US2628890A - Process for the decomposition of hydrocarbons - Google Patents

Description

Patented Feb. 17, 1953 PROCESS. FOR THE DECOMP.OSITION' F HYDROCARBONS James H. Shapleigh', Wilmington, Del-.,.assignor.

to Hercules Powder Company,

Wilmington,

Del-L, a corporation of Delaware NoaDrawing. Application June 20, 1946,. Serial No. 678,163

4 Claims; 1

This. invention relates to the catalytic decomposition of'hydrocarbons and more particularly to such a processutilizing hydrocarbons containing sulfur in amounts. greater than O .5grain per 100 cu. ft. of vaporized hydrocarbon.

In the commercial production of hydrogen, as now practiced, a. gaseous mixture of. steam and substantially sulfur-free hydrocarbon is. passed over a heated catalytic agent containing nickel. In accordance with oneprocedure the process is carried out in' a furnace fired through the arch, with flue. gases withdrawn from the base of the furnace and; with the steam-hydrocarbon mixtureipassing through the" catalyst tubes parallel to and concurrent: with the flow of heat media. The cracked gases are then passed through a secondary furnace and air introduced in order to obtain anoptimum. temperature to reduce the methane content of the: exit gaseslt'o a'valuebelow 1%. There resultsamixed- Nz-Hz gas as'a; necessity bythi's method; In commercialpracticeof this-process the. quantity of. steam used. is customarily of the order of 4 to 5 molsperm'ol of carbon in the hydrocarbon in order to obtain the heat pickup requiredv for the endothermic reaction within the cracking tube without obtaining excessive tube wall temperature- In accordancewith another and more efficient method". described in Reissue: Patent No. 21,521 to J H; Shapleigh, the steam-hydrocarbon mixturepasses essentially countercurrent to a plurality of firing points spaced along the vertical: wall of the furnace, the flue gas in this instance leaving from the top of the furnace. In thisprocess, the CH4 content of the exit gas is obtained: directly, even with hydrogen alone produced, at: values. from 0.3% downward depending upon. the. particular. manner in. which theifurnace operation is conducted. The CH4 content can; be 0.1% or less if desired. Steamgas ratios less than Zmay beutilized when using natural. gas as the. hydrocarbonv and are. not limited as in the first procedure. described- When operating'with the above processes the cracking efficiency, or per cent cracking obtained, is controlled by the steam gas ratio, the spacevelocity, the catalyst quality and the reaction temperature. Having selected'a suitable steamgas ratio, space velocity and catalyst, in accordance withiprinciples: well known in the art, the pen ent; crackinggisi obtained. by a suitable adjustment of the. temperature; within the: limita t ions' of'the particular process; In practice such processes are'condu'cted' at temperatures just sufficient to yield the desired conversion, or cracking efficiency, based upon raw materials com-F.

paratively free of sulfur.. Higher temperatures are unnecessary and have been judged..disad-.

vantageous' and have been avoided; lower temperatures place a limit upon cracking efficiency The lowest temperature required in practiceato nil to-0Z2.grain.per 100 cu. ft.

Y practice of (1) severely limits the production of Howevenwhen sulfur is. present in even minor amounts there. is. a disadvantage because nickel catalyst. is readily susceptible. to. poisoning, and

when. sulfur. is: present in. amounts. greater than about 0.5. grainv per 100.cu. ft. the disadvantage has beendeemedgreat enough. by the" hydrogen producer. thathehas. resorted to sulfur removal by. NaOH. or othermeans. Thus, where hydro; carbons containingabout. 0.5.. grain per liOU'cu. ft. are utilized,.sulfur removal systems are. employed; Ontheother hand, where such systems are.- not. employed. it is. recognized in the art that thehydr-ocarbon. has been substantially free of. sulfur. Because of. this knowledge thepatented art. has generally advised against the use of hydrocarbons containing appreciable amounts of sulfur. Thus, one patentee (Williams-U'. S. Patent No. 2,119,565) states that certain substances such as. the halogensand compounds of sulfur. greatly decrease or even completely inhibit the activity of nickel catalysts for. this purpose and therefore advises that the presence of these and other catalyst poisons be avoided by'using salts. other than the chlorides in preparing. the catalytic materialsandby employing gaseswhich are free from. compounds of sulfur. Schmidtand Nieman, U. S. Patent No. 1,882,977, state: "It is advisable. to operate. with. purified gases, especially those which have been freed. from sulfur. Wietzel, Haller. and Hennicker, U. S:. Patent No. 1,934,836, state; If. the initial substances vare very much polluted, especially with organic compounds of sulfur, these must be removed Hanks and Freyermuth, U. S. Patent No. 1,943,821, state: The flushing gas should be substantially free from substances which are poisonous for the hydrogen-producing catalyst, such as sulfur compounds, halides and the like. The art is full of such warnings and limitations on sulfur content of hydrocarbon gases and well illustrates the prevailing attitude against their use.

