JPH0439397B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a method for removing acidic organic compounds from aqueous solutions, in particular the use of mixtures of two or more phosphine oxides without the use of diluents to remove lower carboxylic acids and phenolic compounds from commercial wastewater. Regarding how to. The treatment of aqueous effluents for the removal of contaminants and further recovery of useful compounds from solution is a most necessary part of modern chemical plants. A number of methods are used for this purpose, such as steam removal methods and somewhat complex solvent extraction methods. This latter method is highly dependent on the nature of the compound being recovered. Solvent selection is critical and must minimize solvent loss. Some organic compounds, such as acetic acid and phenols in dilute aqueous solutions, are particularly difficult to remove. It is known to extract acetic acid using ether or ketone as solvent. However, the equilibrium partition coefficient kd of acetic acid with these solvents (weight fraction of solute in solvent phase/weight fraction of aqueous phase at equilibrium) is approximately
1.0 or less. This low kd requires very high solvent flow rates in the extraction step, making recovery with these solvents economically unattractive when less than 3-5% by weight of acid is present in the aqueous solution. Other and somewhat more popular solvent systems have been applied by using certain organophosphorus compounds and especially phosphine oxide in the diluent. However, these extractant/diluent systems require that the presence of a diluent (which is often required because high melting point extractants can be used) considerably reduces the concentration of the extractant and removes it from the aqueous solution. This is disadvantageous because it evaporates cocurrently with the compound and thus interferes with the subsequent removal step. It is therefore advantageous to use 100% extractant as a solvent without diluent, but it is limited by the melting point of the extractant and the economical operating temperature at which the removal takes place. In particular, it is known to use pure trialkylphosphine oxide, but its relatively high melting point requires that the removal step be carried out above ambient temperature, subjecting it to the risk of freezing during plant breakdowns. It has now been unexpectedly demonstrated that the use of a trialkylphosphine oxide mixture not only provides a more acceptable melting point, but also increases the ability of this mixture to extract acidic organic compounds from dilute aqueous solutions. It's been found. This mixture provides unexpectedly high extraction coefficients for difficult to extract compounds such as acetic acid. The organic phase containing the removed compounds can be removed using several methods such as distillation or removal with alkaline solutions. Therefore, according to the present invention, when removing an acidic organic compound selected from the group consisting of substituted or unsubstituted carboxylic acids having 1 to 5 carbon atoms and substituted or unsubstituted phenolic compounds from a dilute aqueous solution, the aqueous solution is , at least two phosphine oxides, i.e. The first phosphine oxide and the formula of a second phosphine oxide, with the proviso that R ₁ ,
R ₂ , R ₃ , R ₁ ′, R ₂ ′ and R ₃ ′ are each independently selected from the group consisting of alkyl, cycloalkyl, aralkyl and substituted aralkyl having from C ₄ to C ₁₈ ; the total number of carbon atoms in the oxide is at least 15, and the total number of carbon atoms in the second phosphine oxide is at least 17;
the difference in the total number of carbon atoms in the first and second oxides is at least 2, and the at least one of the phosphine oxides is present in an amount of at least 5% and no more than 60% by weight; mixture of oxides 1) or with the formula R ₃ ″PO, R ₃
PO, _R2 ″RPO, R″ _R2PO , where R″ and R are each at least 4 selected from the group consisting of alkyl, cycloalkyl, aralkyl and substituted aralkyl having from _C4 to _C18 . A mixture of species of phosphine oxides which are liquid at room temperature, wherein the total number of carbon atoms of each phosphine oxide is at least 15, preferably at least 18.
and wherein the phosphine oxide is present in an amount of at least 1% by weight and no more than 60% by weight. Preferably, the total number of carbon atoms in the second phosphine oxide of mixture 1) is at least 19 and the difference in the total number of carbon atoms in the first and second oxides is at least 4. More preferably, the at least one phosphine oxide of mixture 1) is present in an amount of about 25-45% by weight, and the mixture of phosphine oxides has a melting point below about 50<0>C. Preferably, if the total number of carbon atoms of the first phosphine oxide with the lowest carbon atom is 18, the carbon of the second phosphine oxide of mixture 2) with the second lowest number of carbon atoms is preferably 18. The number of atoms is at least 20 and the difference between the total number of carbon atoms of the first oxide and that of the oxide with the highest number of carbon atoms is at least 6. More preferably, the at least one phosphine oxide in mixture 2) is present in an amount of about 35 to 50% by weight, and the mixture of phosphine oxides is about 20% by weight.
