Title of Invention

PROCESS FOR THE CATALYTIC HYDROGENATION OF BUTYNEDIOL TO BUTANEDIOL BY A TWO-STAGE METHOD

Abstract

Abstract Process for the catalytic hydrogenation of butynediol to butanediol by a two-stage method Process for the catalytic hydrogenation of butynediol to butanediol by a two-stage method, where the 1st stage is carried out in an agitating reactor with a suspended palladium supported catalyst and the 2nd stage is carried out in a fixed-bed reactor with a nickel supported catalyst. According to the invention a) the conversion from butynediol to butenediol in the 1 st stage is essentially complete and the degree of conversion of the butenediol in the 1st stage is 50 to 85%, preferably 70 to 80%, and b) the catalyst used in the 1st stage is a palladium-silver-aluminium-oxide supported catalyst. The catalyst used in the 2nd stage is a nickel supported catalyst with a small copper component.

Full Text

Process for the catalytic hydrogenation of butynediol to butanediol by a two-stage method The invention relates to a process for the catalytic hydrogenation of butynediol to butanediol by a two-stage process, where the 1st stage is carried out in an agitating reactor with a suspended palladium supported catalyst and the 2nd stage is carried out in a fixed-bed reactor with a nickel supported catalyst. Numerous processes for the technical hydrogenation of butynediol to butanediol are known. These are sub-divided into the so-called single-stage and two-stage processes. A continuous high-pressure process with fixed-bed catalysts is known from DE-PS 890 944, in which butynediol is hydrogenated to butanediol in one stage. The disadvantage of this single-stage high-pressure process is the poor heat dissipation, which, whilst it is improved by a partial recycling of the hydrogenation product to dilute the aqueous butynediol solution, does nevertheless result in the formation of a large number of by-products, mainly of butanol, acetals and high-boiling residues. Therefore, only a comparatively impure product can be obtained by this known process, with a comparatively low yield of approx. 85%. From DE-PS 858 094 a hydrogenation process is known, where an agitating reactor at medium pressure uses a suspended nickel catalyst. Apart fi-om the by-product formation, this known process also only produces comparatively low yields of approx. 88%. However, heat dissipation during hydrogenation is much improved compared with known high-pressure processes. The disadvantage of known medium-pressure processes with suspended catalysts is that they have to be carried out discontinuously. However, the effectiveness of discontinuous processes is poor. In order to reduce the by-product content to a reasonable level, it is necessary to hydrogenate each hydrogenation batch in two stages at different temperatures. In spite of this, the hydrogenation products obtained in this way are of comparatively low quality. The cause of the persistently high by-product content can be found in the fact that when butynediol is hydrogenated under the conditions of the known processes, considerable amounts of aldehydes and acetals are always formed. It is only possible to convert them in part into butanediol at comparatively high temperatures and, in particular, at comparatively high pressures. In order to avoid the disadvantages mentioned, attempts were made to combine medium-pressure hydrogenation in the agitating reactor, as a rule using Raney nickel suspension catalysts, with high-pressure, fixed-bed hydrogenation. In such two-stage processes, butynediol is partially hydrogenated to butanediol at medium pressure in the 1st stage in the agitating reactor. Then, for example, as described in US-PS 3 449 445, hydrogenation is completed in the 2nd stage at high pressure in the fixed-bed trickle reactor in an Ni-Cu-Mn-SiOj catalyst. Aldehydes and acetals formed during this process can be largely removed. Whilst processes of this type do increase the yield to approx. 