JPS5828857B2 - Circulating hydroformylation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the hydroformylation of α-olefins with carbon monoxide and hydrogen in the presence of a rhodium catalyst.
The present invention relates to a method for producing aldehydes by the "hydroformylation" method.

J. Falbe, “Carbon Monoxide in Organ Synthesis”
ic 5 synthesis) J, [Springer Verlarg, New York (1970)], page 3, ``Hydroformylation is the process of unsaturated compounds (or It is a reaction between carbon monoxide and hydrogen.

” is the definition.

This method is also called the oxo method.

Until recently, all industrial hydroformylation reactions were catalyzed by cobalt carbonyl catalysts.

According to Falbe's book (page 70), Shell (5h
All industrially applied oxo processes, with the exception of one method developed by the German company Oberhausen (Oberhausen, Germany), in collaboration with BASF.
Ruhrchemi AG (sen)
e AG).

He states that current oxo facilities are operated continuously and generally "include the following: 1. Hydroformylation reactor; 2. Catalyst removal section; 3. Catalyst preparation and make-up section; 4. Aldehyde distillation. ,
5. Aldehyde hydrogenation reactor, 6° alcohol distillation.

It consists of each part.

” states that it is a thing. Shell's method differs in that it uses an improved cobalt catalyst.

The catalyst is prepared by combining a cobalt salt of an organic acid, a trialkylphosphine (eg, tributylphosphine), and an alkali such as KOH in a hydroformylation reactor.

This in-situ generated HCo(CO)3PR3 catalyst is r HCo
It is more thermally stable than (CO) 4 and therefore requires lower reactor pressures of about 100 atm compared to 200 to 300 atm in other processes.

(Falbe, supra, p. 73). The earliest oxo facilities were based on heterogeneous reactions of the Fischer-Trofsch catalytic type, but it was eventually discovered that the catalysis was homogeneous (Falbe, supra, p. 14).

Therefore, catalyst separation and recovery were essential steps in the oxo process.

This makes sense when the catalyst consists of the noble metal rhodium.

Cornils Hydrocarbon Processing
Although 1Rh compounds are more active than cobalt, as mentioned in June 1975, page 86, they are also much more expensive.

Cobalt requires about 20 DM/kg and rhodium 440 DM/kg.
00 to 72,000 DM/kg (1974
(September and February 1975).

” This shows the speculative nature of the rhodium price.

If the rhodium was 100% recovered and used at low metal concentration levels, the cost would not be significant.

Since economical recycling of rhodium is not possible, the utilization of unmodified Rh compounds has hitherto been limited, even when branched chain aldehydes are desired or when only Rh salts can carry out the oxo reaction. It has been avoided.

The reason for this is several ppm (1
) pm means 1 part per million) or several 100
The desired Rh concentration as low as ppm (cobalt 0.1 to 1% depending on the method of application) makes chemical, thermal or extractive treatment of metal carbonyl-containing oxo products even more difficult. Because I will.

Therefore, a number of specialized methods exist to remove traces of rhodium from the oxo product.

For example, adsorption on solids with a large surface area, distillative concentration of heavy targets of oxo synthesis, treatment with steam, halogens or carboxylic acids or others.

In addition to the oxo equipment, these methods often require an expensive recovery step for concentration.

The rhodium loss of only 1 ppm per kg of oxo product produced is about 0.04 to 0.07 DM/kg to the feedstock.
This will result in a loss of 1 kg.

(Compare with 0.02 DM/kg for Co catalyst.

)”. Based on the oxo process using an improved rhodium catalyst, Cornil et al.
The design of the proposed industrial equipment is shown in Figure 9.

They characterized that the catalyst must be recycled from the distillation column to the reactor.

On page 88 of their book, Cornil et al. state that due to the production of heavy target products, ``complete recirculation of rhodium via only the main circulation 9 results in the concentration of high-boiling components.

"It has said.

According to Cornil et al., p. 88, ``To avoid this, a portion of the residual oil in column 3 is continuously removed as a slip stream and distilled in column 6 to produce the ``aldol'' overhead distillate. cause

”.

They go on to say: ``If there is sufficient activity, the resid that has undergone two heat treatments at this point can be used for a second Rh reflux of 10
recycled to the reactor as

In the distillation in column 6, the intermediate and high-boiling by-products of the oxo synthesis are not removed.

This is because the high-boiling by-products cannot be separated from excess ligand.

The separation of the Rh complex from the intermediate boiling components takes place in column 7, which is fed with a slip stream of the bottom oil of column 6.

Since the bottoms of column 7 are often heat treated, their rhodium content is oxo-inert and therefore has to be prepared in an external replenishment step 8.

This rhodium is recycled to the reactor as a third Rh recycle 11.

However, at the same time, the excess of complexed and complexed ligands is lost.

The annual amount of rhodium passing through the third recirculation is approximately twice the initial Rh charge of the entire oxo system.

