Insidious problems

In designing fixed and ideal fluidized-bed catalytic reactors, we have assumed up to now that the activity of the catalyst remains constant throughout the catalyst s life. That is, the total concentration of active sites, C accessible to the reaction does not change with time. Unfortunately, Mother Nature is not so kind as to allow this behavior to be the case in most industrially significant catalytic reactions. One of the most insidious problems in catalysis is the loss of catalytic activity that occurs as the reaction takes place on the catalyst. A wide variety of mechanisms have been proposed by Butt and Petersen, to explain and model catalyst deactivation. 

A more insidious problem is the limitation on precision imposed by the vanishingly small magnitude of the anodic (corrosion) component compared with the cathodic partial current at large values of cathodic bias, due to the exponential form of the current-voltage relationships for the anodic and cathodic half-reactions. 

Pinholes and voids, although seem innocuous, can create insidious problems such as the following, after firing. 

A more insidious problem results from improper use of a control valve hand jack. The hand jack is a wheel attached to a control valve that can be manually used to move the valve. There is an indicator on the hand jack showing whether it is being used to open or close the control valve. Normally, the hand jack should be in the neutral position. In this position, it is disengaged from the control valve. 

However, some displays are ambignons or counterintnitive. This introdnces a particularly insidious problem, since treatment decisions will be based on this information—these decisions could be perfectly reasonable and yet wrong. 

Since the sample solution must pass through one of the nebulizer capillaries, partial clogging or blockage can result from suspended particulate matter in the sample or to a lesser extent high dissolved solids concentrations in the samples that precipitate at the tip as a result of solvent evaporation. This can be a particularly insidious problem because partial blockage... 

This is the most insidious problem of all, since it has been completely neglected by most users. Instead of working with an arbitrary scheme as before, it would be more useful to base my explanation on concrete facts borrowed from Nimbus 3, and on an isolated example from an ESS A satellite. 

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