EP4622980A1

EP4622980A1 - Regeneration of triphenylphosphine oxide

Info

Publication number: EP4622980A1
Application number: EP23808811.6A
Authority: EP
Inventors: Nico BRODMANN; Lisa HABERER; Leonardo LE; Christian Lothschuetz; Maurus Marty; Pierre PETRYNA
Original assignee: DSM IP Assets BV
Current assignee: DSM IP Assets BV
Priority date: 2022-11-23
Filing date: 2023-11-20
Publication date: 2025-10-01
Also published as: CN120225533A; WO2024110365A1; JP2025537093A

Abstract

The present invention relates to an improved process for preparing triphenylphosphine (TPP) by reacting triphenylphosphine oxide (TPPO) with a catalyst in the presence of an inert solvent and with the addition of a specific alcohol.

Description

Regeneration of Triphenylphosphine Oxide

TPP, which is the compound of formula (I) is used on the industrial scale in the Wittig Ylide synthesis to prepare olefinic compounds such as vitamin A or carotenoids, the TPP being employed in the stoichiometric amount and being oxidized to TPPO, which is the compound of formula (II)

Therefore, a lot of TPPO is produced during these reactions and unfortunately only few uses of TPPO have been disclosed. Since it is an extremely stable substance which can be disposed of only with difficulty, there have been numerous attempts to convert it back into TPP.

One common way to deal with the TPPO problem is to burn the TPPO, so that it can be wasted in a secure way. Therefore, the phosphorus can be re-used again instead of sourcing it again. Another one is the recycling of the TPPO to TPP, which can then be re-used again.

Such recycling processes are known from the prior art. (i.e. from EP638580, from Heteroatom Chemistry 26(3), 2015, p.199 - 205). Most of these recycling processes are carried out in the presence of polymethylhydrosiloxane (PMHS), which is the compound of formula (III)

(CH3)3Si-(CH₃(H)Si-O)n-Si(CH₃)3 (III) wherein n is a value usually between 10 and 100’000 (preferably n is a value from 100 - 20’000, more preferably n is a value from 1000 - 12’000, most preferably n is a value from 1000 - 10’000) in combination with a Ti-compound as catalyst.

Berthod et al. describe in SYNLETT, vol. 2007, no. 10, p. 1545-1548 a particular method using hydroxysilanes, such as TMDS and PMHS, in the presence of a Ti-compound or a Zr- compound as catalyst for reduction of TPPO to regenerated TPP. Berthod et al. points out that PMHS is unfavourable for the work-up and recovery due to gel formation, and that TMDS has a higher reactivity. Berthod et al. further reported that they did not observe any significant reduction of TPPO to TPP using zirconium-based catalysts.

Nevertheless, the use of PMHS as reducing agents has some major disadvantage, namely the need for a work-up procedure.

This work-up procedure is usually performed at very high pH in order to hydrolyse the nonreacted PMHS. Therefore, the work-up procedure consumes huge amounts of base such as KOH or NaOH (typically more than 10 equivalents) resulting in an even larger amount wastewater.

Due to the importance of the reaction, wherein the TPPO is produced (as a waste product) and the problems with the use of TPPO and its disposal, there is a need for an improved way for transforming TPPO into TPP, which can then be used again and wherein the amount of the resulting wastewater is kept at a minimum.

Surprisingly, it was found when using specific reaction conditions, it is possible to reduce TPPO back into TPP directly in an excellent yield, and the work-up of the reaction mixture is carried out in an improved manner.

Therefore, the present invention relates to the process (P) of producing triphenylphosphine (compound of formula (I)) wherein a first (step 1) triphenylphosphine oxide (the compound of formula (II)) is reacted with the compound of formula (III)

(CH3)3Si-O-(CH₃(H)Si-O)n-Si(CH₃)3 (III) wherein n is a value between 10 and 100’000 (preferably n is a value from 100 - 20’000, more preferably n is a value from 1000 - 12’000, most preferably n is a value from 1000 - 10’000) in the presence of at least one catalyst of formula (IV) wherein

M is titanium (Ti), or zirconium (Zr), or a mixture of compound (IV) wherein M is Ti and compound (IV) wherein M is Zr, and wherein

R, Ri, R2 and R3 are independently from each other OR4, wherein R4 is a linear or branched Ci - Ce alkyl group, in at least one aromatic solvent and/or in at least one alkane, at elevated temperature and in a second step (step 2) at least one alcohol of formula (V)

R₅-OH (V), wherein Rs is a linear or branched Ci - Cs alkyl moiety is added to the reaction mixture.

