DE578994C - Process for the production of unsaturated hydrocarbons - Google Patents

Description

Process for the production of unsaturated hydrocarbons is known unsaturated hydrocarbons can be removed by catalytic dehydration polyhydric alcohols so far only with poor yield because in the in most cases in addition to the formation of the unsaturated hydrocarbons at the same time to a greater or lesser extent, undesirable side reactions occur that are in addition to a considerable reduction in the yield of unsaturated hydrocarbons soon cause charring and smearing of the catalytic converters and thereby their Stop the effect after a short time. As catalysts are for this Case already neutral or acidic phosphates, z. B. aluminum phosphate, potassium pyrophosphate and the like, have been proposed.

It has now been found that these inconveniences can be avoided and that excellent results are achieved both in terms of yield and lifetime of the catalysts if polyhydric alcohols are treated at elevated temperatures in vapor form together with steam with catalysts which contain salts of the oxygen acids of phosphorus under the reaction conditions, e.g. B. by hydrolysis or dissociation, have an acidic effect. This subheading includes the acid salts of the various phosphoric acids as well as neutral salts such as B. neutral alkaline earth phosphates, e.g. B. tricalcium phosphate, which act acidic under the reaction conditions. However, aluminum phosphate is unsuitable because it also has a strong condensation effect and would result in undesirable products. Through a suitable choice of the acid with partial or complete replacement of the replaceable hydrogen atoms by light or heavy metals or by inorganic atom groups, catalysts are obtained for each individual case of dehydration, which in the presence of steam exclusively or predominantly with the elimination of undesired side reactions, such as ether- , Ester, aldehyde, ketone, oxide or condensation, etc .; favor the formation of unsaturated hydrocarbons. The. Catalysts can be prepared in a known manner, for example from the acids of phosphorus and oxides, hydroxides, carbonates, etc., of light or heavy metals or by folding soluble salts of these acids with metal salts, expediently while maintaining certain hydrogen ion concentrations. In many cases it is advantageous to use mixtures of different salts, e.g. B. primary with secondary, different primary among each other, etc. to use, the mixing ratios can vary within .. wide limits. The catalysts can be used as such after prior pressing and molding or on supports or as a mixture. with carrier substances such as pumice stone, graphite, bleaching earths such as fuller's earth, etc., for use.

Also for the dehydration of monohydric alcohols, especially high molecular weight Alcohols, the present process is eminently suitable.

Dehydration can take place under ordinary or minor or increased pressure; also, the catalysts can be used in the molten state will. It is advisable to carry out the reaction at low pressures, however Increased pressure can possibly be an advantage, especially if the to-be-won Product is gaseous and one wishes to obtain it in liquid form. One can In addition to water vapor, also add inert gases.

It can also be used in individual cases to produce high-proof products as much as possible to gain, so that the dehydration is carried out in one operation is not fully completed, leaving the unchanged starting materials after the hydrated products and the water of reaction have left the reaction space separated and sent again over the catalyst. - The choice of temperature depends - on the nature of the starting material and the catalysts used; it is - mostly - between 150 and 500 degrees. The unsaturated ones leaving the reaction space Hydrocarbons are depending on their physical behavior with the water precipitated together in a cooler and separated from the water, e.g. B. at Production of cyclohexene, or im. Cooler from the water at normal temperature freed and then liquefied in a known manner by compression, z. B. in the case des butadiene, .Or fed to a gasometer for other purposes, e.g. B. with ethylene.

Apart from the fact that in many cases, e.g. B. when using acidic alkali phosphates, Under the reaction conditions, the elimination of water with the formation of easily fusible ones Metaphosphates; which stick together the surfaces of the catalytic converter and thus lead to malfunctions Such an addition provides an opportunity to avoid this by adding water vapor also the further advantage that it excludes side reactions that lead to resin and Lead to penance, which quickly make the catalyst ineffective.

In particular, unsaturated hydrocarbons can be obtained by the process the aliphatic and hydroaromatic series.

