DE1196641B - Process for removing acetylene from a gas mixture predominantly containing ethylene and a smaller amount of acetylene - Google Patents

Description

Process for removing acetylene from a predominantly ethylene and a small amount of acetylene-containing gas mixture ethylene, which is industrial produced by cracking higher molecular weight petroleum hydrocarbons generally contains numerous impurities including acetylene. The physical methods used to remove similar ones found in petroleum Compounds such as propylene from ethylene can usually only be used be used economically to produce ethylene with a moderate degree of purity.

Acetylene is a particularly nasty contaminant because it is light Reactions of ethylene initiates and also with other impurities in the finished Reacts products that have been made from ethylene. Poisoned for example Acetylene in the catalytic oxidation of ethylene to acetaldehyde, as described in British patents 876024 and 876025 describe the palladium chloride catalysts by forming a palladium-acetylene complex. It has been shown to be a value of about 60 ppm can be assumed as the still permissible concentration of acetylene can that in ethylene without too much poisoning of the catalyst for this reaction may be present.

Also in the production of ethyl alcohol from ethylene by hydration it is known that acetylene present in ethylene increases during this process tarry deposits.

Up to now it was common practice to determine the proportion of that present in the ethylene Acetylene with the formation of more ethylene. However, this method has also led to the formation of some ethane.

Ethane is chemically inert and is generally not harmful Effects on the subsequent reactions of ethylene, but it can only be done with difficulty remove from the ethylene. The main difficulty with hydrogenation is that at the same time some ethylene is also reduced, making the process less economical designed. Solvent extraction has also been used to reduce the acetylene concentration in crude ethylene.

In contrast, the process for removing acetylene consists of a gas mixture containing predominantly ethylene and a small amount of acetylene according to the invention in that the gas mixture with one of the for hydration of Acetylene commonly used aqueous solutions of a mercury (II) salt brings into contact and separates the reaction mixture in a manner known per se.

The hydration of acetylene to acetaldehyde takes place in that the crude ethylene, which contains acetylene, by an aqueous solution of sulfuric acid with a mercury (II) salt, e.g. B.

Mercury (II) sulphate, conducts as a catalyst. Preferably will an iron (II) salt is added to the solution as it catalyzes the reaction further. However, this is not an essential measure. It has been shown to be a great Proportion of an iron (II) salt, such as iron sulfate, in relation to the amount of mercury (II) salt, is desirable and gives the solutions longer life. That way Prepared solutions can be easily regenerated by adding air or oxygen z. B. passes through at about 1000 C. As a modification of this basic procedure you can use ethylene, which contains acetylene, together with air or oxygen in pass the catalyst solution and the treated ethylene continuously out of the solution remove and continuously regenerate the catalyst. The After the ethylene has been stripped off, the catalyst solution is regenerated by air directs through them.

The hydration can expediently take place at temperatures which range from room temperature to the boiling point of the solution at the pressure, which is usually from atmospheric pressure to a pressure of several atmospheres can be enough. Temperatures below room temperature and pressures below atmospheric pressure can may be used, but such conditions are less desirable. It has shown, that temperatures of 60 to 1000 C are preferred, combined with a pressure of Atmospheric pressure up to about 7 kg / cm2. Proper choice of conditions that Applied to a particular catalyst can be done in a single pass through the catalyst to remove considerably more than goelo of the acetylene lead, which is present in an ethylene sample.

In the event that the ethylene is used for further reactions, such as hydration is used for ethyl alcohol, can be advantageous from the pretreated ethylene remove the acetaldehyde. This can stream, for example, with cooling of the gas easily by absorption or by reaction of the acetaldehyde, for example with a sodium bisulfite solution. Acetaldehyde boils at 210 C; by application Acetaldehyde can easily be obtained from high temperatures for the reaction of acetylene distill off. Lower temperatures can be used when taking the acetaldehyde want to leave in solution.

The process can be carried out batchwise or continuously. If you want to work in batches, it is possible to use a lot of crude ethylene circulate until the reaction is complete or as complete as desired has expired. When working continuously, it can be advantageous to use hydration of acetylene to acetaldehyde with a subsequent reaction of ethylene a two-step process to combine. For example, if you think of ethylene wants to oxidize to acetaldehyde by means of one of the known processes, it is advantageous to that the crude ethylene gas is passed through two adjacent reaction vessels, wherein in the first stage the amount of acetylene present to a concentration is reduced, which avoids poisoning of the catalyst in the second stage.

The invention is illustrated in more detail by the following examples, where parts are parts by weight, unless otherwise specified.

Example 1 11 liters of crude ethylene containing approximately ethylene. . . . . . . . 670/0 acetylene. 1 O / o methane ... 160/0 ethane. 10% 100% propane . . 1 per cent air. . . Solo were continuously running at a rate of 11 Liter ie hour passed through a catalyst solution in circulation, which in a vertical reaction tube was included. The catalyst solution consisted of 20 g Mercury (II) sulfate and 1.16 g of iron alum, dissolved in 1 liter of 20% sulfuric acid. The reaction mixture was left to stand at 750.degree. Analysis of the gas after 3.5 hours Recirculation showed that 960% of the acetylene had been removed.

0.19 g of acetaldehyde had formed.

Example 2 The catalyst solution consisted of 20 / o mercury (It) sulfate, dissolved in 200 / o aqueous sulfuric acid. 500 ml of this solution became one with Gas-lined steel pipe (length 91 cm, diameter 3.5 cm) is given. It was with a sintered glass distributor at the gas inlet.

Crude ethylene containing 0.31 percent by volume acetylene became at a rate of 7.3 liters per hour (measured at atmospheric pressure) passed through the catalyst solution at 830 C and under a pressure of 6 kg / cm2. A single pass through the tube removed 96% of the acetylene. No ethanol was formed in the diverted gas or in the catalyst solution.

Example 3 The same catalyst solution and equipment were used as used in example 2; 7.2 liters per hour (measured at atmospheric pressure) Crude ethylene were through the catalyst solution at 950 C and a pressure of 5.8 kg / cm2 sent.

940/0 of the acetylene was removed in a single pass. In this case, too, no ethanol was formed.

Example 4 The catalyst solution contained the following per liter of solution Components: 211 g Fe2 (SO4) 39H2O 196 g H2SO4 10 g H2SO4 1 liter of this solution into a vertical glass-lined reaction vessel over a gas distributor initiated.

Then crude ethylene, which contained 0.6700 / 0 acetylene, with passed through the catalyst solution at a rate of 11.1 liters per hour, heating to 950 ° C. for 37 hours.

After this time, the purified ethylene contained 30 ppm acetylene, corresponding to about 99.50 per cent removal of acetylene.

The experiment was continued for a further 25 hours, with the Acetylene removal was greater than 990in.

After 62 hours about 200/0 of the iron (III) salt had become iron (II) salt reduced. The catalyst solution could be oxidized with oxygen at 1000 C.

Claims (3)

Claims: 1. A method for removing acetylene from a predominantly ethylene and a small amount of acetylene-containing gas mixture, thereby characterized in that the gas mixture with one of the for hydration of acetylene usually used aqueous solutions of a mercury (II) salt in contact brings and separates the reaction mixture in a known manner. 2. The method according to claim 1, characterized in that the aqueous mercury (II) salt solution mixed with iron (II) ions. 3. The method according to claim 1 and 2, characterized in that one conducts oxygen into the catalyst solution at the same time as the gas mixture.