7. Conclusions
In this work, recent advances in catalytic CO2 hydrogenation to methanol are comprehensively discussed. Since 2003,
much effort is focused on investigating the efficacy of Cuand Pd-based catalysts. It is found that the performance
of CuO/ZnO/ZrO2 catalysts prepared by novel routes such
as solid-state reaction, urea-nitrate combustion and reverse
co-precipitation under ultrasound irradiation is promising.
CuO/ZnO-based catalysts promoted with Pd and Ga are especially useful. As a result of Pd incorporation, methanol yield
is enhanced. The presence of Ga2O3 promoter enhances the
activity, selectivity and stability of CuO/ZnO. Among the Pdbased catalysts, Pd/ZnO catalysts supported on multi-walled
carbon nanotubes show excellent performance for CO2hydrogenation to methanol. The addition of Ga to Pd/SiO2results in
unusually high catalytic behaviour.
The reaction pathway of catalytic CO2 hydrogenation to
methanol is discussed. Commonly, two reaction routes to
methanol are described in literature: first, a reverse WGS
via CO2decomposition to CO, and second, the well-regarded
mechanism via a formate intermediate. There are a few reactor innovations recently described in literature; among these,
the zeolite membrane reactor which combines catalytic reaction with the separation properties of zeolite membranes is
attractive. Finally, alternate catalytic techniques to methanol
synthesis are discussed, and the CAMERE (CO2hydrogenation
to form methanol via a reverse WGS reaction) process seems
to be a promising option.