GB2075857A

GB2075857A - Making hydroformylation catalysts

Info

Publication number: GB2075857A
Application number: GB8114576A
Authority: GB
Original assignee: Davy Mckee Oil and Chemicals Ltd
Current assignee: Johnson Matthey Davy Technologies Ltd
Priority date: 1980-05-15
Filing date: 1981-05-13
Publication date: 1981-11-25

Abstract

Complex rhodium hydroformylation catalysts are prepared by treating a liquid body containing a triarylphosphine and an inorganic catalyst precursor, such as Rh2O3. 10H2O or Rh (NO3)3.2H2O, with carbon monoxide under essentially hydrogen-free conditions at a temperature in the range of from about 50 DEG C to about 160 DEG C, and thereafter supplying carbon monoxide and hydrogen to a liquid reaction medium comprising material of the thus treated liquid body.

Description

SPECIFICATION Process This invention relates to hydroformylation, more particularly to the preparation of rhodium complex hydroformylation catalysts.

Hydroformylation is a well-known reaction in which an alpha-olefinic compound, such as ethylene or propylene, is reacted with hydrogen and carbon monoxide under appropriate conditions of temperature and pressure in the presence of a catalyst to yield an aldehyde containing one more carbon atom than the alpha-olefinic compound. Thus propionaldehyde is formed from ethylene, whilst propyiene yields a mixture of n-and iso-butyraldehydes, of which the n-isomer is generally the more commercially valuable. Initial proposals utilised cobalt carbonyls as hydroformylation catalyst but more recently a process utilising a rhodium-based catalyst has been adopted in commercial hydroformylation plants.This process is described, for example, in an article entitled "Low-pressure OXO process yields a better product mix", Chemical Engineering, December 5, 1977. A further description of the process can be obtained, for example, from United States Patent Specification No.3527809 and British Patent Specification No. 1338237.

Although the exact nature of the catalytic species used in this process is not entirely clear, it has been postulated that it is tris(triphenylphosphine) rhodium carbonyl hydride, i.e. HRh(CO)(TPP)3 where TPP represents triphenylphosphine P(C6H5)3. This compound is a crystalline compound and can be added as such to the hydroformylation reaction medium. Alternative catalyst precursors that have been suggested include rhodium nitrate, rhodium trichloride, rhodium dicarbonyl chloride dimer, rhodium carbonyl triphenylphosphine acetylacetonate, and rhodium dicarbonyl acetylactonate.The rhodium complex catalyst precursors, such as rhodium carbonyl triphenylphosphine acetylacetonate and rhodium dicarbonyl acetylacetonate, are converted smoothly under hydroformylation conditions to the active catalytic species in the presence of the olefin, hydrogen, carbon monoxide and excess triphenylphosphine ligand. However, a disadvantage of the use of such complex precursors is their considerable cost because to the cost of the rhodium metal content and of the triphenylphosphine content must be added the cost of forming the complex. The use of inorganic precursors, on the other hand, whilst enabling the use of a cheaper precursor, is found to result in relatively inefficient utilisation of rhodium since it is found that not all of the rhodium added is converted to the active catalytic species in the presence of excess ligand under hydroformylation conditions.For this reason, despite the added cost of the complex catalyst precursors, it is generally better to add the rhodium as a complex precursor to the hydroformylation reactor rather than as an inorganic precursor.

It is accordingly desirable that a process should be developed which permits the more efficient conversion of inorganic rhodium precursors into active catalytic species than is possible using existing techniques.

The present invention accordingly seeks to provide a hydroformylation process in which conversion of inorganic rhodium precursors to active catalytic species is optimized. It further seeks to provide a process for generating a rhodium complex hydroformylation catalyst from inorganic rhodium precursors with optimum efficiency.

