- Email: [email protected]
Oxidation of cyclohexene in the presence of an iminodiacetate vanadyl complex chemically fixed on silica and alumina
lih~lrol. Chem. U.S.S.R. Vol. 28. No. 4, pp. 235-241, 19118 Printed in Poland
0031--6458/88 $10.00+.00 ~ 1990 Pergamon P r e u plc
OXIDATION OF CYCLOHEXENE IN THE PRESENCE OF AN IMINODIACETATE VANADYL COMPLEX CHEMICALLY FIXED ON SILICA AND ALUMINA* V. V. BERENTSVEIG, T. V. BARINOVA and B. V. ROZENTULLER M. V. Lomonosov Moscow State University (Receded25 January 1988)
As SHOWNearlier [l],catalysts based on iminodiacetate transition metal complexes chemically fixed on silica are effective activators of the liquid-phase oxidation of cyclohexene by molecular oxygen. In this case, a radical-chain heterogeneoushomogeneous mechanism is realized in the system with the participation of a heterogeneous catalyst at least at the stages of initiation and linear breakage of chains. In the present paper an investigation was made of features of liquid-phase oxidation of cyclohexene in the presence of an iminodiacetate vanadyl complex chemically fixed either on silica or on alumina. Known published data on the specific nature of the catalytic properties of vanadyl indicate the possible occurrence in its presence not only of oxidation, but also of hydroperoxide epoxidation of cyclohexene [2], i.e. combined oxidation and epoxidation of the initial olefin in the system. The use of silica or alumina as the support made it possible on the other hand to assess the influence of the nature of the supports on the specific properties of heterogeneous catalysts based on chemically fixed metal complexes.
EXPERIMENTAL,DISCUSSION OF RESULTS Silica and alumina were modified with iminodiacetate by the procedure described in detail in [3]. This can be represented by the following scheme:
OEt ! .) 5\ S i _ 0 .Si(CtI.,)a_NH. -
,.\l=,)a,Sit_,. ~-(Et~5)aSi(Cll~)aNll._.,x ( /\ A I _ O o
O I".t
CICI ta --(;
OH
\ OH.. ~. /\.,1_0 /
",\__ ' ] Si--O--Si-(CH.)a--N(CIIzCOONa)2. T HCI; .,/ i t.)tl \
..... -~ ClaSi(CtI~)aBr --5 2. ~..\ .,O,)<~t~.
(5
\\
I
AI--(.)--] --~Si--O---Si--(Cll~)a-- Br
,'Icl
•
/ /
* Neftekhimiya 28, No. 6, 791-796, 1988. 235
236
V . V . BEUN'rSVmO e t a / . o / HN \
CH,--C \ \
ONa 0 \CH,_C ~
() )"
"ONa_>
AI--O--
OH
, _Si_o--si--(CH..,)a--N(CH~:COONa).' : !IY,~.
/
I
OH
Subsequently Olt
q
L --- - - S i - - ( C H 2)3-- N (CH,,C 00-)~.
I
OH Sorption of vanadyl ions using a chemically modified support was carried out from aqueous solutions of vanadyl sulphate of different concentrations at 323°K for 30 rain. After this, the catalysts were washed with distilled water and acetone and dried in air. Certain characteristics of the catalysts obtained are summarized in Table 1. TABLE 1. C H A R A ~ T I C ~ OF CATALYS1~ USED IN P R O S
OF LIQUID-PHASBOXIDATION OF
I-IYDROCARBONS
Catalyst
Temperature of exocffcct,
zlm, V.
Capacity [C]o~, with respect mmole/g to metal,
°K
Silochrome S-80-L AlaO3-L
593 568
S,,, m2/g
a~,,.,,
mmole/g
1.5 2.5
0.089 0.0145
0-0115 0.096
Average pore diameter
102 89
nm
45 4.5
An investigation of the distribution and structure of vanadyl complexes on the surface of oxides by means of EPR spectroscopy showed that real information can be obtained by this method only for a silica-base catalyst. Here the obtained values of the parameters of the EPR spectra ( g l l = 1.993; gx= 1.377, Arl=98) were in satisfactory agreement with parameters of the EPR spectra of homogeneous analogues, which indicates the formation of an oxide of a similar iminodiacetate complex (IDAC) on the surface. Increase in the degree of filling of the surface of modified silica with vanadyl ions led to broadening of the second parallel component, although this effect is due to an increase in dipole-dipole interaction between the paramagnets on account of a reduction in the mean statistical distance between them [4]. It is this that can result in the absence of signals in the EPR spectra of vanadyl complexes chemically fixed on alumina, which is probably characterized by denser (mean statistical distance < Inm) grafting of functional groups. Objectively, differences in the grafting densities of functional groups can probably be attributed on the one hand to the difference in the texture of the supports (as follows from
237
Oxidation of cyclohexene
Table 1, the average pore diameter in alumina is an order of magnitude smaller than in silica), and on the other hand to the average concentration and reactivity of the surface hydroxyl groups by which chemical modification of oxides occurs.
