This review reports recent achievements in dimethyl ether (DME) synthesis via CO₂ hydrogenation. This gas-phase process could be considered as a promising alternative for carbon dioxide recycling toward a (bio)fuel as DME. In this view, the production of DME from catalytic hydrogenation of CO₂ appears as a technology able to face also the ever-increasing demand for alternative, environmentally-friendly fuels and energy carriers. Basic considerations on thermodynamic aspects controlling DME production from CO₂ are presented along with a survey of the most innovative catalytic systems developed in this field. During the last years, special attention has been paid to the role of zeolite-based catalysts, either in the methanol-to-DME dehydration step or in the one-pot CO₂-to-DME hydrogenation. Overall, the productivity of DME was shown to be dependent on several catalyst features, related not only to the metal-oxide phase—responsible for CO₂ activation/hydrogenation—but also to specific properties of the zeolites (i.e., topology, porosity, specific surface area, acidity, interaction with active metals, distributions of metal particles, …) influencing activity and stability of hybridized bifunctional heterogeneous catalysts. All these aspects are discussed in details, summarizing recent achievements in this research field.

The development of processes based on the integration of new technologies is of growing interest to industrial catalysis. Recently, significant efforts have been focused on the design of catalytic membrane reactors to improve process performance. In particular, the use of membranes, that allow a selective permeation of water from the reaction mixture, positively affects the reaction evolution by improving conversion for all reactions thermodynamically or kinetically limited by the presence of water. In this paper, how pervaporation (PV) and vapor permeation (VP) technologies can improve the catalytic performance of reactions of industrial interest is considered. Specifically, technological approaches proposed in the literature are discussed with the aim of highlighting advantages and problems encountered in order to address research towards the optimization of membrane reactor configurations for liquid biofuel production in large scale.

CO₂ hydrogenation to dimethyl ether (DME) is a promising strategy to drive the current chemical industry towards a low-carbon scenario since DME can be used as an eco-friendly fuel as well as a platform molecule for chemical production. A Cu‒ZnO‒ZrO₂/ferrierite (CZZ/FER) hybrid grain was recently proposed as a catalyst for CO₂-to-DME one-pot conversion exhibiting high DME productivity thanks to the unique shape-selectivity offered by ferrierite zeolite. Nevertheless, such a catalyst deactivates but no direct evidence has been reported of activity loss over time. In this work, CZZ/FER catalysts with different acidity levels were characterized with the FTIR technique before and after reactions, aiming to give new insights about catalyst deactivation. Results show that activity loss can be related to both (i) copper particle sintering, which decreases CO₂ activation towards methanol, and (ii) acidity loss due to H⁺/Cu²⁺ ion exchange.

Samples of Ag nanoparticles (AgNPs) in a poly-methacrylic acid (PMA) matrix have been prepared by a photo-induced reduction process. They have been widely characterized by SEM, EDX-mapping, TEM, XRD and XPS measurements. The results have shown that the morphological and microstructural characteristics of AgNPs formed in a PMA matrix depend on the Ag/PMA molar ratio. Thick films of these samples deposited on ceramic substrates have also been prepared. The formation of Ag dendritic structures has been evidenced in samples with a low Ag/PMA ratio, whereas at a higher Ag/PMA ratio the film surface was found to be highly heterogeneous, along with an increase in Ag species in the ionic form. Loading AgNPs/PMA samples with multi-walled carbon nanotubes (MWCNTs) allowed production of conductive films suitable for sensing applications. The samples synthesized were investigated as sensing materials for fabricating ammonia (NH₃) gas resistive sensors. The novel sensors developed are active at low temperature, exhibiting fast response/recovery times in a wide range of detection levels from ppm to v/v (%).