US2190453A

US2190453A - Oxidation of hydrocarbons

Info

Publication number: US2190453A
Application number: US108478A
Authority: US
Inventors: William H King; Clyde Q Sheely
Original assignee: SHEELY
Current assignee: SHEELY
Priority date: 1936-10-30
Filing date: 1936-10-30
Publication date: 1940-02-13
Anticipated expiration: 1957-02-13

Description

Feb. 13-, 1940. w. H. KING ET AL OXIDATION OF HYDROCARBONS Filed 001;. 30. 1936 H M m Y m .m KR m Hw A i'atented Feb. 13, 1940 UNITED STATES OXIDATION 01 HYDROOARBON William 1!. Kill, New Orleans, La., and Clyde Q. Sheely, State College, Mica; said Kin: assignor to said Shed! Application October 30, 1938, serial No. 108,478

12 Claim.

This invention relates to a new and improved process for the preparation of chemical compounds by the oxidation of aliphatic hydrocarbons and more particularly to such a process wherein the reaction products mainly comprise aliphatic alcohols, aldehydes and acids.

The higher aldehydes of the aliphatic series have considerable value as chemical compounds and a number of them have found use in industry as perfumes. The difficulties in the way of preparing such compounds, however, have kept their costs so high' as to limit their field of usefulness. An improved and simpler method of obtaining such aldehydes would make more accessible a very desirable class of products. The same condition holds in the case of a number of the higher aliphatic alcohols and acids also, for example those containing in the neighborhood of 8 to 12 carbon atoms.

It is known that aliphatic aldehydes and acids may be obtained by the incomplete oxidation of the respective hydrocarbons by means of air or oxygen under carefully controlled conditions.

Such hydrocarbons are, as a rule, relatively inert to oxidizing agents at temperatures low enough to prevent complete oxidation to carbon dioxide and water. Methods for their partial oxidation have, however," been disclosed by several investigators and the ,use of nitrogen oxides has been suggested as an aid in such a process.

. Bibb, for example, in U. S. P. 1,392,886 discloses a method in which he utilizes a gaseous catalyst comprising nitrogen oxides to convert m'ethane into formaldehyde. Likewise James has described a process in U. S. P. 2,009,663 for converting hydrocarbons to partially oxidized products, such as aldehydes and acids, by the use of various oxides, for examples oxides of nitrogen. While such methods have been described in the patent literature, it is not considered that their efiiciency in operation has been suflicient to make them entirely satisfactory.

An object of our invention is an improved method for the production of alcohols, aldehydes, and acids by the incomplete oxidation of aliphatic hydrocarbons. A further object is such a process in which carefully controlled conditions allow a high degree of efliciency in the preparation of the desired products. A still further object is a process in which the several products obtained may be separated in relatively pure form. Additional objects will be disclosed as the process is further described hereinafter.

We have found that the foregoing objects may be accomplished by the procedure that will be detailed in the following. We introduce an excess of a normally liquid hydrocarbon in the vapor phase into a heated chamber, into which vaporized nitric acid is conducted also. Preferably such nitric acid vapor will be in intimate contact with a gas containing free oxygen, usually air, and will at least approach saturation of such oxygen-containing gas. Within the reaction chamber, the mixed gases and vapors are subjected to a temperature between 250 and 500 C. While the oxidation of the hydrocarbons constitutes an exothermic reaction, the heat evolved will not be sufficient to obtain the desired temperature and external heating will be necessary. It is essential that the reaction period be kept at a relatively short time interval, and we have found 15 seconds to be the maximum allowable time. Preferably we employ a reaction period not greater than 10 seconds, in order that the oxidation may not proceed too far. The reacting materials and reaction products are removed from the heated chamber while still in the vapor phase, and are condensed by any desired method and apparatus-under such conditions and in such an atmosphere that further reaction cannot take place. 'The amount of hydrocarbon will be above the explosive limit in all cases. We have found. it desirable to use an amount of hydrocarbon in excess of 10% by volume of the gaseous reaction mixture, and preferably between and The vaporized nitric acid is present as an oxidizing agent and not in the role of a catalyst. This agent is substantially completely utilized during the reaction so that its nitrogen is present in the exit products in elemental form and not as nitrogen oxides. The nitric acid is used in an amount greater than 3% by volume of the gaseous reaction mixture. The vaporized nitric acid is introduced, preferably as a component of a mixture with the gas containing free oxygen, and we have found desirable concentrations of such mixture to have a partial pressure of nitric acid vapor between 21 and 165 mm. While the gaseous mixture in which the oxidation reaction takes place may be at atmospheric pressure, or even slightly below, we prefer to operate at a pressure somewhat above atmospheric.