At the end of the process the solvent (or the mixture of solvents) is removed (for example by distillation) and the compound of formula (I) is obtained.

The compound of formula (I) can be further purified by using commonly known processes.

Usually the obtained compound of formula (I) is washed with the same alcohol of formula (V) (or mixtures thereof) as used in the step 2.

The solvent used in the process according to the present invention is at least one aromatic solvent and/or at least one alkane.

Suitable and preferred aromatic solvents are benzene, benzene substituted with one or more Ci-C4-alkyl or benzene substituted with one or more OCi-C4-alkyl group, or mixtures thereof.

More preferred aromatic solvents are benzene, toluene, mesitylene, xylene and anisol, moreover, diethylbenzene in isomeric pure form, or as mixture of o,m,p-isomers, as well as solvent naphtha, also called petroleum, such as e.g. Solvesso 100 by Exxon Mobil, or mixtures thereof.

Therefore, the present invention also relates to a process (P1 ), which is process (P), wherein the at least one aromatic solvent is chosen from the group consisting of benzene, benzene substituted with one or more Ci-C4-alkyl and benzene substituted with one or more OC1-C4- alkyl group.

Therefore, the present invention also relates to a process (PT), which is process (P), wherein the at least one aromatic solvent is chosen from the group consisting of benzene, toluene, mesitylene, xylene, diethylbenzene (pure or isomeric mixture), and anisol, or mixtures thereof.

Suitable alkanes are C4-Ci8-alkanes, which can be linear, branched as well as cyclic. Suitable alkanes are pentane, hexane, heptane, octane, decane, undecane, dodecane, or any mixture of alkanes (such as i.e. Isopar M).

Therefore, the present invention also relates to a process (P2), which is process (P), wherein the at least one alkane is a C4-Ci8-alkane, which can be linear, branched or cyclic.

Therefore, the present invention also relates to a process (P2’), which is process (P), wherein the at least one alkane is chosen from the group consisting of pentane, hexane, heptane, octane, decane, undecane, dodecan, and any mixture of alkanes.

At the start of the process according to the invention TPPO is suspended in at least one aromatic solvent and/or in at least one alkane and the PMHS (the compound of formula (III)) was added.

PMHS is usually and preferably added in an amount of 1.0 to 4 mol-equivalent (calculated in respect to the active hydrogen content of PMHS in view of the amount of TPPO).

Therefore, the present invention also relates to a process (P3), which is process (P), (P1), (PT), (P2) or (P2’), wherein the compound of formula (III) is added in an amount of 1.0 to 4 mol-equivalent (calculated in respect to the active hydrogen content of PMHS in view of the amount of TPPO).

The process according to the present invention is carried out in the presence of at least one catalyst (compound of formula (IV)). In the compound of formula (IV), M represents a metal of the 4^th group of the periodic table, preferably titanium (Ti) or zirconium (Zr).

In another embodiment of the present invention, the process is carried out in the presence of a catalyst using a mixture of a compound of formula (IV) wherein M is Ti (compound (IV)-Ti) and of a compound of formula (IV) wherein M is Zr (compound (IV)-Zr).

In such embodiment, the mixture of compound (IV)-Ti and compound (IV)-Zr may be used in a ratio of (IV)-Ti : (IV)-Zr of between 1 :99 and 99:1 , preferably in a ratio of between 20:80 and 80:20 or most preferably in a ratio of between 40:60 and 60:40.

