DE2912230B1 - Process for the recovery and reactivation of used rhodium and phosphine-containing catalysts from reaction products of rhodium-catalyzed oxosynthesis - Google Patents

Description

It is especially surprising that the activity

and selectivity of the regenerated rhodium catalyst are higher than with freshly prepared rhodium catalysts.

For the recovery and activation of used and in their activity greatly reduced rhodium and phosphine-containing catalysts from the reaction products the rhodium-catalyzed oxo synthesis is subjected to the liquid contents of the reactor with the spent, partially deactivated catalyst after separating off Hydrogen, carbon monoxide and unreacted olefins from a gentle distillation, taking a small amount of distillation residue, which is practically all of the rhodium contains, and a practically rhodium-free distillate is obtained. The still residue after adding the appropriate amount of phosphine, fresh or recovered, and a diluent such as the aldehyde to be recovered used as a catalyst for hydroformylation. Surprisingly, this one has Recovered contact at least the full activity and selectivity good, new manufactured catalysts.

The practically rhodium-free distillate (stream 1 a), rhodium content <0.2 ppm by weight, in particular <0.1 ppm by weight, are separated into those to be obtained Aldehyde, an intermediate run containing a multitude of substances, one for the Activation of fresh or recovered rhodium catalyst suitable phosphine fraction and a rectification residue that is poor in valuable phosphine, phosphine oxide contains. This distillative separation of the distillate (stream la) can be in several Distillation devices take place.

With the gentle distillative division into at least two material flows the reaction mixture is heated to temperatures of 150 to 300 ° C., preferably from 170 to 270 ° C., in particular from 200 to 220 ° C., at pressures from 0.1 to 1500 mbar, preferably working in two stages and in the first stage 1000 to 1500 mbar and the second stage distilled at 1 to 10 mbar. The same Effects achieved by applying reduced pressure can also be achieved by Application of an inert carrier gas stream can be achieved. Here it is essential that the heating takes place gently without overheating. Separation by distillation can in every distillation plant with a heating system protected against overheating be carried out, preferably distilled within short times, for example in a thin film evaporator or falling film evaporator. The sump temperature should preferably not to exceed 200 ° C.

In the gentle distillative division, the used ones are narrowed down Mixtures containing rhodium and phosphine to 0.1 to 30 percent by weight, preferred to 1 to 10 percent by weight, in particular to 1.5 to 5 percent by weight of the distillation residue a (material flow lb).

The distillative distribution of the partially deactivated rhodium catalyst containing reaction mixture in at least two streams takes place in one or more distillation devices. For example, in a first Distillation system first narrow the sump to 50 to 500 ppm by weight Rh and put it in a second distillation plant to 1000 to 25000 ppm by weight Rh, with the first Distillation expediently under normal pressure and the second distillation at reduced pressure Printing.

The separation by distillation into the streams can be discontinuous and / or take place continuously. Distilled when working in two or more stages is preferably carried out continuously in the second stage under reduced pressure. as well can discharge the used, partially deactivated rhodium catalyst carried out continuously or batchwise from the hydroformylation reactor. In the discontinuous discharge of the deactivated catalyst, it is withdrawn the entire contents of the reactor are preferably used in the case of continuous discharge only a partial flow of the reactor contents is withdrawn and the recovered is carried out activated contact continuously back into the reactor.

The renewed use of the recovered rhodium concentrate (material flow lb) takes place with such an amount of phosphine that at least 100 g mol of phosphine, based on one g atom of rhodium, are present in the reaction medium. An addition of phosphine is not necessary if more than 100 moles of phosphine, based on one g Atom rhodium, present in the material flow lb. The catalyst batch can with fresh or recovered phosphine. It is preferable to use the recovered Phosphine a.

This regenerated phosphine does not have to be used in its pure form It can also be mixed with other substances that do not have any adverse effect on the catalyst activity and / or the selectivity have to be applied. Suitable phosphines are, for example, triarylphosphines. Is particularly suitable Triphenylphosphine.

