Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, 580-585
580
Table VIII. Compounds Identified by Gas Chromatography peak no.
compounds
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
air butane isopentane and 3-methylpentane pentane and cyclopentane 2,3-dimethylpentane and methylcyclopentane hexaneand cyclohexane cyclohexene heptane isooctane, benzene, and thiophene cyclooctane and toluene n-nonane ethyl benzene p-xylene, m-xylene, and styrene o-xylene decane propyl benzene mesitylene pyrrole piperidine and tetralin naphthalene
column. By injecting the pure components with the sample and comparing them with those obtained, we were able to identify 20 compounds in the product which are listed in Table VIII. Conclusion The hydrotreatment of heavy gas oil was investigated over a Mo-Co-A1203 catalyst (Harshaw Co.) in a trickle bed reactor at temperatures of 300-450 "C and pressures of 600-1800 psig. The catalyst could remove up to 92% S and 72% N from the heavy gas oil under experimental conditions. A t temperatures higher than 400 "C and
LHSV smaller than 2, considerable cracking was observed. A t higher pressures (>1200 psig) products of lower C/H ratios were obtained indicating better hydrogenation activity of the catalyst. Cetane number and diesel index of the products improved with increased temperature. Asphaltene conversion took place according to the possible mechanism: asphaltene resin type compounds oils. Acknowledgment The authors are grateful to the National Science and Engineering Research Council of Canada for financial aid (A-1125). Literature Cited
-
-
Arnold, M. F.; Perham, C.; Ettre, L. S.; Welton, E. Chromatog. Newslefter 1978, 6(1), 12. American Society for Testing and Materials, Philadelphia, PA, Code Designation numbers D976-66, D66-67, and D611-64. Ashley, J. H.; Mitchell, P. C. H. J . Chem. Soc.A 1989. 2730. Beuther, H.; Flinn, R. A.; McKinley, J. B. Znd. Eng. Chem. 1959, 57(11). 1349. Frost, C. M., Cottingham U . S . Dept Interior, Bur. Mines, Rep. Invest. 7478, 1970. Furminsky, E. AZChE J . 1979, 25(2), 306. Giordano, N.; Bart, J. C.; Vaghi, A.; Castellan, A,; Martinolti, G. J . Catai. 1975, 36, 81. Gupta, R. K.; Mann, R. S.; Gupta, A. K. J . Appl. Biotechnol. 1978, 28, 641. Katritzky, A. R. Quart. Rev. 1979, 73, 353. Lovetro, D. C.; W e b , S . W. Znd. Eng. Chem. Prod Res. Dev. 1977, 76(4), 297. Mirza, Aziz; Massod, M. S.; Mallikarjunan, J. M.; Vaidyeswaran, R. Pet. Hydrocarbons 1988, 3, 13. Moschpedis, S. E.; Speight, J. G. Fuel 1976, 5 5 , 167. Parsons, 6. I.; Ternan, M. 6th Znt. Congr. Catal. England 1977, 2 , 965. Rao, C. N. R . "Chemical Applications of Infra-red Spectroscopy"; Academic Press: New York, 1963. Speight, J. G. "The desulfurization of Heavy Oils and residues"; Marcel Dekker, Inc.: New York, 1981.
Receioed for review January 11, 1982 Revised manuscript received June 28, 1982 Accepted August 13, 1982
Gas-Phase Polymerization of Propene with the Supported Ziegler Catalyst: TiCI,/MgC12/C6H5COOC2H5/AI(C2H5) Yoshlharu Dol,' Masahlde Murata, and Karuhlsa Yano Research Laboratory of Resources Utilization, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, Yokohama 227, Japan
Tomlnaga Keli Numazu College of Technology, Ooka 3600, Numazu-shi, Shizuoka-ken 4 10, Japan
The gas-phase polymerization of propene with the MgCI,-supported TiCI,/C,H,COOC,H, catalyst in conjunction with AI(C2H,), has been investigated. The rate of polymerization depends on both titanium content and surface area of the MgCITsupported catalyst and decreases with the polymerization time. The number of active centers in the catalyst at different polymerization times is estimated by the inhibition method using carbon monoxide. As a result, the number of active centers decreasesjuring the course of polymerization, but the mean propagation rate constant k , remains constant. The value of k , is one order of magnitude larger than that in the conventional TiCI, catalyst.
