US2388099A - Manufacture of butylenes - Google Patents

Description

Oct. 30, 1945. c. K. vlLAND ETAL MANUFACTURE OF BUTYLENES Y Filed Jan. 14, 1945 0 N A Vr WMH y www /u L EH IKM MH y o e v. N k KIPAIHR Puoxt UQTMU .n Uzkzwmc( m,

Patentel0ct30,l945

UNITED sTATEs PATENT OFFICE MANUFACTUBE OFBU'I'YLENES Clare Kenneth Vliand. Martinet, and Herschel Y. Hyde, Associated, Calif., assignors to '11de Water Associated i! Company, San Francisco Calif., a corporation of Delaware Application January 14, 1943, Serial No. 472,412

9 Claims. (Cl. 260-685) This invention relates to the manufacture of olenic feed stock for alirylation and similar processes where a high concentration of butylenes is desirable and has for a principal object the manufacture of a C4 fraction containing unusually high percentages of oleflnic hydrocarbons.

Another object of the invention is to provide materials peculiarly adapted' for pyrolytic conversion into butylenes.

A further object is to reduce the quantity of normal butane commonly present in stocks charged to alkylation or similar processes thereby increasing the plant capacity by elimination of a large proportion of those hydrocarbons not entering into the reaction.

Other objects will be apparent from the following description.

In the manufacture of modern aviation gasoline the alkylation process has become one of the most commonly used methods of obtaining gasoline fractions of high anti-knock rating. As is well known, this process comprises the formation of branch-chain paratiins chleily in the boiling range of the octanes by the chemical combination of isobutane with butylenes.

The quantity of alkylate which may be produced in any given area, therefore, is limited by the available supply of isobutane and butylenes as well as by the capacity of the alkylation plan. APresent demands for aviation gasoline have resulted in the consumption of practically the entire supply of naturally occurring isobutane and nu- `merolus refiners have undertaken the installation of isomerisation processes to augment the supply thereof. The chief source, if not the entire supply. of butylenes is obtained as by-products from pyrolytic processes, such as cracking and polymerization, which are primarily designed for the manufacture oi' hydrocarbons within the gasoline boiling range. Due to modern demands for butylenes for alkylatlon purposes numerous pyrolytic plants are being operated principally for their butylene production.

As commonly practiced. the butylenes for the alkylation process are obtained by isolating a C4 cut from the products of the pyroiytic cracking and/or polymerization processes. Ordinarily this C4 cut will contain from about 25% to 45% of butylenes, the remainder being chieily normal butano. As the normal butane cannot be readily fractionated from the butylenes without the use of extensive fractionatlng equipment. it is common practice to charge the entire C4 cut to the slhlation process. along with the required amcimts' of lscbutane. As the normal butano does not enter into the alkylation reaction, it passestbroughtheplantunchanged andisfracuomtes from the produca ai the reaction. This procedure offers dilcultles, however. when northe throughput capacity of the alkylation reactor is reduced in proportion to the amount of the inert normal butano which is present. Second. in order to separate the normal butane from the products. a heavy load is placed on the fractionating equipment of the alhlation plant. Third, since the alkylation process requires the recirculation of large amounts of isobutane for the properiunctioning of the process, the separation therefrom of the inert normal butane always results in the loss of substantial quantities of valuable isobutane into the normal butane due to imperfect fractionation. From the above it is seen that it is desirable to charge to the alkylation process a Ci cut with as iowa content of normal butane as possible.

The present invention provides a means whereby there can be obtained from a pyroivtlc process a C4 cut containing in the order of 60% to 80% of butylenes, the remaining 40% to 20% being composed of nearly equal quantities of isobutane and normal butano. By the use of such a C4 cut the above dimcultles are greatly alleviated and the capacity of a conventional alkylatlon plant is thereby greatly increased. As the isobutane enters the allwlation reaction, the quantity of unreactive material (normal butaiie) is thus reduced to a minimum.