The activity increase and catalyst recovery are suitable in the hydroformylation of olefins, preferably C2 to C4 olefins, in particular in the hydroformylation of propene to butanal.

The method according to the invention improves and simplifies the recovery active rhodium- and phosphine-containing catalysts and enables for the first time an increase in the activity of used rhodium-containing catalysts. Practically there In addition, the process does not produce any exhaust gases or contaminated wastewater very environmentally friendly.

Example 1 After the hydroformylation of propene with a longer Time spent and significantly reduced in its activity and selectivity Hydridocarbonyltristriphenylphosphine-rhodium catalyst, hydrogen is first separated, Carbon monoxide and unreacted propene. In an oil-heated falling-film glass evaporator (Evaporator area 814 cm2 (3 tubes, 600 mm long, inner diameter 14.4 mm), the is heated with a 214 "C hot heating medium, is given at a pressure of 1009 mbar 563 g / h of this hydroformylation residue, heated with hot oil at 203 ° C. of propene, which is about 0.124 g Rh of a used and in its activity significantly reduced hydridocarbonyltristriphenylphosphine rhodium (220 ppm Rh) contains. The top product obtained is 84.4 g / h (= 15 percent by weight) of low boilers, which essentially consist of butyraldehydes and are practically rhodium-free (< 0.1 ppm by weight Rh). 478.6 g / h of higher-boiling products are obtained as the bottom product. This higher-boiling product is poured into an oil at 212 ° C. without cooling heated thin-film evaporator made of glass (evaporator area: 900 cm2, rotor: 900 Rpm) that you get at a pressure operates from 4 mbar. As a top product 469.5 g / h of a rhodium-free distillate are obtained (rhodium content not detectable, <0.1 ppm Rh). The distillate of the thin film evaporator is rectified in one System of two continuously operated columns.

The columns each have 20 practical trays, the feed to the first column takes place in liquid form on the 10th tray, while the bottom product of the first column also liquid is passed to the 10th tray of the second column. The first column operates one with a head pressure of 40 mbar and a differential pressure of 30 mbar. The head temperature is 1800C, the reflux ratio is 1. Under these conditions, the Distillate 0.12 percent by weight triphenylphosphine. The second column is operated under a head pressure of 30 mbar. The temperature at the top of the column is 236 "C, the bottom temperature 280 "C. The reflux ratio is 0.4. The triphenylphosphine obtained is 90% pure according to gas chromatographic analysis. This product is based on same Triphenylphosphine content, for the production of the rhodium catalyst fresh triphenylphosphine equivalent to. This eliminates the need for any further cleaning that is possible. That Bottom product of the second column contains triphenylphosphine oxide. In the sump of the thin film evaporator 9.1 g / h are obtained (= 1.62 percent by weight, based on the feed to the falling film evaporator) a highly viscous solution that contains all of the rhodium (13800 ppm by weight Rh) and 3.5 percent by weight Contains phosphorus. This solution is mixed with 30 g / h triphenylphosphine (TPP), diluted with 530 g / h of n-butanal, a solution of 220 ppm Rh at a molar Ratio of phosphine to rhodium of 102 1 is obtained.

Hydroformylation is carried out continuously with 2 kg of this contact solution working test apparatus 125 g / h propene with 133 Nl / h synthesis gas (CO: H2 1: 1) at 17 bar and 100 ° C. The raw discharge is 188 g / h (conversion z 88%) with one amount of exhaust gas of 27 l / h (15 vol.% C3Hb). The raw output contains an average of 92.6 percent by weight n-butanal and 5.6 percent by weight i-butanal. The n / i ratio is therefore at 16.5.

The 9.1 g / h of stream Ib are added instead of 30 g / h of pure Triphenylphosphine with 33.3 g / h of the in this example as the distillate of the second 90% of the column obtained triphenylphosphine, diluted with 527 g / h of n-butanal and carries out a hydroformylation according to the information in this example with 2 kg of this mixture through, one obtains within the usual experimental and analytical fluctuations the same results.

