538
Ind. Eng. Chem. Process Des. Dev. 1981, 20, 538-540
Kunll, D.; Levenspiel, 0. Ind. Eng. Chem. Fundam. 1966, 7, 446-452. Leva, M.; chnmner,M. Chem. Eng. Reg. 1952, 48(6). 307-313. Lewls. W. K.; GHlhd, E. R.; Gkouard, M. Chem. Eng. Rag. Symp. Ser. 1962, 58, NO. 38, 87-97. Maraheck, R. M.; Gomezplata, A. AICMEJ. 1985. 11(11), 167-173. May, W. G. them. Eng. Prog. 1919, 55(12), 49-58. Merry, J.. D.; DaVMson, J. F. Trans. Inst. Chem. Eng. 1973, 51, 361-368. Mlyauchl, T.; hooks, S. Int. Chem. fng.1969, 9(4), 713-721. Ohkl, K.; MI, T. "Particle Veloclty In Fluidized Beds", "Fluidlzatfon Techndogy"; Vd. I, Roceedlngs, Internatlonal Fluldlzation Conference, Peclflc &ove, 1975. Potter, 0.E. " k i n g " In "Fkddizatfon"; Davidson, J. F.; Harrison, D., Ed.; Academic Press: New York, 1971. Rowe, P. N.; I%*, 6. A.; Cheney, A. G.; Henwood, 0.A.; Lyall, E. Trans Inst. Chem. Eng. 1965, 43,T271-T286. Singer, E.; Tood, D. E.; Gulnn, V. P. I d . €4.Chem. 1957, 49(1), 11-19.
Tailby, S. R.; Cocquerel, M. A. T. Trans. Inst. Chem. Eng. 1961, 39, 195-201. Talmor, E.; Benenatl, R. F. A I C K J . 1963, 9(4), 536-570. van Deemeter. J. J. Roc. Int. Symp. Fluid. 1967. Welner, S. C.; Golan, L. P.; Chenington, D. C. "SolldsMlxlng and FluldirauMl Characteristics In a Tube Filled Bed"; Intersoc. Energy Convers. Eng. Conference, 13th. San Diego, 1978. Wen, C. Y.; Fan, L. T. "Models for Flow Systems and Chemical Reactors"; Marcel Dekker: New York, 1978. Werther, T. Powder Technol. 1976, 75, 155-167. Whltehead, A. E.; GartsMe, G.; Dent. D. C. Powder Techno/. 1976, 14, 61-70.
Received for review July 9, 1980 Accepted March 31,1981
Effects of Water Vapor on the Catalytic Hydrodenitrogenation of Quinoline Charles N. Satterfleld" and Denise L. Carter Department of Chemical Engineering, Massachusetts Institute of Technology, C a m b m , Massachusetts 02139
At 7 MPa total pressure, 13.3 kPa partial pressure of water vapor moderately accelerates certain reactions in the catalytic hydrodenitrogenation(HDN) of quinoline on a NIMo/A1,03 catalyst and moderately inhibits others, so there is little net effect on the overall HDN rate at 330 and 375 OC and a slight lnhlblting effect at 420 OC. Water v a p slightly increases the degree of saturation of hydrocarbon products at 375 O C and slightly decreases it at 420 C. The marked enhancing effect of HzS on the HDN reaction rate is not signiflcantly affected by the presence of 13.3 kPa of water vapor.
