ISSN:
1572-879X
Keywords:
AlPO4
;
AlPO4-Al2O3
;
surface basicity
;
Langmuir adsorption
;
Knoevenagel condensation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The amount of basic sites of A1PO4-Al2O3 (APA1-A, 5–15 wt% Al2O3) catalysts at two basic strengths was measured by studying the liquid-phase adsorption of two acidic molecules (benzoic acid (BA, pK = 4.2) and phenol (PH, pKa = 9.9) from cyclohexane solutions, through the application of a spectrophotometric method. The data obtained follow the Langmuir adsorption isotherm and the monolayer coverage at equilibrium (at 298 K),X m, is assumed as the amount of basic sites corresponding to the specific pK of the acid used as titrant. The amount of basic sites of any AlPO4-Al2O3 catalyst is higher than that of AlPO4, but lower than that of Al2O3. Besides, an increase in the Al2O3 content from 10 wt% gradually increases the basicity of the APA1-A catalyst. Moreover, calcination at increasing temperatures does not practically affect the surface basicity of APAl-A-5 and APAl-A-10 catalysts. However, for AlPO4 content higher than 10 wt% we observe a decrease in surface basicity, this decrease depends on alumina content, i.e. it is higher as the amount of alumina increases. The basic sites of APAl-A systems catalyze the Knoevenagel condensation ofp-methoxybenzaldehyde and malononitrile at room temperature and in the absence of solvent.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00771748
Permalink
