US2176962A - Process for producing ethylene from oil - Google Patents

Description

Oa. ,24, 1939.v

J. J. GREBE PROCESS FOR PRODUCING ETHYLENE FROM OIL Filed April v22a, 1938 l Y N Pressa/'e NVEN TOR.

A TTORNEYS.

Patented Oct.'24, 1939 I PATENT "OFFICE PROCESS FOR PRODUCING ETHYLENE FROM OIL John J. Grebe, Midland, Mich., assignor, by mesne assignments, to Theodore Nagel, New York'.

Application April 28, 1938, Serial No. 204,831

2 Claims.

This invention relates to methods for the pro' duction of unsaturated hydrocarbon gases by the pyrolysis of liquid hydrocarbons. More particularly, it is concerned with an improved pro- 5 cess for the cracking of yhydrocarbon oils to produce a iixed gas of which the major constituent is ethylene, together with a smaller proportion of other olenes containing not more than four carbon atoms per molecule.

It is an object of the present invention to produce ethylene as the principal product of an oil cracking operation in which the major portion of the charging stock is converted to fixed gases under such conditions that the yield of conll densate', oil, tar, and the like, is minimized, i. e., so that not in excess of 30 per cent of condensate by weight of the charging stock, and preferably not in' excess of 10 per cent condensate, is obtained. Another object of the invention is to obtain a high yield of ethylene from a preheated liquid hydrocarbon, as high as 45 per cent by weight of the stock charged, while preventing polymerization in the gases produced.

My process producesv these results from liquid 25 hydrocarbons in a continuous operation, the process comprising the operations of preheating the liquid oil under super-atmospheric pressure to a sufficiently high temperature, e. g., to a temperature slightly below. its vaporizing temperature 30 at the pressure employed although lower temperatures may be used, then injecting all of the preheated liquid oil into a hot gaseous medium, such as superheated steam, which contains sufcient heat for the heat exchange to the preheated oil to ash-heat the oil to within the temperature range of 700-900 C. (about 1300"- 1600 F.) whereby substantially all of the oil cracked is 'converted to ethylene and hydrocarbons containing not more than four carbon atoms per molecule, this hot gas being then immediately shockchilled to a temperature below that at which the ethylene or other olenes polymerize readily, thus substantially excluding polymerization of the olene products.

In the annexed drawing there is illustrated diagrammatically the ow of materials in the process constituting my invention. The oil tovbe cracked is taken from any suitable source I and is forced through a preheater 2 under super- 5o atmospheric pressure, e. g., 2 to 20 atmospheres.

into a reaction chamber 3. In the pheheater 2 the temperature of the oil is raised to between about 150 C. and about 500 C. (300-950.F.), e. g., to about 450 C. (850 F.) under such conditions that substantially all the oil remains'in the liquid phase. This preheated liquid oil is continuously injected into a hotter reaction chamber 3 and Aflashes into vapor, the tempera-- ture of the hot reaction zone being so controlled within the range 650'900 C. (1200-1600 F.) 5 that substantially all of the oil vapor cracked is converted to ethylene and other gaseous hydrocarbons containing not more than four carbon atoms per molecule.

The hot cracked gases formed in the reaction 10 chamber 3 pass directly to a cooler 4 where they are shockchilled, preferably by means of water or a relatively cool fluid injected into said cooler, to a temperature below that at which there occurs any substantial polymerization of the ole- 16 fines to form gasoline hydrocarbons, e. g., to below about 550 C. (1000 F.). In this Way the yield of condensate is minimized, not more than 30 per cent of condensate by Weight of the charging stock, and frequently not more than 10 per 20 cent of condensate, being obtained. The small proportion of condensate is removed to storage 5 and the iixed gases 6 are withdrawn from the shock-cooler 4 to be treated in any known manner to separate the ethylene from other products of pyrolysis. l