90% and also considerably improve the quality of the hydrogenation products, they do include the significant disadvantage that the 1st stage of hydrogenation still has to be performed discontinuously. From DD-PS 219 184 a procedure is known, whereby the 1st stage also runs continuously with a suspended nickel supported catalyst. The continuous operation of the two-stage process that this has made possible represents a clear step forward. A significant disadvantage of this process is the narrow butynediol conversion range of 90%, up to a maximum of 98%, which has to be maintained. It is essential to maintain this conversion range in order to avoid a drastic increase in by-product formation outside this range. In other words, butynediol must not be hydrogenated to butanediol, otherwise acetals will be formed under the conditions of the known process, which will inhibit hydrogenation in the high-pressure stage. However, to maintain the prescribed butynediol conversion rate requires a sophisticated and complicated control, which must even take into account almost incalculable quantities, such as catalyst deactivation and variations in catalyst activity, as precisely as possible. The prescribed butynediol conversion range also has to be precisely maintained for safety reasons, in order to prevent the large amounts of butenediol to be found in the 1st stage from starting to hydrogenate. As the conversion of butynediol to butanediol is a strongly exothermic reaction and also because the hydrogenation of butenediol proceeds significantly more quickly than the hydrogenation of butynediol, there is a danger that the agitating reactor of the 1st stage will be destroyed as a resuh of uncontrolled butenediol hydrogenation. In the second stage of this process, i.e. of the high-pressure hydrogenation of butenediol to butanediol, tremendous problems in dissipating the heat also occur on account of the exothermic nature of butenediol hydrogenation and the residual hydrogenation of butynediol. To summarise, it can be stated that the yield of butanediol and its quality is not improved compared with the known processes. In order to avoid these disadvantages, DD-PS 265 394 suggests that in the 1st stage, a continuously operated tube reactor with suspended palladium supported catalyst is used, and in the 2nd stage, a fixed-bed reactor with a nickel supported catalyst. The procedure is designed in such a way that a butynediol conversion rate of 100% and a butenediol conversion rate of > 95% is achieved already in the 1st stage. This process for producing butanediol by hydrogenation of butynediol in two stages, does, however, have the following disadvantages: In order to achieve extensive conversion of butenediol, a comparatively long dwell time for the substances being converted in the first hydrogenation stage is necessary, because of the poor kinetics. This in turn, results in a comparatively high rate of by-product formation. Furthermore, the low productivity of the catalyst used, i.e. 5 kg butynediol per 1 kg catalyst per hour, means that a large amount of catalyst is required, which increases the cost of this process. In order to be able to process sufficient batch quantities, nevertheless, then either correspondingly large-dimensioned reactors are required or the process must be operated with a correspondingly higher catalyst concentration. However, a higher catalyst concentration is disadvantageous because this results in problems when separating out or filtering the catalyst. Furthermore, it is essential with this process that additional heating is provided for the second hydro genation stage, because the amount of hydrogenable substance in the second stage is too small in order to keep the batch at the temperature level necessary for complete conversion. The purpose of the invention is to indicate an improved process for hydrogenating butynediol to butanediol, which delivers a high yield of butanediol of high purity with low expenditure on safety and control systems. This is achieved by the invention in that: a) the conversion from butynediol to butenediol takes place almost completely in the 1st stage and the degree of conversion of the butenediol in the 1st stage is 50 to 85%, preferably 70 to 80% and b) the catalyst used in the 1st stage is a palladium-silver-aluminium-oxide supported catalyst. Because, in accordance with the invention, the reaction is already interrupted when the butenediol is partially converted, long reaction times are avoided in the first stage, compared with processes which attempt to achieve as complete a conversion of butenediol as possible. However, after the first hydrogenation stage, there is still sufficient hydrogenable material remaining, in the case of the process according to the invention, so that additional heating of the fixed-bed reactor in the 2nd stage can be dispensed with. Since for the degrees of conversion chosen, the major part of the heat is already liberated in ^ the 1 St stage, any overheating in the 2nd stage, which would result in the formation of excess | by-product, can be prevented. Compared with known processes, which essentially attempt only to achieve complete conversion of butenediol, where butynediol is completely converted and the butenediol is partially converted, comparatively