Europium Oxybromide Catalysts for Efficient Bromine Looping in Natural Gas Valorization

Abstract

The industrialization of bromine-mediated natural gas upgrading is contingent on the ability to fully recycle hydrogen bromide (HBr), which is the end form of the halogen after the activation and coupling of the alkanes. Europium oxybromide (EuOBr) is introduced as a unique catalytic material to close the bromine loop via HBr oxidation, permitting low-temperature operation and long lifetimes with a stoichiometric feed (O :HBr=0.25)-conditions at which any catalyst reported to date severely deactivates because of excessive bromination. Besides, EuOBr exhibits unparalleled selectivity to methyl bromide in methane oxybromination, which is an alternative route for bromine looping. This novel active phase is finely dispersed on appropriate carriers and scaled up to technical extrudates, enhancing the utilization of the europium phase while preserving the performance. This catalytic system paves the way for sustainable valorization of stranded natural gas via bromine chemistry.

Olefins from Natural Gas by Oxychlorination

“…Mercury porosimetry indicated the preservation of the meso and macroporosity of the extrudate (see Figure S12). X‐ray photoelectron spectroscopy of the samples evidenced the presence of Eu 2+ on the catalytic surface, which increased slightly after being exposed to the reaction environment (see Figure S12), thus suggesting that Eu 3+ /Eu 2+ is an active redox couple, in line with other studies on europium‐based catalysis …”

“…Herein, we have investigated the gas‐phase oxychlorination of ethane and propane under variable reaction conditions over different catalytic families, including, cerium oxide (CeO 2 ), vanadyl pyrophosphate ((VO) 2 P 2 O 7 ), titanium oxide (TiO 2 ), iron phosphate (FePO 4 ), and europium oxychloride (EuOCl). The oxide and phosphate systems were selected based on their good activity and stability in methane oxyhalogenation, while the choice of EuOCl was based on a previous study revealing its promising performance in ethylene oxychlorination to give vinyl chloride, and on a recent report of EuOBr for methane oxybromination to give methyl bromide and HBr oxidation to Br 2 . The catalysts were compared by evaluating the product distribution obtained in the oxychlorination of ethane and propane at about 20 and 15 % alkane conversion, respectively (Figure a,b; see Figure S1 in the Supporting Information), obtained by adjusting the reaction temperature.…”

Catalytic halogenation of methane: a dream reaction with practical scope?

“…[15][16][17][18][19] The implementation of this technology is contingent on the full recycling of the hydrogen halide (HX) formed in the halogenation and coupling steps and the ability to maximize the productivity of CH 3 X over polyhalomethanes and its coupling efficiency. 1,20 The recent decade demonstrated significant progress in HX recovery via cataloreactant systems, 21,22 electrochemical and thermochemical HX oxidation, [23][24][25][26] and methane oxyhalogenation, [26][27][28] as well as CH 3 X coupling, [16][17][18][19] which brought this technology closer than ever to practical implementation. In contrast, the selective monohalogenation was tackled in a much less depth.…”

An Activated TiC–SiC Composite for Natural Gas Upgrading via Catalytic Oxyhalogenation

“…These results suggest the beneficial effect of the embedment of the in situ generated TiO 2 in the thermally conductive SiC matrix. By comparing to the best benchmark catalysts, that is, CeO 2 for MOC and EuOX for both MOB and EOC, the performance of TiC–SiC was inferior. Nevertheless, this material represents an interesting alternative owing to its high thermal conductivity, low price particularly in relation to EuOX, and its availability as a commercial technical catalyst.…”

“…In particular, oxyhalogenation, comprising the reaction of a hydrocarbon with O 2 and a hydrogen halide (HX, X=Cl, Br), has been demonstrated as a promising strategy for the selective functionalization of natural gas to yield methyl halides (CH 3 X) or olefins. Various materials based on europium oxyhalides (EuOX), cerium oxide (CeO 2 ), and titanium oxide (TiO 2 ) have been identified to efficiently catalyze these reactions . Particularly, in the case of methane oxyhalogenation, the superior performance of these materials was related to their balanced redox properties, enabling the oxidation of HX, an important step for activity, while suppressing the oxidation of the desired methyl halides .…”