250
Ind. Eng. Chem. Process Des. Dev. 1980, 19, 250-257
Acknowledgment
Azer, N. Z., Fan, L. T., Lin, S.T., "Proceedings of the 1976 Heat Transfer and Fluid Mechanics Institute", p 512,Stanford University Press, Stanford, Calif.,
This work was supported by the Engineering Experiment Station, Kansas State University. The Kenics static mixer elements employed in this work were supplied by Dr. S. J. Chen of Kenics Corporation.
Bergles, A. E., ASHRAE Trans., 82, 891 (1976). Chen, S.J., Cost Eng., 17,8 (1972). Fan, L. T., Lin, S.T., Azer, N. 2.. Left. Heat Mass Transfer, 4,425 (1977). Genetti, W. E., Priebe, S.J., "Heat Transfer with a Static Mixer", presented at the 4th Joint Meeting of AIChE and CHChE, Vancouver, 1973. Lopina, R. F., Bergles, A. E., J . Heat Transfer, 95,281-283 (1973). Marner, W. J., Bergles, A. E., "Augmentation of Tubside Lamlnar Flow Heat Transfer by Means of Twisted Tape Inserts, Static Mixer Inserts, and Internally Finned Tubes", 6th Int. Heat Transfer Conference, Toronto, Canada, pp 583-588, Aug 7-11, 1978. Ornatshiy, A. P., Chemobay, V. A., Vasilyev. A. F., Perfov. S.V., Heat Transfer Sov. Res., 5 , 7 (1973). Rohsenow, W. M.. "Boiling", in "Handbook of Heat Transfer", W. M. Rohsenow and J. P. Hartnett, Ed., Section 13,pp 13-1-13-3,McGraw-Hill, New York,
Nomenclature
AP = pressure drop, N/m2 Q = heat transfer rate, W
QIA = heat flux, W/m2 'il; = average temperature of refrigerant-113, "C Td = avTrage-inside wall temperature of heater tube, "C AT& = Td - T f
Literature Cited
1976.
1973. Sununu, J. H., "Heat Transfer with Static Mixer Systems", Kenics Co. Technical Report NO. 1002 (1970). Sununu, J. H., "Heat Transfer and Pressure Drop Characteristics of a Static In-Line Mixer", Kenics Co. Report, 1971.
Received f o r review March 5, 1979 Accepted December 14, 1979
Alexander, L. G., Hoffman, H. W., "Performance Characteristics of Corrugated Tubes for Vertical Tube Evaporators", A.S.M.E. Paper 71-HT-30(1971).
The Kinetics of Porphyrin Hydrodemetallation. 1. Nickel Compounds Chl-Wen Hung and James Wel" Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetfs 02 139
The kinetics of hydrodemetallation (HDM) of nickel etioporphyrin (I) (Ni-Etio) and nickel tetraphenylporphine (Ni-TPP) have been studied in batch autoclave experiments, with white oil as solvent and Co0,-Mo03/A1203 as catalyst without presulfiding. The effects of hydrogen pressure up to 12 500 kPa and temperature between 287 and 357 OC were studied. Up to 90% nickel removal, the data can be described by fractional order kinetics. The activation energy is from 27 to 34 kcal/g-mol, and the pressure dependence on hydrogen is from 1.5 to 2.2 order. There is no diffusion effect. The rates with clean oil and model compounds are at least 100 times faster than previous work with residual oil and presulfided catalysts.
Introduction Due to the shortage of crude oil supply, there has been an increase in demand for upgrading residual oils in the past few years. However, during the upgrading processes, trace amounts of metal compounds in the residual oils, chiefly vanadium and nickel, will poison the hydrodesulfurization and cracking catalysts through hydrodemetallation reaction (HDM). During oil combustion the oxides of nickel and vanadium formed tend to erode turbine blades and furnace linings (Nelson, 1976,1977; Edison et al., 1976). A better understanding of the hydrodemetallation reaction and the laws of metal deposition would lead to better designs of catalysts and reactors, and to longer economic life of the catalyst. Although the importance of HDM has been recognized in recent years, there has been little scientific work published. First-order HDM kinetics was observed by Chang and Silvestri (1974, 1976) over manganese nodules and by Riley (1978) over Co0-Mo03/A1203 catalyst. Inoguchi and co-workers (1971) found that the kinetics can be explained equally well by either first-order or second-order kinetics. The recent study of Oleck and Sherry (1977) represented the data by second-order kinetics; however, they mentioned that if the metal complexes in residual oils are divided into two groups, each follows first-order kinetics but with 0196-4305/80/1119-0250$01.00/0
different rate constant, then the conversion vs. time data can be represented by a second-order kinetic model. We examined this hypothesis and found that if the ratio of the initial concentrations of the two metal complexes and the ratio of two different first-order rate constants are within certain narrow ranges, the concentration vs. time data can be represented by a second-order kinetic model very well even up to 92% conversion. The previous publications use crude oils or residual oils which contain many metal compounds of unspecified nature and quantity. The presence of sulfur compounds, nitrogen compounds, and asphaltenes could also affect the kinetics of hydrodemetallation reaction. In view of this, our experiments used pure model metal compounds of known structure dissolved in white oil, so that the kinetics of hydrodemetallation can be studied for each compound individually. In this way, the kinetic result will not be affected by other metal compounds, sulfur compounds, and other materials commonly occurring in residual oils. This paper deals with the kinetics of hydrodemetallation of nickel etioporphyrin (I) and nickel tetraphenylporphine. Experimental Section (1) Equipment. A schematic of the autoclave batch reactor system is shown in Figure 1. The 1-L autoclave 0 1980 American
Chemical Society
Ind. Eng. Chem. Process Des. Dev., Vol. 19, No. 2, 1980 251
Table 11. Property of White Oil (Nujol) (1)density ( 2 ) viscosity
0.876 g/cm3 a t 24.67 "C 100 "F, 360-390 su 210 O F , 54 ssu C,,H,, 417 676-927 " F (atmosphere pressure) 406-624 " F (10 mmHg)
( 3 ) average formula ( 4 ) average molecular weight (5) boiling point range
d
'
1
A L ' o ~ I o ~ ?
Figure 1. Schematic of high-pressure autoclave for hydrodemetallation study. NI-TPP
Table I. Property of CoO-MoO,/Al,O, Catalyst and y-Alumina Carrier A. Coo-MoOJA1, 0, (American Cyanamid HDS-16A) (1)chemical compositions c o0 5.7 wt % MOO, 12.2 wt % Na, 0 0.03 wt % Fe 0.04 wt % ( 2 ) physical properties pore volume 0.43 cm3/g average pore diameter 80.4 A surface area 1 7 6 m'/g density 0.67 g/cm3 (dried, 0.074-0.088 m m ) B. y-Alumina (Norton Co. SA-6273 -in. Spheres, Sample No. 63012) (1)chemical compositions All 0 3 >99.85 wt % Na, 0