According to the present invention there is provided a process for producing an aldehydic compound or compounds by hydroformylation of an alpha-olefinic compound with carbon monoxide and hydrogen comprising: establishing a liquid body containing a triarylphosphine and an inorganic rhodium catalyst precursor which is convertible under hydroformylation conditions in the presence of free triarylphosphine to a soluble rhodium complex hydroformylation catalyst; treating the liquid body with carbon monoxide under essentially hydrogen-free conditions at a temperature in the range of from about 50"C to about 160"C; supplying carbon monoxide, hydrogen and alpha-olefinic compound to a liquid reaction medium comprising material ofthethus-treated liquid body;; maintaining the liquid reaction medium under pressure and temperature conditions conducive to hydroformylation of the alpha-olefinic compound; and recovering aldehydic product or products from the liquid reaction medium.

The invention further provides a novel process for generating a complex rhodium hydroformylation catalyst which comprises; establishing a liquid body containing a triarylphosphine and an inorganic rhodium catalyst precursor which is convertible under hydroformylation conditions in the presence of free triarylphosphine to a soluble rhodium complex hydroformylation catalyst; treating the liquid body with carbon monoxide under essentially hydrogen-free conditions at a temperature in the range of from about 50"C to about 1600C; and supplying carbon monoxide and hydrogen to a liquid reaction medium comprising material of the thus-treated liquid body.

Although the mechanism involved has not been entirely clarified, it is tentatively postulated that the inorganic rhodium catalyst precursor is converted during the treatment with carbon monoxide to a rhodium complex precursor containing both carbon monoxide and triaryl-phosphine ligand and that this complex precursoWis thereafter transformed under the hydroformylation conditions employed to the active catalytic species. However, it is not intended that the applicant should be bound by this explanation and it may turn out later that some other mechanism is in fact involved.

United States Patent Specification No.3801646 describes a hydroformylation process in which the reaction is intiated by contacting the liquid hydroformylation reaction medium with carbon monoxide at a pressure of at least about 1 atmosphere before the reaction medium is contacted with hydrogen. in this prior process the liquid reaction medium may contain a rhodium or iridium catalyst in complex combination with carbon monoxide and a biphyllic ligand, such as tripenylphosphine. The use of complex chelates of rhodium as catalysts is also suggested. Contacting of the catalyst with carbon monoxide prior to introduction of hydrogen is said to achieve a catalyst having a higher initial activity whereby the reaction can be commenced without any prolonged induction period.The carbon monoxide treatment is effected at room temperature, following which hydrogen added, either alone or in admixture with further carbon monoxide, whereupon the reaction zone is heated to the desired reaction temperature and the reaction initiated. As examples of suitable sources of rhodium there are mentioned, interalia, rhodium nitrate, rhodium acetate and rhodium oxide. It is taught that the Group VIII metal, i.e. rhodium or iridium, may be complexed with the biphyllic ligand before being introduced into the reaction medium or the complex may be formed "in situ" by simply adding a compound of the metal and the biphyllic ligand directly into the reaction medium.

The specific reaction conditions used in the present invention result in efficient conversion of inorganic rhodium precursor to active complex rhodium catalytic species and the catalytic activity ofthe rhodium in the resulting catalyst approaches or is substantially equal to the activity of the rhodium in the catalyst species obtained by initiating the hydroformylation reaction in conventional manner, using both carbon monoxide and hydrogen during such initiation step, from a rhodium complex catalyst precursor, such as rhodium carbonyl triphenylphosphine acetylacetonate. However, the reaction conditions used in the present invention have not been found to result in any improvement in catalytic activity when the inorganic rhodium catalyst precursor is replaced by one of the above mentioned rhodium complex catalyst precursors.The benefit of the present invention is that, under the chosen reaction conditions, conversion of rhodium in the inorganic precursorto rhodium metal, i.e. a catalytically inactive species in a hydroformylation reaction, is at least partially or wholly avoided. Hence more efficient rhodium utilisation is achieved.