It has a melting point of less than 10°C, more usually less than about 10°C. Although the method of the present invention is believed to be useful with a variety of useful contaminants or impurities in dilute aqueous streams, it is particularly useful with acidic organic compounds such as carboxylic acids and phenolic compounds. In particular, the process is used to remove carboxylic acids having 1 to 5 carbon atoms, preferably acetic acid, propionic acid, butyric acid and valeric acid (usually found in industrial wastewater) and phenols. The carboxylic acid may be substituted by one or more halogen, hydroxyl, cyano or alkoxyl groups. Other special acids that may be removed by the method of the invention are hexanoic acid,
heptanoic acid, octanoic acid, nonanoic acid, benzoic acid,
Examples include succinic acid, oxalic acid, malic acid, lactic acid, cyanoacetic acid, glycolic acid and maleic acid.
The phenolic compounds provided in the present invention include those substituted with one or more alkyl groups. Examples of phenolic compounds that can be removed from dilute aqueous streams are p-cresol, resorcinol, 1-
naphthol, 2-naphthol, o-, m- and p
- xylenol and unsubstituted or substituted hydroquinones, phloroglucinol and pyrogallol. The compound removed from the dilute aqueous solution may be present in the dilute solution in any low or moderately low amount,
Usually less than 5% by weight, more preferably 2% by weight.
The amount may be less than 1% by weight or less than 1% by weight. The method of the present invention is particularly useful for recovering carboxylic acids from paper and synthetic fuel oil mill wastewater. The method is useful for the recovery of phenols from waste water from phenolic resin manufacturing processes and also for the gasification of quartz. It is believed that the recovery of organic and inorganic compounds that are normally difficult to extract (such as Sb, As, Bi compounds) can be accomplished by the method of the present invention. In the phosphine oxide, when one or more R or R'' groups is alkyl, preferred alkyls include straight and branched chain alkyls of about _C4 to about _C18 , while preferred cycloalkyls include carbon Number 6 ~
8 substituted or unsubstituted cycloalkyl. Examples of suitable phosphine oxides useful as mixture 1) are tri-n-hexylphosphine oxide (THPO), tri-n-octylphosphine oxide (TOPO), tris(2,4,4-
trimethylpentyl)-phosphine oxide, tricyclohexylphosphine oxide, tri-n
-Dodecylphosphine oxide, tri-n-octadecylphosphine oxide, tris(2-ethylhexyl)phosphine oxide, di-n-octylethylphosphine oxide, di-n-hexylisobutylphosphine oxide, octyldiisobutylphosphine oxide , tribenzylphosphine oxide, di-n-hexylbenzylphosphine oxide, di-n-octylbenzylphosphine oxide, 9-octyl-9-phosphabicyclo[3,3,1]nonane-9-oxide, etc. , but not limited to this.
TOPO and THPO are two-part mixes (part
mix) is the preferred oxide. One oxide of mixture 1) should be present in an amount of at least 5% and at most 60% by weight, with preferred amounts being about 25-45%, more preferably about 35%. Although many phosphine oxides can be used in mixture 1), it is most convenient to use a two-part mix. A particularly preferred two-part mix is a mixture of tri-n-octylphosphine oxide (TOPO) and tri-n-hexyl-phosphine oxide (THPO).
