Effect of Chemical Composition on the Structure and Catalytic Behaviour of AlPO4 and Al2O3–AlPO4 Mixed Catalysts

AlPO4 and Al2O3–AlPO4 mixed catalysts of different composition (Al/P > 1) were prepared and calcined in the temperature range 350–650°C. Such catalysts were characterized by DTA and X-ray diffraction methods, and by nitrogen adsorption studies at −196°C. Their acidity was determined using a calor...

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Published inAdsorption science & technology Vol. 20; no. 2; pp. 131 - 140
Main Authors Mohamed, F.Sh, Kiwan, H.H., Mostafa, M.R.
Format Journal Article
LanguageEnglish
Published London, England SAGE Publications 01.01.2002
Multi Science
Subjects
Catalysis
Catalytic reactions
Chemistry
Exact sciences and technology
General and physical chemistry
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
Mixed catalyst
Structure effect
Catalytic reaction
Heat treatment
Acidic site
Composition effect
Propanol
Dehydration
Experimental study
Heterogeneous catalysis
Aluminium Oxides
Secondary alcohol
Aluminium phosphate
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Summary:AlPO4 and Al2O3–AlPO4 mixed catalysts of different composition (Al/P > 1) were prepared and calcined in the temperature range 350–650°C. Such catalysts were characterized by DTA and X-ray diffraction methods, and by nitrogen adsorption studies at −196°C. Their acidity was determined using a calorimetric titration method while their catalytic activity towards the dehydration of isopropanol was determined using a pulse microcatalytic technique. The data obtained from XRD studies showed that pure AlPO4 when calcined at 650°C had a rather low crystallinity with its crystalline structure (which is of the α-cristobalite type) being characterized by poorly developed peaks. However, significant changes in the texture, surface acidity and catalytic activity were observed as a result of changing the chemical composition of the solid, with the surface area, total pore volume and surface acidity generally increasing with increasing alumina content. Sintering commenced above 550°C leading to a decrease in the surface area and to pore widening. Dehydration of isopropanol appeared to be insensitive to the structure of the catalysts investigated but was related to the surface acid density.
ISSN:0263-6174
2048-4038
DOI:10.1260/026361702320360559