No abstract

Vapor-phase synthesis of 2-methylpyrazine (2-MP), from propylene glycol (PG) and ethylenediamine (ED), has been studied over ferrite catalysts in a temperature range of 523-773 K. The performance of MnFe 2 O 4 was observed to be better than that of Zn 1-x Mn x Fe 2 O 4 (x ) 0, 0.25, 0.5, 0.75). The reaction was determined to be almost stoichiometric, with an ∼98% conversion of PG. A maximum yield of 80% of 2-MP could be obtained at a temperature of 723 K, using a feed of ED, PG, and water (ED:PG:H 2 O molar ratio of 1:1:2) over MnFe 2 O 4 . The influence of reactant molar ratio, reaction temperature, weight hourly space velocity (WHSV), and time on stream (TOS) on the product yield has been studied. Catalyst characterization was made using X-ray diffraction (XRD), surface area measurement and ammonia desorption methods, scanning electron microscopy that has been coupled with energy-dispersive X-ray analysis (SEM-EDX), and Mo ¨ssbauer spectroscopy. Increasing the manganese content in Zn 1-x Mn x Fe 2 O 4 (x ) 0, 0.25, 0.5, 0.75, and 1) increases the paramagnetism of the samples, which seems to be responsible for enhanced activity of the catalysts as the value of x increases from 0 to 1.0. A tentative mechanism for the reaction has been proposed. It has been concluded that, similar to chromites, ferrites also can function as a dehydration/dehydrogenation catalyst.