It will be a desirable step in our process also to utilize the unreacted hydrocarbon resulting from the process and to recycle it to an additional similar oxidation step, whereby the advantages of the presence of an excess of hydroing material.

partially saturated with nitric acid vapor and. the mixture of ,/air and such vapor then passes through the preheater 5. The vaporized nitric acid in air and the vaporized hydrocarbon both pass into the reaction chamber 10 where they become intimately mixed and where a tempera- 'ture of 250-500 C. is maintained, whereby partial oxidation of the hydrocarbons is brought about. The vapors pass out the pipe I! into separator 12, where any tar formed in the process is separated out. The mixed vapors and gases then pass through condenser l3, where the products capable of condensation become liquefied. The liquid condensate flows into vessel 14, while a second vessel l5 receives any further condensed product not caught in chamber I, but condensed in I 6. The vessels [4 and I5 contain the liquefied unreacted hydrocarbon that has passed through the process, and alsd'condensed water and the alcohols, aldehydes and acids resulting from the oxidation process. Such alcohols, aldehydes and acids will commonly be found in th water-insoluble layer.

Specific operating conditions suitable for our process for the production of alcohols, aldehydes, and acids are shown in the following examples. These are to be considered as merely illustrative, however, and not limiting in their application.

Example 1 v A reaction mixture comprising air containing nitric acid "vapor, in which the partial pressure of the nitric acid amounted to 67.5 mm., was passed into the reaction chamber, together with the vapors from an aliphatic hydrocarbon fraction having a distillation range between 165 and 210 C. The hydrocarbon was present in an amount such that its vapor comprised about 37% of the mixture. Using a reaction temperature of 335 C. and a contact period of 3.5 seconds, the point yield of aldehydes, based on the amount of hydrocarbon burned, was 11.54%, while the yield of acids was 91.03%. The yields are cal culated as nonylic aldehyde and acid, respectively.

' Example 2 A reaction mixture comprising an air-nitric acid mixture, where the vapor pressure of the nitric acid was 152 mm., and vaporized hydrocarbon of a distillation range similar to the one used in Example 1 was passed into the reaction chamber at a temperature of 387 C., and maintained there for a reaction period of 5.2 seconds. The hydrocarbon was present in the same proportion to the air-acid mixture as in Example 1. The yields, calculated in the same manner, amounted to 12.0% aldehyde and 57.56% acid.

Example 3 A similar run using a vapor pressure of nitric acid of 67.5 mm., a hydrocarbon ratio of 37.3%,

0 a temperature of 444 0., and a reaction time of as 19.73% aldenane, decane. undecane, and dodecane. The 9.1-

cohols, aldehydes, and the acids resulting from the oxidation of these hydrocarbons are products of considerable economic value and of desirable properties, and the process described offers a novel and advantageous method of obtaining such products. The alcohols, aldehydes, and acids may be separated from the hydrocarbon condensate and from one another by the use of suitable solvents. In the case of aldehydes, for example, a saturated solution of sodium bisulfite was found desirable for extraction, the bisulflte subsequently being made alkaline and being subjected to steam distillation. The acids were desirably extracted by means of .sodium hydroxide solution. The alcohols are preferably extracted by means of phosphoric acid.

Our method, as disclosed, has been directed particularly to the oxidation of the liquid hydrocarbons by means of vaporized nitric acid in the presence of air. We have found, however, that desirable oxidation results are obtained by the use as catalysts of such compounds as tetraethyl lead, nitrobenzene, copper oleate and benzoyl peroxide, preferably in the absence of nitric acid. Such a method of operation is favorable to the production of alcohols.

While our process has been described in detail in the foregoing, it'will be understood that many variations in procedure may be employed without departing from the scope oi our invention. In the examples cited, a hydrocarbon fraction of a specific distillation range was used, but it would be ahighly desirable procedure also to start with a single aliphatic hydrocarbon, for example octane, or a, mixure of octanes.

we wish to be limited, therefore, only by the following patent claims.

