US2359759A - Purification and production of olefins - Google Patents

Description

Oct. 10, 1944. HEBBARD E AL 2,359,759

PURIFICATION AND PRODUCTION OF OLEFINES Filed April 22, 1939 IN VEN TORS e 47. #ebara Wzsonan 3Y2.

Patented Oct. 10, 1944 UNITED STATES PATETT OFFICE PURIFICATION A 1:::Il. tQD'U(J".'.I'.I(')N OF I v San Application April 22, 1939, Serial No. 269,503

19 Claims. ('01. 260-677) This invention concems an improved method for purifying olefins which are contaminated with acetylenic compounds. It refers particularly to the conversion of such acetylenic compounds into oleflns, whereby the yield and purity of the olefins are simultaneously improved. The present application is a continuation-in-part of our co-pending application Serial No. 174,667, filed November 15, 1937.

One of the usual methods for manufacturing olefins comprises passing a material, such as considerable molecular excess over the acetylenic natural gas, refiner" gas. kerosene, or other min-v eral oil fractions through .a zone heated sufficiently to decompose such material with formation of hydrogen and one or more unsaturated compounds. Pyrolyses of the type just men-' tioned have been carried out at temperatures ranging from about 500 C. to about 1200" C., but the yield of olefinic products per pass of the material through the pyrolyzin'g zoneis usually highest when operating at temperatures above 600 0., e. g., between 600 and 1000 C. The product obtained by the pyrolysis usually comprises not only the desired oleilnic products but also hydrogen; .saturated hydrocarbons such as methane, ethane, propane, etc.; di-oleflns such extracting the mixtures with various organic solvents such as acetone, ethyl acetate, etc., having the property of selectively absorbing the acetylenic compounds and leaving the olefinic products largely unabsorbed. Such mode of removing the acetylenes from thepyrolysis mixtures involves extra operating steps, utilization of a solvent for the extraction, and usually results in loss of a portion of the olefin product.

As hereinbefore stated, the cracked-gas mixture obtained by pyrolyzing mineral oil fractions or other aliphatic hydrocarbons at temperatures above 600 C. comprises not only gaseous oleflns but also hydrogen, acetylenic compounds, saturated hydrocarbons, and ,other gases. The hydrogen is usually present in an amount sufiicient to saturate a substantial proportion of the unsaturated hydrocarbons in the gas and is always in compounds.

We have discovered that be contacting such cracked-gas mixture with a hydrogenation catalyst under the operating conditions hereinafter described the acetylenic compounds are selectively hydrogenated to'form oleflns, thereby removing acetylenes from the mixture and increasing the .yield of oleflns. During'such operation the olefins present in the gas are not appreciably hydrogenated and the hydrogenation of the acetylenic compounds stops with the formation of olefins. We have further found that, although any active hydrogenation catalyst may satisfactorily be employed in such operation, certain new catalysts are particularly well adapted to use in the process. The invention, then, consists in the method and new catalysts hereinafter fully described and particularly pointed out in the claims.

The accompanyin drawing is a diagrammatic sketch of apparatus suitable for use in practicing the invention. In the drawing, the numeral I designates the outer shell of a hydrogenator which is provided at one end with a gas inlet 2 and at the other end with a gas outlet 3. The interior of the hydrogenator is divided into three compartments, viz., a reaction chamber 4 at one end of the same, a cooling compartment 5 in its center, and another reaction chamber 6 at 'the other end of the hydrogenator beyond said cooling chamber. In the reaction chambers E and 6 are located catalyst panels 7 and 8 which may be removed through the well openings 9 and Ill, re-