The preferred ratio for TOPO/THPO mixtures is 35/
It is 65% by weight. However, synergistic effects giving unexpectedly increased kd values can be obtained with two-part mixes or more of the above-mentioned phosphine oxides. The phosphine oxides used in mixture 1) are such that the total number of carbon atoms in the first and second oxides differs by at least 2, preferably at least 4,
More preferably, it is selected to be 6 or 8. Preferably, the melting point of mixture 1) is below about 60° C., which is the usual upper temperature limit for processing commercial waste solutions in liquid/liquid extraction processes. However, lower melting points are desirable to improve process efficiency and cost. A melting point of about 50°C is preferred, and therefore phosphine oxide mixtures that melt below about 50°C, more preferably below 30°C or 25°C, have practical advantages if the ability to extract acidic organic compounds is acceptable. It will be used in this method from the perspective of:
The most preferred mixture of TOPO/THPO in a proportion of 35/65% by weight melts at about 16°C. Examples of suitable phosphine oxides useful as mixture 2) include those described above for mixture 1). Additionally, the following phosphine oxides may be used: dihexylmonoctylphosphine oxide, dioctylmonohexylphosphine oxide, dihexylmonodecylphosphine oxide,
Didecylmonohexylphosphine oxide, dioctylmonodecylphosphine oxide, didecylmonoctylphosphine oxide, and dihexylmonobutylphosphine oxide. Although all oxides should be present in mixture 2) in an amount of at least 1% and at most 60% by weight, a preferred amount for at least one oxide is about 1.5-10.0% by weight. Although more than four phosphine oxides can be used in mixture 2), it is most convenient to prepare four mixes from two olefin compounds. Particularly suitable 4
The part mixes are tri-n-octylphosphine oxide (TOPO): tri-n-hexylphosphine oxide (THPO): dihexylmonoctylphosphine oxide and dioctylmonohexylphosphine oxide. However, a synergistic effect giving unexpectedly increased K _D values can be obtained using four or more part mixes of the phosphine oxides described above. The phosphine oxides used in mixture 2) are selected such that the difference in the total number of at least two carbon atoms of the oxides is at least 2 and up to 6 or more. Preferably, the melting point of mixture 2) is below about 20°C. However, lower melting points are desirable to improve process efficiency and cost, and to provide material handling advantages. Melting points below about 10°C are preferred and therefore phosphine oxide mixtures melting at about 10°C, more preferably 0±5°C, are suitable from a practical point of view, provided their acidic organic compound extraction performance is acceptable. can be selected for use in the present method. Apart from the energy savings obtained by using low melting point phosphine oxide mixtures, other advantages of low melting point mixtures are that the phosphine oxides can be used as is, thus avoiding the use of diluents; Also, the possibility of freezing during plant shutdowns is avoided. Low-melting eutectic mixtures of phosphine oxides allow the use of phosphine oxides for lowering their melting points, which until now can only be used at elevated temperatures or with diluents, often followed by complex removal operations. enable. Further, the preferred quaternary phosphine oxide mixture prepared from hexene and octene contains about 70%
Compared to the preferred binary phosphine oxide mixture of THOP/TOPO with THOP, approximately 20%
It only has THPO. Since THPO is soluble in water in excess of the desired amount, a suitable quaternary phosphine oxide mixture with less THPO will obviously have less solubility in aqueous solution and will be less soluble in a binary system for extracting acidic organic compounds from aqueous solution. It is more advantageous than However, the main advantage of the phosphine oxide mixtures used in the process of the invention is the unexpectedly increased extractability provided by such mixtures. This extractability exceeds that of an equivalent amount of phosphine oxide when used alone, thus saving in the process the amount of phosphine oxide required to extract the desired solute from a dilute aqueous solution. do. Suitable phosphine oxide mixtures 2) are prepared by reacting two or more olefin compounds, such as pentene, hexene, octene and decene, with phosphine. The intermediate tertiary phosphine product from two olefinic compounds such as octene and hexene is oxidized with hydrogen peroxide to form a four-component trialkylphosphine oxide mixture, namely R ₃ ″PO, R ₃ PO, R ₂ ″R
Obtain PO, R′R ₂ PO. Depending on the ratio of olefin compounds (octene/hexane), the mixture can be liquid at room temperature. For example hexene 70% by weight:
The freezing temperature of a mixture of 30% by weight octene is approximately 0°C. For practical handling reasons, the mixture is liquid at room temperature. For example, nine-part mixes obtained from hexene, octene and decene have been found to be particularly convenient and effective. The invention will be described in further detail by the following examples, which are given for illustrative purposes only. Example 1 Samples of solvents were tested for the extractability of acetic acid and also phenols from dilute aqueous solutions. A sample of each solvent was shaken and mixed with an aliquot of an aqueous solution containing acetic acid. After a few minutes, the aqueous and organic phases were separated and the aqueous phase was analyzed for the presence of acetic acid. Mixing with the aqueous phase was repeated until all the acetic acid was recovered and transferred to the organic phase. The volume of organic phase (solvent) required for 100% recovery is expressed as the aqueous/organic (A/O) ratio.