In addition, commercial practice in the manufacture of hydrogen from hydrocarbons has been (11) to. utilize those hydrocarbons which are substantially free of sulfur and/or sulfur compounds, or: (2) to provide suitable preliminary treatments for. removing the sulfur when it approaches 0.5 grain per cu. ft. of hydrocarbon gas. The

. 3 hydrogen both from the standpoint of location of plants and quantity produced, since it avoids the use of many hydrocarbons, particularly liquid hydrocarbons, which aside from their sulfur content, are otherwise quite suitable. In the practice of (2) preliminary treatment to remove sulfur is required and this involves additional equipment, manpower and materials and is both time consuming and expensive. In the case of liquid hydrocarbons such as pentane, vaporization is practiced, with sulfur removal carried out in the vapor phase; for heavier hydrocarbons, the purification process becomes complex. Since sweet natural gas is generally sold with a guarantee that it will not have more than 1 grain H2S per 100 cu. ft. and with contracts generally not available which will guarantee less than this amount, it has been the case that the hydrogen producer has had to protect his production by installing sulfur removal equipment even though the source of the gas might run less than 0.5 grain per 100 cu. ft. for most of the time. So far as is known commercial hydrogen plants using hydrocarbon raw materials containing sulfur in quantity higher than approximately 0.5 grain per 100 cu. it, do not exist today without sulfur removal systems. Now in accordance with the present invention it'has been discovered that hydrogen may be produced from hydrocarbons containing sulfur by a one-step process and without the necessity for preliminary treatment of the hydrocarbon to remove sulfur. This is accomplished by passing a mixture of the sulfur-containing hydrocarbon and steam over a nickel catalytic agent at temperatures which have heretofore been avoided and which are higher than the optimum temperature heretofore used in the art of producing hydrogen from a hydrocarbon substantially free from sulfur under comparable conditions of cracking efiiciency, steam-carbon ratio, space velocity, and. catalyst quality. High cracking efiiciencies are obtained by this improvement, which have heretofore been regarded as impossible, and from a range of sulfur-containing hydrocarbons, from those moderate in sulfur content, such as propane, to those heavy in sulfur content, such as crude oils. j Thus, in carryin out the process of this invention sulfur-containing hydrocarbons are reacted under specific conditions of steam-hydrocarbon ratio, space velocity and catalyst quality and the temperature of the reaction carried out at above the optimum temperature that would prevail with a sulfur-free hydrocarbon gas under the same conditions of steam-carbon ratio, space velocity and catalyst quality. 1 Having described the invention generally, the

'4 following examples are given to illustrate the advantages thereof.

EXAMPLE 1 A catalyst comprising 25% nickel, 25% zirconium silicate, and 50% magnesia by weight was made up in the form of pellets and placed in the cracking tube of a hydrogen furnace. A sulfur-free hydrocarbon and steam were then passed through the cracking tube under conditions and with results set forth in column 1, Table I, below. A petroleum oil containing 1% sulfur was then atomized, vaporized, mixed with steam and passed through the cracking tube under the same conditions of steam-gas ratio, space velocity, catalyst quality and temperature. The per cent cracking or cracking efiiciency fell off to as shown in column 2, Table I. The temperature was then increased C.'and the crackin efficiency rose to 98% as shown in column 3, Table I.