In a series of previous papers we have reported on studies of the reaction network of the catalytic hydrodenitrogenation (HDN) of quinoline, made in a continuous-flow microreactor on a presulfided commercial NiMo/A1203 catalyst. These include determination of equilibrium constants for the reactions that are reversible (Satterfield et al., 1978; Cocchetto and Satterfield, 1981) and the development of a kinetic model for the reaction (Satterfield and Cocchetto, 1981;Satterfield and Giiltekin, 1981). Quinoline is a good model compound for the 6membered ring heterocyclic nitrogen compounds found in the middle distillate range of fuels derived from oil shale, coal, and low grade petroleum. Sulfur compounds are also invariably present and we showed in the last paper that H a formed by hydrodesulfurizationhad a slight inhibiting effect on the hydrogenation reactions in quinoline HDN but a marked enhancing effect on hydrocracking reactions, so the net effect was an enhancement of the overall rate of nitrogen removal. Fuels derived from coal may contain significant quantities of oxygenated species such as phenols and furans, in addition to sulfur and nitrogen compounds, and during hydrotreating these will be converted to hydrocarbons and water. The purpose of the present study was to explore some of the effects of water vapor on the HDN of quinoline, in analogous fashion to our earlier study of the effect of HZS. Experimental Section The apparatus and experimental procedures were the same as those used previously. The same charge of commercial NiMo/A1203 catalyst used by Satterfield and Gultekin was retained in the reactor and was resulfided 0196-4305/81/1120-0538$01.25/0
between runs, as previously. Studies were made at temperatures of 330,350,375, and 420 "C, at 7.0 MPa total pressure, quinoline partial pressure of 13.3 kPa, water vapor partial pressure of 13.3 kPa, and space-times, W I F Q ,of~ 83.3 to 667 h g of cat./ g-mol of quinoline. Most of the studies were a t 375 O C . Some studies were also made with each of two reaction intermediates, Bz-tetrahydroquinoline (BzTHQ) or with o-propylaniline (OPA), in each case at 13.3 kPa initial partial pressure. The water was fed in the form of a solution with the heterocycliccompound. In the desired ratio it was completely miscible with quinoline or Bz-tetrahydroquinoline but was only partially miscible with opropylaniline (OPA) and in those runs with OPA the partial pressure of water vapor was somewhat less than 13.3 kPa. Most runs began at intermediate space times, then proceeded to lower flow rates (higher space-times) and then to the highest flow rates (shortest space-times). About 2 h was required to come to steady state. For the first 1to 1.5 h after initial startup some HzS from the resulfiding procedure was desorbed, as detected by lead acetate paper. This was also observed in the previous study of HDN of quinoline in the absence of HzS. The catalyst was resulfided after each run, as previously, but H2S was not introduced during the run, except in one case. Results and Discussion The catalyst had previously been on stream for about 700 h for HDN studies in the presence of H2S. Figures 1, 2, and 3 compare the effect of the presence of HzS,of HzO, or both, on the overall percent hydrodenitrogenation of quinoline as a function of space-time at a representative 0 1981 American Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 20, No. 3, 1981 539
f
*O
i
I
100
7
I
I
600
700
I
I
200
300
400
500
.hr g cot / g -mole
W
0
Figure 1. Hydrodenitrogenation of quinoline, 7 MPa, 13.3 kPa of quinoline, T = 330 O C . 100
90
I
I
I
I
I
t W/Go
. h r 9 - c a t /g-mol
0
Figure 3. Hydrodenitrogenationof quinoline, 7 MPa, 13.3 kPa of quinoline, T = 420 "C. (DOPA)
(ai
(pO)
(PYTHOI
t
NH3
-2H2
0
100
200
W IFao
300
hr 9-cat
400 500 /g - m o l 0.
600
700
Figure 2. Hydrodenitrogenation of quinoline, 7 MPa, 13.3 kPa of quinoline, T = 375 "C.
