Oxidative chlorination of ethylbenzene and isopropylbenzene

1~4

M.S. SAZ,U~HOVet al.

10. G. M. GAL'PERN, V. A. IL'INA, P. M. SHUMSKAYA and V. N. ALEgSANDROV, Khlmlya i tekhnol, monomerov. Tr. Vses, n.-i. i proektn, in-t. monomerov 2, 129, 1970 11. A. M. IVANOV, L. N. KHAKALO and K. A. ~CHEItVINSKII, Neftel~hlmiya 8, 589, 1968 12. Ye. M. TOCHINA, L. M. POSTNIKOV and V. Ya. SHLYAPINTOKH, Izv. AN SSSR, Ser. khlm. 71, 1968

OXIDATIVE CHLORINATION OF ETHYLBENZENE AND ISOPROPYLBENZENE* M. S. SAT,A~I~[OV,~V~.~¢~.GUSS]~I~OV,CH. A. CH~,A~IEV and D. K. ABD~LAYEV Stungait Branch of the Institute of Petrochemical Processes Azerb. S.S.R. Academy of Sciences (Received 16 July, 1974)

C ~ o ~ x ~ . derivatives of ethyl and isopropylbenzene are obtained b y alkyiatiou of chlorobenzene in the presence of Friedel-Crafts [1, 2] catalysts b y direct chlorination of ethylbenzene [3-5] and isopropylbenzene [6, 7]. A1Cls, FeCIa, ZnCI~, SnC14 and TiC14 are used as catalysts in chlorination of alkylbenzenes. However, secondary reactions [5, 7] are undesirable in the catalytic process of chlorination. Investigations are being carried out in our laboratory in the field of oxidizing chlorination of alkyl-aromatic hydrocarbons [8]. There is no information in the literature about this problem. • This article is concerned with explaining some relations which govern the preparation of chlorine derivatives of ethyl- and isopropy!benzene b y oxidative chlorination (with a mixture o f hydrochloric acid and hydrogen perox i d e ) . ..... Experiments were carried out in a glass flask provided with a mechanical atirrer, d r o p funnel and a thermometer. Reaction temperature was maintained with an accuracy of ± 0 . 5 °. Commercial hydrochloric acid, ethyl- and isopr0pylbenzene (pure) and a 30% aqueous solution of hydrogen peroxide were used: for the investigation. The flask was filled with these in given proportions. Hydrogen peroxide was added to the reaction mass from a drop funnel. ~ The react:ion mixture was analysed a t equal time intervals b y GLC using an LKhM-7A device with a heat conductivity detector (detector current 90 mA). * Neftekhlrnlya 15, No. 4, 601-605, 1975.

chlorination of e~hylbenzene

Oxidative

, 1~

Before chromatographic analysis the samples were washed ¢o neutral reaction a n d dried over calcium chloride. Chromatographic curves were obtained using II~Z-600 brick modified with PEG-4000 at a carrier gas (nitrogen) velocity of 60 ml/min. The length of the column was 3 m, analytical temperature 150°. Under these conditions the separation of products of the reaction mixture is ensured. The peaks were assigned by comparing the retention times of individual compounds and those obtained. Results of chromatographic analysis and IR spectra of products synthesized show that o-, 10-ehloroethyl- and o-, ID-chloro-isopropylbenzenes are formed during the reaction. % • /6

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0

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1

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I

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6

8

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300 r'pm

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400

500

Fze. 1. Effect of the intensity of agitation of the reaction mass on the yield (1-6) and rate (7) of oxych]orination of ethy]benzene. Temperature 20°0, intensity of agitation, rpm: 1--0; 2--100, 3--200; 4--300; 6--400; 6--600.

To find optimum conditions for oxychlorination, the.effects of the intensity of stirring the reaction mass, the concentration of hydrochloric acid, hydrogen peroxide feed rate, t h e molar ratio of reacting substances and temperature on the yield of chlorine derivatives of ethyl- and isopropylbenzene were examined. RESULTS

In the initial stage of the experiment we determined the reaction range. Since initial a~omatic hydrocarbons (and chloroalkylaromatic compounds) do, not dissolve in hydrochloric acid it was assumed that reaction rate might b e a~ected by difl~usion factors. In fact, results of experiments (Fig/ I ) s h o w that the intensity of sirring the reaction mixture has a marked effect on the field of monochloroethylbenzene and the rate of oxyehlorination.::: ThUs, without agitation (curve 1, Fig. 1) t h e m a x i m u m yield Of ehloroethylbenzene

'!156

M.S.

SAT.A~OV ~ a/.

does not exceed 18%, while an increase in the intensity of agitation to 400 rev/min (curve 5) increases yield to 91°/o. A further increase of agitation intensity to 600 rev/min has no effect on the yield of chlo~oethylbenzene. To obtain comparable results by a di~erential method, initial reaction rates were calculated at dii~erent intensities of agitation. A marked increase in reaction rate in the interval of 200-400 rev/min (Fig. 1, curve 7), apparently, points to a transition of the reaction from the diffusion (<200 rev/mi'n) into the kinetic range (>400 rev/min). Oxychlorination of aromatic hydrocarbons consists of two step-by-step reactions: interaction of hydrogen peroxide with hydl'ogen chloride takes place in the first stage to form chlorine 2HCI~-H20= -+ CI~-2tt20,

(1)

in the second stage of the process the chlorine separated reacts with hydroca2o bon by the system

(2)

CI,+ ~ - R - - ~ - R + H C I C1

Consequently, the yield and rate of chlorine formation depend on the concentration of hydrochloric acid.

