CA1069937A - Production and use of quaternary phosphonium halides - Google Patents

Abstract

PRODUCTION AND USE OF QUATERNARY PHOSPHONIUM HALIDES

ABSTRACT OF THE DISCLOSURE:

Production of quaternary phosphonium halides of the general formula:
[R1R2R3R4P]X, in which R1, R2, R3 and R4 stand for identical or different alkyl groups having from 1 to 4 carbon atoms and X stands for halogen, especially for chlorine or bromine. The compounds are more especially made by flowing hydrogen phosphide or a primary phosphine R1PH2 or secondary phosphine R1R2PH or tertiary phosphine R1R2R3P and an alkyl halide R4X in a molar ratio from 0.02 to 10, at a temperature from 100 to 500°C, under a pressure of up to 10 atmospheres gauge and for a period from 0.5 to 500 seconds over a catalyst and separating the resulting quaternary phosphonium halides from the reaction gas.
The halides so made are used for making trialkyl-phosphine oxides and trialkylphosphines.

Description

9~9 3~7 !

- H 1141 /a/b : ;
~.
. . .
The present invention rel~,es to a novel procea~ for making quate~lary phosphonium halide~ of the gener~
formula - ':
in whlch R1, R2~ ~3 and R4 stand for identical or di~ferent alkyl groups ha~ing from 1 ~o 4 carbon atoms and X stands for a halogen atom, especialIy for a ;
chlorine or bromine atom, and to-the use of the comp~und~
;~ so made.
- Quaternary phosphonium halides are commonly mad~ by .
reactin~ a tertiary phosphine wi-th a hydroc~rbon halide ' in accordance with the following e~uation:
, . , . , , . , . . ,, ~ . . . ..
::. . , ~ ,~,,,.............. ~
R3P ~ R~ / R4 _7 in which R stands for a hydrocarbon and X stands for .
halogen~
, 20 ~ Tetramethylphosphonium iodide is more especially produced from trimethyl phosphine and methyl iodide in etheral dilution (J.Chem.Soc. (London)~ 192~ pages 2342 , ~ . , . - .~
and 1933, page 989).
. , ~ .
A fur~her process describes the additive combination of tertiary phosphines with-compounds having an acti~ated double bond in the presence of a mineral acid, ., ~ .. ~.~
in accordance with -the following equation~
, . , . - , ' R3P ~ CH2 = CH-CN + ~Br = ~ R3P-CH2-CH2-CN_7Br~

~Chem. Berichte 94 (1961), page 1331 and Gèrman .
. . . .
:~ - 2~

.
. ~ .

C ` ~ 9~3}7 Published Specif~.catiori "Auslegeschri~t" 1 045 401).
These -two processes are, how~ver~ not ~ully s~tisfactory inasmuch as very expensive tertiary .``
phosphines are required to be us~d as startin~ materlals therei~. .
I~ is also known that phosphonium haiides can b~
made by reactin~ an alkyl halide with white phospho~ls a~ ~60C in a bomb tube (cf. German Published SpeciX~cation "~uslegeschrift" 1 294 376).
Thi~ latter process is carried out under pressure~
whiGh lS disadvantageous. Il is also krlown that quaternary - phosphonium halides can be produced by reacting a phosp~ine, a primary or secondary phosphine (in which phosphines the hydrogen is fully replaced by a metal~
with an alkylene halide (Chem. Berich-te 92 (1959), pages -1118 and 2088).

; Me3P + 4 RX = / R4P_7 X + 3 Me~
Me PR + 3 RX = / R4P 7 X -~ 2 MeX

2 _ _ : . ' . MePR2 + 2 RX = / R4P 7 X + MeX

(Me - alkali me~al; R = alkyl radical; X - halogen) In this process it is necessary first to prepare-the alkali metal phosphides in a ~ery expensive separate operation in liquid ammonia with the use of alkali metals, which are di~icult to handle. The direct alkylation of free phosphine or free primary and secondary ~.
alkyl phosphines has long been held impossible in the ~-literature (cf. Houben-Weyl 9 "Methoden der Organischen Chemie", vol. XII/I (1963), page 97).
In clear contrast with this9 the present lnvention -- 3 ~