Cornil et al. further at page 89: ``A rhodium concentration of 0.1%, together with the amount of rhodium present at each different stage of the recirculation and recovered at each moment,
Requires high initial catalyst investment costs.

The relationship between initial catalyst investment for cobalt and for Rh-improved oxo units is 1:5 (1:3 depending on the price of Rh).

More important than the initial catalyst investment are rhodium leakage and loss of work.

Use precious metal catalysts. In comparison with other industrial processes, losses of 1 m9 of rhodium per kg of oxo product are considered realistic.

As a result, the raw material cost is approximately 0.04 to 0 depending on the price of Rh.
．． 07 DM/kg.

In order to equalize the raw material cost of the conventional oxo method catalyst,
"Rhodium losses must be reduced to below 0.3 ppm per liter."

A method similar to that described by Cornil et al. is described in British Patent No. 1,228,201.

In the process described in this patent, recycling of the catalyst is critical to the process, except when the catalyst is on a solid support in a fixed bed mode.

However, as pointed out earlier by J. Falbe, the reaction is in fact a homogeneous reaction, and by depositing the rhodium on an inert support, considerable catalyst losses must be expected. .

In GB 1312076 a different technique is adopted for the separation of the catalyst from the reaction products.

This technique removes the overhead of the gaseous product stream, separates the aldehyde product from the overhead by fractional distillation, and then separates the complex catalyst, aldehyde, and high-boiling residue from the reactor. A portion of the high-boiling residue and the aldehyde are removed through the membrane by passing the liquid stream under reaction pressure over the surface of the membrane and removing the catalyst-containing liquid stream. including recycling the remainder of the liquid stream to the reactor.

British Patent Provisional Specification No. 23678 (1969) states:
This illustrates the fact that in homogeneous catalysis of the type described here, removing the catalyst from the reaction products for recycling is a difficult operation.

It is mentioned in that specification that the catalyst can be recycled in the heavy residue obtained after distilling the main reaction product at the expense of catalyst losses.

To further illustrate the difficulties with catalyst recovery from oxo reactions, Olivinyl (01ivier) and Snyder (5ny
der) US Pat. No. 3,539,634.

This specification passes the separated reaction product heavy and/or residual oil containing catalyst through an inert bed;
It states that the catalyst is extracted from the inert bed with a reaction solvent.

The above process requires that the solvent be of an extractive type and at the same time requires an infinite extraction capacity to ensure no catalyst loss.

Described herein is a process for the preparation of the above oxo products by hydroformylation of alpha-olefins using an improved rhodium catalyst, which for all practical purposes avoids catalyst loss over time. Describe how to do so.

The process of the invention is a continuous process for the production of aldehydes by hydroformylation of alpha-olefins having from 2 to about 5 carbon atoms.

It consists of an olefin, carbon monoxide and hydrogen fed to it, aldehyde products and high-boiling aldehyde condensation products continuously formed therein, a soluble rhodium catalyst complexed with carbon monoxide, and a triarylphosphine. and establishing a liquid body of a homogeneous mixture.

The amount of triarylphosphine fed to the liquid is at least equal to 10 moles for each mole of rhodium metal fed to the liquid.

The liquid is supplied with a gaseous recycle stream consisting of hydrogen and olefins, and supplementary amounts of carbon monoxide, hydrogen and olefins are supplied to the liquid.

The temperature of the liquid is maintained at about 50 DEG C. to about 140 DEG C., and the total pressure is maintained below about 28 kg per 'J-crA (about 400 pounds per square inch) absolute pressure.

The partial pressure of carbon monoxide in the reaction is approximately 3.5 per crA.
kg (about 50 pounds per square inch) absolute pressure, and the partial pressure of hydrogen is about 14 kg (about 200 pounds per square inch) absolute pressure per crit.

olefins, hydrogen, and vaporized aldehyde products;
and removing from the liquid a vaporous mixture with vaporized aldehyde condensation product in an amount substantially equal to the rate of formation in the liquid, thereby maintaining the amount of the liquid at a preset value. .

An aldehyde product and an aldehyde condensation product are recovered from the vaporous mixture.

The vaporous mixture forms a gaseous recycle stream and is fed to the liquid as described above.

R6L, Pruett (published on September 8, 1970)
Pruett) and J.A. Smith.
U.S. Pat. No. 3,527,809 titled "Hydroformation Process" produces aldehydes in high yield, low temperature and pressure, with excellent catalyst stability, and which has three or more carbon atoms. Significant improvements in the hydroformylation of α-olefins are disclosed that produce aldehyde mixtures with high normal to iso (or branched chain) isomer ratios in the case of α-olefins.

This method uses a variety of rhodium complex compounds for the hydroformylation of olefins with hydrogen and carbon monoxide under specific combinations of variables.
In the presence of selected triorganophosphorous ligands,
It effectively acts as a catalyst.

The variables are (1) the rhodium complex catalyst, (2) the olefin feedstock, (3) the triorganophosphorus ligand and its concentration, (4) the relatively low temperature range, and (5) the hydrogen and carbon monoxide and (6) limitations on the partial pressure of carbon monoxide.

