CA2052919A1 - Process for the produciton of guanylthiourea - Google Patents

Abstract

Abstract Process for the production of guanylthiourea The present invention provides a process for the production of guanylthiourea by the reaction of dicyandiamide with hydrogen sulphide in M-alkyl-pyrrolidone as solvent in the presence of cata-lytically-acting additives, wherein, as catalytic-ally-acting additive there is used an amine, ammonia and/or elementary sulphur with the formation of an addition compound of guanylthiourea and M-alkyl-pyrrolidone which is decomposed by treatment with an organic solvent followed by recovery of guanyl-thiourea as residue.

Description

20~2919 ~~he present invention is concerned with a process for the prDduction of ~uanylthiourea by the reaction of dicyandiamide with hydrogen sulphide in an organic solvent and isolation t~ereof.
It is known that dicya~iamia~dds hydrogen sulphide in aqueous or alcoholic medium with ~he~ormation of guanylthiourea. In spite of long reaction times or carryin~ out the reaction under pressure, the yield and purity are unsatisfaCtory, especiallg as a result of the formation of dithiobiuret.
Published Federal ~epublic of Germany Patent ~pecification DE-O~ 16 70 146 describes a process for the production of addition compounds of .~-alkyl-pyrrolidones with guanylthiourea. l;~hereas the yield of addition product is, with 93%, satisfactory, in the case of the described recrystallisation with alcohol, mucb o, the desired product is lost so that this process appears to be unsuitable for use on a technical scale.
~ herefore, it is an object of the present invention to provide a process for the production of guanyl-thiourea which avoids tbe described disadvantages and permits the production of guanylthiourea in good yield and with high purity.
m~us, according to the present invention, there is provided a process for the production of ~uanyl-thiourea by the reaction of dicyand~mide with hydrcgen sulphide in M-alkylpyrrolidone as solvent in the presence of catalytically-actin~ additives, wherein, as ca~alytically-acting addi~ive, there is used an amine, ammonia and/or elementary sulphur with the L ormation of an addition compound of L,uanylthiourea and N-alkylpyrrolidone which is decomposed by treatment 1Jith an or~anic solvent followed by recovery of the guanylt;~iourea as residue.
As dicyandiamide, there can be used the tec~nical product which is commercially available with a purity of grea~er than 9~.5,~ he hydrogen sulphide can be used in pure form, mixed ~Jith inert gas or as a mixture of hydrogen sulphide and carbon dioxide which is obtained tec~nically. ~he ratio of hydrogen sulphide to carbon dioxide can thereby vary in the ran~e of from 70:3C to 30:70~
An il-alkylpyrrolidone serves as reaction medium for the reaction of the dicyandiamide with the hydrogen sulphide. i~-meth~l-pyrrolidone is preferred but other I~T-alkylpyrrolidones, for example l~-ethylpyrrolidone and monomeric M-vinylpyrrolidone, can also be used with good success. ~he ~i-alkylpyrrolidone can be used as sole reaction medium or also in admixture with other solvents, In particular, the addition of toluene or xylene has proved to be useful, in which case it is preferable to use ~ weight ratio of N-alkylpyrrolidone to toluene and/or xylene of 1:1 to 1:1.50 20~2919 Accordin-, to t;-le inven~ion, it is i~portant to add to the reaction rnixture the additives favourir~
the reaction oetween dicyandiamide and hydrogen sulphide.
~or tnis purpose, primary, secondary and tertiary amines, for example ~ethylamine, diethylamine or tributylamine, nave proved to be useful. The addition of ammonia has proved to be especially useful, preferabl~l in an amount of C.2 to 1.55, by weight and especially preferably of 0.2 to 0.6~ by weight, referred to the amount of dicyan-diamide used. Furthermore, it has been surprisingly ascertained that, besides ammonia ~s catalyst, also the addition of elementary sulphu~ , preferably in an amount of C.5 to 3.Cc by weight, referred to the dicyan-diamide used, quite substantially influences the -;7eed of the reaction and substantially suppres~es the fcr~-ation of undesired by-products.
~ inally, we have found that recycled, impure mother Liquor exerts an ~pecially strong catalytic influence on the reaction, as is shown in the experimental series No. 3 described ~.ereinafter. Over the course of ten batches, practically quantitative yields were obtained, the purity of the Juanylthiourea oein~-; over 980 in all cases. T~us, thQ process according to the present invention is outstandinsly suitable for continuous operation since ~ardly any by-products are for~ed which have to be eli~inatedO

