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Alkylation of toluene with propylene on catalysts containing fluorine
ALKYLATION OF TOLUENE WITH PROPYLENE ON CATALYSTS CONTAINING FLUORINE* E. KHABIBULLAYEVA, YE. G. TRESHCHOVA and T. V. ANTIPI~A M. V. Lomonosov State University,Moscow
(Received 8 May 1969)
FLUOI~nVATED alumina and reaction products of AI~Os and concentrated hydrofluoric acid (aluminium hydroxyfluoride)have a high catalytic activity in cracking of cumene and alkylation of benzene with propylene [1]. The study of benzene homologues alkylated with olefins is of practical and teoretical interest. Products of alkylation are valuable raw materials for the production of synthetic materials, synthetic rubber, detergents, etc. The requirements for products of alkylation are becoming more rigid as individual alkylbenzenes have to be separated for further chemical processing. Therefore, when obtaining alkylbenzenes intended for processing in chemical industry secondary processes, if possible, should be excluded. Problems of alkylation of toluene with olefins (propylene) have been insufficiently described in the literature, particularly with heterogeneous catalysts. Vapour-phase alkylation of toluene with propylene has been investigated with HsPO a catalysts on kieselguhr, natural and synthetic aluminosilicates [2-4]. This study deals with alkylation of toluene with propylene using catalysts containing fluorine, which have not been previously used for this process. An industrial Houdry catalyst was used for comparison. The catalytic activity of specimens was determined in a circulating apparatus at atmospheric pressure, with a toluene to propylene molar ratio of 3 : 1 and a space velocity of toluene feed of 0.3 hr -1. Alkylation was carried out by methods previously described [1] using the same catalyst batch. The experiment lasted 60 min.t The catalysed product was analysed every 15 min. Liquid products were analysed in a UKh-1 gas-liquid chromatograph. Column length was 2m, diameter 4ram, fixed phase was Apiezon L - - 1 0 % wt. on chromosorb (grain size 60--80 mesh), column temperature 205 °, carrier gas eomsumption 2.4 dmS/hr. A study was made of the dependence on temperature of product yield from cymene alkylation and the isomeric composition of cymene fraction at 220-300 °. The calculation related * N e f t e k h i m i y a 10, No.I, 34-36, 1970. ¢ Fluorine c o n t e n t did n o t decrease in t h e specimens f r o m one e x p e r i m e n t to another.
2
E. KHABIBUI~AYEVAet a/.
to the products obtained was carried out using chromatograms by the method previously proposed [5]. Cymenes were the only products of alkylation. Not more t h a n 2~/o wt. di-isopropylt~luenes were found in fresh batches of catalysts containing fluorine. Cymene yield and the composition of the cymene fraction, according to temperature, are shown in Figs. 1 and 2. %wl-,
g ~
I
5
$
J
I
220
3 I
l
260
l
300 °C
FIG. l. Dependence of eymene yield on temperature on the catalysts: 1 - - a l u m i n i u m hydroxyfluoride; 2--fluorinated AI=Os; 3 - - H o u d r y catalyst.
With an increase in temperature from 220 to 300 ° cymene yields increase and at 240 ° reach 20% wt., calculated on the toluene taken for the reaction for an aluminium hydroxyfluoride catalyst, containing 56.5% F (Fig. 1, curve 1); 21.0% at 280 ° for fluorinated alumina, containing 6-4% F (Fig. 1, curve 2)
% wt.
b
a
0
! ~.~ N ~ . oO
-
2
8 ~ 20 I
@'~
220
I
3O0
II
I
220
I i,~
300
I
220
l
280 °C
FIG. 2. Composition of the cymene fraction according to experimental temperature. Catalysts: a--aluminium hydroxyfluoride; b--fluorinated Al~O3; c--Houdry catalyst. 1--m-Cymene; 2--p-cymene; 3--o-cymene.