less needs to be spent on control. This results from the fact that the conversion does not have to be terminated precisely before the start of butenediol hydrogenation, after the conversion of butynediol. As already mentioned, since by-product formation of high-boiling components can be considerably reduced by the process according to the invention, a comparatively more simple separation stage connected after the hydrogenation stages, is required. In addition, higher butanediol yields are achieved. By modifying the palladium with silver, selectivity is increased. Theta-aluminium oxide, which is formed when aluminium hydroxide is calcinated and, because of its low OH group content, has low acidity, is used as the preferred support. Furthermore, theta-aluminium oxide has a relatively large pore structure, which prevents carbon deposits, which in turn results in selectivity advantages. One development of the process according to the invention is characterised by the fact that the amount of catalyst supplied to the first stage is between 0.1 and 1 % by weight, preferably between 0.2 and 0.5 % by weight. The catalyst requirement of the process according to the invention, can therefore be described as comparatively small. A further advantage of the low catalyst concentration can be seen in the improved fihering properties. The catalyst used in the second stage is preferably a nickel supported catalyst with small copper component (roughly 1 to 3%). The addition of copper improves the selectivity and activity of the catalyst. As a development of the process according to the invention, it is suggested that the 1st stage is operated at a pressure of 5 to 50 bar, preferably 20 to 30 bar, and at a temperature of 50 to 100°, preferably 60 to 80 °C, and the second stage is operated at a pressure of 10 to 50 bar, preferably 20 to 40 bar and a temperature of 100 to 150°C, preferably 125 to 140°C. Accordingly the present invention provides a process for the catalytic hydrogenation of butynediol to butanediol by a two-stage method, where the 1st stage is carried out in an agitating reactor with a suspended palladium supported catalyst and the 2nd stage is carried out in a fixed-bed reactor with a nickel supported catalyst, characterised in that, a) the conversion from butynediol to butenediol in the 1st stage is essentially complete and the degree of conversion of the butenediol in the 1st stage is 50 to 85%, preferably 70 to 80%, and b) the catalyst used in the 1st stage is a palladium-silver-aluminium-oxide supported catalyst. The mvention and further developments of it are explained on the basis of the two examples below. Here, the abbreviations BID, BED and BAD stand for butynediol, butenediol and butanediol. WE CLAIM; 1. A process for the catalytic hydrogenation of butynediol to butanediol by a two- stage method, where the 1st stage is carried out in an agitating reactor with a suspended palladium supported catalyst and the 2nd stage is carried out in a fixed-bed reactor with a nickel supported catalyst, characterised in that, a) the conversion from butynediol to butenediol in the 1st stage is essentially complete and the degree of conversion of the butenediol in the 1st stage is 50 to 85%, preferably 70 to 80%, and b) the catalyst used in the 1st stage is a palladium-silver-aluminium-oxide supported catalyst. 2. The process according to claim 1, wherein the catalyst used in the 2nd stage is a nickel supported catalyst with a small copper component. 3. The process according to claim 1 or 2, wherein the amount of catalyst fed to the 1st stage is between 0.1 and 1% by weight, preferably between 0.2 and 0.5 % by weight. 4. The process according to any of the claims 1 to 3, wherein the 1st stage is operated at a pressure of 5 to 50 bar, preferably 20 to 30 bar, and at a temperature of 50 to 100°C, preferably 60 to 80°C, and the 2nd stage is operated at a pressure of 10 to 50 bar, preferably 20 to 40 bar, and at a temperature of 100 to 150°C, preferably 125 to 140°C. 5. A process for the catalytic hydrogenation of butynediol to butanediol by a two- stage method substantially as herein described and exemplified.

Documents:

1339-mas-1997 abstract.pdf

1339-mas-1997 assignement.pdf

1339-mas-1997 claims duplicate.pdf

1339-mas-1997 claims.pdf

1339-mas-1997 correspondence others.pdf

1339-mas-1997 correspondence po.pdf

1339-mas-1997 description (complete) duplicate.pdf

1339-mas-1997 description (complete).pdf

1339-mas-1997 form-19.pdf

1339-mas-1997 form-2.pdf

1339-mas-1997 form-26.pdf

1339-mas-1997 form-4.pdf

1339-mas-1997 form-6.pdf

1339-mas-1997 others.pdf

1339-mas-1997 petition.pdf