US1991344A

US1991344A - Treatment of hydrocarbons

Info

Publication number: US1991344A
Application number: US334589A
Authority: US
Inventors: Stephen P Burke; Charles F Fryling
Original assignee: Doherty Research Co
Current assignee: Doherty Research Co
Priority date: 1929-01-23
Filing date: 1929-01-23
Publication date: 1935-02-12
Anticipated expiration: 1952-02-12

Description

Feb. 12, 1935. 5 P, BURKE r AL N 1,991,344

TREATMENT OF HYDROCARBONS Filed Jan. 23, 1929 2 Sfieets-Sheet 1 7 52 METER commas R" I f 26 44 ha l l--J6HEATJ6{ A METE ABSORBER I INVENTORS CQHARLEs E FRYL NG bTEFHEN P- SUI-(IRE.

Patented Feb. 12, 1935 1,991,344 max m-2m or nr'naocaanous Stephen P. Burke, Plainfield, and Charles F. mling, Metuchen, N. J., assignors to Doherty Research Company, New York, N. Y., a corporation of Delaware Application January 2:, 1929, Serial No. 334,589

13 Claims.

This-invention relates to the transformation of hydrocarbons by partial oxidation into useful hydrocarbon-oxygen compounds. 4

Methods heretofore suggested for effecting the 5 partial oxidation treatment of a mixture of a hydrocarbon and air to produce valuable intermediate oxidation products (such as alcohols, aldehydes, acids and ketones) have usually contemplated contacting a mixture of the hydrocarbon and air at an elevated temperature with a solid metal or metal oxide contact catalyst capable of accelerating heterogeneous (surface) oxidation of dehydrogenation reactions. So far as is known none of these proposed methods have 3 produced altogether satisfactory yields of intermediate (as distinguished from complete) combustion products.

The primary object of the present invention is to provide a process for eifectingthe partial oxi- D dation of hydrocarbons with oxygen or air whereby satisfactory yields of hydrocarbon-oxygen compounds are obtainable.

A more specific object of the invention is to provide a process for effecting the partial oxida- 5 tion of hydrocarbons whereby the major part of the oxidizing agent is utilized in forming partial (as distinguished from complete) combustion products. I One of the principal features of the process hereindescribed is that it contemplates carrying out the partial oxidation reactions in' the absence of solid contact catalysts for heterogeneous (surface) reactions of the type above referred to. In other words the process as carried out embodies principles of homogeneous (gasor vaporphase) oxidation and utilizes a reaction vessel having its walls, and other parts in contact with the reaction mixture, preferably constructed of an inert substance having substantially no apparent surface catalytic'effect on oxidation or dehydrogenation reactions.

vWith these and other objects and features in view the invention consists in the method of producing hydrocarbon-oxygencompounds by partial oxidation of hydrocarbons which is hereinafterdescribed and more particularly defined in the claims.

Various features of the invention are illus- .0 trated in the accompanying drawings, in which: Fig. 1 is a flow sheet of the principal steps of the process, illustrating diagrammatically a cross v sectional plan view of a. preferred type of reaction chamber.

Fig. 2 is an enlarged view in vertical cross gas gasoline therefrom. If the gas is known to section of a reaction chamber of the type shown in Fig. 1. N

Fig. 3 is a curve showing the rather wide temperature range within which partial oxidation of several of the lighter hydrocarbons of the paraflln series may be carried out.

Fig. 4 is a curve illustrating the narrow temperature range within which the reactionmay go to completion once it has been initiated.

Fig. 5 is a curve showing the effect of variation in pressure on the temperature at which partial oxidation takes place.

The improved process may be carried out according to the plan illustrated in the accompanying flow sheet substantially as follows:

A hydrocarbon to be treated, (for the purpose of this illustration considered as a natural gas of relatively high calorific value containing in addition'to methane smaller amounts of higher hydrocarbons, including ethane, propane and butane) is drawn from a main 10 and passed through a meter 12 for the purpose of determining the volume rate of flow. From meter 12 the gas is passed through a compressor 14 wherein it is compressed to a suitable, normally relatively high pressure. After being thus compressed the gas may be conducted through an absorber or equivalent apparatus 16 for the purpose of separating liquefiable constituents such as natural contain only very small amounts of natural gas gasoline hydrocarbons, or if their removal is not desired, it may be by-passed around the absorber 16 through a valved line 18. The measured portion of gas which is to be treated is next conducted through a valve 20 into a manifold 22 and any part of the gas which it is not desired to treat is passed back through a valve 24 to the main line 10. A part, or all, of the gas delivered to the manifold 22 is passed into a valved line 26 and thence either through the tubes or coils of a main heat interchanger 28 and an auxiliary heat interchanger 30, or around the interchanger through a. valved by-pass 32. From the delivery side of interchanger 30 the gas is delivered through a continuation of pipe 26 to an air-gas mixing nozzle 34 mounted in an inlet-chamber 36 of a high pressure oxidation vessel 38. A measured volume of air (or oxygen or other gaseous oxidizing medium), under a pressure slightly higher than that on the gas, is intimately admixed with the gas at 34 by jetting the air from a yalve controlled air supply line 40. Air is delivered to the line 40 either through

interchangers

28 and 30.

or around the interchan'gers through a by-pass 42. The air is conducted to the interchangers by a pipe 44 which in turn receives a continuous throat mixers and the like if desired) is mounted at the inlet 36 of vessel 38 and functions to effect thorough intermingling of the hydrocarbon and the air or other' oxidizing medium which make up the reaction mixture. In the reaction zone of the vessel 38 the oxygen of the reaction mixture enters into chemical combination with one or more of the hydrocarbon constituents of the natural gas under conditions of temperature, pressure and the like which experience has shown to be best suited for effecting homogeneous partial oxidation to form intermediate hydrocarbon-oxygen compounds (in preference to complete oxidation products of the carbon-oxygen and hydrogen-oxygen type). The hot prodnets of the reaction which takes place in vessel 38 exit from the vessel, still under pressure, through a. pipe 52 and are passed directly into and through a hot gas chamber 54 of the interchanger 28. Chamber 54 lies between flue sheets 56 and surrounds the flues of the interchanger.

changers 38 and 30 into separate passages to air and gas passing to the reaction vessel.

From chamber 54 the products of reaction pass by a line 60 into a condenser 62 and from thence into an absorber 64, wherein any intermediate oxidation products formed during the treatment in the reaction chamber are liquefied and separated from the gaseous residue. Refrigeration is normally used in cooling the condenser 62 and absorber 64. The treated gaseous residue is passed into a pipe 66 from which it is either recycled through manifold 22 for treatment in a similar manner with a fresh portion of oxidizing gas in the same orv in another reaction vessel 38, or else such gaseous residue may be conducted through a valve 68 into a manifold 70 and thence back to the gas distributing main 10 through a valve 72. If desired the gaseous residue of the first stage of the treatment may be conducted by extension '74 of manifold 70 into and through another set of

apparatus units

38, 62 and 84, (not shown) the treatment in such second stage and in each subsequent stage being preferably carried out after admixture of relatively smaller volumes of oxygen-bearing gas with the hydrocarbon to be treated.

The preferred design of reaction vessel (see Fig.

' 2) embodies a pressure-resistant, air-tight casing 76 having its interior divided by heat-conductant partitions (comprising flue sheets 78 and flues or tubes 80) into relatively gas-tight, pressure-resistant passages for the reaction mixture and products of the reaction, and into a chamber 82 surrounding the tubes in which a fluid cooling or temperature control medium is normally circulated. The oxidation reactions take place in tubes 80, and communicating with these tubes at opposite ends thereof are inlet and outlet chambers 36 and 84 for conducting the reaction mixture and products of reaction, respectively, to and within the contemplation of the invention.

away from the reaction zone. A partition 86 extends longitudinally between the flue sheets '78 and divides chamber 82 into two sections 87 and 88 (see Fig. 1). ing media are circulated at a controlled rate and under a controlled pressure through the

sections

87 and 88 throughout the period of the treatment for the purpose of maintaining careful and Liquid or gaseous heat absorb-' accurate control of temperatures in the reaction tubes 80 by a rapid removal (at a controlled rate) of excess heat liberated by the exothermic reactions in the tubes 80 in the form of sensible heat in the fluid circulating medium. The fluid temperature control medium which is maintained in circulation in'section 87 of chamber 82 throughout the period. of the reaction enters chamber 82 through a valved connection 90, and leaves through a valved connection 92. Similarly the fluidflwhich is maintained in circulation in section 88 enters this section through a line 91 and leaves through a line 93.