~L~69~3~

now unexpectedly provides in ~he process for making quaternary phosphonium halides of the general formula [R4P3X, in which R is identical or different alkyls having from 1 to ~ carbons and X is chlorine or bromine, the improve-ment which comprises reacting hydrogen phosphide as starting material with an alkyl halide ~X, R and X having the meaning given above in a molar ratio from 0.02 to 10, preferably O.OS to 2, at a temperature from 100 to 500C, preferably 150 to 350C, within a gas atmosphere inert to the reaction mixture, under a pressure of up to 10 atmospheres gauge, preferably at ~- atmospheric pressure, and for a period of time of about 210 seconds by flowing the gaseous reactants over a catalyst selected from the group con-sisting of active carbon, a finely divided metal from the first or eighth subgroup of the Periodic System of the elements and mixture of such metals;
and separating the resulting quaternary phosphonium halides from the reaction gas.
The above reaction may be effected in a fixed bed reactor as well as in a flow bed reactor.
Active carbon, especially active carbon having a BET-surface area of more than 10 m2/gJ is particularly well adapted for use as a catalyst. It is good practice to employ the active carbon in the form `-~
of particles having a size from 011 to 10 mm, for use in a fixed bed -reactor, and to employ pulverulent active carbon, for use in a ~
~ , ~` r ,~' ' :
' ~

1 .

~6~93~
flow bed reactor. Further use~ul catalys-ts comprise metals belonging t,o the first or eighth subgroup o~ the Periodic System of -t:he elements, which may be used alone or in combination, e~g. gold9 plati~um or palladium~ It ..
is possible for these metals to be deposited on a carrier :
being inert under the reaction conditions, such as Al203 or SiO29 for example. .
Needless to say unreacted starting material issuL~g from the reactor may be separated from the quate~nary phosphonium halid.es and then recycled to be used again in the.process.
The reactions which occur in the reactor are believed ` to be based on -the ~ollowing empirical ~ormulae: :

PH3 ~ 4 R4X = / R4P 7 x ^t 3 HX
R1PH ~ 3 R4X = ¦ R R3P_7 X ~
R1R2pH ~ 2 R4X _ /~R1R2R2P 7 X -tjHX
:. R1R2R3p + R4X = /-R1R2R3R4P 7 X ~-.
` As resul-ts it is possible, depending on the phosphine ; 20 used as starting material in each particular case, to ~: ` produce symmietric quaternary phosphonium halides having identical or di.fferent alkyl groups ~inked thereto. In carrying out -the present process 9 it is immaterial whether the starting material is used in admixture Wit}l ` i one or more inert gases. Those quate~nary phosphonium halides 9 which have a melting point lower than the reaction temperature, are separated from the reaction gas downstream o~ the catalyst by condensation and purified in known manner, e.g. by extraction and :~ ~0 recystallization. In those case,s in which melting point ' - , . ~ - , .~ . ' . . . . .

~ 39~7 and vapor prG-.ss~lre of -khe ~uaternary PhosPhonium hali~es do not permit removing -them from the reac-tor during th~
reaction at the temperature selected, the ca-talyst is allowed -to become saturated with the particular phosp~onium haljde, where upon the reaction is interrupted. Followlng this, the catalyst is treated in known fashion, e.g~ with the aid of water or alcohol or another suitable solv~n~, so as to dissolve the phosphonium halide thereon~ wh~ch is then separated from the resulting solution, if desired 1Q after evaporation of the solvent. Once the solvent ha~
..
been expelled; it is possible for the catalyst so re~c.tiva~
whîch need not be removed from the reac-tor~ to be used again.
The process of the present invention9 which is naturally not limited to the embodiment specifically .
described herein, enables quaternary phosphonium ~alides to be produced in commercial quantities from readily -accessible alkyl halides R4X and hydrogen phosphide, which is a by-product being obtained in commercial : . .
quantities in the production of sodium hypophosphite, and from the following organophosphines: R1PH2; R1R~PH
and ~2R3P, which in turn are readily obtainable b~ the ~rocess described in Belgian Patent No. 825 541. The ~ua-ternary phosphonium halides produced in accordanc~
with the present invention are important in-termediates in the ~eld of flame-proofing agents and extractants, ~or example.
A further object o~ the present invention relates to the use of tetralkylphosphonium halides made in ac~ordance therewith for the production of trialkyl phosphine oxide3 ~069~3~