¢i, mole/t.
Gi, mole/I n
b
30-
30-
1"5
//+4 / / /.,," 3 .I ~" ..ry 5
1"0
1
80
10
/ C o ....
~ qO
2"0
6
I
120 7", min
0"5
S, 00
80
120 ~',rnin
Flo. 1. Kinetics of oxygen absorption and yield of oxygen-containing products of cyclohexene oxidation (348 K; me.t=0.05 g; concentration: [RH]o=9-87 mole/1., [ROOH]o=0.01 mole/l.) in presence of catalytic systems: a - AlaO3-L-V; b - SiOa-L-V; 1 - oxygen: 2 - hydroperoxide; 3 - cyclohexenol; 4 - cyclohexenone; 5 - cyclohexane oxide; 6 - cyclohexanol oxide. Points indicate experimental data; curves indicate data calculated by model. The procedure for investigating the kinetics of liquid-phase oxidation of cyclohexene and analysis of the products were described earlier in [I]. Figure 1 presents kinetic curves characterizing the combined process in the presence of an iminodiacetate vanadyl complex chemically fixed on silica or alumina. From these data it can be seen firstly that the composition of the products is identical for both catalysts, and secondly that somewhat unexpectedly there is no great difference in their activity despite the considerable difference in the amount of vanadyl fixed on each of the oxides. This effect cannot be attributed to "peaking" of the effectiveness of the catalyst as the surface o f iminodiacetate-modified oxides is filled with vanadyl ions. As shown by experiments, in this case the amount of oxygen absorbed within 2 hr of the combined process with increase in the degree of filling, for example, of modified alumina with vanadyl ions from 20 to 100~o (of its maximum capacity) increases from 0.2 to 4.6 mole/1. Assuming that the nature of distribution of vanadyl complexes on the surface of the oxides is statistical, as assumed, for example, in Kobozev's "active enseble"
V. V. ~ m c r s v e z o
238
et al.
theory [5], it can be sho~,n that the identical activity of the catalysts with different contents of the active phase may be due to the virtually equal concentration of centres of certain nuclearity on the two of them. Corresponding results of numerical calculations for mononuclear centres in the form of isomolar sections are presented in Fig. 2. Here the maximum capacity of the modified sorbent (in mole/g) is plotted
8
#
/13_/ 0.5
,.<>,,i
Y,
l.O Ci " 105, rnolel9
I
:
Fie. 2. Isomolar sections of dependenceof concentration of mononuclearcentres with variation in maximum capacity of sorbent (X-axis) and average number of complexes in fixation zone (F-axis). Concentration of centres along Z-axis equal to C~x 105, mole/g. along the X-axis, the average number of complexes in the fixation zone ~ along the Y-axis, and the concentration of mononuclear centres on each of them along the Z-axis. The points in Fig. 2 indicate two catalyst variants which will have, for example, an identical number of mononuclear centres (5 x l0 -s mole/g) (points 1 and 2), although their maximum capacities differ almost by an order of magnitude. Of course, this will be possible only when the average of complexes in the fixation zone of one is ,,.2, and in that of the other 4. What is more, the concentration of mononuclear centres in the catalyst of greater maximum capacity may not unexpectedly even be considerably lower than in the catalyst of lower maximum capacity (points 3 and 4), which is also due to the different nuclearity of the complex in the fixation zone for the two catalysts. With account taken of textural features of the oxides used, this seems to us to be entirely realistic and probably predetermined their roughly equal catalytic activity with a considerable difference in maximum sorption capacity. Certain differences in the selectivity of the combined process and, in particular, the slightly greater selectivity of an iminodiacetate VO complex chemically fixed on alumina in cyclohexanol epoxide formation may also be due to the specific nature of the structure of the active surface. Mathematical modelling of the kinetics of the combined process in the presence of synthesized catalysts was based on the
239
Oxidation of.cyclohexene
following e x p e r i m e n t a l facts. W i t h o u t h y d r o p e r o x i d e in t h e system, t h e r e a c t i o n d i d not begin at 348°K even over a p e r i o d o f 4 hr. On the o t h e r h a n d , the k i n e t i c o r d e r o f the r e a c t i o n w i t h respect to oxygen was r o u g h l y equal to unity. In the course o f catalysis, a c c o r d i n g to E P R s p e c t r a o f silica-based c a t a l y s t s t h e r e was a c h a n g e in the v a l e n c y state o f t h e v a n a d y i ions in the catalysts. V a n a d i u m c h a n g e d f r o m t e t r a v a l e n t to p e n t a v a l e n t . This led to a c o n s i d e r a b l e c h a n g e in selectivity o f such a d e v e l o p e d c o n t a c t , s u p p o r t e d ' by the d a t a in T a b l e 2. In p a r t i c u l a r , these TABLE 2.
