Release of hydrogen from nanoconfined hydrides by application of microwaves

Abstract

The release of hydrogen from solid hydrides by thermolysis can be improved by nanoconfinement of the hydride in a suitable micro/mesoporous support, but the slow heat transfer by conduction through the support can be a limitation. In this work, a C/SiO 2 mesoporous material has been synthesized and employed as matrix for nanoconfinement of hydrides. The matrix showed high surface area and pore volume (386 m²/g and 1.41 cm³/g), which enabled the confinement of high concentrations of hydride. Furthermore, by modification of the proportion between C and SiO 2 , the dielectric properties of the complex could be modified, making it susceptible to microwave heating. As with this heating method the entire sample is heated simultaneously, the heat transfer resistances associated to conduction were eliminated. To demonstrate this possibility, ethane 1,2diaminoborane (EDAB) was embedded on the C/SiO 2 matrix at concentrations ranging from 11 to 31%wt using a wet impregnation method, and a device appropriate for hydrogen release from this material by application of microwaves was designed with the aid of a numerical simulation. Hydrogen liberation tests by conventional heating and microwaves were compared, showing that by microwave heating hydrogen release can be initiated and stopped in shorter times.

Unconventional Approaches to Hydrogen Sorption Reactions: Non‐Thermal and Non‐Straightforward Thermally Driven Methods

“…Depending on the dielectric properties of materials, the interaction of charged particles or polar molecules with the electric field part of the electromagnetic produces radiation heat . Several investigations have been carried out on the possibility of using such effects to drive the hydrogen desorption process and the effectiveness of microwave radiation varies as function of the hydrides. For example, no temperature increase was observed for simple ionic hydrides (LiH, NaH, MgH 2 and CaH 2 ) while metallic hydrides such as TiH 2 is heated to 327 °C upon a 3.5 min microwave irradiation .…”

Advances in Microwave-assisted Heterogeneous Catalysis

“…74,75,78 In the case of multiphase systems, several simplifications are needed to effectively manage the complexity of the system and obtain results at a reduced computational cost. For example, some studies are available in which a multiphase fixed bed reactor, constituted by large uniformly arranged particles, 29 biphasic solid hydrides 79 and zeolites, 63,80 was considered a continuum, and in the simulations the experimentally measured effective permittivity of the sample was employed. However, these simplifications should be carefully chosen since they can introduce large uncertainties in model predictions, which can lead to uncertainties in the reactor design.…”

Electrified Hydrogen Production from Methane for PEM Fuel Cells Feeding: A Review

“…In the case of multiphase systems, several simplifications are needed to effectively manage the complexity of the system and obtain the results in a reduced computational cost. For example, some studies are available in which a multiphase fixed bed reactor, constituted by uniformly arranged large particles [43], biphasic solid hydride [84] and zeolites [45,85], was considered a continuum, and in the simulations the experimentally measured effective permittivity of the sample was employed. However, these simplifications should be carefully chosen, since they can introduce large uncertainties in the model predictions, which can result in uncertainties for the reactor design.…”