of the general..~ormula R~R2R3Po, in whlch R ~ R and R3 have the meaningsgiven hereinabove.
I~ has been described that trialkylphosphi~o oxides9 :~`or ~xamp^le, can be made by oxidi.zi~g trialkylphosph~nes or ~y subjecting -te-tralkylphosphoni.um hydroxides to thermal decomposition. Fur-ther kna~m processes descr~'be the reaction of phosphorus halides wi-th organo~metal compounds, e.g.-P(O)X~ + 3 RMgX ~ R3P~0) + 3M~2, or the addit~ve combination of cLlefins, aldehydes or .- - :
~ 10 ketones with primary or secondary phosph:ine oxide~ 7 e.g. ~, - - R2P(O)H + R2CH - CH2- --- > R1P(o~R3. (G.M.Ko30lapof~
and L. Maier~ Organic Phosphorus Compounds, Vol. 3, ~.
Wiley-Interscience, New York ~i972)). ;:
These however are proçesses whi.ch can scarcely be effected on a commercial scale ina~much as they use -' . starting material, which is preparecl in a plu.rali$y of' ., processing sta~es and therefore very expensive.
.,.~ . We have now unexpe~tedly ~ound that trialkylphosphi.ne ' ;
' oxides are readily obtainable ~rom hyd.rogen phosphide, ~, 20 , primary, secondary or tertiary phosphines provided th~t " ,' ', ~' the tetralkylphosphonium halides made in accordance with the present invention are used as the starting material ~:;. for making the said phosphine o~ide~., To this end) the .
tetralkylphosphonium haiides are first reacted in kno~m , manner with an alkall metal hydroxide9 then neutralized ~:
' and trialkylphosphine oxide is separa-ted from the '' neutralized material. . .
:: .
. It is -technically good practice to effect th~
alka~ine hydrolysis at elevated temperature so as to ~' ~0 arrive at the tertiary'phosphine oxide staee via the ~. .

tetralkylphosphoniu~ halide s-tage~ ;
The hydrolysis is believed to initially cause the formation o~ tetralkylphosphonium hydrsxides which ar~
transformed later into trialkylphosphine oxides, while -.
an alkane is eliminated. The following empirical formulae are a diagrammatic representation o the reac-tion which oc&urs: - -~ R4P_7 X ~ N~OH ~ R4P_7 OH ~ NaX
- / R4P_7 OH - ~ / R3P_7 (O) ~ RH

tG.M. Kosolapo~f and L.~Maier~ Organic Phosphorus Compounds, vol. 2 3 Wiley~Interscience, New York (197~)).
; Pure trialkylphosphine oxide is obtained by suspending tetralkylphosphonium chloride, which may have been separated earlier, in a 40-50 % sodium hydroxide r solution and reacting the suspension at 120--150C~ The resultin~ phosphine oxide solution i5 neutrali~ed by means of hydrochloric acid and then evaporated to dryness.
The evaporation residue is taken up in anhydrous ethanoI
.
2,0 and freed from sodium chloride by filtration. Once the ~ .
- solvent has been dis-tilled off, pure trialkylphosphine `
oxide is obtained.
~ .. . . . . .
The process of the present invention is the first to permit the production of Iow tertiary phosphine o~ides ~ from hydrogen phosphide via the tetralkylphosphonium - chloride stage, which is a very desirable step forward in the art.
Trialkylphosphine oxides Yind widespread uses as detergents, dyei~g auxiliaries, catalysts, corrosion inhibitors and as interesting intermediates for the .
, ~,. . .

production o~ ~lamep~oo~ing agentsp pl.a~t protective agents and pha~ma~eutical preparationsD
- The present inve~ion also relates to the use of the tetralkylph~sphonium halides o~ the present in~ention ~or mak.ing trialkylphosphin~c of the general formula R~R2R3P, in whioh R1, R2 and R3 ha~e the meanings given ~ ' hereinabove.
~ t has been described that tri~lkylphosphine~ can be made by reacting a phosphorus h~lide with an organo .
` 10 metal compound, e.g. in acc~rdance with the ~ollowin~
- equation: ' - . .. ~ ;, PX3 + 3 RMgX ~ R3P + 3 MgX2 Further known processes are based on the alkylation - of phosphines, the additive combination o~ ole~lns, aldehydes or ketones with phosphines 3 e.g. in accordance wi-th the following equation: ~ ......................... .
~; R1PH ~ 2'R2CH=CH2 3 R PR2, ~ . or the 'reduction of phosphine oxide~ and phosphine : sul~ides (~.M. Kosolapof~ and L. Maier, Organic Phosphorus ~; 20 Compounds, vol. 1, ~iley-Interscience~ ~ew York (1972~
~ - .
.. These are processes which can scarcely be ef:~ected ~ on a Gommercial scale inasmuch as they use starting ~ .
`- material which is prepared by a plurality of steps and tharefore very expensive.
We have now unexpectedly found that trialkylphosphlnes.
are readily obtainable from hydrogen phosphide, primary, secondary or tertiary phosphines provided that the tetralkylphosphonium halides o~ the present invention are used as the starting material for making the sald

