722
Several routes were proposed and currently being utilized to convert such crude
glycerol to produce a variety of industrially important chemical additives [1].
Therefore, the utilization of crude glycerol for the production of alkylpyrazines is
the main topic in this book chapter.
To the best of our knowledge, we have developed a route for the first time to
synthesize 2-methylpyrazine (2MP) via vapor-phase reaction by using ethylenediamine (EDA) and crude glycerol by dehydrocyclization over a mixed oxide catalyst
composed of ZnO-ZnCr 2 O 4 (Zn-Cr) derived from HTlc (as shown in Scheme 1) [2].
2MP is a key intermediate substance for the synthesis of 2-amidopyrazine is a
well-known antitubercular and bacteriostatic drug. Commercially, 2MP was prepared by dehydrocyclization of EDA and 1,2-propylene glycol (PG) over
Pd-promoted Zn-Cr catalyst (as shown in Scheme 2) [3].
In our previous reports, the effect of the acid-base properties of the Zn-Cr catalyst was investigated for product distributions during the synthesis of Zn-Cr HT
precursors by changing their pH [4]. It was noticed that the acid-base characteristics
of Zn-Cr catalyst significantly affect the 2MP selectivity. The Zn-Cr catalyst precursor synthesized at pH = 7 and exhibited enhanced selectivity toward pyrazine due to
more acidic nature via the cyclization of EDA. In contrast, the catalyst that contains
both weak acidity and basicity sites showed high 2MP selectivity. In comparison,
high specific rate of 2MP was observed over the Zn-Cr catalyst prepared at pH ∼9
[5]. Under these experimental conditions, it is also quite possible that the ethylenediamine undergoes intermolecular cyclization to form pyrazine as a by-product
(Scheme 3).
In our previous studies, the effect of catalyst calcination temperature on physicochemical characteristics of Zn-Cr catalyst and their influence on reaction
Scheme 1 Synthesis of 2MP via glycerol dehydrocyclization over Zn-Cr catalysts
Scheme 2 Synthesis of 2MP by using EDA and PG over Pd-based Zn-Cr catalyst
Scheme 3 Intermolecular
cyclization of EDA to form
pyrazine
R. Sarkari et al.
Several routes were proposed and currently being utilized to convert such crude
glycerol to produce a variety of industrially important chemical additives [1].
Therefore, the utilization of crude glycerol for the production of alkylpyrazines is
the main topic in this book chapter.
To the best of our knowledge, we have developed a route for the first time to
synthesize 2-methylpyrazine (2MP) via vapor-phase reaction by using ethylenediamine (EDA) and crude glycerol by dehydrocyclization over a mixed oxide catalyst
composed of ZnO-ZnCr 2 O 4 (Zn-Cr) derived from HTlc (as shown in Scheme 1) [2].
2MP is a key intermediate substance for the synthesis of 2-amidopyrazine is a
well-known antitubercular and bacteriostatic drug. Commercially, 2MP was prepared by dehydrocyclization of EDA and 1,2-propylene glycol (PG) over
Pd-promoted Zn-Cr catalyst (as shown in Scheme 2) [3].
In our previous reports, the effect of the acid-base properties of the Zn-Cr catalyst was investigated for product distributions during the synthesis of Zn-Cr HT
precursors by changing their pH [4]. It was noticed that the acid-base characteristics
of Zn-Cr catalyst significantly affect the 2MP selectivity. The Zn-Cr catalyst precursor synthesized at pH = 7 and exhibited enhanced selectivity toward pyrazine due to
more acidic nature via the cyclization of EDA. In contrast, the catalyst that contains
both weak acidity and basicity sites showed high 2MP selectivity. In comparison,
high specific rate of 2MP was observed over the Zn-Cr catalyst prepared at pH ∼9
[5]. Under these experimental conditions, it is also quite possible that the ethylenediamine undergoes intermolecular cyclization to form pyrazine as a by-product
(Scheme 3).
In our previous studies, the effect of catalyst calcination temperature on physicochemical characteristics of Zn-Cr catalyst and their influence on reaction
Scheme 1 Synthesis of 2MP via glycerol dehydrocyclization over Zn-Cr catalysts
Scheme 2 Synthesis of 2MP by using EDA and PG over Pd-based Zn-Cr catalyst
Scheme 3 Intermolecular
cyclization of EDA to form
pyrazine
R. Sarkari et al.