Lines

90, 91, 92 and 93 have been shown (Fig. 1) in closed circuit with a' hot fluid chamber 94 (formed between flue sheets 56 and surrounding the flues or coils of the heat exchanger 30), as well as with pumps 96. The closed circuit thus provided is utilized for cooling and circulating at a controlled rate any fluid which may be employed as a-temperature control medium in vessel 38.

A valved pipe connection 98 is provided between .the pipe and the pipe 26 on the inlet side of the valve 100 therein. Likewise a valved connection 102 connects pipe 92 with the discharge side of valve 100. By virtue of these connections gas on its way to the reaction vessel may be used as the temperature control medium for circulatic'n around the reaction zones of tubes 80, if desired. A pipe 104 similarly connects line 91 with pipe 40 and may be used to conduct at from pipe 40 into the top of section 88; while a pipe 106 is likewise provided to conduct air, back from line 93 into pipe 40 on the discharge side of the valve 108. The purpose of partition 86 is similar to that of partition 58 in the

interchangers

28 and 30, namely to prevent the intermingling of the hydrocarbon and the oxygen-supplying components, respectively, of the reaction mixture during periods in which such components are employed as temperature controlling media in sections 8'! and 88 of the reaction vessel. The small or section 88 of chamber 82 is normally used as an air circulating chamber because of the fact that the reaction mixture normally contains less air than gas.

The partial oxidation reactions leading to formation of aldehydes and alcohols and similar intermediate oxidation products in accordance with the present process are believed to be chiefly homogeneous in character, at least under the conditions of operation outlined herein, and accordingly the use in the reaction zone of known metal and metal compound contact catalysts such as platinum or vanadium oxide is preferably avoid- -ed. However, it is not desired to limit the present process to any particular theory as to the homogeneous character of the reaction or otherwise, and the employment of gas or vapor phase catalysts andthe principles of auto-catalysis are If the process is not one of homogeneous oxidation it exhibits most of the characteristics of homogeneous oxidation reactions, and it has been noticed that in general the presence of any of the well known solid contact catalysts in the reaction zone will decrease the yield of intermediate products as compared with the yields obtained in the absence of such catalysts. For this reason the expression homogeneous partial oxidation reaction" has been used in the description and claims as, a generic term to deflne a reaction which takes place with substantially equal velocity (and in the absence of contact catalysts) throughout all sections of the reaction zone; as

oxidation of hydrocarbons, are considered to function primarily to activate surface or heterogeneous reactions, the principal (and sometimes the only recoverable) products of which are complete combustion products, namely carbon oxides and water. For this reason and in order to avoid any difficulties in temperature control which would result from the development of hot spots (that is local highly energized reaction centers) in the reaction tube, each tube or flue 80 is preferably constructed of, or lined with, a relatively highly heat conductant non-catalyst material such as aluminum, while a cooling fluid of accurately controlled temperature is rapidly circulated at a controlled rate therearound. Moreover each of the tubes 80 of the reaction vessel is preferably of small cross section and has a relatively large heat transfer surface per unit of cross sectional area. Thus even in. a commercial size apparatus the diameter of the reaction tubes is normally limited to a maximum of one inch, and in cases where it is necessary to employ reaction tubes of larger diameter than one inch,

such larger tubes are normally filled with a granulated inert heat conductant material such as aluminum tumings.

The temperature of initial combustion of a hydrocarbon such as propane is higher in the presence of aluminum than it is in the presence of such metals as platinum and copper. As distinguished from most metals, however, aluminum is 'not a catalyst for complete combustion of hydrocarbons and consequently the use of alumi-j num favors a high yield of aldehydes obtained by partial oxidation of hydrocarbons by prevent ing or reducing the substantial loss of hydrocarbons by heterogeneous reactions. Stainless steel, iron and prex glass have been satisfactorily substituted for aluminum in constructing the reaction tubes or their linings. Materials of this type are known to be substantially inert so far as their power to activate surface oxidation reactions is concerned. The use of-a flller such as aluminum turnings in the reaction tube serves to inhibit; or to at least partially inhibit, the formation of of hot spots, probably because the high thermal conductivity of this material serves to rapidly dissipate or transfer any excess heat developed in the reaction zone, to the fluid cooling medium surrounding the tubes. It is recognized that an oxide film may form on the surface of aluminum thus used, but if such is the casethe results show that the effect of the oxide on the process is substantially the same asthat of the metal.

