Ind. Eng. Chem. Process Des. Dev. 1985, 2 4 , 525-530
525
Kinetics of Deamination of Diethylenetriamine over an Alumina Catalyst+ Y. S. Bhai, B. D. Kulkarnl, and L. K. DOra18Wamy' National Chemical Laboratory, Poona 4 1 1 008 India
Kinetics of vapor-phase deamination of diethylenetriamine over an alumina catalyst was studied. A number of catalysts have been screened for the deamination reaction. A plausible reaction network (consisting of nine steps) has been proposed from the product distribution study on the best catalyst by means of both integral and internal circulation (Berty) reactor data. Kinetic constants and e7tivation energies for various steps of the reaction network have been evaluated.
Introduction Piperazine is used mainly for the preparation of anthelmintics and as a starting material in the manufacture of dyes. Commercially it is manufactured by the catalytic deamination and cyclization of alkylene polyamines such as ethylenediamine (EDA) and diethylenetriamine (DETA) in the liquid phase at about 250 OC and lo00 psi pressure. The process, however, suffers from a number of disadvantages common to batch processes: for example, separating the catalyst from the product. The simpler vapor phase process is therefore gaining considerable importance. Pfann et al. (1942) first reported that the deaminocyclization of DETA to piperazine in the vapor phase is possible. This was followed by a paper by Anderson et al. (1967) in which they also reported the feasibility of deamination of DETA in the vapor phase on aluminum oxide and kaolin. After this no study has been reported on this system in the open literature. Though the possibility of the vapor-phase deamination of DETA has been established from the reports of earlier workers, no systematic study on the basic information needed to design a vapor phase reactor for this reaction is available. Considering the importance of this reaction in the synthesis of piperazine, it was considered desirable to study the various aspects of this reaction in detail. Thus the present work was undertaken with the following objectives: (1)to screen a number of catalysts for the reaction, and (2) to study the kinetics of the reaction using the best catalyst. Experimental Section Preparation of Catalyst. The catalysts used for studying the vapor phase deamination of DETA were 7-A1203and 7-A1203impregnated with metal oxides. The procedure for the preparation of y-A1203catalyst was the same as used by Maciver et al. (1963). An aqueous solution of aluminum nitrate was slowly added to a solution of ammonium hydroxide with constant stirring. The resulting precipitate was immediately filtered, washed, and dried at 120 "C for several hours. Then it was crushed to small pieces and calcined at 500 OC for 24 h. The white calcined material was found to have an X-ray diffraction pattern characteristic of 7-A1203. The procedures for the preparation of other catalysts is briefly summarized in Table I. Experimental Setup. The experimental setup shown schematically in Figure 1 consisted of a feed pump, vaporizer, preheater, reactor, and product collection assemt NCL
Communication No. 3209. 0196-4305/85/ 1124-0525$0 1.50/0
bly. The reactor was an integral type reactor made of stainleas steel. It was immersed in a fluidizing bed of solids (bauxite) heated to the desired reaction temperature so as to ensure isothermal conditions in the reactor. The liquid reactant was fed to the vaporizer, where it was vaporized and carried to the preheater by the inert carrier gas (nitrogen). In the preheater the reactant in the form of vapor was heated to the reaction temperature and passed through the catalyst bed maintained at a constant temperature in the reactor. The product vapors coming out of the reactor were condensed and collected in icecooled glass traps. Identification and Analysis of Products. Several reactions take place simultaneously when DETA is deaminated on an alumina catalyst resulting in the formation of a number of products. All the products formed in the reaction were identified by use of a combination of gas chromotograph and mass spectrometer (AEI MS 3074 GC/MS). The mixture of products was resolved in the gas chromatograph and carried by an inert gas (argon) to the mass spectrometer. In the mass spectrometer, product molecules are fragmented into different ionic species which are separated by applying a magnetic field, and the mass spectra thus obtained are characteristic of the organic molecules. After the spectra of all the products are obtained, they are identified by matching the spectra with standard data reported in the Atlas of Mass Spectral Data (Stenhagen et ai., 1969). The analytical procedure and column used in the gas chromatograph were the same as those reported by Tornquist (1965). The chromatographic column was made out of an aluminum tubing of 4 mm i.d. and 2 m length. The adsorbent material was Chromosorb W impregnated with 3% KOH as carrier on which was applied 10% Carbowax 20 M. The polymer products formed in the reaction were estimated by direct weighing. A typical chromatogram is shown in Figure 2. It will be seen that a number of products are formed piperazine, ethylenediamine, pyrazine, alkyl pyrazines, triethylenediamine, and N-(0-aminoethy1)piperazine. Results and Discussion Influence of Mass Transfer. Experiments were conducted to determine conditions under which the resistance due to external film diffusion and pore diffusion would be negligible. The runs were carried out at constant W I F but at varying flow rates. At lower feed rates the conversion varies with the feed rate, and at higher feed rates it is not influenced by feed velocity. The region in which conversion is not influenced by feed rate is the 0 1985 American Chemical Society
526
Ind. Eng. Chem. Process Des. Dev., Vol. 24, No. 3, 1985
Table I. Procedure for the Preoaration of Different of Catalysts calcn tema "C
".