set of conditions, 7 MPa and 330,375, or 420 O C . Whereas H2S has a significant accelerating effect at all temperatures, water vapor had little effect on the overall HDN rate a t 330 and 375 "C and some inhibiting effect at 420 "C. However, it appeared to moderately accelerate certain reactions and inhibit others in the overall reaction network, as will be shown. In the presence of both H2S and H20, studied a t 375 "C only, there is a slight inhibition compared to the presence of H2S alone. During the studies reported here, the catalyst was on stream for about 150 h. Three reproducibility runs at the above set of conditions during this period showed no significant variation in catalyst activity with time on stream. Kinetic Analysis. The products were the same as those observed previously but the effect of space-time on product distribution at a fixed temperature and pressure was somewhat different, especially at long space-times. The reaction network as developed in our previous study of quinoline HDN in the presence of H2S is shown in Figure 4. This identifies the five reactions discussed below and lists the acronyms used for the various species that may be present. The kinetic analysis here utilized the same procedure as that used previously. The conversion of Q to PyTHQ goes rapidly to equilibrium and the reaction between BzTHQ and DHQ appeared to be essentially in equilibrium, as was found in the presence of H2S. The individual reactions were again well formulated in terms of a Langmuir-Hinshelwood type of kinetic expression which incorporated adsorption terms for NH3, KW; for secondary amines as a group (PyTHQ and DHQ),
( PCH
0
quinotina
PyTHO
PY ( O r 1.2,3,4 1 - t o t r a h y d r O q U , n 01 #me
BzlHO
62
DHQ
dQC0
OPA PCHA
I
( o r 5.6.7.81- t a t r o h y d r o q u ~ n o i l n e
h y d r oqu In 01,n e 0-propylonilina
PB
PrODylCyCIOhary10m~na propylbanzana
PC t i E
PrOPYIcyClOhmana
PCH
P~ODYlCYClOhQ~On~
DOPA
dihydro
0-propyioniljne
Figure 4. Quinoline hydrodenitrogenationnetwork.
KsA; and for aromatic amines as a group (quinoline, BzTHQ, and OPA), KAA. As before, the network was divided into three regimes and plug flow equations were applied to determine the rate constants in one regime and an adaptation of the Himmelblau-Jones-Bischoff method (1967) was used to determine rate constants in two other regimes. Studies with o-propylaniline alone and with BzTHQ alone were also used, as before, to help generate the values of some of the constants. The criteria for quality of fit included linearity of Arrhenius plots, good agreement between rate constants calculated by more than one method, and close agreement of predicted product distributions with the original data. The detailed raw data and procedures used for the kinetic analysis are given by Carter (1980). The best value of the ratio KNH8/KAAhere was 0.15, slightly less than the value of 0.25 previously calculated in the absence of water. The best value of the ratio of KsA/KAA was found to be 6, the same as that in the absence of water.
Ind. Eng. Chem. Process Des. Dev. 1981, 20, 540-545
540
It is desirable industrially to carry out hydrodenitrogenation with as little consumption of hydrogen as possible. Saturation of the N-containing ring and subsequent hydrocracking to propyl benzene and NH3 represents the absolute minimum on present-day catalysts. In fact, however, most of the hydrocarbon product is saturated. Table I shows the effect of presence of water vapor and/or H2S on the PCH/PBz ratio at 375 "C and at 420 "C, for selected % conversions at which comparisons could be made. At 375 "C, the ratio is slightly increased by water vapor alone but is markedly increased by H2S. A mixture of H2S and H20 vapor behaves like H2S alone. Although H2Saccelerates the overall HDN rate, it is seen that in its presence the hydrocarbon product is on average more highly saturated. A t 420 "C the PCH/PBz ratio is decreased below that at 375 "C for each case. H2S slightly increases the ratio and water vapor slightly reduces it. Although water vapor reduces the HDN rate at 420 "C, in its presence the hydrocarbon product is on average less highly saturated. The only other study of the effect of water vapor on HDN of a heterocyclic nitrogen compound of which we are aware is a brief report in the thesis of Goudriaan (1974) of the HDN of pyridine over a CoMo catalyst in either the "oxidic" form or in the presence of H2S. With the oxidic catalyst at 250 "C water vapor caused a marked decrease in ring hydrogenation activity (rate of formation of piperidine), but the rate of hydrogenolysis was too low to observe an effect of water vapor. With the sulfided catalyst at 300 "C and in the presence of 2 bar (200 P a ) H a , water vapor did not affect ring hydrogenation activity. Hydrogenolysis activity was likewise not affected by water vapor up to 1 bar (100 kPa) but' was enhanced at higher water vapor pressures. Literature Cited
Table I. Effects of Water Vapor and Hydrogen Sulfide on Ratio of Propyl Cyclohexane t o Propyl Benzenea quinoline quinoline quinoline alone + H,O + H,S 375"C, 23% HDN 375 'C, 47% HDN 420"C, 50% HDN 4 2 0 OC, 94% HDN
quinoline + H,O andH,S
5.4
6.4
17
18
4.2
5.7
19
19
3.1
2.3
4.1
3.0
2.7
3.5
--
a P = 7 MPa;p.p.g= 1 3 . 3 kPa;p.p.H,o= 13.3 kPa; p . p . ~ , 1~3=. 3 kPa.
