Catalytic properties of the framework-structured zirconium-containing phosphates in ethanol conversion

Aliphatic alcohols C1–C4 can serve as raw material for the production of essential organic products, such as olefins, aldehydes, ketones and ethers. For the develop- ment of catalysts of alcohols’ conversion, the authors considered two families of framework phosphate compounds with significant chemical, thermal and phase sta- bility: NaZr2(PO4)3 (NZP/NASICON) and Sc2(WO4)3 (SW). Variation in the com- position of zirconium-containing NZP- and SW-complex phosphates allows one to vary the number and strength of Lewis acid centers and incorporate oxidative-reduc- ing centers (such as d-transition metals) into the structure. The phosphates M0.5+xNixZr2 − x(PO4)3 (where M are Mn and Ca) were studied in the reactions of ethanol conversion. From the results of complex investigation, the compounds with M–Mn (x = 0, 0.3 and 0.5) were crystallized in the SW-type (mon- oclinic symmetry), while the phosphates with M–Ca (x = 0, 0.2 and 0.4) were char- acterized as the NZP-structured compounds (trigonal symmetry). The surface areas and pore volumes of synthesized catalysts varied, with different compositions, from 14 to 32 m2/g and 0.03 to 0.12 mL/g, respectively. From the catalytic experiments, the main direction of conversion on all the studied catalysts was ethanol dehydro- genization with acetaldehyde formation. The other conversion products—diethyl ether and ethylene—were produced with small yields. Based on the results obtained, the NZP-sample Ca0.5Zr2(PO4)3 can be considered as a selective catalyst for producing acetaldehyde at 400 °C with a yield of 55% from its theoretical amount.