Brieily described the invention comprises subjecting normal pentane to pyrlytlc decomposition in the presence of substantial amounts of Cs and Ca hydrocarbons. When normal pentane Vis subjected to temperatures in the range of 1000 F. to 1300 F., it is decomposed into various oleilnlc and paraiilnic hydrocarbons as a result of several more or less simultaneously occurring reactions of which the following appear to pre' dominate:

' ln accordance with the invention substantial quantities of propane, propylene, ethane, and/or ethylene are mixed with the normal pentane prior to carrying out the decomposition. The presence of the Cn and especially the C: hydrocarbons tends to suppress reactions (l) and (2) and thereby increases the amount of material undergoing reaction (3), resulting in the formation of a large amount of butylenes.

Under the temperature conditions of the reaction, and especially in the temperature range of i050 F. to ll'., there occur, simultaneously with the decomposition of the normal pentane, poLvmerizing reactions among the C: and C: hydrocarbons present resulting in the formation of additional quantities of butylene together with a. large quantity of polymer gasoline of good antimai butano is present in large amounts. First ,9 knock value. 'Isobutana nonnal butano, and, in

minor proportions, polymer tars and other products are also formed. As stated above, the isobutane is a valuable constituent for the feed stock to the alkylation plant, while the normal butane is formed in a much lower proportion than in conventional pyrolytic processes.

While the presence of any amount of C: and Ca hydrocarbons will suppress reactions (l) and (2) above to some extent, the eil'ect increases with the amount of C: and C: hydrocarbons present. In order to obtain a substantial predominance of reaction (3) the C: and Ch hydrocarbons should be present at least in equimolar proportion to the normal pentane, although a greater amount is to be preferred and a ratio of Cz and C3 hydrocarbons to normal pentane of 3:1 or greater is desired. Excellent results have been obtained using o, molal ratio of about 7:1. In the C: and Ca hydrocarbons charged as above. a ratio of 20% Cz and 80% C; hydrocarbons has been found to give good results.

In carrying out the process of the invention it may be convenient to use a conventional thermal polymerization plant. The accompanying drawing shows diagrammatically a typical thermal polymerization plant with modlcations for carrying out the invention. In accordance with the invention normal pentane in line I and Cz and Cs hydrocarbons in line 2 are charged to pyrolytic zone 6 through line l; the proportion of each being controlled by valves l and l. In pyrolytic zone the mixture is heated to the reaction temperature in coils 1 and l and the resulting products leave through line 9. Suitable pressure is maintained upon the mixture in the pyrolytic zone by means of valve I0. From line B the products enter fractionating zone H (which may advantageously comprise several fractionating columns arranged in accordance with well known principles of fractional distillation) wherein they are fractlonally distilled to recover desired fractions, shown diagrammatically as leaving through lines I2, II, Il, IB. and II in the respective order of their boiling ranges. Through line Ill is withdrawn methane, and any hydrogen, formed during the reaction and sumcient ethane and ethylene to maintain the concentration of C: fractions withdrawn through line I3 within the desired range. This fraction may be used as fuel. The remaining Cz hydrocarbons together with the C: hydrocarbons are withdrawn through line I3 and recycled to the process through lines l1 and I0, being mixed with incoming fresh charge of C: and C: hydrocarbons in line 2 or l. Through line il is withdrawn the desired C4 cut which under the operating conditions of the invention will contain from 60% to 80% of oleiins. As previously stated, this C4 cut may advantageously be used as olenic feed for an alkylation process. Through line l5 is withdrawn a debutanized polymer gasoline while polymer tars leave the fractionating zone through line il. If desired, normal pentane may be fractionated from the polymer gasoline in a second fractionating zone (not shown) and recycled to the process (through lines not shown) to be mixed with the fresh normal pentane in line l or I.

Normal pentane for conducting the process of the invention is readily available in most refineries manufacturing aviation gasoline, being obtained as a. by-product of relatively low value in the fractionation of straight run gasoline stocks. and other stocks, for the production of isopentane used as an ingredient in aviation gasoline. As is well known, the normal pentane thus obtained is generally not of 100% purity. Modern fractionating equipment, carefully operated, is capable of producing normal pentane of or higher purity. With less eilicient equipment, or with overloaded emcient equipment, the purity of the normal pentane lay-product may be reduced to as low as 75%, the chief impurity being isopentane.