Introduction The gas-phase polymerization of propene with ZieglerNatta catalysts is of great industrial significance since the use of solvent is obviated.
Keii et al. (1961) and Kanetaka et al. (1964) found that the TiC13 salt with AlC13 shows some activity in the gasphase polymerization of propene. Doi et al. (1972a) examined the gas-phase polymerization of propene over TiCl?
0196-4321/82/1221-0580$01.25/00 1982 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 4, 1982 581
Table I. Titanium Contents and Surface Areas of in combination with A1(C2H5),or A1(C2H5)2C1 using a reMgC12-Supported Catalysts actor with a mechanical agitation system (of 400 rpm stirring speed), and they pointed out two advantages of surface the gas-phase polymerization: higher stereospecificity in Ti content, area," the case with A1(C2H5)3as cocatalyst and higher catalyst cat. wt % mz/g efficiency. In addition, Doi et al. (1972b, 1973,1980)made 68 MgCL(A) kinetic studies of the gas-phase polymerizations of propene A- 1 0.48 48 with several conventional Ziegler-Natta catalysts based A- 2 1.13 44 5.5 MgC&(B) on TiC1, and showed that there is no appreciable difference B-1 1.02 4.6 in the number of active centers in the gas-phase and slurry polymerizations. Prabhu et al. (1980, 1981) studied the " Surface area measured by the BET method of nitrogen adsorption at -196 "C. block copolymerization of ethylene and propene in the gas-phase process using TiC13-Al(C2H5)2C1catalyst. The BASF gas-phase process for the polymerization of propene equipped with a Teflon stirrer and three side arms. In has been outlined by Wisseroth (1969,1977). A significant order to assure good dispersion of the catalyst, about 4 cm3 extension of Wisseroths work on the kinetics for gas-phase of glass beads (0.5 cm diameter) were added in the reactor. polymerization of propene using TiC13 catalyst has been After a prescribed amount (0.1-0.5 g) of catalyst sample made by Brockmeier (1979). and 1.0 cm3 of A1(C2H5)3solution in heptane were mixed Recently, highly active, supported Ziegler catalysts for for 1min at a Polymerization temperature under a nitrogen propene polymerization have been reported (Munoz-Esatmosphere in the reactor, the catalyst mixture was dried calona and Villalba, 1977; Suzuki et al., 1979; Soga et al., under vacuum for 4 min to remove heptane. Polymeri1979, 1980, 1981; Duck et al., 1979; Galli et al., 1981; Gization was started by introducing propene. The stirring annini, 1981). A variety of inorganic supports for titanium speed was 400 rotations/min. The propene pressure and compounds have been claimed in the patent literature the temperature during the polymerization could be ad(Sivaram, 19771, the most common being magnesium justed within 5 torr and 0.3 OC. The polymerization rate chloride treated with Lewis bases such as ethyl benzoate. was determined from the rate of propene consumption, In general, the supported Ziegler catalysts have been used measured by a flowmeter. The error of the rate meafor the slurry polymerization of propene in a hydrocarbon surement did not exceed k0.5 cm3 min-l. When required, diluent. prescribed amounts of carbon monoxide were admitted by In the present study, we have carried out the gas-phase means of a syringe through the side arm sealed with silicon polymerization of propene with the highly active supported rubber packing. The procedure of the gas-phase polymand catalyst, TiC14/MgC12/C6H5COOC2H5/A1(C2H5)3, erization using the conventional catalysts, 6-TiC13/A1determined the number of active centers [C*] and the (C2H5),C1and 6-TiC13/A1(C2H5)3, was the same as that value of the propagation rate constant k,, examining the described in a previous paper (Doi et al., 1972a). The inhibition effect of carbon monoxide on the polymerization polymerizationswere quenched by introducing 100 cm3 of rate. The values of [C*] and It, are compared