US2270303A - Hydrogenation of hydrocarbons - Google Patents

Description

v. N. IPATIEFF HYDROGENATION OF .HYDROCARBONS Filed Fei. 25, 195s Jan. 20,1942.

structure of the molecules.

i Patented Jan. 2.0, 1942 UNITED v{STATI-:sa PATENT OFFICE 2,210,303 nrnaoenNArloN or maoomons Vladimir N. Ipatleil, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware 'Application February 25, 1938, Serial No. 192,595 z claims. (cieco- 676) This invention relates to a special process are believed tobe optimum,

At the present time great interest is manifested' in the production of aviation fuels which must conform to rigid requirements in respect to vola-v high antilmock rating to permit their use under severe conditions of operation encountered at high altitudes including low temperatures and high supercharging pressures. Comparatively `few hydrocarbon mixtures have been found to meet all these requirements and at the present time interest is centered around' the increased production of iso-octanes, principally 2,2,3- 'trimethylpentane and 2,2,4-trimethylpentane.

These compounds are most readily produced by controllably polymerizing the butenes present in .the so-called butane-butene fractions recover-- able from cracked gases 'followed by hydrogenation of the dimer fraction to produce octanes. Owing to the high cost of starting materials and the limited yields at present available, any proc- -ess which improves the overall eiliciency of the hydrogenating step is of immediate interest'and the present invention' is a contribution to this art.

In o'ne specific embodiment the present invention comprises the manufacture of octanes vby hydrogenating octenes in vapor phase in contact with a specially prepared composite catalyst containing reduced nickel while employing definitely limited relationships between temperature, pressure, excess of hydrogen over that required for complete saturation ofthe olefins, and definite space velocities.

It has been found'that the most efficient hy-l drogenation ofoctenes under minimum temperature and pressure conditions is brought about by using what may be termed a spaced reduced nickel catalyst of a rather definite composition and produced by a preferred sequence of steps.

ge overall composition of thev catalyst is given y T -Per cent Total nickel f 62.0 Oxygen in nickel oxide (NiO) 4.0- Graphite '6.0 Kieselguhr...,. 28.0

`stant agitation, the proportions of kieselguhr,

tility, stability in respect to gum formation, and

' approximately 1.7 moles to 1 mole of anhydrous.

It is obvious that the composition of the catalyst as given above may be varied within reasonable limits without departing from the scope of the invention. However, when the manufacture of the preferred catalytic material is conducted properly, it is generally found that the above analysis represents the composition of the iinished material very closely.

The general method of preparation of the cata-.-

lyst involves the following-steps:-Kieselguhr is suspended in a relatively dilute aqueous'solution of nickel sulfate and a saturated hot solution of sodiumcarbonate is added gradually With'connickel sulfate, and sodium carbonate being chosen so that after Washing and drying the precipitata, pelleting in admixtu're with graphite and reducing with hydrogen, a composition corresponding to that given above-is obtained. It is only necessary to employ commerciallypure sodium carbonate and nickel sulfate in the primary precipitation although for best results the reac.

tions are brought about in distilled water which can be obtained by the condensation of ordinary plant steam. As a rule a considerable excess of sodium carbonate is employed corresponding to nickel sulfate. It is important that the temperature of the suspension of kieselguhr and nickel sulfate solution be kept low and therefore the hot saturated sodium carbonate solution is added gradually so as to prevent a noticeable rise in temperature.

The primary precipitate consists of kieselguhr, nickel carbonate, and nickelous hydroxide, the composition of the particles Without the silica corresponding to the approximate formula It is probable that some of the water in this formula is associated with the kieselguhr. The

relative amounts of carbonate, hydroxide, and water will depend to some extent upon the con-` ditions of drying;

The dry precipitate is now mixed with-1% cf ,its weight of powdered graphite and pelleted into` small cylindrical forms of approximately 31's ydiameter and 1/8" thick in any standard typ of pelleting machine. The approximate composition of the material at this point is given below:

. Per cent Total nicke1- .40 Carbon dioxide Y, 7 i Total water f 20- Oxygen in nickel oxide (NiO) 1lA Graphite 4 Kieselguhr ---i i 18 The formed pellets which stm contain .the mixture of carbonate and hydroxide are now heated in a stream ofv air or nitrogen at a tempei-ature of approximatelyT300?I C..(5'12 F.) `to eliminate carbon dioxide. At this temperature vit preceding tabulation. Analyses have indicated that in the formation of the catalyst composite of the preferred composition the following reactions take place in the decarbonizing and reduction steps:

In the heating and reduction steps the porosity and hence the contact surface of the composite catalyst pellets is greatly increased and the crushing strength of the pellets is reduced to approximately 50% of their original value, this still being sufficiently high enough so that the pellets may be used in beds of reasonable depth in practice without crushing to produce fines.