In the hydroformylation process of the invention there is contemplated the use of alpha-olefinic compounds, preferably those containing from 2 to about 20 carbon atoms. Such alpha-olefinic compounds contain a vinylidene group, i.e. CH2 = C , or preferably a vinyl group, i.e. CH2 = CH-. Generally speaking, compounds containing a vinyl group (e.g. butene-1) are more reactive than compounds containing a vinylidene group bound to two radicals other than hydrogen (e.g. iso-butylene) and it is for this reason that such compounds are preferred.Illustrative alpha-olefinic compounds include aliphatic olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1,octene-1, nonene-1,decene-1 andtheir homologues, as well as isomers thereof, such as 3-methylbutene-1, 2-ethylhexene-1, and iso-octene. Other alpha-olefinic compounds that can be considered for use in the process of the invention include aromatic olefins, such as styrene and allyl benzene, terpenes, such as myrcene, and d-limonene, and substituted a/pha-olefin compounds, such as allyl alcohol, allyl acetate, allyl methyl ether, allyl t-butyl ether, vinyl acetate, and diallyl ether.

Essential constituents of the liquid body are a triarylphosphine and an inorganic rhodium catalyst precursors The inorganic rhodium catalyst precursor may be dissolved in the liquid body or, more usually, suspended in it, preferably in finely divided form. The triarylphosphine is preferably present in excess of the amount required to complex with the rhodium of the inorganic catalyst precursor. Usually there is used an amount of triarylphosphine sufficient to provide in the liquid body after the carbon monoxide treatment at least 2 moles of free triarylphosphine, preferably at least about 10 moles of free triarylphosphine, per gram atom of rhodium.Even more preferably there is usually present an amount of triarylphosphine sufficient to provide at least about 50 moles or more, e.g. about 100 moles up to about 400 moles or more, of free triarylphosphine per gram atom of rhodium in the liquid body subsequent to the carbon monoxide treatment. If desired, further triarylphosphine can be added subsequent to the carbon monoxide treatment.

Typical triarylphosphine include tri-(naphthyl-1 )-phosphine, tri-(naphthyl-2)-phosphine, tri-o-, -m- or -p-to lyl phosph ine, tri-(p-phenyl phenylene)-phosphine, tri-(p-methoxyphenyl )-phosphine, and the like, but the preferred triarylphosphine is triphenylphosphine.

The inorganic rhodium catalyst precursor may be any precursor which is convertible under hydroformylation conditions in the presence of free triarylphosphine to a soluble rhodium complex hydroformylation catalyst. Examples of such precursors include Rh4(CO)12, Rh6(CO)16, Rh203, Rh203-5H2O, Rh203-8H2O, Rh203-10H2O, (Rh(OCOCH3)2)2-2H2O), Rh(NO3)3.2H2O, Rh(lll) 2,4-pentanedionate (i.e. Rh (C5H702)3) and the like.Although other inorganic rhodium compounds, such as Rhl3, RhCI3, RhCI3-3H2O and rhodium (III) sulphate (as Rh2(SO4)3-XH2O solution), have the potential to be converted to species exhibiting activity as hydroformylation catalyst, the use of such halogen-containing or sulphur-containing materials is generally best avoided since halogen-containing and sulphur-containing compounds generally act as catalyst poisons or inhibitors towards rhodium complex hydroformylation catalysts.

Besides the inorganic rhodium catalyst precursor and the triarylphosphine ligand the liquid body may contain also alpha-olefinic compound, aldehyde(s), aldehyde condensation product(s) and/or an inert solvent Typical inert solvents include alcohols such as n-or iso-butanol, glycols such as ethylene glycol or propylene glycol, ethers such as di-n-butyl ether ortetrahydrofuran, ether-alcohols such as ethylene glycol monomethyl and mono-n-butyl ethers, esters such as n-butyl and n-amyl acetate, and hydrocarbons such as benzene, toluene, xylene, hexane, cyclohexane, or heptane.Preferably, however, the process is conducted in the absence of an added inert solvent and the liquid body comprises, in addition to triarylphosphine and the inorganic rhodium compound or compounds, aldehyde product(s) and/or aldehyde condensation product(s) and, optionally alpha-olefinic compound.The nature of such aldehyde condensation products and a mechanism for their formation under hydroformylation conditions are described more fully, for example, in British Patent Specification No. 1338237 and in West German Offenlegungsschrift No.2715685, the disclosure of each of which is to be regarded as incorporated herein by reference. Suchaldehyde condensation products in admixture with product aldehyde or aldehydes provide a suitable solvent medium for the soluble rhodium active catalyst species and for the excess triarylphosphine and, since these aldehyde condensation products are formed as byproducts under hydroformylation conditions, it is not necessary to add any extraneous material to the reaction system.