20~29~9 ''~e reaction temperature is preferably of f om 7C to 120v, a 'e~perature of about 50C more prefer-ably being maintained) favourable reaction speeds 'hereby bein~ obtained in the case of app-opriate de~,rrees of reaction. Under optimum conditions, the period of reaction is from 3 to 4.5 hours. Longer reaction times of up to lO hours can be necessary -J~en, for example, displacements in the catalyst system favourinG the reaction occur.
~ he addition product of ,~,-alkylpyrrolidone and guanylthiourea first o'~tained as inter~ediate product can be obtained from the reaction medium in crystalline form by coolin~. It can then be subsequently washed with a small amount of the same solvent combination as was used for the production. Subsequently, the complex is treated with an anhydrous, hot extraction agent in which case, surprisingly, only t~e ;~'-alkyl-pyrroLidone goes into solution, the ~uanylthiourea remainin~ behind as a practically colourless cryst-zlline product.
T0luene has proved to be useful as extraction agent. Ho~ever, there can also be used mixtures of toluene wit~ one OL more other arene derivatives, for example xylene, anisole, chlorobenzine or toluene, and/or esters, for example carbonic acid dialkgl esters, and ketones, for example diethyl ketone or methyl isobutyl ketone.

~, ~ he rl~ixin, ratio of to'uene to the other solvent components can ~e ~aried ~ithin ~lide limits and can be, or example, from 100:0 to 50:50.
7uanyltniourea can be used as an intermediate for ;he production of triazines, optical bLiuhtenin~ agents and plant protection agents, as well as as a component in fertilisers.
~ ne ~ollo~Jing ~xamples are given for the purpose of illustrating the present invention:
Example 1.
Into a stirrer vessel eguipped 1ith a stirrer, a thermometer, a cooler and a gas inlet pipe and con-taining 130 parts by weight of toluene and 99 parts by wei-~ht of l,-methylpyrrolidone ~reintroduced ~4 ?artS by ~Jeight of dicyandia~ide, 0.1 part by weight of tributylamine and 1 part by ~leight of ,uanylthiourea.
After flushin~ the reaction vessel with nitro~en, it ~;w~ heated and, at a temperature of about 7CC, the introduction of hydro~en sulphid~wascom~enced. mhe temperature ~las incrsased to 90C and the introduction of hydrogen sulphide continued until the upta~e of the theoretical amount of 34 parts by weig'nt was ended aft-er a~out 10 hours.
~ he addition compound formed Gf ~uanylthiourea/
i7-methylpyrrolidone ~las so~led ~r.ile stirr~ng, filtered off :Jith suction and subsequently washed with some I~-methylpyrrolidone/toluene.

2~52~19 The addition compound was separated by extracting with hot toluene first at 60C and secondly at 85C.
By briefly boiling up the residue twice and again filter-ing off, the guanylthiourea was obtained as a practically colourless product with a purity of more than 98% and with a melting point of 155 to 164~C. The yield was 114 g, corresponding to 96.5% of theory.
_xample 2.
Correspondin;~ ~ D ~xample 1, ~he follo;~in~ batches were carried out ~it~ other catalysts an(1 other solvent ixture:

exp. Ic~talyst , dicyan- solventlreaction I;lei~h Iyield I;o. (parts ' diamide ! (parts time out ('') by ~:/t~ I (parts I by wt.), hrs./ I parts ,., ,~ wt.)' I( 8~ ~ ,~ ~lt.) _ ~

1 0.8 GT-H 'I 84 1 ~47.5 8/90 07.2 90.7 2 0.1 ~3A ', 84 ~ 99 I~.l;P 9/~8 jll2.3~5.5 0.8 ~TH , 1 15C , j ¦toluene 3 0 03 T3A ~ 84 ~27~ p 12/90 ~112.5I,95.2 I I toluene 4 O.G6 TBA 84 5C ~IP 16/35 ,112.8 95.5 G.8 GTH 150 toluene 52 S 3 84 ~oluen~ 4 8/ 114,3¦~6.7 61 3 S , 84 , 13G 4 5~ 114.7',97.1 i '~oluene . ._ j , ~TIJ = ,uanylthiourea ~A = tribu~ylamine ;~IlP = ;I_methylpyrrolidone S = sulphur 20~2919 'he above _xamples show ~he clear acceleration of the reaction by rneans of ~he use of a~monia and/or sulphur as catalyst s~stem in t'ne case o~ the p~oduction of ~uanylthiou~ea.
ln each case, the addition compound was separa~ed off ~ extraction ~Jith toluene. Analogous results ;lere obtained with mixtures of toluene ~Jith various butanol derivatives, ketones and esters, for example carbonic acid esters, in a ratio of toluene to the other solvent com~onent of 1:1.
~xample 3.
In this series of 10 experiments, there is described the influence of the recycled mot~er liquor on the formation of guan~lthiourea.
~ serial experi~ent ~as carried out ~lith 8 ~atches with the reuse of the mother liquor at 90C. Th2 startin~ reaction mixture (experiment 1) contalned 84 parts by wei~ht of dicyandiamide, 150 parts by ~ei~ht of toluene, 99 parts by l:/eight of I,-met~yl-pyrrolidone (NllPJ and 0.1c,~ of tributylamine and 0.80,~
of guanylthiourea referred to dicyandiamide.
~ or experiments 2 to 8, to f esh dicyandiamide was added the amount of toluene ~iven in the follo~qing Table (in each case 150 parts by lJeight), together ;Jith the pa~ticular given amount of mother liquor from the preceding experiment (= residue of the reaction medium after distilling off the toluene and separation of the product), whereby, in addition, ~.5 g of fresh c 2~52919 ;il ~? wer~ nded in each experiment.