In starting the operation of the process the reaction vessel is brought up to the necessary reaction temperature either by some external heating means, such as electrical resistance heating elements (not shown). or by combustion of a small part of the hydrocarbon which is to be 1 reaction vessel.

treated. When very low concentrations of oxygen areusedinmakingupthereactionmixtureit may sometimes be found advantageous or necessary to use small amoimts' of contact catalysts in the reaction chamber in order, by reason of the complete combustion reaction thereby promoted, to make'the reaction self-sustaining in the matter of maintenance of the necessary reaction temperature. Usually however, theuse of such contact catalysts is neither necesary nor desirable.

While the initial stage of reaction treatment is preferably homogeneousjincharacter, one or more subsequent stages of treatment may be carried on in the presence of contact catalysts. For example, where the reaction mixture formed in the initial homogeneous reaction contains acids,

aldehydes', alcohols and hydrogen, the passage of this mixture in a subsequent reaction stage over a catalyst such as silver or platinum will cause the hydrogenation of aldehydes and acids to alcohols, thus giving a simpler and more de-' sirable final product. Obviously other catalysts can be employed with a similar object in view.

Following is a brief description of an application of the present process to the partial oxidation of commercial propane:-A measured volume of this gas is vaporized under a superatmospheric pressure of about 400 lbs. per square inch and is admixed with about 30% of its volume of air, under a slightly higher pressure, to

make up the reaction mixture. The gas and air components of the reaction mixture are separately preheated to about 250Zi00 CL, and the reaction mixture is formed by thorough intermingling of its components just at the entrance of the The reaction mixture thus formed is passed into and through a number of open aluminum lined steel reaction tubes of about one fourth inch diameter, the temperature of such tubes, or rather of the fused nitrate bath in which the tubes are immersed, being maintained uniform at about 350 C. It will be understood that the average temperature inside the open reaction tube is diflicult to measure but it may be at least 25 C. higher than the temperature of the surrounding bath. The rate of passage of such that the time of sojourn of any unit volume thereof in the reaction tube is ordinarily less than one second. It is desirable to hold the mixture of hydrocarbons and oxygen-supplying gas not higher than 50 C. above the temperature at which the partial oxidation reaction is initiated in such mixture. On leaving the reaction zone the prod-.

ucts of the reaction are immediately and rapidly cooled and part of their sensible heat is recovered by passing them through a heat interchanger in heat transferring relationship with the gas and air passing to the reaction vessel. Any condensible liquid hydrocarbon-oxygen compounds formed during the course of the reaction are separated from the gaseous residue in suitable condensing and absorber equipment. The entire operation, including the reaction and separation of the gaseous and liqueflable products of the reaction, is preferably carried out under the specified pressure. Among the products of the treatment are water, small amounts of substances containing active oxygen such as organic peroxides and materials derived from organic peroxides, methanol, acetaldehyde, formaldehyde andother alcohols, aldehydes, ketones, acetals and acids.

The liquid reaction product obtained by partial the reaction mixture through the tubes is I oxidation of commercial propane in accordance with the treatment described consists largely of compounds the molecules of which all contain less than three carbon atoms. However there may also be present in this product small amounts of compounds the molecules of which contain three or more carbon atoms. In general the use of reaction mixtures of low initial oxygen concentration and the maintenance of high pressures, high rates of flow and low temperatures in the reaction zone are all conducive to production of a liquid product of. high molecular weight and low water content. The average molecular weight of a liquid product obtained by partial oxidation of propane in accordance with the treatment above specified is from to 35 as compared with 18 for water. The gaseous residue of the treatment contains no uncombined oxygen (if the reaction is properly carried out) and may be used as a fuel or may be admixed with another portion of air and subjected to a similar treatment in a second stage of partial oxidation. Complete utilization of the free oxygen contained in the original reaction mixture used in each stage of the treatment is preferred because, for one reason, it is known that both the liquid and gaseous products of the reaction are strongly corrosive in case there is free oxygen associated therewith.