During the carbon monoxide treatment step the liquid body is maintained under essentially hydrogen-free conditions. In other words the partial pressure of hydrogen is reduced to a low level, preferably below about 0.1 kg/cm2 absolute and is desirably effectively zero, e.g. about 0.01 kg/cm2 absolute or less. By reducing the hydrogen partial pressure to such low levels, it is postulated, the possibility of reduction of the inorganic rhodium catalyst precursor to rhodium metal during conversion to a rhodium complex catalyst precursor is prevented. Hence the efficiency of conversion of the inorganic rhodium catalyst precursor to active catalytic species is improved compared with procedures in which the precursor is converted to active catalytic species under hydroformylation conditions ab initio.

In the practice of the present invention the amount of the inorganic rhodium catalyst precursor may be so adjusted-in relation to the volume of the liquid body that, subsequent to the carbon monoxide treatment, the concentration of rhodium is suitable for effecting hydroformylation of the alpha-olefinic compound.

Generally speaking -it is preferred to effect hydroformylation at rhodium concentrations in the range of from about-20 ppm to about 1000 ppm or more calculated as rhodium metal, preferably from about 50 ppm up to about 250 ppm, whilst the free triarylphosphine concentration may range from about 0:5% by weight up to the solubility limit of the triarylphosphine, preferably from about 2% by weight up to about 25% by weight of free triarylphosphine.

Alternatively the liquid body used in the carbon monoxide treatment step may comprise only a fraction of the volume of the liquid reaction medium required for the hydroformylation step. In this case additional aldehyde(s), aldehyde condensation product(s), free triarylphosphine and/or inert solvent may be added as required to produce the desired volume of liquid reaction medium and the desired concentrations of rhodium catalytic species and free triarylphosphine. Yet again the liquid body that is subjected to the carbon monoxide treatment step may be larger than the volume of liquid reaction medium desired during the hydroformylation step. In this case evaporation of excess liquid may be effected in any convenient manner, e.g. in one or more falling film evaporators.

During the carbon monoxide treatment step the partial pressure of carbon monoxide may range from about 0.1 kg/cm2 absolute up to about 100 kg/cm2 absolute or more. Preferably, however, the carbon monoxide partial pressure lies in the range of from about 0.5 kg/cm2 absolute up to about 10 kg/cm2 absolute, e.g. in the range of from about 0.75 kg/cm2 absolute up to about 5 kg/cm2 absolute. In addition to carbon monoxide the a/pha-olefinic compound may be present during this step. It is generally preferred that the carbon monoxide treatment step should be carried out in the presence both of carbon monoxide and of the a/pha-olefinic compound to be hydroformylated.

The temperature during the carbon monoxide treatment may range from about 50"C up to about 160on; preferably, however, it is in the range of from about 90"C to about 130"C. The total pressure during the carbon monoxide treatment step is usually about 50 kg/cm2 absolute or less and typically is about 20 kg/cm2 absolute or less.-The partial pressure attributable to the alpha-olefinic compound, if present, is typically less than about 1.5 kg/cm2. If desired, the carbon monoxide treatment step can be carried out under the same pressure conditions that are later to be used during hydroformylation, the hydrogen to be used during hydroformylation being replaced during the carbon monoxide treatment step with an inert gas, such as nitrogen.

The liquid body is subjected to the carbon monoxide treatment step for a period sufficient to convert essentially all of the inorganic rhodium catalyst precursor to complex species. This period may range from a few minutes to several days, depending inter alia on the choice of catalyst precursor, the temperature, the total pressure, the carbon monoxide partial pressure, and the concenration of free triarylphosphine.

Typically this period ranges from about 30 minutes to about 5 hours.