with the a solution of hydrochloric acid in ethanol, and the resulting values in the case with the conventional catalysts based polymers were washed several times with 200 cm3 of ethon TiC1,. anol and dried under vacuum at 50 "C. Analysis. The isotactic index (1.1.)of polymers proExperimental Section duced was represented by the weight fraction of polymer Materials. Propene (purity 99.9%, major impurity residues in boiling heptane extraction for 15 h. being propane) supplied from Mitsubishi Petrochemical 13C NMR spectra of polypropylenes were recorded on Co. was used after it was passed through columns of moa JEOL FX-200 spectrometer operating at 50.10 MHz lecular sieves 13X and 3A. Nitrogen (extra pure grade) under proton decoupling in the FT mode. Solutions of was used after it was passed through columns of molecular polymers were made up in o-dichlorobenzene to 1.0 g/5 sieves 13X and 3A, and then a copper column operating cm3 and the temperature for measurement was 135 "C. at 350 "C. Anhydrous magnesium chlorides of different The molecular weights of the polymers were measured surface areas (MgC12-A 68 m2/g, MgClZ-B 5.5 m2/g) and by gel permeation chromatography (GPC) (Waters Asso6-TiC13(TiC13.1/3AlC13:15 m2/g) were supplied from Toho ciates, Model 200) using five polystyrene gel columns (lo', Titanium Co. TiC14 (pure grade, Kanto Chemical Co.), lo6, lo5, lo4, and lo3 A pore sizes) and o-dichlorobenzene C6H5COOC2H5(pure grade, Tokyo Kasei Kogyo Co.), and as solvent at 135 "C. alkyl aluminums, A1(C2H5),and A1(C2H,J2C1(Japan AluResults and Discussion minium Alkyl Co.) were used without further purification. Preparation of the Supported Catalysts. Three Polymerization Rate. Figure 1 shows the rate-time samples (A-1, A-2, and B-1) of the supported catalyst, curves during the gas-phase polymerization of propene at TiC14/MgC12/C6H5COOC2H5,were prepared by the fol41 "C with the MgC12-supportedcatalysts (A-1, A-2, and lowing procedure. Anhydrous MgClZ-Aor MgC12-B(15 g) B-1) in conjunction with A1(C2H5)3.The rate of polymwas ground by ball-milling for 20 h in the presence of a erization depends on both titanium content and surface prescribed amount (1.5-3.0 cm3) of C8H5COOCzH6.The area of the MgCl,-supported catalyst, and decreases in the order: A-1 > A-2 > B-1. For comparison, the kinetic curve ground mixture (15 g) was treated with 13-26 cm3of TIC& at 80 "C for 2 h in a glass flask equipped with a magnetic of the gas-phase polymerization of propene with the constirrer. After the soluble part was filtered out through a ventional Ziegler-Natta catalyst, 6-TiC13/A1(C2H6)3,is represented by curve D in Figure 1. It was confirmed also glass filter, the solids were washed several times with 100 in the gas-phase polymerization that the MgCl,-supported cm3 of heptane and dried under vacuum at room temcatalyst shows high activity in comparison with the conperature. The titanium contents and surface areas of the ventional catalyst based on 6-TiC13. three catalyst samples are given in Table I. Polymerization Procedure. The gas-phase polymerAs Figure 1shows, the rate of polymerization with the izations of propene were carried out under a constant MgClz-supportedcatalysts decreases gradually during the pressure of propene in a glass-made 600-cm3 reactor course of polymerization. The rate of decay during po-
582
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 4, 1982
1
.-.
-U.*..t-t--Ch . ..~ ....~. ...... ..-~. ~..
;
60
30
90
120
0
Figure 1. Kinetic curves of gas-phase polymerization of propene with different catalyst systems at 41 OC under 760 torr of propene pressure: (curve A) A-1/Al(C2H6)3,(Ti) = 0.08 mmol, and (Al)/(Ti) = 15 mol/mol; (curve B) A-2/Al(CzH&, (Ti) = 0.08 mmol, and (Al)/(Ti) = 14 mol/mol; (curve C) B-1/Al(C2H5)3,(Ti) = 0.08 mmol, and (Al)/(Ti) = 8 mol/mol; (curve D)d-TiC13/Al(C2H,)3,(Ti) = 1.5 mmol, and (Al)/(Ti) = 4 mol/mol.