As hereinbefore explained, the preheated liquid oil being cracked to ethylene is at least'partially flashvaporized into the hot reaction chamber 3. The source of heat in this reaction zone is a hot gaseous medium 1, e. g., a superheated condensible vapor such as steam or a hot xed gas. for example hydrogen, carbon monoxide, etc., which is raised 'to the required temperature in a heater 8. This heater may take any suitable form, such as an externally heated coil or a superheater of the type described in United States Patent 2,113,536. The temperature of the hot gaseous medium flowing through the reaction chamber 3 from the vapor-heater 8 is so controlled that the gas contains sufficient heator heat exchange to the preheated oil injected into v the reaction chamber 3 to flash-heat said oil to within the desired range of reaction temperathe oil is instantantly gasiiied substantially to ethylene and hydrocarbons of not more than four carbon atoms. Y -A In practicing the invention, the liquid hydrocarbons used as the charging stock maybe gasoil and oils heavier than gas-oil, but any hydro'l 50 carbonwhich is liquid under pressures of up to 20 atmospheres or higher at temperatures up to v 450 C. (850 F.) may be employed. It'is to be understood that with different charging stocks the temperature at which the reaction takes place and the reaction time necessary to obtain optimum 'yields of ethylene will vary, but\ in any case the reaction time should not exceed about I 1% seconds 'and the temperatures should-not beA 5 less .than about 650 C. (1200 F.) 'to avoidproducing a larger proportion of liquid condensate. At temperatures materially above 900 C. (1625 F.) the yield of ethylene decreases, so that operation at such elevated temperatures is not deslrable. 'Ihe reaction time generally varies in inverse relation to the temperature, preferably ranging from approximately 1%- seconds to less than l/ second, e. g., as low as 1,60 second, in order tov obtain the optimum yield of ethyleney and other olenes.

The following examplev is illustrative of the invention but is not to be construed as limiting the scope thereof:

In a continuous run a fuel oil having a specific 4 2o gravity of 0.877 was preheated under a pressure of 35 pounds gage to a temperature of about 220 C. (428 F.) and was injected into steam supplied at '1.5 pounds pressure and superheated to a temperature of about 1170 C. (2138 F.) .l

The oil vand steam were supplied tothe reaction chamber in the ratio of 3 pounds of steam per pound of v'fuel oil in such proportions that the average temperature Ain the cracking zone was about 800 C. (1472 F.) and the reaction time was of the ordenof 0.0135 second. When opera ating in this manner, 9.5 cubic feet of dry xed l gas (measured at 60 F.) and 0.2 pound of condensate were obtainedrper pound of oil charged.

'I'he averageanalysis of this gas on a dry basis was 'as follows: v

Per .cent by volume Other modes of applyingthe principle lof my invention may be employed, changebeing made as regards the details disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

'I therefore particularly point out and distinctly claiml as my invention:

1. The process of producing ethylene from oil,

which process comprises preheating the oil under superatmospheric pressure while maintaining the oil slightly below its vaporizing temperature at that pressure, injecting all of the preheated liquid oil into a flowing superheated condensible vapor whichr contains sufficient heat for heat exchange to the preheated oil to dash-heat thef preheated oil'to within the temperature range of 1300 F. to 1600I ll., at which temperature all of the `hydrocarbons of the oil are instantly decomposed to ethylene and hydrocarbons of not more than four carbon atoms, and immediately upon attaining this temperature shock-cooling the gaseous mixture to below 1000 F. to exclude polymerizing reactions forming gasoline hydro- .carbons and to retain the hydrocarbons as ethylene and hydrocarbon of not more than four carbon atoms.

2. The process of ,producing ethylene from heavy oil, which process' comprises preheating the oil to a temperature in the order of 850 F.

while subjected to superatmospheric pressure,

controlling pressure and time conditions while preheating so that the oil remains in the liquid phase, injecting allot the preheated oil into a flowing superheated condensible vapor which contains suillcient heat for heat exchange to the preheated oil to dash-heat the preheated oil to within the temperature range of 1300 F. to 1600 F., at which temperature all of the hydrocarbons of the oil are instantly decomposed to ethylene and hydrocarbons of not more than four carbon atoms, and immediately upon attaining this temperature shock-cooling' to below 1000 F.

to exclude polymerizing reactions forming gasoline hydrocarbons and to retain the hydrocarbons as ethylene and hydrocarbons of not more than four carbon atoms.

Y JOHN J. GREBE.

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