Showing papers on "Cobalt sulfide published in 1995"
TL;DR: The mean kinetic energy of chemisorbed hydrogen in molybdenum and cobalt sulfide catalysts has been measured by Compton neutron scattering on the electronvolt spectrometer (eVS) as the Rutherford Appleton Laboratory ISIS facility.
Abstract: The mean kinetic energy of chemisorbed hydrogen in molybdenum and cobalt sulfide catalysts has been measured by Compton neutron scattering on the electronvolt spectrometer (eVS) as the Rutherford Appleton Laboratory ISIS facility. Assuming an isotropic harmonic oscillator, the fundamental wavenumbers of vibrations associated with chemisorbed hydrogen are 1430 ± 34 cm–1 for MoS2 and 1392 ± 26 cm–1 for CoMoS2; there was no hydrogen peak in the eVS spectrum of Co9S8. The frequencies are closer to the mean values expected for H—S stretching and bending vibrations (ca. 1300 cm–1) than for H—Mo (ca. 1100 cm–1); the chemisorbed hydrogen observed by eVS is evidently bound to sulfur.
17 citations
TL;DR: In this paper, a variety of physicochemical techniques (temperature programmed decomposition and sulfidation, both followed by subsequent TPO, XRD, TPR, microelectrophoresis, XPS and AEM) were used to study the samples, verify the formation of the ''CoMoS phase'' in the mixed CoMo sulfide and investigate the existence of interactions between the sulfides forming the mechanical mixtures.
Abstract: Unsupported Co9S8, MoS2, and CoMoS sulfides (prepared by the HSP method) as well as supported MoS2/Al2O3 and CoSx/C (prepared by impregnation) were used to prepare a series of binary mechanical mixtures of various compositions. A variety of physicochemical techniques (temperature programmed decomposition and sulfidation, both followed by subsequent TPO, XRD, TPR, microelectrophoresis, XPS and AEM) were used to study the samples, verify the formation of the ''CoMoS phase'' in the mixed CoMo sulfide and investigate the existence of interactions between the sulfides forming the mechanical mixtures. The catalytic activity of the supported and unsupported HSP sulfides as well as that of the mechanical mixtures was tested in the hydrodesulfurization of thiophene (HDS) and the hydrogenation of cyclohexene (HYD) at 513 K and 3 MPa. The mechanical mixtures exhibit a synergy in HDS and HYD. This shows that cobalt sulfide (supported or unsupported HSP) can promote the activity not only of molybdenum sulfide, but also of the unsupported HSP ''CoMoS phase''. In addition, XRD and AEM (performed before and after catalytic tests) were used to study the evolution of the unsupported ''CoMoS phase'' during the catalytic reaction, ft was found that this phase is unstable; cobalt segregates from the CoMoS association to form Co9S8, even after a relatively short period in the reactor. These results provide more evidence that the remote control mechanism plays a major role in the synergetic behavior of the CoMo hydrotreating catalysts.
13 citations
TL;DR: Cobalt ions have been recovered from aqueous solutions by dispersed-air flotation in acidic conditions The preliminary step of precipitation as cobalt sulfide using Na2S is kinetically limited, with only approximately 70% of the cobalt ions being recovered.
Abstract: Cobalt ions have been recovered from aqueous solutions by dispersed-air flotation in acidic conditions The preliminary step of precipitation as cobalt sulfide using Na2S is kinetically limited, with only approximately 70% of the cobalt ions being recovered Recoveries increase considerably under alkaline conditions, where Co(OH)2 is also precipitated Several collectors have been tested: cetyl trimethyl ammonium bromide, sodium dodecyl sulfate cetyl pyridinium chloride, and dodecylamine; dodecylamine was found to be the most efficient The gas flow rate was found to affect the process, with a flow rate corresponding to a superficial gas velocity of 01 cm/s yielding maximum recoveries; any further gas flow rate increase resulted in lower recoveries An increase in column height was found to have an adverse effect on CoS recovery
4 citations