20
10
Figure 2. Effect of intermission of polymerization on the rate. Polymerization conditions: A-1/A1(C2H&, 41 OC, 760 torr, (Ti) = 0.08 mmol, and (Al)/(Ti) = 15 mol/mol.
50
)
P I Torr
001
002
[W,]
lmin
mod
Figure 3. Effect of (Al)/(Ti) molar ratio on the average rate R of polymerization in 2 h (0) A-1/A1(C2H5),at 41 "C; ( 0 )A-2/A1(C2H5)3at 41 "C; (0)B-1/Al(C2H5)3at 38 "C; (Ti) = 0.08 mmol and propene pressure = 760 torr.
0
-1r-c
40
30
( A I ).:T I )-' i ( mol
Time, n i n
003
004
dw-3)
/(IO,
Figure 4. Effect of propene pressure (concentration) on the average rate R of polymerization in 2 h. Polymerization conditions: B-1/ Al(C,H,),, 38 "C; (Ti) = 0.08 mmol and (Al)/(Ti) = 8 mol/mol. 20,
lymerization can be represented by a second-order decay law as
where R, is the rate a t time t, Ro is the initial rate, and k d is the second-order decay constant. The second-order rate decay during polymerization has also been observed in the slurry polymerization of propene in heptane solution (Suzuki et al., 1979). In the polymerization with highly active catalysts, the polymerization rate may be affected by propene monomer diffusion through polymer layer covering the surface of the catalyst or enveloping the catalyst particles, as pointed out by Eley et al. (1977) and Nagel et al. (1980). Then, the effect of intermission of polymerization was examined by means of the substitution of nitrogen for propene monomer during the course of polymerization. The result is shown in Figure 2. The rate decay takes place during the intermission of polymerization under nitrogen, indicating that the rate decay is not caused by the polymer produced. Therefore, it can be concluded that the monomer diffusion through the polymer layer is not responsible for the rate decay. The mechanism of the rate decay will be discussed in the final section together with the other experimental results. Figure 3 shows the relation between the average rate R of polymerization in 2 h and the molar ratio of aluminum to titanium, (Al)/(Ti). The average rate attains a maximum value at (Al)/(Ti) molar ratio of 10-15 in all the cases with the MgClz-supported catalysts. The average rate R of polymerization is first order with respect to the concentration o f propene [MI, as shown in Figure 4. The effect of temperature on polymerization rate was examined under 760 torr o f propene pressure using two
01
t
30
31
38
103. T-I i K-!
Figure 5. Relation between log (E/[M]) and 1/T. (0)A-1/Al(CZH6)3$(Ti) = 0.08 mol, (Al)/(Ti) = 15 mol/mol, and 760 torr; ( 0 ) B-1/Al(C2H6)3,(Ti) = 0.08 mmol, (Al)/(Ti) = 8 mol/mol, and propene pressure = 760 torr.