It should be mentioned that in certain cases it may be desirable to separate from the gaseous reaction residue, its content of unacted upon propane. This can readily be accomplished by proper cooling of the gaseous residue preferably after the hydrocarbon-oxygen products have been removed.

In treating a natural gas containing large proportions of methane under the conditions of pressure and the like just specified, it has been found bestto employ a reaction temperature in the neighborhood of 425-450 C. In treating butane, on the other hand, the reaction temperature may be dropped to about 325 C. The optimum reaction temperature for treating other hydrocarbons of the paraffin series under the conditions of pressure and the like stated in the example may be interpolated from the values given (see Fig. 3). The most advantageous temperature range at which to carry out the partial oxidation of propane is fairly wide (depending upon pressure, size of reaction vessel, and other conditions under which the reaction takes place). This range includes temperatures of 300 C. to about 450 C. A corresponding temperature range has been 'aund for treating the other hydrocarbons of this coup, as the foregoing data indicates. The optimum treating temperature increases proportionately as the number of carbon atoms in the hydrocarbon molecule decreases, and vice versa. The most desirable temperature is usually one approaching closely the temperature of initial reaction of the reaction mixture at the pressure employed, for the reason that if the temperature is carried much above thetemperature at which reaction commences, side reactions occur, the ultimate products of which are carbon oxides and water. i

The minimum temperature below which no partial oxidation reaction takes place is in general considerably higher than the temperature at which complete combustion reactions are activated in the presence of such heterogeneous reaction catalysts as platinum or copper.

It is a feature of this invention that the process described is very sensitive to changes of temperature. Thus, as the process is ordinarily conthe temperature of initial reaction, the increase in reaction velocity is so great that a temperature difference of less than 3 C. often separates the condition of the system in which there is small, barely detectable reaction, and the condition in which the reaction mixture loses all of its free oxygen with the formation of the intermediate 4 compounds previously mentioned. (See Fig. 4.)

It has been found to be difficult to measure the temperature of initial reaction, but it is not difficult to obtain an accurate measurement of the temperature of half reaction, which is the temperature at which half of the oxygen of the initial reaction mixture has entered into combination reactions. This temperature has been found to depend upon the following conditionsz-nature of the hydrocarbon or composition of the hydrocarbon gas if a mixture of hydrocarbon is being treated, initial concentration of air or oxygen used, rate of flow thru reaction zone, diameter and length of reaction cylinder, i. e., design of the apparatus employed, the presence of certain substances which can act as detonators, catalysts or inhibitors to the reaction, and the pressure employed.

Thus it has been found that the temperature of half reaction of 70% propane% air mixtures, in the absence of any known catalyst, detonator or inhibitor, all of the experiments being conducted in the same apparatus and the thruput of reaction mixture being held the same for each determination, is lowered by an increase in pres sure substantially in accordance wth the following equation:--

*(T being expressed in degrees Kelvin and P in' pounds per square inch).

In treating paraffin hydrocarbons of the ethane to octane range by the present process, pressures ranging from 100 lbs. 1750.1bs. per square inch have been employed. Apparently the most satisfactory and practicable pressures are those in the neighborhood of 300 to 500 lbs. per square inch. The efliciency of the treatment, or in other words, the percentage of the oxygen content of the initial reaction mixture which is obtained in the form of liquid organic hydrocarbon-oxygen products, increases with an increase in pressure up to about 500 lbs. per square inch. The increase is not so marked at pressures above this point. Thus the liquid product obtained by subjecting commercial propane to partal oxidation at atmospheric pressure consists chiefly of water (as much as 90%) and small amounts of formaldehyde; whereas the treatment of commercial propane at 400 lbs. per square inch in accordance with the example stated above normally yields a product containing less than 30% water and more than 70% of liquid hydrocarbon-oxygen products. In other words an increase in pressure from atmospheric to 400 lbs. per square inch, with a corresponding drop in reaction temperatures, results in a corresponding increase in. the proportion of oxygen content of the initial reaction mixture which is converted into hydrocarbon-oxygen compounds as distinguished from products of complete combustion. As the presure under which the reaction is carried out increases the proportion of the initial per square inch to.

continue to increase with an increase in pressure.