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F I o . 2. Effect of t h e concentration of hydroohloric acid on the yield of ehloroethyl. benzene. Temperature 20°C, intensity of agitation 400 rev/rnln~ (~0]~jCt]~l : H t O a ~ 1 : 1. Concentration o f hydrochloric acid, % wt.: 1--12; 2--10; 3--20; 4--20; 5--30. FIG. 3. Effect of t h e feed rate of hydrogen peroxide on the yield of ohloroethylbenzene. C+H,C~H, : HCI : H = O , ~ 1 : 6 : 1; feed r~te: 1 - - simultaueotm Rllln~; 2--30; 3--15; 4 - - 1 0

g/hr.

157,

Oxidative chlorination of ethylbenzene

Results of Fig. 2 indicate t h a t the yield of ehloroethylbenzene and t h e rate of its formation depend on the concentration of hydrochloric acid and the reaction does not take place in practice if acid concentration is lower t h a n 12~o. An increase in He1 concentration to 36% increases the yield of chloroethylbenzene to 91% in 2 hr. Oxidative chlorination of aromatic hydrocarbons depends both on reaction (1) and reaction (2). I f the rate of reaction (2) is equal to, or considerably higher than, the rate of reaction (1) the separation of free chlorine m a y be excluded. I t was established t h a t without aromatic compounds reaction (1) takes place at a high rate and it m a y be adjusted b y the rate of hydrogen peroxide supply. Consequently, it was essential to select conditions under which the chlorine separated in the first stage fully reacted with aromatic hydrocarbons. Results in Fig. 3 indicate t h a t a feed rate of hydrogen peroxide of 10 g/hr is optimum; at this rate a 98-99~/o yield of chloroethylbenzene is ensured in terms of t h e hydrogen peroxide taken. The Figure shows that with the simultaneous supply of all reacting substances the rate of oxidative chlorination is higher t h a n with the gradual feed of Hz0~, b u t the yield of chlorine derivatives is only 790/0, i.e. part of chlorine is not used up in the reaction. T A B L E 1. E F F E C T OF ~:J~JS A M O U N T OF H Y D R O G E N C H L O R I D E ON T~lJ~ ~2"J[ELD OF CHLORO"~.~t"Y'L- A N D CHLOROISOPROP~irLBENZ]ENE8

Temperature 20°C; molar ratio of alkylbenzene : H,O~----1 : 1 HC1, mole 1 2 4 6 8 10

C,HsC,H,C1 overall I o-I p28 57 85 91 91 91

17 35 52 55 i 55 56

11 22 33 36 36 35

Yield, % CsH~C6H,C1 C~IIC,HsC1, °veraU I °" I P" 0 2 4 7 7.5 8

23 51 7O 80 81 82

11 112 25 26 34.5 35.5 39.5 40.5 40 i 41 40"5 I 41.5

CsH,CeH,CI~

2.5 5 8 11 11

The effect of the amount of hydrochloric acid in the initial mixture on the yield of chloroalkylbenzenes is shown in Table 1. Investigations were carried out at an intensity of agitation of the reaction mixture of 400-450 rev/min and a rate of hydrogen peroxide feed of 10 g/hr. An increase in t h e molar concentration of hydrochloric acid from 1 to 6 moles pet mole hydrogen peroxide increases the yields of monochloroethylbenzene and monochlorois0propylbenzene from 28 to 91% and from 23 to 80%, respectively. The relatively low yield of monochloro-isopropylbenzene, particularly o-isomers is probably due to the sterie effect of the isopropyl radical (Tables 1 and 2). A further increase in the content of hydrochloric acid increases tho

1~. S. SAT.Alg'Frovet a~=

158

formation of dicMoroderivatives of aromatic compounds, the yields of which v a r y between 8 and 11 ~ . A study of the effect of temperature on the yields of chloroaromatic hydrocarbons in the temperature range of 0-40 ° at a rate of hydrogen peroxide feed of 10 g/hr (Fig. 4a, b) indicates that an increase in temperature accelerates oxychlorination of ethyl- and isopropylbenzenes. The time to achieve a maxim u m yield of the intermediate product at 40 ° decreases from 9 to 3 hr, this yield, however, is lower than at 0 °. This dependence of the yield of ehloroethylbenzene on temperature is due to the. acceleration of subsequent chlorination of t h e chloroethylbenzene formed to dichloroethylbenzenes. In fact, it follows from curves 2'-5' (Fig. 4a) that with an increase of temperature from 10 to 40 °, diehloroethylbenzene yield varies between 4 and 18~o and at 0 ° the latter is not formed at all. Consequently, to achieve selective oxychlorination, the process should be carried out at low temperature (20 ° and lower) or at high temperatures with a duration of up to 3 hr. a/a /