Table I.Comparison of cracking ejficiencies utilizing sulfur-free and sulfur-containing hydrocarbons Petroleum Oil Petroleum Oil Containing Containing Sulfur-Free 100 Grains of 100 Grains of Hydrocarbon Sulfur Per Sulfur Per 100 Cu. Ft. 100 Cu. Ft. of Gas of Gas Cracking Efficiency percent 98 90 98 Steam-Carbon Ratio... 2:1 2:1 2:1 500 500 500 n i l l Mi 25% 25% 50% 2 Same as 1.

EXAMPLE 2 A catalyst comprising 10% nickel, 10% aluminum oxide, and 80% magnesia by weight was made up and the same procedure followed as in Example 1. Conditions of treatment and results are shown in Table II below. The sulfur-free hydrocarbon gave a cracking efficiency of 99% as shown in column 1. The petroleum oil (same as used in Example 1) containing 100 grains of sulfur per 100 cu. ft. of vaporized hydrocarbon, gave a cracking efficiency of 88% under the same conditions of steam-carbon ratio, space velocity, catalyst quality, and temperature, as shown in column 2. Raising the temperature from 800 C. to 900 C. increased the cracking efficiency from 88% to 98% as shown in column 3. A further increase in temperature to 950 C. gave a cracking efficiency of 99%.

Table II.C'omparison of cracking ejficiencies utilizing sulfur-free and sulfur-containing hy- V drocarbons Petroleum Oil Petroleum Oil Petroleum Oil Containing Containing Containing Sulfur-Free 100 Grams of 100 Grains of 100 Grains of Hydrocarbon Sulfur Per 100 Sulfur Per 100 Sulfur Per 100 Cu. Ft. of Gas Cu. Ft. of Gas Cu. Ft. of Gas Cracking Efficiency percent" 99 88 98 99 gteam-( Jarb%1;Ratio 2:1 2:1 2:1

pace e oci 500 600 Catalyst 500 Temperature C 800 800 900 950 Same as 1.

LA catalyst comprising nickel, 40% zirconium silicate and 50% magnesia by weight was made up .and the'sameprocedure followed as in Example .1. Conditions or treatment and results are shown in'Table III below. Thesulfur-iree hydrocarbon gave. a cracking. efficiency of 97-98% as shown in column'l. Under thesame conditions of steam-carbon'ratio, 'space'velocity, catalyst quality and temperature the 'petroleum'oil utilized in Example 1 and containing 100 grains of sulfur per'100 cu. ft. of vaporized hydrocarbon gave a reduced cracking efilciency of 88% as shownin co1umn2. However; when the temperature was increasedto 900 C. the cracking eflicie'ncy rose to 97 98% as shown in column 3. The sulfur content of the oil was then increased tothe 'abnormally'h'igh value of'1000 grains per 100 cu. ft. of vaporized hydrocarbon. The resulting cracking efliciency of 93%,, when compared with the cracking efficiency of 88% obtain'ed when treating a petroleum oil containing "In accordance "with this invention is. mixture or steam and sulfur-containing hydrocarbonsare passed through a catalyticbed heated to'sa new and higher level of temperature:thanzpreviouslyused in the art to give the unexpectedtcracking,

efliciency. Both hydrocarbons which :arewnormally gaseous and those which :are :normally liquid may be treated.

Steam to carbon ratios and space velocities Temperatures utilized will depend on the.

steam to gas ratio, space velocity, catalyst qual-' ity, amount of sulfur presentand'the desired cracking efficiency. By selecting proper values for steam to gasratios, space velocities, catalyst quality and cracking efficiency in accordance with the teachings of the prior art in connection with the treatment of sulfur-freehydrocarbons,

Table III.--.C"ompar2',son of cracking ejficz'enctes .utilizing sulfur-free and suljuracontaining hydrocarbons Petroleum Oil Petroleum Oil Petroleum Oil I Containing Containing Containing Sulfur-Free '100 Grains of 100 Grins of ,000'Grains of Hydrocarbon Sulfur Per 100 SulfurPer 100 tulfur. Per 100 Cu. Ft. of Gas Cu. Ft. of Gas Cu. Ft. of Gas Cracking Efficiency I percent. 97-98 88 97-98 93 Steam-Carbon Ratio 2:1 2:1 2:1 2:1 Space Velocity 500. g 500 500 500 Catalyst Temperature C 800.. 800 900 .900

