Abstract
Non-coking stable alkaline earth metal (M = Mg, Sr, and Ba) modified Ga-NaY catalysts were prepared by ionic-exchange and tested in oxidative dehydrogenation (ODH) of n-octane using air as the source of oxygen. The role of the alkaline earth metals in NaY was to poison the acid sites while enhancing the basic sites responsible for ODH. The exception was the calcium modified NaY, which was more acidic than the parent NaY, coking and unstable under the ODH conditions used in this study. The role of gallium was to enhance the dehydrogenation pathway and improve the stability of NaY. The sequence of increasing selectivity to octenes followed the order: CaGa-NaY < Ga-NaY< MgGa-NaY < SrGa-NaY < BaGa-NaY. The highest octene selectivity obtained was 37% at iso-conversion of 6 ± 1% when BaGa-NaY was used at a temperature of 450 °C. The activity of the catalysts was directly proportional to the reducibility of the catalysts, which is in agreement with expectations.
Highlights
Oxidation, cracking, dehydrogenation, dehydrocyclization, and oxidative dehydrogenation are possible reactions that can activate paraffins using heterogeneous catalysts
The closeness of the total basicity is relative to the alkaline earth metals used, which all of them belong to the same group and contain the same charge, there is a noticeable change in basicity as you go down thesame periodic table, with barium more change basicityinwhich is consistent our the charge, there showing is a noticeable basicity as you gowith down thefindings
To determine the amount of alkaline earth metal that can be efficiently exchanged in Ga-NaY and still give a material with appreciable activity, three catalysts of different Ba concentrations were tested in the activation of n-octane
Summary
Oxidation, cracking, dehydrogenation, dehydrocyclization, and oxidative dehydrogenation are possible reactions that can activate paraffins using heterogeneous catalysts. More recent developments have led to the introduction of oxygen to the DH reaction, which rendered the process exothermic, with much reduced thermodynamic limitations and reduced coke deposition on the catalyst This is the reason why oxidative dehydrogenation (ODH) would be the preferred reaction in the petrochemical industry [9,10]. The reaction mechanism associated with this type of catalyst is the Mars-van Krevelen mechanism, which involves the abstraction of lattice oxygen by the alkane to form the corresponding alkene and water The limitations of these mentioned systems, which include low surface area leading to active metal agglomeration, low thermal stability, and complicated synthesis procedures which can hinder reproducibility, leave considerable room for improvement. NaY zeolite modified with gallium in conjunction with alkaline earth metals, looking at the influence on the acidity and reducibility which in turn affects the activity and stability of the catalyst
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