Using the catalyst prepared as above described it has been found that the best hydrogenating temperatures are within the range of approximately 17o-215 C. (338419 F.) and that for the most effective operation the hydrogenation is conducted by counter-current methods in two stages whereby the octenes are partially hy- .drogenated in a primary stage using an amount of hydrogen inadequate to effect complete saturation and wherein the partially hydrogenated octene mixture is nally treated with a sucient excess of hydrogen in the secondary stage. The

catalyst is preferably contained in parallel tubes of relatively small diameter between distributing headers, the tubes being surrounded by a cooling medium to maintain theL temperature Within a close range since the hydrogenating reactions are exothermic and heat must be extracted. It has further been found for most eilicient operation that the space velocities (which are defined asthe volume of liquid octenes admitted to a given volume of catalyst space per hour) are all in the neighborhood of a value of 4. The attached graph designated as Figure 1 was made up from the data obtained from a series of runs in whichl temperature, pressure, and ratio of moles of hydrogen to moles of octene vapors were varied. The area included between the full lines represents the preferred area of operating condil tions for the two-stage hydrogenation operation mentioned. vIt will be seen from the indicated limits of this area that for optimum results a temperature of 420 F. should not be exceeded and that no beneficial effects are obtained in utilizing pressures of over 200 lbs. per square.

and temperatures by the use of the graph is to insure completely vapor phase conditions in the mixture of hydrogen and octene vapors entering per hour.

the catalyst tubes since single phase conditions are necessary for proper distribution and hence accurate temperature control of the entering mixture. For example, if a ratio of hydrogen to octene vapors of 0.6:1 is employed in the primary stage of hydrogenation along with a temperature of 390 F. it will be seen from the graph that a pressure of lbs. per square inch may not be exceeded if completely Vapor phase conditions are to be assured. Similarly for a ratio of 1.4:1, which may be employed in the second and final stage of hydrogenation, if the same temperature of 390 F. is used, the pressure can be increased to 188 lbs. without fear of the appearance of liquid and consequent unequal distribution.

The following example is` introduced to show the character of the results obtainable in the operation of the process but not with the intention of unduly limiting its scope.

An octene fraction produced by the selective polymerization of iso-.butylene to form a mixture of dimers was vaporized and passed over a re duced nickel catalyst of the composition shown in the specification in a two-stage hydrogenation. In the first stage the temperature employed was 330 F., the/molal ratio ofhydrogen to octene vapors was 0.6:1 and the pressure was 100 lbs. per square inch. In the second stage a temperature of 390 F. was employed with a molal ratio of hydrogen to octene vapors of 1.4:1 and a pressure of 180 lbs. per square inch. As a result of this operation, the octene mixture was 96% hydrogenated to a mixture of octanes consisting principally of 2,2,3-trimethyl pentane and 2,2,4-trimethyl pentane. The octane number of the hydrogenated product as determined by the motor method of testing being 98.

I claim as my invention:

1. A continuous process for the hydrogenation of octenes which comprises subjecting the vapors of said octenes in admixture with a molal excess of free hydrogen of less than 60% to contact with catalytic material comprising approximately 62% nickel, 4% oxygen combined in nickel oxide, 6% graphite, and 28% kieselguhr at temperatures within the range of -2l5 C. under pressure of from atmospheric to 200 lbs. per square inch and times of contact corresponding to liquid space velocities of approximately four per hour.

2. A continuous process for the hydrogenation of octenes which comprises subjecting the vapors of said octenes in admixture with from 40 to 80% -of the moles of free hydrogen necessary for their saturation to contact with catalytic material comprising approximately 62% nickel, 4% oxygen combined in nickel oxide, 6% graphite, and z8 kieselguhr at temperatures within the range or' 170-215 C. under pressures of the order of 100 lbs. per square inch in a primary stage, subsequently subjecting vapors of the partially hydrogenated products in a secondary stage in admixture with from 100 to 160% of the moles of Iree hydrogen necessary for their saturation to Contact with catalytic`material similar to that employed in the first stage at temperatures within the rangehof 17o-215 C. under pressures of approximately 200 lbs. per square inch while maintaining a liquid space velocity of about 4 VLADIMIR N. IPATIEFF.

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