In the compound of formula (IV) preferably, R, R1, R2 and R3 are independently from each other OR4, wherein R4 is a linear or branched Ci - Ce alkyl group, more preferably R4 is a linear or branched Ci - Ce-alkyl, most preferably linear or branched C2 - Cs-alkyl.

Even more preferably R4 is ethyl, iso-propyl, n-propyl, iso-butyl or n-butyl.

Therefore, the present invention also relates to a process (P4), which is process (P), (P1), (PT), (P2), (P2’) or (P3), wherein the compound of formula (IV) R4 is a linear or branched C2 -Ce-alkyl.

Therefore, the present invention also relates to a process (P4’), which is process (P), (P1), (PT), (P2), (P2’) or (P3), wherein the compound of formula (IV) R4 is a linear or branched C2 -Cs-alkyl.

Therefore, the present invention also relates to a process (P4”), which is process (P), (P1), (PT), (P2), (P2’) or (P3), wherein the compound of formula (IV) R4 is chosen from a group consisting of ethyl, iso-propyl, n-propyl, iso-butyl and n-butyl.

In the compound of formula (IV) R, R1, R2, R3 and R4 can be the same substituent, but they can also be different from each other.

Preferably R, R1, R2, R3 and R4 have the same meanings.

In the process according to the present invention the catalyst, which is the compound of formula (IV) is usually and preferably used in an amount of 1 - 20 mol-% (in regard to the amount of TPPO), more preferably in an amount of 1 - 15 mol-%, most preferably in an amount of 6 - 14 mol-%.

In a preferred embodiment, the process is carried out in the presence of a catalyst being of a mixture of compounds (IV)-Ti and (IV)-Zr which is usually used in an amount of 1 - 20 mol-% each, preferably in an amount of 1 - 15 mol-%, more preferably in an amount of 1 - 12 mol-%, and most preferably in an amount of 1 - 10 mol-% (in regard to the amount of TPPO).

Thereby, the amount of the compound (IV) being a mixture of compound (IV)-Ti and of compound (I )-Zr is used in a ratio of (IV)-Ti : (I )-Zr of between 3:1 and 1 :3, preferably between 3:2 and 2:3, and most preferably in a ratio 1 :1 , amounting to a typical amount of compound (I )-Ti of 1 - 10 mol-% and a typical amount of compound (I )-Zr of 1 - 10 mol-%, more preferably amounting to a typical amount of compound (IV)-Ti of 1 - 5 mol-% and a typical amount of compound (IV)-Zr of 1 - 5 mol-%.

In another embodiment of the present invention, the process as described hereinabove is carried out in the presence of a catalyst, wherein if the catalyst is a mixture of compound (IV)- Ti and of compound (IV)-Zr, all 4 substituents R4 are identical within the same compound (IV), thus compound (IV)-Ti may have 4 identical substituents that are identical or different from the 4 identical substituents of compound (IV)-Zr. Preferably, the process as described hereinabove is carried out in the presence of a catalyst, wherein in case a mixture of compounds (IV) is used, R4 is different for compound (IV)-Ti than for compound (IV)-Zr, e.g., in such a mixture compound (IV)-Ti may comprise iPr as R4 whereas the compound (IV)-Zr may comprise nBu as R4 substituent.

According to the present invention, in step 1 the compound of formula (IV) is typically and preferably used as a solution of the compound (IV) in a suitable solvent. Suitable solvents are selected from a group consisting of ethyl, iso-propyl, n-propyl, is-butyl, and n-butyl alcohol. Preferably, said solvent corresponds to the substituent R4 used in said compound (IV). Preferably, compound (IV) is used in said solution of compound (IV) in said solvent in a concentration of up to 100%, preferably between 20 to 99% w/w.

Therefore, the present invention also relates to a process (P5), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’) of (P4”), wherein the compound of formula (IV) is used in an amount of 1-20 mol-% (in regard to the amount of TPPO), more preferably in an amount of 1 - 15 mol-%, most preferably in an amount of 6 - 14 mol-%. In the process according to the present invention, step 1 is carried out at elevated temperature. Preferably step 1 is carried out at a temperature of 100°C to 200°C, more preferably at 150°C to 180°C.

