Study on a Microreaction Process for Synthesis of Polyaniline

ABSTRACT

A catalytic continuous microreaction process for synthesis of polyaniline (PANI) under solar light was investigated. The polymerization of aniline was conducted via a photochemical method. The photopolymerization method yields a polymeric material that has been characterized by Fourier-transform infrared spectroscopy analysis and by scanning electron microscopy. It is shown that the functional groups and surface morphology are affected by solar incident energy where the PANI main vibrational bands become wider, resulting in higher concentration of rings. Results showed that solar intensity enhanced the average yield by 5% over that of indirect solar, while the average time of polymerization is reduced by 17%. The polymerization time was reduced by 20–​27% while the temperature was increased from 5°C​ to 25°C under indirect solar and direct solar, respectively. The yield of PANI is reduced from 94.0% to 84.2% as liquid hour space velocity (LHSV) is increased from 0.145 to 0.385 min⁻¹. An optimum molar ratio of about 1.25 is found to give the maximum yield of PANI. Kinetic analysis revealed that a pseudo-first-order Langmuir–​Hinshelwood model is well expressing the oxidation rate of aniline over TiO₂. The values of the adsorption equilibrium constant, , and the kinetic rate constant of surface reaction, , are 0.0209 and 0.791 (L⁻¹g min⁻¹), respectively. Comparison between microreactor's performance and performance of batch reactors from published literature was presented. The comparison confirmed the unique characteristics of the microreactor.

KEYWORDS:

• FTIR
• microreactor
• photocatalysis
• polymerization
• rate law
• SEM
• solar light

Acknowledgments

Authors are grateful to the Chemical Engineering Department, University of Technology, for providing space and facilities. Thanks are also due to the Iraqi Solar Energy Research Center (ISERC) for assistance.