JPS63218640A - Hydroformylation of olefin - Google Patents

Abstract

PURPOSE:To react on olefin while removing high-boiling by-products accumulated in a catalytic solution recycled to a reaction zone and keeping the amount of the catalytic solution within a given range in carrying out the reaction in the presence of a catalyst containing Rh and an oxide of an organophosphorus compound. CONSTITUTION:An Rh compound (preferably rhodium nitrate) and an oxide of a trivalent organophosphorus compound (e.g. triphenylphosphine oxide) are mixed in a solvent and Co is then introduced thereinto to provide an active Rh catalyst. An olefin is hydroformylated in the presence of the resultant Rh catalyst and a trivalent organophosphorus compound is added to the reaction solution. Distillation is subsequently carried out to afford a formed aldehyde. A recycled catalyst solution consisting of high-boiling fractions containing Rh is then partially taken out and steams distillation is conducted at <=250 deg.C column bottom temperature using steam in an amount of <=30 times to distil away at least part of the high-boiling by-products. The bottoms are subsequently recycled to the reaction system. Thereby the deterioration of catalyst activity is suppressed by the above-mentioned method.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a process for the hydroformylation of olefins.

Preferably, the present invention provides a method for hydroformylating an olefin in the presence of a catalyst consisting of rhodium and an oxide of a trivalent organic phosphorous compound, in which the pB medium is recycled to the reaction zone. The present invention relates to a method for carrying out a hydroformylation reaction of an olefin while maintaining a constant amount of catalyst liquid by removing M1 boiling point organisms.

[Conventional technology]

It is well known to produce aldehydes by subjecting olefinic compounds to a hydroformylation reaction with carbon monoxide and hydrogen in the presence of a rhodium or cobalt catalyst. In particular, in the hydroformylation reaction of olefinic compounds having branches, the hydroformylation reaction is carried out using a rhodium catalyst modified with the oxide of a trivalent organophosphorus compound, and the resulting reaction product is a trivalent organophosphorus compound. is added and distilled, and the generated aldehyde is distilled off to obtain it, while,
A method has been proposed in which the bottom liquid containing the rhodium catalyst is recycled to the reaction system of the hydroformylation reaction (see JP-A No. 76034, JP-A 9-9-3, etc.).

In the above method, when the circulating catalyst liquid is used repeatedly, reaction by-products having a boiling point higher than the generated aldehyde (hereinafter referred to as high-boiling by-products) accumulate in the circulating catalyst liquid.
9 corresponding to the answer tic of the accumulation increases the volume of the entire catalyst liquid, so that it becomes impossible to maintain operation in the reaction vessel of the specified # violet. Even if the amount of high-boiling by-products produced per one reaction of 1A is very small, the 11 volume becomes an enormous amount due to the repetition of the steps of reaction, separation of produced aldehyde, and recirculation. Therefore, it is necessary to extract not only the generated aldehyde but also the high-boiling byproducts out of the reaction system by some means in proportion to the amount of the generated aldehyde. The following methods can be considered.

(2) A method in which a certain amount of the circulating catalyst liquid containing the high boiling point by-product is withdrawn in proportion to the amount of nodal by-product produced.

(2) A method in which the circulating catalyst liquid containing the high-boiling by-products is subjected to distillation to selectively distill off only the high-boiling by-products.

(2) A method in which the above-mentioned distillation ((1)) is carried out by steam distillation (see Japanese Patent Application Laid-Open No. 2003-41302).

[Problem that the invention seeks to solve]

However, although it is possible to remove all of the high-boiling by-products produced by method (2) above, the rhodium-containing catalyst and the trivalent organic phosphorus compound are also extracted at the same time. This increases the cost of recovering the catalyst component from the source, making it uneconomical. In addition, in method (2) above, it is possible to remove nodal by-products up to a certain boiling point, but it is not possible to remove those with a boiling point higher than that, and there is also the problem that the activity of the catalyst decreases during distillation. However, it cannot be adopted industrially. Furthermore, although it is possible to remove high-boiling by-products using method (2) above, the catalyst system consisting of rhodium and the oxide of a trivalent organic phosphorus compound significantly reduces the activity of the catalyst during distillation, making it difficult to use industrially. There is a slight problem with this.

