Formation of Cobalt Phyllosilicate During Solid State Preparation of Co2+/ZSM5 Catalysts from Cobalt Acetate

Abstract

When CO 2þ /ZSM5 catalysts are prepared by solid state exchange between H-ZSM5 and cobalt acetate, CO 2þ ions form layered cobalt phyllosilicate at the surface of the zeolite grains, bringing about a reassessment of the chemistry involved in the preparation of catalytic systems by solid state exchange.

Oxidation of methane to methanol and formaldehyde over Co–ZSM-5 molecular sieves: Tuning the reactivity and selectivity by alkaline and acid treatments of the zeolite ZSM-5 agglomerates

“…H 2 -TPR results can provide additional quantitative information about the cobalt species [12,[47][48][49], which will be demonstrated here for Co-ZSM-5-p ( Fig. 4A; Table 1, entry 1).…”

“…The reduction of the smaller particle might explain the reduction signal at 633 K. The peak at 1000 K is ascribed to the reduction of CoO oligomers containing Co 2+ (as for all other samples). In addition, this specific sample shows an additional peak at 1073 K, which was ascribed to the reduction of extra-framework cobalt(II) phyllosilicate [8,49] or cobalt(II) aluminate [51].…”

“…A peak at around 1000 K (T 3max ) was observed, which was assigned to the reduction of CoO oligomers containing Co 2+ [48][49][50]. Isolated Co 2+ can only be reduced above 1200 K. However, the latter temperatures could not be reached with our TPR equipment, therefore the amount of isolated Co 2+ ions was calculated as the difference between the total amount of cobalt (based on AAS) and the amount of reducible cobalt as deduced for the H 2 -TPR thermograms [48][49][50] up to a temperature of 1173 K. Table 3 summarizes the results of the quantification as obtained from the H 2 -TPR measurements. Apparently, the amount of isolated Co 2+ species decreases with increasing severity of the alkaline treatment (either by increasing the alkaline concentration or the treatment time), while the amount of cobalt oxidic species increases in the same order.…”

Partial Oxidation of Methane Over Co-ZSM-5: Tuning the Oxygenate Selectivity by Altering the Preparation Route

“…can only be reduced above 900°C. Their quantity was, in general, calculated by the difference between the total amount of cobalt and the amount of cobalt quantified based on the thermograms [29][30][31]. Table 2 presents the quantification of cobalt species using H 2 -TPR analysis.…”

Cu/ZnO aggregates in siliceous mesoporous matrices: Development of a new model methanol synthesis catalyst

“…Thus, we believe that lattice destruction due to silicate formation (mostly with zinc) is the origin of these phenomena. Lattice destruction by silicate formation has been recently observed during the preparation of Co-ZSM-5 from Co acetate (solid-state and liquid-exchange routes) [36]. Regarding copper and zinc, the interaction of the latter with the pore walls is much stronger than that of the former; Cu was found to form oxide nanoparticles in siliceous matrices, whereas zinc did not under comparable conditions [23].…”