YIELD OF PRODUCTS (MOLE/L) WITH RE-USE OF
SiO,-L-V
CATALYST IN ]PROCE~F..$ OF
OXIDATION AND EPOXIDATION OF CYCLOHEXENE AT 348°K
120rain; [rn,,]=25 g/I.; [Vl= 1.15 x 10 -3 mole/g; [ROOH]o--0'38 mole/l. Catalyst
Absorption of 02 : ROOH
Initial After use in oxidation After use in epoxidation
ROH
Oxidation 0.42 ] 1.08 10"08 : 1"56 0.56 [ 1"14 Epoxidation 0-04 0-16 0.02 0.18
3'2 5"6 3.2
i
R>O
1.30 1.35
1 "06 0'76 0'87
0"'90 0"84
0-09 0.08
0"22 0"24
0"14 0"16
0"12
0.18
0"13
I
Initial After use in epoxidation After use in oxidation
R(O H) > O
R=O
2.73
1"20
I
0.04
I
0'18
* [ R O O H ] o - - . 0 - 4 8 molo/1.
d a t a show t h a t p e n t a v a l e n t v a n a d i u m ions a r e m o r e active in o x i d a t i o n , while t e t r a v a l e n t , v a n a d i u m ions are m o r e active in e p o x i d a t i o n . U n f o r t u n a t e l y , we are n o t able to j u d g e the n u c l e a r i t y o f the active centres in either case on these basis o f the d a t a o b t a i n e d . C o m b i n e d with d a t a on the d e p e n d e n c e o f the r a t e o f t h e r e a c t i o n on the c o n c e n t r a t i o n o f its m a i n c o m p o n e n t s , all this m a d e it possible to p r o p o s e the following scheme for the c o m b i n e d o x i d a t i o n - e p o x i d a t i o n process ( n u m e r i c a l values o f the rate c o n s t a n t s o f individual stages a n d t h e i r d i m e n s i o n s ) : SiO2 O.
[V'*]~+ROOH~[V4+ROOH)~
9. [V 5 + ] , + R O O H - + [ V 5 + R O O H ] , -
= -
AI203
O
--
-
Q'
-
-
1. Q + O,--*[VS +], + R = O + H20~ 2"5x 10 -2 01. Q"--~[V4+]s+RO2+H,O 6"26x10 -3 2. Q'+ROH--+IVS+],+2RO" + H 2 0 30"0 3. Q'+ROOH-'+IVS+]s+RO" +R.O~ + H 2 0 30"1 4. RO" + R H " * R O H + R " 5. R" +Ov-*RO~ 6. RO'~ + RH--*ROOH'+ R" 60x10 -2 7. RO~ + R . H - , R > O +RO" 2.0 x 10 - s 8. RO,~ + R O ~ - - * R = O + R O H + O 2 9. RO.~ + ROOH--+ROOH + R,= O + HO ' 0"67 10. HO~ + RH"-*HaO + R"
2-5 x I0 -2 l./(mole.min) 6"25x10 -3 min- t 18"0 l./(mole.min) I0"0 l./(mole.min) 6.0 x 10 -2 (l./(mole.min))~ 2.0×10 -3 (l./(mole.min))~ 0"64
240
V.V.
BEREt,rrsv~o et al.