Therefore, the present invention also relates to a process (P6), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”) or (P5), wherein step 1 is carried out at a temperature of 100°C to 200°C.

Therefore, the present invention also relates to a process (P6’), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”) or (P5), wherein step 1 is carried out at a temperature of 150°C to 180°C.

In case the solvent (or the mixture of solvents) are low boiling solvents then step 1 is preferably carried out in an autoclave.

The reaction time of step 1 of the process according to the present invention is usually several hours. Usually and preferably the reaction time of step 1 of the process according to the present invention is 3 to 10 hours.

Therefore, the present invention also relates to a process (P7), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6) or (P6’), wherein the reaction time of step 1 is 3 to 10 hours.

In preferred embodiment, after step 1 , the solvent or the mixture of solvents is removed (in full or partially) from the reaction mixture. This step (step 1a) can be carried out by using commonly known methods (such as distillation).

Therefore, the present invention also relates to a process (P8), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’) or (P7), wherein after step 1 , the solvent or the mixture of solvents is removed (in full or partially) from the reaction mixture.

After step 1 (or after step 1a), the reaction mixture is cooled down to a temperature below 100°C, usually down to a temperature between 40°C to 90°C.

Therefore, the present invention also relates to a process (P9), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7) or (P8), wherein after step 1 (or after step 1a) the reaction mixture is cooled down to a temperature below 100°C. Therefore, the present invention also relates to a process (P9’), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7) or (P8), wherein after step 1 (or after step 1a) the reaction mixture is cooled down to a temperature between 40°C to 90°C.

In step 2 of the process according to the present invention (which is carried out after step 1 or 1a), at least one alcohol of formula (V)

R₅-OH, wherein R5 is a linear or branched Ci - Ce alkyl moiety is added to the reaction mixture.

Preferably, R5 is a linear or branched Ci - C4-alkyl moiety.

More preferably, the at least one alcohol of formula (V) is chosen from the group consisting of methanol, ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol. Most preferably, the at least one alcohol of formula (V) is iso-propanol.

Therefore, the present invention also relates to a process (P10), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9) or (P9’), wherein the alcohol of formula (V) R5 is a linear or branched Ci - C4-alkyl moiety.

Therefore, the present invention also relates to a process (P10’), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9) or (P9’), wherein the alcohol is chosen from the group consisting of methanol, ethanol, n-propanol, iso-propanol, n-butanol and iso-butanol, preferably iso-propanol.

The alcohol of formula (V) is usually and preferably added to reaction mixture in molar excess (in regard to TPPO). Usually, the at least one alcohol is added in at least an amount which is 1 - 30 mol equivalent (in regard to TPPO).

Therefore, the present invention also relates to a process (P11), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9), (P9’), (P10) or (P10’), wherein the at least one alcohol of formula (V) is added to reaction mixture in molar excess (in regard to TPPO).

Therefore, the present invention also relates to a process (P1 T), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9), (P9’), (P10) or (P10’), wherein the at least one alcohol of formula (V) is added to reaction mixture in at least an amount which is 1 - 30mol equivalent (in regard to TPPO). Preferably the reaction mixture is heated to a temperature of 40 to 90°C in step 2.

Therefore, the present invention also relates to a process (P12), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9), (P9’), (P10), (P10’). (P11) or (P1 ), wherein step 2 the reaction temperature is between 40 to 90°C.

At the end, the reaction mixture is cooled down to a low temperature, usually between -10°C to 10°C.

Therefore, the present invention also relates to a process (P13), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9), (P9’), (P10), (P10’). (P11), (P1 T) or (P12), wherein at the end of the reaction of step 2 the reaction temperature is cooled down to a temperature of -10°C to 10°C.

At this point in time TPP is precipitated and can be filtered off.

Usually, the obtained product (TPP) is washed with the same alcohol of formula (V) (or mixture of alcohols), which is already added during step 2.

As an additional feature it is possible to further treat the mother liquid obtained at the end of step 2 and after the (optional) washing

The filter cake was washed with the same alcoholic solvent used in the prior step.

