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- Activity–acidity relationship in zeolite Y: Part 3. Application of Brönsted type equationsPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaThe relation between activity and acidity in a variety of Y zeolite catalysts for the transformation of small olefins: ethene, propene, 1-butene and iso-butene, is presented. The acid site distribution of these samples was estimated by temperature-programmed desorption of ammonia, by using a numerical deconvolution technique. This information was then correlated with catalytic activity measurements using Brönsted type equations. Despite the complexity of calculations it is clear that this gas phase solid acid catalysed reactions follow simple rules, similar to the one observed in homogeneous processes.
- Activity–acidity relationship in zeolite Y: Part 1. Transformation of light olefinsPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaReactions of ethene, propene, 1-butene and iso-butene over two series of catalysts, HNaY (prepared from NaY zeolite) and HNaUSY (prepared from NH4USY zeolite), were studied. The catalytic activity for the transformation of these olefins follows the expected order according to the ease of formation of the respective carbocations: ethene
- Activity–acidity relationship in zeolite ZSM-5. Application of Brönsted-type equationsPublication . Costa, Carla; Dzikh, I. P.; Lopes, Jose M.; Lemos, Francisco; Ribeiro, Fernando RamôaIn this paper the relation between activity and acidity in a variety of ZSM-5 zeolite catalysts, with different Si/Al ratios and different protonic content, is analysed and a quantitative correlation is obtained. The acid site strength distribution was estimated using temperature-programmed desorption (TPD) of ammonia by applying a digital deconvolution method to the curves. These data were then correlated with experimental catalytic activity data for the same catalysts towards n-heptane cracking reaction, by means of a Brönsted-type equation similar to the ones used for homogeneous acid catalysis and already used for other zeolites. It can be noticed that the same types of equation that are used for homogeneous acid catalysis also hold for heterogeneous acid catalysis and that the activation energy for ammonia desorption can be used as acid-strength scale for the purpose of correlation with catalytic activity.
- Activity–acidity relationship in zeolite Y: Part 2. Determination of the acid strength distribution by temperature programmed desorption of ammoniaPublication . Costa, Carla; Lopes, Jose M.; Lemos, Francisco; Ribeiro, F. RamôaIn this paper we will have a detailed look at a numerical procedure that allows the estimation of the acid site strength distribution using a single temperature programmed desorption (TPD) experiment. The possibility of estimating these parameters is of paramount importance in the determination of quantitative relationships between activity and acidity. The application of the procedure to a set of simulated thermograms gives a clear view of the applicability of this method. The procedure was tested both in single and multi energy distributions, as well as quasi-continuum distributions. Then the method has been applied on TPD thermograms obtained from catalysts based on two different forms of zeolite Y. In part 3 of this series, the acid site distributions obtained here will be used in an activity–acidity relationship, using a Brönsted type equation, similar to the one used in homogeneous acid catalysis.