- by-products from such mixtures have comprised spectively. Each such catalyst panel is usually made bysupporti'ng a granular catalyst, or a catalyst deposited on a granular base such as pumice, broken brickware, etc., between two par-- allel metal screens, the latter, of course, being provided with suitable frame work to hold them and the granular catalytic material in place. On each side of the panels I and 8 are located temperature recording means,'such as thermometers or thermocouples, which are inserted into the wells it, Ma, Nb, and Me, respectively. The cooling chamber 5 is provided with the headers 5a and 5b and has passing through it the tubes H, which permit the .flow of gas from reaction chamber 4 to chamber 6. Cooling chamber 5 is provided with a cooling fluid inlet l2 and outlet i3. Any of the usual cooling fluids, e. g., water,

' steam, 'air, etc., may be used in chamber 5. The

metal parts of the hydrogenatormay be composed oi usual structural metals such as iron, steel, nickel, etc. Any solid hydrogenation catalyst, e. g.-, nickel, cobalt, platinum, etc.',- may be used in the process, although factors such as the activity of the catalyst and the thickness of each catalyst bed will determine to. a considerable extent the rate at which the gas mixture may be passed through the hydrogenator to obtain the benefits of the invention. Also, the new catalysts described at a point later herein possess good ac- I tivity and are exceptionally long' lived.

In employing apparatus such as that just described for the selective hydrogenation of the acetylenic compounds in a gas mixture containing the same and also olefins and hydrogen in excess over that required to convert the acetylenes into olefins, the operating conditions which require control are the temperature at which the hydrogenation is carried out, the rise in temperature .of the gas mixture which occurs during its passage through a given panel or bed of catalyst, and the rate at which the gas mixture is passed through the catalyst. Of'these three variable operating conditions, the rise in temperature of the gas during passage through the catalyst is most critical, but fortunately this temperature rise is directly dependent upon the rate of gas passage and may be varied by changing the rate of flow.

When using any solid catalyst for the hydrogenation, the operating conditions to be observed are:

(1) The temperature of the gas mixture during contact with the catalyst should be suflicient to cause reaction but not above 450 C., since at higher temperatures the olefins as well as the acetylenes become hydrogenated and this secondary reaction, once started, usually causes overheating with resultant carbonization and frequent plugging of the apparatus. Temperatures of from 80 to 450 C. have successfully been employed and temperatures between 125 and 225 C. are generally most satisfactory.

(2) 'The rise in temperature of the gas during passage through a catalyst bed should not exceed 300 C. and preferably does not exceed 275' C. If a greater temperature rise is permitted, over-hydrogenation with formation of paraffins and carbonization are liable to occur.

(3) The rate of gas flow should'be controlled so that the difference between the temperature of the gas entering a catalyst bed and that leaving the bed does not exceed 300 C. When necessary, this temperature differencemay be decreased by increasing the rate of gas flow.

Since the temperature r se which occurs during passage of the gas mixture through a catalyst bed is due to heat liberated by hydrogenation of the acetylenic compounds, the temperature rise is dependent upon the concentration of acetylenes in the gas treated, upon the heat lost by radiation or conductance, and upon the quantity of acetylenic compound reacted during passage ofthe gas through the panel. Stated in simpler. though less exact, terms. the rise in temperature of the gas during passage through a catalyst bed is approximately proportional to the decrease in concentration of acetylenic compounds in the gas which occurs during such passage. Usually a 1 per cent by volume reduction of acetylene in such gas, brou ht about by hydrogenation in a catalyst bed. raises the temperature of the gas by between 48 and 56 C. Accordingly, in order to avoid a temperature rise of more than 300 C., the acetylene concentration of the gas should be reduced bynot more than 6 per cent. and preferably not more than per cent. during passage through a given panel or bed of catalyst.

It will thus be seen that in treating a gas mixture containing less than 5 per cent by volume of acetylenic compounds a single bed of catalyst can be used to convert substantially all of such compounds into olefins,'but that when the gas to be treated contains acetylenic compounds in higher concentration a plurality of catalyst panels must be usedand not more than. about 5 per cent reduction in, the acetylenic content of the gas should be permitted to -occur in any single panel of catalyst. In practice, it is preferable to employ a hydrogenator containing two or more panelsof catalyst, with cooling means located between the panels, in treating any gas mixture containing more than 2 per cent of acetylenic compounds, since the use of a multi-panel reactor permits better temperature control with resultant increase in the life of the catalyst than is obtained when using only a single panel or bed of catalyst.