3~ phosphines.

9 . .

~. .

. ' , '~ ~ ' ~'.'' ' '. ' ' 7 C ~ 9937 To thi~ end~ the tetral~ylphosphonium halide~ are heate~ in Gontact with a stream of an .inert gas to ~emperature~ higher ~han 300CC, th~ resulting tri~lkyl-~ -phosphoniu~ halides and/or trialkylpho~phines are , abs~rb~d, preferably in hydrochloric acid~ and the resulting trial~yl phosphonium halid~ solution lS
treated in known ma~erJ e.g. by adding an alkali metal hydroxide ther~t~$ so a~ to libe~ate an~ separa-t~ the-trialkylphosphines therefrom~ :
,. - - - ::: . *
` 10 :T'he s~arting ma~erial should preferably be heated to temperatures from 380 -to 480C, more preferably 400 to 420c, and with the use of nitrogen as the inert gas.
The trialkylphosphines are easy to libera-te from the trialkylphosphonium halide solut:ion in hydrochloric acid by admixing the solution with an alkali metal : h~droxide solution so as to establish a pH from 1~-to 14. ~ ::
e trialkylphosphines set free in the manner jUSt . described are separated.from the alkaline solution in accordance with their respective boiling points~ i.e~
by distillation where low-boiling products are conc~rned~
. or by extraction where high-boiling produ~ts are conc-erned.
-- -The trialkylphosphine and/or trialk~lph~sphonium ~- halide are often obtained together with an alkyl halide/
alkane/hydrogen.halide-mixture. The following empirical . formulae are a diagramma-tic representation of the reactionswhich occur:

R4P~7X --- > R3 RX ~ R + HX
- - - . > / R3PH_7X ~ :

., .

. - 10 - .

~1~6~937 ~~.M. Kosola~of`~ ~nd L~ Maier, Organic Phosphorus Compourlds9 ~rol. 1 9 Wiley-Interscience, New York (197~
By such use of the tetralkylphosphonium halides made in accordance with the present inven~ion it is ~or the first tim0 possible -to produce low tertiary phosphi~les ~rom hydrogen phosphide~ Trialkylphosphines ~ind widespread uses as catal~sts9 e.g~ in the form of ~ -complex compounds with transi-~on me-tal compounds in the cyclization of ethylene and acetylens compounds, in the , , , . . ........ . : ~ .
polymerization of aldehydes, ethylene and àcetylene compounds, in the hydroformylation9 and in the F~
dehalogenation of halohydrocarbons.
EXA~
Tetramethylphosphonium chloride /-(CH3)4P 7Cl was prepared. ~o this end, 20 l/hr of PH3 and 100 l/hr o~
CH3Cl were mixed together and preheated to 200C.~The resulting mixture was passed at 280C and at atmospheric pressure through a reactor filled with active carbon and -~
. ,contacted the rewith for a period of 210 seconds. The ~0 suppiy o~ the PH~!CH~Cl-mixture was terminat~d after 85 ~ p hours. This corresponded to the absorbing power of the- ~ r- . ~' quantity of active carbon placed in -the reac'tor. Nitrogen ; ~
: - . - ;
was also passed -through ~he reactor for a period of 2 hours at 280C. Followin~ this, tetr~methylphosphonium chloride having a melting point higher than 400C was removed from the active carbon by treating it with warm water having a -temperature of 90C. The resulting ... . . . . .
aqueous solution was evaporated to dryness, the tetra-methylp~osphonium chloride was taken up in ethanol, precipitated with die-thylether and thereby purified.

.

.

. .: . : ..