11. HO" + R H ~ H 2 0 + R " 12. Q + RH'-*[V4+],+R> O + ROH t3. Q + ROH--*[V* +]. + R(OH) > O + R O H
-
7"5 130.0
-
1"5 20.0
l./(mole.min) I./(mole.min)
Here ROOH is cyclohexenyl hydroperoxide, R H is cyclohexene, ROH is cyclohexanol, R = O is cyclohexenone, R > O is cyclohexane oxide, R[OH] > O is cyclohexanol oxide, [V* +]s [Vs + ]s is heterogenized IDAC of tetra- and pentavalent vanadyl, and Q and Q' are hydroperoxide complexes on the surface of the heterogeneous catalyst with V(V) and V(IV) respectively. Stages I--4 are actually stages of chain initiation with account taken of the autocatalytic nature of the process because of its acceleration by the cyclohexenol (stage 2) and hydroperoxide (stage 3) formed in the system. The inverse kinetic problem with different initial conditions was solved on an SM-4 machine by the procedure described in [6]. The numerical values of the constants found for different stages of the combined process are given above. The best description for both catalysts was obtained on the assumption that the constants of stages 1 and 01 for them are identical, while the constants of stages 2, 3, 12, and 13 (which are actually certain effective parameters since they contain the unknown concentrations of active centres of some specific nuclearity) are different. On this assumption, it is entirely logical that numerical estimates of the constants of stages 5, 6, and 7, which are not associated with the participation of a catalyst, are practically identical for the two catalysts. Description of experimental data within the framework of the given scheme is illustrated in Fig. 1, where calculated kinetic curves are presented by the continuous lines, and experimental kinetic curves by the points. Consequently, iminodiacetate vanadyl complexes chemically fixed on silica or aluminium are fairly effective catalysts of the combined oxidation and epoxidation of cyclohexene. Differences in the properties of the two catalysts obtained can be attributed both to the nature of the oxide support investigated (the difference in the distribution and reactivity of surface OH groups) and to the difference in their texture, which determines the distribution of the active component on the surface of the support. Strictly, the effectiveness of the active centre of catalysis is probably roughly identical for the two cases. This is determined by the specific nature of their structure: according to the catalyst production scheme presented above, the vanadyl complexes are actually 1.0-1.5 nm away from the surface of the support and therefore not very "sensitive" to its nature. SUMMARY
1. In the presence of iminodiacetate vanadyl complexes fixed on silica or alumina, combined liquid-phase oxidation and epoxidation of cyclohexene takes place. 2. The process proceeds by a heterogeneous-homogeneous radical-chain mechanism with autoacceleration on account of the cyclohexenol and cyclohexenyl hydroperoxide accumulated in the system. 3. The texture of the supports used has a greater effect on the distribution of
N-2-pyridyldialkylthioamides as additives to lubricating oils
241
active centres (iminodiacetate vanadyl complexes) on the surface of the catalysts than the nature of the supports. This leads to a certain difference in the activity and selectivity of the catalysts in the combined process. REFERENCES
1. V. V. BERENTSVEIG, CHAN BIK NGA, T. V. BARINOVA and G. V. LISICHKIN, Kinetika i kataliz 25, 5, 1477, 1984 2. S. A. NIZOVA, N. N. BUYANOVA, S. P. LUCHKINA, Ye. P. KRYSIN and L. G. A.NDRONOVA, Neftekhimiya 15, 5, 765, 1975 3. G. V. KUDRYAVTSEV, G. V. LISICHKIN, Yu. A. SAPOZHNIKOV and R. A. KUZNETSOV, Auth. Cert. 850204 (U.S.S.R.). Byull. izobr., 28, 53, 1981 4. S. T. ROSS, J. Chem. Phys. 42, 3919, 1965 5. N. I. KOBOZEV, Izbrannye trudy (Selected Proceedings), Vol. 1, p. 134, MGU, Moscow, 1978 6. S.V. KRIVENKO, L G. SYSHCHIKOVA, A. M. YEVSEYEV and V. V. BERENTSVEIG, Kinetika i kataliz 24, 6, 1299, 1983
Petrol. Chem. U.S.S.R. Vol. 28, No. 4, pp. 241-245, 1988 Printed in Poland
0031-6458/88 Sl0.00+ .00 ~D 1990 ]Pergamon Preu pie
N-2-PYRIDYLDIALKYLTHIOAMIDES AS ADDITIVES TO LUBRICATING OILS* A. B. KULIYEV, T. SH. GASANOVA, N. O. AKHADOV a n d S. A. MAMEDOV Institute of Chemistry of Additives, Azerbaidzhan Academy of Sciences, Baku (Received 30 March 1988) THE results of earlier investigations showed that primary thioamides are effective additives to lubricating oils [1-3]. In order to find more effective additives, in the present study secondary thioamides (N-2-pyridyldialkanethioamides) were synthesized, and their effect on the quality of lubricating oils was investigated. Interest in the given compounds is due to the fact that N-2-pyridyldialkanethioamides contain double the quantity of thiocarbonyl groups (C = S) possessing high activity in relation to metals [4]. N-2-pyridyldialkyhhioamides were synthesized by the interaction of phosphorus pentasuiphide with N-2-pyridyldialkylthiamide [1-3], and the latter were obtained by the reaction of corresponding carboxylic acid. chlorides with 2-aminopyridine * Neftekhimiya 2,8, No. 6, 809-812, 1988.
