NMR Imaging of the Distribution of the Liquid Phase in a Catalyst Pellet during α-Methylstyrene Evaporation Accompanied by Its Vapor-Phase Hydrogenation

Koptyug, Igor V.; Куликов, А. В.; Lysova, Anna A.; Кириллов, В. А.; Parmon, and Valentin N.; Sagdeev, R. Z.

doi:10.1021/ja026713u

Cited by 51 publications

(33 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have employed a combination of NMR imaging (figure 9) and spectroscopy to visualize the processes in an operating single catalyst pellet [13,26,27] or in a granular catalyst bed. During the experiments, the catalyst (Pt/c-Al 2 O 3 ) is residing inside the rf coil of the NMR instrument, and the H 2 gas and the liquid reactant (a-methylstyrene, AMS) preheated to 68-80°C are supplied to the reaction volume.…”

Section: Coupling Of Mass Transport and Chemical Reactionmentioning

confidence: 99%

NMR imaging of mass transport processes and catalytic reactions

et al. 2005

Self Cite

View full text Add to dashboard Cite

c Boreskov Institute of Catalysis, 5 Acad. Lavrentiev Pr., Novosibirsk 630090, Russia NMR imaging and spectroscopy techniques are applied to study flow and filtration of liquids, gases and granular solids in various geometries and to the in situ studies of the interplay of mass transport and catalytic reactions in porous media. In particular, quantitative spatially resolved maps of flow velocities of liquids and gases in the channels of monoliths have been obtained. A comparative study of the filtration of water and propane through model porous media has revealed that the dispersion coefficients for water are dominated by the holdup effects even in a bed of nonporous glass beads. Similar experiments performed with the gravity driven flow of liquid-containing fine solid particles through a porous bed have yielded the distributions of particle velocities for various flow rates. The NMR imaging technique was employed to visualize the propagation of autocatalytic waves for the Belousov-Zhabotinsky reaction carried out in a model porous medium. It was demonstrated that the wave propagation velocity decreases as the wave crosses the boundary between the bulk liquid and the flooded bead pack. The images detected during the catalytic hydrogenation of a-methylstyrene on a single catalyst pellet at elevated temperatures have revealed that the reaction and the accompanying phase transition alter the distribution of the liquid phase within the pellet.

show abstract

Section: Coupling Of Mass Transport and Chemical Reactionmentioning

confidence: 99%

NMR imaging of mass transport processes and catalytic reactions

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…Then, by definition, ϕ can be expressed as (10) The change in the thickness h dry of the dry surface layer according to expression (10) and Fig. 4a is equal to (11) The volume of the dry surface layer within which there is vapor-phase AMS hydrogenation is found as (12) β gas ShD AH /d eq = , D AH 6 10 5 -T gas /373 ( ) 1.9 , × = α gas Nuλ gas /d eq = , λ gas 0.216 T gas /373…”

Section: Estimation Of Parameters Of Mathematical Modelmentioning

confidence: 99%

“…For this purpose, the most promising experimental method is in situ NMR tomography (magnetic resonance microimaging) [7][8][9]. This method allows one, in particular, to obtain images of the liquid-phase distribution within the porous object and monitor the liquid-phase redistribution immediately during the process without destroying the object and without introducing any probes or molecular labels [10][11][12][13]. EXPERIMENTAL As a model reaction, we chose α -methylstyrene (AMS) hydrogenation to form cumene: C 6 H 5 C(CH 3 )=CH 2 + H 2 C 6 H 5 C(H)(CH 3 ) 2 .…”

mentioning

confidence: 99%

Self-oscillations on a partially wetted catalyst pellet in ?-methylstyrene hydrogenation: Experiment and mathematical modeling

