Acidity control of zeolite functionality on activity and stability of hybrid catalysts during DME production via CO2 hydrogenation

The catalytic behaviour of a CuZnZr-FER hybrid catalyst was assessed in the direct CO2-to-DME hydrogenation
reaction, considering the effects of structural and surface properties induced on the system by homemade
ferrierite samples at different acidity and grain size. Notwithstanding a comparable initial activity under the
adopted experimental conditions (TR=220-260°C; PR=3.0MPa; GHSV=8800 NL/kgcat/h), the investigated
catalyst samples exhibited a different behaviour in terms of stability, with a progressive decay with time mostly
marked on the hybrid containing ferrierite at larger acidity. Irrespective of the zeolite grain size, TEM analysis
showed a low tendency of catalysts to form carbon deposits, while the comparison of surface properties of "fresh"
and "used" samples evidenced a significant metal sintering occurring during reaction, proportional to the Si/Al
ratio. The loss of metallic surface area was mainly connected to water formation, as proved in the measurements
at high contact time in which a larger net drop between initial and final DME yield, resulting from a higher partial
pressure of water, was recorded.