While, for overall refinery eiliciency, it is desirable to separate normal pentane oi' as high Purity as possible, the process of the invention is adapted to operate satisfactorily on normal pentane stocks within the above range of purity. In the appended claims this range of purity is intended to come within the scope of the term consisting essentially of normal pentane.

Following is an example of the process of the invention conducted in a conventional thermal polymerization plant. A fresh charge consisting of V612 barrels per day of propylene. 237 barrels per day of propane, and 1046 barrels per day of normal pentane stock, together with 3800 barrels per day of recycled C: hydrocarbons and i162 barrels per day of recycled Cn hydrocarbons, was charged to the heating coil of the polymerlzing plant wherein the temperature was raised to 1125 F. The products from the heating coil were passed to the reaction section wherein the temperature was reduced to 1050' F. over a period of about 12 minutes. The products were then fractionally distilled into a gas fraction, a recycle fraction consisting of all the C: hydrocarbons together with a portion of the Cz hydrocarbons formed, a C4 cut containing all the C4 hydrocarbons formed. a debutanized polymer gasoline fraction, and a residual tar fraction. It was found that the C4 fraction contained '70% of oleilns. The following table shows results obtained compared to conventional operations where C: hydrocarbons are pclymerized under similar operating conditions:

Fresh charge (bbl-lday):

Propylene es y R C. hydrocarbons C: hy

Analysis of N pentane stock, pement:

lso-pentane N- tano lso ennepins Yields (bbl. day):

Isobutane Butylenes N-butnne Total Cl traction Other products Total Analysis oi' C4 fraction, (percent): Isobutnna From the above table it is seen that, by introducing normal pentane into the charging stock of the polymerization plant in accordance with the invention, the yield of C4 hydrocarbons is greatly increased together with a substantial over- :,ssaooo allloweringoi'thepercentageoinormalbutane therein.

Although a conventional thermal polymeriaation plant using normal operating conditions of time. temperature, and pressure is well adapted to the carrying out of the invention and although such operation is a preferred form of the invartion,theinventionlnabroadersenseisnot limited to such operation. any equipment mur beusedwhichiscapableofmaintaining themixture of normal pentane and (I: and C: hydrocarbons at a cracking temperature for suiilcient time that the desired amount of butylenes is `iorxned and various apparatus may suggest themselves to a skilled engineer.

Conventional polymerization furnaces are generally divided into two sections: the tubes or coils of the rst section being subiectcd to a higher degree of heat than those of the second section. The process of the invention may be carried out in a single coil subjected to the necessary temperature. or a combination of heating coil and reaction chamber may be used if so desired.

Pressures employed in conventional polymerization plants are usually in the order of 300 to 500 lbs. per sq. inch at the outlet transfer line. While this pressure is preferable, for operating reasons, in the practice of the invention. other pressures may be used from atmospheric. or below, to one hundred or more atlnosphcres.

fractionation is, in practically all cases, carried out in a series oi' fractionating columns under pressures suilicient to properly condense the necessary products and reiiuxes at the temperatures employed. The conditions of operation and design of such fractionating towers is well known to distillation engineers.

Likewise, the charge to the conventional polymerization plant (including both the feed and recycle stocks) is generally in the liquid phase. This is, however, merely an expedient and the charge oi normal pentane and C: and C: hydrocarbons according to the invention may be either in the liquid or vapor phase as desired. Obviously, at the cracking temperatures involved. the materials undergoing the reactions will be above the critical temperature. and, consequently, in the vapor phase.

