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.
Similar content being viewed by others
References
J.M. Campelo, A. Garcia, D. Luna, J.M. Marinas and M.I. Martinez, Mater. Chem. Phys. 21 (1989) 409.
F.M. Bautista, J.M. Campelo, A. Garcia, D. Luna, J.M. Marinas and A.A. Romero, Appl. Catal., in press.
F.M. Bautista, J.M. Campelo, A. Garcia, D. Luna, J.M. Marinas and A.A. Romero, Appl. Catal., in press.
J.M. Campelo, A. Garcia, J.M. Gutierrez, D. Luna and J.M. Marinas, Can. J. Chem. 62 (1984) 638.
J.A. Cabello, J.M. Campelo, A. Garcia, D. Luna and J.M. Marinas, J. Org. Chem. 49 (1984) 5195.
F.M. Fowkes, in:Attractive Forces at Interfaces, in Wetting, Monograph No. 25 (Soc. Chem. Ind., London, 1967) pp. 3–30.
V. Gutmann, in:The Donor-Acceptor Approach to Molecular Interactions (Plenum Press, New York, 1978).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Bautista, F.M., Campelo, J.M., Garcia, A. et al. A1PO4-Al2O3 catalysts with low alumina content. III. Surface basicity of catalysts obtained in aqueous ammonia. Catal Lett 19, 137–142 (1993). https://doi.org/10.1007/BF00771748
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00771748