reverse water-gas-shift over a fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ING+JHUInternational audienceAlthough already applied at industrial scale about one century ago, the Fischer-Tropsch process is gaining renewed interests as it is a key step for converting alternative feedstocks, including biomass to transportable fuels. Compared to Co-based catalysts, state of the art Fe catalysts show lower activity (per volume), lower selectivity as it produces a significant and undesirable quantity of CO2 and much faster deactivation. There is a need to develop more active, more selective and more stable Fe Fischer-Tropsch Synthesis (FTS) catalysts. Indeed, Fe particles, especially nanoparticles, sinter to very large particles within the first hours/days on reaction leading to low activity per mass of catalyst. Besides, typical Fe-catalysts contain many different phases, which strongly limit the establishment of structure-activity relationships.We describe here the synthesis of well controlled iron nanoparticles of 3.5 nm encapsulated in the walls of hollow silicalite-11. The encapsulation prevents the particle to sinter under reaction conditions leading to a high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produce any CO2.High resolution TEM and tomography (figure 1) show silicalite-1 hollow single crystals (~100 nm width) with a narrow distribution of the iron particle size centered at 3.5 nm. After 100 hours under reactions, non-significant sintering was observed. FTS performances of the Fe@silicalite-1 (3.4%Fe) were measured at 250°C, 20 bar and H2/CO = 2. In terms of activity per mass of iron the Fe@silicalite-1 catalyst is 10 times more active than a commercial catalyst. It also shows very high C5+ selectivity. In contrast to all other known Fe-catalysts, this iron ship-in-the-bottle catalyst does not produce any CO2. We may hypothesis that the silicalite-1 nano-shell around the Fe particle acts as a water repellent membrane which prevents WGS reaction to occur (CO + H2O => CO2 + H2).Further analysis of this catalyst shall provide insights into the sites responsible for CO2 production, paving the way to a rational design of iron-based FTS catalysts

reverse water-gas-shift over a fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ING+JHUInternational audienceAlthough already applied at industrial scale about one century ago, the Fischer-Tropsch process is gaining renewed interests as it is a key step for converting alternative feedstocks, including biomass to transportable fuels. Compared to Co-based catalysts, state of the art Fe catalysts show lower activity (per volume), lower selectivity as it produces a significant and undesirable quantity of CO2 and much faster deactivation. There is a need to develop more active, more selective and more stable Fe Fischer-Tropsch Synthesis (FTS) catalysts. Indeed, Fe particles, especially nanoparticles, sinter to very large particles within the first hours/days on reaction leading to low activity per mass of catalyst. Besides, typical Fe-catalysts contain many different phases, which strongly limit the establishment of structure-activity relationships.We describe here the synthesis of well controlled iron nanoparticles of 3.5 nm encapsulated in the walls of hollow silicalite-11. The encapsulation prevents the particle to sinter under reaction conditions leading to a high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produce any CO2.High resolution TEM and tomography (figure 1) show silicalite-1 hollow single crystals (~100 nm width) with a narrow distribution of the iron particle size centered at 3.5 nm. After 100 hours under reactions, non-significant sintering was observed. FTS performances of the Fe@silicalite-1 (3.4%Fe) were measured at 250°C, 20 bar and H2/CO = 2. In terms of activity per mass of iron the Fe@silicalite-1 catalyst is 10 times more active than a commercial catalyst. It also shows very high C5+ selectivity. In contrast to all other known Fe-catalysts, this iron ship-in-the-bottle catalyst does not produce any CO2. We may hypothesis that the silicalite-1 nano-shell around the Fe particle acts as a water repellent membrane which prevents WGS reaction to occur (CO + H2O => CO2 + H2).Further analysis of this catalyst shall provide insights into the sites responsible for CO2 production, paving the way to a rational design of iron-based FTS catalysts

highly selective, active and stable fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ECI2D:ING+JHU:YSC:JMI:ATU:DFAInternational audienceWe describe here the synthesis of well controlled iron nanoparticles of 5 nm encapsulated in the walls of hollow silicalite-1. The encapsulation prevent the particle to sinter under reaction conditions leading to very high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produced CO2

highly selective, active and stable fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ING+JHUNational audienceTypical Fe based catalysts have high metal loadings (>70 wt%) and contain many different phases, which strongly limit the establishment of structure-activity relationships. We describe here the synthesis of well controlled iron nanoparticles of 3.5 nm [1] encapsulated in the walls of hollow silicalite-1. The encapsulation prevents the particle to sinter under reaction conditions leading to a high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produce any CO2.High resolution tomography show silicalite-1 hollow single crystals (~100 nm width) with a narrow distribution of the iron particle size centered at 3.5 nm (cf. figure 1). FTS performances of the Fe@silicalite-1 (3.4%Fe) were measured at 250 °C, 20 bar and H2/CO = 2. In terms of activity per mass of iron the Fe@silicalite-1 catalyst is 10 times more active than a commercial catalyst. Besides the high activity, the catalyst did not produce any CO2 against 20% for the commercial catalyst. It also showed a very high C5+ selectivity. In contrast to all other known Fe-catalysts, this iron ship-in-the-bottle catalyst does not show activity for the water-gas-shift reaction during FTS. Non-significant sintering was observed with the exception of a few larger Fe particles present in the big zeolite cavity. Further analysis of this catalyst shall provide insights into the sites responsible for CO2 production, paving the way to a rational design of iron-based FTS catalysts

