A review of late-stage tungsten fuzz growth

Tungsten will be used as the plasma-facing divertor material in the International Thermonuclear Experimental Reactor (ITER) fusion reactor. Under high temperatures and high ion fluxes, a ‘fuzz’ nanostructure forms on the tungsten surface with dramatically different properties and could contaminate the plasma. Although simulations and experimental observations have provided understanding of the initial fuzz formation process, there is debate over whether tungsten or helium migration is rate-limiting during late-stage growth, and the mechanisms by which tungsten and helium migrations occur. Here, the proposed mechanisms are considered in turn. It is concluded that tungsten migration occurs by adatom diffusion along the fuzz surface. Continual helium migration through the porous fuzz to the tungsten bulk is also required for fuzz growth, for continued bubble growth and rupture. Helium likely migrates due to ballistic penetration, although diffusion may contribute. It is difficult to determine the limiting process, which may switch from helium penetration to tungsten adatom diffusion above a threshold flux. Areas for further research to clarify the mechanisms are then considered. A greater understanding of the fuzz formation mechanism is key to the successful design of plasma-facing tungsten components, and may have applications in forming porous tungsten catalysts.

The Production of Liquid Fuel Products by the Catalytic Hydroliquefaction of Sapropels Using Nickel and Nickel-Tungsten Catalysts

Ni catalysts with the carbon-mineral supports obtained from sapropel were synthesized and studied in the catalytic hydroliquefaction of sapropel. It was found that catalysts with the supports obtained from mineral sapropel are more active as compared to those based on organic sapropel; therewith, bimetallic NiW catalysts showed a higher activity than monometallic nickel, irrespective of the support nature. The conversion of the organic matter of sapropel and the composition of liquid products are affected by both the features of supported metal and the composition of support. The liquid products of hydroliquefaction contain mostly the nitrogen- and oxygen-containing compounds. The maximum yield of С5-С21 hydrocarbons is achieved for the catalysts with the supports obtained from mineral sapropel. The composition of the liquid products of sapropel hydroliquefaction is similar to that of biofuels obtained from other renewable sources; such products can be introduced in the known schemes of further processing.

Identification of extremely hard coke generation by low-temperature reaction on tungsten catalysts via Operando and in situ techniques

The coke formation in the catalytic system mainly cause to the catalyst deactivate resulting the dramatic decreasing of the catalyst performance then the catalyst regeneration was required. In this study, adding MgO physically mixed with WO3/SiO2 catalysts were prepared and compared with the ones prepared by physically mixing with SiO2. Adding MgO affected the generation of new species of coke deposited on WO3/SiO2 and MgO itself. Comparing the reaction temperature when adding MgO between at 300 and 450 °C, the different pathway of reaction and the coke formation were found. At 450 °C, the metathesis reaction was more pronounced and the lower temperature of coke deposited on WOx/SiO2 was found. Surprisingly, the extremely hard coke occurred during reaction at 300 °C that the maxima of coke formation was found over 635 °C. This due to the fact that the reduction of reaction temperature from 450 to 300 °C affected the decreasing of the metathesis activity. Conversely, the increasing of dimerization and isomerization of butenes-isomer was observed especially 1-butene and iso-butene. Thus, it could suggest that those quantity of them play the important role to generate the charged monoenyl or cyclopentenyl species by participating with ethene through the dimerization, resulting in the formation of extremely hard coke.

One-pot reductive amination of carboxylic acids: a sustainable method for primary amine synthesis

Recyclable ruthenium–tungsten catalysts perform excellently for the direct reductive amination of carboxylic acids, with up to 96% yield.

Sustainable hydrogenation of aliphatic acyclic primary amides to primary amines with recyclable heterogeneous ruthenium–tungsten catalysts

Hydrogenation of primary aliphatic amides was achieved in CPME with a novel RuWOx/MgAl2O4 catalyst with yields up to 83%.

Hydrogenation of levulinic acid to valeric acid over platinum–tungsten catalysts supported on γ-Al2O3

Highly efficient conversion of levulinic acid to valeric acid over 2Pt–10WO3/γ-Al2O3 catalysts.