Test methods Mitchell method

The catalysts with metals are previously impregnated with solutions of vanadyl and nickel naphtenates based on the Mitchell method [4], Before hydrothermal deactivation the samples were calcined in air at 600°C. The activity was performed in the conventional MAT test using 5 grams of catalyst, ratio cat/oil 5, stripping time 35 seconds, and reaction temperature 515°C. Elemental analyses to determine the total amount of carbon in the spent catalysts were done by the combustion method using a LECO analyzer. 

A simplified cyclic test (Mitchell method followed by cyclic propylene steaming) has been proposed which addresses the redox aging of the metal, but not the non-uniform laydown and age distribution of metals on the catalyst. Under actual FCC conditions, the penetration and age profile of the metals will influence the efficiency of the catalyst metal trapping function [23,39,40] and consequently catalyst activity and selectivity. 

An early attempt to simulate metals deactivation was the introduction of the Mitchell method steam deactivation procedure (2). This procedure involved impregnation of catalysts with Ni and V naphthenates, followed by steaming in the presence of air. While this method was easy to implement and did allow comparison of catalysts in the presence of metal contaminants, both the destruction of the zeolite and the metal dehydrogenation activity was greatly over-predicted (3, 4) in both MAT and riser testing. 

Test Methods. Since its inception, the Mitchell Method (MM) or slight variations (often referred to as the Modified Mitchell Method) have been en )loyed by researchers evaluating FCC catalyst as a sin )le, inexpensive, and fast procedure by which to simulate the effect of contaminant metals on catalyst performance. As a fallout of more sophisticated catalytic testing in fixed fluid bed reactors, the method of cycUc metals deposition (CMD) has also emerged as a useful method for introducing metal contaminants. 

It would be desirous to have available a sinq)ler testing tool which could imitate many of the aspects of the cyclic deposition particularly the inq)ingement of the metals on the catalyst surface with the simplicity, efficiency, and cost of the Mitchell Method. One such test, at least so far developed for vanadium interaction, is what we termed above as the Engelhard Transfer Method (ETM) (7). 

Conclusions. It is necessary to test a catalyst s stabihty and performance under high vanadium conditions for materials which will be processing metals laden feedstocks. The Engelhard Transfer Method offers the benefits of both the Mitchell Method and... 

Various assay methods have been used to detect the presence of inhibitory substances. These include some of the classical tests used by investigators of growth-promoting substances—i.e., the various Avena coleoptile assays which utilize intact, decapitated, or isolated cylinders and the split pea stem test. Effects on seed germination and seedling shoot or root growth and development have also been measured in addition to other visible expressions of inhibition. Details of many of these tests have been compiled by Mitchell et al. (99). Tests have been carried out in Petri dishes, with various solution culture techniques, and by sand and soil culture. Effects so measured may or may not be similar to those obtained under field situations— i.e., the establishment of inhibition under controlled conditions pro-... 

Murray FES, Mitchell R, Ford T (1993) In Experimental methods for the study of microbial mediated corrosion. NACE International, Houston Myers T (1988) Failing the test germicides or use dilution methodology ASM News 54 19—21... 

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