cat. DreDn - impregnating y-Al,O, with ammonium fluoride from solution containing appropriate amounts of fluorine and dryihg at 111 "C for 10 h 2. phcsphoric acid on y-A1203 soaking y-A1203in appropriate quantity of phosphoric acid and drying at 110 OC impregnating y-A120, with ammonium dichromate from solution and drying at 110 "C 3. chrom-y-A1203(5%) for 10 h 4. molybdena-y-A1203(5%) impregnating y-A1203with ammonium molybdate from solution of appropriate strength soaking y-A1203in appropriate quantity of nickel nitrate and drying at 110 "C 5. Ni0-y-A1203(5%) 6. zeolite commercial ZSM-5catalyst
no. cat. tvDe 1. fluorinated y-A1203(5%)
i
SILICA GEL TRAP
3 MANOMETER 4
FEED WLET
5 VAPORIZER 6 PREHEATER
400 450
450 450
W
1
2 CAPILLARY F L O W METER
450
OUTER HEATING JACKET BAUXITE IFluidimd Hollnp bed 1 TUBULAR REACTOR TMERMOWELL 11 CATALYST BED I 2 PRODUCT OUTLET 7 8 9 10
13 14
CYCLONE WATER CONDENSER
15 PRODUCT COLLECTOR 16
FEEDING PUMP
Figure 1. Experimental setup.
1 1
~
r
w
15
0
5 % PHOSPHORIC ACID ON f-A12 O3 5 % FLUORINATED Y - A I 2 0 3
'
f-Al2Oj
x
T
12
o
Li
z
0
N
5 % C r 2 0 3 ON Y-A1203 5 % N I O ON -(-AI203 5 % MOLYBDENUM OXIDE ON f - A l q 0 3 ZSM-5
a
0:
g 9 e
a IL 0
* t 6
i
t -
2
I
2
F U
W W
Figure 2. A typical chromatogram of reactant and products. 3
region free of external film diffusion. Thus in all kinetic experiments feed rates falling in this region were used. To eliminate the effect of pore diffusion, experiments were conducted with six different particle sizes (-20 +30, -30 +36, -36 +50, -50 +60, -60 +65, and -65 +80 B.S.S. mesh). This corresponded to average particle diameters in the range of 670-190 pm. It was observed that pore diffueion is negligible for particles with average diameters less than about 300 pm. Hence all experiments for studying this system were conducted using (-50 +60) mesh particles of average diameter 275 pm. Screening of Catalysts. In all, seven catalysts were used in this study. These catalysts can be classified into two groups: (1) yA1203impregnated with substances which are commonly used as catalysts for liquid phase
0
20
40
60
80
0
CONVERSION OF D E T A , %
Figure 3. Plot of selectivity for piperazine against conversion of DETA for different catalysts.
