Abstract
Mesoporous molecular sieves, NbFAPO-5 and NbFAPSO-5 were hydrothermally synthesized with AlPO-5 type structure. Characterization of these molecular sieves was performed by X-ray diffraction to determine their structure, ICP-EAS for their elemental composition and infrared spectrometry to access their acidic properties. X-ray diffraction patterns confirmed well AlPO-5 type structure. ICP-EAS analysis confirmed the incorporation of silicon (12.9%), aluminium (15.4%), phosphorous (21.9%), iron (5.62%) and niobium (0.39%) into AlPO-5 framework. Infrared spectrometry analysis showed that both Bronsted and Lewis sites were found in the synthesized samples. The presence of both Bronsted and Lewis acid site led to bifunctional function of NbFAPO-5 and NbFAPSO-5 molecular sieve in promoting both oxidation and esterification reactions. NbFAPSO-5 Bronsted acidity was higher than that of NbFAPO-5 and for Lewis acidity, NbFAPO-5 was higher than that of NbFAPO-5.
Highlights
Catalyst technology has increasingly played a key role in the economic development of countries around the word
Hydrothermal synthesis is preferred over post synthesis because it leads to better incorporation of a wide variety of metal ion into aluminophosphate materials which are of particular interest for the design of novel catalysts
The unfavorable feature of niobium oxides, the biggest group of niobium compounds applied in heterogeneous catalysis is a low mobility and reducibility of niobium species
Summary
Catalyst technology has increasingly played a key role in the economic development of countries around the word. In recent years the isomorphous substitution in zeolite and aluminophosphate materials by other elements has been extensively studied and reviewed [2]. Isomorphous substitution of elements in these materials is carried out in order to modify their catalytic and shape selective properties. Different ways to perform such substitutions are well established either during hydrothermal synthesis or by post-synthesis methods in liquid and vapor phase [3]-[5]. Hydrothermal synthesis is preferred over post synthesis because it leads to better incorporation of a wide variety of metal ion into aluminophosphate materials which are of particular interest for the design of novel catalysts. The past decade has brought an increasing interest in niobium-containing materials, which can be applied within many fields [6]. Nb was successfully introduced into FAPO-5 and FAPSO-5 type structure leading to NbFAPO-5 and NbFAPSO-5 and their acidic properties studied
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