69~37 60g ~ o~ PH3 g~ve 8 052 g o~ / (CH~)4P 7Cl. This corresponded -to a yield of 83 %. 285 g of yellow phos phoru.s and a mixture of CH3PH2, ~CH3~zPH and (CH3)3~ wer~
ob-tained as by~products. These latte~ co~pounds can be - used once again as starting mate~ials for making (CH3)4P 7Cl~ or separated and worked up by the process `
~escribed i.n Belgian Pa-tent 825 541 a~d made into r - - valuable material ~or u~e in the production o~ flame-proofing agents~ for example. .
~. --10 `EXAMPLE 2 - . ~
'!: Tëtramethylphosphoni~ chloride / (CH3)4P_7Cl wa~ ~ r- :

made. To this end 25 l!hr of CH3PH2 and 100 l/hr of CH3Cl were mixed together and preheated to 150~ The mixture so made was passed at 280C and at atmospheric pressure ~, through a reactor filled with acti~e carbQn and con-tacted ;;` : therewith for a period of 120 seconds. The supply~pf.the GH3PH2/CH3Cl-mixture was terminated after 35 hours. The other conditions were the same as those described in Example 1. 1 785 g of CH3PH2 gave 2 705 g of / (CH3)L~P 7Cl, co:rresponding to a yield of 78 %. . ~

~ .
` Tetrame~hylphosphonium chloride / (CH3~4P 7Cl was made. To this end 25 l/hr of (CH3)2PH and 75 l/hr o*
CH3Cl were mixed together and preheated to 150C. The . resulting mixture was passed at 280C and at atmospheric pressure through a reactor filled with active carbon and contacted therewith for a period of 50 seconds. The . supply of the (CH3)2PH/CH3Cl-mixture was terminated - after 17 hours. The other conditions were the same as 3 those described in Example 10 1 189 g of (CH3)2 PH gave .

. . _ 12 .

6~g37 2 062 g of / (CH3)4P_7Cl~ corresponding to a yield of ' ~5 %~
EXAMPL~ 4 Tetrame-thylphosphonium chlorid~ / ~CH3)L~P 7Cl was ma:~e. To this end, 25 l/hr of (-CH3)3P and 50 l/hr of`~
CH3~1 were m~xed together and preheated -to 1~0C. The resul~ g mixture was passed at 270C and at atmospheric - pressure through a reactor filled ~ri-th active carbon and - ~ ,, contacted therewith for a period of 18 seconds. The , ~10 supply of the (CH3)3P/CH3Cl-mixture'was terminated a~ter 8.5 hours. The other conditions were the same as those described in Example 1. 645 g of (CH3)~P gave 977 g o~ -"~
/ (CH3)4P 7Cl; corresponding to yield of 91 %. ' ; , EXAMPLE 5: , ' P~~~
, Tetramethylphosphonium chloride / (CH3)~P 7Cl was I first prepared. To this end 20 l/hr o~ PH3 and 100 l/hr ' of CH3Cl were mixed together and preheated to 200C. m e ; resulting mixture was passed at 280C and at atmospherlc pressure through a reactor filled with active carbon and , -- contacted-therewith',for a period of 210 seconds. The ~ ;bh;, ~upply'o-f the PH3/CH3Cl~mixture was te~linated after 85;- -hours~ This corresponded to the absorbing power of the quantity of active carbon placed in the reactor. Nitrogen ~;
, was also passed through the reactor for a period of 2 hours at 280C. Following this, tetramèthylphosphonium chloride havinga melting point higher than 400C was removed from the active car'bon by treating it with warm water ha~ing a temperature of 90C. The resulting aqueous ' :-solution was evaporated to dryness, the tetramethyl-.