deamination, and (2) yAl,O, impregnated with acidic substances. The procedures for the preparation of these catalysts are summarized in Table I. Experiments were carried out by changing the time factor W / F at 380 "C.From the data collected selectivity plots were prepared and are shown in Figure 3. It is evident that the catalyst with acidic impregnation favors
Ind. Eng. Chem. Process Des. Dev., Vol. 24, No. 3, 1985 527
ETHYLENEDIAMINE
x
N-IP-AMINOETHYL)
0
P O L Y E T H Y L E N E POLYAMINE
s25-* VI
v
U
P
I-
E a
PIPERAZINE
P O L Y E T H Y L E N E POLYAMINE
PIPERAZINE ALKYL P Y R A Z I N E AMMONIA
20-v 0
k
n
p
TRIETHYLENE-
0
E
N-(B-AMlNOETHYLI
PIPERAZINE
15-
IA
0
z 0
vrK
10-
W
z 0 U
5
0
2
4
6
0
10
12
W / F , pm h r / m o l e
W / F, pm hr/ mole
Figure 4. Product distribution study at 380
OC.
the conversion of DETA to piperazine. Catalysts less acidic or basic favor the formation of other products. Therefore, yA1203treated with phosphoric acid was selected as the best catalyst from among those investigated and used for obtaining kinetic data. It will be noticed that the selectivity for piperazine does not exceed 20%. Fortunately, some of the other products formed are equally important, such as EDA, polyethylenepolyamines, TEDA, and N-(p-aminoethyl)piperazine. EDA is used in the preparation of fungicides, surfactants, softeners, and chelating agents. Polyethylene polyamines are used as a component of wet strength additives in the paper industry. N-@-Aminoethyl)piperazine is used in the preparation of photographic developers and of TEDA, which is used as a catalyst in the manufacture of polyurethanes. It would therefore seem desirable to use the vapor phase method for this reaction where outlets can be found for the coproducts as well. If, on the other hand, piperazine is the main product desired, then the liquid phase process would appear to be preferable. No catalyst is available at this time which would give a much higher selectivity for piperazine than that reported in this paper. A Plausible Reaction Network. In order to gain a clear understanding of the reaction it is necessary to study product distribution as a function of W / F and temperature. For this purpose experiments were carried out on y-A1203by varying the time factor (W/F)at two different temperatures (360and 380 "C). From the data collected, plots of conversion (to any product) vs. W / F and selectivity (for piperazine) vs. conversion were prepared and are presented in Figures 4,5, and 6. From Figures 4 and 5 it is evident that the profiles of some of the products such as piperazine and EDA go through maxima and some products such as pyrazine and ppazine derivatives do not exhibit maxima. This is because of the occurrence of primary and secondary reactions. At low conversion levels of the primary reactant, the secondary reactions are relatively unimportant. Secondary reactions, however, become significant as the conversion of the primary reactant is raised to higher levels. The transformation of DETA occurs mainly in two ways: (1) deamination and (2) dehydrogenation. There are two types of deamination: linear deamination which gives
Figure 5. Product distribution study at 360 "C. 5 o r
I
I
I
I
I
I
V 0
I
I
I
1
TRIETHYLENEDIAMINE PYRAZINE
40
CONVERSION
OF D E T A ,
*/e
Figure 6. Plot of selectivity for different products against conversion of DETA at 380 O C .