Moreover, we found that upon treating the mother liquor with ammonium hydroxide (which is an aqueous solution of NH3) has some surprising and advantageous effects.

When adding the ammonium hydroxide, a Si-containing compound formed a solid precipitate that also incorporated the titanium derived from the catalyst is formed and can be removed from the solution.

By this unexpected finding it was possible to remove almost all the silicium and titanium from the alcoholic aqueous solution.

Therefore, the present invention also relates to a process (P14), which is process (P), (P1), (PT), (P2), (P2’), (P3), (P4), (P4’), (P4”), (P5), (P6), (P6’), (P7), (P8), (P9), (P9’), (P10), (P10’). (P11), (P1 T), (P12) or (P13) wherein in a third step (step 3), the mother liquor (obtained after step 2) is treated with ammonium hydroxide. Usually and preferably, the mother liquor is treated with ammonium hydroxide having a concentration of 1-30 weight-% (wt-%), based on the total weight of the ammonium hydroxide, of NH₃ in H₂O.

Therefore, the present invention also relates to a process (P15), which is process (P14), wherein the ammonium hydroxide having a concentration of 1-30 weight-% (wt-%), based on the total weight of the ammonium hydroxide, of NH₃ in H₂O.

The treatment of the mother liquor is carried out at a temperature of 40°C to 120°C, preferably 60°C to 100°C.

Therefore, the present invention also relates to a process (P16), which is process (P14) or (P15), wherein step 3 is carried out at a temperature of 40°C to 120°C.

Therefore, the present invention also relates to a process (P16’), which is process (P14) or (P15), wherein step 3 is carried out at a temperature of 60°C to 100°C.

Optionally, the treatment of the mother liquor can be carried out in the presence of at least one surfactant.

Suitable surfactants are cetyltrimethylammonium bromide, myristyltrimethylammoniumbromide, dodecyltrimethylammoniumbromide or hexadecyltrimethylammoniumbromide.

Therefore, the present invention also relates to a process (P17), which is process (P14), (P15), (P16) or (P16’), wherein step 3 is be carried out in the presence of at least one surfactant.

Therefore, the present invention also relates to a process (P17’), which is process (P14), (P15), (P16) or (P16’), wherein step 3 is be carried out in the presence of at least one surfactant chosen from the group consisting of cetyltrimethylammonium bromide, myristyltrimethylammonium bromide, dodecyltrimethylammonium bromide, hexa-decyl- trimethylammonium bromide, cetyltrimethylammonium chloride, myristyltrimethylammonium chloride, dodecyltrimethylammonium chloride, and hexa-decyl-trimethylammonium chloride.

Optionally, tetratethylortosilicate can be used as well in the treatment of the mother liquor.

Therefore, the present invention also relates to a process (P18), which is process (P14), (P15), (P16), (P16’), (P17) or (P17’), wherein step 3 is be carried out in the presence of tetratethy I o rtos i I i cate . Furthermore, the present invention relates to the use of the triphenylphoshine (TPP) manufactured by the process described hereinabove for the manufacture of a carotenoid selected from the group of carotenoids, including alpha-, beta-, gamma- or delta-carotene, , apocarotenal, beta-apo-8’-carotenal, beta-apo-12’-carotenal, lycopene, bixin, or including lutein, astaxanthin, canthaxanthin, citranaxanthin, cryptoxanthin, flavoxanthin, violaxanthin, or zeaxanthin.

The present invention also relates to a method for the manufacture of carotenoids comprising the steps of i) manufacturing TPP from a waste containing TPPO according to process described above, ii) subjecting the building block compounds for a respective carotenoid to a coupling reaction with the TPP as coupling reagent manufactured according to step i) hereinabove, and iii) recovering the respective carotenoid.

A coupling reaction as defined hereinabove may be any reaction for formation of C=C bonds, preferably a Wittig reaction, as described in DE954247. Building block compounds according to the present invention may have at least two structures having independently of each other C3, C4, C5, C6, C7, C8, C9, C10, C11 , C12, C13, and at least one functional group suitable for reacting accordingly in such a coupling reaction.

