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Bio-oil derived from the pyrolysis of lignocellulosic biomass residues cannot be used directly as biofuel due to the high content of oxygenated compounds. As an alternative, bio-oil must undergo a deoxygenation process, such as catalytic hydrodeoxygenation (HDO). In this sense, this work studied the effect of different concentrations of Ce3+ and Ce4+ in layered double hydroxides (LDHs) in order to obtain mixed oxide catalysts containing NiAlCe (NiO-NiAl2O4-CeO2) with low cost and high performance for the hydrodeoxygenation of anisole as a model bio-oil compound. Mixed oxides were obtained from the thermal decomposition of layered double hydroxides (LDHs) by using terephthalic acid as compensation anion, with molar ratio: Ni2+/(Al3++ M) = 1.0, where M = Ce3+; Ce4+ or Ce3+-Ce4+; and Al/Ce ratios of 9 and 1. Characterization analyses confirmed the formation of LDHs for all materials, although at lower Al/Ce ratio it is observed a loss of crystallinity, due to a greater repulsion and distortion of the layer structure caused by the incorporation, in greater amount, of cations with a high ionic radius. The increase in the content of cerium in mixed oxides also led to an increase in the acidity of the catalysts, in addition to a reduction in the surface area, justified by the pore blockage by CeO2 on the catalyst surface. The greater structural and thermal stability was evidenced in the LDHs derived from Ce4+, as well as a greater dispersion of the NiO phase in the corresponding mixed oxides, and therefore presenting greater anisole conversion. The obtained data indicated that the presence of Ce4+ ions on the catalyst surface was decisive in the conversion of anisole to cyclohexane, the main deoxygenated product, obtained via the direct deoxygenation and hydrogenation mechanism.

This work reports on obtaining iron phosphate-supported from activated carbon derived from the acai fruit (Euterpe oleracea Mart.) waste, with H3PO4 and Fe(NO3)2 as precursors. The samples were well-prepared by thermal decomposition at 400 °C (CP-400) and 500 °C (CP-500) with biomass, phosphoric acid, and iron nitrate ratio of 1:1:1 (wt/wt/wt). We characterized the products by X-ray diffraction, confirming the phase mixture of Fe(PO3)3 metaphosphate (P21/n), Fe2P4O12 tetrametaphosphate (C2/c), and amorphous carbon. All active modes were identified for biomass and iron phosphates in infrared spectroscopy. SEM images showed several irregular agglomerates formed by iron phosphate in both samples, where carbon (C), oxygen (O), iron (Fe), and phosphorus (P) were detected in the EDX analysis. The resulting N2 adsorption/desorption obtained isotherms were classified as type I (CP-400) and II (CP-500), with a surface area of 303 m2 g−1 and 206 m2 g−1, respectively. The adsorption of methylene blue dye (MB) in the aqueous solutions of composites CP-400 and CP-500 were 40 mg g−1 and 50 mg g−1, respectively. The photo-Fenton reaction using these composites as solid catalysts showed 99.6% of discoloration for CP-400 and 97.5% for CP-500, at 240 min under UV-light.

This work presents the physicochemical characterization and activity of zirconia-supported silver catalysts for the oxidation of pollutants present in diesel engine exhaust (propane, propene, naphthalene and soot). A series of silver-supported catalysts AgxZ (x = 1, 5 and 10 wt.%, Z = zirconia) were prepared, which were studied by various characterization techniques. The results show that silver is mainly found under the form of small metal nanoparticles (&lt, 10 nm) dispersed over the support. The metallic phase coexists with the AgOx oxidic phases. Silver is introduced onto the zirconia, generating Ag&ndash, ZrO2 catalysts with high activity for the oxidation of propene and naphthalene. These catalysts also show some activity for soot combustion. Silver species can contribute with zirconia in the catalytic redox cycle, through a synergistic effect, providing sites that facilitate the migration and availability of oxygen, which is favored by the presence of structural defects. This is a novel application of the AgOx&ndash, Ag/ZrO2 system in the combustion reaction of propene and naphthalene. The results are highly promising, given that the T50 values found for both model molecules are quite low.

The production of biodiesel from acidic non-edible oil and waste lipid feedstocks has the drawback of forming soaps in the conventional transesterification process. A solution is the esterification reaction that uses superacid homogenous catalysts; however, it generates dangerous effluents. To overcome this, heterogeneous acid catalysts such as heteropolyacid supported on activated carbon have been studied for the production of biofuel. Due to its high surface area, the activated carbon allows high dispersion of the active phase. The aim of this work was to study the esterification of oleic acid over 12-tungstophosphoric acid (HPW) supported on activated carbon derived from passion fruit biomass (ACP), prepared by chemical activation using ZnCl2. The composites (HPW/ACP) were prepared containing 10–30 wt% of HPW by following two procedures: aqueous impregnation method and incipient moisture. The results showed that the activated carbon prepared from the residue of the passion fruit seed presented a high surface area (465 m2. g−1) and that the HPW impregnation method on activated carbon was a decisive factor on the catalyst performance. XPS, SEM, NMR and N2 adsorption-desorption results showed that in the catalyst obtained by aqueous impregnation (HPW/ACP) surface area decreased (50 m2 g−1), HPW was highly dispersed in the internal pores of the ACP support and presented superior acidity. The incipient moisture impregnation (HPW/IACP) formed HPW particles on the external surface of the support with little interaction among them, resulting in surface area of 90 m2 g−1. The best result of oleic acid esterification with methanol led to 86.4% conversion with catalyst HPW30/ACP, at 100 °C, after 2 h of reaction. The leaching of HPW active phase after the reaction was low ∼1.0–2.6%. This study showed the importance of the HPW impregnation method on activated carbon to obtain a more stable and more active catalyst for the production of biodiesel. A detailed analysis of the catalyst synthesis from a fruit industry residue demonstrated the possibility of operating in a closed-loop system towards cleaner production.