polyethylene polyamines, and deaminocyclization leading to the cyclic product piperazine. The dehydrogenation products are pyrazine and pyrazine derivatives. The deamination processes predominate at lower temperatures, while dehydrogenation reactions prevail a t higher temperature (Yurel et al., 1974). In order to arrive at a probable reaction network for this complex scheme it would be instructive to examine the effects of each of the reaction products on the overall conversion. Thus a number of experiments were carried out using reactant mixed with different products (to the extent of 5%). The results obtained are presented in Figure 7. It will be seen from the figure that except for NH3 no other product influences the conversion of reactant. For identical operating conditions the runs with NH3 in the feed of DETA always showed greater conversion than those without admixture of NHg. This observation suggests two possibilities: (1) NH3 catalyzes the reaction,
Ind. Eng. Chem. Process Des. Dev., Vol. 24, No. 3, 1985
528
Table 11. Concentrations (M)of Products and Reactant for Various Values of W / F at 330 OC WIF, no. (g h)/mol CC Cll CE CI CA CB 1. 0.365 1.348E-02" 8.510E-05 2.180E-05 8.650E-05 2.310E-05 4.310345 1.3753-07 2. 0.584 1.333E-02 1.3453-04 3.45OE-05 1.607E-04 3.7103-05 4.6003-05 3.492E-07 3. 0.730 1.3233-02 1.668E-04 4.28oE-05 2.106E-04 4.640345 4.63OE-05 5.4273-07 4. 1.460 1.2743-02 3.198E--04 8.000E-05 4.5273-04 9.3803-05 4.7 1OE-05 2.100E-06 5. 3.650 1.137342 7.047E-04 1.3433-04 1.0983-03 2.404E-04 5.140345 1.210E-05 6. 1.146E-03 9.820E-05 1.962E-03 4.961E-04 5.470E-05 4.2403-05 7.300 9.390E-03 7. 10.950 7.809E-03 1.4123-03 5.890E-05 2.626343 7.6133-04 5.4103-05 8.380345 6.5353-03 14.600 8. 1.563343 4.1403-05 3.146B-03 1.0333-03 5.510E-05 1.319E-04
CP.
CH
4.066E-08 1.035E-07 1.610E-07 6.222347 3.100E-06 7.7003-06 1.05OE-05 1.236E-04
6.449E-08 3.1863-07 6.621347 5.700346 7.2003-05 2.933E-04 4.997E-04 6.678344
. _ _
"This signifies 1.348 X lo-*, etc., throughout.
'-
=0
7-
0.61
!I ,I\
E
l
//
i 1
R
ED4 ALKYL
HIN-ICHp-CH2-NHl"-CH~-CH~-Nn~
-l 0.4
PYRAZINE
t NH,
POLYETHYLENEPOLYAMINE~
0
Figure 8. Plausible reaction network
W / F , gm h r f m o l e
Figure 7. Effect of presence of product in the reactant feed.
and (2) NH3 combines directly with DETA to give the products. When we combine this observed increase in conversion by addition of NH3 with another important observation, viz., the proportion of EDA is always very high in the product, it is a reasonable conclusion that one of the main reactions in the network is the direct amination of DETA to EDA. It is clear, therefore, that the increase in the total conversion due to addition of NH3 is because of the deamination reaction leading to EDA. We shall now put together all the observations made on the product distribution: (1) maxima are observed at certain conditions in the concentrations of piperazine, EDA, and N-(8-aminoethyl)piperazine;(2) the conversion of primary reactant is enhanced by the addition of NH,; and (3) for the conditions studied, the quantities of TEDA, pyrazine, and pyrazine derivatives formed are quite small with no evidence of maxima. From the observations listed above, the reaction network suggested in Figure 8 appears reasonable. It accounts for the fact that EDA is formed in sufficient quantity and also undergoes further reaction to pyrazine derivatives. This explains the appearance of a maximum in the concentration of EDA. Maxima in piperazine and N-(p-aminoethy1)piperazine clearly suggest that these are also intermediate products, leading respectively to the fmal products TEDA and pyrazine. The formation of polyethylenepolyamines can be explained in various ways. However, purely for the sake of simplicity and since the quantity polyethylenepolyamines is small, it may be assumed that they are directly formed from DETA.
