Effect of Various Au/Al2O3Preparations on Catalytic Behaviour during the Continuous Flow Hydrogenation of an Octanal/Octene Mixture

Heterogeneous Cu-Fe oxide catalysts for preferential CO oxidation (PROX) in H2-rich process streams

The influence of Fe loading in Cu–Fe phases and its effect on carbon monoxide (CO) oxidation in H₂-rich reactant streams were investigated with the catalyst material phases characterized by Field Emission Scanning Electron Microscopy (FESEM), X-ray diffraction (XRD) studies and Mössbauer Spectroscopy (MS). There was no change in the oxidation state of the Fe ions with copper or iron loading. The catalytic activity was examined in the feed consisting of H₂, H₂O and CO₂ for the preferential CO oxidation (PROX) process. These catalysts showed an optimized performance in converting CO in WGS streams in the temperature range of 80–200 °C. In addition to the formation of the CuFe₂O₄ phase, the Fe and Cu were found to be incorporated into a Cu–Fe supersaturated solid solution which improved CO oxidation activity, with carbon dioxide and water produced selectively with high catalytic activity in depleted hydrogen streams. Relatively high conversion of CO was obtained with high Fe metal loading. In addition to their catalytic efficiency, the employed heterogeneous catalysts are inexpensive to produce and do not contain any critical raw materials such as platinum group metals.

Fe loading in Cu–Fe phases and its effect on carbon monoxide oxidation in H₂-rich reactant streams were investigated with the catalyst material phases characterized by Field Emission Scanning Electron Microscopy, X-ray diffraction studies and Mössbauer Spectroscopy.

The effect of oxidant species on direct, non-syngas conversion of methane to methanol over an FePO4 catalyst material

The effect of the phase transformation of a FePO₄ catalyst material from the tridymite-like (tdm) FePO₄ to the α-domain (α-Fe₃(P₂O₇)₂) during the direct selective oxidation of methane to methanol was studied using oxidant species O₂, H₂O and N₂O. The main reaction products were CH₃OH, carbon dioxide and carbon monoxide, whereas formaldehyde was produced in rather minute amounts. Results showed that the single-step non-syngas activation of CH₄ to oxygenate(s) on a solid FePO₄ phase-specific catalyst was influenced by the nature of the oxidizer used for the CH₄ turnover. Fresh and activated FePO₄ powder samples and their modified physicochemical surface and bulk properties, which affected the conversion and selectivity in the partial oxidation (POX) mechanism of CH₄, were investigated. Temperature-programmed re-oxidation (TPRO) profiles indicated that the type of moieties utilised in the procedures, determined the re-oxidizing pathway of the reduced multiphase FePO₄ system. Mössbauer spectroscopy measurements along with X-ray diffraction (XRD) examination of neat, hydrogenated and spent catalytic compounds, demonstrated a variation of the phosphate into a mixture of crystallites, which depended on operating process conditions (for example time-on-stream). The Mössbauer spectra revealed the change of the initial ferric orthophosphate, FePO₄ (tdm), to the divalent metal form, iron(ii) pyrophosphate (Fe₂P₂O₇); thereafter, reactivity was governed by the interaction (strength) with individual oxidizing agents. The Fe³⁺ ↔ Fe²⁺ chemical redox cycle can play a key mechanistic role in tailored multistep design, while the advantage of iron-based heterogeneous catalysis primarily lies in being inexpensive and comprising non-critical raw resources. When compared to the other catalysts reported in the literature, the FePO₄-tdm phase catalysts showed in this work exhibited a high activity towards methanol i.e., 12.3 × 10⁻³ μmol_MeOH g_cat h⁻¹ using N₂O as an oxidant. This catalyst also showed a high activity with O₂ as an oxidant (5.3 × 10⁻³ μmol_MeOH g_cat h⁻¹). Further investigations will include continuous reactor unit engineering optimisation.

The effect of the phase transformation of a FePO₄ catalyst material from the tridymite-like (tdm) FePO₄ to the α-domain (α-Fe₃(P₂O₇)₂) during the direct selective oxidation of methane to methanol was studied using oxidant species O₂, H₂O and N₂O.

Continuous Flow Preferential Hydrogenation of an Octanal/Octene Mixture Using Cu/Al2O3 Catalysts

γ-Alumina-supported catalysts with varying copper loadings (5-25 wt %) were prepared by incipient wet impregnation and characterized by various characterization techniques. These catalysts were tested for the selective hydrogenation of octanal in a mixture containing 10 wt % octanal and 2 wt % octene diluted in octanol. The reactions were carried out in a continuous flow fixed-bed reactor in a down flow mode with varying pressures, liquid hourly space velocities, and hydrogen (H₂)-to-aldehyde molar ratios. The catalyst activities were assessed over a temperature range between 100 and 180 °C using hydrogen gas as the hydrogen source. The results obtained showed that under these experimental conditions, copper preferentially hydrogenates the aldehyde and the copper content exhibited no significant influence on the catalyst activity or product selectivity. Kinetic modeling revealed that both octanal and octene hydrogenation were first-order reactions, although octene conversion was very low until octanal conversion had reached a significant level. The activation energy for octanal hydrogenation is higher than the octene hydrogenation. A maximum octanal conversion of >99% was obtained at 160 °C, and the best selectivity toward octanol of 99% was achieved at 100 °C (53% conversion). The pressure played a small role with regards to octanal conversion and selectivity toward octanol, whereas it exhibited a significant influence on the octene conversion. Increasing the hydrogen-to-aldehyde ratio was found to have a direct influence on both octanal and octene conversion.