DE4430057C2 - Process for separating undesirable components from a butynediol solution - Google Patents

Description

The invention relates to a method for separating unwanted components, such as e.g. B. acetylene, formaldehyde, propargyl alcohol or the like, which from the butynediol Synthesis withdrawn crude butynediol solution.

The crude butynediol solution withdrawn from the butynediol synthesis still contains physically dissolved acetylene, unreacted formaldehyde, propargyl alcohol as well as other low and high boilers. It is known by means of a stripping column Remove acetylene and the crude butynediol solution then two in a row to supply arranged vacuum distillation columns. In the first vacuum The crude butynediol solution of formaldehyde and low boilers becomes the distillation column frees the high boilers in the second vacuum distillation column is separated off and the pure butynediol solution is withdrawn overhead (see e.g. Chem. System Inc., Butanediol / Tetrahydrofuran Report, No. 91S15, April 1993, page 22, Figure II. B. 1). The separation of the above-mentioned undesirable components from the raw Butynediol solution is necessary because acetylene and formaldehyde are otherwise in the downstream hydrogenation reactor lead to increased by-product formation and thus the product quality and yield would deteriorate. In addition, the Catalyst activity can be reduced.

The aim of the invention is to remove the undesirable components in a single To separate the separation process.

This is achieved according to the invention in that the undesirable components are separated from the crude butynediol solution by means of hot steam stripping, wherein the steam supplied to the hot steam stripping has a temperature between 105 and 140 ° C and a pressure between 1.2 and 1.5 bar.

By means of hot steam stripping it is now possible to inject the unwanted components in a single column from the crude butynediol solution. Result from this several advantages. The vacuum distillation used in the known method for formaldehyde removal leads to the fact that the raw material freed from formaldehyde Butynediol solution in the bottom of the first vacuum distillation column almost water-free becomes. Boiling the raw butyne diol solution increases the strength High boiler formation. As a result, the proportion of those which interfere with the hydrogenation High boilers so high that, as already mentioned above, this in an additional Vacuum distillation column must be separated. The overhead distillation  of butindiol leads to a not inconsiderable risk of accident, which then arises when the crude butynediol solution breaks down spontaneously. The critical bottom temperature in the distillation column is about 150 ° C. In the method according to the invention, however, the water content of the raw Butynediol solution almost constant. So there is no boiling up Water-free butynediol solution, such as that of the prior art Procedure is the case. A spontaneous decay can therefore not occur. Also learns the raw butyne diol solution, also due to the shorter residence times within the Steam stripper column, a gentler treatment than this in the thermal distillation is the case.

The invention and a special exemplary embodiment are explained in more detail with reference to FIG. 1 and the table below. The concentration of the individual components is given in mol%.

Table 1

The steam stripper column K is fed via line 1 to the crude butynediol solution at a pressure of 1.3 bar and a temperature of approx. 105 ° C. Column K is further charged via line 2 with superheated steam at a pressure of 1.3 bar and a temperature of 140 ° C. The temperature of the water vapor supplied can be between 105 and 140 ° C, while the pressure is preferably in the range between 1.2 and 1.5 bar. The butynediol solution drawn off via line 3 now contains only about 0.5 mol% of formaldehyde. To set this amount of residual formaldehyde, about 1.5 kg / h of steam are required for 1 kg / h of raw butynediol solution. The residual formaldehyde content can be reduced by increasing the amount of steam up to the formaldehyde detection limit, i.e. up to about 100 ppm. Acetylene is withdrawn via line 5 at the top of the steam stripper column K, while formaldehyde, water and low boilers, such as, for example, are removed via line 6 . B. propargyl alcohol to be deducted. The butynediol solution drawn off via line 3 can now either be fed directly to a downstream hydrogenation (not shown) or first to a high boiler removal and then to the hydrogenation.

In summary, it can be stated that with the method according to the invention at least one column or column saved compared to the known method can be. So hot steam stripping does not only include the stripping and the first Distillation process of the known method together, but can under Circumstances, depending on the selected parameters or depending on the Composition of the raw butynediol solution supplied to the hot steam stripping, also the second distillation process, which serves to separate the high boilers, dispense.

Claims (1)

Process for separating undesired constituents, such as acetylene, formaldehyde propargyl alcohol or from the crude butynediol solution withdrawn from the butynediol synthesis, characterized in that the undesired constituents are separated from the crude butynediol solution by means of hot steam stripping, the steam supplied to the hot steam stripping being at a temperature between 105 and 140 ° C and a pressure between 1.2 and 1.5 bar.