SU70754A1 - A method of producing a catalyst for hydrogenation - Google Patents

Description

Hydrogenation at the site of double bonds in the presence of aldehyde and ketone groups is usually carried out with a René-type catalyst. The disadvantage of this catalyst is that selective reduction is difficult and not always possible. This method was used to obtain decyl aldehyde: from the decyl eno fraction of the flowering coriaidra, and only the double bond was reduced. But at the same time, a significant amount of alcohol was formed, and decyldehyde was obtained with an elevated refractive index and an underestimated aldehyde content. Hydrogenation of para-isopropylmethyl-cinnamic aldehyde, from which a valuable perfume is obtained, cyclamenaldehyde, does not proceed selectively with this catalyst.

On the other hand, there are indications of the possibility of selective hydrogenation with a nickel catalyst obtained using nickel formate, which was previously used in the hydrogenation of fats.

Nickel formate was obtained by precipitation from a sulfur solution: nickel sulfate nickel with sodium formate followed by its decomposition in vegetable oil. Nickel formate

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always contained impurities of sulfur compounds, which reduced the activity of the catalyst. Due to the difficulty of purification, this catalyst was not widely used.

When a catalyst is used to hydrogenate products from the perfume industry, decomposition is usually carried out in solvents such as phthalic acid methyl ester or paraffin oil. When choosing a medium for decomposition, a number of conditions should be taken into account: the boiling point of the product used should be below the decomposition temperature of nickel formate, the product should not have a persistent odor, should be cheap. Before using the catalyst for hydrogenation, it must be separated from the medium. To decompose nickel formate, the temperature must be raised to 240 ° C. All this makes it difficult to choose the medium.

In contrast to the described method, it is proposed to decompose nickel formate as follows.

The nickel formate is loaded into an iron apparatus with a mechanical stirrer and heated to complete removal of the crystallization process with the charging port open. Then the hatch is closed and the temperature

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increase to 220 ° C by passing a weak current of hydrogen over the catalyst. This temperature is maintained for three hours. Then the temperature is raised to 240 ° C; after heating for two hours at this temperature, the decomposition can be considered complete. The catalyst is cooled to 30-40 ° by passing a weak stream of hydrogen and poured with ethyl or methyl alcohol.

The catalyst prepared by this method was tested for activity and used for selective hydrogenation.

The object of study was a product that had not previously been subjected to selective hydrogenation, namely, para-isopropylmethyl-cinnamic aldehyde, which was converted to cyclamenaldehyde. The reaction was carried out with a 10% catalyst at a temperature of 80 ° C and under a pressure of 50 at. The data obtained are shown in the table.

In distilled product

Until now, cyclamenaldehyde was obtained in a complicated way: para-isopropyl-methyl-cinnamic aldehyde was hydrogenated to para-isopropyl-methyl-hydro-cinnamic alcohol; the latter was oxidized in a toluene solution with a chromic mixture to cycmenaldehyde.

Subsequently, the experiments were extended and the catalyst was applied to selectively hydrogenate a number of other products, such as decylenic aldehyde, methyl-2-phenyl-5lentadien-2, 4-al, etc. In all cases, positive results were obtained.

Hydrogenation of methyl 2-phenyl-5pentadiene-2, 4-al was carried out in a stainless steel autoclave, it became high-pressure steel with a capacity of 1 liter with a mechanical stirrer. 200 g of methyl 2-phenyl-5-pentadiene-2, 4-al, 100 g of ethyl spine, mouth and 20 g (10%) of catalyst were loaded into the autoclave. After loading the autoclave, it was flushed with hydrogen until the air was completely removed and checked for tightness, then the stirrer and electrical heating were turned on.

The temperature was measured by a thermocouple, the pressure was generated by a high pressure compressor. Hydrogenation lasted about 2 hours. 30 min.

The end of the hydrogenation was determined by stopping the absorption of hydrogen. At the end of the reduction process, the electrical heating was turned off, the autoclave was cooled to 50 °, the stirrer was stopped, and the product was unloaded from the autoclave. The product was separated from the catalyst and the alcohol was distilled off.

The amount of crude methyl 2-phenyl5-pentanal was about 190 g, which corresponds to a yield of 95% of the load or 93% of the theoretically possible.

Subject invention

A method of preparing a catalyst for hydrogenating double bonds in unsaturated aldehydes and ketongs by thermal decomposition of nickel formate, characterized in that nickel formate is directly decomposed at a temperature of about 220-240 ° C.