US2425506A - Production of premium aviation fuel components - Google Patents

Description

Aug. 12, 1 947. s. R. BETHEA PRODUCTION OF PREMIUM AVIATION FUEL COMPONENTS Filed July 13, 194;,

Light Hyd rocarbons Staa In Nam/u y la Bl/TYZEIYEJ Catalytic Dahydraganation Qucnchmq II. Zona Zane l6 0 Hydrocarbons 23 Clay Contacting Zane Ii I d Hydrgganaflan Pramiull 3| Aviation wn/7k nrroausv.

Patented Aug. 12 1947 PRODUCTION OF PREMIUM AVIATION FUEL COMPONENTS Sam R. Bethea, Baytown, 'lex'., assignor to Standard Oil Development Company, a corporation of Delaware ApplicationJuly 13, 1945, Serial No. 604,838

Claims.

- The present invention is directed to a process for producing premium aviation fuel components.

The process of the present invention may be described briefly as involving the steps of catalytically dehydrogenating a C4 fraction containing mono oleflns in the presence of large amounts of steam to obtain a product rich in aromatics, mono-oleflns and diolefins, fractionally distilling the product from the dehydrogenation step to separate a fraction including the Ca hydrocarbons and boiling up to approximately 350 F., treating this fraction with clay to polymerize at least a major portion of the diolefln and the more reactive mono-olefins therein, separating product from the" clay treating step and in distilling to separate a fraction boiling up to 350 F. and subiecting this fraction to a mild hydrogenation step to obtain a product suitable for inclusion in a premium aviation fuel.

The practice of the present invention will now be described in greater detail in conjunction with the drawing in which the sole figure is in the form of a diagrammatic flow sheet illustrating a preferred modification of the present invention.

Turning now specifically to the drawing, a C4 fraction, for example, a C4 fraction containing a major amount of butylenes and minor amounts of butanes, is passed through an inlet II and is mixed with a large amount of steam injected through inlet l2. The mixture .of C4 hydrocarbons and steam passes into catalytic dehydrogenation zone H! where it is contacted with a catalyst under temperature and pressure conditions which cause the formation of relatively large amounts of dioleiins as well as higher boiling mono-oleilns and aromatics. It is preferred to maintain the cat-' alytic dehydrogenation zone at a temperature within the range of 1050 to .1300 F. and at a pressure within the range of 1 to 2 atmospheres absolute. Under these temperature and pressure conditions the catalyst employed may be any of the known dehydrogenation catalysts, such as one consisting of 80% MgO, 14% Fezoa, 3% K and 3% CuO. In the catalytic dehydrogenation zone it is preferred to have superheated steam admixedwith the hydrocarbons within the range of 3 to 15 volumes of superheated steam per volume of hydrocarbon and this mixture is preferably passed over the catalyst at space velocities within the range of 2 to 500 volumes of feed per volume of catalyst per hour.

Product is removed from catalytic dehydrogenation zone 13 via outlet I! and is passed to a'quenching zone l5 where the temperature of the (Cl. 260-0835) i drawing, the quenching zone l5 appears as a rectangular member. In practice, it will usually be desirable to divide the quenching zone into several steps, using, for example, a water spray, an oil spray and a subsequent water spray to cool the product from the catalytic dehydrogenation zone and from each of these stages. the mixture of quenching liquid'and product is withdrawn and separated prior to passing the product to the subsequent stage. The quenching of the product removed from the catalytic dehydrogenation zone in itself i not considered an inventive feature in the present case and is not shown in detail in the drawing; the zone designated by numeral l5 will be understood to include as many quenching steps and separating steps as necessary in order to produce a quenched liquid product which In the fractional distillation tower n, the low boiling dio'lefin components, such as butadiene and pentadiene, which in themselves are valuable products, are separated from the relatively less valuable higher boiling components. In the drawing, the low boiling components, which may include butadiene and pentadiene, are indicated as being withdrawn as overhead through outlet l9 while the heavier components which are indicated as being Cc plus hydrocarbons are removed as a higher boiling fraction through outlet 20. In commercial practice it will be understood that the fractional distillation step may be conducted in a plurality of fractionating towers and a fraction containing buta'diene and a fraction containing pentadiene may be separately removed from the distillation step and subjected to further treatment to concentrate the valuable butadiene and pentadiene fractionsbut these manipulative steps are well known to the art and are not shown in detailin the drawing.

