DE708622C - Process for the catalytic conversion of straight-chain hydrocarbons - Google Patents

Description

Process for the catalytic conversion of straight-chain hydrocarbons en It is known in the presence of the halides of the elements of the third group of the periodic system as catalysts low hydrocarbons into their isomers, z. B. n-butane to isobutane or vice versa to convert. This implementation takes place even at ordinary temperature; if only very slowly, instead. A noticeable one Acceleration can be achieved by increasing the temperature, but it can below Zoo ° considerable decomposition of the hydrocarbons begins become much larger at higher temperatures.

This mode of operation has the further disadvantage that it is proportionate Large amounts of catalyst are necessary, far from decomposition products in a short time Time is largely changed and thereby loses its effectiveness. Consequently Continuous uninterrupted work is hardly possible. Also must be careful care must be taken to exclude moisture, because otherwise disturbing corrosion of the vessel material, if not special building materials such as ceramic Material or enamelled or plastic-lined vessels.

It has now been found that the catalytic conversion is lower straight-chain hydrocarbons with q. up to 6 carbon atoms in those with branched Chain or vice versa can be carried out much more advantageously if the hydrocarbons are used under high pressure, at elevated temperature and in the presence of hydrogen from low partial pressure over difficult to reduce oxidic hydrogenation or dehydrogenation catalysts directs. In general, the partial thickness of hydrogen is chosen not to exceed 30% of the total pressure, advantageously it is less than 5 ° / 0.

You can already work at zoo at printing. However, it is recommended apply even higher prints from Zoo at and above.

At these high pressures, the partial pressure of the hydrogen required in the reaction space can be a fraction of one percent of the total pressure. Hydrogen-containing gases can then also be used instead of pure or practically pure hydrogen. At higher hydrogen partial pressures, it is better to use pure or practically pure hydrogen if the hydrogen-containing gases contain so much admixture that they would reduce the partial pressure of the hydrocarbons to be isomerized too much Take advantage at 60o ° and above, especially if the total pressure is selected to be very high. It is expedient to work at 350 to 50 °, depending on the level of pressure.

The oxidic catalysts used should, like chromium oxide, at the conditions used in general not be reducible because in this In this case, except for copper and silver, there is slight decomposition to the point of carbon deposition enter. These oxide catalysts can be used together with carriers or binders be used. Substances with a large surface area are suitable as such in lumpy form, e.g. B. those of a cxy dic nature, such as clay, silica gel, Zinc oxide, etc., especially if the hydrogen to be added contains traces of volatile Halogen compounds are mixed in, or inert adsorbents such as activated carbon, Silicates 1r. like

In the manner described you can easily do it in a single Operation up to 400j0 and more of the starting hydrocarbon in its isomer convict.

After the isomer has been separated off by rectifying distillation and allow repeated return of the unreacted waste material for implementation yields of over 80%, up to 95% and less can be achieved.

A breakdown to lower hydrocarbons takes place only in subordinate Dimensions instead.

The process is particularly suitable for the isomerization of butanes. EXAMPLE Liquid n-butane is continuously pressed hourly in an amount equal to half the volume of the catalyst through a high-pressure tube filled with lumpy tungsten oxide and heated to q.30.degree. At the same time, a volume of hydrogen equal to the volume of the supplied liquid n-butane (measured without pressure) is pumped in. Behind the connected high-pressure cooler, an acidic mixture of 25% isobutane and 730 /, 7 n-butane collects in the separating vessel which is under the same pressure. The remaining 2% consists of methane, athan and propane. The converted n-butane is thus converted to about 93% into isobutane.

Claims (1)

PATENT CLAIM: Process for the catalytic conversion of straight-chain Hydrocarbons with 4 to 6 carbon atoms in those with a branched chain or vice versa, characterized in that the hydrocarbons mentioned under high pressure, at elevated temperature and in the presence of hydrogen from low partial pressure over difficult to reduce oxidic hydrogenation or dehydrogenation catalysts directs.