【table】

Table: For samples 1 and 2, TOPO was dissolved in the commercial diluent DPA from Conoco, which consists of diphenyl alkane. It is seen that increasing the amount of TOPO in the solvent reduces the amount of organic phase used, ie increases the aqueous/organic (A/O) ratio. However, for solvent sample 3, the phosphine oxide mixture (THPO: 65% by weight of TOPO: 35% by weight)
substantially increases the extraction capacity of acetic acid. Sample 4 also showed substantially increased A/O values in the extraction of phenols. This clearly shows that a smaller amount of organic (solvent) phase is sufficient for 100% recovery of phenol from aqueous solution. Example 2 Commercial aqueous effluents containing acetic acid and propionic acid in amounts of 6.15 and 1.50 gpl were treated with THPO/TOPO
The mixture was used for extraction. Equilibrium concentrations for each carboxylic acid were determined for different A/O ratios.

[Table] *Based on aqueous analysis and mass balance.
Isotherms aligned with the Y-axis for residual acid.
Furthermore, the same wastewater was extracted using solvents containing TOPO at different concentrations.

[Table] Matched isotherms.
Kd values for THPO/TOPO mixtures using TOPO alone in diphenylalkane (DPA) diluent for corresponding A/O ratios
It is clearly shown that it is much larger than the Kd value. Example 3 An aqueous solution containing 10 gpl phenol was extracted with solvents of different extractant concentrations.

[Table] Determine the equilibrium phenol concentrations in the organic and aqueous phases for various A/O values and find the equilibrium partition coefficient.
Kd was calculated. Again, it is seen that the Kd values for the phosphine oxide mixture are unexpectedly higher than for the single oxide solvent for all A/O values. The following four examples illustrate C ₈ /C 6 mixtures as well as C ₁₀ /C ₆ mixtures in the preparation of quaternary phosphine oxide mixtures.
An example of the use of _C6 mixture is shown. Example 4 In an autoclave, phosphine was reacted with an olefin mixture consisting of 70% by weight of octene and 30% by weight of hexene. The intermediate reaction product (tertiary phosphine) was then oxidized with hydrogen peroxide to produce a final product containing a mixture of four tertiary phosphine oxides. The product is trihexylphosphine oxide 3.9% according to analysis,
Dihexyl monooctylphosphine oxide 22.8
%, dioctylmonohexylphosphine oxide
45.7% and trioctylphosphine oxide 27.6
% (by weight). The final product had a melting point range of 8-17°C and was liquid at room temperature. Example 5 Example 4 was repeated using an olefin mixture consisting of 60% by weight octene and 40% by weight hexene. The final tertiary phosphine oxide product was analyzed to be trihexylphosphine oxide 8
%, dihexyl monooctylphosphine oxide
31.9%, dioctylmonohexylphosphine oxide 42.8% and trioctylphosphine oxide
It was found that it contained 17.4% (by weight).
The final product had a melting point range of -5 to 0<0>C and was liquid at room temperature. Example 6 Example 4 was repeated using an olefin mixture consisting of 30% by weight octene and 70% by weight hexene. The final product was analyzed to contain 40.2% trihexylphosphine oxide, 42.6% dihexylmonoctylphosphine oxide, 15.3% dioctylmonohexylphosphine oxide, and 2% trioctylphosphine oxide. The tertiary phosphine oxide mixture is -7 to +
It had a melting point range of 6°C and was liquid at room temperature. Example 7 Example 4 was repeated using an olefin mixture consisting of 50% by weight decene and 50% by weight hexene.
The final product was analyzed to contain 22% trihexylphosphine oxide, 42.5% dihexylmonodecylphosphine oxide, 28.9% didecylmonohexylphosphine oxide, and 6.4% tridecylphosphine oxide. The final product had a melting point range of -5 to +10°C and was liquid at room temperature. The following Table 4 shows 70% by weight hexene and octene.