The fraction withdrawn from the'fractional distillation step lI through outlet 20 includes the Ca and higher bolling,hydrocarbons and comprises substantial amounts of aromatic hydrocarbons-as well as diolefin and mono-olefin constituents boiling in the range from about to about. 350 F. This fraction is treated to remove at least the major portion of the diolefins and with clay at a temperature substantially above atmospheric to polymerize the diolefin and more reactive mono-olefin constituents and the product fromthe clay treating step is subsequently distilled to separate it into a lower boiling condensate fraction and a higher boiling bottoms fraction containing the bulk of the polymer pro.

. duced in the clay treating step. In the drawing the treatment for removing the diolefln and more reactive mono-olefin is indicated by passing the Cs and heavier hydrocarbon fraction from line a through furnace 2| where it is heated to a temperature substantially above atmospheric, for example, approximately 400' it, and the fraction passes from furnace 2| through line 22 to clay treating zone 23 maintained at a pressure of about 100 lbs/sq. in. Various types of clay may be employed in zone 23-, such as Attapulgus clay or fuller's earth. The naphtha fraction is maintained in contact with the clay in treating zone 28 for a time interval of approximately 2 hours at a temperature of approximately 400 F.- Product is removed from clay treating zone 23 through outlet 24 to a fractional distillation zone indicated as distillation tower 25 provided with a heating coil 20. In the distillation zone, the product from the clay treating zone is separated into a lower boiling fraction removed through outlet 21 and a heavier fraction containing the bulk of thepolymers which are removed through outlet 20.

The fraction in line 21 is preferably obtained by operating the fractional distillation zone to produce an overhead fraction boiling up to 350 F. and this fraction, substantially free from dioleflns and the more reactive mono-oleiln's, is subjected to a mild hydrogenation step in zone 29 to produce a product suitable for use as a 1 premium aviation fuel base stock. It is preferred to employ a catalyst of the type of nickel sulfidetungsten sulfide in zone 29 and to contact the vaporized naphtha with the catalyst at a temperature within the range of 400 to 600 F. The pressure within zone 29 may conveniently be within the range of 200 to 240 pounds per square inch and the volume of liquid per volume of catalyst per hour is preferably within the range of 2 to 3. On a large scale unit which'allows the naphtha charge rate to be varied within the range of 8,000 to 17,000 barrels perday, the hydrogen charge rate may be within the range of 800,000 to 1,500,000 cubic feet per hour.

The product from the hydrogenation zone 29 is removed through outlet 30 and is suitable, after blending. for use as a finished premium aviation fuel. Accordingly, the product is passed to a blending step, indicated in the drawing by rectangle 3|, and the finished product is withdrawn through outlet 32. It will usually be found desirable to blend the product from the mild hydrogenation step with isopentane and tetraethyl lead to obtain afinished product.

It is to be emphasized that the Ca and heavier hydrocarbon fraction separated from the product of the dehydrogenation zone must be subjected columns 1 and 2; and the results were entered in column 3.

x Table Clay Clay Treated None and Hydro- Treated gamma 7 Treatment Given to Bottoms Clay Treater Employed l Temp. of Clay treat, F. 340 340 Time of Clay Treat Hours 2.4 2. 5 Bromine No. of aw Charge ck, cgmJgm 130 130 130 Bromine No. of Polymer-free Product, cgmJgm 62.3 1. 0 Yield of Final Polymer-free Prodnot based on raw stock, Vol.

per cent 100 73. 0 71. 0

Impediom on Final Polymer-Free Produd 4a. 9 3a 0 40.4 I31, 98 168 175 FBI, ra... 330 see ass 5% 01! at, F.-. 120 206 207 6% of! 223 244 240 9 off at F 325 290 278 e? add d i d 4 6 e sopentane an cc. letraethyl lead rgallon... 84.0 95.2 0 Diane Number, cgm. gin 27.0 ASTM Gum, mg./l00 cc 609. l l. 0

first to a clay contacting step to polymerize the active dioleflns and mono-oleflns, the resulting polymer separated and the remaining material mildly hydrogenated in order to obtain a material suitable for use as a premium aviation fuel.