In manufacturing olefins in accordance with the invention natural gas, refinery gas, kerosene, or other mineral oil fractions or any substance rich in saturated aliphatic hydrocarbons may be employed as the starting material. Also, higher olefins, such as amylene, hexene, octylene, etc., may be used to produce lower olefins, such as ethylene, propylene, etc. Any such starting material, alone or admixed with diluents such as steam, carbon dioxide, etc., is pyrolyzed at temperatures above 600 C. in the presence or absence of dehydrogenation catalysts in accordance with any of the usual modes of pyrolyzing aliphatic hydrocarbons to obtain a vapor mixture comprising one or more olefins, hydrogen, and one or more acetylenic compounds. Other products, such as saturated hydrocarbons, di-oleflns, etc., may also be present in the pyrolyzed mixture. The pyrolyzed vapor mixture may be cooled somewhat and passed over the hydrogenation catalyst, as hereinbefore explained, to effect the desired hydrogenation of the acetylenic compounds present.

However, such pyrolysis mixture frequently contains di-olefins, e. g., butadiene, which tend to polymerize or decompose and coat the catalyst during the hydrogenation, thereby shortening the active life of the catalyst. In practice, such diolefins, are preferably removed before carrying out the hydrogenation. This may be accomplished in any of several ways, eg., the pyrolysis mixture may be cooled and treated with a condensation catalyst, such as aqueous sulphuric acid, of activity sufficient to polymerize and condense the di-olefins without appreciably affecting the other unsaturated compounds present, or the mixture may be scrubbed with a solvent such as light mineral oil having the property of selectively absorbing di-olefins and other higher hytaining 4 or more carbon atoms, but not the ethylene or propylene present, to form liquid polychlorinated hydrocarbons. The vapor mixture remaining after any such treatment contains tional oleflns. As hereinbefore pointed out. such temperature is usually between 125 and 250 0.,

and it is essential that neither the catalyst nor the gas in contact therewith be'permitted to become heated to temperatures above 450 C. The gas mixture is passed through the catalyst bed at such rate that the temperature of the gas leaving the bed does not exceed that of the gas entering the bed by more than 300 C. when the gas subjected to the hydrogenation initially contains more than per centby volume of acetylenic compounds, it 'is, as hereinbefore explained, necessary to contact it with a series of catalyst panels or beds, the gas being cooled during passage from one such panel or bed to the next so that it never becomes heated to a temperature exceeding 450 C.

The hydrogenation is usually carried out at atmospheric pressure or slightly above, but it may be carried out under considerably higher pressures. e. g., 50-200 pounds per square inch gauge. In most instances we prefer to operate at pressures below 50 pounds per square inch gauge since the reaction is most readily controlled at such moderate pressures.

The vapor mixture issuing from the hydrogenation chamber is relatively free of acetylenic compounds and is considerably richer in olefins than before contact with the catalyst. The treated mixture may be employed directly in most reactions for the preparation of olefin derivatives, such as alcohols,'alkyl halides, olefin halides, etc.

As hereinbefore stated, any active hydrogenation catalyst, such as platinum, cobalt, reduced nickel, etc., may be employed to promote the reaction between hydrogen and the acetylenic byproducts, but certain catalysts possess a greater catalytic life than others and display less tendency to cause overheating when-employed in the reaction. In practice, we prefer to use reduced nickel or catalysts comprising reduced nickel-in the process and we have found that certain compound catalysts comprising reduced nickel and other metals are more useful than reduced nickel itself for the purpose. by heating nickel nitrate to a temperature at which it is decomposed with formation of the oxide and subsequently or simultaneously hydro-' genating the latter is very active, but tends to Reduced nickel prepared assures tively, but theymay be carried out in a single step by heating the nitrates in a current of hydrogen to a temperature at which they are decomposed. I

