US3838179A

US3838179A - Process for manufacturing alcohols by oxidation of saturated hydrocarbons containing from 5 to 8 carbon atoms per molecule

Info

Publication number: US3838179A
Application number: US00638719A
Authority: US
Inventors: B Cha; J Alagy; C Busson
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1966-05-25
Filing date: 1967-05-16
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24
Also published as: GB1141724A; NL6707164A; DE1618561A1; FR1497522A; FR1509367A

Abstract

THE PRESENT DISCLOSURE IS DIRECTED TO A PROCESS FOR CONVERTING SATURATED HYDROCARBON CONTAINING FROM 5 TO 8 CARBON ATOMS IN THE MOLECULE TO CORRESPONDING ALCOHOLS AND KETONES OF THE SAME NUMBER OF CARBON ATOMS WHICH COMPRISES CONTACTING SAID HYDROCARBONS IN THE LIQUID PHASE WITH AN OXIDIZING GAS BEING INTRODUCED AT A TEMCOMPOUND, SAID OXIDIZING GAS IN THE PRESENCE OF A BORON PERATURE BETWEEN ABOUT 100 TO 220*C., HYDROLYSING THE REACTION PRODUCT AND SEPARATING THE OBTAINED ALCOHOLS AND KETONES, SAID OXIDIZING GAS CONTAINING A MIXTURE OF ABOUT AIR AND A VAPOR OF THE HYDROCARBON TO BE OXIDIZED WHICH HAS BEEN PRELIMINARY PREHEATED TO A TEMPERATURE OF ABOUT 140 TO 190*C.

Description

United States latent C) PROCESS FOR MANUFACTURING ALCOHOLS BY OXIDATION OF SATURATED HYDROCARBONS CONTAINING FROM 5 TO 8 CARBON ATOMS PER MOLECULE Jacob Alagy, La Celle-Saint-Cloud, Christian Busson, Rueil-Malmaison, and Bernard Cha, Chatou, France, assignors to Institut Francais du Petrole, des Carburants 'et Lubrifiants, Rueil-Malrnaison, France N Drawing. Filed May 16, 1967, Ser. No. 638,719 Claims priority, application France, May 25, 1966,

- 62,988; Jan. 18, 1967, 91,680

Int. Cl. C07c 29/12, 45/02 US. Cl. 260-586 AB 6 Claims ABSTRACT OF THE DISCLOSURE The present disclosure is directed to a process for converting saturated hydrocarbons containing from to 8 carbon atoms in the molecule to corresponding alcohols and ketones of the same number of carbon atoms which comprises contacting said hydrocarbons in the liquid phase with an oxidizing gas in the presence of a boron compound, said oxidizing gas being introduced at a temperature between about 100 to 220 C., hydrolysing the reaction product and separating the obtained alcohols and ketones, said oxidizing gas containing a mixture of air and a vapor of the hydrocarbon to be oxidized which has been preliminary preheated to a temperature of about 140 to 190 C.

It is known that the oxidation of linear or cyclic saturated hydrocarbons, in liquid phase, in the presence of a boric acid (for example ortho-, metaor pyro-boric acid), boric anhydride, a boric ester or an equivalent boron compound, provides for boric esters of the alcohols corresponding to said hydrocarbons.

. Oxygen is usually emplyed at a concentration of 1 to 25% in admixture with an inert gas such as nitrogen.

For example, oxidizing cyclohexane, under these conditions; provides for a cyclohexy borate. The oxidizable hydrocarbons are essentially alkanes and cycloalkanes which contain from 5 to 8 carbon atoms per molecule, for example hexane, heptane, octane, isooctane, cycloheptane, cyclooctane, methylcyclohexane and dimethycyclohexanes (ortho-, meta-, para-).

The oxidation temperature is usually comprised between 100 and 220 C. preferably between 140 and 190 C., the pressure being suflicient to maintain a liquid phase, for example between 1 and 40 atmospheres.

