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Received for review April 21, 1975 Accepted August 5,1975
Issued as NRC No. 14983.
Demetalation of Petroleum Residua Using Manganese Nodules Clarence D. Chang' and Anthony J. Sllvestrl Mobil Research and Development Corporation, Central Research Division, Princeton, New Jersey 08540
The catalytic activity of Lake Michigan manganese nodules (LMN) for demetalation of various petroleum residuals has been examined. The influence of hydrogen pressure on the aging characteristics of the LMN catalyst was compared against a commercial Co/Mo/A1203 catalyst and an activated bauxite (Porocel). The LMN catalyst was found to have a comparatively lower aging rate as the hydrogen pressure was reduced below 2000 psig. This was attributed to its unusual macropore structure.
Introduction Catalytic hydroprocessing of heavy petroleum fractions has become increasingly important in recent times. The need for more efficient feedstock utilization has been occasioned by rapidly escalating crude oil costs and by the tightening of environmental controls. A well-recognized problem associated with the upgrading of petroleum residuals is the presence of trace metals. These contaminants tend to accumulate on catalysts during processing, decreasing catalyst effectiveness, and leading ultimately to irreversible deactivation. The metals problem has been extensively researched in the past. Among the numerous approaches taken, one can cite the development of catalysts with increased resistance to metals poisoning (Beuther et al., 1968), the use of ebullated beds (Van Driessen et al., 1968), and the direct removal of metals from feedstocks by various physical and chemical means. In the U S . alone over 300 patents have issued dealing with the removal of metal contaminants from various petroleum fractions. One of the more practical methods for feedstock demetalation is the use of pretreatment guard-chambers containing solid absorbents. Such technology is used in Chevron's Isomax process (Paradis et al., 1971) and HRI-Citgo's H-Oil process (Johnson et al., 1972). The feasibility of the guard-chamber technique depends on the availability of adsorbents having pore structures which will not impede the diffusion of the metal-containing asphaltene colloids (10-100 8, diameter), and which are inexpensive enough to be discarded after a single cycle. Activated bauxite has been mentioned in this regard as a cheap naturally occurring adsorbent (Porter et al., 1955). Manganese nodules, another naturally occurring mineral, have recently been found to be catalytically active for the demetalation of topped crude in the presence of hydrogen
(Silvestri and Weisz, 1973; Chang and Silvestri, 1974). Manganese nodules occur in great abundance in both marine and fresh water sediments. It is estimated that as much as 10l2 metric tons may be found in the Pacific Ocean alone (Mero, 1962). In contrast to other mineral resources, manganese nodules are unique in thethat they are apparently self-replenishing. Although the mechanism of formation is not completely understood, it is estimated that in the Pacific, nodules are being formed at a rate of about 6 X lo6 metric tons a year. A number of processes for harvesting marine nodules for metals recovery are reported to be close to commercialization (Hammond, 1974). Aside from their great abundance and their catalytic usefulness, manganese nodules are potentially very cheap. The cost of production was estimated some years ago to be between $2 and $40 per ton for deep sea nodules (Mero, 1965). Even if this estimate were now doubled, reflecting the pressure of inflation over the last decade, the cost would still be substantially lower than that of manufactured catalysts and competitive with most naturally occurring adsorbents. Manganese nodules have been found in Lake Michigan as well as other fresh water bodies in the U S . Fresh water nodules may be even cheaper to mine than marine nodules since they occur a t depths of only several hundred feet, in contrast to thousands of feet for the marine nodules. In this paper we describe the demetalation of Kuwait atmospheric and vacuum residua, and an Agha Jari topped crude, in the presence of hydrogen over fresh water manganese nodules. The effect of hydrogen partial pressure on demetalation activity is examined, with comparisons made against commercial Co/Mo and bauxite (Porocel) catalysts. Experimental Section Experiments were carried out in high-pressure, tricklebed microreactors containing 20-100 cm3 of catalyst. A Ind. Eng. Chem., Process Des. Dev., Vol. 15. No. 1, 1976
161
Table I. Feedstock Properties
Table 11. Catalyst Properties “API
Kuwait atmospheric resid Kuwait vacuum resid Agha Jari 400+ topped cru&
Surface Particle Real area, Pore vol, density, density, m z g - ‘ cm3 g-’ g c m T 3 g ~ m - ~
Ni, V, %N ppmppm
%S
0.19 12 46 0.30 37 91 0.20 13 46
3.89 6.8 5.63 24.4 2.20 18.4
Lake Michigan nodules (LMN) Porocel (activated bauxite) 3% CoO/9% MOO,/
V
9
-v
IO II
12 I3
I
’
i
1-1
14 I5 I6 17 V
1.49
3.75
129
0.32
1.59
3.26
0.35 1.55 Metals Content of Lake Michigan Nodules
I M K E REGULATOR
2 3 4 5 6 7 6
0.41
3.39
161
A1Z03
I
209
METERING VALVE MASS FLOWMETER FILTER PUMP 3-ZONE NRNACE REACTOR BACK PRESSURE REGULATOR MbNOMETER CONDENSER LIQUID PRODUCT RECEIVER GAS SAMPLE CAUSTIC SCRUBBER WET TEST METER RUPTURE DISC AUTOMATIC SAFETY VALVE PRESSURE s w i n n VENl
Metal Mn Fe
wt % 9.2 35.4
Ni