and 1 8 o wt. at 260 ° for a Houdry catalyst (Fig. 1, curve 3). At these temperatures optimium cymene yield was observed. Further increase in temperature markedly reduces cymene content in the catalysed product (Fig. 1) for all three
Alkylation of toluene with propylene
3
catalysts. On changing reaction temperature the composition of the cymene fraction also alters. Formation ofp-cymene passes through a maximum on all the three samples (Fig. 2). During alkylation on aluminium hydroxyfluorideand fluorinated alumina (Fig.2a,b, curve 1) m-cymene content increases and o~cymenecontent decreases (Fig. 2a, b, curve 3) with the increase of temperature. On a Houdry catalyst the formation of m-cymene passes through a minimum with increase in temperature and the formation of o-cymene through a maximum (Fig. 2c, curves 1 and 3, respectively). However, the authors of a previous paper [3] did not find any change in the composition of the cymene fraction at temperatures of 200-300 °. It may be assumed that the isomeric composition of cymenes during alkylation depends on cymene isomerization and on the number of active centres, which decrease as a result of coke formation, as noted by the authors of another paper [4]. It is well known that, if the benzene nucleus contains a substituent the position in which a second substituent group enters the nucleus is determined by the nature of the first substituent. The alkyl radical, CHa, belongs to that type of substituent, which only direct the substituent to the ortho- and parapositions. An isomer mixture is formed in this case, in which one isomer predominates. Meta-isomer either is not formed at all or in a negligible quantity. However, alkylation of toluene by propylene does not conform to the rule of orientation of electrophilic substitution. During alkylation on catalysts containing fluorine para- and meta-cymenes are mainly formed. It is obvious that owing to steric hindrance, the strongly branched radical cannot be oriented on the ortho-position. In addition to using the chromatographic method of analysis for determining cymene content and composition, alkylation produc~s were analysed using Raman spectra. The catalysate taken after the experiment, which lasted for 60 rain, was distilled in vacuum. The spectrum was recorded in an ISP-51 spectrograph by conventional methods. In the spectra obtained the frequencies and intensities of lines of components were calculated and the composition of the fraction determined (%). The following spectrum lines were used for analysis: 788 cm -1 to determine toluene; 803 cm- 1 for p-cymene; 711 cm- 1 for m-cymene and 716 cm- 1for o-cymene. Di-isopropyltoluenes were not detected by Raman spectra. A comparison of results with information in the literature [2-4] suggests that catalysts containing fluorine are effective in alkylation of toluene with propylene. SUMMARY
1. Fluorinated alumina and aluminium hydroxyfluorides are highly active selective catalysts in alkylation of toluene with propylene. 2. The isomeric composition of the cymene fraction depends on experimental temperature. On increasing temperature, m-cymene content increases, o-cymene content decreases and p-cymene formation passes through the maximum.
4
E. K H A B r s u L ~ Y E V A
et c~.
REFERENCES 1. E. KHABIBUIJJAYEVA a n d T. V. ANTIPINA, Neftekhimiya 9, No. 3, 368, 1969 2. V. G. TELEGIN a n d V. A. SIDOROV, Khim. prom.-st', No. 11, 65, 1961 3. Yu. G. MAMEDALIEV, T. A. ZEINALOVA and M. A. MIRZOYEVA, Selected papers b y Yu. G. Mamedaliev, Izd. AN SSSR, Moscow, 1964 4. G. M. PENCHENKOV, I. M. KOLESNIKOV a n d Ye. A. MOR0ZOV, K i n e t i k a i kataliz (Kinetics a n d Catalysis). 69, Izd. Mosk. in-ta neftekhim, i gazovoi prom-sti (Published b y the Moscow I n s t i t u t e of Petrochemical and Gas Industry). Moscow, 1967 5. A. A. ZHEgHOVITSI(II~ O. D. STERLIGOV a n d N. M. TURKEL'TAUB, Dokl. A N SSSR 123, 1037, 1958
(Received 8 May 1969)
FLUOI~nVATED alumina and reaction products of AI~Os and concentrated hydrofluoric acid (aluminium hydroxyfluoride)have a high catalytic activity in cracking of cumene and alkylation of benzene with propylene [1]. The study of benzene homologues alkylated with olefins is of practical and teoretical interest. Products of alkylation are valuable raw materials for the production of synthetic materials, synthetic rubber, detergents, etc. The requirements for products of alkylation are becoming more rigid as individual alkylbenzenes have to be separated for further chemical processing. Therefore, when obtaining alkylbenzenes intended for processing in chemical industry secondary processes, if possible, should be excluded. Problems of alkylation of toluene with olefins (propylene) have been insufficiently described in the literature, particularly with heterogeneous catalysts. Vapour-phase alkylation of toluene with propylene has been investigated with HsPO a catalysts on kieselguhr, natural and synthetic aluminosilicates [2-4]. This study deals with alkylation of toluene with propylene using catalysts containing fluorine, which have not been previously used for this process. An industrial Houdry catalyst was used for comparison. The catalytic activity of specimens was determined in a circulating apparatus at atmospheric pressure, with a toluene to propylene molar ratio of 3 : 1 and a space velocity of toluene feed of 0.3 hr -1. Alkylation was carried out by methods previously described [1] using the same catalyst batch. The experiment lasted 60 min.t The catalysed product was analysed every 15 min. Liquid products were analysed in a UKh-1 gas-liquid chromatograph. Column length was 2m, diameter 4ram, fixed phase was Apiezon L - - 1 0 % wt. on chromosorb (grain size 60--80 mesh), column temperature 205 °, carrier gas eomsumption 2.4 dmS/hr. A study was made of the dependence on temperature of product yield from cymene alkylation and the isomeric composition of cymene fraction at 220-300 °. The calculation related * N e f t e k h i m i y a 10, No.I, 34-36, 1970. ¢ Fluorine c o n t e n t did n o t decrease in t h e specimens f r o m one e x p e r i m e n t to another.