Is used in the continuously operating experimental apparatus Hydroformylation of 130.3 g propene / h and 139 Nl / h synthesis gas (CO: H2 = 1: 1) at 17 bar and 100 "C 2 kg of one that has been used for a long time and its activity considerably reduced contact, which contains 220 ppm by weight of Rh, is obtained only a raw discharge of 160.8 g / h (conversion = 72%) with an exhaust gas quantity of 61.5 Nl / h (16% by volume C3H6). The crude discharge contains an average of 89.7 percent by weight of n-butanal and 8.4 percent by weight isobutanal. The n / i ratio is 10.7.

If 112 g / h of propene are hydroformylated with 120 standard l / h of synthesis gas Hydridocarbonyltristriphenylphosphine-rhodium freshly prepared under the same conditions as a rhodium contact [HRh (COX til sP) 3] which is mixed with 150 g of triphenylphosphine and with n-butanal on 2 kg is made up (rhodium content of the solution 220 ppm), one obtains one Raw discharge of 153g / h (conversion z 80%) with an exhaust gas quantity of 39 Nl / h (15.5 vol.% C3H6). The raw discharge contains an average of 91.6 percent by weight n-butanal and 6.0 percent by weight i-butanal. The n / i ratio is 15.3.

Comparable results are obtained if one follows this information Example with a load of 1150 g / h in the thin film evaporator at one temperature of 2500 C works.

Example 2 According to the information in Example 1, 1486 g / h were used there used residue concentrated in the oil-heated falling-film glass evaporator. That concentrated product was in an amount of 1263 g / h without cooling, as in the example 1 described, fed to the glass thin film evaporator. Distill 1122 g / h and there remains a residue of 141 g / h (= 9.5 percent by weight, based on on the inlet to the falling film evaporator), which brought in everything with the product Contains rhodium (concentration 2315 ppm by weight Rh) and a concentration of 2.0 Weight percent phosphorus. 61 g / h of triphenylphosphine are added to this solution diluted with 1280 g / h of n-butanal, a solution containing 220 ppm of Rh at a molar ratio of phosphine: rhodium of 102: 1.

With 2 kg of this contact solution is hydroformylated in the example 1 described apparatus 134.8 g / h propene with 144 Nl / h synthesis gas (CO: H2 = 1: 1) at 17 bar and 1000C. The average gross output is 187 g / h (conversion 81%). That The mean n / i ratio is 15.1.

Comparable results are obtained if one follows this information For example, with a load of 620 g / h in the thin-film evaporator at one temperature from 1980 C works.

Comparative Example 3 In the falling-film glass evaporator described in Example 1 if, as described there, the same raw material is concentrated to 85%, 1044 g / h of this concentrated product in the thin film evaporator described in Example 1 further concentrated at a pressure of 3 mbar and a heating medium temperature of 147 "C. 430g / h, which do not contain rhodium, evaporate and a residue remains of 614 g / h, corresponding to a reduction of 50%, based on that of the falling film evaporator amount of substance supplied.

The residue contains the entire amount of rhodium.

The concentration is 440 ppm by weight Rh. The residue also contains 1.4% phosphorus compounds, calculated as phosphorus. Add 614 to this solution g / h of n-butanal, so that you get a solution with 220 ppm by weight Rh at a molar ratio Phosphine to rhodium from 106 1 is obtained.

With 2 kg of this contact solution is hydroformylated in the example 1 described apparatus 136 g / h propene with 145 Nl / h synthesis gas (CO: H2 = 1: 1) at 17 bar and 100 "C. The raw output is on average 175 g / h (conversion 75%) The average n / i ratio is 9.6.