The process of the present invention employs the parameters of the invention of the '809 patent, and experience from the operations described herein ensures that the invention represents significant advantages in the oxo technology community. be.

Among the catalysts described in said U.S. patent are carbon monoxide and triarylphosphorus ligands, especially triphenyl.
There are compounds containing rhodium complexed with triarylphosphine ligands, exemplified by phosphine (TPP).

Representative active catalyst species have the formula RhH(Co)CP(C6H
5) 3) Rhodium hydride carbonyl tris(triphenylphosphine) with s.

The method uses an excess of notriorganophosphorus ligand.

As is known in the current literature, the active rhodium catalyst can be preformed and then introduced into the reaction mixture medium, or alternatively the active catalyst species can be prepared in situ during the hydroformylation reaction. can do.

An example of the latter is the introduction of (2,4-pentanedionato)dicarbonylrhodium(I) into the reaction medium, and under operating conditions in the medium, the (2,4-pentanedionato)dicarbonyl rhodium(I). Rhodium(I) can be reacted with a triorganophosphorous ligand such as triphenylphosphine to obtain rhodium hydridocarbonyl-tris().
Active catalysts such as IJ phenylphosphine) can be produced.

If the process of said US Pat. No. 3,527,809 uses a normally liquid inert organic solvent that is not a reaction product or reactant in the process, the product mixture may eventually be heated to room temperature or e.g. 80°C. At such selected operating temperatures, its properties are either slightly cloudy or have significant precipitation.

Elemental analysis showed that the solid (cloudy or precipitated) contained rhodium.

In some cases it appears that "polymerized" rhodium complex solids have been formed; in other cases the solids appear to resemble the active form of the rhodium complex species.

Such solids can be lost from the system, for example by depositing in small cracks, eyes, or plug valves.

As stated above, even small losses of rhodium cannot be tolerated in truly efficient industrial oxo operations.

Another disadvantage of introducing the rhodium species as a solution into an external organic liquid as described above is that it may clearly be necessary to separate the oxygenated products formed in the reaction from the organic liquid. be.

Since the oxo reaction produces aldehydes and high boiling aldehyde condensates which are removed to maintain solvent concentration as mentioned above, removal of said condensation products by distillation affects the solvent, i.e. even if all of it is If not, some of it is distilled and Rh values are contained therein.

It is advantageous to first introduce an external catalyst solution in organic liquid into the oxo reaction zone.

However, such industrial oxo operations require continuous or interval (intermittent) introduction of catalyst.

The catalyst may be fresh catalyst, regenerated catalyst, or catalyst contained in the recycle stream, but such practices result in catalyst losses.

Japanese Patent Publication No. 51-1687 uses a high-boiling liquid aldehyde condensation product as the primary solvent for the catalyst.

As a result, no removal of solvent from the catalyst was required other than a small purge flow to reduce the concentration of condensation products and poisons to the reaction.

As a result, hydroformylation of olefins containing 3 carbon atoms or higher maintains a high ratio of the normal to yne isomer distribution of aldehydic products over long periods of time, while maintaining substantial amounts of the above-mentioned Continuous recycling of rhodium species in the condensation product did not result in extensive precipitation of rhodium in one form or the other.

During long-term operation, no obvious loss in catalyst life was observed.

The use of a condensation product as described above as a rhodium-containing catalyst dissolution medium is advantageous from the point of view that the extraneous organic liquid can be completely excluded from the hydroformylation zone if desired. .

To provide the advantages listed in said U.S. Pat. No. 3,527,809, the use of an excess of free triorganophosphorous ligand in a reaction medium containing dissimilar high-boiling condensation products can be Even in continuous operation over a long period of time, the activity or solubility of the rhodium complex catalyst is not disturbed.

Since these condensation products are formed in situ, the process described above is economically very favorable.

Continuous recycling of rhodium species dissolved in the high-boiling liquid condensation product has been found to be disadvantageous after substantial repeated use.

Constant movement of the catalyst leads to some degree of catalyst loss; in liquid recycle, some of the catalyst is outside the reactor, requiring significant catalyst volume; the rate of residue formation is at a significant level. and must be removed, thus affecting the stability of the catalyst in such cases and making it difficult to control the pressure of the carbon dioxide gas;
The nature of recirculation results in heat losses because hot liquid is constantly moved through the system; and increases the tendency for small amounts of oxygen leakage (which has been found to be detrimental to the process). .

Hydroformylation reactions using nonvolatile catalysts such as hydridocarbonyltris(triphenylphosphine)rhodium(I) in the liquid phase convert aldehyde reaction products and their high-boiling condensation products at reaction temperatures and pressures. by distilling off the catalyst-containing liquid (or solution), and by condensing the aldehyde reaction product and the condensation product from the off-gas from the reaction vessel in a product recovery zone; In a further advantageous manner, by recycling unreacted feed materials (e.g. carbon monoxide, hydrogen and/or alpha-olefins) from the product recovery zone to the reaction zone,
Furthermore, it has been confirmed that the process can be carried out using a simple device.