If the rate of flow and composition of the reaction mixture is held constant the acidity of the liquid product also increases with an increase in pressure. In treatingpropane under pressures between 300 and 400 lbs. per square inch the reaction is unnoticeable at temperatures below 280 C. However in accord with the equation shown above the reaction is suddenly completed within the range of 300 to 400 C. (See Fig. 5.)

In the oxidation of propane temperatures above about 400 to 440 C., are unnecessarily high and result in complete oxidation reactions and thermal decomposition of at least part of the intermediate oxidation products formed. The optimum reaction temperature for propane under such pressures andin the absence of. a catalyst appears to be about 350 C. The same may be said for other hydrocarbons of the parailin series, except that the optimum temperature is displaced upwardly or downwardly depending on the decrease or increase, respectively, in the number of carbon.

' atoms in the hydrocarbon molecule.

The temperature of initial reactionofa hydrocarbon-air mixture increases as the oxygen concentration of the reaction mixture increases. The most satisfactory products and the most efficient conversion of oxygen to product usually occurs when using a reaction mixture of low initial'oxygen concentration, i. e., below 50% air by volume. However reaction mixtures having a much higher initial oxygen concentration can be satisfactorily oxidized if it is practicable to use sufficiently small sized reaction tubes. It has been observed that the initial reaction temperature of a hydrocarbon-pure-oxygen mixture is lower than that of a hydrocarbon-air mixture of thesame oxygen concentration. In other words for any given oxygen concentration the reaction takes place at a lower temperature when pure oxygen is substituted for air in making up the reaction mixture. In treating a propane-pureoxygen mixture the temperature of half reaction was found to increase with an increase in the initial oxygen concentration up to a temperature of 342.5 C. at an oxygen concentration of 5%. With increase of oxygen concentration above 5% the temperature of half reaction remains con-. stant. The lowest temperature at which any oxidation with air took place under similar con ditions of pressure and the like was 325 C., whereas with oxygen it was below 300 C. The amount of initial oxygen in the reaction mixture which is wasted by combination to fonn oxides of carbon and water increases as the temperature at which the reaction is conducted increases.

The temperature of half reaction of a hydrocarbon oxygen mixture containing two or more hydrocarbons, one of which is less readily converted than the other by the process into intermediate oxidation products, increases as the proportion of such less readily oxidizable hydrocarbon in the reaction mixture increases. Thus it was found that the temperature of half reaction of a reaction mixture comprising 49.7% propane, 21% methane and 29.3% air was 353.5 0. when treated in a 1 i. (1. steel reaction tube 11 feet long under a pressure of 750 pounds/sq. in,

with a slow rate of flow, namely 7.76 cu. ft./hour. The temperature of half reaction of a propaneair mixture containing 70.6% propane was 345.5 0., under similar reaction conditions. The liquid oxidation product of the propane-air mixture was of slightly higher molecular weight, andthe C0 content of the gaseous residuewas slightly lower than the corresponding products of treatment of the propane-methane-air mixture. It appears,

therefore, that the methane component. of the propane-methane-air mixture acts merely as a diluent, being comparable with the nitrogen of the air used in this respect.

It has been found that at any given pressure and temperature the molecular weight of the liquid hydrocarbon-oxygen product of the treatment of an original hydrocarbon-air mixture decreases with increase of initial oxygen concentration. For hydrocarbon-air mixtures having an' initial oxygen concentration much above 10% it has been found that the value of the liquid products drops of! rapidly with further increase in initial oxygen concentration. The use of hydrocarbon-pure oxygen mixtures in place of hydrocarbon-air mixtures of equal oxygen content results in slightly better yield of higher molecular weight products. The liquid product obtained by treating a propane-pure-oxygen mixture under substantially the conditions of pressure and the'like specified above had a water content of about 15% and a molecular weight of about 33. The liquid product obtained by treating a propane-air reaction mixture of corresponding oxygen concentration under the same conditions contained about 30% water and had a molecular weight of 29. When using hydrocarbon-pureoxygen mixtures the eiliciency of oxygen conversion of the process decreases less rapidly with an increase of oxygen concentration than when using hydrocarbon-air mixture; an efllciencyof as high 'as 66% conversion of all initial oxygen to hydrocarbon-oxygen product having been obtained.