Comparative Example 4 A) According to the information in DE-OS 27 30 527 (page 15) were after hydroformylation with freshly prepared Hydridocarbonyl triphenylphosphine rhodium [HRh (COX3P) 3] and the separation of hydrogen, carbon monoxide and unreacted Propene at a pressure of 1 mm Hg and a temperature of 100 "C is the n- and i-butanal stripped as an overhead fraction. The bottom product contains the rhodium catalyst in a Rh concentration of 340ppm and 8.8% triphenylphosphine (TPP). Corresponding a molar ratio TPP:: Rh of 102 1.

1.3 kg of this recovered catalyst are mixed with 700 g n-butanal, uses this catalyst solution (220 ppm Rh; TPP: Rh = 102: 1) in a continuously operating experimental apparatus for the hydroformylation of 112 g propene / h and 120 Nl / h synthesis gas (CO: H2 = 1 at 17 bar and 100 "C.

A crude discharge of 153 g / h (yield 80%) is obtained with an amount of exhaust gas of 39 Nl / h (15.5% by volume C3H6). The raw discharge contains an average of 91.6 percent by weight n-butanal and 6.0 weight percent i-butanal.

The n / i ratio is 15.3.

B) According to the information in DE-OS 27 30 527 (page 15) were after Hydroformylation has been used for a long time, about 1 year and in its activity considerably reduced rhodium catalizer and after the separation of hydrogen, carbon monoxide and unreacted propene, the n- and i-butanal at a pressure of 1 mm Hg and a temperature of 100 "C as the overhead fraction stripped off. The bottom product contains the rhodium catalyst in a Rh concentration of 340 ppm and 8.8% TPP. This corresponds to a TPP: Rh molar ratio of 102 :1.

1.3 kg of this recovered catalyst are mixed with 700 g n-butanal and uses this catalyst solution (220 ppm Rh: TPP: Rh = 102: 1) in the continuously operating experimental apparatus for the hydroformylation of 130.3 g propene / h and 139 Nl / h synthesis gas (CO: H2 = 1: 1) at 17 bar and 100 "C. Only a crude discharge of 160.8 g / h (yield 72%) with an exhaust gas quantity of 61.5 standard l / h (16 vol% C3H6). The crude discharge contains an average of 89.7 percent by weight of n-butanal and 8.4 percent by weight isobutanal. The n / i ratio is 10.7.

C) The bottom product obtained after Comparative Experiment B with the Rhodium catalyst in a concentration of 340 ppm is reworked by distillation the details of Example 1 of the present application. A highly viscous one is obtained Solution containing all of the rhodium (13,800 ppm Rh) and 3.5 weight percent phosphorus contains. This solution is mixed with 30 g / h triphenylphosphine, diluted at 530 g / h n-butanal, a solution of 220 ppm Rh at a molar ratio of Phosphine to rhodium from 102 1 is obtained.

With 2 kg of this contact solution, hydroformylation is carried out according to the information of the example 1125 g / h propene with 133 Nl / h synthesis gas (CO: H2 = 1: 1) at 17 bar and 100 "C. The crude discharge is 188 g / h (yield 88%) with an exhaust gas quantity of 27 Nl / h (15 vol.% C3H.

The crude discharge contains on average 92.6 percent by weight of n-butanal and 5.6% i-butanal. The n / i ratio is 16.5.

Claims (1)

