DE734470C - Process for the production of acrolein - Google Patents

Description

Process for Making Aerolein The present invention relates to a novel process for the production of aerolein by synthetic means. Aerolein has so far essentially been made from glycerine by treating it with dehydrating agents Fabrics made. However, this route could not be used for industrial purposes Open Aeroleins.

It is also known to produce aerols from formaldehyde and acetaldehyde. In this case, condensation takes place with the release of water. This splitting off of water the reaction only works with very specific catalysts, namely in their absence acidic or alkaline catalysts, in front of you. According to the invention Aerolein is made directly from acetylene and formaldehyde, while so far the acetaldehyde d served as the starting material. The production of: 'cetaldehyde from acetylene in one according to the invention, a special production process is eliminated.

In the condensation according to the present process presumably takes place The change of a hydrogen atom from the formaldehyde to the acetylene takes place. For support Both acidic and base catalysts are suitable for this reaction.

The reaction, which can be carried out in a vaporous medium, becomes favored by the use of catalysts. When working in the liquid phase mineral acids or salts of mercury can be used as catalysts. Very satisfactory results are obtained if the reaction is carried out in vapor or gaseous form States, d. H. if you have a vapor mixture, which is formaldehyde and acetylene contains, conducts over fixed catalysts at higher temperatures. the The reaction is expediently carried out at temperatures above 150 '. With advantage one works at temperatures of about tgo to 3oo °. Because the reaction is under strong If heat is released, measures are recommended. which are suitable deduct the excess heat of reaction. This can be achieved e.g. B. by appropriate indirect cooling of the contact space or the contact walls or such, that your reaction mixture diluting gases or vapors, such as. B. nitrogen, Carbon dioxide, steam, carbon dioxide or even excess aectylene, mixed in will. Salt-like or ozydic compounds of metals are used as catalysts into consideration, such as B. Oxides, Hydroxy de or carbonates of alkalis, alkaline earths or earth metals, rare earths, also corresponding compounds of zinc, silver, Copper, cadmium, tungsten, manganese, iron Michel, cobalt. _-1, -i place these mentioned Compounds can also be acidic or basic phosphates, chlorides, borates, Acetates, silicates, etc. be used. The mentioned catalytically active Substances can be used on their own or in any "mixture" with one another reach. Furthermore, these supported catalysts can be used. For For this purpose, large-area catalytic converters with absorbing properties are particularly suitable Properties, such as B. activated carbon, active clay or, with advantage, active silica.

The proportions of acetylene and formaldehyde can be selected as desired will. It is advantageous to avoid an excess of forinaldelivd. very good results are achieved with mixtures containing acetylene and formaldehyde in the contain equimolecular or only slightly deviating ratios. On the other hand favorable results are obtained even when using excess acetylene, whereby the excess of acetylene is made available for removing the heat of reaction.

As has been found, it is also useful to control the throughput rate not to be chosen too low, as this results in a loss of _1uslietite and too rapid a The catalyst will weaken. It is beneficial to the throughput speed not -much less than about 0.2 moles of formaldehyde per liter of contact! to Select. Very good results are obtained with a throughput of about 5 mol of formaldehyde per liter of contact and hour. Sometimes it can be beneficial. especially with regard to on the dissipation of the heat of reaction, the throughput rate is still considerable to increase further. The formaldehyde to be used according to the invention can contain water Shape, such as E. The commercially available or anhydrous can be used, -like it can be obtained in particular by gasifying paraformaldehyde. The acetylene can be in the pure state or if necessary; diluted with hydrogen or methane be applied as it is z. B. with the \ letlianlcracl: ung accrues.

The reaction can take place at any, i. H. so also reduced or increased pressure. Example i The vapors of .Io °, 'oigem formaldehyde in a mixture with excess acetylene at temperatures between 200 and 25o- 'passed over a catalyst consisting of active silica, which is impregnated with io °, o their (icwiclites sodium silicate and zinc phosphate). The throughput rate is about 1 mole of formaldehyde per liter of contact and hour set. The vapor mixture obtained in this way is condensed and worked up. Here is acrolein with a yield of; 2 1 "" based on Formaldehyde and o, based on acetylene, obtained. Example e 35cc formaldehyde and 12 1 acetylene are passed per hour at 28o ° over zoo ccm of a catalyst, which was produced by adding activated charcoal with 2o g of So ° Joiger orthophosphoric acid and 0.6 g of copper acetate was impregnated. The resulting vapor mixture is condensed and the catalyst after the addition of o.5 0, `o hydroquinone, based on the total amount of liquid rectified; this results in a yield of 550i, acrolein, based on formaldehyde and a yield of 80 '/ based on acetylene is obtained.

In general, the catalysts have a sufficient service life. if When their activity decreases, they can be easily removed by treating them with oxygenated Regenerate gases at elevated temperatures. 'Sometimes it's an advantage that acetylene to be used initially in a manner known per se from sulfur- or phosphorus-containing To get rid of impurities.

Claims (2)

PATENT CLAIMS: i. Method of making aerolein, thereby characterized in that acetylene and formaldehyde at 15o to 300 ° over catalysts brings to implementation. 2. The method according to claim i, characterized in that mixtures are used which contain about one mole of acetylene or more per mole of formaldehyde contain.