We claim:

l. The process of producing a mixture or C4 hydrocarbons containing a high proportion of butylenes, which comprises: subjecting a hydrocarbon fraction consisting essentially of normal pentane to a temperature in the range of i000" F. to 1300 F. while in the presence of added amounts oi hydrocarbons from the group consisting oi' ethane. ethylene. propane. and propylene and in the substantial absence of other added hydrocarbons; fractionally distilling the resulting products and separating therefrom a mixture of C4 hydrocarbons: the molal ratio of normal pentane to C: and C: hydrocarbons subjected to the reaction being between about 1:1 and about 1:7.

2. The process according to claim 1 wherein the molal ratio of normal pentane to Cz and C: hydrocarbons subiected to the reaction is not greater than 1:3.

3. Ihe process according to claim 1 wherein the molal ratio ot normal pentane to C: and C: hydrocarbons subjected to the reaction is about 1:7.

4. The process ci producing amixture of C4 hydrocarbons containing a high proportion oi' butylenes, which comprises: subjecting a hydrocarbon traction consisting essentially of normal pentane to a temperature in the range ot about 1050 F.

toabmxtlloltwhlleinthepnseuoeoiadded amounts ci from the lmnp cmsisting ot ethane, ethylene. propane. and propyiene andinthesubstantialabsenceoiotheradded hydrocarbons: iractionaiiy distilling the resulting products; and separating therefrom a mix- -tureof Cshydrocarbons: the molalratio otnormal pentane to Cs and C: hydrocarbons subiected tovthe reaction being between about 1:1 and about 1:

LThepx-ocessofproducingamixtureoi'cahydrocarbons containing a high proportion of butylenes, which comprises: nowing a stream of hydrocarbons consisting essentially oi' normal pentane through a conduit, simultaneously bowing a stream of hydrocarbons from the group consisting o! ethane. ethylene, propane. and propylene through said conduit in admixture with said normal pentane while in the substantial absence of other added hydrocarbons. heating the mixture in said conduit to a temperature between i000 ll'. and 1300 F., maintaining the mixture at said temperature for suilicient time that a Portion of the normal pentane is cracked forming butylenes. reducing the temperature of the resulting products. fractionalLv distiliing the resulting products and separating therefrom a fraction composed mainly of the C4 hydrocarbons present in said products; the molal ratio o! normal pentane to Cz and C: hydrocarbons subjected to the reaction being between about 1:1 and about 1:7.

6. The process of producing a mixture of C4 hydrocarbons containing a high proportion oi' butylenea, which comprises: flowing a stream oi hydrocarbons consisting essentially of normal pentane through a conduit, simultaneously ilowing a stream o! hydrocarbons from the group consisting of ethane. ethylene, propane. and prvwlene through said conduit in admixture with said normal pentane while in the substantial absence oi other added hydrocarbons, heating the mixture in said conduit to a temperature between i000 F. and 1300 F., maintaining the mixture at said temperature for sutiicient time that a portion of the normal pentane is cracked forming butylenes,

reducing the temperature of the resulting products, fractionally distilling the resulting products to separate therefrom a fraction composed mainly of the C4 hydrocarbons present in said products and a recycle fraction composed mainly of C: and C: hydrocarbons, and returning at least a Portion oi' said recycle traction to the process to Join said stream of C: and C: hydrocarbons: the moial ratio of normal pentane to C: and C: hydrocarbons subjected to the reaction being between about 1:1 and about 1:7.

'1. The process of producing a mixture of Cl hydrocarbons containing a high proportion of butylenes, which comprises: iiowing a stream of hydrocarbons consisting essentialw oi' normal pentane through a conduit, simultaneously flowing a stream oi hydrocarbons from the group consisting of ethanc, ethylene, propane, and propylene through said conduit in admixture with said normal pentane while in the substantial absence of other added hydrocarbons, heating the mixture in said conduit to a temperature between i!` F. and 1300l F., maintaining the mixture at said temperature ior sumcient time that a portion of the normal pentane is cracked forming butylenes, reducing the temperature oi the resulting products, iractionally distllling the resulting products to separate therefrom a fraction composed mainly of the C4 hydrocarbons present in said products and a recycle fraction composed mainly of unre- 4 aandoen acted normal pentane. and returning at least a 9. A process of producing drocarbong portion of said recycle fraction to the process to which comprises: heating normci lntane to a. loin said nrst mentioned stream: the molal ratio cracking temperature in the order ci' 1000 F. to of normal pentane to Ca and C: hydrocarbons 1300 F. while in the presence of an added quan# subjected to the reaction being between about 1:1 5 tity of C: and Ce hydrocarbons and 1n the suband about 1 :7. stantial absence oi' other added hydrocarbons. and

