Coke formation in the oxidative dehydrogenation of ethylbenzene to styrene by TEOM

A packed bed microbalance reactor setup (TEOM-GC) is used to investigate the formation of coke as a function of time-on-stream on gamma-Al2O3 and 3P/SiO2 catalyst samples under different conditions for the ODH reaction of ethylbenzene to styrene. All samples show a linear correlation of the styrene selectivity and yield with the initial coverage of coke. The COX production increases with the coverage of coke. On the 3 wt% P/SiO2 sample, the initial coke build-up is slow and the coke deposition rate increases with time. On alumina-based catalyst samples, a fast initial coke build-up takes place, decreasing with time-on-stream, but the amount of coke does not stabilize. A higher O-2 : EB feed ratio results in more coke, and a higher temperature results in less coke. This coking behaviour of Al2O3 can be described by existing "monolayer-multilayer" models. Further, the coverage of coke on the catalyst varies with the position in the bed. For maximal styrene selectivity, the optimal coverage of coke should be sufficient to convert all O-2, but as low as possible to prevent selectivity loss by COX production. This is in favour of high temperature and low O-2 : EB feed ratios. The optimal coke coverage depends in a complex way on all the parameters: temperature, the O-2 : EB feed ratio, reactant concentrations, and the type of starting material.</p

Synthesis and gas adsorption properties of mesoporous silica-NH2-MIL-53(Al) core-shell spheres

Ordered mesoporous silica-NH2-MIL-53(Al) core-shell spheres of about 4 µm in diameter have been synthesized by seeding the corresponding mesoporous silica spheres (MSSs) with crystals of NH2-MIL-53(Al) and subsequent secondary crystal growth into a MOF shell. The morphology of the particles was analyzed by SEM, while TGA, EDX and XRD characterizations gave information on the composition and structure of this material and the activation of the MOF. N2 adsorption analysis revealed that the NH2-MIL-53(Al) shell controlled the access of guest molecules into the hydrophilic silica mesoporous structure, while the breathing behavior of the microporous NH2-MIL-53(Al) shell was confirmed by CO2 adsorption isotherms

Intensifying the Fischer-Tropsch Synthesis by Reactor Structuring—A

Abstract This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of threephase catalytic reactors: slurry bubble columns and multi-tubular fixed beds. A simple mathematical model is used to analyse the effect of structuring on the C 5+ productivity of these two types of reactors. The results of the model show that decreasing the backmixing with a factor 4 and increasing the gas residence time in a slurry bubble column considerably enhances the production of C 5+ . On the other hand in a fixed bed reactor a similar improvement is obtained when the heat transfer coefficient is improved with a factor 2.5 and the diffusion length in catalyst particles is decreased with a factor 2. Both reactors show a potential improvement in productivity per reactor volume; 20% in the slurry bubble column and 40% in the fixed bed reactor