Several runs with a commercial propane-air mixture under uniform conditions of pressure and oxygen concentration have shown a gradual increase in reaction temperature over a range of about 40 C. with an increase in rate of flow from 6 to 36 cubic feet per hour. Thus a straight line relationship exists between the temperature of half-reaction and therate of flow of the reaction mixture through the reaction zone, at least in reaction tubes of small cross section. The yield of product increases as the rate of flow increases. The results of a series of runs made in a inch reaction "tube twelve feet long with a propane-air mixture containing 30% air at 750 lbs. per square inch pressure, to determine the effects of varying the rate of now on the character of the product, indicatedthat the acidity of the liquid product increased with an increase in rate of flow up to about 16 cu. ft. per hour and then decreased with a further increase in flow, thus showing a maximum acidity with a turbulent flow rate of 16 cunft. per hour. The results of other runs have shown that with constant pressure and rate of flow the acidity of the liquid product ofthe treatment decreases as homogeneous character of these partial oxidation reactions, at least so far as treatment of the low boiling paraflin hydrocarbon is concerned, satisfactory temperature control appears to be best insured by the use either of larger sized reaction tubes filled with granulated catalytically inert material or of open unobstructed tubes of small, almost capillary, size, preferably constructwas found to be the initial reaction temperature for a propane-air mixture containing 30% air passed at a rate of 4 cu. ft. per hr. under 750 lbs. per square inch pressure through a 1; inch inside diameter reaction tube 12 ft. long, whereas the corresponding initial reaction temperature of the same mixture in a 4 inch inside diameter tube of the same material under like conditions was 307 C.

The process of the invention has particular utility in producing formaldehyde, methanol and acetaldehyde from paraflln hydrocarbons of the ethane to octane range. It will be understood, however, that the invention is not limited to the production of any specific hydrocarbon-oxygen compound or to the partial oxidation treatment of any specific type of hydrocarbon. Thus the process has been applied to the treatment of methane and also to the treatment of unsaturated hydrocarbons, including ethylene and other oleflns.

The invention having been thus described, what is claimed as new is:

1. The process of producing hydrocarbon-oxygen compounds comprising heating a mixture containing a fluid aliphatic hydrocarbon and-less than 10% by volume of free oxygen in theform of an oxidizing fluid at superatmospheric 'prese sure above per sq. in., anda temperature within the range of from 200 to 500 C., in a narrow, unobstructed reaction zone, thereby effecting a homogeneous partial oxidation reaction and the production of a fluid reaction mixture containing the said hydrocarbon-oxygen com pounds and hydrogen, and reacting the fluid reaction mixture containing the hydrocarbon-oxygen compounds while contacting it with a reducing catalyst adapted to convert to alcohols the aldehydes and acids present in the said mixture of hydrocarbon-oxygen compounds.

2. The process of producing intermediate hydrocarbon-oxygen compounds comprising reactin: a mixture containing an aliphatic hydrocarbon with not more than 10% by volume of oxygen in the form of an oxygen-supplying gas, within an unobstructed reaction zone of narrow transverse section free from solid contact catalysts and maintained at a temperature within the range of 200 to 500 0., and under a pressure within the range from 200 to 1750 poundsper square inch and passing. the said reaction mixture through the reaction zone at such rate that it is exposed to the high temperature there- 3. The process of producing intermediate hydrocarbon-oxidation products which comprises reacting a gaseous aliphatic hydrocarbon with less than one-tenth of its volume of free oxygen at a temperature between 200 and 500 0., and at a pressure above 100p0unds per square inch, within an unobstructed aluminum-lined reaction zone, and quickly removing the resultant reaction products from the said zone after exposure to the high temperature therein for a period of not more than one second.

4. The process of producing intermediate hydrocarbon-oxygen products comprising rapidly flowing an intimate mixture of a gaseous aliphatic hydrocarbon and oxygen through an elongated unobstructed reaction zone of less than one inch transverse thickness while out of contact with any solid contact catalyst, the said zone being maintained at a temperature in the range of 200 to 500 C., and at a corresponding superatmospheric pressure above 100 pounds per square inch, adapted to initiate and maintain homogeneous partial oxidation reactions almost exclusively, maintaining a substantially uniform temperature within the reaction zone, and rapidly dissipating any excess heat developed therein.

