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Comparison of Catalytic Cracking Performance between Riser Reactor and Microactivity Test (MAT) Unit Siauw Ng,*,† Hong Yang,† Jinsheng Wang,‡ Yuxia Zhu,† Craig Fairbridge,† and Sok Yui§ National Centre for Upgrading Technology, 1 Oil Patch Drive, Suite A202, Devon, Alberta, Canada T9G 1A8, CANMET Energy Technology Centre, 1 Haanel Drive, Nepean, Ontario, Canada K1A 1M1, and Syncrude Research Centre, 9421-17 Avenue, Edmonton, Alberta, Canada T6N 1H4 Received May 31, 2000. Revised Manuscript Received January 26, 2001
A fluid catalytic cracking (FCC) study of 10 vacuum gas oil feeds was performed using a fixedbed microactivity test (MAT) unit. Gas, liquid, and coke yields at several conversion levels were compared with reported pilot plant data obtained from a modified ARCO riser reactor using the same feeds. The data indicated that except for coke yield, MAT results were, in most cases, within 15% of the corresponding riser yields. Good linear correlations could be established between MAT and riser yields except for liquefied petroleum gas (LPG) and light cycle oil (LCO). Causes for the relatively poor correlations for the two products were analyzed and discussed. Despite the substantial differences in reactor design, flow pattern, and operation between the two systems, the MAT unit can predict the riser performance when appropriate test conditions are applied.
The fluid catalytic cracking (FCC) unit for converting heavy gas oils to gasoline and other valuable products is the heart of a modern refinery. The microactivity test (MAT) based on ASTM D 5154, originally designed for catalyst screening, has been popularly used as a quick and cost-effective tool to provide FCC-related information.1 Like all laboratory methods, the significance of the MAT test depends on its commercial relevance, i.e., if it can realistically simulate aspects of the commercial process.2 Because of fundamental differences between the MAT and FCC riser systems in reactor design, hydrodynamics, catalyst contact time, feed preheat and vaporization, etc., the MAT test cannot duplicate the dynamic FCC riser operation. However, advances in MAT technology have made this simple method a useful tool to predict riser behavior.1,3,4 This is achieved by interpreting correctly the yield and product quality data obtained from MAT and verifying the interpretation, if necessary, by pilot-scale riser operation. As an industrial practice, a circulating riser pilot plant is used to bridge * Author to whom correspondence should be addressed. Fax: 1-780987-5349. E-mail:
[email protected]. † National Centre for Upgrading Technology. ‡ CANMET Energy Technology Centre. § Syncrude Research Centre. (1) Moorehead, E. L.; McLean, J. B.; Cronkright, W. A. Microactivity Evaluation of FCC Catalysts in the Laboratory: Principles, Approaches and Applications. In Fluid Catalytic Cracking: Science and Technology, Studies in Surface Science and Catalysis; Magee, J. S., Mitchell, M. M., Jr., Eds.; Elsevier Science Publishers B. V.: New York, 1993; Vol. 76, pp 223-255. (2) Young, G. W. Realistic Assessment of FCC Catalyst Performance in the Laboratory. In Fluid Catalytic Cracking: Science and Technology, Studies in Surface Science and Catalysis; Magee, J. S., Mitchell, M. M., Jr., Eds.; Elsevier Science Publishers B. V.: New York, 1993; Vol. 76, pp 257-292. (3) Biswas, J.; Maxwell, I. E. Appl. Catal. 1990, 63, 197-258. (4) Ng, S. H.; Briker, Y.; Zhu, Y.; Gentzis, T.; Ring, Z.; Fairbridge, C.; Ding, F.; Yui, S. Energy Fuels 2000, 14 (4), 945-946.
the gap between the laboratory MAT unit and the commercial FCC reactor. Pilot tests are much more expensive to run due to the heavy capital and operating costs involved. For better simulation of commercial performance, it is desirable to design MAT experiments by choosing specific test conditions so that the data produced are as close as possible to the commercial or pilot plant results. In the present work, the same set of conditions was applied to 10 vacuum gas oils (VGOs) which were run in both MAT and riser pilot plant units. Originally, it was intended to use the MAT data to guide the subsequent pilot plant operation of which the results were reported in 1998.5 The current paper is probably the first refereed publication which describes the performance relationship between the MAT and the pilot riser based on quite a variety of feeds. The fixed-bed MAT unit used was an automated Zeton Automat IV, a modified version of ASTM D 5154 equipped with collection systems for gas and liquid products. For each feed, three runs were conducted at 510 °C and one and two runs were at 500 and 520 °C, respectively. Since the reaction temperature range was rather small ((10 °C at 510 °C), it was assumed that the temperature effect on MAT yields was negligible and that one regression could be applied to the same set of data points obtained at three different temperatures. The reactor was loaded with 4 g of catalyst (Engelhard’s equilibrium catalyst, Dimension 60), and the unit was purged with nitrogen (20 mL/min) during testing. The catalyst contact time was kept at 30 s for all runs. Collected liquid products were weighed and then analyzed by simulated distillation (ASTM D 2887) to determine the yields of gasoline (IBP/216 °C), light cycle (5) Yui, S.; Matsumoto, N.; Sasaki, Y. Oil Gas J. 1998, 96 (3), 4351.
10.1021/ef000115o CCC: $20.00 Published 2001 by the American Chemical Society Published on Web 05/25/2001
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Table 1. Summary of Feedstock Propertiesa feed number
1
feed name density at 15 °C, g/mL hydrogen, wt % H/C atomic ratio total nitrogen, wppm total sulfur, wppm MCR, wt % Ni + V, wppm aromatic carbon, % 343 °C-, wt % 524 °C+, wt % conversion precursors, wt % a
2
3
4
5
6
7
8
9
10
HCB
RZ
HT-VIR
HT-LCF
HTDA-BIT
HTC
VIR
LCF
DA-LCF
DA-BIT
0.8643 13.7 1.892