A comparison of the rate constants in the presence of water at 375 "C to those in its absence (Satterfield and Cocchetto, 1980) yielded the following results R1 = 0.000164/0.00020 = 0.82
R2 = 0.0044/0.0052 = 0.84 R3
= 0.0185/0.0238 = 0.78
R4 = 0.0020/0.00172 = 1.16 R, = 0.0013/0.00133 = 0.98 where
Ri =
(ki)~HW=13.3 E a
(ki)P~=o.o
and the subscript i refers to the reaction as noted in Figure 4. Water vapor seems to have a moderate inhibiting effect on reactions 1and 2 but essentially none on reaction 7. It seems to affect the two hydrogenation reactions in opposite ways, accelerating 4 and inhibiting 3. However, the precision with which K4 can be determined is somewhat less than that for the other constants (Satterfield and Gultekin, 1981) so this may be an artifact of the model. None of the effects are major at this temperature and partial pressure, indicating that water vapor is not strongly adsorbed on a sulfided catalyst at these conditions. Overall, water vapor slightly enhanced the reaction path PyTHQ DHQ PCH in contrast to PyTHQ OPA PB, and consequently the ratio PCH/PB in the final products was moderately greater (Table I).
Carter, D. L. M.S. thesis, M.I.T., Cambridge, MA, 1980. Cocchetto, J. F.; Satterfleld, C. N. Ind. Eng. Chem. Process Des. Dev. 1981, 20, 49. Goudriaan, F. Thesis, Twente Universlty of Technology, Enschede, The Netherlands, 1974. Himmelbhu, P. M.; Jones, C. R.; Bischoff, K. B. Ind. fng. Chem. Fundem. 1987, 6, 539. Satterfbld, C. N.; Cocchetto, J. F. Ind. Eng. Chem. Process Des. Dev. 1981, 20, 53. Satterfiild, C. N.; Gbkekin, S. Ind. fng. Chem. Process Des. Dev. 1981, 20. 62. Satterfbld, C. N.; Modell, M.; Hies, R. A.; Declerck, C. J. Ind. fng. Chem. Process Des. Dev. 1978, 17, 141.
- - - -
Received for review August 25, 1980 Accepted April 6,1981
Heat Transfer Coefficient in Bubble Columns Haruo Hlktta,' Satoru Asal, Hlroshl Klkukawa, Toshlakl Zalke, and Masahlko Ohue Depament of Chemical Engineering, University of Osaka Prefecture, Sakai, Osaka 59 1, Japan
Experimental data on the heat transfer between the d u m n wall and the gas-liquid dispersions in the bubble column with a single nozzle gas sparger were obtained by using air and various liquids. A new dimensionless correlation for the heat transfer coefficient was presented and shown to correlate the experimental data with an average deviation at 3.9%.
Introduction Bubble columns are widely used in the chemical industry as absorbers, fermenters, and gas-liquid reactors. In order 0196-4305/81/1120-0540$01.25/0
to attain the required liquid temperature and its subsequent control, heat must be removed or supplied. Thus, information on heat transfer coefficients h, between the 0
1981 American Chemical Society