catalyst systems, A-l/Al( C,H,), and B - l / Al( C2H5),. Figure 5 shows the relation between log (R/[M]) and 1/T. The optimum temperature for polymerization is -55 "C. The apparent activation energies are determined as 5.3 kcal mol-' for both catalyst systems at temperatures below 41 "C. Isotacticity and Molecular Weight of Polymers. Table I1 summarizes the isotactic index I.L, the numberaverage molecular weight &fn, and the polydispersity Mw/Mnof the polymers produced with three different MgClz-supported catalysts and A1(CZH5),.As can be seen from Table 11, the isotactic index of polymers decreases from 94% to 44% with increasing (Al)/(Ti) molar ratio, and it increases with increasing polymerization temperature. Table I11 gives the steric pentad compositions of two fractions (1.7 and S.7) of polypropylenes, determined from the methyl carbon pentad intensities of the I3C NMR spectra. Fractions 1.7 and S.7 are the polypropylenes in-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 4, 1982 583 Table 11. Isotactic Index and Molecular Weight of Polypropylenes Obtained with MgCl, -Supported Catalysts and Al(C,H,), a (Al)/ iso(Ti), tactic mol/ index,b mol wt% 4 82 8 81 15 70 19 62 4 94 85 8 14 68 75 8 8 76 79 8 79 8 4 91 8 81 11 59 16 63 20 52 30 47 46 44 8 82 8 85 8 83
temp, "C 41 41 41 41 41 41 41 1 7 16 24 38 38 38 38 38 38 38 54 64 65
cat. A- 1 A- 1 A- 1 A- 1 A- 2 A- 2 A- 2 B- 1 B- 1 B- 1 B- 1 B- 1 B- 1 B- 1 B- 1 B-1 B- 1 B- 1 B-1 B- 1 B- 1
40
t
1
co
mol wt
M,,
a?/ M"
Time i m i n
Figure 6. Change in the rate induced by the addition of CO during the gas-phase polymerization of propene with 6-TiC1,/A1(C,H5),C1 ((CO)/(Ti) = 0.003 mol/mol); 41 OC, (Ti) = 2.5 mmol, (Al)/(Ti) = 4 mol/mol, and propene pressure = 760 torr. 7.3 2.5 2.2
5.8 5.4 5.9
4.2
7.7
Number of Active Centers. In order to elucidate the kinetic feature of active centers in the MgC1,-supported catalyst, a comparison between the numbers of active centers has been made for the catalyst systems, TiC1.J MgC12/CGH5COOCzH5/Al(C2H5)3 and 6-TiC13/Al(CzH5)2C1. To evaluate the number of active centers, we use an inhibition method to determine the minimum amount of carbon monoxide necessary to stop the polymerization. Figure 6 shows the change in the rate induced by the addition of carbon monoxide ([CO]/[Ti] = 0.003 mol/mol) during the gas-phase polymerization of propene with 6TiC1,/A1(CZH5),C1catalyst. The addition of a small amount of CO into the polymerization system results in a rapid depression in the rate of polymerization. After the attainment of a minimum value, the rate increases gradually to reach its original value. The inhibiting effect of CO and the subsequent recovery of polymerization activity may be interpreted in terms of the following reaction sequence proposed by Caunt (1981)
Polymerization conditions: (Ti) = 0.08 mmol and propene pressure = 760 torr. Weight fraction of polymers insoluble in boiling heptane.
soluble and soluble in boiling heptane, respectively. In fraction 1.7 small amounts of steric defects are observed with the following relation in steric pentad composition [mmmm] >> [mmmr] = [mmrr] = 2[mrrm]
(2)
Then, the steric defects in the isotactic chain are represented as
Ti-CH2P
I
+
CO
-
-
Ti-CH2P
I
m
m
m
m
m
r
1 r
(3)
m m m m m m - - - - -
II
'J I
(5)
U
+
T!-C-CH,P
'\\.J
where the angular symbols in the top line indicate the propylene units in the orientation, m is an isotactic (meso) diad, and r is a syndiotactic (racemic) diad. The value (90%) of [mmmm] in the 1.7 fraction is the same as that (90%)in the 1.7 fraction of polypropylenes obtained in the slurry polymerization with the TiC14/MgC12/ C&5COOC2H5/Al(C2H5)3 catalyst system (Doi et al., 1981). The steric pentad composition of the fraction S.7 shows the following relations [mmmm] > [mmmr] > [rmmr] [rrrr] > [rrrm] > [mrrm]
'\
0
_____ JJ_J_I_I J_1J A JJ_I_J_i----- - _ - -m
Ti-C-CH,P
rH5 +
AI(C2H51,CI
(PCH,CO)AI(C,H,)CI
(6)
where is a free coordination site and -CH2P is a polymer chain. After the polymerization rate decreased suddenly by the addition of CO, no residual CO in the gas phase was detected by gas chromatography. Examples of irreversible insertion of CO into a titanium-alkyl bond have been reported by Fachinetti et al. (1974,1977) in the reaction of CO with dicyclopentadienylhaloalkyltitanium, (q5C5H5)2Ti(X)R,to give the acyl derivative, (v5-C6H5),Ti(X)(COR). The slow reaction (6) of a titanium-acyl bond with alkylaluminum may result in the formation of new active center. We estimated the residual rate just after poisoning by CO by means of extrapolation of the gradual recovery into the time when CO was added, as shown in Figure 6. Figure 7 shows the relation between the residual
(4)
The observed distribution of steric pentads cannot be accounted for by Bernoullian propagation statistics of a one-parameter model (Bovey, 1968). The atactic polypropylenes seem to contain the chains consisting of both isotactic and syndiotactic stereoblocks (Doi, 1982). Table 111. Stereoregularity of Each Fraction of Polypropylenesa polymer fraction
steric pentad fraction in %
in wt no.
