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SYNTHESIS, CHARACTERIZATION AND CATALYTIC PERFORMANCE OF THE SOLID ACID DAF-1

WRIGHT, PA; SAYAG, C; REY, F; LEWIS, DW; GALE, JD; NATARAJAN, S; THOMAS, JM; (1995) SYNTHESIS, CHARACTERIZATION AND CATALYTIC PERFORMANCE OF THE SOLID ACID DAF-1. J CHEM SOC FARADAY T , 91 (19) 3537 - 3547.

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Abstract

The novel aluminophosphate-based microporous solid DAF-1 may be prepared in aqueous or non-aqueous media, its framework composition being determined by the need to charge balance organic cations taken up into the structure. In aqueous conditions the framework charge is 0.22(-) per AIPO(4) unit which may result from magnesium (for aluminium) or magnesium plus silicon (for phosphorus) substitution. Computer simulation of the framework-template interaction for the successful octa- and deca-methonium templates suggests templating action occurs in the narrower channels, with the organic cation acting only as a void filler in the larger cavities. DAF-1 is capable of assimilating heteroatoms into the framework in varying concentrations: Co substituting for Mg, Ga and Al and Si for P. Characterisation of the framework structure by advanced energy-minimisation methods and taking (Mg, Al)/P ordering into account predicts the true space group to be P6/mcc. Calcined Mg-DAF-1 is shown by IR spectroscopy of adsorbed pyridine to possess mild Bronsted and Lewis acidity of strength similar to MgAPO-5 but much weaker than MgAPO-36. This is reflected in the results of isobutane conversion, where DAF-1 and MgAPO-5 give a high selectivity to butenes and propene with few of the saturated hydrocarbons typical from strong acids such as MgAPO-36 and H-ZSM-5. The higher conversion rate of isobutane over DAF-1 than over MgAPO-5 is due to the higher concentration of acid sites within the former.

Type:Article
Title:SYNTHESIS, CHARACTERIZATION AND CATALYTIC PERFORMANCE OF THE SOLID ACID DAF-1
Keywords:ALUMINOPHOSPHATE MOLECULAR-SIEVES, CONVERSION, ISOBUTANE, MECHANISM, CRACKING
UCL classification:UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Chemistry

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