highly selective, active and stable fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ING+JHUNational audienceAlthough already applied at industrial scale about one century ago, the Fischer-Tropsch process is gaining renewed interests as it is a key step for converting alternative feedstocks, including biomass to transportable fuels. Compared to Co-based catalysts, state of the art Fe catalysts show lower activity (per volume), lower selectivity as it produces a significant and undesirable quantity of CO2 and much faster deactivation. There is a need to develop more active, more selective and more stable Fe Fischer-Tropsch Synthesis (FTS) catalysts. Unfortunately, the origins of low selectivity and fast deactivation are still unclear. Typical Fe based catalysts have high metal loadings (>70 wt%) and contain many different phases, which strongly limit the establishment of structure-activity relationships. We describe here the synthesis of well controlled iron nanoparticles of 5 nm encapsulated in the walls of hollow silicalite-1. The encapsulation prevents the particle to sinter under reaction conditions leading to a high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produce any CO2.High resolution TEM (figure 1) and tomography show silicalite-1 hollow single crystals (~100 nm width) with a narrow distribution of the iron particle size centered at 5 nm. FTS performances of the Fe@silicalite-1 (3.4%Fe) were measured at 250°C, 20 bar and H2/CO = 2 (table 1). A commercial Fe FT catalyst (54.8%Fe, 2.7%Cu, 2.2%K, 0.03%Na, 7.0%Si) was also investigated for comparison. The activities, stabilities and product selectivities of these catalysts were tested several times over a period of 100 h runs. On a volume basis, the catalytic activity of the Fe@silicalite-1 catalyst displayed a low activity in CO conversion. It is due to the low metal amount e.g. 15 times less than the commercial catalyst and the lower powder density. However in terms of activity per mass of iron the Fe@silicalite-1 catalyst is ten times more active. Besides the high activity, the catalyst did not produce any CO2. It also showed a very high C5+ selectivity. In contrast to all other known Fe-catalysts, this iron ship-in-the-bottle catalyst does not show activity for the water-gas-shift reaction during FTS. After 100 hours under reactions, non-significant sintering was observed with the exception of a few larger Fe particles present in the big zeolite cavity.Further analysis of this catalyst shall provide insights into the sites responsible for CO2 production, paving the way to a rational design of iron-based FTS catalysts

highly selective, active and stable fischer-tropsch catalyst using entrapped iron nanoparticles in silicalite-1

SSCI-VIDE+ING+JHUNational audienceTypical Fe based catalysts have high metal loadings (>70 wt%) and contain many different phases, which strongly limit the establishment of structure-activity relationships. We describe here the synthesis of well controlled iron nanoparticles of 3.5 nm [1] encapsulated in the walls of hollow silicalite-1. The encapsulation prevents the particle to sinter under reaction conditions leading to a high and stable Fe dispersion. In addition to the high activity, this catalyst is extremely selective as it does not produce any CO2.High resolution tomography show silicalite-1 hollow single crystals (~100 nm width) with a narrow distribution of the iron particle size centered at 3.5 nm (cf. figure 1). FTS performances of the Fe@silicalite-1 (3.4%Fe) were measured at 250 °C, 20 bar and H2/CO = 2. In terms of activity per mass of iron the Fe@silicalite-1 catalyst is 10 times more active than a commercial catalyst. Besides the high activity, the catalyst did not produce any CO2 against 20% for the commercial catalyst. It also showed a very high C5+ selectivity. In contrast to all other known Fe-catalysts, this iron ship-in-the-bottle catalyst does not show activity for the water-gas-shift reaction during FTS. Non-significant sintering was observed with the exception of a few larger Fe particles present in the big zeolite cavity. Further analysis of this catalyst shall provide insights into the sites responsible for CO2 production, paving the way to a rational design of iron-based FTS catalysts

Interaction of titanium with smectite within the scope of a spent fuel repository: a spectroscopic approach

AbstractThe Swedish and Finnish nuclear waste repository design, KBS-3H, foresees horizontal emplacement of copper canisters-bentonite modules surrounded by a titanium shell. The interaction of titanium with bentonite was studied here using a combination of wet chemistry and a spectroscopic approach to evaluate the potential impact of Ti corrosion on the clay. For natural analogue clays with high Ti contents, spectroscopic investigations showed that titanium occurs as crystalline TiO2. In contrast, the Ti in the MX-80 bentonite occurs in the clay structure, presumably in the octahedral sheet. Hydrothermal tests conducted at 200°C using synthetic montmorillonite showed little if any change in the montmorillonite structure at near-neutral and acidic conditions. Under alkaline conditions, limited alteration was observed, including the formation of trioctahedral clay minerals and zeolite. These changes, however, occurred independently of the addition of Ti. In the batch tests conducted at 80°C, Ti did not occur as separate TiO2particles. The comparison of experimental data with spectroscopic simulations provides sound evidence that Ti was incorporated in a neoformed phyllosilicate structure.</jats:p

The deep-water Peyssonnelia beds from the Balearic islands (Western Mediterranean)

Peyssonnelia bed distribution on continental shelf bottoms of the Balearic Islands (Western Mediterranean) ranges from 40 to 90 m depth. Different species of Peyssonnelia dominate these bottoms and, according to multivariate techniques, two main assemblages have been distinguished: the Peyssonnelia rosa-marina beds and the Peyssonnelia sp. beds, together with some transition samples between Peyssonnelia and maërl beds. Erect red algae are always abundant. Although average yearly irradiance reaching these beds is only 6.4-0.3% of subsurface irradiance, the species richness averages 45 species per sample (1600 cm2) and mean biomass is 2835 g dw. m-2. The high carbonate content of the living algae of these bottoms suggests that they are important contributors to the production of sediments in the Balearic continental shelf.Peer reviewe