100

a

1

3

3

5

b

7

8

r,hr

I

8

5

7

FIG. 4. Dependence of the yields of chloroaromatic hydrocarbons on reaction t i m e : a - - chloroethyl (1-5) and dichloroethylbenzene (2'-5"); b -- chloroisopropyl (1-4) and dichloroisopropyl benzene (1'-4'). Molar ratio of C6HsAI • HC1 : H=O----1 : 6 : 1; tempera° ture, °C: 1--0; 2, 2'--10; 3, 3'--20; 4, 4'--30; 5, 5'--40. Similar results were obtained for oxychlorination of isopropylbenzene (Fig. 4b). In this case with an increase of temperature the yield of monochloroisopropylbenzene decreases and the content of dichloroisopropylbenzene increases. Results in Fig. 4 indicate that the formation of dichloroderivatives of ethyl- and isopropylbenzenes begins after a 4 5 ~ conversion of initial alkylaromatic compounds. Therefore, in order to increase process selectivity, a s t u d y was made of the effect of molar quantitites of ethyl- and isopropylbenzenes in the reaction mixture (Table 2).

Oxidative chlorination of ethylbenzene

159

I t was f o u n d t h a t w i t h a n e q u i m o l e c u l a r r a t i o of a r o m a t i c h y d r o c a r b o n s a n d h y d r o g e n p e r o x i d e u p to 7-8~/o d i c h l o r o d e r i v a t i v e s are f o r m e d . T~BLE 2. EFFECT OF ~ ' ~ M O ~ •£ ' ~

YIELD

OF

PROPORTION OF ETJ~t~Jb-ANDISOPROPYI,BEN~ENES ON MONO-

AND

DICH~LOROA_I.~YI,BENZENES

Temperature 20°C hydroperoxide feed rate 10 g/hr; molar ratio of H C I : H I O s =6:1 CIHsC,H~C1 Alkylbenzene, overall opmole 1 2 4 6 8 10

91

55

36

93 95 96 96 97

57 58 58 58 59

37 37 38 38 38

CaHTCeH,C1 I C,H6C,HaC1.

overall

o-

p-

80 94 95 96 97 97

39.5 46-5 47 47.5 48 48

40"5 47"5 48 48"5 49 49

CsHTC,HaCII

On increasing t h e m o l a r r a t i o o f a l k y l b e n e z e n e : h y d r o g e n p e r o x i d e t o 10 : 1, t h e c o n t e n t s o f d i c h l o r o - d e r i v a t i v e s decreases to 1.0~/o a n d t h e yield o f m o n o c h l o r o - a l k y l b e n z e n e s increases to 97.0%. SUMMARY

l. A s t u d y was m a d e of o x y c h l o r i n a t i o n of e t h y l - a n d i s o p r o p y l b e n z e n e w i t h a m i x t u r e of h y d r o g e n p e r o x i d e a n d h y d r o c h l o r i c acid. I t was s h o w n t h a t w i t h v i g o r o u s s t i r r i n g (over 400 r e v / m i n ) t h e r e a c t i o n t a k e s p l a c e in t h o k i n e t i c range. 2. On using 36~/o h y d r o c h l o r i c acid a n d a m o l a r r a t i o o f A r : HCI : H 2 0 a of 1:1:1, yields o f c h l o r e t h y l - a n d c h l o r i s o p r o p y l b e n z e n e s are 28 a n d 23 a n d w i t h a r a t i o o f 1 : 6 : 1 t h e y increase to 91 a n d 80~/o, r e s p e c t i v e l y . A n increase in t h e c o n c e n t r a t i o n of t h e a r o m a t i c c o m p o u n d to 10 m o l e results in t h e f o r m a t i o n of ortho- a n d para-isomers. REFERENCES

1. 2. 3. 4. 5. 6. 7. 8.

Yu. G. MAMEDALIYEV and Sh. V. VEIAYEV, Dokl. AN SSSR 92, 325, 1953 ~ M. B. TUROVA-POLYAK and M. A. MASLOVA, Zh. obshch, khimii 27, 897, 1957 S. N. USHAKOV and P. A. MATUZOV, Zh. obshch, khimii 14, 120, 1944 Yu. G. MAMEDALIYEV, M. M. GUSEINOV, D. Ye. MISHIYEV, R. S. AT.E~IARDANOV and P. A. PETROSYAN, Azerb. khim. zh. No. 4, 9, 1962 Yu. S. KROPANEV, V. G. PLYUSNIN, N. I. PLOTKINA and L. P. UL'YANOVA, Neftckl~imlya 9, 591, 1969 Yu. G. MAMEDALIYEV, Izbrannyye proizvcdcniya (Selected Works), Izd. AN Azerb. SSR 1, 1964 Yu. S. KROPANEV, V. G. PLYUSNIN and P. I. PLOTKINA, Ncftebhimiya 7, 398, 1967 Auth. Cert. U.S.S.R. 386891, 18. 10. 1972. Otkr. isobr., prom. obr. i toy. znaki, No. 27, 59, 1973