, I ca~al~st, reaction mother H2S ,reactionlwPi-n yieid , :o. (parts I medium liquor I ta~e- ' ti~e ! OUt ' ,, by wt.) I (parts (parts ~, up I (hrs.)l(~arts by wt.) by wt.) ( parts ) vy ;Jt~

1 I ~y .r ~ ~ , ~0 I Ll llC~.9 ~ ~2.2 toluene ¦ 2 _ 150 93.3 ~ 35.5 ¦ 4.3 jllb.~ ¦ 98.6 ! 3 ~ 15~ 94 1 33-4 ! ~-5 ~117-7 1 95.6 ¦ 4 _ 150 lG0 ~ 34.5 1 3.5 ill6.8 ' 98.~ j 1 5 _ 150 lG2 11 32.4 l, 4.4 ~ .2 ~00.0 , o ¦ _ 15C lG9 1 33.5 3.& , 117 99.o 7 ¦ - 15G 112 1 ~2.2 , 3.7 l~117.7 99.6 ~ 15~ 112 ' 34,7 4.6 '117.9 99.8 -methylpyrrolidone In t'ne case of ex~eriments 6 to ~, hydrogen sulphide was used in ad~ixture with 40 parts by volume of carbon dioxide.
Example 4.
Correspondin~ to Exa~ple 3, a series of experi-ments was carried out with ammonia as catalyst and with the reuse of the mother liguor. ~he startin-~reaction ~ixture was as in Example ~ e~cept that 1.2 parts by l~ei~ht of am~onia was used as c3tal,~s~.
In batch 2, to the mother liquor were addition311~
added 2,0 parts by weir,llt of ammonia and 0.5 parts by weight of fresh ~iiP. In batch ~ were addition311 added 2.2 p3rts by weir,ht of a~monia an~ 0.5 pa~ts by wei~hl~ of fresh l~ilP.

2~52919 -L0_ ~ 'he reaction temperature was 90C. ~he hydro~en sulphide was introduced in the form of a mixture ~7ith 50,~ by volume of carbon dioxide.
_, exp. cataLyst reaction mother ¦ -~2S ¦reaction ~Jeigh Yield ;,o. (parts medium liquor time out bg wt.j (parts (parts j take- ¦ (hrs ) (parts ~y wt.) by wt.)¦ (parts ~y ~Jto) . , , , 1 1.~ 995~ollP ~ 31.51 12.2 110.9 93.8 ~oluene 2 2.0 150 89.8 33.6 7.5 118.1 99.9 3 2.2 150 95.1 1I n.d.~.3 118.0 99.9 1 minor amounts result from the volatiLity of the toluene n.d. = not determined

Claims (9)

1. Process for the production of guanylthiourea by the reaction of dicyandiamide with hydrogen sulphide in N-alkylpyrrolidone as solvent in the presence of catalytically-actingr additives, wherein, as catalyric-ally-acting additive there is used an amine, ammonia and/or elementary sulphur with the formation of an addition compound of guanylthiourea and N-alkyl-pyrrolidone which is decomposed by treatment with an organic solvent followed by recovery of guanylthiourea as residue.

2. Process according to claim 1, wherein, as reaction medium, there is used a mixture of N-methylpyrrolidone and toluens with a content of ammonia and elementary sulphur.

3. Process according to claim 2, wherein the content of ammonia is 0.2 to 1.50% by weight and that of sulphur is 0.5 to 3.0% by weight, referred to the amount of dicyandiamide used.

4. Process according to any of the preceding claims, wherein the hydrogen sulphide is used in admixture with carbon dioxide in a volume ratio of 70:30 to 30:70.

5. Process according to any of the preceding claims, wherein the mother liquor is recycled.

6. Process according to any of the preceding claims, wherein the addition product of guanylthiourea and N-methylpyrrolidone is decomposed with toluene.

7. Process according to claim 6, wherein toluene is used an admixture with at least one other arene, ester or ketone derivative in a mixing ratio of from 100:0 to 50:50.

8. Process according to claim 1 for the production of guanylthiourea, substantially as hereinbefore described and exemplified.

9. Guanylthiourea, whenever produced by the process according to any of claims 1 to 8.