The carbon monoxide treatment step can be effected in the hydroformylation reactor or in a separate vessel, in which latter case the treated liquid body is thereafter transferred to the hydroformylation reactor.

After completion of the carbon monoxide treatment step the liquid body can be cooled and its volume adjusted as necessary. Alternatively the resulting liquid reaction medium can be used immediately for hydroformylation. In this case the partial pressure of hydrogen is raised to the pressure desired'for hydroformylation and, if necessary, the a/pha-olefinic compound is introduced to the liquid reaction medium under an appropriate partial pressure thereof. The precise hydroformylation conditions selected depend on the alpha-olefinic compound used and, except in the case of ethylene when only a single product aldehyde is formed, on the desired n-/iso-product aldehyde ratio. Generally speaking the total pressure during hydroformylation is about 50 kg/cm2 absolute or less and usually it is about 20 kg/cm2 absolute or less.

Moreover the partial pressure attributable to the a/pha-olefinic compound is preferably about 1.5 kg/cm2 or less, whilst the total pressure attributable to hydrogen and carbon monoxide is typically less than about 30 kg/cm2, preferably less than 12 kg/cm2. Usually the carbon monoxide partial pressure during hydroformylation ranges from about 0.1 kg/cm2 up to about 1.5 kg/cm2, whilst the hydrogen partial pressure is from about 1.5 kg/cm2 up to about 7.5 kg/cm2.

The temperature during hydroformylation usually ranges from about 50"C up to about 1 60"C or more. The temperature should be at least as high as that required to effect hydroformylation but not so high as to destroy the catalyst. Usually the temperature will lie in the range of from about 70"C to about 140 C, e.g. in the range of from about 90"C to about 1300C.

Subsequent to the hydroformylation step the aldehydic product or products is or are recovered. Due to the involatility of the rhodium complex hydroformylation catalyst species distillation under atmospheric or reduced pressure can be used in many cases for product recovery. Water washing can be used in cases in which the aldehydic product or products is or are water-soluble.

Further teaching as to the conditions appropriate for hydroformylation can be found, for example, in United States Patent Specification No. 3527809. The hydroformylation step can be operated, particularly when utilising a C2 to C5 olefin as the alpha-olefinic compound, using the gas recycle system described in West German Offenlegungschrift No.2715685.

The invention is further illustrated in the following Examples.

Comparative Example A A 2,000 ml stainless steel autoclave fitted with a magnetically coupled stirrer and with a sparge tube for the supply of gases to the autoclave was charged with 500 ml of "Filmer 351", i.e. the trimer of iso-butyraldehyde, with 110 grams of triphenylphosphine and with 0.6 grams of rhodium carbonyl triphenylphosphine acetylacetonate. The autoclave was also provided with an off-take line for an overhead vaporous product and a recycle line for controlling the liquid volume in the autoclave. It could be heated electrically and could be cooled by means of an internal air cooling coil; by a combination of heating and cooling accurate temperature control could be achieved to within +0.1 C of a desired temperature.The liquid level in the autoclave could be detected by means of a pair of thermocouples positioned one just above and one just below the desired liquid level. An inlet mixture of hydrogen, carbon monoxide, propyiene and nitrogen could be supplied to the sparge tube. Product butyraldehyde distilled out of the autoclave and could be cooled and collected in a knock-out pot, from which it was recycled as necessary to the autoclave in order to maintain the desired liquid level. By measuring the vent gas flow rate and by gas chromatographic analysis of the product aldehyde collected and of the vent gas from the knock-out pot the n-/ iso-butyraldehyde ratio and the absolute rate of production of n-butyraldehyde could be calculated.

The carbon monoxide feed stream was purified by passage through a stainless steel coil at 200 C to destroy any carbonyls and was then mixed with propylene, hydrogen and nitrogen in the appropriate proportions before passing through individual tubes connected in series and containing respectively manganous oxide at room temperature, zinc oxide at 200"C, and active carbon at room temperature.

The autoclave was flushed with the gas mixture, pressurised to 17.6 kg/cm2 absolute, and heated to 110"C.

