Deactivation of Oxidation Catalysts for VOC Abatement by Si and P Compounds

BY MOHAMMAD RAHMANI, KHASHAYAR BADII, MOSTAFA FAGHIHI, MEHRI SANATI, NEIL CRUISE, OLA AUGUSTSSON, 

Understanding the deactivation processes that take place in oxidation catalysts used for volatile organic compound (VOC) abatement has both industrial and academic interest. The industrial importance of improving the deactivation resistance of catalysts used to remove VOC emissions is directly related to the economics of this process. The market for such equipment will grow significantly in the next few years. For example, in Europe the Solvent Emissions Directive adopted by the EU s Environmental Ministers in 1999 seeks to reduce VOC emissions from operations using solvents by 67 % by 2007, based 1990 levels. The EU member states have now adopted these directives into national law. 

This directive will affect over 400,000 solvent users across more than 30 manufacturing sectors. Current estimates, from the European solvent industry, suggest that this directive will reduce emissions by 1.5 million tonnes a year and cost industry 80 billion to implement. 

A key challenge is to acquire a better understanding of the mechanisms for silica and phosphorus deactivation. This better understanding can then be used to produce catalysts with minimal deactivation even for the most severe emissions. 

From a scientific standpoint, there is an interesting relationship between the fouling and poisoning mechanisms that are typical of silica deactivation, and the poisoning mechanism that more accurately describes phosphorous deactivation. It is of interest to carefully review the dependence and interplay of these processes as a function of the reactant, catalyst support, pore structure, metal loading, and oxidation conditions. 

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