A quaternary phosphine oxide mixture from 30 wt% (Example 6) has somewhat improved performance properties for use as a solvent extractant when compared to a binary mixture of 65 wt% THPO/5 wt% TOPO3. However, both binary and quaternary mixtures are shown to be superior to conventional methods.

[Table] That is, when calculating K _D values using the equilibrium acetic acid concentrations in the organic and aqueous phases for various A/O values, the K _D values for quaternary mixtures, especially at high acetic acid loadings, are It can be seen that it is somewhat higher than the mixture (high A/O ratio). Additionally, interpolation from the acetic acid isotherms shown in Table 4 shows complete extraction in four stages at A/O=2 for binary mixtures. When using comparable quaternary mixtures, three stages are required at A/O=2. The accompanying drawings show the extraction properties of the quaternary phosphine oxide mixture and the binary mixture of Example 8.

[Brief explanation of drawings]

The figure shows the extraction properties of acetic acid using binary and quaternary phosphine oxides.

Claims (1)

[Scope of Claims] 1. When removing an acidic organic compound selected from the group consisting of substituted or unsubstituted carboxylic acids having 1 to 5 carbon atoms and substituted or unsubstituted phenolic compounds from a dilute aqueous solution, the aqueous solution is At least two phosphine oxides, i.e. a first phosphine oxide and of a second phosphine oxide, with the proviso that R ₁ ,
R ₂ , R ₃ , R ₁ ′, R ₂ ′, R ₃ ′ are each independently selected from the group consisting of alkyl, cycloalkyl, aralkyl, and substituted aralkyl having from C ₄ to C ₁₈ ;
The total number of carbon atoms in the second phosphine oxide is at least 17, the difference in the total number of carbon atoms in the first and second oxides is at least 2, and at least one of the phosphine oxides is ,
Mixtures of phosphine oxides 1) present in an amount of at least 5% by weight and no more than 60% by weight
or at least four phosphine oxides, i.e. of the formula R ₃ ″PO, R ₃ PO, R ₂ ″RPO, R″R ₂ PO
, with the proviso that R'' and R are each independently selected from the group consisting of alkyl, cycloalkyl, aralkyl, and substituted aralkyl having from _C4 to _C18 , and the total number of carbon atoms in each phosphine oxide is at least 1% by weight. present in an amount not more than 60% by weight in
A method for removing an acidic organic compound, which comprises bringing the compound into contact with mixture 2) which is a liquid at room temperature. 2. The total number of carbon atoms in the second phosphine oxide of mixture 1) is at least 19, and the difference in the total number of carbon atoms in the first and second oxides of mixture 1) is at least 4. A method according to claim 1. 3. The method of claim 1, wherein said at least one phosphine oxide of mixture 1) is present in an amount of about 25-45% by weight. 4. A process according to claim 1 or 3, wherein said mixture of phosphine oxides of mixture 1) has a melting point below about 50<0>C. 5. The method of claim 1 or 3, wherein the acidic organic compound is selected from the group consisting of acetic acid, propionic acid and phenol. 6. The method of claim 1, wherein said at least one phosphine oxide of mixture 1) is present in an amount of about 35% by weight. 7. The mixture 1) of phosphine oxide is heated to about 30°C.