0031--6458/88 $10.00+.00 ~ 1990 Pergamon P r e u plc
OXIDATION OF CYCLOHEXENE IN THE PRESENCE OF AN IMINODIACETATE VANADYL COMPLEX CHEMICALLY FIXED ON SILICA AND ALUMINA* V. V. BERENTSVEIG, T. V. BARINOVA and B. V. ROZENTULLER M. V. Lomonosov Moscow State University (Receded25 January 1988)
As SHOWNearlier [l],catalysts based on iminodiacetate transition metal complexes chemically fixed on silica are effective activators of the liquid-phase oxidation of cyclohexene by molecular oxygen. In this case, a radical-chain heterogeneoushomogeneous mechanism is realized in the system with the participation of a heterogeneous catalyst at least at the stages of initiation and linear breakage of chains. In the present paper an investigation was made of features of liquid-phase oxidation of cyclohexene in the presence of an iminodiacetate vanadyl complex chemically fixed either on silica or on alumina. Known published data on the specific nature of the catalytic properties of vanadyl indicate the possible occurrence in its presence not only of oxidation, but also of hydroperoxide epoxidation of cyclohexene [2], i.e. combined oxidation and epoxidation of the initial olefin in the system. The use of silica or alumina as the support made it possible on the other hand to assess the influence of the nature of the supports on the specific properties of heterogeneous catalysts based on chemically fixed metal complexes.
EXPERIMENTAL,DISCUSSION OF RESULTS Silica and alumina were modified with iminodiacetate by the procedure described in detail in [3]. This can be represented by the following scheme:
OEt ! .) 5\ S i _ 0 .Si(CtI.,)a_NH. -
,.\l=,)a,Sit_,. ~-(Et~5)aSi(Cll~)aNll._.,x ( /\ A I _ O o
O I".t
CICI ta --(;
OH
\ OH.. ~. /\.,1_0 /
",\__ ' ] Si--O--Si-(CH.)a--N(CIIzCOONa)2. T HCI; .,/ i t.)tl \
..... -~ ClaSi(CtI~)aBr --5 2. ~..\ .,O,)<~t~.
(5
\\
I
AI--(.)--] --~Si--O---Si--(Cll~)a-- Br
,'Icl
•
/ /
* Neftekhimiya 28, No. 6, 791-796, 1988. 235
236
V . V . BEUN'rSVmO e t a / . o / HN \
CH,--C \ \
ONa 0 \CH,_C ~
() )"
"ONa_>
AI--O--
OH
, _Si_o--si--(CH..,)a--N(CH~:COONa).' : !IY,~.
/
I
OH
Subsequently Olt
q
L --- - - S i - - ( C H 2)3-- N (CH,,C 00-)~.
I
OH Sorption of vanadyl ions using a chemically modified support was carried out from aqueous solutions of vanadyl sulphate of different concentrations at 323°K for 30 rain. After this, the catalysts were washed with distilled water and acetone and dried in air. Certain characteristics of the catalysts obtained are summarized in Table 1. TABLE 1. C H A R A ~ T I C ~ OF CATALYS1~ USED IN P R O S
OF LIQUID-PHASBOXIDATION OF
I-IYDROCARBONS
Catalyst
Temperature of exocffcct,
zlm, V.
Capacity [C]o~, with respect mmole/g to metal,
°K
Silochrome S-80-L AlaO3-L
593 568
S,,, m2/g
a~,,.,,
mmole/g
1.5 2.5
0.089 0.0145
0-0115 0.096
Average pore diameter
102 89
nm
45 4.5
An investigation of the distribution and structure of vanadyl complexes on the surface of oxides by means of EPR spectroscopy showed that real information can be obtained by this method only for a silica-base catalyst. Here the obtained values of the parameters of the EPR spectra ( g l l = 1.993; gx= 1.377, Arl=98) were in satisfactory agreement with parameters of the EPR spectra of homogeneous analogues, which indicates the formation of an oxide of a similar iminodiacetate complex (IDAC) on the surface. Increase in the degree of filling of the surface of modified silica with vanadyl ions led to broadening of the second parallel component, although this effect is due to an increase in dipole-dipole interaction between the paramagnets on account of a reduction in the mean statistical distance between them [4]. It is this that can result in the absence of signals in the EPR spectra of vanadyl complexes chemically fixed on alumina, which is probably characterized by denser (mean statistical distance < Inm) grafting of functional groups. Objectively, differences in the grafting densities of functional groups can probably be attributed on the one hand to the difference in the texture of the supports (as follows from
237
Oxidation of cyclohexene
Table 1, the average pore diameter in alumina is an order of magnitude smaller than in silica), and on the other hand to the average concentration and reactivity of the surface hydroxyl groups by which chemical modification of oxides occurs.
