The adsorption equilibria of ammonia gas on various inorganic and organic sorbents were determined at
298.15 K in a pressure range of 0−101 kPa using a static volumetric apparatus. The zeolite sorbents
were 4A, 5A, 13X, dealuminated faujasite, dealuminated pentasil, and clinoptilolite. To illustrate the
differences between commercial grades, the 5A and 13X zeolites were obtained from three suppliers.
Other inorganic sorbents were three aluminas and three silica gels. Organic sorbents were two activated
carbons, charcoal, and two polymeric sorbents (sulfonated and nonsulfonated). The nonlinear experimental
equilibrium data were fitted to the Langmuir, Freundlich, Langmuir−Freundlich, and Toth isotherm
models. The Henry model was used for the linear equilibrium data. The equilibria of all of the sorbents,
with the exception of sulfonated polymeric and dealuminated pentasil zeolite sorbents, provide an accurate
correlation with the isotherm models over the entire pressure range.
Adsorption equilibrium isotherms of ammonia gas were measured at temperatures between 298 and 393 K on 13X zeolite, 4A zeolite, alumina, silica gel, and
The hydrogenation of a wood-based plant sterol mixture consisting of β-sitosterol, β-sitostanol, campesterol, and campestanol was studied using a polymer fiber-supported Pd catalyst. The effect of the operating variables was screened by a fractional factorial experimental design. The hydrogenation experiments revealed that the fiber catalyst is stable, that is metal species are not leached into the reaction mixture, and mechanical agitation does not damage the catalyst. Kinetic experiments were carried out at temperatures of 333-353 K at constant hydrogen pressure. The catalyst was observed to be very selective: the obtained β-sitostanol is a stereochemically pure r-form, and only three byproducts could be quantitatively detected for kinetic modeling. A power-law model and 12 mechanistic models based on two different mechanisms were fitted to the experimental data. The best model assumes the competitive adsorption of sterol and hydrogen molecules as well as the molecular hydrogen adsorption. This model is based on the direct hydrogenation of sterols to stanols without the formation of half-hydrogenated intermediates. The scale-up of hydrogenation process was successfully carried out in pilotplant and industrial reactors.
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