Claim: process for the recovery and reactivation of used Catalysts containing rhodium and phosphine. z oo them in the oxo synthesis in In the presence of an excess of phosphine, the reaction mixture with the catalyst in a known manner by distillation into an essential distillate containing the bulk of the desired aldehyde and a bottom product is separated. characterized . that you get the rhodium catalyst Swamp product containing genetically modified activity gently at Tempelatulen from 150 to 300 "C and pressures of 1) 09 to 01 mbar in one or more stages by distillation separates into at least two sources. whereby the mixture of substances accumulating on the head prefers the volatile reactants such as i.a. Aldehydes, acetals, esters and phosphines. but contains practically no rhodium compounds. and that in the swamp accruing mixture of substances. which contains practically all rhodium compounds. on 0.1 to 30 percent by weight is concentrated and this concentrated mixture of substances so a lot of phosphine is added, that at least 100 moles of phosphine per g atom of rhodium are present in the regenerated mixture. Phosphine-containing rhodium complexes are excellent catalysts for the production of aldehydes and alcohols by reacting olefins with Carbon monoxide and hydrogen (hydroformylation or oxo synthesis). By addition of excess phosphine one can affect the activity and selectivity in terms of improve the nAl canal formation of the phosphine-containing rhodium complexes (DE-OS 19 39 322 and DE-OS27 1585). However, after prolonged use, the activity of these catalysts decreases so far after. that the catalytic converter has to be replaced. Strong in their activity Diminished rhodium catalysts could previously only be achieved with the help of a chemical Regeneration of the catalyst. optionally after separating off the rhodium, recovered will. Strong acids are often used here. The time-consuming work-up with the help of a chemical regeneration requires various apparatuses that are exposed to severe corrosion due to the presence of strong acids or are made from expensive materials must be created. However, none of these methods allow the direct increase in activity and recovery of both valuable components of the used catalysts, both rhodium and phosphine. In addition This process results in considerable losses of expensive rhodium. It is also known that the dissolved active hydroformylation catalysts, for example cobalt or rhodium catalysts, after releasing the CO-containing catalyst The gas thermally by heating it to 200 C, if necessary after adding water, to be deposited as metals. However, these known methods have been used with rhodium catalysts considerable disadvantages, since the Rh metal obtained only with considerable difficulty and large losses on an active catalyst for hydroforming mylation can be worked up (DE-AS 12 90 535, DE-AS 21 45 532). From DE-OS 20 44 651 it is also known that bis (triphenylphosphine) rhodium carbonyl chloride decomposes at temperatures of 180 to 200 "C. In DE-AS 24 06 323, special pointed out that in the distillation of the oxo products in the bottom of the column remaining rhodium catalyst is deactivated. According to the process of DE-OS 27 30 527, the reaction mixture is separated with the active catalyst and the excess phosphine by distillation in an im essentially the majority of the desired aldehyde-containing distillate and a bottom product containing the rhodium catalyst and the excess phosphine on. In order to prevent a decrease in productivity, a sufficient one is used Amount of oxygen in the liquid phase. This addition of oxygen can deactivate the catalyst only slow down, but not prevent. However, this method does not allow the reactivation and the restoration of the selectivity of longer Use of rhodium catalysts with reduced activity and selectivity. Thus the task arises of the greatly reduced activity of the to bring used rhodium catalysts back to their original level and these catalysts from the reaction products of the oxo synthesis in as quantitative a manner as possible Recover yield in active form in an economical and simple manner. According to the invention, this object is achieved in accordance with the details of the claims solved. The inventive method has the advantage that you can easily and economically an active rhodium and phosphine containing catalyst high selectivity recovered. Compared to the known processes for regeneration of used, partially deactivated rhodium catalysts according to the invention Process also has the further advantage that when recovering the active rhodium and phosphine-containing catalysts no chemicals are consumed. The inventive In addition to the recovery of the active rhodium catalysts, this process also enables the recovery of phosphines. The recovery of active rhodium and phosphine-containing substances Enables catalysts in the simple and economical manner according to the invention it, the rhodium catalysts already with a lower loss of activity 7u regenerate and thus the hydroformylation with higher space-time yields and / or perform higher selectivity. Surprisingly, when recovering of the rhodium catalysts not only have a high activity, but also a high one Selectivity set. It was particularly surprising that, contrary to the clear teaching many publications on the gentle distillative dividing according to the invention the rhodium compounds are neither decomposed nor deactivated in at least two streams are still deposited as metals, rather than soluble compounds remain in solution, or represent releasable compounds, with their activity and Selectivity is increased significantly. With greater constriction, it only increases the viscosity of the solution of the rhodium compounds.