The Catalyst Review June 2019 - 15

EXPERIMENTAL
Figure 1. a) The coordination environment of gallate ligand and MO6. M purple, C black, O red, H white. b) Perspective view of the structure along the c axis showing the
triangular main channels and the regular branched channels leaning against the main ones. The H atoms are omitted for clarity. c) Diagram of the fusiform branched channels.
Only ethylene can favorably enter the cavity because the limiting aperture size of M-gallate (3.47W4.85 Å2 for Ni-gallate, 3.56W4.84 Å2 for Mg-gallate, and 3.69W4.95 Å2 for
Co-gallate) matches well with the smallest cross-section size of C2H4 (3.28W4.18 b2), but is smaller than that of C2H6 (3.81W4.08 b2). The C atoms in C2H4 and C2H6 are
particularly presented in orange. d),e) Accessible Connolly surface calculated with a Connolly radius of 1.0 b. The quasi-discrete cavities of the fusiform branched channels are
restrained by the narrow pore windows. f) Diagram of the zigzag channels. The zigzag channels in different layers are colored by purple and orange, respectively.

Figure 2. a) Single-component adsorption isotherms of C2H4 (red) and C2H6 (blue) in Co-gallate at 298 K in the pressure range of 0-1 bar. Empty symbols represent desorption
data. b) Comparison of IAST selectivities for equimolar C2H4/C2H6 mixtures in M-gallate with other best-performing materials in the range of 0-1 bar. The adsorption isotherms
were collected at 318 K for FeMOF-74, 298 K for M-gallate, MgMOF-74 and zeolite 13X, 296 K for CoMOF-74, 293 K for NOTT-300, and 283 K for zeolite 5A. c) Comparison of
C2H4/C2H6 adsorption selectivity and volumetric C2H4 uptake at 1 bar in M-gallate and other best-performing materials. d) Experimental breakthrough curves of Mgallate for the
equimolar CC2H4/C2H6 mixture at 273 K and 1 bar with a constant flow rate of 0.5 mLmin-1.

Based on its readily available ligand, high stability against water vapor combined with the excellent maintenance of separation
performance, M-gallate shows significant potential in industrial practice, such as the pressure-swing adsorption process. Source: Bao
Z, Wang J, Zhang Z, et al. (2018). Angew. Chem. Int. Ed., 57: 16020-16025.
Tuning Zeolite Properties towards CO2 Methanation: An Overview...
Utilization of CO2 as feedstock has been the focus of significant attention because of its potential for achieving a more efficient
electric energy network. The efficiency of power-to-gas plants depends on the use of active, selective, and stable CO2 methanation
catalysts. Herein, the authors present a review of peer-reviewed publications using zeolite materials for CO2 methanation in which
the main conclusions of the published works are summarized, and the performances of the best-reported samples compared,
considering the limitations due to the dependence of the results on the experimental conditions.
Their work begins with an assessment of the parameters associated
with CO2 methanation over zeolite-based catalysts under thermal
conditions, namely the catalysts themselves (see Table 1 next page)
as well as mechanistic considerations. A brief treatment of CO2
methanation over zeolite-based catalysts under plasma conditions
is followed by a discussion of the relevant properties of zeolites for
CO2 methanation including, calcination temperature, pre-reduction
temperature, incorporation of promoters, and, most importantly,
resistance to the presence of water. A suggested roadmap for zeolite
applications for CO2 methanation based on the results of current
research activity (Figure 1) is then presented.

Figure 1. Main properties to guarantee in a methanation catalyst and
proposals for achieving them when using zeolite-based materials.

In summary, this overview shows the suitability of zeolites as supports
for the CO2 methanation from a fundamental point of view, as long
as their properties are adjusted to meet the requirements of the CO2
methanation. The most relevant property that zeolites need to fulfill for
The Catalyst Review

June 2019

The Catalyst Review June 2019

Table of Contents for the Digital Edition of The Catalyst Review June 2019