CH489449A - Process for the oxidation of saturated hydrocarbons to alcohols and ketones - Google Patents

Description

  

  Process for the oxidation of saturated hydrocarbons to alcohols and ketones The present invention relates to a process for the oxidation of a saturated hydrocarbon containing 5 to 8 carbon atoms per molecule to the corresponding alcohol and ketone. in the liquid phase, by means of an oxidizing gas containing molecular oxygen introduced into the liquid phase, in the presence of a boron compound.

         characterized in that one operates in the presence of compounds providing sulphate ions SO4 It is known that the oxidation of saturated hydrocarbons, linear or cyclic. in liquid phase. in the presence of a boric acid (eg ortho-. meta- or pyro-boric acid). boric anhydride or boric ester. or an equivalent compound of boron. provides boric esters of alcohols corresponding to said hydrocarbons.



  Oxygen is usually employed at a concentration of 1 to 25 0'n mixed with an inert gas such as nitrogen.



  For example. the oxidation of cyclohexane. in these conditions. provides cyclohexyl borate. Other oxidizable hydrocarbons are those which contain 5 to 8 carbon atoms per molecule. for example hexane. heptane. octane, isooctane. cycloheptane. cyclooctane. methylcyclohexane and dimethylcyclohexanes (ortho-, meta- or para-).



  The oxidation temperature is usually between <B> 100 </B> and 220 ° C., preferably between 1-t0 and 190-C. the pressure being chosen sufficient to maintain a liquid phase. for example between 1 and 40 atmo spheres.



  It is also known that by hydrolysis of the reaction product. before or after separation of part or all of the unconverted hydrocarbon, boric acid is collected either directly in the solid state or in aqueous solution which can be subjected to crystallization. as well as an organic phase containing the desired alcohol. usually accompanied by a minor proportion of corresponding ketone.



  As hydrolysis agent, for example water or mother liquors from the crystallization of boric acid are used. The amount of water used is at least equal to the stochiometry of the hydrolysis reaction; generally 0.1 to 2 parts are used; by volume of aqueous phase for a part by volume of liquid effluent from the oxidation zone. and the operation is usually carried out between 20 and 170 ° C. approximately.



  Unprocessed hydrocarbon can be recycled. The solid boric acid recovered can be reused in a new oxidation operation. preferably after dehydration.



  The present process results in increased yields of allcohols and ketones and allows the use of commercial reagents and not of low cost pure reagents.



  According to the method of the invention. the operation is therefore carried out in the presence of compounds providing sulfate ions.



  This process is based on the surprising discovery that the above reaction of oxidation of hydrocarbons in the presence of boric acid can be carried out in substantially increased yield when the reaction mixture contains. in controlled amounts, sulfate ions. for example soluble or insoluble sulfates, preferably of alkali or alkaline earth metals.



  This fact is especially surprising given that such salts have not proved so far. possess catalytic properties vis-à-vis oxidation.



  Nevertheless, it was found that a reaction mixture containing <B> (the </B> 100 to 5000 (preferably 200 to <B> 1000) </B> parts per million (expressed as weight of SO., Per relative to the weight of ineta-boric acid) sulphates preferably alkaline or alkaline-earth, such due for example to the sulphates of calcium, barium, sodium or potassium, made it possible to obtain better results, as regards the oxidation of hydrocarbons to the corresponding alcohols,

   that the same reaction mixture not containing said sulfates (or containing them in amounts different from those given above).



  Examples 1 to 3 below illustrate the invention, Examples 1A, 1B and 1C being given by way of comparison but not coming within the scope of the invention.



       Example <I> 1 </I> One continuously oxidizes. in a reactor maintained at 170 ° C. and under a pressure of 10.5 kg / cm 2 of the liquid cyclohexane introduced into the reactor at a rate of 48 liters per hour.



  The reactor is supplied with a gas stream composed essentially of nitrogen (94% by volume) and oxygen (6% by volume). the specific flow rate of the latter gas corresponding to 9501 / h of pure oxygen.



  In addition. metaboric acid containing 300 ppm (parts per million) of alkaline earth sulphates counted as SO 3 is introduced at a rate of 2 kg / h.



  After hydrolysis of the reactor effluent and separation of the unconverted cyclohexane, a mixture of cyclohexanol + cyclohexanone is obtained with a molar yield of these two compounds equal to 92% and a degree of conversion of cyclohexane equal to 12%.



  Examples! A, I B and! C Example 1 is repeated using a metaboric acid containing Oppm (Example 1A). 50 ppm (Example I B) and 7600 ppm (Example 1C) of alkaline earth sulphates counted as SO3.



  All the other 'conditions remaining identical to those of Example 1 (temperatures. Flow rates, etc.), a cyclohexanol - + - cyclohexanone mixture is obtained with the following yields (R) and degrees of conversion (C).
EMI0002.0008
  
    Example <SEP> R <SEP> 0; <SEP> 0 <SEP> C <SEP> 0! 0
<tb> 1 <SEP> A <SEP> 89.8 <SEP> 10.?
<tb> 1 <SEP> B <SEP> 90.5 <SEP> <B><I>11,5</I> </B>
<tb> 1 <SEP> C <SEP> <B> 89.8 <SEP> 11.0 </B> We see that the results are noticeably worse than in example 1.



  Examples 2, 3 and 3bis Example 1 is repeated using a metaboric acid containing respectively 100 and 1000 ppm of alkaline earth sulphates counted as SO 3. In the ibis example, pure metaboric acid was used and 200 ppm sodium sulfate was separately introduced.



  All the other conditions remain identical to those of Example 1, the following results are obtained
EMI0002.0013
  
    Example <SEP> R <SEP> <B> 0/0 </B> <SEP> C <SEP> 0/0
<tb> 2 <SEP> 91.85 <SEP> 11.90
<tb> 3 <SEP> 91.90 <SEP> <B> 11.95 </B>
<tb> ibis <SEP> 92.10 <SEP> 11.80

 

Claims (1)

CLAIM A process for the oxidation of a saturated hydrocarbon containing 5 to 8 carbon atoms per molecule in the corresponding alcohol and ketone. in liquid phase. by means of an oxidizing gas containing molecular oxygen introduced into the liquid phase. in the presence of a boron compound. characterized in that one operates in the presence of compounds providing sulfate ions <B> sol--. </B> SUB-CLAIMS 1. Process according to claim 1, in which 100 to 5000 parts expressed by weight of SO., Are used. of compounds providing sulfate ions, per million parts by weight of boric acid. 2. Method according to claim in which 200 to 1000 parts are used, expressed by weight of SO 3, of compounds providing sulfate ions. per million <B> </B> parts by weight of boric acid. 3. Method according to claim wherein. alkali metal or alkaline earth metal sulphates are used.