Towards coupling direct activation of methane with in situ generation of H₂O₂

Abstract

Due to the explosive nature of H 2 , O 2 and CH 4 mixtures, the concept of coupling in situ synthesis of H 2 O 2 with low-temperature single-step methane conversion to methanol has not received sufficient attention.This study aimed to investigate this process using a microchannel reactor, which offers the opportunity to explore the process under a wide range of concentrations. Direct methane activation with in situ generation of H 2 O 2 was successfully demonstrated in a microcapillary containing Au-Pd nanoparticles embedded on its silica-coated walls. The effect of H 2 , O 2 and CH 4 partial pressures, H 2 /O 2 molar ratio, gas-to-liquid (G/L) ratio and liquid phase weight-hourly-space-velocity (WHSV) on the productivity and product distribution was investigated. CH 4 partial pressure had the most significant effect on the productivity, while H 2 and O 2 partial pressures influenced the productivity less. The methane activation rate was found to be correlated with the H 2 O 2 formation rate. With only O 2 or pre-formed stabilized H 2 O 2 methane activation was not found, in situ H 2

Selective Oxidation of Methane to Oxygenates using Oxygen via Tandem Catalysis

“…Due to the explosive nature of the mixture of CH 4 /O 2 /H 2 , the gas mixture needs to be diluted to guarantee safe operation, thus resulting in much lower CH 3 OH production rates. Neira d′Angelo and co‐workers developed an inherently safe washcoated microchannel reactor (Figure 5) anchored AuPd nanoparticles for selective oxidation of CH 4 to oxygenates via tandem catalysis [44] . Compared with other types of reactors, microchannel reactor offers an opportunity to study the effect of gas concentration on CH 4 oxidation under a wide range.…”

Bringing the promises of microreactors and gold catalysis to lignocellulosic biomass valorization: A study on oxidative transformation of furfural

“…The porous and supramolecular composition of PEMs creates dispersed charged surfaces that are suitable for binding the gold ions from the aqueous precursor solution. Furthermore, particle aggregation is prevented due to the surrounding polymer chains which result in dispersed and uniform nanoparticles [30]. PAA (35 wt% in H 2 O, Sigma-Aldrich) with a concentration of 10 mg/mL in DI water and PEI (50 wt% in H 2 O, Sigma-Aldrich) with a concentration of 2 mg/mL in DI water are passed through the capillary at 10 mL/h for 20 min using a syringe pump, with intermittent rinse with DI water and flushing with N 2 .…”

“…Microreaction technology offers a unique opportunity that enables investigation of the reaction over a wide window of process conditions, especially the conventionally explosive regions of the mixtures, and paves the path to the process scale-up through approaches such as numbering up and sizing up [29]. On top of that, microchannel reactors provide superior yet well-defined mass transfer characteristics that make them an ideal choice for G-L-S type of reactions [30][31][32][33]. However, to the best of the authors' knowledge, the application of microchannel reactors in oxidative esterification conversions is yet to be explored in the literature.…”

Partial Methane Oxidation in Fuel Cell-Type Reactors for Co-Generation of Energy and Chemicals

“…The methane activation with in-situ H2O2 formation was successfully demonstrated in a microcapillary containing Au-Pd nanoparticles embedded in its silica-coated walls using a microchannel reactor. The direct methane activation with in situ generation of H2O2 promoted methanol formation [32,66]. The high affinity for oxygen of gold facilitates the breakdown of H2O2 in OH•, which would be the activator of the C-H breakage [73,115,116].…”

“…All these processes can be conducted in mild conditions, such as the homogeneous catalytic process that consists of partial oxidation of methane by means of strong oxidizing species, H2SO4 [28,29] in oleum and H2O2 [6,27,[30][31][32], enhanced by metal ions, generating reactive oxygenated species.…”