I. 7 s.7
%
[mmmm]
81 19
90 39
[mmmr] 4 12
[rmmr]
[mmrr]
[mrmm] [rmrr]
5
4 11
8
[rmmr] 3
[rrrr]
[rrrm]
[mrrm]
10
8
2 4
a Polypropylenes obtained a t 4 1 "C with the catalyst system, A-l/Al(C,H,), . 1.7: fraction insoluble in boiling heptane; S.7: fraction soluble in boiling heptane. Determined from the methyl carbon pentad intensities of '%NMR spectra.
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Ind. Eng. Chem. Prod. Res. Dev., Vol. 21, No. 4, 1982
Table I V . Number of Active Centers, [ C* 1, and Mean Propagation Rate Constants, E,, of the Gas-Phase Polymerization of Propene with Different Catalyst Systems - __-__ - -- --_102 [ c * 1, k,, d m 3 / cat. system temp, 'C time, min molimol of Ti mol s _I
.
I
__
%:
{i$
6 -TiCl3/A1(C2H,),C1 h -TiCl, /A1( C,HS),' a
41 '40
10 60
10 30 60 80
6.8 t 3.8 i 1.6 i 1.0 i 0.6 i 0.8 t 1.5 t
0.3 0.3 0.2 0.1 0.1 0.1 0.5
3 0 0 i 15 3 2 0 i 25 320 i. 40 320t. 30 360 t 60 32t 3 3 1 2 10
From a previous paper (Doi e t al., 1980).
-
1
I
'7
3O)(T
C6
'
:e
XI3
70-11
Figure 7. Relation between polymerization rate and the amount of CO added. The polymerization conditions are the same as those in Figure 6
F . ?
-
n
Figure 9. Relation between polymerization rate and amount of CO added at 10, 30, and 60 min of polymerization times. Polymerization conditions are the same as those in Figure 8 (0) the rate at 10 min; ( 0 )the rate ate 30 min; ( 0 )the rate at 60 min
a tcc,
Figure 8. Changes in the rate induced by the addition of CO during the gas-phase polymerization of propene with the MgC12-supported catalyst system, B-1/Al(C2H,),; 38 "C, (Ti) = 0.11 mmol, (Al)/(Ti) = 8 mol/mol, and propene pressure = 760 torr; (A) CO added at 10 min; (B) CO added at 30 min
rate and the amount of CO added during the polymerization. The polymerization activity disappears completely at 0.008 f 0.001 mol of CO/mol of TiC13,where all active centers react with CO. Assuming that an active center reacts with one molecule of CO, we determined the number of active centers [C*] as 0.008 f 0.001 mol/mol of Ti. The value of [C*] is essentially consistent with the value (0.006 f 0.001 mol/mol of Ti) determined by Schnecko et al. (1969, 1975) using other methods in the slurry polymerization of propene with 6-TiC13/A1(CzH5)zC1 catalyst. The deviation from the linear dependence of the amount of CO on the rate in Figure 8 may be interpreted in terms of the surface heterogeneity that some centers are more reactive for both the polymerization and the reaction of CO than others. Figure 8 shows typical changes in the rate induced by the addition of CO during the course of gas-phase polymerization of propene with the MgClz-supported catalyst system, B-l/Al(C2H5)3.The relation between the residual rate and the amount of CO was examined at 10, 30, and 60 min of polymerization times, since the polymerization rate decreased with the time. The result is shown in Figure 0. Figure 10 shows the dependence of the residual rate on the amount of CO observed with the highly active catalyst system, A-1/A1(C2H5),. The numbers of active centers [C*], at time t are determined from Figures 9 and 10 and are listed in Table IV, together with the values of
T
j-?
