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Subject: search.filters.subject.Catalyst deactivation

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    Biofuel upgrading via catalytic deoxygenation in trickle bed reactor: Crucial issue in selection of pressure regulator type
    (2024-01-01)
    Pongsiriyakul, Kanokthip
    ;
    Kiatkittipong, Worapon
    ;
    Lim, Jun Wei
    ;
    Najdanovic-Visak, Vesna
    ;
    Wongsakulphasatch, Suwimol
    Trickle bed reactors (TBRs) are commonly used in various chemical and associated processes. The selection of a proper back pressure regulator (BPR) is crucial for maintaining the system's upstream pressure. In this study, we investigate the impact of BPR selection on deoxygenation reaction in a TBR with two typical types of BPR, including gas-phase type back pressure regulator (Gas-BPR) and multiphase type back pressure regulator (Multi-BPR). Notably, Gas-BPR introduces interruptions and pressure drops during the sampling step, impacting the hydrogen flow rate, while Multi-BPR ensures more consistent hydrogen flow. To examine the performance of BPR systems, hydrotreating experiments were conducted at 330 °C, 50 bar of hydrogen over Ni/γ-Al<inf>2</inf>O<inf>3</inf> catalyst using crude Pongamia pinnata oil as a feedstock and refined palm olein as a benchmark. Insignificant difference in the reaction performance between Multi-BPR and Gas-BPR systems was observed when using refined palm olein. Interestingly, there was a significant difference between the two systems when feeding with crude Pongamia pinnata oil. The multi-BPR system demonstrated superior performance, achieving 100% conversion of the feedstock over a prolonged period compared to the interrupted hydrogen flow in the Gas-BPR system. Further characterization of fresh and spent catalysts using N<inf>2</inf> sorption, XRD, SEM-EDS and TGA-DTG-DSC techniques revealed that a gum and coke formation was a reason for the rapid catalyst deactivation. Furthermore, the interrupted flow in the Gas-BPR system led to substantial gum production, ultimately causing a blockage in the reactor bed. Consequently, for feedstocks with high impurities, a robust continuous flow of hydrogen is essential. Thus, the study strongly recommends selecting Multi-BPR for continuous operation in TBRs to enhance efficiency and avoid catalyst deactivation.
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    Determining the role of oxygen vacancies in palmitone selectivity and coke formation over acid metal oxide catalysts for the ketonization of methyl palmitate
    (2021-11-25)
    Guntida, Adisak
    ;
    Rattanachartnarong, Thanwarat
    ;
    Jongsomjit, Bunjerd
    ;
    Sooknoi, Tawan
    ;
    Weerachawanasak, Patcharaporn
    In the present study, TiO<inf>2</inf>, CeO<inf>2</inf>, MnO<inf>2</inf>, and ZrO<inf>2</inf> catalysts were used to investigate the catalytic performance in methyl palmitate ketonization. The reaction was accelerated by weak Lewis acid, while the oxygen vacancies promoted the palmitone selectivity. The use of various characterization techniques revealed that oxygen vacancies played an important role for trapping the hydrogen atom and inhibited its spillover. This caused the suppression of the Lewis acid transformation to new Bronsted acid. Thus, the cracking of palmitone over the new Bronsted acid was diminished, leading to the decrement of selectivity to undesired products. However, when the hydrogen atom was trapped in the oxygen vacancies, the coke deposition was dominant. This phenomenon arose because hydrogen could not suppress the deep dehydrogenation, resulting in the transformation of aliphatic coke to aromatic coke. The role of oxygen vacancies was determined, and it had the positive effect on the palmitone selectivity, whereas it raised the coke formation.
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