Hydrogen adsorption axial

The hydrogenation of 3 -substituted cholest-5-enes gives almost exclusively the corresponding 5a compounds [56], indicating that the stereochemistry of the reduction process is insensitive to the nature of the equatorial substituent at C(3). In contrast, reduction of 3a-substituted-cholest-5-enes [57] gives mixtures of the 5 a- and 5jS-products in which the latter may predominate. The ratio of products depends on the size of the axial 3a-substituent and its ability to block adsorption of the a-face of the molecule on to the catalyst surface. A C i9 hydroxyl group is reported to increase the proportion of 5 -product [58]. 

The velocity profiles and the axial distribution of volume fraction of solid particles are shown in Fig 4.12. The solid velocity pattern did show a non-axial symmetric behavior. The axial distribution of the solid phase was close to uniform. Figure 4.13 displays the outlet fractions of hydrogen, methane, and CO2 in the gas phase as achieved for the SMR and SE-SMR processes operated in a BFB reactor. In the SMR results, the outlet molar fraction of H2 is only 75 %, thus a considerable amount of CO2 and CH4 are emitted out of the reactor. In the SE-SMR process results, both the conversion of methane and the adsorption of CO2 are larger than 99 %. The simulation results show that the integration of CO2 sorption in the SMR process can enhance the methane conversion to hydrogen to near the equilibrium composition in the BFB reactor. 

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