¢i, mole/t.
Gi, mole/I n
b
30-
30-
1"5
//+4 / / /.,," 3 .I ~" ..ry 5
1"0
1
80
10
/ C o ....
~ qO
2"0
6
I
120 7", min
0"5
S, 00
80
120 ~',rnin
Flo. 1. Kinetics of oxygen absorption and yield of oxygen-containing products of cyclohexene oxidation (348 K; me.t=0.05 g; concentration: [RH]o=9-87 mole/1., [ROOH]o=0.01 mole/l.) in presence of catalytic systems: a - AlaO3-L-V; b - SiOa-L-V; 1 - oxygen: 2 - hydroperoxide; 3 - cyclohexenol; 4 - cyclohexenone; 5 - cyclohexane oxide; 6 - cyclohexanol oxide. Points indicate experimental data; curves indicate data calculated by model. The procedure for investigating the kinetics of liquid-phase oxidation of cyclohexene and analysis of the products were described earlier in [I]. Figure 1 presents kinetic curves characterizing the combined process in the presence of an iminodiacetate vanadyl complex chemically fixed on silica or alumina. From these data it can be seen firstly that the composition of the products is identical for both catalysts, and secondly that somewhat unexpectedly there is no great difference in their activity despite the considerable difference in the amount of vanadyl fixed on each of the oxides. This effect cannot be attributed to "peaking" of the effectiveness of the catalyst as the surface o f iminodiacetate-modified oxides is filled with vanadyl ions. As shown by experiments, in this case the amount of oxygen absorbed within 2 hr of the combined process with increase in the degree of filling, for example, of modified alumina with vanadyl ions from 20 to 100~o (of its maximum capacity) increases from 0.2 to 4.6 mole/1. Assuming that the nature of distribution of vanadyl complexes on the surface of the oxides is statistical, as assumed, for example, in Kobozev's "active enseble"
V. V. ~ m c r s v e z o
238
et al.
theory [5], it can be sho~,n that the identical activity of the catalysts with different contents of the active phase may be due to the virtually equal concentration of centres of certain nuclearity on the two of them. Corresponding results of numerical calculations for mononuclear centres in the form of isomolar sections are presented in Fig. 2. Here the maximum capacity of the modified sorbent (in mole/g) is plotted
8
#
/13_/ 0.5
,.<>,,i
Y,
l.O Ci " 105, rnolel9
I
:
Fie. 2. Isomolar sections of dependenceof concentration of mononuclearcentres with variation in maximum capacity of sorbent (X-axis) and average number of complexes in fixation zone (F-axis). Concentration of centres along Z-axis equal to C~x 105, mole/g. along the X-axis, the average number of complexes in the fixation zone ~ along the Y-axis, and the concentration of mononuclear centres on each of them along the Z-axis. The points in Fig. 2 indicate two catalyst variants which will have, for example, an identical number of mononuclear centres (5 x l0 -s mole/g) (points 1 and 2), although their maximum capacities differ almost by an order of magnitude. Of course, this will be possible only when the average of complexes in the fixation zone of one is ,,.2, and in that of the other 4. What is more, the concentration of mononuclear centres in the catalyst of greater maximum capacity may not unexpectedly even be considerably lower than in the catalyst of lower maximum capacity (points 3 and 4), which is also due to the different nuclearity of the complex in the fixation zone for the two catalysts. With account taken of textural features of the oxides used, this seems to us to be entirely realistic and probably predetermined their roughly equal catalytic activity with a considerable difference in maximum sorption capacity. Certain differences in the selectivity of the combined process and, in particular, the slightly greater selectivity of an iminodiacetate VO complex chemically fixed on alumina in cyclohexanol epoxide formation may also be due to the specific nature of the structure of the active surface. Mathematical modelling of the kinetics of the combined process in the presence of synthesized catalysts was based on the
239
Oxidation of.cyclohexene
following e x p e r i m e n t a l facts. W i t h o u t h y d r o p e r o x i d e in t h e system, t h e r e a c t i o n d i d not begin at 348°K even over a p e r i o d o f 4 hr. On the o t h e r h a n d , the k i n e t i c o r d e r o f the r e a c t i o n w i t h respect to oxygen was r o u g h l y equal to unity. In the course o f catalysis, a c c o r d i n g to E P R s p e c t r a o f silica-based c a t a l y s t s t h e r e was a c h a n g e in the v a l e n c y state o f t h e v a n a d y i ions in the catalysts. V a n a d i u m c h a n g e d f r o m t e t r a v a l e n t to p e n t a v a l e n t . This led to a c o n s i d e r a b l e c h a n g e in selectivity o f such a d e v e l o p e d c o n t a c t , s u p p o r t e d ' by the d a t a in T a b l e 2. In p a r t i c u l a r , these TABLE 2.