~ ~069~3~ ~

. phosphonium chloride was taken up i~ ethanol, presipitaked :~
: with diethyle~her and thereby purified. 2 605 g of PH3 - ga~e ~ 05~ g of / (CH3)4P 7Cl~ corre~ponding to a y~el~
~ 83 ~.
; The product so obtained was analyzed and found to contain~
:~ . Phosphorus: 24.5 weight % of P (calcula-ted 24.47 weigh~ %) Chlorine: 28~1 weight ~ o~ Cl (calculated 28.01 w~igh~ X) 8.504 g o~ ~ (CH )LP 7Cl was :: :
_ 3 ~ -treated with 25 cc of a 50 weight ~ aO~-solution at oc. 1610 cc of gas (at 20C under 768 mm ~g) wa~
collected. Gas chromatograph~ indicated tha~ the gas , .
cont~ined more than 99.9 /0 by volume of meth~ne. The - purity of the product accordingly WaB 100.00 %.
The product was used for making trimethylphosphine - :~
oxide. To this end, 30 g of / (.CH3)4]P 7Cl was suspended in 80 g of a 50 weigh-t % sodium hydroxide solution (molar ratio of NaOH to phosphonium salt = 4:1) and ..
r~acted at 120-130C. Once gas ceased ~o be evolvedt the ~- 20 whole was neutralized with the use of hydrochlorlc acid -.
and a pH-electrode, and-the solution was e~aporated in 1 rota~ing evaporator. The residue wa~ taken up in anhydrous ethanol9 sodium chloride w~s filtered off ~nd the solvent was distilled off. (CH3)3P(O) was obtained in a yield of 18 g, corresponding to a yield of 83 % of the theoretical. :
The following further experiments, in which / (CH3)4P 7Cl and NaOH were used in various molar ratios~
were made under the conditions just described~

, . , ' ~, .

~xp- (CH3~4P ~ NaOH Reaction Yield o~
No5 temp. (CH~)P(O) mol mol C

2 1.00 4 1~5 84 %
3 0.40 1 130 94 %

4 0.40 0.8 120 100 EXAMPLE 6: -: :.

Tetramethylphos,phonium chloride was prepared first / (CH3~4P 7Cl~ To this end~ ~O l/hr of PH3 and 100 ~hr of CH~Cl were mixed together and preheated -to 200C. The ^~
resulting mixture was passed a-t 280C and at atmospheric pressure through à reactor ~illed with acti~e carbon and . .
contacted therewlth for a period of 210 seconds. The supply of the PH3/CH3Cl-mixture was terminated af~er 85 hours. This corresponded to the absorbing power of the quantity of ac-tive carbon placed in the reactor.
Nitrogen was also passed through the reac-tor for 2 houra at 280C. Following this, the tetramethylphosphonium chloride having a meltin~ polnt higher than 400C was `~
eluted from the active carbon by means of warm water having a temperature of 90C.
While the tetramethylphosphonium chloride was le~t unseparated9 the aqueous / (CH3~4P 7C1 solution was treated with a 40 weight % sodium hydroxide solution and a pH-value of 12 was es-tablished with the aid o~ a pH-electrode. By heating the solution for about 1 hour to 80C while gaseous nitrogen was passed therethrough, ~ it was freed from minor proportions of monomethylphosphine, .

., ( - ~06~37 dime-thylphosp~ine and trimethylphosphine. N~-spectxoscopy showed t,hat this was suf~icient to effect the conversion of a proportion as high as 4 weight % based on the / t~}I~)4~7Cl u5ed~ into trimethylphosphine oxide. The solutio~ was then concentrated in a rotating evaporator until NaCl commenced separation and thereaf~er reacted with 2 mols o~ sodium hydroxide per mol of ~ (CH3)4P 7Cl.
Once gas ceased to be evolved, the solution was neutralized by means o~ hydrochloric acid, evaporated to dr~ness and take~ up in anhydrous ethanol. The sodium chloride was filtered off and the solvent was distilled of~. 5 520 g of trimethylphosphine oxide was obtained. This corresponded ~~
to a yield of 77 %9 based on the phos~hine used.
EXAMPLE 7: -~ . . . .
ne.
-- ~.
Trimethylphosphonium chloride / (CH3)4P 7Cl ~s prepared first. To this end, 20 l/hr of PH3 and 100 l/hr o ~H3Cl were mixed together and preheated to 200C. The resulting mixture was passed at 280C and at atmospherlc presxure through a reactor filled with active carbon, and contacted therewith for a-period of 210 seconds.
The supply o~ the PH3/CH3Cl mixture was terminated after 85 hours. This corresponded to the absorbing power of the quantity of active carbon placed in the reactor.
Nitrogen was also passed through the reactor at 280C
~ over a period of 2 hours~ Following this, tetramethyl phosphonium chloride melting at a temperature higher than 400C was removea from the acti~e carbon by washing with warm water having a temperature of 90C.
The resulting aqueous solution was evaporated to dryne~s~
.

