SU443017A1 - The method of producing cyclohexene or n-heptene - Google Patents

Description

one

The invention relates to a process for the oxidative dehydrogenation of cyclic and aliphatic paraffins, in particular the preparation of cyclohexene from cyclohexane.

According to a known method, the process of dehydrogenating cyclohexane is carried out on catalysts containing metal compounds of groups of the periodic system 16, PB, IV6 and VII at 200-450 ° C, contact time 0.1-5 s, and the volume ratio of cyclohexane to oxygen is 1: 5 The maximum yield (15% cyclohexene) was obtained on a catalyst - oxidation -} - 5 wt. % cadmium oxide. The yield of the target product is low; in addition, expensive catalysts are used, which require hydrogen purging for their activation, which complicates the whole process.

In order to increase the yield of the target product, it is proposed to use a catalyst containing at least 30 wt. % of magnesium oxide, and the process is carried out at a temperature of 350-500 ° C. Preferably, dehydrogenation is carried out in the presence of water vapor.

The magnesium oxide catalyst may consist of pure magnesium oxide or of magnesium oxide mixed with oxides of metals of the second or third groups of the periodic system, and in addition, the magnesium oxide may be used in a mixture with fillers, such as bentonite clay. The contact time is 0.1-1.5 s, the volume ratio of hydrocarbon, oxygen and water vapor is 1: 0.8-4: 1-5.

The proposed method allows to achieve a high selectivity of the process (up to 90%)

increase the yield of the target product to 25%.

Example 1. Cyclohexane is dehydrated in a vertically quartz reactor with a diameter of 2, a length of 25 sul and an external electric heating in the form of a wire. In part

quartz trzbki is transverse to the glass to solve; a, on which the catalyst is attached. The reaction is carried out on oxipar arni with mechanical strength up to 20 kg / cm in the presence of air at 440 ° С, the volume ratio of hydrocarbon and oxygen is 1: 2.5 n and the contact time is 0.75 s. Conversion of cyclohexane 11%, the selectivity of the process 89%. Magnesium oxide is prepared by calcining magnesium hydroxide, obtained by precipitation pz

A 20% solution of magnesium sulphate with a 20% solution of caustic soda ppr 80 ° C.

Example 2. Under the conditions analogous to the example, the oxidizing dehydrogenation is carried out in the same catalyst in the presence of water vapor (0.01 mol per 1 mol of the feedstock).

Conversion n.klogeksaia 24% with a selectivity of 87%. Example 3. Under conditions analogous to example 2, cyclohexane on the same catalyst

dehydrated in the presence of water vapor (0.08 mol H2O per 1 mol n-SbH12) by 31%; process selectivity 74%; yield of the target product is 23%.

Example 4. On a catalyst prepared from magnesium oxide and zinc oxide (4: 1 by weight) obtained by calcining zinc hydroxide at 300 ° C for 3 hours, under conditions similar to example 2, cyclohexane reacts to 22% with selectivity 84 %

Example 5. On a catalyst consisting of 2 wt. including magnesium oxide and 1 wt. including alumina prepared by calcining aluminum hydroxide at 500 ° C for 3 hours in air flow under the conditions specified in Example 2, the conversion of cyclohexane is 30% with a selectivity of 64%.

Example 6. On a catalyst containing 2/3 of magnesium oxide and 1/3 of bentonite clay, calcined at 400 ° C for 3 hours, under conditions similar to example 2, cyclohexane is converted with a conversion of 21 and a selectivity of 87% to cyclohexene. Catalyst has

443017

significant mechanical strength (50 kg / cm2), does not lose it during operation and is not inferior in its activity to the initial magnesium oxide.

EXAMPLE 7 Oxidative dehydrogenation of n-heptane is carried out on the catalyst of example 6 under conditions analogous to example 2. Conversion of the last 48, selectivity of 90%.

Subject matter and i

Claims (2)

1. A method of producing cyclohexene or ngeptene by oxidative dehydrogenation, respectively, cycloxan or n-heptane in the presence of an oxide catalyst, characterized in that, in order to increase the yield of the target product, a catalyst containing at least 30 wt. % magnesium oxide, and the process is carried out at a temperature of 350-500 ° C. 2. SPOSob according to claim 1, characterized in that the dehydrogenation is carried out in the presence of water vapor.