Browsing by Author "Widyaparaga, Adhika"

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    Reactivity and Stability of Natural Clay Minerals with Various Phyllosilicate Structures as Catalysts for Hydrothermal Liquefaction of Wet Biomass Waste
    (2023) Sudibyo, Hanifrahmawan; Cabrera, Daniela V.; Widyaparaga, Adhika; Budhijanto, Budhijanto; Celis, Crispin; Labatut, Rodrigo
    We evaluated natural clay minerals representing all classesofphyllosilicates as in situ catalysts for hydrothermal liquefaction(HTL) of anaerobically digested cattle manure at 350 & DEG;C for 1h, i.e., kaolinite, montmorillonite, talc, vermiculite, phlogopite,meixnerite, attapulgite, and alumina. The relative compositions ofstrong Bronsted (SBrA), strong Lewis (SLA), and weak Lewis acidic(WLA) sites and the strong (SBS) and weak (WBS) basic sites of clayminerals significantly affected the formation of HTL products (i.e.,biocrude oil, hydrochar, and aqueous- and gas-phase coproducts) andthe distribution and speciation of elements. The general mechanisticroles of these active sites are as follows: (1) SBrA catalyzed thebiocrude-forming reactions and inhibited the hydrochar-repolymerizingreactions; (2) SLA promoted the production of hydrochar precursors;(3) WLA enhanced the hydrodeoxygenation, hydrodenitrogenation, andhydrodesulfurization of biocrude by utilizing the hydrogen generationcatalyzed by WBS; and (4) SBS increased the production of organicacids solubilizing nutrients into the aqueous-phase coproduct (HTL-AP).Montmorillonite was the most suitable for the HTL catalyst due tothe optimal composition of these active sites, leading to achievingmaximal biocrude energy recovery (i.e., 82%) with low heteroatomscontent (i.e., 15% O, 0.24% N, and 0.08% S), minimal hydrochar yield(i.e., 10%), and maximal nutrient yield in HTL-AP, i.e., 71% P, 54%Mg, 29% NH3-N, and 14% Ca. In addition, the crystallinestructure of montmorillonite remained intact after the HTL process.This study informs comprehensive catalytic roles of different surface-activesites of clay minerals useful for future development of clay-basedcatalysts for more sustainable overall HTL systems.
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    Syngas production from phenolic pollutants via a series of hydroxylation, ring cleavage, and aqueous-phase reforming catalyzed by a hydrotalcite-supported Fe-Mn-Ni alloy
    (2024) Sudibyo, Hanifrahmawan; Cabrera, Daniela V.; Labatut, Rodrigo; Supriyanto, Calvin J.; Budhijanto, Budhijanto; Widyaparaga, Adhika
    A trifunctional catalyst facilitating a series of hydroxylation, oxidative ring opening, and aqueous-phase reforming reactions was developed to convert phenolic wastewater into syngas. The definitive screening design experiment at 250 degrees C for 5 h with 1.75% H(2)O(2 )and 2 wt% catalyst loading demonstrated the importance of Fe, Mn, and Ni among the first-row transition metals to be impregnated into hydrotalcite to acquire the trifunctional feature. The surface chemistry characterization revealed that they improved the amount of strong and weak Br & oslash;nsted (SBrA and WBrA) and Lewis (SLA and WLA) acidic active sites. The mechanistic roles of these sites via semi-continuous kinetic investigation at 200-300 degrees C for 1-5 h with 1.75% H2O2 and 2 wt% catalyst loading were unraveled: (1) SBrA (surface metal oxyhydroxides) facilitated hydroxylation and homolytic cleavage producing hydroxyphenols; (2) WBrA (surface metal hydroxides) promoted ring opening of hydroxyphenols yielding oxo- and di-carboxylic acids; (3) WLA (mineral phase with a tetrahedral coordination) catalyzed reforming of acids into syngas; and (4) SLA (mineral phase with an octahedral coordination) improved the H2 yield by promoting the water-gas shift reaction. The optimal content of Fe, Mn, and Ni was 49.4, 21.2, and 29.4 wt%, respectively, from 20 wt% of active metals on the support to achieve the maximal organic carbon removal (similar to 82%) and H2 yield (similar to 80%) with a CO-to-H2 ratio of 0.6, useful for chemical building block synthesis. The optimized catalyst demonstrated high activity and reusability, with a turnover number and frequency of similar to 1 x 106 and similar to 6 x 104 s-1, respectively, marking a breakthrough in sustainable syngas production.