In industrial operations, the process of removing high-boiling by-products from the circulating catalyst liquid not only allows for selectively removing only the high-boiling by-products from the circulating catalyst liquid to a desired extent, but also reduces the amount of the circulating catalyst liquid retained. It is desired that the catalytic activity of the catalyst is not impaired during the removal process.

[Means for solving problems]

In view of the above-mentioned prior art, the present inventors have conducted an intensive investigation to resolve the problems associated with the method (2) above.When removing high-boiling by-products by steam distilling a catalyst liquid under specific conditions, The present invention was completed by discovering that the reduction in the activity of the catalyst is effectively suppressed, and that a portion of the high-boiling byproducts are decomposed and recovered into aldehydes or alcohols.

That is, the gist of the present invention is to react an olefinic compound with carbon monoxide and hydrogen in a catalyst solution containing rhodium and an oxide of a trivalent organic phosphorus compound, and to obtain a hydroformylation reaction solution containing a trivalent organic phosphorus compound. After adding the compound and separating and obtaining the generated aldehyde by distillation, the residual liquid consisting of a high-boiling fraction containing rhodium is used as a circulating catalyst liquid and is added to the reaction system Kh.
In a hydroformylation method including circulation, at least a part of the circulating catalyst liquid is extracted as a extracted catalyst liquid, and the extracted catalyst liquid is supplied at a ratio (weight ratio) of steam to the extracted catalyst liquid of 30. or less, and the bottom temperature is λ! θ
There is a method for hydroformylating olefins, which is characterized in that at least a portion of high-boiling byproducts are distilled off by steam distillation at temperatures below .degree. C., and the bottoms are recycled to the hydroformylation reaction system.

The present invention will be explained in more detail below.

In the hydroformylation reaction of olefins using a catalyst containing rhodium and an oxide of a trivalent organic phosphorus compound, the present invention separates high-detailed point bioorganisms from the catalyst liquid discharged from the reaction system, and the remaining liquid is used for the hydroformylation reaction. Applicable when recycled to the system for reuse.

The hydroformylation reaction step in the method of the present invention is carried out according to a conventional method. Usually, uIi is obtained from the circulation process described below.
A reaction is carried out by using a solution containing agglomerated rhodium and oxide of a trivalent phosphorus compound as a catalyst, and supplying an olefinic compound and aqueous gas. Additional supplies can be provided. ms can be gmg in the reaction system by adding a rhodium compound and, if desired, an oxide of a trivalent monophosphorous compound to this hydrophoric reaction step, but the rhodium compound and the trivalent organic phosphorus compound can It is preferable to mix the oxides in a solvent and introduce -carbon oxide into the mixture to form an active rhodium catalyst before adding it to the reaction system. , inorganic acid salts such as rhodium sulfate; am salts such as vinegar [o dicum, g#ker sodium sodium, rhodium potassium malate, etc.: [RhL,] X, , [RhL, H
,o]x,, (RhLll(OH)IK,,[Rh
Ls(NOx))xt, (Rh('7)s("5)t)
(In the formula, X represents N01, OH- or + (“knee”), L represents N4, and P7 represents pyridine.)
Examples include amine #salts such as . Among them, rhodium nitrate and rhodium acetate are preferably used.

Examples of oxides of trivalent organic phosphorus compounds include arylphosphine oxides such as triphenylphosphine oxide, tritolylphosphine oxide, and dorianisylphosphine oxide; tributylphosphine oxide;
Alcohol-based phosphine oxide such as trioctylphosphine oxide; has both an alkyl group and a 7-aryl group! 7-aryl phosphite oxides such as triphenyl phosphite oxide (triphenyl phosphate) and tritolyl phosphite oxide; Kylphosphite oxide; alkylaryl phosphite oxide having both an alkyl group and an aryl group: bis(dienylphosphinone methane dioxide,
/, -monobis(diphenylphosphino)ethane dioxide, /#″-bis(diphenylphosphino)butane dioxide, /, 2-bis(diphenylphosphinomethyl)
Cyclobutane dioxide, a2. The oxides of these trivalent organic phosphorus compounds include polydentate phosphine oxides such as -0-inglobylidene-, 3-dihydroxy-/, and Hiro-bis(diphenylphosphino)butane dioxide. , in the hydroformylation reaction system, phosphorus in the oxide form is /θ~! with respect to rhodium/atom.
It is preferable that the number of atoms is zero. Too little phosphorus in the oxide form reduces the stability of the catalyst, while too much phosphorus reduces the rate of the hydrophorylation reaction.