YIELD OF PRODUCTS (MOLE/L) WITH RE-USE OF
SiO,-L-V
CATALYST IN ]PROCE~F..$ OF
OXIDATION AND EPOXIDATION OF CYCLOHEXENE AT 348°K
120rain; [rn,,]=25 g/I.; [Vl= 1.15 x 10 -3 mole/g; [ROOH]o--0'38 mole/l. Catalyst
Absorption of 02 : ROOH
Initial After use in oxidation After use in epoxidation
ROH
Oxidation 0.42 ] 1.08 10"08 : 1"56 0.56 [ 1"14 Epoxidation 0-04 0-16 0.02 0.18
3'2 5"6 3.2
i
R>O
1.30 1.35
1 "06 0'76 0'87
0"'90 0"84
0-09 0.08
0"22 0"24
0"14 0"16
0"12
0.18
0"13
I
Initial After use in epoxidation After use in oxidation
R(O H) > O
R=O
2.73
1"20
I
0.04
I
0'18
* [ R O O H ] o - - . 0 - 4 8 molo/1.
d a t a show t h a t p e n t a v a l e n t v a n a d i u m ions a r e m o r e active in o x i d a t i o n , while t e t r a v a l e n t , v a n a d i u m ions are m o r e active in e p o x i d a t i o n . U n f o r t u n a t e l y , we are n o t able to j u d g e the n u c l e a r i t y o f the active centres in either case on these basis o f the d a t a o b t a i n e d . C o m b i n e d with d a t a on the d e p e n d e n c e o f the r a t e o f t h e r e a c t i o n on the c o n c e n t r a t i o n o f its m a i n c o m p o n e n t s , all this m a d e it possible to p r o p o s e the following scheme for the c o m b i n e d o x i d a t i o n - e p o x i d a t i o n process ( n u m e r i c a l values o f the rate c o n s t a n t s o f individual stages a n d t h e i r d i m e n s i o n s ) : SiO2 O.
[V'*]~+ROOH~[V4+ROOH)~
9. [V 5 + ] , + R O O H - + [ V 5 + R O O H ] , -
= -
AI203
O
--
-
Q'
-
-
1. Q + O,--*[VS +], + R = O + H20~ 2"5x 10 -2 01. Q"--~[V4+]s+RO2+H,O 6"26x10 -3 2. Q'+ROH--+IVS+],+2RO" + H 2 0 30"0 3. Q'+ROOH-'+IVS+]s+RO" +R.O~ + H 2 0 30"1 4. RO" + R H " * R O H + R " 5. R" +Ov-*RO~ 6. RO'~ + RH--*ROOH'+ R" 60x10 -2 7. RO~ + R . H - , R > O +RO" 2.0 x 10 - s 8. RO,~ + R O ~ - - * R = O + R O H + O 2 9. RO.~ + ROOH--+ROOH + R,= O + HO ' 0"67 10. HO~ + RH"-*HaO + R"
2-5 x I0 -2 l./(mole.min) 6"25x10 -3 min- t 18"0 l./(mole.min) I0"0 l./(mole.min) 6.0 x 10 -2 (l./(mole.min))~ 2.0×10 -3 (l./(mole.min))~ 0"64
240
V.V.
BEREt,rrsv~o et al.