ii-01
mal-')
Figure 10. Relation between polymerization rate and the amount of CO observed in the gas-phase polymerization of propene with the highly active catalyst system, A-1/Al(C2H5)3;41 "C, (Ti) = 0.08 mmol, (AI)/(Ti) = 15 mol/mol, and propene pressure = 760 torr; (0) the rate at 10 min; ( 0 )the rate at 60 min.
mean propagation rate constant k, which are calculated from the relation
R, = ~,[Ml[C*l,
(7)
where R, is the polymerization rate a t time t and [MI is the concentration of propene monomer in the gas phase. As shown in Table IV, the values of [C*], decrease during the course of polymerization, but the values of k, remain constant. The decrease in the number of active centers during polymerization could be expressed by
or
Applying eq 9 to eq 1 and 7 , we have (10)
We verified that the second-order decay constant kd in eq 1 is inversely proportional to the concentration of propene monomer. Then, we have concluded that the rate decay during polymerization is attributed to the second-order deactivation (disproportionation) of active centers resulting
585
Ind. Eng. Chem. Prod. Res. Dev. 1982,21, 585-590
in the reduction of Ti3+to Ti2+. As Table IV shows, the values of hp in the MgC12-supportedcatalysts are larger than the values of h in the conventional catalysts based on 6-TiC1, by one orjer of magnitude. The MgC1, support must influence the electronic structure of the active titanium-polymer chain bond by inductive effects. The electron-withdrawing capability of the MgC12 support seems to instabilize an active titanium-carbon bond, resulting in the higher value of k . An activation effect of MgC12 may be supported by t i e fact that an apparent activation energy (5.3 kcal mol-') for polymerization with the MgCl,-supported catalysts is lower than the value (12 kcal mol-') of polymerization with the 6-TiCl3/A1(C2H6), catalyst (Doi et al., 1973). Literature Cited Bovey, F. A. Acc. Chem. Res. 1968, 1 , 175. Brockmeier, N. F. I n "Polymerization Reactors and Processes"; Henderson, J. N., Ed.; ACS Symposium Series 104, Washington, DC, 1979; p 201. Caunt, A. D. Br. Polym. J. 1981, 13, 22. Dol, Y.; Okura, I.; Keii. T. Chem. Lett. 1972a, 327. Doi, Y.; Yoshimoto, Y.; Keii, T. Nippon Kagaku Kalshl 1972b, 495. Doi, Y.; Kobayashi, H.; Keii, T. Nippon Kagaku Kaishi 1973, 1089. Doi, Y.; Morinaga, A,; Keii, T. Makromol. Chem. RapM Commun. 1980, 1 , 193. Doi, Y.; Suzuki. E.; Keii, T. Makromol. Chem. RapM Commun. 1981, 2 , 293.
Doi, Y. Makromol. Chem. RapMCommun. 1982, 3 , 635. Duck, E. W.; Grant, D.; Kronfli, E. €or. Polym. J. 1979, 15, 625. Eley, D. D.; Keir, D. A.; Rudham, R. J. Chem. SOC.,Faraday Trans. 1977, 73, 1738. Fachinetti, G.; Florianl, C.; Soeckli-Evans, H. J. Chem. Soc ., Dalton Trans. 1977, 2297. Galli, P.; Luciani, L.; Cecchln, G. Angew. Makromol. Chem. 1981, 9 4 , 63. Giannini, Y. Makromol. Chem. Suppl. 1981, 5 , 216. Kanetaka, S.;Takagi, T.; Keii, T. Kogyo Kagaku Zasshi 1984, 6 7 , 1436. Keii, T.; Takai. T.; Kanetaka, S. Shokubai 1981, 3 , 210. Muiioz-Escaiona, A.; Villalba, J. Polymer 1977, 18, 179. Nagei, E. J.; Kirillov, V. A.; Ray, W. H. Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 372. Prabhu, P.; Shindler, A,; Theii, M. H.; Gilbert, R. D. J. Polym. Sci., Polym. Lett. Ed. 1980, 18, 389. Prabhu, P.; Shlndler, A.; Theil, M. H.; Gilbert, R. D. J. Polym. Sci., Polym. Chem. Ed. 1981, 19, 523. Schnecko, G.; Dost, W.; Kern, W. Makromol. Chem. 1969, 121, 159. Schnecko, H.; Jung, K. A.; Kern, W. I n "Coordination Polymerization"; Chien, J. C. W., Ed.; Academic Press: New York, 1975; p 91. Sivaram, S. Ind. Eng. Chem. Prod. Res. Dev. 1977, 16, 121. Soga, K.; Terano, M.; Ikeda, S. Polym. Bull. 1979, 1 , 849. Soga, K.; Izumi, K.; Terano, M.; Ikeda, S. Makromol. Chem. 1980, 181, 657. Soga, K.; Terano, M. Polym. Bull. 1981, 4 , 39. Suzuki, E.; Tamura, M.; Dol, Y.; Keil, T. Makromol. Chem. 1979, 180, 2235. Wlsseroth, K. Angew. Makromol. Chem. 1989, 8 , 41. Wisseroth, K. Chem. Ztg. 1977, 101, 271.