In addition, in order to prepare an active catalyst in advance from a rhodium compound and an oxide of a trivalent organic phosphorus compound, it is preferable to mix the two in the above ratio and then treat this with -carbon oxide.

The conditions are 1 version carbon partial pressure /~-〇θ~/cd,
Preferably 7~/θjc9/aA, temperature io~aoo°C
, preferably from 20 to 730°C, and from 7 to 100 minutes, preferably from - to 0 minutes. Note that it is preferable to use carbon oxide that does not substantially contain hydrogen.

The catalyst hardness in the reaction zone is usually as rhodium/~j0
0 wg/11 t<+tx ~ 100 ay/l.

Examples of the olefinic compound to be subjected to the hydroformylation reaction include ethylene, globylene,
Straight chain α-olefins such as pentene, /-hexene, /-octene, /-decene, etc.-1-butene, λ-pentene,
--Hexene, J-hexene, co-octene,! -Linear internal olefins such as octene; isobutylene, λ-methyl-7-phthene, -1-methyl-/-pentene, 3-methyl-/-pentene, -1-methyl-7-hexene, J-
Methyl-/-hexene, co-methyl-/-heptene, 3
-Methyl-/-heptene, Hiro-methyl-1-heptene,
Branched α-olefins such as -13-dimethyl-/-butene, λ, 3-dimethyl-/-pentene, J, 4t-dimethyl-/-pentene, -13-dimethyl-/-hexene 1.2. @-dimethyl-/-hexene, λ,! Hyperbranched α-olefins such as -dimethyl-/-hexene, j,4t-dimethyl-/-hexene, and 21-bond isomers thereof.

In addition to the above, olefin oligomer isomer mixtures such as dicapsules and tetramers of lower olefins such as globylene, butene, and imbutylene, Saratra allyl alcohol, acrolein acetal, vinyl acetate, styrene,
Substituted olefins such as alkyl vinyl ethers can also be used. In particular, the present invention is directed to a carbon-carbon fraction obtained by diluting a fraction with a carbon number of 1 (hereinafter referred to as BB fraction) obtained in large quantities from the thermal cracking of naphtha or the catalytic cracking of heavy and light oils.
The hydroformylation of olefin isomer mixtures is advantageously applied.

This is because, unlike the case of using a rhodium catalyst modified with an organic phosphine, in the method of the present invention using a catalyst that functions with rhodium and an oxide of a trivalent organic phosphorus compound,
This is because it progresses with these branches.

In the method of the present invention, a solution containing oxides of rhodium and trivalent organic phosphorus compounds, which are obtained by C11 agglomeration from the circulation process, is usually used as the reaction medium, but additional solvents may also be used. .

Any solvent can be used as long as it dissolves the catalyst and does not adversely affect the reaction.

For example, aromatic hydrocarbons such as benzene, toluene, xylene, and dodecylbenzene; alicyclic hydrocarbons such as cyclohexane; ethers such as dibutyl ether, ethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetrahydrofuran; diethyl phthalate; Esters such as dioctyl phthalate are used. Also,
Aldehydes produced by a hydroformylation reaction can also be used as a solvent.

A higher reaction temperature is advantageous in terms of reaction rate, but if the temperature is too high, there is a risk that the catalyst will decompose. So usually!
It is preferable to carry out the reaction with 0-/70"C1, especially /(7<7~izo"c).

-For carbon oxide and hydrogen gas, the molar ratio of hydrogen and carbon monoxide is //J'~! //, especially a water gas in the range of //λ to co// is preferred. The partial pressure of the water gas used is in the range of 10 to 100 kg/-, preferably in the range of to to J00JC9/-.

The reaction can be carried out either continuously or batchwise.

Next, a trivalent organic phosphorus compound is added to the reaction solution of the hydroformylation reaction, and then distilled to distill out the aldehyde or alcohol produced by the reaction. As the trivalent organic phosphorus compound, it is preferable to use one corresponding to the oxide in the catalyst solution for the hydroformylation reaction. Usually, triphenylphosphine, tributylphosphine, etc. are used. The trivalent organic phosphorus compound coordinates rhodium MmK in the reaction solution to stabilize it. The trivalent organic phosphorus compound is added so that the amount of phosphorus in the trivalent form is greater than /M to rhodium/atom. However, even if multiple uses are used, the stability of the leading edge is proportional to the amount used, and the stability of the leading edge is not completely giJ. Add so that it becomes ~20 atoms.

