Study on the thermal decomposition of a copper-containing hydrotalcite-like catalytic material

The hydrotalcite like compound Cu_{0. 13}Mg_{0. 6}A_{10. 27}(OH)₂(CO₃)_{0. 135} · xH₂O (CuHTlc) are synthesized by coprecipitation method and are characterized by XRD, DTA-TG, BET, TEM and ²⁷Al MAS NMR. The results show that at relatively low calcination temperatures (below 300°C), the layer structure of CuHTlc is retained, although partial dehydroxylation in addition to dehydration occurs. At 500°C, the hydrotalcite structure is destroyed and MgO phase appears, the spinel phase forms with the further increase of calcination temperature. CuHTlc calcined at 500°C has the highest surface area (193m² · g^-1). When CuHTlc are calcined above 500°C, the composition of resusting products is Cu_{0. 13}Mg_{0. 6}Al_{0. 27}O_{0. 135}, the equation of thermal decoposition of CuHTlc can be expressed as following: Cu_{0. 13}Mg_{0. 6}Al_{0. 27}(OH)₂(CO₃)_{0. 135} · xH₂O → Cu_{0. 13}Mg_{0. 6}Al_{0. 27}O_{0. 135} + (1 + x)H₂O + 0. 135CO₂.