Furthermore, by recycling a sufficient amount of gas from the product recovery zone to the reaction zone, combined with make-up starting material, reactions can be carried out using α-olefin starting materials and C2 to C5 olefins. A mass balance is achieved in the liquid in the vessel such that substantially all high-boiling condensation products resulting from self-condensation of the aldehyde products are removed at a rate at least as great as their rate of formation. can be removed from the reaction zone at a rate of

If the gas recirculation is insufficient, the condensation products will accumulate in the reaction vessel in a different manner.

According to the present invention, the method for producing aliphatic aldehydes having 3 to 6 carbon atoms comprises adding an aliphatic α-olefin having 2 to 5 carbon atoms together with hydrogen and carbon monoxide to the liquid form at the temperature and pressure mentioned above. a catalyst dissolved in the body, which is substantially non-volatile and effective for the hydroformylation of alpha-olefins;

), a vapor phase is continuously withdrawn from the reaction zone, the vapor phase is passed through a product separation zone, and the liquid aldehyde-containing product in the product separation zone is separated from the gaseous unreacted product by condensation. separating from the starting material and then recycling the gaseous unreacted starting material from the product separation zone to the reaction zone.

Preferably, the gaseous unreacted starting material plus make-up starting material is recycled at a rate at least as great as that required to maintain mass balance in the reaction zone.

The process according to the invention contemplates the use of alpha-olefins having 2 to 5 carbon atoms, preferably 2, 3 or 4 carbon atoms.

Such alpha olefins have a terminal ethylenic carbon-to-carbon bond, which may be a vinylidene group, i.e., CH2-C, or a vinyl group, i.e., CH2-CH-.

).

They may be straight or branched and may contain groups or substituents that do not substantially interfere with the course of the method.

Examples of α-olefins are ethylene, propylene, l
Butene, imbutylene, 2-methyl-1-butene, 1-
Such as pentene.

This reaction is advantageously conducted at a temperature of about 50 to about 14.00 g.

Temperatures in the range of about 60°C to about 120°C are preferred and are usually conveniently operated at temperatures of about 90°C to about 115°C.

A feature of the invention is that the total pressure required to carry out the industrial process is low.

Total pressures as low as about 28 kg/ca absolute (about 400 psia) or less, even 1 atmosphere and less, can be employed with effective results.

Total pressure 24.5 kg/crA absolute pressure (350 psia
) The following are preferred.

This reaction can be conducted at a pressure within the range of about 7 to about 21 kg/c4 absolute (about 100 to about 300 psia).

The partial pressure of carbon monoxide is an important factor in the method of the invention.

When using complex rhodium catalysts, there is a clear decrease in the isomer ratio of the normal to iso aldehydic products as the partial pressure attributable to carbon monoxide approaches a value of about 75% of the total gas pressure (CO+H2). was observed to occur.

It is generally preferred that the partial pressure attributable to hydrogen is 25 to 95% or more based on the total gas pressure (CO+H2).

It is common to employ total gas pressures such that the partial pressure attributable to hydrogen is significantly greater than that attributable to carbon monoxide, e.g. the ratio of hydrogen to carbon oxide is between 3:2 and 100:1. It is advantageous.

In daily practice, this ratio is about 62.5:1 to about 12.5:1.
5:1 is fine.

The partial pressure of the α-olefin in the reaction zone is about 3 of the total pressure.
It may be up to 5%, preferably in the range 10 to 20% of the total pressure.

In preferred operation, the CO partial pressure is typically about 3.5
kg/crj, absolute pressure (about 50 psia), and most preferably does not exceed about 2.45 kg/csl absolute pressure (about 35 psia).

The preferred hydrogen partial pressure is about 14 kg/crA absolute pressure (about 2
00 psia) or less.

For example, if H2 partial pressure is 8.75kg10A absolute pressure (12s
psia) and C0 partial pressure is 0.14 to 0.7 kg
/c absolute pressure (2 to 10 psia) can be varied.

The catalyst may be any non-volatile catalyst that is effective for the hydroformylation of alpha-olefins, but is not disclosed in the aforementioned U.S. Pat. No. 352 for rhodium-based catalysts.
In view of its known advantages as taught in '7809, improved forms of rhodium constitute the most preferred catalysts.

When C3 or higher olefins are used as starting materials, it is preferred to select a catalyst that provides a high normal-to-yne ratio in the aldehyde product mixture.

The general class of rhodium catalysts described in the aforementioned US Pat. No. 3,527,809 can be used in the practice of this invention.

A preferred catalyst of the present invention is comprised of rhodium complexed with carbon monoxide and a triarylphosphine ligand.

The most desirable catalysts are hydrogen, carbon monoxide, and tria, which do not contain halogens such as chlorine, and which complex with rhodium metal to produce a catalyst that is soluble in the liquid described above and stable under the reaction conditions. It contains lylphosphine.