The reaction solution of the hydroformylation reaction to which a trivalent organic phosphorus compound has been added is distilled by a conventional method to separate into light boiling fractions such as generated aldehydes and alcohols and high boiling fractions containing rhodium catalysts. . Since the rhodium catalyst in the reaction solution is stabilized by a trivalent organic phosphorus compound, any distillation method can be used, such as Futoshi S distillation, atmospheric distillation, vacuum distillation, or a combination thereof. can.

In addition, # trade temperature is usually below -00℃, special KJj~/10℃
A range of is appropriate.

The fraction before the fI6s point containing the rhodium catalyst and the oxide of a trivalent organic phosphorus compound discharged as a bottom liquid from the distillation process is agglomerated by 4% to the hydroformylation reaction mixture as a circulating catalyst liquid. At this time, in order to avoid accumulation of high-boiling by-products, at least a portion of the circulating Ik liquid is continuously or intermittently extracted from the reaction system as a mg liquid.

In the method of the present invention, the catalyst liquid extracted from the reaction system is subjected to steam distillation either directly or after removing the reaction solvent. When the extracted pB medium is directly subjected to steam distillation, the reaction solvent and high-boiling by-products are distilled off from the top of the steam column. In this case, if desired, the distillate can be further distilled to separate the solvent and high-boiling by-products, and the solvent can be recovered.

The contents of high-boiling by-products are diverse and complex, but they are mainly produced by primary side reactions of aldehydes produced in the hydroformylation reaction. High boiling point by-products include aldol which is a dimer of the aldehyde produced, unsaturated aldehyde which is the dehydration product of the aldol, saturated aldehyde and saturated IFQ alcohol which are the water temperature products of the unsaturated aldehyde, and the aldehyde produced. Examples include unsaturated ether which is a dehydration product of hekiacecool obtained from reaction 9 with its hydrogenated product, alcohol, acetal obtained by the reaction of the hexacetal with the produced aldehyde, and a ternary compound of the produced aldehyde. It will be done. Additionally, the two additional by-products have a high cohesive point and cannot be removed by a simple aldehyde distillation process.

In the steam distillation, at least a portion of the high-boiling byproducts in the extracted catalyst liquid are removed by distillation together with steam. The specific operating conditions of the steam distillation column include the amount of high-boiling by-products to be removed, the physical properties of the high-boiling by-products, the amount of the extracted catalyst liquid supplied to the steam distillation column, and the high-boiling by-products in the extracted catalyst liquid. Although it is determined by conditions such as the concentration of living organisms, in the method of the present invention, the supply amount ratio (weight ratio) of steam to the extracted catalyst liquid is 30// or less, preferably 0// or less, more preferably 0// or less. teeth/! //Hereafter, most preferably O0θ///~/
fl[! of θ// , fl, and maintain the bottom temperature at 2jθ°C or lower, preferably at 220°C or lower, more preferably at 2oo°C or lower. Note that it is preferable to adjust the operating pressure and/or external heating so that water and air do not condense in the column and mix with the bottoms.

If the supply ratio of steam to the extracted catalyst liquid exceeds the above upper limit, the activity of the catalyst will decrease significantly, and if the bottom temperature exceeds the above upper limit, the stability of the catalyst will decrease.
This is not preferable because the activity of the catalyst is significantly reduced.

The method of steam distillation mentioned above is not limited to %, but can be carried out by a conventional method. For example, this may be carried out by directly blowing steam into the distillation can of the steam #Iw column, by heating from the outside while blowing steam, etc., but the present invention is not limited to these methods.

In the steam distillation column, from the top of the column to the desired base, that is, in proportion to the amount of high-boiling by-products produced in the reaction,
High-boiling by-products are distilled off, and bottoms with a reduced content of high-boiling by-products are extracted from the bottom of the column. Most of the bottoms are recycled to the main formylation reaction step, but a portion is discharged outside the system as a catalyst liquid in order to remove high-boiling byproducts that cannot be removed in the steam distillation column. is preferable. In addition, the bottoms extracted from the bottom of the tower become two liquid phases.
In the case where a part of the blown steam is condensed and mixed, it is preferable to separate K from oil and water, and then circulate the oil layer to the human formylation reaction step.