A mixture of between 0.05 and 0.25 gram atom of copper. per gram atom of .nickel is substantially as active in the process as nickel itself, but

. is less easily poisoned than nickel. Such catalyst is prepared by heating a mixture of the metal nitrates to form the corresponding oxides and reducing the latter at temperatures between 275 and 325 C. under a hydrogen pressure between 100 and 200 pounds per square inch. If desired, this reduction may be carried out at amospheric pressure and at temperatures between 300 and A mixtureof about 0.1 gram atom of copper, 0.25 gram atom of iron, and 1 gram atom of nickel is substantially equivalent in activity to the iron-nickel catalyst mentioned above. Such catalyst is made by heating the necessary metal nitrates to form a mixture of the corresponding oxides and reducing the latter with hydrogen. at atmospheric pressure and a temperature between 350 and 375 C.

Mixed catalysts comprising nickel, zinc, and iron, or nickel and cobalt, are also less sensitive than nickel itself toward poisoning during the hydrogenation. Such catalysts are prepared from a mixture of the corresponding metal nitrates by procedure similar to that mentioned above.

The hydrogenation catalyst ,may be used in pure finely divided form but is preferably used on a support such as pumice, alumina, silica gel, carborundum, coke, etc. In practice, we find coal-coke to be satisfactory and most economical as a support for the catalyst. The supported catalyst is prepared by treating the sup-. porting material, e. g., coal-coke, with a solution or melt of the necessary metal nitrates, heating the resultant mixture to generate the metal oxides on the supporting material and reducing the metal oxides to obtain the metals on and/or in the supporting material. As hereinbefore stated, the operations of decomposing the nitrates to oxides and reducing the latter are preferably carried out consecutively but may cause overheating during use in the hydrogenaj tion. Accordingly, careful control is required in using reduced nickel itself as the catalyst.

atom of nickel displays less tendency to'cause overheating during the hydrogenation and is less susceptible to becoming poisoned, i. e., deactivated, than reduced nickel alone. This catalyst may be prepared by heating a mixture of iron and nickel nitrates to form a mixture of'the corresponding oxides andreducing the latter with,

hydrogen at temperatures between 375 and 425 C. under a hydrogen pressure of between 100 and 200 pounds per square inch gauge. Such cperations are preferably carried out consecube performed simultaneously. The supported catalyst is employed in granular form, prefer-' ably of size capable of passing a four mesh, but

not a three mesh, screen.

The following examples illustrate certain ways in which the principle of the invention has been applied but arefnot to be construed as limiting the invention.

' Example 1 eral oil in accordance with known procedure to remove hydrocarbons containing more than 3 ear bon atoms therefrom. The remaining gas contained 39.6 per cent by volume of ethylene, about 20 per cent of hydrogen, 12 per cent'of methane, about 7 per cent of propylene, 3 per cent of acetylene and traces of other gases. This gas mixture was passed at approximately atmospheric pressure and at space velocities varying from 6.6

to 47 cubic feet of gas percubic foot of catalyst per minute through a bed of a granular hydrogenation catalyst maintained at temperatures which increased gradually from 150 to 250 C. during the run. The catalyst employed in this experiment was one prepared by soaking granular pumice in a concentrated nickel nitrate solution, drying the treated pumice at about 100 0., whereby the nickel nitrate was deposited on and in the pumice, and thereafter simultaneously decomposing the nitrate to the oxide and reducing the latter by passing hydrogen over the treated pumice while maintaining the latter at a temperature between 300 and 350 C. The gaseous mixture issuing from the catalyst bed during the above-described employment of the catalyst contained 43.2 per cent by volume of ethylene, 8 per cent of propylene, and only 0.5 per cent of acetylene.