The present invention also relates to a carotenoid that has been obtained by the method described hereinabove, wherein the carotenoid is selected from the group of carotenes, including alpha-, beta-, gamma- or delta-carotene, apocarotenal, beta-apo-8’-carotenal, beta- apo-12’-carotenal, lycopene, bixin, or from the group of xanthophylls, including lutein, astaxanthin, canthaxanthin, citranaxanthin, cryptoxanthin, flavoxanthin, violaxanthin, or zeaxanthin.

The following examples illustrate the invention. EXAMPLES

Example 1 :

70 g of TPPO were loaded in an autoclave and 270 g of toluene were added. 37 g of PMHS was added. 7 g of Ti(OiPr)4 were added. The autoclave was closed, and the reaction mixture heated to 170°C for 6 hours. After this time, the reaction mixture was cooled to 55°C. Toluene was distilled off (>90% of the initially used amount). 169 g of iPrOH (iso-propanol) were added and the reaction temperature was kept at 55°C until the solids were dissolved. The reaction mixture was cooled to 0°C to crystallize the TPP. The TPP was filtered off and washed with iPrOH. Finally, the TPP was dried yielding 55 g of material.

Example 2:

70 g of TPPO were loaded in an autoclave and 270 g of toluene were added. 32 g of PMHS and 5.5 g of Ti(OiPr)4 were added. The autoclave was closed, and the reaction mixture heated to 170°C for 6 hours. After this time, the reaction mixture was cooled to 60°C. Toluene was distilled off (>90% of the initially used amount). 169 g of iPrOH were added and the reaction temperature was kept at 60°C until the solids were dissolved. The reaction mixture was cooled to 2°C to crystallize the TPP. The TPP was filtered off and washed with iPrOH. Finally, the TPP was dried yielding 46 g of material.

Example 3:

70 g of TPPO were loaded in an autoclave and 270 g of toluene were added. 38 g of PMHS and 8.5 g of Ti(OnBu)4 were added. The autoclave was closed, and the reaction mixture heated to 170°C for 6 hours. After this time, the reaction mixture was cooled to 57°C. Toluene was distilled off (>90% of the initially used amount). 168 g of iPrOH were added and the reaction temperature was kept at 65°C until the solids were dissolved. The reaction mixture was cooled. The TPP was filtered off and washed with iPrOH. The TPP was filtered off and washed with iPrOH. Finally, the TPP was dried yielding 55.5 g of material.

Example 4:

70 g of TPPO were loaded in an autoclave. 360 g of toluene and 19 g of PMHS were added. The autoclave was closed, and the reaction mixture heated to 170°C and the catalyst, Ti(OiPr)4, 7.5 g, was dosed over a period of 2 h . After the dosage was completed, the reaction mixture was cooled to 53°C. Toluene was distilled off (>90% of the initially used amount). 170 g of iPrOH were added and the reaction temperature was kept at 60°C until the solids were dissolved. The reaction mixture was cooled to 0°C to crystallize the TPP. The TPP was filtered off and washed with iPrOH. Finally, the TPP was dried, yielding 33.6 g of material.

Example 5:

75 g of TPPO were loaded in a reactor and 375 g of mesitylene were added. 41 g of PMHS and 7.7 g of Ti(OiPr)4 were added. The reaction mixture was heated to 150°C for 14 hours. After this time, the reaction mixture was cooled to 90°C. Mesitylene was distilled off (>90% of the initially used amount). 180 g of iPrOH were added and the reaction temperature was kept at 60°C until the solids were dissolved. The reaction mixture was cooled to 0°C to crystallize the TPP. The TPP was filtered off and washed with iPrOH. Finally, the TPP was dried yielding 55 g of material.

