Products Cited in Publications Worldwide Development of catalysts for the valorization of lignin: hydrodeoxygenation of dimeric aryl ethers

Development of catalysts for the valorization of lignin: hydrodeoxygenation of dimeric aryl ethers

Rafael, Raphaela Azevedo

Abstract

The present thesis aims at studying the role of the support and metal particle size on the hydrodeoxygenation reactions (HDO) of benzyl phenyl ether (BPE), phenethoxybenzene (PEB), and diphenyl ether (DPE) chosen as model molecules representative of the main ether linkages present in the lignocellulosic biomass. The reactions were carried out in the liquid phase at 230 °C and 18 bar of H2. Pd-supported on different oxides (SiO2, TiO2, Nb2O5, Al2O3, ZrO2, and HZSM5) were synthesized by incipient wetness impregnation and deposition of metal particles prepared by the colloidal method. The acidic sites of the support promote the cracking of the C-O ether bond of BPE, but for PEB and DPE, this effect is less pronounced due to the higher energy required to break these linkages. The hydrogenolysis of the C-O ether bond takes place on the metallic Pd particles, producing the respective arenes. However, the Pd particle size can directly affect the product distribution after C-O cleavage. Due to the larger Pd particle size, impregnated catalysts favor the hydrogenolysis and exhibit a higher selectivity to alkylated products, whereas a smaller Pd particle size, obtained for catalysts prepared by the colloidal route, increases the selectivity to deoxygenated products. Over these catalysts, the formation of alkylated products is suppressed, but the hydrogenation of BPE, PEB, and DPE aromatic rings occurs in parallel to hydrogenolysis also promoted by Pd particles. The performance of Ru-based catalysts was also evaluated in the same reaction conditions. In the presence of Ru, alkylated products are produced even in the absence of acidic sites.

Keywords

Hydrodeoxygenation ; Hydrogenolysis ; Alkylation ; Ether linkage

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A35545340515-89-797%

Phenethoxybenzene

115.0/25g

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