Wioletta Raróg-Pilecka

Effect of a Barium Promoter on the Stability and Activity of Carbon‐Supported Cobalt Catalysts for Ammonia Synthesis

Samples of barium‐promoted carbon‐supported cobalt catalysts for ammonia synthesis were prepared; the cobalt content was constant (27.4 wt %) and the amount of barium introduced differed within the range of 0–0.88 mmol gC+Co−1. Turbostratic carbon was used as the support. Several techniques, including X‐ray powder diffraction, TEM, Thermogravimetric analysis–mass spectrometry (methanation studies) and H2 temperature‐programmed desorption were used to examine the properties of the carbon support or catalytic materials. The reaction rate measurements were performed under the following conditions: T=400 °C, p=9.0 MPa, x  NH 3 =8.5 mol %, H2/N2=3:1. It was found that barium is an important component of the cobalt catalysts supported on activated carbon for ammonia synthesis. Barium inhibits the process of carbon support methanation, which also results in a decrease in the sintering of the active phase (cobalt). Moreover, even a small amount of barium significantly activates the cobalt surface in ammonia synthesis, suggesting that barium locates primarily on the surface of cobalt.

Effect of the ruthenium loading and barium addition on the activity of ruthenium/carbon catalysts in carbon monoxide methanation

Abstract A group of supported ruthenium catalysts was prepared and tested in methanation of small CO amounts (7000 ppm) in hydrogen-rich streams. High surface area graphitized carbon (484 m2/g) was used as a support for ruthenium and RuCl3 was used as a Ru precursor. Some of the Ru/C systems were additionally doped with barium (Ba(NO3)2 was barium precursor). The catalysts were characterized by the chemisorption technique using CO as an adsorbate. To determine the resistance of the catalysts to undesired carbon support methanation, the TG-MS experiments were performed. They revealed that the barium addition inhibits support losses. The studies of CO methanation (fl ow reactor, atmospheric pressure) have shown that some of the supported ruthenium catalysts exhibit high activities referred to the metal mass. The catalytic properties of ruthenium proved to be dependent on metal dispersion. Some of the Ru/C and Ba-Ru/C systems exhibit higher activity in CO hydrogenation than the commercial nickel-based catalyst.

Cobalt-lanthanum catalyst precursors for ammonia synthesis: determination of calcination temperature and storage conditions

Abstract A thermal decomposition of a cobalt-lanthanum catalyst precursor containing a mixture of cobalt and lanthanum compounds obtained by co-precipitation were studied using thermal analysis coupled with mass spectrometry (TG-MS). Studies revealed that the calcination in air at 500°C is sufficient to transform the obtained cobalt precipitate into Co3O4, but it leads to only partial decomposition of lanthanum precipitate. In order to obtain Co/La catalyst precursor containing La2O3 the calcination in air at the temperature about 800°C is required. However, it is unfavorable from the point of view of textural properties of the catalyst precursor. A strong effect of storage conditions on the phase composition of the studied cobalt-lanthanum catalyst precursor, caused by the formation of lanthanum hydroxide and lanthanum carbonates from La2O3 when contacting with air, was observed.

Properties and activity of the cobalt catalysts for NH3 synthesis obtained by co-precipitation – the effect of lanthanum addition

Abstract In modern research on catalysts for NH3 synthesis a lot of attention is paid to cobalt. In this work the new catalytic systems based on cobalt are presented. Unsupported cobalt catalysts singly promoted (La or Ba) and doubly promoted (La and Ba) were prepared and tested in NH3 synthesis reaction under commercial synthesis conditions. Characterization studies revealed that lanthanum plays a role of a structural promoter, which improves the surface of catalyst precursors and prevents from sintering during calcination. However, lanthanum has a negative effect on the reduction of cobalt oxide, but the addition of barium promoter (Co/La/Ba catalyst) diminishes the negative impact of La. The co-promotion of cobalt with lanthanum and barium results in the increasing of the active phase surface and improvement of its activity in NH3 synthesis.