sam le 2' A cracked-oil gas fraction containing-42.4 per cent by volume of ethylene, 22 per cent of hydrogen, 16.2 per cent of methane and other saturated hydrocarbons, 9.5 per cent of propylene, 4 per cent of nitrogen and oxygen, 3.7 per cent of compounds present in the mixture. It may also be applied where an aliphatic hydrocarbon is pyrolyzed at very high temperatures, e. g., in an electric arc, to form acetylene as the principal product. The resultant pyrolysis mixture may be scrubbed with a suitable solvent to extract selectively most of the acetylene leaving a vapor mixacetylene, 1.2 per cent of higheracetylenic compounds (apparently allylene for the most part), and l per cent of carbon dioxide and hydrogen sulphide was reacted to convert the acetylenic compounds into olefins, using a reactor similar It will be noted that the cracked-oil gas employed in this experiment contained a total of 4.9 per cent of acetylenic compounds. This gas was preheated and passed at a space velocity-of 100 through the reactor. By space velocity is meant the ratio of the volume of gas per minute (expressed as cubic feet of gas at 0 C. and atmospheric pressure) per cubic foot of granular catalytic material in the reactor. During passage of the gas through the reactor measurements were taken of the temperature of the gas just before entering each catalyst panel and of the temperature in the center of each panel. The gas was, of course, cooled during passage from one panel to the next. Also, samples of the gas leaving each panel were withdrawn and analyzed to determine their content of acetylenic compounds in per cent by volume. Thevalues obtained are given in the following table.

The gas leaving the reactor was analyzed and found to contain, on a volume basis: ethylene, 48.2 per cent; hydrogen, 18.1 per cent; saturated hydrocarbons, 17.1 per cent;. propylene, 11.2 per cent; nitrogen and oxygen, 4.2 per cent; carbon hire comprising hydrogen, olefins and a minor proportion of acetylene. This residual vapor mixture may be contacted with a hydrogenation catalyst under the reaction conditions hereinbefore specified to convert the remaining acetylene into an olefin, e. g., ethylene, thereby increasing the yield of olefin.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regards the method or ingredients herein disclosed, provided the steps or ingredients stated in any of the following claims or the equivalent of such stated steps oringredlents be employed.

We therefore particularly point outand distinctly claim as our invention:

1. Ina method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene and more than one mole of hydrogen per mole of the acetylene, through a bed of a durable hydrogenation catalyst at a reaction temperature sufiicient to cause hydrogenation of the acetylene :butbelow 450 C. and at a rate of gas flow suflicient to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst (bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased.

v 2. In a, method for producing ethylene, the step of passing a gaseous mixture comprising ethylene as its major ingredient and also containing acetylene, and more than one mole of hydrogen per mole of acetylene, through a bed of a durable hydrogenation catalyst at a reaction temperature suiilcient to cause hydrogenation of the acetylene but below 450 C. and at a-rate of gas fiow sufficient to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form ethylene and the ethylene content of the gas is increased.

3. In a method for producing -olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene, and more than one mole of hydrogen per mole of the acetylene, at a reaction temperature sumcient to cause hydrogenation of the acetylene but below 450 C. through a series of beds of durable hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bed to another such bed, the rate of gas flow beingsufficient to prevent a more than 300 0. rise in temperature of whereby the acetylene is hydrogenated to form an olefin and the olefin content or the gas is increased. a

4.. In a method for producing ethylene, the

genation oi. the acetylene but below 450 C. and

step oi passing a cracked-oil gas fraction comprising ethylene as its maioringredlent and also containing acetylene, and more than one mole oi hydrogen per mole of the acetylene, at a reaction a temperature sufiicient to'cause hydrogenation of the acetylene but below 450 C. through a series of beds of durable hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bed to another such bed, the rate oi -gas flow being sumcient to prevent a more than 300 C.rise in temperature of the gas during passage through any catalyst bed, whereby acetylene is hydrogenated to form ethylene and the ethylene content of the gas is increased.