This invention relates to a process of this kind wherein, by hydrolysis of the reaction product, before or after having separated a part or the whole of the non-converted hydrocarbon, there is recovered boric acid either directly in the solid state or an aqueous solution which may be submitted to crystallization, as well as an organic phase containing the required alcohol having the same number of carbon atoms as the oxidized hydrocarbon usually with a minor'amount of corresponding ketone.

As hydrolysis agent, there is used for example water or the mother-waters of boric acid crystallization. The amount of used water is at least the stoichiometrical amount for the hydrolysis reaction; as an average there is used from 0.1 to 2 parts by volume of aqueous phase per part by volume of liquid efiluent from the oxidation zone, and the operating temperature is usually between 20 and 170 C. approximately.

The non-converted hydrocarbon may be recycled.

The recovered solid boric acid (essentially orthoboric acid) may be used again in a new oxidation operation, preferably after dehydration, so as to be at least in part under the form of alower hydrate of boric acid.

The process results into increased yields of alcohols and ketones.

This invention also relates to several improvements to the above process, which improvements may be used alone or as various combinations.

The process of this invention consists of using an oxidizing gas containing oxygen and vapor of the hydrocarbon to be oxidized, for example as an intimate mixture of oxygen, nitrogen and vapor of the hydrocarbon to be oxidized.

Preferably this mixture must be warm, for example at a temperature of about to 220 C., when it is introduced into the reactor.

Also for preparing the mixture, it is preferred to warm the nitrogen and/or oxygen gas, for example at about -190 -'C., before admixing the same with the hydro carbon vapor.

If this is not done, there occurs the risk that the hydrocarbon be partially condensed, which results into pressure drops in the pipes and a non-selective oxidation of this hydrocarbon.

According to a preferred embodiment which further improves the process, the nitrogen-oxygen mixture is saturated only partly with vapor of hydrocarbon to be oxidized; the saturation rate is advantageously comprised between 20 and 90%, preferably between 30 and 55%. The saturation rate S, at a given temperature, is the ratio between the partial pressure p of the hydrocarbon in the oxidizing mixture and the saturating vapor pressure of the hydrocarbon p at the same temperature. The latter is given by the constants tables.

On the other hand, p, is proportional to the concentration c of the hydrocarbon in the oxidizing mixture:

where P is the total pressure (p is at most equal to p whence:

Usually the best results are obtained for gaseous mixtures of oxygen, nitrogen and hydrocarbon containing by volume 214% oxygen, 33-70% nitrogen and 28-58% hydrocarbon, provided the above conditions of saturation are respected.

It was prior known to dilute air by means of an inert gas such as the gas impoverished in oxygen resulting from a previous oxidation, so as to bring its oxygen concentration to a value comprised between about 2 and 15%.

This technique is relatively expensive in power for circulating and compressing the recycle gas. Moreover if care is not taken to reheat and saturate the recycle gas with hydrocarbon, an intense evaporation of the hydrocarbon results, in the oxidation zone, which obliges to furnish considerable amounts of heat to the oxidation reactor and causes local overheating which are detrimental to the yield and aspect of the products.

The improvement, object of this invention, and which remedies to the above defects, consists of feeding the reactor with an oxidizing gas consisting of an intimate mixture of oxygen, nitrogen and vapor of the hydrothrough one or several injectors, through a distributor or any equivalent means.

There is advantageously used, in the oxidizing mixture of this invention, a volumetric ratio of the vaporized hy- .drocarbon to the mixture oxygen nitrogen comprised between 0.5/1 and 10/1.

It is essential to introduce oxygen, nitrogen and hydrocarbon vapor into the reactor as a mixture as intimate as possible. On the contrary if there is introduced separately air on one side and hydrocarbon vapor on the other side, which possibility is outside the scope of this invention, there is not obtained the high yields of this invention.

It seems that, in the process of the invention, the hydrocarbon vapor which is presents in each gas bulb limits the speed of diffusion of oxygen towards the interface gasliquid of each bulb, which gives time to the formed molecules of alcohol and ketone to be dispersed through the liquid phase before having borne an undesired thorough oxidation.