Claim 1 or 3 having a lower melting point
The method described in section. 8. The method of claim 1, wherein the at least one phosphine oxide of mixture 1) is tri-n-octylphosphine oxide. 9 The mixture 1) of phosphine oxides is tri-
n-hexylphosphine oxide and tri-n-
The method according to claim 3 or 5, which is octylphosphine oxide. 10. The method of claim 1, wherein said mixture of phosphine oxides has a melting point of less than about 20°C. 11 The total number of carbon atoms of the first of the phosphine oxides of mixture 2) having the lowest number of carbon atoms is at least 18, and the total number of carbon atoms of the second of the phosphine oxides of mixture 2) having the lowest number of carbon atoms is at least 20. and
and the difference between the total number of carbon atoms of the first oxide of mixture 2) and that of the oxide with the highest number of carbon atoms of mixture 2) is at least 6. 12. The method of claim 1, wherein at least one of the phosphine oxides in mixture 2) is present in an amount of about 35-50% by weight. 13 The mixture 2) of phosphine oxides is about 10
2. A method according to claim 1, having a melting point below .degree. 14 The mixture 2) of phosphine oxides is tri-n-hexylphosphine oxide, tri-n-
The method according to claim 1, wherein octylphosphine oxide, dihexylmonoctylphosphine oxide and dioctylmonohexylphosphine oxide are used. 15 The mixture 2) of phosphine oxides is tri-n-hexylphosphine oxide, tri-n-
2. The method according to claim 1, wherein decylphosphine oxide, dihexylmonodecylphosphine oxide and didecylmonohexylphosphine oxide. 16. The method of claim 1, wherein said mixture 2) of phosphine oxides comprises at least 9 phosphine oxides. 17. Process according to claim 16, in which hexyl, octyl and decyl groups are present in mixture 2). 18 Formula R ₃ ″PO, R ₃ PO, R ₂ ″RPO, R″R ₂
PO, where R″ and R are each C ₄ to C ₁₈
a phosphine oxide mixture of at least four phosphine oxides independently selected from the group consisting of alkyl, cycloalkyl, aralkyl, and substituted aralkyl having a total number of carbon atoms in each phosphine oxide of at least 15. A phosphine oxide mixture, wherein the phosphine oxides are present in the mixture in an amount of at least 1% and no more than 60% by weight, and the mixture is liquid at room temperature. 19. A phosphine oxide mixture according to claim 18 having a melting point below 20°C. 20 The total number of carbon atoms of the first of said phosphine oxides having the lowest number of carbon atoms is at least 18
and a second of said phosphine oxides is at least 20, and the difference between the total number of carbon atoms of the first oxide and that of the oxide having the highest number of carbon atoms is at least 6. A phosphine oxide mixture according to claim 18. 21 The at least one phosphine oxide is about
Claim 1 present in an amount of 35-50% by weight
Phosphine oxide mixture according to item 8. 22. The phosphine oxide mixture of claim 18 having a melting point below about 10°C. 23 Trihexylphosphine oxide about 2-45
% by weight of dihexyl monooctylphosphine oxide, 20-45% by weight of dihexyl monooctylphosphine oxide, 10-48% by weight of dioctylmonohexylphosphine oxide, and 1-30% by weight of trioctylphosphine oxide. phosphine oxide mixture. 24 Trihexylphosphine oxide about 2-24
% by weight of dihexylmonodecylphosphine oxide, 40-45% by weight of dihexylmonodecylphosphine oxide, 26-33% by weight of didecylmonohexylphosphine oxide and 4-9% by weight of tridecylphosphine oxide. phosphine oxide mixture. 25 Formula R ₃ ″PO, R ₃ PO, R ₂ ″RPO, R″R ₂
PO, where R″ and R are each C ₄ to C ₁₈
a phosphine oxide mixture of at least four phosphine oxides independently selected from the group consisting of alkyl, cycloalkyl, aralkyl, and substituted aralkyl having a total number of carbon atoms in each phosphine oxide of at least 15. A process for producing a phosphine oxide mixture, wherein the phosphine oxides are present in the mixture in an amount of at least 1% by weight and no more than 60% by weight, and the mixture is liquid at room temperature, A process for producing a phosphine oxide mixture of tertiary phosphine oxides by reacting both olefinic compounds with phosphine to produce an intermediate tertiary phosphine product. 26. The method according to claim 25, wherein the oxidation is carried out by adding hydrogen peroxide. 27. The method according to claim 25 or 26, in which hexene is reacted with octene. 28 About 25-65% by weight of octene and about 75% by weight of hexene
Claim 2 reacted together with 35% by weight
5 or 26. 29 Approximately 55 to 65% octene and approximately 35 to 65% hexene by weight
Claim 2 reacted together with 45% by weight
5 or 26. 30. The method according to claim 25 or 26, wherein hexene is reacted with decene. 31 Hexene, octene and decene are reacted followed by oxidation to form nine phosphine oxides in the mixture Claim 25
or the method described in item 26.