Examples of triarylphosphine ligands include triphenylphosphine, I-linapthylphosphine, tritolylphosphine, tri(p-biphenyl)phosphine, tri(p-methoxyphenyl)phosphine, tri(m-chlorophenyl)-phosphine, p-N-N-dimethylaminophenyl bisphenylphosphine, and other analogs.

Triphenylphosphine is a preferred ligand.

As previously pointed out, the reaction is carried out in a liquid containing an excess of free triarylphosphine.

Rhodium is e.g. a stable crystalline solid, rhodium hydridocarbonyl-tris(triphenylphosphine), R
Preferably, it is introduced into the liquid as a pre-bottomed catalyst such as hH(CO)(PPh3)s.

The rhodium can be introduced in the form of a precursor that is converted into a catalyst in situ.

Examples of such precursor forms include rhodium carbonyltriphenylphosphine acetylacetonate,
Rh203, Pb+(Co)12, Rh6(Co)t6
and rhodium dicarbonylacetylacetonate.

Both the catalytic compounds and their formulation which provide the active species in the reaction medium are known in the art [Brown (
Journal of the Chemical Society (Brown) etc.
emicsl 5ociety), 1970, 275
See pages 3-2764].

Ultimately, the rhodium concentration in the liquid can range from about 25 to about 1200 ppm rhodium, calculated as free metal, with triarylphosphines ranging from about 0.5 to about 1,200 ppm based on the weight of the total reaction mixture. It is present in a range of about 30% by weight and in an amount sufficient to provide at least 10 moles of free triarylphosphine per mole of rhodium.

The meaning of free ligand is taught in US Pat. No. 3,527,809, GB 1,338,225, and Brown et al., supra, pages 2759 and 2761.

Generally, the optimum catalyst concentration depends on the concentration of the alpha-olefin, such as propylene.

For example, the greater the concentration of propylene, the lower the catalyst concentration that can be used to achieve a given conversion rate to aldehyde product in a given size reactor.

Recognizing that partial pressure and concentration are related, employing a higher propylene partial pressure will increase the proportion of propylene in the off-gas from the liquid.

It may be necessary to purge a portion of the gas stream from the product recovery zone prior to recycling to the liquid to remove some of the propane that may be present. The higher the propylene content in the off-gas, the more propylene will be lost in the propane purge stream.

Therefore, it is necessary to balance the economic value of propylene loss in the propane purge stream against the capital savings associated with lower catalyst concentrations.

An unexpected advantage of the improved Rh-catalyzed process of the present invention is that all Co-catalyzed processes produce significant amounts of diethyl ketone in the hydroformylation of ethylene. , the process of the present invention does not produce measurable amounts of diethyl ketone.

The process of the present invention comprises a reaction zone containing one of the aforementioned rhodium complex catalysts and a high-boiling liquid aldehyde condensation product (which is rich in hydroxyl compounds, as defined below) as a solvent therefor. Preferably, it is carried out in the liquid phase.

As used herein, the term "high-boiling liquid aldehyde condensation product" means, as illustrated below in a series of formulas including n-butyraldehyde as a model,
It refers to the complex mixture of high-boiling liquid products resulting from the condensation reaction of the C3 to C6 alkanal products of the process of the invention.

Such condensation products can be preformed or generated in situ in the Okine process.

The rhodium complexes are soluble in the relatively high boiling liquid aldehyde condensation products and exhibit a high degree of catalyst life over long periods of continuous hydroformylation.

Initially, the hydroformylation reaction can be carried out in the absence or in the presence of small amounts of high-boiling liquid aldehyde condensation products as solvent for the rhodium complex.

Alternatively, the reaction can be carried out in the presence of the condensation product in amounts up to about 70% by weight, or even as much as about 90% and more, based on the weight of the liquid.

The small amount of the high-boiling liquid aldehyde condensation product may be as small as 5% by weight, preferably 15% by weight or more, based on the weight of the liquid.

■■ For example, in the hydroformylation of haflopyrene, two types of products are possible.

That is, normal-butyraldehyde and iso-butyraldehyde.

A high normal-to-yne ratio of butyraldehyde is desirable since normal-butyraldehyde is the more industrially interesting product.

However, aldehyde-based products, which are themselves reactive compounds, condense slowly even in the absence of catalysts and at relatively low temperatures to form high-boiling liquid condensation products.

Therefore, various aldehyde products are included in the various reactions described below using n-butyraldehyde for illustrative purposes.

Furthermore, Aldol ■ can undergo the following reaction be.

In the equation explained above, the names in parentheses, 1 aldol■, substituted acrolein■, trimer■, trimer■,
Dimer V, tetramer ■, and tetramer ■ are merely for convenience.

Aldol ■ is produced by aldol condensation, trimer ■ and tetramer ■ are produced by Chisienko reaction,
Trimer 2■ is produced by a transesterification reaction, and trimer 2 and tetramer 2 are produced by a disproportionation reaction.

