Synthesis of Spinel Ferrite MFe2O4 (M = Co, Cu, Mn, and Zn) for Persulfate Activation to Remove Aqueous Organics: Effects of M-Site Metal and Synthetic Method.

Metal species and synthetic method determine the characteristics of spinel ferrite MFe2O4. Herein, a series of MFe2O4 (M = Co, Cu, Mn, Zn) were synthesized to investigate the effect of M-site metal on persulfate activation for the removal of organics from aqueous solution. Results showed that M-site metal of MFe2O4 significantly influenced the catalytic persulfate oxidation of organics. The efficiency of the removal of organics using different MFe2O4 + persulfate systems followed the order of CuFe2O4 > CoFe2O4 > MnFe2O4 > ZnFe2O4. Temperature-programmed oxidation and cyclic voltammetry analyses indicated that M-site metal affected the catalyst reducibility, reversibility of M2+/M3+ redox couple, and electron transfer, and the strengths of these capacities were consistent with the catalytic performance. Besides, it was found that surface hydroxyl group was not the main factor affecting the reactivity of MFe2O4 in persulfate solution. Moreover, synthetic methods (sol-gel, solvothermal, and coprecipitation) for MFe2O4 were further compared. Characterization showed that sol-gel induced good purity, porous structure, large surface area, and favorable element chemical states for ferrite. Consequently, the as-synthesized CuFe2O4 showed better catalytic performance in the removal of organics (96.8% for acid orange 7 and 62.7% for diclofenac) along with good reusability compared with those obtained by solvothermal and coprecipitation routes. This work provides a deeper understanding of spinel ferrite MFe2O4 synthesis and persulfate activation.

[Effect of Cu-Ce/γ-Al2O3 catalyst on bio-oil production by hydrothermal deoxygenation of stearic acid].

In order to improve the hydrothermal deoxygenation of organic acids as well as to reduce the cost, we prepared a Cu-Ce/γ-Al2O3 catalyst to study the hydrothermal deoxygenation of stearic acid in the absence of H2. The Brunauer-Emmett-Teller surface area and X-ray diffraction pattern suggest that both CuO and CeO2 exist in the Cu-Ce/γ-Al2O3 catalyst. The crystals of Cu-Ce/γ-Al2O3 were more stable compared with those of the Cu/γ-Al2O3 catalyst after 12 h of hydrothermal liquefaction at 300℃, thereby indicating a better thermal stability of the former. The presence of Cu-Ce/γ-Al2O3 catalyst could greatly improve the conversion of stearic acid (94.71%) and the yield of hydrocarbon (81.41%). A preliminary analysis of the mechanism suggests that decarboxylation is the main step in the deoxygenation during the hydrothermal liquefaction of stearic acid. The addition of Cu/γ-Al2O3 and Cu-Ce/γ-Al2O3 decreased the yield of n-heptadecane and increased the yield of n-octadecane. Besides, the yields of n-paraffins increased drastically from 0.45% to 49.72% along the series from n-nonane to n-hexadecane. Thus, the cracking reactions could be improved in the presence of Cu-Ce/γ-Al2O3, suggesting that it is an efficient deoxygenation catalyst in the hydrothermal liquefaction of organic acid. In addition, the Cu-Ce/γ-Al2O3 catalyst could help in removing the carbonyl groups, and this effectively reduced the amounts of aldehydes and ketones in the bio-oil.

Catalytic liquefaction of human feces over Ni-Tm/TiO2 catalyst and the influence of operating conditions on products.

In this study, human feces were hydrothermal liquefied and converted into biocrude over Ni-Tm/TiO2 catalyst. The influence of catalysts, reaction temperature, and holding time on the distribution of products and element content of biocrude was assessed. The biocrude yield increased to 53.16% with a reaction temperature of 330 °C, a holding time of 30 min, and adding Ni-Tm/TiO2 catalyst while the liquefaction conversion peaked at 89.61%. The biocrude had an HHV of 36.64 MJ/kg and was similar to heavy crude oil. The biocrude is rich in fatty acid amides, esters, and oxygen-containing-only heteroatom-ring compounds as well as some nitrogen-containing heteroatom-ring compounds. The main gaseous products were CO2, CH4, and C2H6. Hydrothermal liquefaction over Ni-Tm/TiO2 catalyst could be a potential method to handle human excrement treatment and produce biofuel.