The loss of Cu/ZnO/Al 2 O 3 activity for methanol synthesis has been studied over 50 h under a range of synthesis gas compositions. Experiments have been carried out at differential and finite conversions in order to compare deactivation under the pure feed to that in the presence of products. Under differential conversion, it was found that the degree of deactivation was related to the CO concentration, being particularly acute under CO/H 2 . Under CO/H 2 , there was a close correlation between activity loss and loss of Cu surface area, suggesting that an important cause of deactivation is sintering, which may be promoted by over-reduction of Cu. At finite conversion with CO/H 2 feed the deactivation was less severe. This lower rate of deactivation is most likely due to exposure of the catalyst to products that can stabilize oxidized Cu species. Interestingly, under CO 2 /H 2 , the deactivation was negligible at differential conversion. However some deactivation was apparent at finite conversion. The exposure of the catalyst to the products, CO and water, at finite conversion can explain these results.
Abstract158 MHz SAW oscillators coated with organic polymers and zeolites were tested as sensors for monitoring the level of humidity and carbon dioxide in a flowing stream of nitrogen. All coatings exhibited responses to water vapor on the order of kilohertz frequency shifts, while the responses to carbon dioxide were significantly (generally one order of magnitude) smaller. The presence of CO2 dramatically interfered with the detection of water with poly-(ethylenimine) (PEI) coatings. Poly-vinyl pyridine (PVP) coatings showed large responses to water without any interference from CO2; CO2 produced little response whether water was present or not. ZSM-5 coatings also showed no evidence of interference between water and CO2; a detectable response for CO2 is possible in humid nitrogen.
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