Identifying the Active Silver Species in Carbonylation of Dimethyl Ether over Ag−HMOR

High Reactivity of Dimethyl Ether Activated by Zeolite Ferrierite within a Fer Cage: A Prediction Study

The zeolite-catalyzed conversion of DME into chemicals is considered environmentally friendly in industry. The periodic density functional theory, statistical thermodynamics, and the transition state theory are used to study some possible parallel reactions about the hydrogen-bonded DME over zeolite ferrierite. The following are the key findings: (1) the charge separation probably leads to the conversion of a hydrogen-bonded DME into a dimethyl oxonium ion (i.e., DMO+ or (CH3)2OH+) with a positive charge of about 0.804 e; (2) the methylation of DME, CH3OH, H2O, and CO by DMO+ at the T2O6 site of zeolite ferrierite shows the different activated internal energy (∆E≠) ranging from 18.47 to 30.06 kcal/mol, implying the strong methylation ability of DMO+; (3) H-abstraction by DMO+ is about 3.94-15.53 or 6.57-18.16 kcal/mol higher than DMO+ methylation in the activation internal energy; (4) six DMO+-mediated reactions are more likely to occur due to the lower barriers, compared to the experimental barrier (i.e., 39.87 kcal/mol) for methyl acetate synthesis; (5) active intermediates, such as (CH3)3O+, (CH3)2OH+, CH3CO+, CH3OH2+, and CH2=OH+, are expected to appear; (6) DMO+ is slightly weaker than the well-known surface methoxy species (ZO-CH3) in methylation; and (7) the methylated activity declines in the order of DME, CH3OH, H2O, and CO, with corresponding rate constants at 463.15 K of about 3.4 × 104, 1.1 × 102, 0.18, and 8.2 × 10-2 s-1, respectively.

Antimicrobial and Virus Adsorption Properties of Y-Zeolite Exchanged with Silver and Zinc Cations

The antimicrobial activity of silver and zinc exchanged cations in Y-zeolite (Ag/CBV-600, Zn/CBV-600) is evaluated against Staphylococcus aureus (gram (+)) and Escherichia coli (gram (-)) bacteria along with their adsorption capacity for viruses: brome mosaic virus (BMV), cowpea chlorotic mottle virus (CCMV), and the bacteriophage MS2. The physicochemical properties of synthesized nanomaterials are characterized by inductively coupled plasma optical emission spectroscopy (ICP-OES), UV-Vis spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). According to the obtained results, the main species associated with the exchanged ions are Ag+ and Zn2+ cations with the concentration of around 1 atomic %. The incorporation of cations does not modify the Y-zeolite framework. The Ag/CBV-600 and Zn/CBV-600 materials show an inactivation of 90% for both gram (+) and gram (-) bacteria at 16 h at a relatively low concentration of nanomaterial (0.5 mg/mL). Moreover, the samples present good adsorption capacity for BMV, CCMV, and MS2 viruses showing adsorption higher than 40% after 2 h of interaction with the viruses. These prominent results allow the further usage of nanomaterials as an effective remedy to inhibit and reduce the spread of viruses such as SARS-CoV-2 or other gram (+) or gram (-) bacteria.

Silver-Modified Nano Mordenite for Carbonylation of Dimethyl Ether

Mordenite (H-MOR) catalysts were synthesized by a hydrothermal method, and silver-modified mordenite (Ag-MOR) catalysts were prepared by ion exchange with AgNO3 at different concentrations. The performance of these catalysts in the carbonylation of dimethyl ether (DME) to methyl acetate (MA) was also evaluated. The catalysts were characterized by Ar adsorption/desorption, XRD, ICP-AES, SEM, HRTEM, 27Al NMR, H2-TPR, NH3-TPD, Py-IR, and CO-TPD. According to the characterization results, Ag ion exchange sites were mainly located in the 8-membered ring (8-MR) channels of Ag-MOR; evenly dispersed Ag2O particles were also present. The acid site distribution was changed by the modification of Ag, and the amount of Brønsted acid sites increased in 8-MR and decreased in 12-MR. The CO adsorption performance of the catalyst significantly increased with the modification of Ag. These changes improved the conversion and selectivity of the carbonylation of DME. Over 4Ag-MOR in particular, DME conversion and MA selectivity reached 94% and 100%, respectively.