The formation of EDA, piperazine, and N-@-aminoethy1)piperazine as intermediates in the overall reaction scheme, and which is the basis for the proposed reaction network, can be confirmed by carrying out the reaction under identical conditions in integral and fully stirred reactors. Clearly, operating under fully mixed conditions would lead to higher concentrations of intermediates. A number of runs were carried out in the integral reactor described earlier and also in a Berty reactor, the latter under fully mixed conditions. The Berty reactor (Berty, 1974) is an internal recycle reactor which ensures operation at fully mixed conditions in the absence of mass transfer effects. The conversion-time profile for the principal products under the two extreme conditions are shown in Figure 9. It will be noticed that there is an enhancement in the reaction under fully mixed conditions. This can be taken as additional evidence for the reaction scheme suggested. Kinetic Analysis. Runs were carried out at four different temperatures (330, 350, 360, and 380 OC) by recording the product distribution at different values of space time (W/F). The data collected at each temperature were used to calculate the concentrations of the products and reactant at different W / F and are presented in Tables 11, 111, IV, and V. These data points were fitted to a fourth-order polynomial of the type
X = a ( W / F ) + b ( W / n 2+ c ( W / n 3+ d ( W / n 4
(1)
Initially data points were fitted with different order polynomials. With fourth and higher orders, polynomials variances were very small and almost negligible. Hence a fourth-order polynomial was used for data fitting. From regression analysis the constants a, b, c , and d were determined. Equation l when differentiated leads to dX/d(W/F) = a
+ 2b(W/F) + 3 c ( W / n 2+ 4 d ( W / n 3 (2)
The left-hand side of eq 2 is the reaction rate. Hence by using the constants determined above, the rates at dif-
Ind. Eng. Chem. Process Des. Dev., Vol. 24, No. 3, 1985 529
Table 111. Concentrations (M) of Products and Reactant for Various Values of W / F at 350 OC
WIF,
CA
CB
CC
CD
CE
CI
CF
CG
CH
1.293E-02 1.2583-02 1.128E-02 9.4843-03 8.2523-03 7.195343 5.877E-03 4.475343
1.448E-04 2.531344 6.260344 1.048E-03 1.277E-03 1.4373-03 1.583E-03 1.662E-03
4.0803-05 7.130E-05 1.559B-04 1.647E-04 1.265E-04 9.260E-05 6.3003-05 4.470E-05
1.7743-04 3.4533-04 9.6713-04 1.7503-03 2.2493-03 2.6603-03 3.1483-03 3.6233-03
4.180E-05 7.620E-05 2.221E-04 4.708E-04 6.831E-04 9.0413-04 1.248343 1.7213-03
5.480E-05 5.580E-05 5.950345 6.640E-05 6.8603-05 6.961344 7.210E-05 7.940E-05
2.642E-07 8.191E-07 5.800E-06 2.080345 3.720E-05 5.6403-05 8.850345 1.344344
8.523E-08 2.7173-07 1.800E-06 5.300E-06 7.700E-06 9.500346 1.140E-05 1.3203-05
2.9703-07 1.989346 3.960E-05 2.042344 3.6843-04 5.181344 7.040344 9.046344
Table IV. Concentrations (M) of Products and Reactant for Various Values of W / F at 360 OC WIF, no. (g hjlmol CA CB CC CD CE CI CF 1. 1.2623-02 1.857E-04 5.490E-05 2.3553-04 5.570E-05 6.0303-05 3.000E-07 0.380 2. 1.234E-02 2.720E-04 8.030E-05 3.752E-04 8.470E-05 6.090E-05 7.000E-07 0.560 3. 1.206E-02 3.541E-04 1.037E-04 5.101E-04 1.144E-04 6.140E-05 1.300E-06 0.760 4. 1.005E-02 8.805E-04 1.967E-04 1.430E-03 3.7543-04 6.960E-05 1.060E-05 2.280 5. 8.3453-03 1.223343 1.667E-04 2.127E-03 6.676E-04 7.610E-05 2.630345 3.800 6. 5.7593-03 1.5653-03 8.240E-05 3.074E-03 1.309343 8.260345 6.810E-05 6.840 7. 4.343E-03 1.648E-03 5.690E-05 3.526E-03 1.8213-03 9.180B-05 1.037E-04 9.120 11.400 8. 3.213E-03 1.646E-03 4.4503-05 3.8333-03 2.344E-03 1.073E-04 1.402E-04
CG
CH
1.000E-07 2.000E-07 4.000E-07 3.3003-06 6.5003-06 1.070E-05 1.2503-05 1.38OE-05
