Gas-phase dehydration of glycerol over calcined tungsten-modified Zn–Al–O hydrotalcite-type catalysts

Abstract Zinc aluminum (ZA) samples with the ratio of Zn/Al > 2 prepared by deposition of a mixed solution of aluminum and zinc nitrates with an aqueous solution of precipitant and varied by the method of modification with tungsten-containing component were characterized by XRD, FTIR, and adsorption methods and tested in the reaction of glycerol dehydration. The properties of samples were studied depending on Zn/Al ratio (ZA-2, ZA-3), the nature of precipitant: NaOH (ZA-2) or NH 4 OH (ZA-2a), and the method of modification by introducing the [W 12 O 41 ] 10− anion into the interlayer space [ZA-2 (W), ZA-2a (W)] or by deposition of PW (SiW) heteropoly acid on the surface [PW (SiW)/ZA-2 (ZA-2a)]. It was shown that dried ZA-2 sample represented a layered Zn–Al hydroxide with a structure similar to hydrotalcite; ZA-2a and ZA-3 samples contained ZnO in addition to mentioned phase. The modification of ZnAl samples with W-containing component did not change the phase composition but reduced the degree of crystallinity. The thermal treatment of the samples in the interval of 450–600 °C promoted the formation of a solid solution based on ZnO which transformed after the calcination at 900 °C into mixture of ZnO and ZnAl 2 O 4 phases. It was found that the surface of the studied samples contained both Bronsted (BAS) and Lewis acid sites (LAS). BAS concentration referred to m 2 of the surface increased in the row: ZA-2a