2
E. KHABIBUI~AYEVAet a/.
to the products obtained was carried out using chromatograms by the method previously proposed [5]. Cymenes were the only products of alkylation. Not more t h a n 2~/o wt. di-isopropylt~luenes were found in fresh batches of catalysts containing fluorine. Cymene yield and the composition of the cymene fraction, according to temperature, are shown in Figs. 1 and 2. %wl-,
g ~
I
5
$
J
I
220
3 I
l
260
l
300 °C
FIG. l. Dependence of eymene yield on temperature on the catalysts: 1 - - a l u m i n i u m hydroxyfluoride; 2--fluorinated AI=Os; 3 - - H o u d r y catalyst.
With an increase in temperature from 220 to 300 ° cymene yields increase and at 240 ° reach 20% wt., calculated on the toluene taken for the reaction for an aluminium hydroxyfluoride catalyst, containing 56.5% F (Fig. 1, curve 1); 21.0% at 280 ° for fluorinated alumina, containing 6-4% F (Fig. 1, curve 2)
% wt.
b
a
0
! ~.~ N ~ . oO
-
2
8 ~ 20 I
@'~
220
I
3O0
II
I
220
I i,~
300
I
220
l
280 °C
FIG. 2. Composition of the cymene fraction according to experimental temperature. Catalysts: a--aluminium hydroxyfluoride; b--fluorinated Al~O3; c--Houdry catalyst. 1--m-Cymene; 2--p-cymene; 3--o-cymene.
and 1 8 o wt. at 260 ° for a Houdry catalyst (Fig. 1, curve 3). At these temperatures optimium cymene yield was observed. Further increase in temperature markedly reduces cymene content in the catalysed product (Fig. 1) for all three
Alkylation of toluene with propylene
3
catalysts. On changing reaction temperature the composition of the cymene fraction also alters. Formation ofp-cymene passes through a maximum on all the three samples (Fig. 2). During alkylation on aluminium hydroxyfluorideand fluorinated alumina (Fig.2a,b, curve 1) m-cymene content increases and o~cymenecontent decreases (Fig. 2a, b, curve 3) with the increase of temperature. On a Houdry catalyst the formation of m-cymene passes through a minimum with increase in temperature and the formation of o-cymene through a maximum (Fig. 2c, curves 1 and 3, respectively). However, the authors of a previous paper [3] did not find any change in the composition of the cymene fraction at temperatures of 200-300 °. It may be assumed that the isomeric composition of cymenes during alkylation depends on cymene isomerization and on the number of active centres, which decrease as a result of coke formation, as noted by the authors of another paper [4]. It is well known that, if the benzene nucleus contains a substituent the position in which a second substituent group enters the nucleus is determined by the nature of the first substituent. The alkyl radical, CHa, belongs to that type of substituent, which only direct the substituent to the ortho- and parapositions. An isomer mixture is formed in this case, in which one isomer predominates. Meta-isomer either is not formed at all or in a negligible quantity. However, alkylation of toluene by propylene does not conform to the rule of orientation of electrophilic substitution. During alkylation on catalysts containing fluorine para- and meta-cymenes are mainly formed. It is obvious that owing to steric hindrance, the strongly branched radical cannot be oriented on the ortho-position. In addition to using the chromatographic method of analysis for determining cymene content and composition, alkylation produc~s were analysed using Raman spectra. The catalysate taken after the experiment, which lasted for 60 rain, was distilled in vacuum. The spectrum was recorded in an ISP-51 spectrograph by conventional methods. In the spectra obtained the frequencies and intensities of lines of components were calculated and the composition of the fraction determined (%). The following spectrum lines were used for analysis: 788 cm -1 to determine toluene; 803 cm- 1 for p-cymene; 711 cm- 1 for m-cymene and 716 cm- 1for o-cymene. Di-isopropyltoluenes were not detected by Raman spectra. A comparison of results with information in the literature [2-4] suggests that catalysts containing fluorine are effective in alkylation of toluene with propylene. SUMMARY
1. Fluorinated alumina and aluminium hydroxyfluorides are highly active selective catalysts in alkylation of toluene with propylene. 2. The isomeric composition of the cymene fraction depends on experimental temperature. On increasing temperature, m-cymene content increases, o-cymene content decreases and p-cymene formation passes through the maximum.
4
E. K H A B r s u L ~ Y E V A
et c~.
REFERENCES 1. E. KHABIBUIJJAYEVA a n d T. V. ANTIPINA, Neftekhimiya 9, No. 3, 368, 1969 2. V. G. TELEGIN a n d V. A. SIDOROV, Khim. prom.-st', No. 11, 65, 1961 3. Yu. G. MAMEDALIEV, T. A. ZEINALOVA and M. A. MIRZOYEVA, Selected papers b y Yu. G. Mamedaliev, Izd. AN SSSR, Moscow, 1964 4. G. M. PENCHENKOV, I. M. KOLESNIKOV a n d Ye. A. MOR0ZOV, K i n e t i k a i kataliz (Kinetics a n d Catalysis). 69, Izd. Mosk. in-ta neftekhim, i gazovoi prom-sti (Published b y the Moscow I n s t i t u t e of Petrochemical and Gas Industry). Moscow, 1967 5. A. A. ZHEgHOVITSI(II~ O. D. STERLIGOV a n d N. M. TURKEL'TAUB, Dokl. A N SSSR 123, 1037, 1958