1 sm g a 10% 40% 1 Same as'l. .EXAMPLEA the temperature utilized W1l1 then=depend-onthe The results of tests on heavy 011s in plant size 45 amount of sulfur present. Sulfur content; subapparatusfshown in Table IV below, are illustrativeof the. highly unexpected resultsobtained in. accordance with this invention. Theseoils contained from 0.5% sulfur to.2.5% sulfur and Table IV.-Results of tests on heavy oils P. S. 300 Diesel 011 Crude Oil Containing ggg gg Containing 0.5% Sulfur 3 Sulfur 2.5% Sulfur Cracking Efliciency percent. 96 97. 5 96.7 Steam, Oil Wt. Ratio-.." 4. 3:1 5.3:1 5.121 Space Velocity 548 795 595 Catalyst I Exit Temperature". 0-- 750 800 900 i Ni-ZrSiOrMgO 8 Same as 1.

stantially less than about0.5 grain per 100.cu. ft. of gas being treated normally does not appre ciably poison the catalyst andhence requires no substantial increas in temperature. .Sulfur content in excess of 0.5 grain per 100 .cu..ft .of-igas being treated has a sufficient poisoningaeifecton the catalyst to require sulfur removal equipment in the present day art. Concentrationsof lgrain per cu. ft. have been consideredas-simply unusable. For concentrations .in excess of .1 grain per 100 cu. ft. and even with oils having suflicient sulfur to be customarily expressed on a per cent by weight basis, forexample, 1% sulfur,-I have found that temperature increase to about C. higher than optimum temperatures utilized for the treatment of-sulfur-freehydrocarbons under analogous conditions will give high commercial efliciencies not heretofore obtained without prior sulfur removal. i V i In the practice of this invention it is preferred to use a nickel catalyst containing more than 10% nickel by weight. Suitable catalysts of this type are nickel-zirconium silicate-magnesia, nickelaluminum oxide-magnesia, nickel-zirconium silicate, nickel-aluminum oxide, nickel-diaspora, nickel-magnesia, nickel-pumice, nickel-titanium oxide, etc. These catalysts may be made by any of the methods of the prior art and are desirably given a preliminary tempering treatment with heat prior to use.

According :to iusages.

Space velocities will generally- -'The"various expressions as used in the specification and claims are defined as follows: sulfurcontaining hydrocarbon is defined as a hydrocarbon containing more than 0.5 grain of sulfur per 100 cu. ft. of vaporized hydrocarbon treated; optimum temperature is defined as the lowest temperature required in practice to obtain a given per cent of cracking with a'given steam-carbon ratio, space velocity and catalyst quality; crack.- i'ng efficiency is defined as per cent conversion of the carbon in the hydrocarbon to CO; steamcarbon ratio is defined as the ratio of the mols of steam to the mols of carbon in the hydrocarbon being treated; thus in the case of propane a ratio of 2:1 would mean 6 volumes of steam for each volume of propane; space velocity is defined as the volume of steam-hydrocarbon mixture per volume of catalyst per hour; catalyst quality is defined as the activity of the catalyst under a given set of conditions, i. e., type and age of catalyst and conditions of use.

The process of the present invention is particularly useful in the manufacture of hydrogen by the catalytic decomposition of hydrocarbons. The invention is not, however, limited to hydrogen 'prod uction but is applicable, as well, to

other catalytic processes utilizing a catalyst susceptible to sulfur poisoning.