The inlet gas flows were controlled by means of valves in the individual supply lines from the gas cylinders so as to maintain constant outlet partial pressures of hydrogen, propylene and carbon monoxide in the ratio 60:40:10 at a total vent gas flow rate of approximately 1000 litres/hour (measured at STP). The total pressure was adjusted as required by appropriate control of the nitrogen partial pressure. The volume of liquid gradually increased to the desired level and was maintained at this level by recycle of product aldehyde from the knock-out pot. Once the volume of liquid had attained the desired value in the autoclave, operation at.

11 00C was continued for a period sufficient to ensure a constant aldehyde production rate over a minimum period of 6 hours. The reactor was then cooled and depressurised. The activity of this catalyst charge was assigned a value of 100 units on an arbitrary scale. The results are listed under Run No. 1 in Table 1 below.

The above procedure was repeated in further runs using, in place of the 0.6 gms of rhodium carbonyl triphenylphosphine acetylacetonate, an amount of one of the following compounds: Rh203-8H2O, Rh203-10H2O, and Rh(NO3)3 (in the form of a concentrated aqueous solution). In each run an amount of rhodium compound was used that contained an equivalent amount of rhodium metal to that used in Run No.

1. In each case hydroformylation occurred, demonstrating the production under the reaction conditions chosen of the desired rhodium-containing complex catalytic species. However in each case the catalytic activity was less than that observed in Run No. 1, even though the rhodium metal content and the liquid volume in the reactor were essentially the same in each run. The results are summarised as Runs Nos. 2 to 4 in Table 1.

In each of Runs Nos. 2 to 4 there was found to be a small amount of black solid suspended in the discharged reactor solution. It is thought that this was rhodium metal.

Examples 1 to 3 The procedure described above for Runs 1 to 4 of Comparative Example A was repeated except that the start up procedure was modified by using a mixture of carbon monoxide, propylene and nitrogen only (and no hydrogen) at a total pressure of 17.6 kg/cm2 absolute whilst the temperature of the- reactor was brought up to 110"C. The ratio of propylene to carbon monoxide in this mixture was 40:10. One hour after a reactor temperature of 110"C was attained hydrogen was admitted to the reactor and the flow of nitrogen was correspondingly reduced. With the total pressure still at 17.6 kg/cm2 absolute, the inlet gas flow rates were adjusted to produce the desired outlet gas composition (i.e. 60:40:10 hydrogen:propylene:carbon monoxide).' The results are set out in Table 2 below.

TABLE 2 Example No. Catalyst Precursor Total Rh content Active Rh content 1 Rh203.8H2O 100 106 2 Rh203.10H2O 100 100 3 Rh(NO3)3aq 100 97 Note: All Rh contents are expressed in arbitrary units It can be seen by comparison of Tables 1 and 2 that a significant increase of catalytic activity can be achieved, when using the precursors mentioned in Table 2, by utilising the start-up procedure of the invention, that is to say when starting-up under essentially hydrogen-free conditions. Examination of the reactor solutions at the end of the run in each of Examples 1 to 3 showed no evidence of any insoluble black material.

Comparative Example B The procedure used in Examples 1 to 3. was repeated using Rh(CO)(TPP)(acac). The total rhodium content was 100 arbitrary units. The measured catalyst activity was 88 arbitrary units on the same arbitrary scale as was used in Comparative Example A and in Examples 1 to 3.

Claims

1. A process for producing an aldehydic compound or compounds by hydroformylation of an alpha-olefinic compound with carbon monoxide and hydrogen comprising: establishing a liquid body containing a triarylphosphine and an inorganic rhodium catalyst precursor which is convertible under hydroformylation conditions in the presence of free triarylphosphine to a soluble rhodium complex hydroformylation catalyst; treating the liquid body with carbon monoxide under essentially hydrogen-free conditions at a temperature in the range of from about 50"C to about 160 C; supplying carbon monoxide, hydrogen and alpha-olefinic compound to a liquid reaction medium comprising material of the thus-treated liquid body;; maintaining the liquid reaction medium under pressure and temperature conditions conducive to hydroformylation of the alpha-olefinic compound; and recovering aldehydic product or products from the liquid reaction medium.