5. In a method for producing olefins, the steps of pyrolyzing an aliphatic hydrocarbon at'a tem-' perature above 600 C. to obtain a gaseous mixture comprising hydrogen, olefins and acetylene, and containing the olefins as the major ingreat a rate of gas fiow sufilcient to prevent a more than 300 C. rise in the'temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased.

9. In a method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene and more than one mole 'of hydrogen per mole of the acetylene,

through a bed of a granularsupported hydrogenation catalyst comprising nickel and iron, each finely divided, at a reaction temperature sufiicient to cause hydrogenation oi the .acetylene but below 450 C. and at arate of gas flow sufii cient to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased.

dients or the gaseous mixtures andpassing the gas through a bed of .a durable hydrogenation catalyst at a reaction temperature sufiicient to cause hydrogenation of the acetylene but below 450 C, and at a rate of gas flow sumcient'to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form ethylene and the olefin content of the gas isincreased.

6. In a method for producing olefins, the steps of pyrolyzing an aliphatic hydrocarbon at a temperature above 600 C. to produce a gaseous mix- -ture comprising hydrogen, olefins, and acetylenes,

and containing the olefins as the major ingre dients of the gaseous mixtures removing any diolefin present in the gas, and thereafter passin the gas at a reaction temperature sumcient to cause hydrogenation of the acetylenes but below 450 0. through a series of beds of hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bed to another such bad, the rate of gas flow. being sufilclent to prevent a more than 300 C. rise in temperature ofthe gas during passage through any catalyst bed, whereby the acetylene is hydrogenated 'to form an olefin and the olefin content oi the gas is increased.

7. In a method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene and more than'one mole of hydrogen per mole of the acetylene, through a bed of a granular durable hydrogenatlon catalyst containing nickel as an essential ingredient at a reaction temperature suiiicient to cause hydrogenation of the acetylene but below 450 C. and at a rate of gas flow sufflcient to prevent a more than 300 0. rise in the temperature of the gas during its passage through the catalyst bed,whereby the acetylene is hydrogenated to form an olefin and the olefin content of the as is increased.

8. In a method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene and more than one mole of hydrogen per mole of the acetylene, through a bed of a granular supported hydro genation catalyst, containing finely divided ,nckel and a finely. divided catalytic metal of the class consisting of iron, copper, zinc, and cobalt, at a reaction temperature suificient to cause hydro- 10. In a method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its major ingredient at least one olefin and also containing an acetylene and more than one mole of hydrogen per, mole of the acetylene,

through a bed of. a granular supported hydrofiow sumcient to prevent a more than 300 C genation catalyst containing nickel and copper, each in finely divided form, at a reaction temperature sufilcient to cause hydrogenation of the acetylene but below 450 C. and at a rate of gas rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased.

11. In a method for producing olefins, the step of passing a cracked-oil gas mixture comprising as its majoringredient at least one olefin and also containing an acetylene and more than one mole of hydrogen per mol of the acetylene,

through a bed of a granular supported hydrogenation catalyst containing nickel, copper, and iron,

each "in finely divided form, at a reaction temalso containing-more than 5Iper cent by volume of at least one acetylenic hydrocarbon and more than one mole of hydrogen permol of the acetylene, through a bed of a durable hydrogenation catalyst at aireaction temperature sufiicient to cause hydrogenation oi the acetylene but below 450 C. and at a rate of gas fiow sufiicient to prevent a more than-300 0. rise in the temperature of the gas during its passage throughthe catalyst bed, whereby the acetylene is hydrogenated to form'an olefin and as is; increased.