An explanation of the observed critical values with respect to the saturation rate could be the following:

At the interface gas-liquid of each gaseous bulb considered as a micro-reactor, a complementary vaporization of hydrocarbon would take place, due to the exothermicity of the oxidation reaction. In this way, the local temperature of the liquid at the interface level remains substantially the same as the average temperature of the liquid.

Conversely if the nitrogen and the oxygen contained in the bulb are completely saturated with hydrocarbon vapor, the vaporization is no more possible. There results an excessive overheating at the interface gas-liquid of the bulb, which results into secondary reactions which are detrimental to the obtainment of good yields.

This explains why it is desirable to have hydrocarbon vapor in each gas bulb and why, however, the amount of vapor must be preferably lower than the saturation value.

It must be understood that the process which is the object of this invention, may be used together with all known and compatible processes for oxidizing saturated hydrocarbons in the presence of boron compounds. In particular, although this is less preferred, one may introduce in known manner a part of the air necessary to the process either as such or preferably after dilution by means of an inert gas, for example the recycle gas. One may also admix with the feed gas of this invention a given amount of recycle gas, although this is less preferred.

The following Examples 1-7 illustrate the process of this invention whereas Example 1A is given by way of comparison.

EXAMPLE 1 In an autoclave of stainless steel of 4 liters capacity is introduced a mixture of 1,800 grams of cyclohexane and 130 grams of meta-boric acid. The autoclave is provided with a blade stirrer and with inlet ducts for introduction of gas in the vicinity of the bottom of the apparatus. The autoclave is surmounted with a condenser and a decanter placed on the circuit of the gas evacuation in order to allow removal of water formed in the reaction. The cyclohexane which has been condensed an separated from water is returned to the reaction vessel.

The temperature is brought to 165 C. and the pressure to 12 kg./cm. as absolute pressure. The oxidizing gas consists of an intimate, previously formed mixture of air with cyclohexane vapor prior to its introduction into the reaction vessel, the ratio by volume of the cyclohexane vapor to the air being equal to 1.5, which corresponds substantially to the complete saturation of this air.

The reaction is stopped when 60 liters of oxygen have been absorbed. The reaction product is hydrolyzed by water at a temperature of 100 C., in a conventional manner.

The molar yield of cyclohexanol+cyclohexanone mixture with respect to the converted cyclohexane is equal to 89% and the conversion rate of cyclohexane attains 12.4%.

EXAMPL'E 1A The same apparatus as in Example 1 is used with the same starting amounts of cyclohexanone and metaboric acid, the same temperature and the same pressure.

EXAMPLE 2 Cyclohexane oxidation is carried out continuously in a cylindrical vertical reaction vessel of stainless steel in which the liquid phase (i.e. cyclohexane containing in suspension metaboric acid) is maintained at C., the pressure prevailing inside the reaction vessel being of 10.5 kg./cm. The respective feeding rates of cyclohexane and metaboric acid are of 50 liters per hour and 2 kg. per hour.

The bottom of the reaction vessel, of conical shape, is perforated with holes through which oxidizing gas is allowed to pass. This gas is obtained by admixing previously, air preheated to C., with cyclohexane vapor also brought to the same temperature. The mixture effected outside of the oxidation reaction vessel, contains 57% by volume of cyclohexane vapor and 43 by volume of air, which corresponds to a saturation rate of 70%.

The experiment lasts 50 hours. During this entire time the gaseous mixture is regularly injected into the reaction vessel. The analysis of the liquid outflow from the reaction vessel, after hydrolysis, shows that the molar yield of mixture cyclohexanol+cyclohexanone is equal to 92% and the conversion rate equal to 12%.

EXAMPLE 3 The experiment described in Example 2 is repeated under the same operating conditions except that air at the ambient temperature is admixed with the stream of cyclohexane, vaporized at 175 C.