Since the above-mentioned circulating catalyst liquid and steam distillation column bottoms contain trivalent organic phosphorus compounds, when these liquids are recycled to the hydroformylation reaction step, the trivalent compounds contained in
The IJ compound is oxidized to the corresponding oxide. For this purpose, it is desirable to carry out a method in which these liquids are oxidized in air and then circulated to the hydroformylation reaction step, or a method in which a peroxide is added to these liquids and then circulated to the hydroformylation reaction step.

In the latter method, the hydroformylation step is repeated.
! ! During ringing, the trivalent organophosphorus compound is oxidized to the corresponding oxide. As the K peroxide, for example, benzoyl peroxide, t-butyl peroxide, lauroyl peroxide 1.4 alt water It is best to use peroxide produced by air oxidation.

〔Example〕

Next, the implementation of the present invention! 1 will be explained in more detail with reference to Examples, but the present invention does not go beyond the gist of the invention.
The following examples are not intended to be limiting.

Example / (1) Synthesis of octene After removing butadiene and isobutyne from the BB fraction obtained from a naphtha cracker, the C,fli fraction (isobutene 6"iL amount, /-butene 4t3x, -1butene = ! group 1 L butanes 2! weight %, etc. / l Dochi's cordage was dehydrated using Molecule sieve / JKK. Next time, in a 10 Jl volume SUs stirred autoclave, 'i11 elementary atmosphere H gas Below, 1L of C6 fraction after dehydration described above and 2Kl of n-hexane bath solution j, j
, 51 (lJi content = t4wt%) and ethylalinium dichloride //, 31 were charged and reacted at 4tO 0 C for 2 hours.

After the reaction! wt% H, 80, aqueous solution 34tOji
was added to deactivate the catalyst, the liquid was separated into four liquids, and then distilled under atmospheric pressure to obtain octene.

The above reaction and distillation were carried out three times.

(2) In a 5US-Jet induction stirring autoclave with a hydroformylation reaction volume of 10 Jl, 7 t of octene obtained in (1) above and a methanol solution of rhodium acetate (rhodium concentration 4 to 7 t) were added.
) was added in an amount such that the rhodium linearity in the reaction solution was 70 cape/l, and then 20 times the molar amount of triphenylphosphine oxyto was added to the rhodium and the autoclave was sealed. After purging the inside of the autoclave with nitrogen gas, and then pressurizing the phoneme gas to 10 kg/dG and then releasing the pressure to normal pressure three times, the temperature of /JO'CK was raised. /JOC
Immediately after reaching tIC, the total pressure is /70 kg/adG
Inject water gas (H*/CO-/) under pressure so that
The reaction was carried out at 730°C for a period of time. During this time, the water gas consumed by the reaction was replenished from the pressure accumulator via the constant pressure device, and the inside of the autoclave was maintained at /70#/csiGK.

After the reaction was completed, the reaction solution was analyzed by gas chromatography, and the yield of aldehyde of 09 was 22%, O@
Alcohol yield: 9.20%, high-boiling byproduct conversion rate: 0.4
It was t0 俤.

(3) Concentration of high-boiling byproducts by steaming the hydroformylation reaction solution To the hydroformylation reaction solution obtained in (2) above, triphenylphosphine was added in an amount twice as much as the rhodium in the reaction solution, and nitrogen The aldehyde was distilled off by simple distillation in a gas atmosphere at a pressure of 20 wHy and a column top temperature of θ°C. 7.2% by weight of aldehyde having 2 carbon atoms (hereinafter referred to as C, aldehyde) and alcohol having 2 carbon atoms (hereinafter referred to as
09 alcohol and In5) 4.71 amounts, triphenylphosphine oxyto (hereinafter referred to as TPPO) J, /,
I quantity and high boiling point by-product (hereinafter referred to as HB)? the law of nature,!
A distillation residue of heavy tts was obtained.

