US1871786A - Production of propylene - Google Patents

Description

portions of these three constituents vary con- Patented Aug. 16, 1932 UETED SAT'ES WILLIAM A. GERSTMYER AND WEAVER n. onAYroN, or nnnrriuonn, MA'n LAitn As- SIG-NORS 'ro COLUMBIA ENGINEERING annraanasnlvrnnr oonronarron, or news;

YORK, N. 'Y., A CORPORATION OF OHIO rnonucrron or rnorrnnun No Drawing.

' This invention relates to decomposition of hydrocarbons and the production of other hydrocarbon compounds, and more particularly to thermal decomposition of hydrocar- F bons boiling between -90 and 36 (3., es-

pecially butane, to produce propylene.

Commercial butane consists of a mixture of butane, iso-butane and a small amountof propane, present as an impurity. The prosiderably, depending upon the source of the natural gases from which the commercial butane is condensed. Typical analyses of commercial butanes include 1 to 5% of propane, 5 5 to 10% of iso-butane and 87 to 9 1% of hutane. cordance with the invention to produce propylene and other hydrocarbon compounds or mixtures thereof including pentane, bu tane, propane and ethane may be utillzed likewise for the purpose of the invention.

It isknown that hydrocarbons such as butane undergo decomposition or cracking when heated to relatively high temperatures. The usual reactions may be indicated:

1. (3 H C l-1 CH 2- G,;Hu OgH dGgH 3. 041110 O4H3+H2 According to reaction 1, propylene and methane are the products; ethylene and ethane steel tube is used the ratio of propylene to ethylene is only 2.3 1.

It is not essential that the copper be pure, as brass tubes produce a. similar effect, that is, the product will contain a ratio of propylene to ethylene of 6: 1. Copper in any form Such materials may be treated in ac Application filed December 14, 1929. Serial no. 414,218. I

'beusedto direct the reaction, forexample, copper filings or turnings, or filings or .turnings of brass or other copperalloys can be employed in a tube of any material which does not affect the reaction'adverselyn The essential factor is the presence of copper in such form as to permit efi'ective control of the vapors therewith at the cracking temperature. i

In the preferred form of the invention, the :7 vapors of butane or mixtures of butane with other hydrocarbons are conducted" through vapors contact therewith. A temperature of 700 C; is satisfactory, but the temperature is not critical and may varywidely with reference particularly to the rate of flow. The

temperature and rate of flow can be increased or decreased simultaneously to aiford'the best cracking conditions which have been found by eztperiment to be such that for every volnine-of butane passedthe volume of cracked gases is increased 0.29. This isexpressed by the ratio of the'volume of butane to the volume of the productwhichshould be about 1:129. Under such conditions a yield of about 18% by volume of propylene should be obtained, based on the volume of the gaseous mixture entering the chamber.

' As anexample of the invention, commercial butane is passed through a reaction tube of copper or steel lined with copper about three feet long and one inch internal diameter. About one third of the tube is heated to about 700 C. The rate of flow is such that the vapor remains in the cracking zone for about 1.7 seconds. The product will b contain about 7.8 parts by volume of propylene to each part by volume of ethylene.

No satisfactory explanation of the mechanism of the reaction or the exact effect of copper thereon is avialable. Presumably copper acts as a catalyst of the propylene forming reaction and thus directs it so that higher ratios of propylene are produced in the presence of copper than are obtainable otherwise.

Various changes may be made in the details of operation or procedure and particularly in the apparatus employed, without departing from the invention or sacrificing the advantages thereof.

We claim: I 1. The method of producing propylene which comprises thermally decomposing .a I mixture of aliphatic hydrocarbons consisting "essentially of butane and iso-butan'e by passing the material through a heated chamber in'the presence of copper at a rate such that the ratio of the initial volume to thevolume I of the gaseous product is about 1':1.29.

2. The method of producing. propylene which comprises thermally decomposing a mixture of a liphatic'hydrocarbons consisting essentially of butane and iso-butane byp'assing the material through a heated chamber of about one inch internal diameter'in the presence of copper for a period of about 1.7 seconds. I

3. The method of producing propylene in agaseous mixture containing 18% or over of propylene and from two to three percent of ethylene which comprises thermally decomposing a mixture of aliphatic hydrocarbons consisting essentially ofbutane and iso- 1 butane bypassing the material through a heated chamber in the presence of copper at atemperature of about 700 C. and for a period of about 1.7 seconds so that the'ratio of the initial volume to the volu'me of the gaseous product is about 1: 1.29. i

4-. The method of producing propylene which comprises thermally decomposing a -mi'xture of aliphatic hydrocarbons consisting-essentially of butane and iso-butane by passing'jth'e material through a heated chamher in the presence of copper at a te-mperature of about. 7 00 C. so that the ratio of the initial volume to the volume of the gaseous product is about 1:1.29;

o In testimony whereof we affix our signa- I tures. V

WEAVER R. CLAYTON. WILLIAM A. GERSTMYER.