An important advantage of the present in vention resides in the fact that nickel catalysts can now be utilized in the decomposition of sulfur-containing hydrocarbons by use of temperatures higher than those hitherto utilized in the decomposition of sulfur-free hydrocarbons under analogous conditions. As a result, it is now possible, without preliminary treatments of any kind, to crack sulfur-containing hydrocarbons in a one-step process and obtain cracking efiiciencies as high as those previously obtained in the cracking of sulfur-free hydrocarbons. 7

What I claim and desire to protect by Letters Patent is:

1. A one step process for catalytic cracking of sulfur polluted fluid hydrocarbons to produce high Weight yields of hydrogen and carbon oxides which comprises passing a mixture of steam and a fluid hydrocarbon containing at least 1 gr. of suliurper 100 cu. ft. of hydrocarbon in gaseous phase over a heated catalytic body containing at least 10% nickel, at least part of the catalytic body being maintained at a temperature of at least 900 C. 2. A one step process for catalytic cracking of sulfur polluted fluid hydrocarbons to produce high weight yields of hydrogen and carbon oxides which comprises passing a mixture of steam and a fluid hydrocarbon containing at least 1 gr. of sulfur per 100 cu. ft. of hydrocarbon in gaseous phase over an indirectly heated catalytic body containing at least 10% nickel at a space velocity of at least 300 volumes per hour per volume of catalyst, at least part of the catalytic body being maintained at a temperature of 900 C., and said mixture of steam and hydrocarbon having a steam to carbonratio of about 2 to about 4.5.

3. A one step process for catalytic cracking of sulfur polluted fluid hydrocarbons to produce high weight yields of hydrogen and carbon oxides which comprises passing a mixture of steam and a normally liquid petroleum hydrocarbon containing at least gr. of sulfur per 100 cu. ft. of vaporized hydrocarbon over an externally heated catalytic body containing at least 10% nickel, at least part of the catalytic body being maintained at a temperature of at least 900 C.

4. A one step process for catalytic cracking of sulfur polluted fluid hydrocarbons to produce high weight yields of hydrogen and carbon oxides which comprises passing a mixture of steam and a normally liquid petroleum hydrocarbon containing at least 100 gr. of sulfur per 100 cu. ft. of vaporized hydrocarbon over an externally heated catalytic body containing at least 10% nickel at a space velocity of at least 300 volumes per hour per volume of catalyst, at least part of the catalytic body being maintained at a temperature of 900 C., and said mixture of steam and hydrocarbon having a steam to carbon ratio of about 2 to about 4.5

JAMES H. SHAPLEIGH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 7 Name Date Re. 21,521 shapleigh July 30, 1940 1,128,804 Mittasch Feb. 16, 1915 1,713,325 Blake May 14, 1929 1,957,743 Wietzel et al. May 8, 1934 1,983,415 Strosacker et al. Dec. 4, 1934 2,135,058 Spicer et al. Nov. 1, 1938 2,218,495 Balcar Oct. 15, 1940 FOREIGN PATENTS Number Country Date 288,662 Great Britain Apr. 16, 1928 OTHER REFERENCES The Science .of Petroleum, vol. 2, pp. 1033 1040; 1938 ed. Oxford Univ. Press, New York.

Gas Engineers Handbook, pages 400, 986 (first ed., second impression). McGraw-Hill Book Co., Inc., New York.

Handbook of Physics and Chem, page 1348, 32d ed., Chemical Rubber Publishing Co., Cleve land, Ohio. i

I The Chemical Constituents of Petroleum by A. N. Sachanen, 1945 ed., pp. l3, 14, 27, 364, 365. Reinhold Publishing Corp., New York.- w

Chemical Engineers Handbook by Perry, second ed., pp. 2108-09, 2114. McGraw-Hill Book Co., New York. Chemistry of Petroleum Derivatives by Carlo ton Ellis,1937 ed., vol. 2, pp. 10 and 454. Reinhold Publishing Corp., New York. 7

Claims (1)

1. A ONE STEP PROCESS FOR CATALYTIC CRACKING OF SULFUR POLLUTED FLUID HYDROCARBONS TO PRODUCE HIGH WEIGHT YIELDS OF HYDROGEN AND CARBON OXIDES WHICH COMPRISES PASSING A MIXTURE OF STEAM AND A FLUID HYDROCARBON CONTAINING AT LEAST 1 GR. OF SULFUR PER 100 CU. FT. OF HYDROCARBON IN GASEOUS PHASE OVER A HEATED CATALYTIC BODY CONTAINING AT LEAST 10% NICKEL, AT LEAST PART OF THE CTALYTIC BODY BEING MAINTAINED AT A TEMPERTURE OF AT LEAST 900* C.