Synthesis of Alcohols From Carbon Oxides and Hydrogen .7. Preparation, Activation, and Catalytic Behavior of A ZnMnCrK-oxide Catalyst

The preparation, activation, and catalytic behavior of a Zn1Mn1.1Cr1.03K2.06 oxide catalyst reported in the early literature for the synthesis of higher alcohols has been investigated by means of chemical analysis, XRD, IR, DTA-TG, SEM, surface area measurements, and flow reactor experiments. Evidence has been collected in support of the following points: (1) Reaction of basic carbonates of Zn and Mn with a solution of K2CrO4 at about 70–80 °C (final pH 8.5) occurs through a redox mechanism; drying at ≈ 100 °C of the resulting mass provides a catalyst precursor made of a core formed by a phase with a spinel structure and basic zinc carbonate covered by a shell of α-K2CrO4 and possibly KHCO3. (2) Basic Zn carbonate and KHCO3 are decomposed upon activation at 400 °C. (3) The spinel-like phase is stable under N2 upon activation at 400 °C, whereas it is transformed into a phase with a rock salt-type structure, with related ZnO segregation, upon activation at 400 °C in H2; reoxidation in air induces the reverse transformation. (4) Calcination at 1000 °C always gives rise to a phase with a tetragonal symmetry typical of ZnIIMn2IIIO4. A lumped kinetic treatment of the catalytic activity data indicates that this catalyst behaves similarly to a commercial ZnCrO catalyst impregnated with K2O, but for an overall reduction of activity due to a lower surface area. Characterization of the catalyst after the activity runs provides data very similar to those obtained from the characterization of catalyst samples activated under a reducing atmosphere