The major condensation products are trimer (1), trimer (2), and tetramer (2), with small amounts of other products present.

Therefore, the condensation product as described above is, for example, a trimeric two-body ■
, contains substantial amounts of hydroxyl compounds as evidenced by trimer ■ and tetramer ■.

■■ A similar condensation product is produced by self-condensation of iso-butyraldehyde.

Further, by condensation of one molecule of normal-butyraldehyde and one molecule of iso-butyraldehyde, more types of compounds are produced.

A molecule of normal-butyraldehyde can be aldolized by reaction with a molecule of iso-butyraldehyde in two different processes to produce two different types of aldol ■ and aldol ■, so butyl A total of up to four aldols can be produced by condensation reactions of normal/iso mixtures of aldehydes.

Aldol ■ is further condensed with isobutyraldehyde to produce a trimer of the isomer of trimer ■, aldol ■ and ■, and the corresponding aldol X produced by self-condensation of two molecules of isobutyraldehyde is normal- Further reaction with either butyraldehyde or isobutyraldehyde produces the corresponding isomeric trimer.

These trimers further react in a similar manner to form a trimer dish,
A complex mixture of condensation products is formed.

Substituted acrolein ■ and its isomers, e.g.
It is highly desirable to keep concentrations low, such as below % by weight.

It has been found that substituted acrolein (1), especially one designated 2-ethyl-3-propyl acrolein (EPA), forms in situ together with other condensation products and interferes with the catalyst activity.

The ultimate effect of EPA or similar products is that all processes in which EPA is present in an amount of about 5% or more (even about 1% or more) by weight based on the weight of the liquid are economical. The goal is to reduce the hydroformylation rate to the extent that it is disadvantageous.

In a preferred form of the process of the invention, the high-boiling liquid condensation product used as solvent is introduced into the reaction zone and is preformed before starting the process.

Alternatively, at the beginning of the process, for example aldol I
can also be added to allow other products to accumulate as the reaction progresses.

In some cases, especially at the beginning of the process, it may also be desirable to use small amounts of organic co-solvents, such as toluene or cyclohexanone, which are normally liquid and are inert during the hydroformylation process.

These organic co-solvents can be replaced in the liquid phase within the reaction zone by the high-boiling liquid aldehyde condensation product as the reaction progresses.

The liquid contains, in addition to the catalyst and optionally added diluents such as the free ligand triphenylphosphine, an aldehyde or a mixture of aldehydes and aldols, trimers, diesters, etc. derived therefrom.

The relative proportions of each product in the solution are controlled by the amount of gas passed through the solution.

If the amount of this gas is increased, the equilibrium aldehyde concentration will decrease,
The rate of removal of by-products from the solution is increased.

The by-products include the high boiling liquid aldehyde condensation products.

Decreasing the aldehyde concentration will reduce the rate of formation of the byproduct.

The dual effect of increased removal rate and decreased production rate means that the mass balance in the by-products within the reactor is very sensitive to the amount of gas passing through the liquid. .

The gas cycle typically includes make-up amounts of hydrogen, carbon monoxide, and alpha-olefins.

However, the most significant factor is the amount of recycle gas returned to the liquid.

This is because the amount of gas determines the extent of the reaction, the amount of products produced and the amount of by-products removed (as a result).

Operation of the hydroformylation reaction with a given flow rate for the olefin and synthesis gas and a low total recycle gas amount below the critical threshold rate results in a high equilibrium aldehyde concentration in solution and therefore a high by-product acid concentration. A generation rate occurs.

The rate of removal of byproducts in the vapor phase effluent from the reaction zone (liquid) under conditions such as those described above will be low.

Because the low flow rate of vapor phase effluent from the reaction zone
This is because it only results in relatively low rates of by-product transport.

The net effect is an increase in by-products in the liquid solution, which results in an increase in the volume of the solution with a consequent loss in catalyst production.

Therefore, when operating the hydroformylation process at low gas flow rates as described above, a purge must be removed from the solution in order to remove by-products and therefore maintain a mass balance throughout the reaction zone. It won't happen.

However, if the flow rate of gas through the reaction zone is increased by increasing the recirculation rate of the gas, the aldehyde content of the solution decreases, the rate of byproduct formation decreases, and the reaction The rate of removal of byproducts in the vapor phase effluent from the zone is increased.

The net effect of this change is to increase the proportion of byproducts removed with the vapor phase effluent from the reaction zone.

If the gas flow rate through the reaction zone is further increased by further increasing the gas recirculation rate, the by-products will be produced in the vapor phase effluent from the reaction zone at a rate equal to the rate at which they are produced. conditions are created and a mass balance across the reaction zone is thus established.

This is the critical gas recirculation threshold rate, which is the preferred minimum gas recirculation rate employed in the process of the present invention.

