respect to temperature and pressure, the process is not limited to the values given above. Altho excellent results in producing gasoline are obtained at about 700 C., it is sometimes desirable to vary the temperature from 450 to 1000 C. The process may be operated at pressures varying from sub-atmospheric to pressures somewhat in excess of atmospheric pressure. In general, it is more economical and preferable to operate between atmospheric pressure and a pressure of 10 atmospheres, but in certain instances it is advantageous to use pressures of from 0.5 to 50 atmospheres.

It is not intended to confine the operation of the process to the rate of oil flow mentioned in the examples. While a liquid space velocity of approximately 13 volumes of oil per volume of catalyst per hour is preferred at the temperatures specified in the examples, yet under certain circumstances it is desirable to increase this to a space velocity as high as 65 volumes per catalyst volume per hour. Furthermore, it is sometimes desirable to lower the space velocity to about 5, depending on the results desired. In general, high space velocities at a given temper ature tend to limit the extent of cracking, while low space velocities tend to increase the proportion of very low boiling hydrocarbons in the product. Thus, variations in temperature will often necessitate corresponding changes in the space velocity for the attainment of maximum results. For a given result the space velocity and temperature should be adjusted with respect to each other. The loss of yield at higher temperatures as shown in Table I may be reduced by increasing the space velocity to compensate for increased temperature. The results recorded in Table I were determined at the same space velocity which was not necessarily the optimum for each temperature shown.

It is sometimes advisable, as pointed out above, to use a gaseous diluent along with the hydro carbon mixture. Steam may thus be used, but inert gases such as nitrogen, carbon dioxide, or

4 y recycled hydrocarbon gases may also be use with advantage.

The above description and examples are intended to be illustrative only. Any modification of or variation therefrom which conforms to the in the vapor phase at a temperature of 450 C. to 1000 C. and a pressure below 10 atmospheres at a space velocity of 5 to 65 volumes of liquid oil per volume of catalyst per hour, in the absence of added hydrogen, to the gas prior to pyrolysis in contact with a catalyst comprising as an essential component chromium sulfomolybdate.

3. In a process for the pyrolysis of hydrocarbons, the step which comprises bringing furnace oil, in the vapor phase at a temperature of 700 C. and at apressure between 1 and atmospheres at a space velocity of 13 volumes of liquid oil per volume of catalyst per hour, in the absence of added hydrogen, to the gas prior to 5 pyrolysis in contact with a catalyst comprising 5 spirit of the invention is intended to be included essentially chromium suliomolybdate. within the scope of the claims. 4. In a process for producing hydrocarbons We claim: boiling at 45 C. to 200 C. in the standard Engler 1. In a process for producing hydrocarbons distillation, the step which comprises bringing 10 boiling at 45 C. to 200 C. in the standard a hydrocarbon heavier than gasoline in the va- Engler distillation, the step which comprises por phase at a temperature of 450 C. to 1000 C, bringing a hydrocarbon heavier than gasoline, and at a pressure below 10 atmospheres, at a in the vapor phase at a temperature of 450 C. space velocity of 5 to 65 volumes of liquid oil to 1000 C. and a pressure below 10 atmospheres per volume of catalyst per hour in the absence 15 at a space velocity of 5 to 65 volumes of liquid of added hydrogen to the gas prior to pyrolysis, 15 oil per volume of catalyst per hour, in the abin contact with a catalyst comprising as an essence of added hydrogen, to the gas prior to sential component ametallic element of the sixth pyrolysis in contact with a catalyst comprising group of the Periodic Table combined with bias an essential component a sulfomolybdate of a valent sulfur, said catalyst being prepared by metal selected from the group consisting of precipitating as a sulfide the said metallic cle- 20 chromium and cobalt. ment from an aqueous solution containing the 2. In a process for producing hydrocarbons ammonium salt of said metallic element. boiling at 45 C. to 200 C. in the standard 5. In the process for producing hydrocarbons Engler distillation, the step which comprises boiling at 45 C. to 200 C. in the standard 2 bringing a hydrocarbon heavier than gasoline, Engler distillation, the step which comprises bringing furnace oil in the vapor phase at a temperature of 450 C. to 1000 C. and at a pressure between 1 and 10 atmospheres, at a space velocity of 13 volumes of liquid oil per volume of catalyst per hour in the absence of added hydrogen to the gas prior to pyrolysis, in contact with a catalyst comprising essentially chromium sulfomolybdate.

WILBUR A. LAZIER.

JOHN V. VAUGHEN.

CERTIFICATE OF CORRECTION.

Patent no 2,095,12

September 28, 1957.

WILBUR A LAZIER, ET AL.

It is hereby certified that error appears in' the printed specification of the above numbered patent requiring correction as follows: Page 1 first column, lines 514,-55, claim 5, strike out the words "the pyrolysis ofhydrocarbons" and insert instead producing hydrocarbons boiling at 1 5C. to 200 in the standard Englerdisti llationrandthat the said Letters Pat-v ent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of February, A. D. 1958,

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.