Dielectric barrier discharge (DBD) plasma technology is a promising method for producing methanol from CO ₂ hydrogenation as the reaction can be run at atmospheric pressure and temperatures below 100 °C. The choice of the catalyst is crucial and has to be made not only according to its activity and selectivity towards the desired product, but its effect on plasma properties. In this work, the influence of several important catalytic properties of DBD plasma such as the dielectric constant of the catalyst and ionic conductivity is studied. The effects of the catalyst support and the addition of promoters on CO ₂ hydrogenation under DBD plasma are also studied. To this end, Cu and Cu–ZnO catalysts supported on γ -Al ₂ O ₃ and a template-free seedless ZSM-5 (Si/Al molar ratio of 23) were prepared to study their catalytic performance on CO ₂ hydrogenation into methanol under DBD plasma. These catalysts were fully characterized by XRD, SEM, N ₂ physisorption, temperature programmed reduction and in situ FTIR CO adsorption. The relative complex permittivity of the catalysts was measured and the ionic conductivity was estimated using a modified Debye model. In this paper, the role of the ionic conductivity of the catalyst was identified as a crucial parameter in plasma-assisted CO ₂ hydrogenation. It was found that the lower the value of the ionic conductivity, the better the CO ₂ conversion. Indeed, high ionic conductivity reduces the density of the plasma and decreases the dissociation of CO ₂ . The highest CO ₂ conversion value (34.0%) was observed for the nonconductive alumina support, whereas the highest methanol yield (0.5%) was observed for the zeolite-supported Cu–ZnO catalyst.

IR spectroscopy has been extensively employed to characterize the structural and vibrational properties of carbonates; yet, its application in studying the adsorption capacity of carbonate surfaces remains limited.

Ethylene stimulates ripening and senescence by promoting chlorophyll loss, red pigment synthesis, and softening of tomatoes and diminishes their shelf-life. The aim of this work was to study the performance of a novel copper- and zinc-based ethylene scavenger supported by ion-exchange on a naturally occurring zeolite by analyzing its ethylene adsorption capacity and the influence of ethylene scavenging on quality attributes during the postharvest life of tomatoes. The influence of copper- and zinc-modified zeolites on ethylene and carbon dioxide concentrations and postharvest quality of tomatoes was compared with unmodified zeolite. Interactions among ethylene molecules and zeolite surface were studied by diffuse reflectance infrared Fourier transform spectroscopy in operando mode. The percentage of ethylene removal after eight days of storage was 57% and 37% for the modified zeolite and pristine zeolite, respectively. The major ethylene increase appeared at 9.5 days for the modified zeolite treatment. Additionally, modified zeolite delayed carbon dioxide formation by six days. Zeolite modified with copper and zinc cations favors ethylene removal and delays tomato fruit ripening. However, the single use of unmodified zeolite should be reconsidered due to its ripening promoting effects in tomatoes at high moisture storage conditions, as water molecules block active sites for ethylene adsorption.

Ourin situ operandoIR DBD cell makes it possible to study the surface species formed in a plasma-catalytic system.