It is known to dehydrate alcohol to ethylene in the presence of aluminum oxide on pumice stone. In the present process, however, other catalysts are used in the presence of steam. The particular advantage achieved here is that polyhydric alcohols or higher molecular weight monohydric alcohols can also be dehydrated without side reactions. The catalysts to be used in the present case are for dehydration z. B. = has already been proposed from "acetic acid to acetic anhydride. However, the present invention consists in the simultaneous use of steam; the advantages described above are achieved. Example ii # 3-butylene glycol; which contains 2o" / (, water is evaporated and passed at 320 to 330 ° at a rate of 100 g per hour and per liter of catalyst space over cerium phosphate onto pumice stone = phat per liter of pumice stones).

The resulting steam-butadiene mixture is passed through a cooler, the water is separated, the butadiene is passed through a tower with soda lime and chlorine-calcium and finally liquefied in the Dewarschen vessel using a toluene-carbonic acid mixture. The yield of pure butadiene, which is obtained in a very high percentage form; exceeds 90 % of theory.

Similar results can be achieved with bismuth phosphate, acid cadmium orthophosphate and with the neutral pyro- and orthophosphates of magnesium and alkaline earths, but it is advisable to work at temperatures of about 400 ° and the added amount of water to double to triple the amount used Butylene glycol to - increase. EXAMPLES A catalyst consisting of acidic sodium phosphate pressed into molds, which was obtained by pulverizing crystallized primary sodium phosphate, molding and gradually heating to about 220 °, is a mixture of i # 3-butylene glycol with 20% water at about 250 ° conducted in such a way that i2o g per liter of catalyst space are passed through every hour. From the butadiene / steam mixture withdrawn from the contact space, a high percentage butadiene can be obtained in an excellent yield in the same way as in Example i.

Example 3 - About a catalyst consisting of sodium metaphosphate mixed with fuller's earth, obtained by evaporating a solution of primary sodium phosphate with fuller's earth, molding and drying, at 45o to 500 ° technical spirit with 6010 water at a rate of 30o ccm per hour and per liter of catalyst space. Almost pure ethylene is obtained in excellent yield. EXAMPLE 4 The catalyst prepared according to Example 2, consisting of acidic sodium pyrophosphate, is passed in gaseous form at 270 ° in a mixture with 20 ° ia water at a rate of 100 g per hour and per liter of contact space. The yield of cyclohexene from Sp.84 ° is quantitative.

For example 100 parts of secondary calcium phosphate are combined with 10 parts secondary ammonium phosphate, 40 parts of water and 10 parts boiled with hydrochloric acid and washed graphite made into a paste, after which the dough is pressed through an extruder will. The granules obtained after drying and crushing are used as a catalyst under the conditions of example i- for the preparation of butadiene from i # 3-butylene glycol used. The catalyst gives a crude yield of over 90% of very pure Butadiene. B @ eisgiel`6 = `100 parts primary anhydrous sodium phosphate dissolved in 4o parts of water and 8 parts of primary n-butylamine phosphate and 2o parts Graphite entered. It is then evaporated with stirring and the solidified mass finally heated to 16o °. After cooling, the mass will be broken into pieces Crush the desired size, sifted and made for the production of butadiene i # 3-Butylene glycol at 26o ° analogously to the manner described in Example i as a catalyst related. The catalyst is characterized by its particular stability.

The primary sodium phosphate contained in the catalyst goes under the reaction conditions in a mixture, which to about 9o ° 1o of acid sodium pyrophosphate Nag H2 P2 O, and about 10 ° 1a consists of primary sodium phosphate Na H2 P 04, while in the absence of excess water vapor, metaphosphate is formed which the surface area of the catalyst is reduced so that the reaction takes place after a few hours wears off and the surface of the catalyst is smeared by the formation of resin and soot will. When 2o0 /, water vapor is added to the i # 3-butylene glycol, the catalyst works on the other hand excellent for weeks and still contains unchanged things even after this time primary sodium phosphate.

Claims (1)

PATENT CLAIM: Process for the production of unsaturated hydrocarbons from mono- or polyhydric alcohols by passing them over such salts of the oxo acids of phosphorus - with the exception of aluminum phosphate - which have an acidic effect under the reaction conditions, at elevated temperature, characterized in that the process is carried out with the addition of water or steam will.