5. The process of producing intermediate hydrocarbon-oxidation products comprising quickly reacting a fluid aliphatic hydrocarbon with not more than 10% of its volume of oxygen in the form of an oxygen-supplying gas at a pressure within the range from 200 to 1750 pounds persquare inch and at a corresponding temperature in the range of 200 to 500 C. but which is not more than 50 (7., above the initial reaction temperature of the said mixture of hydrocarbon and oxygen-supplying gas.

6. The process 01' producing intermediate hydrocarbon-oxidation products comprising separately preheating a gaseous aliphatic hydrocarbon and an oxygen-supplying gas, intimately mixing the said preheated fluids and flowing the mixture in a thin stream through unobstructed reaction zone maintained at a temperature within the range of 200 to 500 C., and under superatmospheric pressure, the said reaction zone being free jrom solid contact catalysts and being immersed in a heat-transferring bath maintained at a temperature approximately that of the reacting mixture, thereby inhibiting heterogeneous oxidation reactions and promoting homogeneous partial oxidation reactions, the hydrocarbon and oxygen respectively being preheated to a temperature within 100 C. of the temperature maintained in the said reaction zone.

7. In the manufacture of hydrocarbon oxygen compounds the steps comprising passing a reaction mixture containing propane and oxygen in the proportions of substantially 10 to 1 by vollume through a reaction zone maintained at a temperature of 325 to 400 C. and under a pressure exceeding 100 lbs. per square inch, and from which solid contact catalysts for oxidation reactions are excluded.

8. In the manufacture of hydrocarbon-oxygen compounds, the steps comprising treating a hydrocarbon body containing propane, admixed with less than 50% of its volume of air, to homogeneous partial oxidation under a pressure ranging from 300 to 500 lb. per square inch and at a temperature of about 350 0., the period of exposure oi the hydrocarbon-air mixture to the said temperature being less than one second.

9. In the manufacture of hydrocarbon-omen compounds the steps comprising passing a reaction. mixture containing an aliphatic hydrocarbon having less than 8-carbon atoms in its molecule and less than 50% of its volume of air, in a plurality o1 finely divided streams each less than one inch in cross section, through a reaction zone from which solid contact catalysts are excluded and which is maintained at a temperature ranging irom'200 to 500 C. and under a pressure exceeding 300 lbs. per square inch.

10. A method of converting an aliphatic hydrocarbon having a higher molecular weight than methane into intermediate oxidation products,

which comprises treating the said hydrocarbon in a small unobstructed reaction zone with less than .ten'per cent of its volume of oxygen while continuously maintaining the mixture under a superatmospheric pressure within the range of from 200 to 1750 pounds per square inch and at a temperature within the range oi'irom 200 to 11. The method of selectively converting the propane content of a hydrocarbon mixture containing methane and propane into an intermediate oxidation product comprising, treating said mixture to partial oxidation with oxygen -at a temperature of about 350 C. and under a pres-.

sure exceeding 100 lbs. per square inch in the absence of a solid contact catalyst for oxidation reactions.

12. The process of producing intermediate hydrocarbon-oxidation compounds which comprises forming a mixture of a fluid aliphatic hydrocarbon and an oxygen-supplying gas, and flowing the said mixture into and through an elongated unobstructed reactionzone of between 1* inch and one inch in transverse thickness, while maintaining thereon a pressure of over 100 pounds per square inch, the said reaction zone being maintained at a temperature within the range of 200 to 500 C., and separately preheating the hydrocarbon and the oxygen-supplying gas to a temperature within 100 C. of the temperature maintained in the said reaction zone prior to intermixture thereof.

13. The process of producing hydrocarbon-ox- Lidation products which comprises subjecting a mixture or an oxygen-supplying gas and an aliphatic hydrocarbon having not more than 8 carbon atoms in its molecule to a pressureof from 200 to 1750 pounds per square inch and to a temperature of from 200 to 500 C. in the absence of solid contact catalysts, thereby initiating and maintaining a homogeneous gas phase par!- tial oxidation reaction and producing the said hydrocarbon-oxidation products, and recovering the latter.

STEPHEN P. BURKE.

CHARLES F. FRYIJNG.