Example 6:

235 g of TPPO waste containing 149.3g TPPO, methanol and water were loaded in a 2L double jacketed glass reactor. To the brownish solution 720 g mesitylene was added. 162 g methanol, water and mesitylene mixture was distilled (800 to 160 mbar, 60° to 90°C) until KF < 0.1%. To the suspension 15.4 g Ti(OiPr)4, 79.9 g PMHS and 102 g mesitylene were added. The reaction mixture was heated to 170°C for 12 hours (slight reflux). After this time, the reaction mixture was cooled to 60°C. The crude solution was added over the course of 2 h to a second 2L double jacketed glass reactor previously charged with 181 g 45% w/w KOH. When hydrogen evolution seized, stirring was stopped whereas two phases developed. 237 g of aqueous phase was drained. The organic phase was concentrated (50 to 10 mbar, 90°C) to 142 g oily residue. 350 g methanol was added and stirring was continued at 60°C for 1 h. Temperature was reduced within 2 h to 0°C and the slurry was filtered. TPP was washed with 50 g cold methanol and dried yielding 117 g of material.

Example 7:

118g of TPPO waste containing 75g TPPO, methanol and water were loaded in a 2L double jacketed glass reactor. To the brownish solution 360g mesitylene was added. 81g methanol, water and mesitylene mixture was distilled (800 to 160mbar, 60° to 90°C) until KF < 0.1 %. To the suspension 7.7g Ti(OiPr)4, 41 g PMHS and 51g mesitylene were added. The reaction mixture was heated to 170°C for 12 hours (slight reflux). After this time, the reaction mixture was cooled to 60°C. The crude solution was added over the course of 2h to a second 2L double jacketed glass reactor previously charged with 100g KOH 20%-w/w. When hydrogen evolution seized, stirring was stopped whereas two phases developed. 119 of aqueous phase was drained. The organic phase was concentrated (50 to 10mbar, 90°C) to 71g oily residue. 180g iPrOH was added and stirring was continued at 60°C for 1h. Temperature was reduced within 2 h to 0°C and the slurry was filtered. TPP was washed with 50 g cold iPrOH and dried under vacuum yielding 55 g of material.

Example 8:

128g of TPPO was loaded in a 2L double jacketed glass reactor. To the yellow solution 513g of diethylbenzene (mixture of o,m,p-isomers) was added. To the suspension 6.63g Ti(OiPr)4 and 10.9g of Zr(OnBu)4 as well as 67.9g PMHS were added. The reaction mixture was heated to 170°C for 8 hours. After this time, the reaction mixture was cooled to 100°C and the solvent was removed by distillation. The crude product was cooled to 50°C and 350g of iPrOH were added and stirred until all solids were dissolved. The reaction mixture was slowly cooled and seeded. The temperature was further reduced to 0°C and the product TPP was filtered off and washed with 50g cooled iPrOH. After this, the product was dried under vacuum, yielding 98g of TPP.

Example 9:

128g of TPPO was loaded in a 2L double jacketed glass reactor. To the yellow solution 509g of Solvesso 100 (solvent Naphtha (Petroleum) by Exxon Mobile) was added. To the suspension 6.61g Ti(OiPr)4 and 10.8g of Zr(OnBu)4 as well as 67.8g PMHS were added. The reaction mixture was heated to 170°C for 6 hours. After this time, the reaction mixture was cooled to 120°C and the solvent was removed by distillation. The crude product was cooled to 50°C and 350g of iPrOH were added and stirred until all solids were dissolved. The reaction mixture was slowly cooled and seeded. The temperature was further reduced to 0°C and the product TPP was filtered off and washed with 50g cooled iPrOH. After this, the product was dried under vacuum, yielding 96g of TPP.

Typical example for treatment of mother liquor (step 3):

500 g of water and 100 g of NH4OH 20%-w/w are added to a reactor. The mixture is heated to 80°C and 100 g of the mother liquor resulting from the TPP filtration (examples 1-5, 8, 9) is added over 90 min. the reaction mixture is stirred for another hour. The formed, white precipitate is filtered off and dried to yield 18 g of material.

