Fugacity control

Ballhaus, C., Berry, R.F., Green, D.H. 1990. Oxygen fugacity controls in the Earth s upper mantle. Nature, 348, 437-440. 

H2S fugacity (/h2S)- It is thought that /hjS is controlled by pyrite, Fe-oxides such as magnetite, hematite and Fe-silicates such as chlorite. For instance, the following reaction is important for controlling /hjS (Giggenbach, 1997) ... 

Fixed-activity and sliding-activity paths (Sections 14.2-14.3) are analogous to their counterparts in fugacity, except that they apply to aqueous species instead of gases. Fixed-activity paths are useful for simulating, for example, a laboratory experiment controlled by a pH-stat, a device that holds pH constant. Sliding-... 

Initial rate data of the catalytic dehydration of butanol-1 are believed controlled by the surface reaction rate with this rate equation in terms of the fugacity, f,... 

Paraiba, L.C., Carrasco, J.M., Bru, R. (1999) Level IV Fugacity model by a continuous time control system. Chemosphere 38, 1763-1775. 

Hydrocarbon distributions in the Fischer-Tropsch (FT) synthesis on Ru, Co, and Fe catalysts often do not obey simple Flory kinetics. Flory plots are curved and the chain growth parameter a increases with increasing carbon number until it reaches an asymptotic value. a-Olefin/n-paraffin ratios on all three types of catalysts decrease asymptotically to zero as carbon number increases. These data are consistent with diffusion-enhanced readsorption of a-olefins within catalyst particles. Diffusion limitations within liquid-filled catalyst particles slow down the removal of a-olefins. This increases the residence time and the fugacity of a-olefins within catalyst pores, enhances their probability of readsorption and chain initiation, and leads to the formation of heavier and more paraffinic products. Structural catalyst properties, such as pellet size, porosity, and site density, and the kinetics of readsorption, chain termination and growth, determine the extent of a-olefin readsorption within catalyst particles and control FT selectivity. 

Secondary reactions are affected by the residence time of primary products within the catalyst bed while primary reactions are controlled only by the fugacity of reactants (and products if they affect the rate and selectivity of primary reactions pathways). Therefore, studies of the effects of bed residence time and of the presence of reaction products in the H2/CO feed are... 

Diffusive and convective transport processes introduce flexibility in the design of catalyst pellets and in the control of FT synthesis selectivity. Transport restrictions lead to the observed effects of pellet size, site density, bed residence time, and hydrocarbon chain size on chain growth probability and olefin content. The restricted removal of reactive olefins also allows the introduction of other intrapellet catalytic functions that convert olefins to other valuable products by exploiting high intrapellet olefin fugacities. Our proposed model also describes the catalytic behavior of more complex Fe-... 

Hemley et al. (1992) studied the solubility of iron, lead, zinc, and copper sulfides in chloride solutions that were rock-bufifered in pH and in oxygen and sulfur fugacity, in the range 300-700 °C 50-200 MPa. Their results show that iron-, copper-, zinc-, and lead-sulfide mineral solubilities decrease with decreasing temperature and decreasing total chloride (see Figure 2), and with increasing pressure. In nature, the HCl concentration (which is the sum of HC1° and some portion of the ionized and Cl ) in a hydrothermal solution is controlled by equilibria such as... 

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