8. A method comprising thermally cracking at maintaining such temperature for a period of time a temperature in the order of 1000 F. to 1300 F. sumcient to form a C4 traction containing in the a mixture ot normal pentane, C: hydrocarbons order ot from 60% to 80% of olens; the molal and C: hydrocarbons while in the substantial ab- 10 ratio ot normal pcntane to C: and C: hydrocarsence o! other added hydrocarbons and fractionbons subjected to the reaction being between ally distilling a C4 fraction from the resulting about 1:1 and about 1:7, and said Cz and C: hyproducts; the molal ratio oi normal pentane to droom-bons being taken from the group consist- C: and C1 hydrocarbons subjected to the recing o! ethane, ethylene. propane. and propylene. tion being between about 1:1 and about 1:7, and l5 said Cz and C: hydrocarbons being taken from CLARE KENNETH VILAND. the group consisting oi' ethane. ethylene. propane, Y. HYDE.

and propylene.

CERTIFICATE 0F CORRECTION. Patent No. 2,588,099. October 50, 19).;5,

CLARE ENNE'IH VIIAND, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered Vpatent requiring correction as follows: Page 1,` secpnd calm, 411n@ 26V after "enters" insert --mco--g line 51+", for` "150 F." read --1150o F.-; page 2, second column, line 25, for "polymeriz'i-ngf' read -po1ymerization; and that-the dsaid Letters Patent '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 5th day .or Februar-y, A. D. 19146.'

Leslie Frazer (Seal) First Assistant Commissioner of Patents.

4 aandoen acted normal pentane. and returning at least a 9. A process of producing drocarbong portion of said recycle fraction to the process to which comprises: heating normci lntane to a. loin said nrst mentioned stream: the molal ratio cracking temperature in the order ci' 1000 F. to of normal pentane to Ca and C: hydrocarbons 1300 F. while in the presence of an added quan# subjected to the reaction being between about 1:1 5 tity of C: and Ce hydrocarbons and 1n the suband about 1 :7. stantial absence oi' other added hydrocarbons. and

8. A method comprising thermally cracking at maintaining such temperature for a period of time a temperature in the order of 1000 F. to 1300 F. sumcient to form a C4 traction containing in the a mixture ot normal pentane, C: hydrocarbons order ot from 60% to 80% of olens; the molal and C: hydrocarbons while in the substantial ab- 10 ratio ot normal pcntane to C: and C: hydrocarsence o! other added hydrocarbons and fractionbons subjected to the reaction being between ally distilling a C4 fraction from the resulting about 1:1 and about 1:7, and said Cz and C: hyproducts; the molal ratio oi normal pentane to droom-bons being taken from the group consist- C: and C1 hydrocarbons subjected to the recing o! ethane, ethylene. propane. and propylene. tion being between about 1:1 and about 1:7, and l5 said Cz and C: hydrocarbons being taken from CLARE KENNETH VILAND. the group consisting oi' ethane. ethylene. propane, Y. HYDE.

and propylene.

CERTIFICATE 0F CORRECTION. Patent No. 2,588,099. October 50, 19).;5,

CLARE ENNE'IH VIIAND, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered Vpatent requiring correction as follows: Page 1,` secpnd calm, 411n@ 26V after "enters" insert --mco--g line 51+", for` "150 F." read --1150o F.-; page 2, second column, line 25, for "polymeriz'i-ngf' read -po1ymerization; and that-the dsaid Letters Patent '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 5th day .or Februar-y, A. D. 19146.'

Leslie Frazer (Seal) First Assistant Commissioner of Patents.

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