Claims

1. A process of producing triphenylphosphine (compound of formula (I)) wherein a first (step 1) triphenylphosphine oxide (the compound of formula (II)) is reacted with the compound of formula (III)

(CH3)3Si-O-(CH₃(H)Si-O)n-Si(CH₃)3 (III) wherein n is a value between 10 and 100’000 in the presence of at least one catalyst of formula (IV) wherein

M is titanium (Ti) or zirconium (Zr), or a mixture thereof, and wherein

R₅-OH (V), wherein

Rs is a linear or branched Ci - Cs alkyl moiety is added to the reaction mixture.

2. The process according to claim 1 , wherein the at least one aromatic solvent is chosen from the group consisting of benzene, benzene substituted with one or more Ci-C4-alkyl group and benzene substituted with one or more OCi-C4-alkyl group, or mixtures thereof, or wherein the at least one alkane is a C4-Cis-alkane, which can be linear, branched or cyclic, or mixtures thereof.

3. The process according to any of the preceding claims, wherein the catalyst of step 1 is a mixture of compound (IV) wherein M is titanium and of compound (IV) wherein M is zirconium.

4. The process according to claim 3, wherein the ratio of compound (IV) with M being titanium and the compound (IV) with M being zirconium, (IV)-Ti : (IV)-Zr, is between 1 :99 and 99:1 , preferably the ratio is between 20:80 and 80:20, most preferably between 40:60 and 60:40.

5. The process according any of the preceding claims, wherein the compound of formula

(III) is added in an amount of 1.0 to 4 mol-equivalent (calculated in respect to the active hydrogen content of PMHS in regard to the amount of TPPO).

6. The process according any of the preceding claims, wherein the compound of formula

(IV) R4 is a linear or branched Ci -Cs-alkyl, and preferably wherein R4 of the compound of formula (IV) is chosen from a group consisting of ethyl, iso-propyl, n-propyl, iso-butyl, and n- butyl.

7. The process according any of the preceding claims 3 to 6, wherein in case a mixture of compounds (IV) is used R4 is different in compound (IV)-Ti than in compound (IV)-Zr.

8. The process according any of the preceding claims, wherein the compound of formula (IV) is used in an amount of 1-20 mol-% (in regard to the amount of TPPO).

9. The process according any of the preceding claims, wherein step 1 is carried out at a temperature of 100°C to 200°C.

10. The process according any of the preceding claims, wherein after step 1 , the solvent or the mixture of solvents is removed (in full or partially) from the reaction mixture, and wherein in the alcohol of formula (V) R5 is a linear or branched Ci - C4-alkyl moiety, or preferably R5 is a branched Ci - Ce alkyl moiety, or more preferably wherein the alcohol of formula (V) is iso-propanol (iPrOH).

11. The process according any of the preceding claims, wherein the at least one alcohol of formula (V) is added to reaction mixture in molar excess (in regard to TPPO).

12. The process according any of the preceding claims, wherein in a third step (step 3), the mother liquor (obtained after step 2) is treated with ammonium hydroxide, and wherein the ammonium hydroxide preferably has a concentration of 1-30 wt-%, based on the total weight of the ammonium hydroxide, of NH3 in H2O.

13. The process according to claim 12 or claim 13, wherein step 3 is carried out at a temperature of 40°C to 120°C, and wherein step 3 is preferably carried out in the presence of at least one surfactant.

14. A method for the manufacture of carotenoids comprising the steps of i) manufacturing TPP from a waste containing TPPO according to any of the preceding claims, ii) subjecting the building block compounds for a respective carotenoid to a coupling reaction with the TPP as coupling reagent manufactured according to step i) hereinabove, and iii) recovering the respective carotenoid.

15. A carotenoid obtained by the method according to claim 14.

16. Use of the triphenylphoshine (TPP) manufactured by the process according any of the preceding claims for the manufacture of a carotenoid selected from the group of carotenoids, including alpha-, beta-, gamma- or delta-carotene, apocarotenal, beta-apo-8’-carotenal, beta- apo-12’-carotenal, lycopene, bixin, or including lutein, astaxanthin, canthaxanthin, citranaxanthin, cryptoxanthin, flavoxanthin, violaxanthin, or zeaxanthin.