(4) Removal of high-boiling by-products by steam distillation Volume with steam inlet, condenser, nitrogen capillary for stirring and distillate receiver! 00- pear-shaped flask with the above (3
) Add O- to the distillation residue obtained in 3011xrHy
While supplying the distillation residual liquid to the pot at a rate of 7d1 min while maintaining the temperature at iro℃ at a pressure of Jkl/c.
The water vapor of dck is supplied at the distillation residual liquid supply rate [K vs. O, a times (
Steam distillation was carried out by blowing at a rate of (weight ratio). As a result, oil layer distillate atco, jIi was obtained. The compositions of the resulting distillate and straw residue are shown in Table 1, and the removal rate of high-boiling byproducts was 4 t/, 7%. In addition, the composition of the obtained distillate and &I residual liquid and the amount of high-boiling by-products determined from the amount of charged liquid (distillation residual liquid in (3) above) and the active ingredients (total of Ce aldehyde, O, and alcohol) The rate of increase in amount) was as shown in Table/. In addition, the decomposition rate of high-boiling point organisms and the increase rate of active ingredients were determined by the following formula.

Decomposition rate of high boiling point by-products (illusion) Increase rate of active ingredients (H) - (5) Comparison of catalyst activity before and after steam distillation ■ Catalytic activity test of distillation residue before steam distillation The results obtained in (3) above Distillation residue treatment, a liquid obtained by blowing 9 air into the octene obtained in (1) above to generate peroxide (peroxide content: 730
milliequivalent/l) w! To 7 moles of triphenylphosphine in the distillation residue, t was added in an amount of 1 m to 7 moles, and the mixture was held at 4 tO ℃ for 30 minutes in a 1 m atmosphere to oxidize it to the corresponding oxide to obtain a catalyst liquid. Ta.

The octene obtained in (1) above and the catalyst liquid A obtained above were placed in a vertically stirred autoclave made of 5O8-374 with an internal volume of -〇〇-. The autoclave was sealed. After replacing the inside of the autoclave with nitrogen gas, pressurizing 1C nitrogen gas to 4tOkg/-G, and repeating the operation of releasing the pressure to normal pressure three times, 73
The temperature was raised to 0°C. Immediately after reaching 130℃, the total pressure is 77℃.
Submersible gas (H, /CO,
, / ) were injected under pressure, and the reaction was carried out at 73Q°C. During this time, the water gas consumed by the reaction is replenished from the pressure accumulator via a constant pressure device, and the inside of the autoclave is
/cdck. The reaction rate constant (seventh order) k was determined from the consumption rate of water gas in the pressure accumulator.

■ Catalytic activity test of &M solution after steam distillation The & residual solution obtained in (4) above was oxidized in the same manner as in (■) above, and catalyst solution B
I got it. The catalyst B was prepared to have the same rhodium degree as in (2) above, and the reaction was carried out using the same photograph as in (2) above, and the reaction rate constant (7th order) k! I asked for

It was 0.9/.

Examples 3 and Comparative Examples The same procedures as in Example 3 were carried out except that the steam distillation conditions were changed as shown in Table 1. The results are shown in Table/.

〔Effect of the invention〕

The method of the present invention makes it possible to effectively remove high-boiling by-products in a hydroformylation reaction using a catalyst system consisting of rhodium and an oxide of a trivalent organic phosphorous compound. In the method of the present invention, a decrease in the activity of the catalyst during the removal of high-boiling byproducts is suppressed, and a portion of the high-boiling byproducts can be decomposed into aldehydes or alcohols and recovered.

Patent applicant: San-ai Kasei Kogyo Co., Ltd. Representative Patent Attorney Hase - Haka/first name

Claims (1)

[Claims] (1) An olefinic compound was reacted with carbon monoxide and hydrogen in a catalyst solution containing rhodium and an oxide of a trivalent organophosphorus compound, and a trivalent organophosphorus compound was added to the resulting hydroformylation reaction solution. In a hydroformylation method that involves recirculating the residual liquid consisting of a high-boiling fraction containing rhodium to the reaction system as a circulating catalyst liquid after separating and obtaining the produced aldehyde by distillation, at least a portion of the circulating catalyst liquid is is extracted as an extracted catalyst liquid, and the extracted catalyst liquid is subjected to steam distillation under the conditions that the supply amount ratio (weight ratio) of steam to the extracted catalyst liquid is 30 or less and the bottom temperature is 250 ° C. or less. 1. A method for hydroformylating olefins, which comprises distilling off at least a portion of high-boiling byproducts and recycling the bottoms to a hydroformylation reaction system.