The clay contacting step in itself will not produce a product of sufliciently high quality for use in an aviation grade fuel. If the Ca and heavier fraction obtained from the product of the catalytic dehydrogenation zone is sent directly to a hydrogenation zone without a prior clay contacting treatment, its high gum content rapidly fouls the exposed surfaces of the equipment and soon renders the process inoperable.

The results obtained in the practice of the ample:

Exmnu A 04 fraction containing approximately n-butylenes, 8% isobutylen and 12% butanes was subjected to catalytic dehydrogenation at a temperature of approximately 1200. F. in the presence of a catalyst consisting of approximately 80% MgO, 14% Fez0a, 3% K20 and 3% CuO. Product from the dehydrogenation zone was quenched and fractionated and from the Co and heavier fraction three samples were obtained. The first of th samples was given no further treatment except blending and was subjected to inspections, the results of which are set out in column 1 ofv the following table. The second sample was subjected to a clay treatment step and the conditions of the treatment and characteristics of the product resulting from the treatment are set out in column 2 of the table below. The third sample was subjected to a clay treatment under the same conditions as the sample of column 2 and from the product of the clay treatment was separated a distillate fraction boiling within the range of Co to 350 F.; this latter .fraction was hydrogenated at a temperature of 450 F., a pressure in the range of to 1'70 lbs/sq. in., and the feed rate of the hydrogen and naphtha adjusted to a mole ratio of 4.25:1 in the presence of a nickel sulfide-tungsten sulfide catalyst with the ratio of naphtha feed (liquid volumes) per catalyst volume equal to .83:1. The product from the mild hydrogenation step was then subjected to the same inspections as the fractions listed in Fixed bed. i

It will be seen that the product obtained when dehydrogenating a C4 fraction in the presence of steam and catalyst was given a clay treatment with a subsequent hydrogenation treatment resulted in a material which when blended with isopentane and tetraethyl lead had an aviation octane number of slightly above 95.

While I have given a specific example illus-,

trating the practice of the present invention and have given preferred operating conditions, it will the purpose of illustrating the practice of the invention.

Having fully described and illustrated the present invention, what I desire to claim as new and useful and secure by Letters Patent is:

1. A method for producing premium aviation fuel components including the steps of catalytically dehydrogenating a C4 fraction including a major amount of normal monoeolefln to produce a product including substantial amounts of mono-olefin, diolefln and hydrocarbons boiling above 110 F. distilling the resultant product to separate a fraction boiling in the range of 110 to 350 F., contacting said fraction with clay at a temperature of approximately 400 F. to polymerize at least a major portion of the dioleiin therein, removing product from saidclay treating step, distilling to separate a fraction boiling up to 350 F. and mildly hydrogenating it to obtain a fracton suitable for inclusion-in a premium aviation fuel.

2. A method in accordance with claim 1 in sulfide catalyst.

3. A process for producing premium aviation fuel components including the steps of passing a vaporized C4 fraction including normal monofraction boiling. in the range .of-approximately olefin into a dehydrogenation zone where it is brought into contact with a dehydrogen'ating catalyst in the presence of steam to form substantial amounts of diolefln, mono-olefin and hydrocarbons boiling above F. therein, re-

moving product from said dehydrogenation zone.

fractionally distilling said product to separate a 110 to 350 F., and contacting said fraction with clay at a temperature of approximately 400 F. for no less than approximately. two hours to cause substantially complete polymerization. of the diolefln present therein, removing product from said clay contacting zone and fractionally distilling to separate the fraction boiling up to 350 F. and catalytically hydrogenating. said fraction under mild conditions to produce a product suitable for inclusion in a premium aviation fuel.

4. A method in accordance with claim 3 in which said mild hydrogenation step is conducted at a temperature within the range of 400 to 600 F. and inthe presence of a nickel sulfide-tungsten sulfide catalyst.

5. A process in accordance with claim 3 in which the dehydrogenation zone is'maintained at atemperature within the range of 1050 to 1300 F. and in which the hydrogenation zone is maintained at a temperature within the range of 400 to 600 1?. and in which nickel sulfidetungsten sulfide is employed as the'hydrogenation catalyst.

- SAM R. BETHEA. rtaraaancss crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,376,191 Roetheli May 15, 1945 2,380,876 Schulze et al July 31, 1945 36 2,202,401 Rosen May 25, 1940 Delbridge et a1- Aug. 2a, 1928

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