Applied Catalysis A: General 171 (1998) 161±165
Testing of resid FCC catalysts in MAT Trond Myrstad*, Hege Engan Statoil R&D Centre, Postuttak, N-7005 Trondheim, Norway Received 18 February 1998; received in revised form 6 March 1998; accepted 14 March 1998
Abstract Employing atmospheric residues when testing FCC catalysts in MAT often faces serious problems with poor mass balances and interrupted operation due to coking of the equipment. When changing to a feed-injection tube made by electroformed nickel (EFNI) in the Statoil MAT unit, the scattering in mass balances was reduced by a factor of four, and the number of interrupted test series was decreased by a factor of two. The reason for the improved results, using an EFNI tube, is the materials lower tendency to form coke, and consequent reduction in clogging. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Fluid catalytic cracking; Catalyst testing; Micro activity test
1. Introduction Despite the fundamental differences between the ®xed bed microactivity test (MAT) unit and a commercial FCC unit, the use of microactivity testing has been found applicable for testing and ranking of FCC catalysts, even though the need for additional testing in a pilot riser has been documented for residues [1]. Testing of residues in small-scale laboratory units, such as MAT units, often presents serious problems. Problems regarding poor mass balances and interrupted operation due to blocking of the equipment by coking have been reported [2]. Despite this, Statoil have chosen to use atmospheric residue as feed in the MAT experiments, as the ranking of residue catalysts have been found to be different, dependent on whether VGO or atmospheric residue were used as feed [3]. *Corresponding author. Fax: 00 47 7358 4618; e-mail:
[email protected] 0926-860X/98/$19.00 # 1998 Elsevier Science B.V. All rights reserved. PII S0926-860X(98)00100-8
This paper discusses how the Statoil MAT unit was modi®ed in order to meet these challenges. 2. Experimental The MAT experiments were performed in a fully automated unit, originally delivered by Vinci Technologies, France, but with several modi®cations made by Statoil. A simpli®ed drawing of the MAT unit is shown in Fig. 1. The feed is injected from a syringe through a multiport valve. After preheating of the feed by an infrared lamp, the feed is introduced to the reactor through a 1.2 mm I.D. injection tube at the reactor inlet. After the reactor, a multiport valve gives the possibility of running eight experiments in the same test series. The product from the different experiments are routed to separate liquid receivers. Gaseous products from the experiments are collected in a gas collector, and analysed online on a GC
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Fig. 1. Simplified drawing of the Statoil automated MAT unit.
equipped with a re®nery gas analyser (Hewlett±Packard 5890). After the reaction and stripping with N2, the catalyst is regenerated by air. After regeneration, the next experiment can be performed. During regeneration, coke is converted to a mixture of CO and CO2. CO is converted to CO2 in a CO converter, and the amount of CO2 is determined by an infrared CO2 analyser (Guardian). The liquid products are weighted and analysed by simulated distillation on GC (Chrompack CP9000). Based on the gas and liquid analyses and the CO2 analysis, the mass balance, conversion and yields are calculated. In all reports, normalised yields are used. The feed used was a north sea atmospheric residue with 4.2 wt% conradson carbon, and a boiling point distribution as shown in Table 1. In the tests 3 g of an FCC equilibrium catalyst were used. Metals level on this catalyst were approximately 2800 ppm Ni and 4200 ppm V. The oil injection time was 30 s, the reaction temperature was 5248C, and the regeneration temperature was 5488C. The catalyst : oil ratio was varied from 2 to 5 by varying the amount of feed injected.