6.000E-07 2.200E-06 5.300E-06 1.090E-04 3.123E-04 6.874344 8.924344 1.060E-03
Table V. Concentrations (M) of Products and Reactant for Various Values of W / F at 380 O C WIF. no. (g h)/mol Ca CP Cll C, C, CA CF 1. 0.395 1.1763-02 2.913E-04 9.420E-05 4.069E-04 9.680E-05 7.1203-05 5.000E-07 2. 0.790 1.088E-02 5.381E-04 1.7303-04 8.274E-04 2.061E-04 7.4003-05 2.2003-06 9.293E-03 9.210E-04 2.4093-04 1.5263-03 4.5623-04 8.320E-05 8.100E-06 3. 1.580 4. 2.370 7.898E-03 1.1873-03 2.308E-04 2.073E-03 7.3853-04 9.2403-05 1.6603-05 5. 3.950 5.641E-03 1.480E-03 1.455E-04 2.8433-03 1.3663-03 1.061E-04 3.830E-05 6. 5.925 3.6052-03 1.588343 8.290E-05 3.4023-03 2.218E-03 1.297344 6.920345 7. 6.715 2.9603-03 1.585343 7.080E-05 3.541E-03 2.5683-03 1.450E-04 8.1903-05
CG
CH
2.000E-07 8.000E-07 2.900E-06 5.2OOE-06 8.800E-06 1.140E-05 1.220E-05
2.100E-06 1.7603-05 1.105E-04 2.669E-04 5.999E-04 9.070E-04 1.002E-03
no. 1. 2. 3. 4. 5. 6. 7. 8.
(g h)/mol 0.375 0.675 1.875 3.750 5.530 6.750 9.OOO 12.000
Table VI. Rate Constants (h-*)for the Nine Reaction Steps at Four Different Temperatures
T , "C 330 350 360 380
kl 1.2645 2.2414 2.9439 4.9530
k2 0.3213 0.6246 0.8572 1.5683
kS 563.23 830.52 999.28 1422.26
k4 0.3378 0.6230 0.8338 1.4541
ferent W / F were calculated. From the proposed reaction network, rate equations (in terms of formation/disappearance of each component) can be written as -dA/dt = k1CA2
k&A
~ B C A C+Ik4CA
dB/dt = k l c A 2 - ~ ~ C B-CkI7 C ~
+
dC/dt = k z C ~ ~ ~ C B-Ck8Cc I - kgCcCD
(3)
(4) (5)
dD/dt = ~ ~ C A-CkgcccD I - k & ~ +~ ~ C B C I(6)
+k6C~ = klCA2 + k z C ~+ k d c ~ + k 6 C ~- ~ B C A C+I dE/dt = k,cA
dl/dt
~ . T CB~
(7)
~ C B+ C kgcCcD I (8)
dF/dt = k7CB
(9)
dG/dt = k8Cc
(10)
d H / d t = kgCcCD
(11)
In these equations the rates are known at different concentrtions and only the rate constants are to be evaluated. The rates are linear functions of rate constants but not the concentrations. From these equations the matrix can be formulated for rates and concentrations. The rate constant matrix which gives the values of rate constants can be evaluated in the following way. First the inverse
k5
k6
126.02 149.88 162.78 190.56
1.0435 2.5390 3.8777 9.7000
k7 0.6419 0.7034 0.7347 0.7985
k8
k9
0.7428 0.8274 0.8710 0.9608
325.65 374.62 400.48 454.86
Table VII. Activation Energies for the Nine Reaction Steps act. act. energy, cal energy, cal E1 21364.09 f 0.79 E6 33184.41 f 1.13 E2 24805.98 h 1.64 El 3415.63 i 1.47 E3 14494.41 f 1.29 Ea 4027.72 f 1.81 E4 22841.10 h 1.10 E9 5228.27 f 1.37 E5 6471.69 f 1.31 Table VIII. Preexponential Factors in the Arrhenius Equations for the Nine Reaction Steps ko1 7.01 x 107 ko6 1.11 x 10'2 kO2 3.15 X lo8 k01 11.10 k03 1.01 x 108 ko8 21.39 k04 6.41 X lo1 kos 2.55 x 104 kos 2.79 x 104
of the product of transpose of the concentration matrix and concentration matrix was found. The new matrix obtained was multiplied by the product of the transpose of concentration matrix and rate matrix. This regression method was repeated to obtain rate constants at other temperatures. From the calculated rate constants at different temperatures, Arrhenius plots of In k vs. 1 / T were prepared. These are shown in Figure 10. It may be seen from this figure that for each reaction step the rate constant increases with temperature, which may be regarded as an indirect verification of the proposed complex reaction
Ind. Eng. Chem. Process Des. Dev., Vol. 24, No. 3, 1985
530 30 -
s VI
k
I
I
25-
*
SERTY
+
I N T R E G A L REACTOR
/*-4 I
I
I
REACTOR
3/*
-I
1 PIPERAZINE K
2 N-
(
p-AMINOETHYL
)
1
PIPERAZINE
3 ETHYLENEDIAMINE
w
/*
15 0
i; z
zVI
K
w
>
8 z
5
!
