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Sulfur oxides, abbreviated to SOx, refer to both sulfur dioxide (SO2) and sulfur trioxide (SO3) that are gaseous pollutants emitted by the combustion of low-grade fuels, including heavy oils, sour gases and coal. Current Flue Gas Desulfurization (FGD) technologies mainly use limestone or CaO (quicklime) as sulfur scavenger. They consume water and produce significant stocks of calcium sulfate, a non-regenerable solid that has limited market outlets and is sometimes considered as waste. To tackle this problem, a multi-partner team has launched a two-phase program in order to develop a new, regenerative FGD concept. This partnership includes a GE Power team (Belfort, France), three research laboratories (IS2M-MPC, LGRE from University of Haute Alsace, Mulhouse and ICB-UTBM-LERMPS, Belfort), a ceramic material testing center (ICAR, Moncel les Luneville, France) and a consultancy organization skilled in materials (Zephir Alsace, Mulhouse). The main objective was to design a regenerable adsorbent that would not release any solid waste but would allow instead the recovery of sulfur in the form of H2SO4 (sulfuric acid) which is a valuable chemical commodity. A first subprogram, executed from September 2012 through March 2015 and called “DeSOx New Gen”, enabled the different partners to identify and test at lab scale a regenerable and durable adsorbent. This adsorbent, used initially in powder form, involved an organized mesoporous silica (SiO2), which was used as a support and was impregnated with copper oxide (CuO) likely to undergo reversible sulfation. Such binary system proved capable of achieving large numbers of successive adsorption/regeneration cycles (more than fifteen attained in the lab) without undergoing substantial activity loss. A second subprogram, initiated in September 2017 and called “AdSOx”, aimed to obtain and test a bead-shaped form of the previously developed adsorbent in view of industrial applications. This product in bead-shaped adsorbent was then evaluated in 2019 in a pilot combustion rig, the flue gases of which were representative of a real industrial combustion installation in terms of SOx, NOx, CO, CO2, H2O and PM (particulate matter). In these rig tests, the performances of the adsorbent for the capture of SOx, including its capability to be regenerated for multi-cyclic use, have been assessed in fluidized bed and most recently in fixed bed conditions. This paper outlines the most significant steps and outcomes of this collaborative two-phase development program. It also illustrates the interesting capabilities of mesoporous materials for the design of highly active sorption and catalytic systems.

The authors present a resonant permittivity measurement method which works over a large microwave frequency domain, with a very small volume sample of dielectric material. The cell is a helical resonator having many modes of resonance. The shifts of resonance frequency and Q-factors are better interpreted with a bilinear function which depends on the complex permittivity of the material than by applying the classical perturbation formula. Results concerning two different catalysts which are used in the coupling oxidation methane reaction are given as a function of the temperature and the frequency to illustrate the correlation of both data sets and the differences in catalytic mechanisms.

The oxidative coupling of methane over LiMgO and BaBiO3 - x catalysts irradiated by microwaves and classically heated is reported. Enhanced selectivities in C2+ products are observed at lower temperatures under microwave conditions, especially with the LiMgO catalyst. The complex permittivity measurements of BaBiO3 - x show that the regeneration of the active oxygen species on the surface is lower under microwave irradiation than classical heating. X-ray diffraction analyses of the catalyst before and after catalytic reaction, when it is classically heated and when it is heated by microwave irradiation, corroborate these results. Therefore, the CH3− carbanions are less oxidated at the catalyst surface under microwave irradiation. On the other hand, the quenching of the output gas probably decreases the oxidation of CH°3 radicals in the gas phase when the LiMgO catalyst is irradiated by microwaves. The quenching of the output gas is a unique consequence of microwave irradiation which heats the catalyst without heating the wall of the reactor.

The oxidative coupling of methane has been studied on a (SmLiO2)0.8(CaOMgO)0.2 catalyst by using two different modes of heating: a conventional oven and a microwave irradiation set-up. The C2 selectivity obtained with microwave heating was much higher than with conventional heating especially at low conversions. This difference could arise from the reduction of oxidation products (ethane, ethylene) in the gas phase under microwave irradiation.