The adsorption of ammonium heptamolybdate (AHM) on phosphated alumina and of P2Mo50231 23456~a nd PMo^O^3-on 7-Al203 has been studied by using FTIR, Raman, and 31P solid-state NMR spectroscopies, and TPR. Adsorption of phosphate prior to contacting of 7-Al203 with AHM leads to a deactivation of the alumina surface still remaining. Phosphate reacts with 7-Al203 to form an A!P04-type surface phase, which itself is capable of adsorbing molybdate, with the formation of an irreducible surface molybdophosphate, its adsorption capacity being lower, however, than that of the original alumina. The primary phosphomolybdate adsorption reaction on alumina is shown to be the same as that observed in the case of AHM, viz., a reaction with the basic surface OH groups, leading to the decomposition of the adsorbing species. Thiophene hydrodesulfurization (HDS) activity data of variously prepared Mo(P)/A1203 catalysts are in agreement with the idea that HDS activity increases with increasing Mo reducibility.

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CoAPO molecular sieves of the structure types 5, 11, 16 and 34 have been investigated by means of electron absorption spectroscopy, temperature-programmed reduction and infrared spectroscopy in combination with pyridine adsorption, the purpose being to determine the amounts of framework and non-framework cobalt and to study the properties of incorporated cobalt with respect to stability, redox behaviour and associated acidic properties. It has been shown that framework and non-framework cobalt species exhibit different spectroscopic properties and can be distinguished from each other. The framework cobalt acceptance and the stability of the different structures decrease in the order CoAP0,-5 > CoAP0,-11 > CoAP0,-16 > CoAP0,-34. In stable structures such as 5 and 11, framework cobalt can perform reversible redox reactions Co" = C o ' ' ' , which are accompanied by changes in the concentration of Brsnsted and Lewis acid sites.

A rapid assessment of product quality can often be made using a combination of near-infrared spectroscopy (NIR) and multivariate calibration. The robustness of such a method is determined by the sensitivity of the multivariate calibration model to variations in the spectral data. An approach is described that uses a combination of experimental design methodology and principal component analysis to identify the main sources of variation in the spectra and to estimate their influence on the quantitative predictions. This is accomplished by comparing variations in a set of measured, replicate spectra to spectra with simulated variations. The approach was applied to the hydroxyl number determination of polyols by NIR spectroscopy and partial least-squares calibration. The results indicated that the most significant sources of variation were due to a variable cell path length and a variable curved background. Correction for these errors resulted in a 58% reduction in the standard deviation of the hydroxyl number predictions, indicating that a substantial improvement in the method precision is possible.

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