US2397638A - Conversion of hydrocarbons - Google Patents

Description

Fatented Apr. 2, i

2.391.638 I coNvEnsroN or nrnaocsanons Richmond T. Bell. Deerfield, Hiliis 0. Folkins, Skohle, and Carlisle M. Thacher, Highland Park, Ill., assignors to The Pure Oil Company, Chicago. 111.. a corporation of Ohio Application March 27, 1943, Serial No. 480,864

5 Claims. (Cl. 196-52) This invention relates to conversion of hydrocarbons and is more particularly concerned with a method for cracking hydrocarbons into lower boiling hydrocarbons and for making unsaturates from saturated hydrocarbons.

It is well known in the conversion of hydrocarbons to use various halogen compounds in small amounts as sensitizers to promote the progress oi the reaction. It is also well known to use small amounts of oxygen or air in admixture with hydrocarbons undergoing conversion in order to promote the reaction.

We have discovered that the conversion of hydrocarbons can be greatly accelerated by using a combination of a hydrogen halide and tree ozone or tree oxygen-containing gas, such as air or. oxygen, in relatively small amounts in mixture with hydrocarbons undergoing conversion.

An object of our invention is to provide a method for conversion of hydrocarbons.

Another object of our invention is to provide a method for accelerating cracking of hydrocarbons,

Still another object oi our invention is to provide a reagent which will accelerate decomposition of hydrocarbons.

A still further object of the invention is to improve the method of cracking hydrocarbons in conventional types of thermal cracking apparatus.

Other objects of the invention will become apparent from the following description. The drawing is a graphical representation 01 data obtained on certain runs'made to demonstrate the utility oi our invention. I

In accordance with our invention a small amount of hydrogen halide including hydrogen chloride, hydrogen bromide. hydrogen iodide, and hydrogen fluoride or'rnixtures thereof and a small amount of ozone, air, oxygen or other free oxygen-containing gas is mixed with the hydrocarbons subjected to decomposition. The free oxygen-containing gas and the hydrogen halide may be mixed with the hydrocarbons prior to charging it to the reaction zone, or may be injected directly into the reaction zone. Ii proportions ranging from approximatelyzfi to 5 mole per cent of hydrogen halide and approximately .25 to 5 mole per cent of oxygen, based on the mixture, are

used the reaction is greatly accelerated. Care should be exercised to guard against use of such large amounts of oxygen as to make an explosive mixture with the hydrocarbon. It should be understood, however, that the invention does not preclude the use of explosive mixtures where apparatus is provided capable of withstanding the explosive shock and proper technique is used. We have found that an amount of free oxygencontaining gas which contains an amount of tree oxygen approximately equal to the amount stoichiometrically required to oxidize the hydrogen halide to water and free halogen gives good results. The aforementioned proportions may be departed from to some extent without sacrificing the advantages accruing from the invention.

The combination of hydrogen halide and free oxygen-containing gas accelerates decomposition of hydrocarbons to a greater extent than would be expected from the additive acceleration of the hydrogen halide and tree oxygen-containing gas separately. In order to demonstrate the effect oi the combined hydrogen halide and free oxy gen-containing gas a number of runs were made using n-butane as charging stock and cracking it at a temperature of 525 C. In the runs made a Pyrex glass reaction vessel was heated to a temperature of 525 0., and was evacuated by means of a vacuum pump to a pressure below 0.001 mm. of mercury and suflicient butane in admixture with a small amount of the sensitizer composition was then charged to the evacuated vessel to raise the pressure inthe vessel to approximately atmospheric pressure (760 mm. of mercury). The reaction was permitted to proceed in the closed reaction chamber while the temperature was maintained at 525 C. until a pressure increase 01' 25% over the initial pressure was obmrved, whereupon the reaction gases were rapidly removed from the reactor and analyzed. A number of runs were made withoutany sensitizer in order to determine the rate of reaction without sensitizer. The results obtained on a number oi representative runs are reported in the following Table I. The figures for the blank run represent the average of three runs made without sensitizer. During each run, the time for increase of pressure of 5%, 12.5% and 25% I was recorded.

2' aso'mss Tom: 1'

Time in minutes Sensitization factor ior pressure infor pressure in- Run Bensitizer and crease oicrease oi- No. moi. percent H thetice time for 25% pressure increase 7 2:5,,air 0.3

from the curves on the drawing for runs 93 and I IOB.

Curves I, 2, 4, 5 and 1 are plottedon observation taken of pressure increase at interval of oneor two minutes in the respective runs. The Hypothetical time for 25% pressure increase" for run 513 is obtained by adding the pressure increases obtained at any selected. time from curves'3 and 5. plotting the figures so obtained as points on the graph, drawing a curve through the points and -then reading the time for 25% pressure increase from the curve (6). For example, after 6 minutes, the blank gave a pressure increase of 10.05%. 2.5% of air gave a pressure increase of 12.65% and 1% of HE! gave a pressure increase of 17.9%. Thus the additive increase expected from 2.5% of air and 1% of HBr after 6 minutes is or 10.45%. By adding the expected additive increase of 10.45% to the increase of the blank after 6 minutes (10.05) the expected or hypothetical increase is 20.5%. By repeating this process for a sufllcient number of selected periods,- a sufficient number of points are obtained to draw a -curve from which the expected or hypothetical v TABLE 11 Analysis of gas from run B Percent by volume of CO 0.4- Hz 0.7 Acids 0.0 Unsaturates 22.6

Residue 76.3

5 The invention is applicable to th cracking'of both low and high boiling hydrocarbon within a temperature range of approximately 375-750 C. The invention is useful in connection with well known commercial mineral oil thermal cracking operations for making gasoline, in order to accelerate the rate of cracking and is useful in connection with catalytic cracking operations wherein a solid comminuted catalyst such as clay or synthetic alumina-silica compositions are used. The invention is likewise useful in thecracking of both liquid and gaseous hydrocarbons to make unsaturated hydrocarbons as for example the cracking of butane to ethylene and propylene or the cracking of gasoline boiling hydrocarbons to butadiene.

We claim:

. 1. The method of cracking hydrocarbons which consists in subjecting said hydrocarbons to temperatures suitable for cracking thereof in the presence of approximately 0.25 to 5 mole of hydrogen bromide and approximately 0.25 to 5 mole of oxygen.

2. The. method. in accordance with claim 1 in which the' oxygen is present in the form of air.

40 3. The method of cracking high boiling hydrocarbons to hydrocarbons within the gasoline boiling range which consists in subjecting said hydrocarbons to temperatures'between approximately 375 C. and 750 C. in the presence of approximately 0.25 to 5' mole of a hydrogen bromide and approximately 0.25 to 5 mole of oxygen.

4. The method of cracking hydrocarbons tohy- I drocarbons of lesser number of carbon atoms without the aid of solid cracking catalysts com- 5 prising subjecting said hydrocarbons to temperatures suitable for cracking thereof in the presence of hydrogen bromide in an amountbetween ap proximately 0.25 and 5 mole percent and oxygen in an amount between approximately 0.25 and 5 5 mole percent.

5. The method of cracking hydrocarbon oils to I lower boiling liquid hydrocarbons comprising subjecting said 011 to cracking temperatures between 375. C. and 750 C. in the presence of a small amount of hydrogen bromide and oxygen.

RICHMOND T. BELL. HILLIS O. FOLKINS. CARLISLE M. I'I-IACKER.

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