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    Hydrogen-Free Production of Green Diesel from Deoxygenation of Methyl Palmitate via Cross-Metathesis with Bio-Ethylene Using Supported WO3 Catalyst
    (2025-06-02)
    Solehudin, Mochamad
    ;
    Wengwirat, Kanokwan
    ;
    Promchana, Pratya
    ;
    Poo-arporn, Yingyot
    ;
    Limphirat, Wanwisa
    Traditional green diesel production from used cooking oils faces challenges in H<inf>2</inf> supply and carbon loss as CO<inf>2</inf>. This study presents a novel hydrogen-free deoxygenation process via cross-metathesis between fatty acids/FAMEs and bio-ethylene under atmospheric pressure as an alternative sustainable solution. The carboxyl end group was removed as CO and blue hydrogen, bearing the hydrocarbons as green diesel, sustainable aviation fuel (SAF), and bio-naphtha. Bifunctional WO<inf>3</inf>/SiO<inf>2</inf> was prepared and characterized by XRD, XANES, EXAFS, DR-UV, and Raman. Lewis site (W = O) promotes the formation of ketene intermediate that undergoes cross-metathesis with ethylene over tungsten carbene (WCH<inf>2</inf>) sites, yielding a C16-ene majority with trace amounts of C17-ene. Smaller hydrocarbons (<C15) are obtained as minor components from decarbonylation, hydrogen transfer, and cracking. The increased contact time (27–106 g h/mol) at 460 °C results in increased conversion (30%–87 %), green diesel (12%–57%), SAF (3.5%–12.7%), and bio-naphtha (1.3%–5.3%). Optimal green diesel production of 2.92 h⁻¹ with 73% selectivity can be achieved at 480 °C. SAF and bio-naphtha yields can be tuned by varying temperature from 460 to 500 °C. This provides a sustainable pathway for renewable liquid fuels without an external hydrogen supply.
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    Selective acetylene removal from ethylene-rich feed by cross-metathesis over supported WO3 catalysts
    (2023-01-25)
    Promchana, Pratya
    ;
    Choojun, Kittisak
    ;
    Limphirat, Wanwisa
    ;
    Poo-arporn, Yingyot
    ;
    Sooknoi, Tawan
    Acetylene in ethylene-rich feed can be removed via acetylene/ethylene cross-metathesis over WO<inf>3</inf>-supported catalysts at 450 °C, yielding 1,3-butadiene with cyclohexene as a minor product. The catalyst must be treated with ethylene at 600 °C to generate a genuinely active site of tungsten (IV) alkylidene species (W=CH<inf>2</inf>). The H<inf>2</inf> treatment decreases surface W[dbnd]O concentration, and hence the activity. Raman spectroscopy shows that active single-site WO<inf>3</inf> species, including mono oxo-WO<inf>3</inf> ((O=)W(O-Si)<inf>3</inf> and (O=)W(O-Si)<inf>4</inf>) and dioxo-WO<inf>3</inf> species (O=)<inf>2</inf>W(O-Si)<inf>2</inf>) were generated in 2%WO<inf>3</inf>/SiO<inf>2</inf>, while the WO<inf>3</inf> cluster and bulk WO<inf>3</inf> exist in 3–5%WO<inf>3</inf>/SiO<inf>2</inf> and 7%WO<inf>3</inf>/SiO<inf>2</inf>, respectively. The 5%WO<inf>3</inf>/NaX and 5%WO<inf>3</inf>/NaY provide lower activity due to coke formation over the acid sites. With high surface area and confined surface silanol of 5%WO<inf>3</inf>/MCM-41% and 5%WO<inf>3</inf>/SBA-15, in situ TR-EXAFS evidences the formation of only O[dbnd]W(O-Si)<inf>3</inf>. This species provides an isolated W=CH<inf>2</inf> site with relatively higher activity and is less prone to coke formation than the WO<inf>3</inf> cluster in 5%WO<inf>3</inf>/SiO<inf>2</inf>.