Computational investigation of the kinetics and mechanism of the initial steps of the Fischer-Tropsch synthesis on cobalt.

A multi-site microkinetic model for the Fischer-Tropsch synthesis (FTS) reaction up to C2 products on a FCC cobalt catalyst surface is presented. This model utilizes a multi-faceted cobalt nanoparticle model for the catalyst, consisting of the two dominant cobalt surface facets Co(111) and Co(100), and a step site represented by the Co(211) surface. The kinetic parameters for the intermediates and transition states on these sites were obtained using plane-wave, periodic boundary condition density functional theory. Using direct DFT data as is, the microkinetic results disagree with the expected experimental results. Employing an exploratory approach, a small number of microkinetic model modifications were tested, which significantly improved correspondence to the expected experimental results. Using network flux and sensitivity analysis, an in-depth discussion is given on the relative reactivity of the various sites, CO activation mechanisms, the nature of the reactive chain growth monomer, the probable C2 formation mechanism, the active site ensemble interplay and the very important role of CO* surface coverage. The findings from the model scenarios are discussed with the aim of guiding future work in understanding the FTS mechanism and subsequent controlling kinetic parameters.

Repeated sprint ability related to recovery time in young soccer players.

This study aimed to describe the influence of recovery duration during a repeated sprint ability (RSA) test (6 × 40 m) by investigating a number of variables, such as general performance, metabolic demand, and muscular stretch-shortening performance. Seventeen male soccer outfield players (16 ± 0 years, 66 ± 10 kg) performed three field shuttle-running tests with 15, 20, and 25-sec recoveries. In addition to specific shuttle test's variables, blood lactate concentration and vertical jump height were assessed. Resulting measures were highly reliable (intra-class correlation coefficient up to 0.86). 25-sec recovery improved test performance (-3% total time from 15-sec to 25-sec recovery), vertical jump height (+7% post-test height from 15-sec to 25-sec recovery), and decreased blood lactate accumulation (-33% post-test from 15-sec to 25-sec recovery). Study findings suggest that metabolic acidosis plays a role in worsening performance and fatigue development during the shuttle test. A 25-sec recovery duration maximized performance, containing metabolic-anaerobic power involvement and muscular stretch-shortening performance deterioration during a RSA test.

Site regeneration in the Fischer-Tropsch synthesis reaction: a synchronized CO dissociation and C-C coupling pathway.

A critical issue in the Fischer-Tropsch synthesis reaction is the blocking of the active sites for low barrier CO dissociation by the C(1) adsorbed species generated from CO dissociation, which can hinder the further steps in the FT process. Here, we propose a synchronized pathway for low barrier CO dissociation and C-C coupling on a corrugated Ru surface.