Propylene Oxidation over Poly(azomethines) Doped with Heteropolyacids
Wincenty Turek , Edyta Stochmal-Pomarzańska , Adam Proń , Jerzy Haber
AbstractKinetic studies of propylene oxidation and isopropanol conversion were undertaken using new catalytic systems, namely, conjugated polymer-supported heteropolyacid catalysts. Unsubstituted and dimethoxy-substituted aromatic poly(azomethines) (PPI and PMOPI) were used as matrices to which selected heteropolyanions (HPAs) were introduced via acid–base-type doping which consists of protonation of imine nitrogen. PPI was synthesized via polycondensation of 1,4-phenylenediamine with terephthaldehyde, whereas PMOPI was prepared via the reaction of 1,4-phenylenediamine with 2,5-dimethoxyterephthaldehyde. Protonation of PPI and PMOPI with heteropolyacids—H3PW12O40 and H3PMo12O40—was carried out in the acetonitrile solutions. The protonation level was controlled by changing the starting molar ratio of HPA : polymer in the reaction medium. Both poly(azomethines) in their base forms and protonated poly(azomethines) were characterized using X-ray diffraction and various spectroscopic methods (FTIR, Raman, XPS). Thermal stability and BET surface area were also studied. X-Ray diffraction patterns show that HPA introduced into the polymer matrices is molecularly dispersed and does not form a separate phase. FTIR studies prove that the structural identity of individual heteropolyanions is preserved on introduction into the polymer matrices. However, Raman studies prove that protonation leads to changes in polymer chain conformation. In the oxidation of propylene the PPI(HPA)y and PMOPI(HPA)y catalysts give hexadiene as the main reaction product. Introduction of HPA into the polymer matrices changes the selectivity of the acid since the reaction carried out in the presence of crystalline H3PMo12O40 results in acrolein as the main product. For all catalysts studied, only products of nondestructive oxidation can be detected (hexadiene, acrolein, propionaldehyde, acetone, benzene).
|Journal series||Journal of Catalysis, ISSN 0021-9517|
|Publication indicators||= 34; = 32; = 54.0; : 2000 = 2.132; : 2006 = 4.533 (2) - 2007=5.11 (5)|
|Citation count*||54 (2020-09-15)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.