We claim: I

1. The process of producing oxidation products of normally liquid aliphatic hydrocarbons, which comprises subjecting said hydrocarbons in the vapor phase to the oxidizing action of vaporized nitric acid in a gas containing free oxygen, said oxidation being carried out at a temperature between 250 and 500 C. in a reaction period not exceeding 15 seconds, removing the reacting materials and the reaction products from the chamber while still in the vapor phase, and condensing the unreacted hydrocarbon and the oxidation products under non-reacting conditions.

2. The process of producing oxidation products of normally liquid aliphatic hydrocarbons, which comprises introducing an excess of said hydrocarbons in the vapor phase, together with an oxidizing medium comprising vaporized nitric acid, into a reaction chamber at a temperature betweeen 250 and 500 C., maintaining a reaction period not exceeding 15 seconds, causing the removal of the reacting materials and thereaction products from the chamber while still in the vapor phase, and condensing the unreacted hyrocarbon and the oxidation products in a nonreacting atmosphere.

3. The process for producing partially oxidized products of normally liquid aliphatic hydrocarbons, which comprises introducing into a. reaction chamber, maintained at a temperature between 250 and500 0., an amount of said hydrocarbons in vapor state in excess of the explosive limit, together with vaporized nitric acid and an oxygen-containing ,gas, reacting said materials for a period not exceeding 15 seconds, removing the reacted materials and reaction products from the chamber while stillin the vapor phase, and condensing the unreacted hydrocarbons and the oxidation products in a non-reacting atmosphere.

4. The process of claim 3 in which the nitric acid vapor is present in the reaction chamber in an amount in excess of 3% by volume of the gaseous mixture.

5. The process of claim 3 in which the nitric acid present is substantially completely utilized in the oxidation reaction.

6. The process of claim 3 in which the condensed oxidation products resulting from the reaction are separated from the condensed hydrocarbon by means of suitable solvents.

7. The process of claim 3 in which the vapor phase oxidation process is carried out under a pressure greater than atmospheric.

8. The process of claim 3 in which the unreacted hydrocarbons resulting from the process are re-cycled to a similar additional oxidation step.

9. The process for producing aldehydes and acids by the oxidation of normally liquid aliphatic hydrocarbons, which comprises subjecting, in the vapor phase at a temperature between 250 and 500 C., hydrocarbons from the group containing between 8 and 12 carbon atoms to the oxidizin action of vaporized nitric acid, together with an oxygen-containing gas, maintaining a reaction period not exceeding 10 seconds, removing the reacting materials and reaction products from the chamber while still in the vapor phase, condensing the unreacted hydrocarbons and the aldehydes and acids in a non-reacting atmosphere, and separating said aldehydes and acids, respectively, from the liquid condensate by extraction with suitable solvents.

10. The process for producing aldehydes and acids according to claim 9, in which the'hydrocarbons oxidized are taken from the group consisting of octane, nonane, decane, undecane, and dodecane.

11. The process of producing as the oxidation products of normally liquid aliphatic hydrocarbons, the corresponding aldehydes, alcohols and organic acids, which comprises subjecting said hydrocarbons in the vapor phase to the oxidizing action of vaporized nitric acid in a gas containing free oxygen, said oxidation being carried out at a temperature between 250 and 500 ,C. in a reaction period not exceeding 15 seconds, removing from the chamber the reacting materials and the reaction products including aldehydes, alcohols and organic acids, while still in the vapor phase, and condensing the unreacted hydrocarbon and the oxidation products including said aldehydes, alcohols and organic acids under nonreacting conditions.

12. The process of producing as the oxidation products of normally liquid aliphatic hydrocarbons, the corresponding aldehydes, alcohols, and organic acids, which comprises subjecting said hydrocarbons in the vapor phase to the oxidizing action of vaporized nitric acid in a gas containing free oxygen, said hydrocarbons being present in excess of 10% by volume of the gaseous reaction mixture, said oxidation being carried out at a temperature between 250 and 500 C. in a reaction period not exceeding 15 seconds, removing from the chamber the reacted materials and the reaction products including aldehydes, alcohol, and organic acids, while still in the vapor phase and condensing the unreacted hydrocarbons and oxidation products including said aldehydes, alcohols, and organic acids under nonreacting conditions, the nitric acid present in said oxidation step being substantially completely utilized in the oxidation reaction.

WILLIAM H. KING. CLYDE Q. SHEELY.