{~ i9~

the t;e-trame~hylphosphonium chloricl~ was -taken up in ethanol~ precipitated with diethylether and purified in this manner. 2 605 g of PH~ gave 8 052 g of (CH3)4P Cl~
COrI`eSpOnding tQ a yield of 83 ~.
The prodlict so made was analyzed and found -~ contai~
24.5 weight % of P (calcula~ed: 24.47 weigh-t ~0~ and .
28.1 weigh-t ~ of Cl (calcula-ted: 28~01 weight %).
~aaaL c~ ~o~oæLv~a~ 8504 g of / (CH ) P 7C1 was -- ~ 4 --treated with 25 cc of a ~0 weigh-t % NaOH-solution at 120C. 1~10 cc of gas ~a-t 20C under 768 mm Hg) was collected~ Gas chromatography indicated that the gas contained more than 99.9 % by volume of methane. The prod~lct was substantially 100 % pure.
The product was used for making trimethylphosphine.
To this end, 24.3 g of / (CH~)4Y 7Cl was pyrolyzed in a tubular reactor heated to 420C and in contact with a stream of nitrogen (20 l/hr). The resulting phosphorus-containing reaction products were absorbed in gas-washing bottles (filled with concentrated hydrochloric acid3 downstream of the reactor. The soiutions absorbed therein were delivered -to a distilling apparatus, treated therein with a 40 weight /0 sodium hydroxide solution so as to establish a pH-value o~ 12-14 and heated to 100C.
Trimethylphosphine which distilled off (bp760 = 40C) was condensed at -30C and absorbed in toluene. Gas chromatography indicated that the material contained 11 . 4 g of trlme~hylphosphine, corresponding to a yield of 78 % of the theore-tical.
' ., ` ' ' ~

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In the process for making quaternary phosphonium halides of the general formula:

[R4P]X
in which R is identical or different alkyls having from 1 to 4 carbons and X is chlorine or bromine, the improvement which comprises reacting hydrogen phosphide as starting material with an alkyl halide RX, R and X
having the meaning given above in a molar ratio from 0.02 to 10, at a temperature from 100° to 500°C, within a gas atmosphere inert to the reaction mixture, under a pressure of up to 10 atmospheres gaugesand for a period of time of about 210 seconds by flowing the gaseous reactants over a catalyst selected from the group consisting of active carbon, a finely divided metal from the first or eighth subgroup of the Periodic System of the elements and mixture of such metals; and separating the resulting quaternary phosphonium halides from the reaction gas.

2. The process as claimed in claim 1, wherein the hydrogen phosphide and the alkyl halide are used in a molar ratio from 0.05 to 2.

3. The process as claimed in claim 1, wherein the starting materials are passed over the catalyst at temperatures from 150° to 350°C.

4. The process as claimed in claim 1, wherein the starting materials are passed over the catalyst at atmospheric pressure.

5. The process as claimed in claim 1, wherein the active carbon catalyst has a BET-surface area of more than 10m2/g.

6. The process as claimed in claim 1, wherein the reaction is effected in a fixed bed reactor with the use of particulate active carbon having a particle size from 0.1 to 10 mm.

7. The process as claimed in claim 1, wherein the reaction is effected in a flow bed reactor with the use of pulverulent active carbon.

8. The process as claimed in claim 1, wherein gold, palladium or platinum is used as the said metal catalyst.

9. The process as claimed in claim 1, wherein the said metal catalyst is deposited on a carrier.

10. The process as claimed in claim 9, wherein the carrier is Al2O3, SiO2 or a mixture thereof.

11. The process as claimed in claim 1, wherein quaternary phos-phonium halides having a melting point lower than the reaction temperature are removed from the reaction gases downstream of the catalyst by condensa tion.

12. The process as claimed in claim 1, wherein quaternary phos-phonium halides of which melting point and vapor pressure forbid removing them from the reactor during the reaction, are separated from the reaction gases by allowing the catalyst to become saturated with the resulting particular phosphonium halide, interrupting the reaction, removing the reaction product on the catalyst by treatment with a suit-able solvent and separating the phosphonium halides from the resulting solution by removing the solvent.

13. The process as claimed in claim 1, wherein the starting materials are mixed together and preheated to about 150°C and the resulting mixture is passed over the catalyst.