Received for review March 29, 1982 Accepted August 17, 1982
Ethylene Addition to Lower n-Olefins with Potassium-Graphite Catalysts John B. Wllkes Chevron Research Company, Richmond, California 94802
Potassium-graphite intercalation compounds were shown to catalyze the addition of ethylene to C, to C, n-olefins to give a preponderance of linear olefinic products. Addition of ethylene to 2-pentenes with KC,-KC,, mixtures made from pure graphite gave 57% linear 3-heptenes and 37% 3-ethyI-1-pentene compared to 19% 3-heptenes and 54 % 3-ethyl-1-pentene produced at similar conditions with catalyst prepared from potassium metal dispersion. With catalysts varying from KC8 to KC24, the rate of reaction was proportional to the amount of KC, and not to the amount of potassium. Varying the reaction temperature had only a small effect on reaction rates. Olefin isomerization was catalyzed by potasslum-graphite catalysts made from graphite containing a significant amount of ash. A new method of preparing potassium-graphite intercalation compounds by reaction of graphite with molten potassium dispersions in liquid hydrocarbon is described.
Introduction The reaction of lower olefins with alkali metal catalysts gives a variety of valuable dimers and codimers. The olefinic isomers produced are usually not those which are most stable thermodynamically (Pines and Stalick, 1977). Potassium, rubidium, and cesium are the most active catalytic materials. In most studies of these reactions, the catalyst has been formed from potassium metal introduced into the reaction mixture. Potassium hydride has occasionally been used. Supported or fiiely divided potassium metal reacts with propylene to form organopotassium compounds (Wilkes, 1967a). Organopotassium compounds, rather than potassium metal or potassium hydride, are probably the actual catalysts in most of these potassiumcatalyzed oligomerization reactions of olefins. Potassium and graphite react to form intercalation compounds which are catalytically active (Boersma, 1974). Although these intercalation compounds are substantially different in structure from supported or unsupported potassium, and
may act differently as catalysts, graphite has often been considered to act only as a support in these olefin-oligomerization reactions. Propylene dimerization at 150 "C was studied by Hambling (1969) with both graphite and potassium carbonate as supports. Sodium-graphite had considerably less selectivity than sodium on potassium carbonate (which presumably was reacted to form potassium and sodium carbonate) for dimerization of propylene to 4-methyl-l-pentene, but a catalyst of potassium on potassium carbonate gave results similar to those obtained with KCs potassium-graphite catalyst. Although the KCs catalyst was only 42% as active as potassium on K2C03, only minor differences were found in the product distributions. KC8 catalysts dimerized propylene to give 4% n-hexenes, compared to 8% n-hexenes with potassium on K,C03, and the two catalysts gave similar selectivities of 79% and 75% to 4-methyl-1-pentene. KCZ4and KC60catalysts showed considerable activity for iscmerization of the 4-methyl-1-pentene to the more
0196-4321/82/1221-0585$01.25/00 1982 American Chemical Society
