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PhD thesis defense of Abdul Qayyum, 23 April 2024, 14:00

2024-04-19

Mr. Abdul Qayyum is a PhD candidate at the Warsaw PhD School in Natural and BioMedical Sciences. His PhD Supervisor is Prof. Dr. Eng. Juan Carlos Colmenares from the Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw, Poland.


Title of PhD thesis: Titania-based photocatalysts prepared by sonication in understanding the selective oxidation of lignin-inspired molecules to phenolics”
 

Lignin presents a significant renewable resource for aromatic compound production. Despite the vast potential, challenges persist in catalytic transformations of lignin-inspired compounds due to harsh conditions and unselective reactivity. The research work of Mr. Abdul Qayyum focuses on addressing these limitations by synthesizing novel titania-based photocatalysts with ultrasound (US) assistance, aiming to tune the physicochemical properties of the photocatalysts, leading to improved selective conversions of lignin-inspired model compounds to the corresponding high-value phenolic compounds.

US irradiation during the synthesis can lead to various physical and chemical effects, such as the enhanced mass transfer, de-passivation, formation of free radicals like hydroxyl etc., due to the nano-jets, localized hotspots where the temperature and pressure can reach up to 5000 °C and 1000 bars, respectively, which in result can tune the physiochemical features of the synthesized nanomaterials on demand. The physical and chemical effects of the US depend on the utilized frequency. Varying US frequencies and amplitudes were employed to synthesize titania photocatalysts, which were compared with samples synthesized using conventional methods. Characterization techniques, including XRD, XPS, TEM, TGA, nitrogen sorption, and diffused reflectance spectroscopy were used to characterize the synthesized photocatalysts.

The synthesized photocatalysts were studied for the additives-free photocatalytic conversion of lignin-inspired compounds like monoaromatic compound such as benzyl alcohol and diaromatic compound containing β-O-4 linkage such as 2-phenoxy-1-phenylethanol. Among the US-assisted samples, the photocatalyst prepared by low amplitude of low frequency, such as 22 kHz exhibited superior conversion rates and yields of valuable products compared to silent conditions and commercial benchmarks. Additionally, the photocatalysts displayed reusability across multiple cycles without leaching. The photogenerated holes were identified as the most reactive species for the photocatalytic reaction revealed by the scavengers studied, which led to understanding the potential mechanism of the reaction. Moreover, this research work demonstrates the greener approach by avoiding harsh experimental conditions, using additive agents, and taking energy-demanding steps.

Sonophotocatalytic studies highlighted the photocatalyst prepared using low frequency showed the enhanced selective conversion of 2-phenoxy-1-phenylethanol to corresponding phenolic compounds. This research underscores the potential of optimized US parameters in tuning the physicochemical features of the photocatalysts for improved selective redox photocatalytic performance.

In summary, this thesis showcases the efficacy of US-assisted synthesis of titania-based photocatalysts in enhancing photocatalytic activities for lignin-inspired compounds, offering insights into achieving elevated selectivity and efficiency in future catalytic applications.

PhD thesis defense of Abdul Qayyum, 23 April 2024, 14:00

  • The PhD thesis is reviewed by 
     

    • Prof. Dr. Françoise Jerome (Institut de Chimie des Milieux et Matériaux de Poitiers — IC2MP, France)
    • Prof. Dr. Janusz Ryczkowski (Department of Chemical Technology, Maria Curie-Skłodowska University, Lublin, Poland)
    • Prof. Dr. Rajender S. Varma (US Environmental Protection Agency, CINCINNATI, OHIO, USA)
       
  • Public defense of a PhD thesis will be held on April 23, 2024 (Tuesday) at 14.00
     

    • The public defense of the doctoral dissertation will be held in English via electronic means of communication, using the Zoom tool.
    • Persons from outside the IPC PAS who wish to take part in the defense should send such information no later than one day before the defense to the following address: 
    • SEKN-​RN@​ichf.​edu.​pl.

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