18. n1 -a .method f r the olefin content of the producing ethylene, the

step oi passing a gaseous mixture, comprising.

ethyleneas its 1 na.1or ingredient and alsfocontaining more than 5 per {cent by "volume of acetyiene and more than one mol of hydrogen "per mole of acetylene, throughfa "bed oia durable hydrogenation catalyst at a re'ar'ition 'tempe'ra ture sufilcient to cause hydrogenation of the acetylene but below 450 C. and at a rate of gas fiow sufilcient to prevent a more than 300 C. rise in the temperature orvthe gas during its passage through the catalyst; bed, whereby the acetylene is hydrogenated to form ethylene and the ethylene content of the gas is increased.

14. In a method for producing olefins, the step of passing a cracked-oil gas mixture, comprising as its major ingredient at least one olefin and also containing more than per cent by volume of an acetylene andmore than one mole of hydrogen per mole of the acetylene, at a reaction temperature sufiicient to cause hydrogenation of theacetylene but below 450 C. through a a series of beds of durable hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bedto another such bed, the rate of gas fiow being sufiicient to prevent a more than 300 C. rise in temperature of the gas during passage through any catalyst bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased.

15. In a method for producing ethylene, the step of passing a cracked-oil gas fraction, comprising ethylene as its major ingredient and also containing more than 5 per cent by volume of acetylene and more than one mole of hydrogen per mole of the acetylene, at a reaction temperature sufiicient to cause hydrogenation of the acetylene but below 450 0. through a series of beds of durable hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bed to another such bed, the rate of gas fiow being sufilcient to'prevent a more than 300 C. rise in temperature of the gas during passage through any catalyst bed, whereby acetylene is hydrogenated to form ethylene and the ethylene content of the gas is increased.

16. In a method for producing oleflns, the step of pyrolyzing an olefinic hydrocarbon at'a temperature above 600 C. to produce a gaseous mixture comprising as its major ingredient at least one olefin and also containing more than 5 per cent by volume of acetylenic hydrocarbons and hydrogen in amount exceeding the molecular equivalent of the acetylenes, removing any diolefin present in the gas,- and thereafter passing the gas at a reaction temperature sufiicie'nt to cause hydrogenation of the acetylenes but below 450 0. through a series of beds of hydrogenation catalyst with intermediate cooling of the gas during passage from one catalyst bed to another such bed, the rate of gas flow being of passing a cracked-oil gas mixture. comprising as its major ingredient at least one olefin and also containing more than 5 per cent by volume of an acetylene and more than one mole of hydrogen per mole of the acetylene, through a bed of a granular supported hydrogenation catalyst,

containing finely divided nickel and a finely divided catalytic metal of the class consisting of iron, copper. zinc, and cobalt, at a reaction temperature below 450 C. and at a rate of gas fiow sufilcient to prevent a more than 300 0. rise in the temperature bf the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an olefin and. the olefin content of the gas is increased.

18. In a method for producing oleflns, the step of passing a cracked-oil gas mixture, comprising as its major ingredient-rat least one olefin and also containing more than 5 per cent by volume of an acetylene and more than one mole of hydrogen per mole of the acetylene, through a bed of a granular supported hydrogenation catalyst comprising nickel and iron, each finely divided, at a reaction temperature suflicient to cause bydrogenation of the acetylene but below 450 C. and at a rate of gas fiow sufiicient to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an olefin and the olefin content of the gas is increased. A

19. In a method for producing oleflns, the step of passing a cracked-oil gas fraction, comprising as its major ingredient at least one olefin and also containing more than 5 per cent by volume of an acetylene and more than one mole of hydrogen per mole of the acetylene, through a bed of a granular supported hydrogenation catalyst containing nickel and copper, each in finely divided form, at a reaction temperature sufilcient to cause hydrogenation of'the acetylene but below 450 C. and at a rate of gas fiow sufilcient to prevent a more than 300 C. rise in the temperature of the gas during its passage through the catalyst bed, whereby the acetylene is hydrogenated to form an-olefin and the olefin content of the gas is increased.

GEORGE M. HEBBARD. WILSON HUNT.

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