Table 1 Feed boiling point distribution %
8C
0 10 30 50 70 90 100
230 348 421 468 528 624 714
Injection tubes of three different materials were tested: stainless steel (SS304); glass lined tubing (GLT), delivered by Teknolab, Norway; and electroformed nickel tubing (EFNI), also delivered by Teknolab. 3. Results and discussion The major advantage gained by using an automated MAT unit is the possibility to run several experiments without operator intervention. When performing well, such a unit gives the possibility to at least double the
T. Myrstad, H. Engan / Applied Catalysis A: General 171 (1998) 161±165
number of MAT experiments compared with a manually operated unit within a given time frame. In its original design, however, the series of experiments
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were often interrupted when processing resid, due to coke formation, mainly in the injection tube (see Fig. 1). Even partial clogging of the injection tube
Fig. 2. Naphtha yield vs. conversion. (~), SS304; (*), GLT; and (&), EFNI.
Fig. 3. Coke yield vs. conversion. (~), SS304; (*), GLT; and (&), EFNI.
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T. Myrstad, H. Engan / Applied Catalysis A: General 171 (1998) 161±165
was found to be a problem, due to scattering in the mass balances. In an attempt to prevent coking, several materials were considered but ®nally two new injection tube materials were selected for testing, glass lined tubing (GLT) and electroformed nickel (EFNI). GLT is made by fusing an integral borosilicate lining onto the inside surface of stainless steel, while EFNI is made by electroplating pure nickel over a diamond drawn mandrel. Both materials are claimed to have extremely smooth and inert surfaces. Both the GLT and the EFNI tube had slightly lower I.D. than the SS304 tube, 1.0 and 0.8 mm, respectively, but based on earlier experience, this was not expected to cause any signi®cant differences.
Three series of experiments were performed in order to test the different injection tubes, and signi®cant differences in the yield patterns were observed, as illustrated in Figs. 2 and 3. Both the GLT and EFNI tubes gave less coke and more naphtha than the SS304 tube. The lower coke formation tendency gave reduced clogging problems, and thereby improved mass balances. Due to the lower material costs for EFNI, it was decided to use this material in future MAT experiments. The effect of changing to the EFNI injection tube was very clear. The scattering in mass balances was signi®cantly reduced, as is illustrated in Fig. 4, where the standard deviation of the mass balances in the last twenty series using the SS304 injection tube, and the
Fig. 4. Comparison of mass balance standard deviation for SS304 and EFNI tubes: (&), SS304; (&), EFNI.
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Fig. 5. Stability of EFNI injection tube. Naphtha yield vs. conversion. (~), fresh tube; (*), after 5 months use.
standard deviation of the mass balances in the ®rst twenty series using the new EFNI injection tube are shown. After switching from SS304 to EFNI, the average standard deviation was decreased from 2.5 to 0.51. Another effect when changing to the EFNI injection tube was that the number of interrupted experiments was decreased by a factor of two. One concern of changing the injection tube was the stability of the EFNI material. There was a possibility that the repeated cycles of cracking and regeneration could give changes in the surface structure of the injection tube. Since nickel is known to promote dehydrogenation reactions, there was a concern that this could affect the experimental results. However, after 5 months in use, the EFNI injection tube did not show any yield changes. This is illustrated in Fig. 5, where naphtha yields from MAT experiments using a fresh injection tube, and the same injection tube after 5 months in use, with the same feed and catalyst, are shown.
4. Conclusion When processing resid in MAT, experiments were often interrupted due to clogging caused by the coke. When changing to a feed-injection tube made by electroformed nickel (EFNI), the scattering in mass balances was reduced by a factor of four, and the number of interrupted test series was decreased by a factor of two. The reason for the improved results, using an EFNI injection tube, was the materials lower tendency towards coke formation and consequent reduction in clogging. References [1] S.I. Andersson, T. Myrstad, Evaluation of residue FCC Catalysts, Accepted for publication, Applied Catalysis A: General, 1998. [2] A.C. Pouwels, F. Olthof, H. Wijngaards, Akzo Nobel FCC Symposium, 1994. [3] S.I. Andersson, J.E. Otterstedt, Katalistiks 8th Annual FCC Symposium, Paper 21, Budapest, 1987.