11. HO" + R H ~ H 2 0 + R " 12. Q + RH'-*[V4+],+R> O + ROH t3. Q + ROH--*[V* +]. + R(OH) > O + R O H
-
7"5 130.0
-
1"5 20.0
l./(mole.min) I./(mole.min)
Here ROOH is cyclohexenyl hydroperoxide, R H is cyclohexene, ROH is cyclohexanol, R = O is cyclohexenone, R > O is cyclohexane oxide, R[OH] > O is cyclohexanol oxide, [V* +]s [Vs + ]s is heterogenized IDAC of tetra- and pentavalent vanadyl, and Q and Q' are hydroperoxide complexes on the surface of the heterogeneous catalyst with V(V) and V(IV) respectively. Stages I--4 are actually stages of chain initiation with account taken of the autocatalytic nature of the process because of its acceleration by the cyclohexenol (stage 2) and hydroperoxide (stage 3) formed in the system. The inverse kinetic problem with different initial conditions was solved on an SM-4 machine by the procedure described in [6]. The numerical values of the constants found for different stages of the combined process are given above. The best description for both catalysts was obtained on the assumption that the constants of stages 1 and 01 for them are identical, while the constants of stages 2, 3, 12, and 13 (which are actually certain effective parameters since they contain the unknown concentrations of active centres of some specific nuclearity) are different. On this assumption, it is entirely logical that numerical estimates of the constants of stages 5, 6, and 7, which are not associated with the participation of a catalyst, are practically identical for the two catalysts. Description of experimental data within the framework of the given scheme is illustrated in Fig. 1, where calculated kinetic curves are presented by the continuous lines, and experimental kinetic curves by the points. Consequently, iminodiacetate vanadyl complexes chemically fixed on silica or aluminium are fairly effective catalysts of the combined oxidation and epoxidation of cyclohexene. Differences in the properties of the two catalysts obtained can be attributed both to the nature of the oxide support investigated (the difference in the distribution and reactivity of surface OH groups) and to the difference in their texture, which determines the distribution of the active component on the surface of the support. Strictly, the effectiveness of the active centre of catalysis is probably roughly identical for the two cases. This is determined by the specific nature of their structure: according to the catalyst production scheme presented above, the vanadyl complexes are actually 1.0-1.5 nm away from the surface of the support and therefore not very "sensitive" to its nature. SUMMARY
1. In the presence of iminodiacetate vanadyl complexes fixed on silica or alumina, combined liquid-phase oxidation and epoxidation of cyclohexene takes place. 2. The process proceeds by a heterogeneous-homogeneous radical-chain mechanism with autoacceleration on account of the cyclohexenol and cyclohexenyl hydroperoxide accumulated in the system. 3. The texture of the supports used has a greater effect on the distribution of
N-2-pyridyldialkylthioamides as additives to lubricating oils
241
active centres (iminodiacetate vanadyl complexes) on the surface of the catalysts than the nature of the supports. This leads to a certain difference in the activity and selectivity of the catalysts in the combined process. REFERENCES
1. V. V. BERENTSVEIG, CHAN BIK NGA, T. V. BARINOVA and G. V. LISICHKIN, Kinetika i kataliz 25, 5, 1477, 1984 2. S. A. NIZOVA, N. N. BUYANOVA, S. P. LUCHKINA, Ye. P. KRYSIN and L. G. A.NDRONOVA, Neftekhimiya 15, 5, 765, 1975 3. G. V. KUDRYAVTSEV, G. V. LISICHKIN, Yu. A. SAPOZHNIKOV and R. A. KUZNETSOV, Auth. Cert. 850204 (U.S.S.R.). Byull. izobr., 28, 53, 1981 4. S. T. ROSS, J. Chem. Phys. 42, 3919, 1965 5. N. I. KOBOZEV, Izbrannye trudy (Selected Proceedings), Vol. 1, p. 134, MGU, Moscow, 1978 6. S.V. KRIVENKO, L G. SYSHCHIKOVA, A. M. YEVSEYEV and V. V. BERENTSVEIG, Kinetika i kataliz 24, 6, 1299, 1983
Petrol. Chem. U.S.S.R. Vol. 28, No. 4, pp. 241-245, 1988 Printed in Poland
0031-6458/88 Sl0.00+ .00 ~D 1990 ]Pergamon Preu pie
N-2-PYRIDYLDIALKYLTHIOAMIDES AS ADDITIVES TO LUBRICATING OILS* A. B. KULIYEV, T. SH. GASANOVA, N. O. AKHADOV a n d S. A. MAMEDOV Institute of Chemistry of Additives, Azerbaidzhan Academy of Sciences, Baku (Received 30 March 1988) THE results of earlier investigations showed that primary thioamides are effective additives to lubricating oils [1-3]. In order to find more effective additives, in the present study secondary thioamides (N-2-pyridyldialkanethioamides) were synthesized, and their effect on the quality of lubricating oils was investigated. Interest in the given compounds is due to the fact that N-2-pyridyldialkanethioamides contain double the quantity of thiocarbonyl groups (C = S) possessing high activity in relation to metals [4]. N-2-pyridyldialkyhhioamides were synthesized by the interaction of phosphorus pentasuiphide with N-2-pyridyldialkylthiamide [1-3], and the latter were obtained by the reaction of corresponding carboxylic acid. chlorides with 2-aminopyridine * Neftekhimiya 2,8, No. 6, 809-812, 1988.