-*-*-
;+O0
I
I
I
3
4
5
6
W/F, g m h r / m o l e
Figure 9. Comparison of DETA conversion to intermediate producta in Berty and integral reactors. 7.51
I
-a
I
I
I
I
I
-*-\-
in Tables VI, VII, and VIII. It may be seen from Table VI1 that for the first six reactions the values of activation energy are in the kinetic regime. For the remaining three reactions, the rather low values of activation energy (30W5000 cal) do not clearly indicate kinetic control. If external mass transfer were controlling, one would expect activation energies in the region 2000 cal/g-mol. It therefore seems possible that pore diffusional resistance may be influencing the reaction to some extent. However, since the extent of reaction in each of these three cases was very small, no additional experiments were carried out to elucidate this point further.
Nomenclature A = DETA B = N-(0-aminoethy1)piperazine C = piperazine D = EDA E = polyethylenepolyamines F = TEDA G = pyrazine H = alkyl pyrazines I = NH3 R = gas constant T = temperature, K C, = concentration of DETA, M C, = concentration of N-(b aminoethyl)piperazine, M C, = concentration of piperazine, M CD = concentration of EDA, M CE = concentration of polyethylenepolyamines, M X = gas phase concentration, M CF = concentration of TEDA, M CH = concentration of pyrazine, M CI = concentration of NH3, M W / F = time factor, (g h)/mol a, b, c, d = constants in eq 1 kl, kz, k3, k4,kg, kg, k7, ks, k9 = rate constants for the reaction step 1 to 9, h-' El, Ez, E 3 , E4, Eg, E6, E7, E8 E9 = activation energies for the reaction step 1 to 9,cal ko!, koz, k03, k04, F o g , kw,kp,, koa,kos = preexponential factor in the Arrhenius equation for the reaction step 1 to 9, h-' Registry No. A1&,,1344-28-1; NiO, 1313-99-1; DETA, 11140-0;fluoride, 16984-48-8; phosphoric acid, 7664-38-2; chromium, 7440-47-3; molybdena, 1313-27-5. Literature Cited
1 T ,
'K
-1
Figure 10. Arrhenius plots for the nine reaction steps.
network. Activation energies for all reaction steps were calculated from the slopes. Once the activation energy is determined it be used to calculateko by the familiar relationship
k = k,.@/RT (12) The values of k, and E for all the reactions are presented
Anderson, A. A; Yurel, S. P.; Shymanska, M. V. Chem. Mleterocycl. Compd. 1867, 2, 346. Berty, J. M. Chem. Eng. Rogr. 1874, 70(5), 78. Maclver, D. S.; Tobin, M. H.; Barth, I?. T. J . Catal. 1009, 2, 485. Pfann, M. F.; Greenwich, Dixon, J. K. US. Patent 2 454 404, Nov 23, 1942. Stenhagen, S.; Abrahamsaon, S.; Mclafferty, F. W. "Atlas of Mass Spectral Data", Vol. 1 and 2; Wlley-Interscience: New York, 1969. Tomqulst, J. Acta Chem. S c a d . 1065, 19, 777. YWd, s. P.; Anderson, A. A.; Plnka, Y. A.; Shymanska, M. V. Bull. A a d . Sci. Lat. SSR 1974, 6 , 891.
Received for review February 3, 1983 Revised manuscript received May 21, 1984 Accepted June 1, 1984
