Chimie

The process by which progesterone in an ethanol solution is retained by Merck granular activated carbon involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (θ ) of the adsorbing surface and (1 -θ). Over the temperature range 10-40 • C, the specific adsorption rate varies from 5.8•10 -5 to 1.3•10 -4 s -1 . The thermodynamic activation functions for the process are H * = 41.6 kJ/mol and S * = -0.20 kJ/K• mol. The rate of the adsorption-desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent.

In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy (DH ) and entropy (DS ) have been calculated. Finally, information related to variations of differential adsorption enthalpy (DH) and entropy (DS) with the surface coverage fraction (u) was obtained by using the corresponding Clausius-Clapeyron equations. #

The process by which progesterone in an ethanol solution is retained by four carbonaceous materials involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (u ) of the adsorbing surface and (1(/u ). Over the temperature range 10 Á/40 8C, the specific rate constant varies from 5.29 )/10 (4 to 44.85 )/10 (4 s (1 . The formation of the activated species involved in the adsorption process is an endothermal, exoentropic step. The rate of the adsorption Á/desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent. #

In the conditioning tasks of olive-tree a large amount of a woody residue is generated. Such a residue has been traditionally used as a domestic fuel. In the last decades, however, this kind of use has lost importance and the preparation of activated carbons from olive-tree wood appears as an attractive alternative to valorize this by-product. In this study, the optimization of the chemical activation method with phosphoric acid for the production of activated carbon has been analyzed. The results obtained clearly show that samples prepared at 350 and 400°C exhibit a discrete porous development. On the contrary, when the carbonization temperature increases above 450°C the presence of a well-developed mesoporosity is observed. The mercury intrusion curves indicate that the samples exhibit a noticeably developed mesopore volume as well as a wide variety of mesopores ranging from 40 up to 1100 Å of diameter. If the appropriate conditions are used, it is possible to prepare activated carbons showing tailored properties in terms of micro-or mesoporous texture and surface area.

Recently, much research has been focused on liquid oil from biomass pyrolysis, which is considered as an alternative to conventional fossil fuels. This paper studies the effect of heating rate on both the yields and the chemical composition of the oil product obtained from pyrolysis of esparto which is the most important biomass in Morocco. The pyrolysis experiments of esparto was performed in a fixed bed reactor under argon atmosphere with different heating rate: 50, 150 and 2508C min À1 . The maximum conversion of esparto in oil of pyrolysis was obtained with fast pyrolysis 68.5% at 5508C. The FT-IR and 1 H NMR analysis showed that the oil of pyrolysis formed principally by aliphatic compound. The analysis elemental showed that the H/C ratio increase and O/C decrease as the heating rate increase. The PCV improved slightly from 33.5 to 34.8 MJ kg À1 . The oil obtained with higher heating rate has chemical properties similar to diesel that can be used with an economic and environmental advantage.

Recently, much research has been focused on liquid oil from biomass pyrolysis, which is considered as an alternative to conventional fossil fuels. This paper studies the effect of heating rate on both the yields and the chemical composition of the oil product obtained from pyrolysis of esparto which is the most important biomass in Morocco. The pyrolysis experiments of esparto was performed in a fixed bed reactor under argon atmosphere with different heating rate: 50, 150 and 2508C min À1. The maximum conversion of esparto in oil of pyrolysis was obtained with fast pyrolysis 68.5% at 5508C. The FT-IR and 1 H NMR analysis showed that the oil of pyrolysis formed principally by aliphatic compound. The analysis elemental showed that the H/C ratio increase and O/C decrease as the heating rate increase. The PCV improved slightly from 33.5 to 34.8 MJ kg À1. The oil obtained with higher heating rate has chemical properties similar to diesel that can be used with an economic and environmental advantage.