All other conditions being identical to those of Example 2, it is observed that the pressure drop of the gaseous mixture between the inlet duct therefor and the reaction zone is increased; after hydrolysis, the molar yield of cyclohexanol-l-cyclohexanone is only 89% and the conversion rate equal to 10.5%.

This shows why it is preferred to prepare the oxidizing mixture by means of preheated oxygen and nitrogen.

EXAMPLE 4 Example 2 is repeated with different saturation rates of the oxidizing gas in cyclohexane vapor. The following results are obtained:

Percent Molar Conver- Saturation rate yield sion EXAMPLE 5 The same reaction vessel is used as in Example 2. The oxidation is carried out continuously at 165 C. under 10 kg./cm. The liquid cyclohexane rate is 50 liters perhour and that of boric acid is 2.2 kg./hour.

The oxidizing mixture consists of 4% oxygen, 68% nitrogen and 28% cyclohexane vapor (by volume), which corresponds to a saturation rate of about 40% of the mixture oxygen-nitrogen by means of hydrocarbon vapor.

After hydrolysis, the following results are obtained: yield of cyclohexanol+cyclohexanone mixture, 92.25%; conversion rate, 12.30%.

EXAMPLE 6 Example 5 is repeated with the same operating conditions except that the saturation rate of the oxidizing mixture oxygen-nitrogen with cyclohexane vapor is about Example 5 is repeated with the same saturation rate of the hydrocarbon vapor, however, with different hydrocarbons. The following results are obtained:

Percent Conver- Molar sion Hydrocarbon yield rate Methyleyclopentane 88. 1 12. 5 n. Hexane 89.2 12.2 Cyelooctane- 92. 1 11. 5

What is claimed is:

1. A process for converting saturated hydrocarbons containing from 5 to 8 carbon atoms in the molecules to corresponding alcohols and ketones to the same number of carbon atoms which comprises contacting said hydrocarbons in the liquid phase With an oxidizing gas in the presence of a boron compound, said oxidizing gas being introduced at a temperature between about 100 to 220 C., hydrolyzing the reaction product and separating the obtained alcohols and ketones, said oxidizing gas containing a mixture of air and a vapor of the hydrocarbon to be oxidized, said mixture containing by volume, 2-14% oxygen, 33-70% nitrogen and 2858% said hydrocarbon vapor, and said air and hydrocarbon vapor being preliminarily and separately preheated, before being admixed, to a temperature of about 140 to 190 C.

2. Process according to claim 1 wherein the saturation rate of the oxidizing gas with the vapor of the hydrocarbon to be oxidized, at the inlet of the oxidation zone, is between 20 and 3. Process according to claim 2 wherein the saturation rate of the oxidizing gas with the vapor oi hydrocarbon to be oxidized at the inlet of the oxidation zone, is between 30 and 55% 4. Process according to claim 1, wherein the hydrocarbon is cyclohexane.

5. Process according to claim 1, wherein the boron compound is boric anhydride, a boric acid or a boric ester.

6. A process for converting saturated hydrocarbons containing from 5 to 8 carbon atoms in the molecules to corresponding alcohols and ketones or the same number of carbon atoms which comprises contacting said hydrocarbons in the liquid phase With an oxidizing gas in the presence of a boron compound, said oxidizing gas being introduced at a temperature between about to 220 C., hydrolyzing the reaction product and separating the obtained alcohols and ketones, said oxidizing gas containa mixture of air and a vapor of the hydrocarbons to be oxidized, said oxidizing gas being characterized by a ratio by volume of the vaporized hydrocarbon to oxygen-l-nitrogen between 0.5 :1 and 10: 1, and said air and hydrocarbon vapor being preliminarily and separately preheated, before being admixed to a temperature of about to C.

References Cited UNITED STATES PATENTS 3,317,614 5/ 1967 Marcell 260632 CB 3,274,254 9/1966 Seddon 260-586 B 1,947,989 2/1934 Hellthaler 260586 B LEON ZITVER, Primary Examiner N. MORGANSTERN, Assistant Examiner US. Cl. X.R.

260597 'R, 617 H, 631 B, 632 CB