If the process is operated at a gas recirculation rate above this gas recycle threshold rate, the volume of the liquid in the reaction zone will tend to decrease and therefore the gas recirculation rate will exceed this threshold rate. In order to maintain a constant volume of the liquid phase in the reaction zone, some amount of the crude aldehyde by-product acid mixture should be returned from the product separation zone to the reaction zone.

The gas recirculation threshold rate can be found by trial and error for a given olefin and synthetic gas (mixture of CO and hydrogen) feed rate.

Operating at a recirculation rate below a critical threshold rate will increase the volume of the liquid phase over time, operating at the threshold rate will keep the volume constant, and operating at or above the threshold rate will increase the volume of the liquid phase over time. If so, the volume will decrease.

The critical gas recirculation threshold rate is 1 at the reaction temperature.
It can be calculated from the vapor pressure of the aldehyde or aldehydes and each by-product present.

A process operating at or above the threshold gas recirculation rate produces by-products in a gaseous vapor withdrawn from the reaction zone containing the liquid. is removed at the same rate or faster than the reaction zone and therefore does not accumulate in the liquid phase within the reaction zone.

Under such circumstances, there is no need to purge the catalyst-containing liquid from the reaction zone to remove by-products.

This has the advantage of not removing the catalyst from the reaction zone except for long periods when the catalyst needs to be renewed, thus reducing the chance of loss of expensive catalyst due to leakage incidents.

Furthermore, high temperature treatment of the catalyst-containing purge solution for removing by-product oxides is not required, thus extending the life of the catalyst.

Experience to date indicates that catalyst renewal of any kind is not necessary for at least one year of operation.

The residence time of the aldehyde in the reaction zone can vary from about several minutes to several consecutive hours.

It is also well recognized that these variables depend on the reaction temperature, the choice of alpha-olefin, catalyst and ligand, the concentration of the ligand, the total pressure of the synthetic gas and the partial pressure due to its components, It is also influenced to some extent by other factors.

For practical periods of time, the reaction is carried out for a period of time sufficient to hydroformylate the alpha or terminal ethylenic bond of the alpha-olefin.

A by-product of the hydroformylation process of the present invention is an alkane produced by hydrogenation of an alpha-olefin.

Thus, for example, in the hydroformylation of propylene, the by-product is propane.

It is therefore preferred to take a purge stream from the gas recycle stream from the product recovery zone to remove propane and prevent it from accumulating within the reaction system.

This purge stream will contain, in addition to the unwanted propane, unreacted propylene, some inert gas introduced into the feed, and a mixture of carbon monoxide and hydrogen.

This nohage stream can, if desired, be subjected to conventional gas separation techniques, such as cryogenic techniques, to recover propylene.

However, it is usually uneconomical to do so and the purge stream is typically used as fuel.

The main components of the recycle gas are hydrogen and propylene.

However, if no CO is consumed in the reaction, this per-W)CO is also part of the recycle gas.

Normally the recycle gas will contain alkanes despite purging prior to recycle.

It is appreciated that the process according to the invention can be operated continuously over long periods of time without removing any catalyst-containing liquid from the reaction zone.

However, from time to time it may be necessary to regenerate the rhodium catalyst.

In this case, a purge stream is removed from the reactor through a normally closed valve and fresh catalyst is added to maintain the catalyst concentration in the liquid, or the removed catalyst is regenerated.

After removal from the liquid in the reactor, the vapor effluent is fed to a product separation zone where the aldehyde or aldehydes are removed and, if appropriate, the aldehydes are separated from each other, and To recover the high-boiling liquid aldehyde condensation product, the mixture of one or more aldehydes, their dimers, trimers and other high-boiling liquid condensation products is processed using conventional techniques such as distillation. Processed by

The α-olefins used as starting materials in this process must be rigorously purified to remove the inherent potential oxo catalyst poisons (see Falbe, supra, pp. 18-22).

The carbon monoxide and hydrogen required for the process can be produced by partial oxidation of suitable hydrocarbon feedstocks, such as naphtha, but these can also be rigorously purified to remove impurities that are potential catalyst poisons. must be removed.

The invention will be further explained with reference to the accompanying drawings, which diagrammatically show process steps suitable for carrying out the method of the invention.

In [, the stainless steel reactor 1 is provided with one or more disk impellers 6 having vertically mounted blades and rotated by a shaft 7 by a suitable motor (not shown).

A cylindrical sparger 5 is installed below the impeller 6 to supply alpha-olefins and synthesis gas plus recycle gas.

The sparger 5 includes a plurality of sparges having a size sufficient to supply a sufficient gas flow rate into the liquid near the impeller 6 and supply a desired amount of reactant into the liquid. It is provided with a hole.

The reactor is also equipped with a steam jacket (not shown) and an internal cooling coil (not shown) for raising the contents of the reactor to reaction temperature at the start of the reaction.

The vaporous product effluent from the reactor 1 is taken off via conduit 10 to a separator 11 in which a misting pad l is removed.
1a to return some amounts of aldehyde and condensation products and to prevent any possibility of catalyst being carried away.

