Kinetics of Heterogeneous Catalytic Reactions

Boudart, M.; Djéga‐Mariadassou, Gérald

doi:10.1515/9781400853335

Cited by 899 publications

(737 citation statements)

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“…The integration of Eq. 2 at maximum temperature leads to a temperature independence of the peak position on initial coverage for a first order desorption process and a temperature dependence for a second order desorption process [34,35]. Our results suggest that methanol desorption follows a first order kinetics (Fig.…”

Section: Effect Of Variation Of Initial Coveragementioning

confidence: 65%

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

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The desorption of methanol and dimethyl ether has been studied over fresh and hydrocarbon-occluded ZSM-5 catalysts with Si/Al ratios of 25, 36 and 135 using a temporal analysis of products reactor. The catalysts were characterized by XRD, SEM, N 2 physisorption and pyridine FT-IR. The crystal size increases with Si/Al ratio from 0.10 to 0.78 µm. The kinetic parameters were obtained using the Redhead method and a plug flow reactor model with coupled convection, adsorption and desorption steps. ZSM-5 catalysts with Si/Al ratios of 25 and 36 exhibit three adsorption sites (low, medium, and high temperature sites), while there is no difference between medium and high temperature sites at a Si/Al ratio of 135. Molecular adsorption on the low temperature site and dissociative adsorption on the medium and high temperature sites give a good match between experiment and the plug flow reactor model. The DME desorption activation energy was systematically higher than that of methanol. Adsorption stoichiometry shows that methanol and DME form clusters onto the binding sites. When non-activated re-adsorption is accounted for, a local equilibrium is reached only on the low and medium temperature binding sites. No differences were observed, other than in site densities, when extracting the kinetic parameters for fresh and activated ZSM-5 catalysts at full coverage. Graphical AbstractElectronic supplementary material The online version of this article (https://doi

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Section: Effect Of Variation Of Initial Coveragementioning

confidence: 65%

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

et al. 2017

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“…Furthermore, none of the fitted models used to date to the authors' knowledge include the formation and conversion of the mono-and diglycerides, the temperature's influence on enzyme deactivation or the equilibrium limitation for conversion. This could be included by using a simple expansion of Equation (3) substituting the triglyceride concentrations with mono-and diglyceride concentrations respectively creating a rake mechanism as known from solid (Bourdart and Djega-Mariadassou, 1984). Equilibrium limitations could be included simply using the reversibility term as suggested by Bourdart and DjegaMariadassou (1984), while temperature deactivation could be formulated by a simple first order enzyme deactivation kinetics.…”

Section: Transesterification With Enzymes Choice Of Enzymesmentioning

confidence: 99%

A review of the current state of biodiesel production using enzymatic transesterification

Fjerbæk

Christensen

Norddahl

2009

Biotech & Bioengineering

662

459

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Enzymatic biodiesel production has been investigated intensively, but is presently employed industrially only in a 20,000 tons/year pilot plant in China (Du et al. [2008] Appl Microbiol Technol 79(3):331-337). This review presents a critical analysis of the current status of research in this area and accentuates the main obstacles to the widespread use of enzymes for commercial biodiesel transesterification. Improved results for enzymatic catalysis are seen with respect to increased yield, reaction time and stability, but the performance and price of the enzymes need further advances for them to become attractive industrially for biodiesel production. Critical aspects such as mass transfer limitations, use of solvents and water activity are discussed together with process considerations and evaluation of possible reactor configurations, if industrial production with enzymes is to be carried out. Results of published studies on the productivity of enzymes are also presented and compared to the use of chemical catalysts.

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“…Therefore, TEM micrographs show an effect on the size of the particles during catalyst preparation, as the mean particle size slightly increases from the starting colloid to the final catalyst. Table 2 shows the diameter of the prepared particles (d) before and after deposition on the supports and the dispersion (D) of the nanoparticles, calculated according to a procedure described in detail elsewhere, assuming a spherical particle shape [29]. Metal loading (wt %) calculated by ICP analyses are included in Table 2.…”

Section: Catalysts Characterisationmentioning

confidence: 99%

Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders

Varela-Gandía

Berenguer-Murcia

Lozano‐Castelló

et al. 2013

Applied Catalysis B: Environmental

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Kinetics of Heterogeneous Catalytic Reactions

Cited by 899 publications

References 0 publications

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

Mechanistic Insights into the Desorption of Methanol and Dimethyl Ether Over ZSM-5 Catalysts

A review of the current state of biodiesel production using enzymatic transesterification

Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders

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