2. A process according to Claim 1, in which the liquid body contains a sufficient amount of triaryl phosphine to provide in the liquid body after the carbon monoxide treatment at least 2 moles of free triarylphosphine per gram atom of rhodium.

3. A process according to claim 2, in which the liquid body contains a sufficient amount of triarylphosphine to provide in the liquid body after the carbon monoxide treatment step from about 50 moles up to about 400 moles of free triarylphosphine per gram atom of rhodium.

4. A process according to any one of claims 1 to 3, in which the inorganic rhodium catalyst precursor is selected from: Rh4(CO)12, Rh6(CO)16, Rh203, Rh203.5H2O, Rh203.8H20, Rh203.10H2O, (Rh(OCOCH3)2)2.2H2O, Rh(NO3)3.2H2O, and Rh(lil) 2,4-pentanedionate.

5. A process according to any one of claims 1 to 4, in which the triarylphosphine in triphenylphosphine.

6. A process according to any one of claims 1 to 5, in which the liquid body further comprises aldehyde product(s) and/or aldehyde condensation product(s).

7. A process according to any one of claims 1 to 6, in which the liquid body further comprises an alpha-olefinic compound containing from 2 to about 20 carbon atoms.

8. A process according to any one of claims 1 to 7, in which the carbon monoxide partial pressure during the carbon monoxide treatment step ranges from about 0.5 kg/cm2 absolute up to about 10 kg/cm2 absolute.

9. A process for generating a complex rhodium hydroformylation catalyst which comprises: establishing a liquid body containing a triarylphosphine and an inorganic rhodium catalyst precursor which is convertible under hydroformylation conditions in the presence offreetriarylphosphineto a soluble rhodium complex hydroformylation catalyst; treating the liquid body with carbon monoxide under essentially hydrogen-free conditions at a temperature in the range of from about 50 C to about 160"C; and supplying carbon monoxide and hydrogen to a liquid reaction medium comprising material ofthe thus-treated liquid body.

10. A process according to claim 9, in which the liquid body contains a sufficient amount of triaryl phosphine to provide in the Jiquid body after the carbon monoxide treatment at least 2 moles of free triarylhosphine per gram atom or rhodium.

11. A process according to claim 10, in which the liquid body contains a sufficient amount of triarylphosphine to provide in the liquid body after the carbon monoxide treatment step from about 50 moles up to about 400 moles of free triarylphosphine per gram atom of rhodium.

12. A process according to any one of claims 9 to 11, in which the inorganic rhodium catalyst precursor is selected from: Rh4(CO)12, Rh6(CO)16, Rh203, Rh203.5H2O, Rh203.8H2O, Rh2O3.1 OH2O, (Rh(OCOCH3)2)2.H2O, Rh(NO3)3.2H2O, and Rh(lil) 2,4-pentanedionate.

13. A process according to any one of claims 9 to 12 in which the triarylphosphine is triphenylphosphine.

14. A process according to any one of claims 9 to 13 in which the liquid body further comprises aldehyde product(s) and/or aldehyde condensation product(s).

15. A process according to any one of claims 9 to 14, in which the liquid body further comprises an alpha-olefinic compound containing from 2 to about 20 carbon atoms.

16. A process according to any one of claims 9 to 15 in which the carbon monoxide partial pressure during the carbon monoxide treatment step ranges from about 0.5 kg/cm2 absolute up to about 10 kg/cm2 absolute.

17. A process-according to claim 1 conducted substantially as herein described wih particular reference to any one of Examples 1 to 3.

18. A process according to claim 9, conducted substantially as herein described with particular reference to any one of Examples 1 to 3.

19. Complex rhodium hydroformylation catalysts whenever prepared by a process according to any one of claims 9 to 16 or 18.

20. Aldehydic compounds whenever produced by a process according to any one of claims 1 to 8 or 17 or by using a rhodium complex hydroformylation catalyst according to claim 19.