The reactor effluent passes through conduit 13 to condenser 14 and then through conduit 15 to catchpot 16 where the aldehyde product and any by-products are condensed from the off-gas (effluent). .

Condensed aldehyde and by-products are removed from catchpot 16 via conduit 17.

The gaseous material passes via conduit 18 to a separator 19 containing a fogging pad and then to a recirculation conduit 20.

Recycled gas is removed by conduit 21 to conduit 8 from which purge is drawn through conduit 22 to adjust the saturated hydrocarbon content.

The remainder, and the main part of the gas, passes through conduit 8 to conduit 4.
can be recirculated.

A make-up reactant feedstock is supplied to conduit 4 through conduits 2 and 3.

All reactants combined are fed to reactor 1.

Compressor 26 assists in transporting recycle gas.

Fresh catalyst solution can be added to the reactor 1 via conduit 9.

The single reactor 1 can of course be replaced by a plurality of reactors in parallel.

The crude aldehyde product in conduit 17 can be processed by conventional distillation to separate the various aldehydes and condensation products.

If necessary, for the purpose of maintaining the liquid level in the reactor 1, a portion of the crude is recycled through the conduit 23 and then fed to a point above the impeller 6, as indicated by the dashed line 25. be able to.

The following examples are intended to provide a detailed explanation of the invention, but are not intended to limit the invention.

The reactor used in the example had a diameter of 120 mm and was installed directly below the impeller.
cIrL (4 feet 1-), internal diameter 390CrrL (with internal diameter 20CIrL (8 inches) cylindrical spreader)
13 feet), height 720crrL (24 feet)
It is a cylindrical container made of stainless steel having the dimensions shown in the accompanying drawings.

The sparger has a plurality of holes for supplying reactants.

The reaction conditions for adopting the process shown in the attached drawings are shown in Tables 1 and 2.
Shown in the table.

The pressure of the reactor is approximately 28 kg/crA absolute pressure (approximately 400
psia) or less, and the carbon monoxide partial pressure is approximately 3°5
kg/cni absolute pressure (approximately 50 psia) or below, and the hydrogen partial pressure is approximately 14 kg/cni absolute pressure (approximately 20 psia).
0 psia) or less.

The composition of the product from conduit 17 is as follows.

Substantially the above procedure has proven to be the most effective technique for producing propionaldehyde from ethyl/one.

[Brief explanation of the drawing]

The accompanying drawings show process diagrams of preferred embodiments of the invention. In the figure, 1... Reactor, 5... Distributor, 6... Impeller, 7... Shaft, 11... Separation Container, 11a...Four fog removal pads,
14. Condenser, 16. Catch pot, 19. Separator, 20. Recirculation conduit, 26. Compressor O.

Claims (1)

[Scope of Claim] 1. A process for the continuous production of aldehydes by hydroformylation of α-olefins having 2 to about 5 carbon atoms, comprising: an olefin, an aldehyde product continuously produced therefrom and a high boiling point; an aldehyde condensation product and a soluble rhodium catalyst complexed with carbon monoxide and triarylphosphine;
mol of free triarylphosphine, and supplying to said liquid a gaseous recycle stream containing hydrogen, an alkane, and said olefin as major components, and carbon monoxide; A replenishing amount of hydrogen and olefin is supplied to the liquid, and the temperature of the liquid is controlled to be about 50 to about 140°C, the total pressure is about 28 kg/c4 absolute pressure (about 400 psia) or less, and the carbon monoxide content is reduced. The pressure is approximately 3.5 kg/crA absolute pressure (approximately 50 psia) or less, and the hydrogen partial pressure is approximately 141 y/cm.
crA absolute pressure (approximately 200 psia) or less, condensing the olefin, hydrogen, and vaporized aldehyde product from the liquid body in an amount substantially equal to the rate of production in the liquid body. removing the vaporous mixture comprising the product, thereby maintaining the volume of the liquid at a predetermined value, and then recovering the aldehyde product and the aldehyde condensation product from the vaporous mixture, and recovering the aldehyde product and the aldehyde condensation product from the vaporous mixture. Said method, characterized in that a circulating flow is formed. 2. The method according to item 1 above, wherein the α-olefin is propylene. 3. The gaseous recycle stream contains hydrogen, alpha-olefins,
2. The method of claim 1, comprising carbon monoxide. 4. The gaseous recycle stream contains hydrogen, alpha-olefins,
3. The method according to item 2, comprising carbon monoxide. 5. The method according to item 2 above, wherein the triarylphosphine is triphenylphosphine. 6 Total pressure is 24.5 kg/crA absolute pressure (350p
2. The method according to item 1, wherein: sia) or less. 7. The method of claim 2, wherein the molar ratio of hydrogen to carbon oxide is between 3:2 and 20:1. 8. The method of item 2 above, wherein the temperature is about 60°C to about 120°C. 9. The method according to item 1 above, wherein the α-olefin is ethylene. 10. The method according to item 1 above, wherein the α-olefin is 1-butene.