Dimethyl Ether Hydrolysis over WO3/γ-Al2O3 Supported Catalysts

Abstract

Dimethyl ether (DME) is considered an alternative hydrogen carrier with potential use in fuel cells and automotive and domestic applications. Dimethyl ether hydrolysis to methanol is a thermodynamically limited reaction catalyzed by solid-acid catalysts, mainly Al2O3 and zeolites. Moreover, it is the rate-limiting step of the DME steam reforming reaction, which is employed for the production of hydrogen fuel for fuel cell feeding. In the present study, the performance of WO3/Al2O3 catalysts (0–44% wt. WO3) was tested in DME hydrolysis reaction. The catalysts were characterized by means of N2-physisorption, XRD, Raman spectroscopy, XPS, NH3-TPD and 2,6-di-tert-butylpyridine adsorption experiments. The reaction rate of DME hydrolysis exhibited a volcanic trend as a function of tungsten surface density, while the best-performing catalyst was 37WO3/Al2O3, with a tungsten surface density of 7.4 W/nm2, noting that the theoretical monolayer coverage for the specific system is 4–5 W/nm2. Brønsted acidity was directly associated with the catalytic activity, following the same volcanic trend as a function of tungsten surface density. Blocking of Brønsted acid sites with 2,6-di-tert-butylpyridine led to a dramatic decrease in hydrolysis rates by 40 times, proving that Brønsted acid sites are primarily responsible for the catalytic activity. Thus, the type and strength rather than the concentration of acid sites are the key factors influencing the catalytic activity.

Towards High CO2 Conversions Using Cu/Zn Catalysts Supported on Aluminum Fumarate Metal-Organic Framework for Methanol Synthesis

“…In addition, the Zn content was 3.12 and 5.77 wt% in the Cu/ZnO/AlFum MOF and 7Cu/3ZnO/AlFum MOF catalysts, respectively. This discrepancy may be attributed to high Cu dispersion in the framework of the AlFum MOF support with regions of surface enrichment, potentially leading to higher Cu content albeit it must be noted that SEM-EDX is a semi-quantitative technique and other techniques such as inductively coupled plasma optical emission spectroscopy may provide more accurate, quantitative, elemental analysis results [28,29].…”

“…EDX is a semi-quantitative technique and other techniques such as inductively coup plasma optical emission spectroscopy may provide more accurate, quantitative, elemen analysis results [28,29].…”

Recent Progress on Hydrogen Storage and Production Using Chemical Hydrogen Carriers

“…The possible schematic route of DME synthesis, transportation, and utilization is shown in Figure 1. In recent years, DME has attracted interest as a chemical hydrogen carrier [24,80,92,93]. DME has a high gravimetric H2 density (13 wt %) and a higher volumetric H2 density than liquid H2, which are equal to 86.9 kg-H2/m 3 and 70.9 kg-H2/m 3 , respectively [94].…”