Кириллов

Koptyug

Куликов

et al. 2005

Theor Found Chem Eng

View full text Add to dashboard Cite

Catalytic reactions of hydrogenation of liquid hydrocarbons underlie many petrochemical processes. A feature of these reactions is high heat release, because of which components of the liquid phase can evaporate and the reactions can occur in both the liquid and the vapor-gas phases on wetted and dry catalyst pellets, respectively. The interplay between chemical and phase changes on an incompletely flooded pellet give rise to various types of steady-state heat modes.Experimental studies in this area were started [1, 2] with model reactions of hydrogenation of α -methylstyrene (AMS) and cyclohexene in a three-phase system. In steady-state experiments on cyclohexene hydrogenation on a single catalyst pellet [2], multiplicity of temperature and flooding states of the catalyst pellet was first observed, which were dependent on the initial impregnation of the pellet with liquid. In AMS hydrogenation [3], phenomena of the "ignition" and the "extinction" type were experimentally investigated for the first time in irrigation of various types of single catalyst pellets at different flow rates of the liquid reactant.Previously [4], we proposed a physical mechanism and developed several simple models for a monoporous pellet, which, by and large, explained the experimental data [3]. We also put forward a more complex mathematical model of AMS hydrogenation on a catalytic plate that is partially wetted on the surface and partially impregnated with the liquid reactant. This model took into account the pore size distribution, the pore filling distribution, and the reactions in the liquid and gas phases [5]. Using this model, by numerical methods, multiplicity of steady states and hystereses of temperature and the degree of pellet filling with the liquid were revealed.It is known that the interplay between physical steps of the process (impregnation of a pellet with the liquid, liquid evaporation, heat and mass transfer) and chemical reactions in the liquid and vapor-gas phases may lead to instability and self-oscillation modes in threephase systems [6]. Therefore, it seems necessary to study such modes further.The purpose of this work was to experimentally and theoretically investigate self-oscillation modes on an irrigated porous catalyst pellet in exothermic hydrogenation accompanied by liquid evaporation. For this purpose, the most promising experimental method is in situ NMR tomography (magnetic resonance microimaging) [7][8][9]. This method allows one, in particular, to obtain images of the liquid-phase distribution within the porous object and monitor the liquid-phase redistribution immediately during the process without destroying the object and without introducing any probes or molecular labels [10][11][12][13]. EXPERIMENTAL As a model reaction, we chose α -methylstyrene (AMS) hydrogenation to form cumene:C 6 H 5 C(CH 3 )=CH 2 + H 2 C 6 H 5 C(H)(CH 3 ) 2 . This reaction is most widely used as a model reaction in the experimental investigation of processes in trickle-bed reactors (in which there is a downward cocurrent g...

show abstract

“…Nuclear magnetic resonance (NMR) imaging [9] offers certain advantages over other tomographic techniques. Recently it has been shown that NMR imaging can be successfully applied to map the liquid phase distribution within a functioning multiphase reactor [10,11] and to monitor the spatial variation of conversion along the length of the catalyst bed [12]. Under non-reactive conditions, the liquid holdup and the extent of surface wetting efficiency during trickle flow have been estimated with the use of two-dimensional (2D) and three-dimensional (3D) NMR imaging [13,14].…”

Section: Introductionmentioning

confidence: 99%

An NMR Imaging Study of Steady-State and Periodic Operation Modes of a Trickle Bed Reactor

et al. 2009

View full text Add to dashboard Cite

NMR imaging has been applied to study the steady-state and the periodic operations of a functioning trickle bed reactor. It has been revealed that under conditions of the continuous supply of a liquid reagent to the catalyst bed, the bed was mostly filled with the liquid phase and was characterized by the uniform and stationary distribution of a liquid phase, whereas under conditions of the periodic supply of a liquid reagent to the catalyst bed with the same liquid flow velocity the bed was mostly dry and was characterized by a non-stationary distribution of the liquid phase. The oscillations of the liquid phase content within the bed, corresponding to the modulated liquid flow, have been observed. It has been shown that performing the hydrogenation reaction in a trickle bed reactor under conditions of the periodic supply of a liquid reagent to the catalyst bed leads to the intensification of the hydrogenation process. It becomes apparent in the significant increase of the temperature of the catalyst bed as well as in the increase of the conversion degree in the regimes under forced time-varying liquid flow rates in comparison to the steady-state regime of the reactor operation.

show abstract

NMR Imaging of the Distribution of the Liquid Phase in a Catalyst Pellet during α-Methylstyrene Evaporation Accompanied by Its Vapor-Phase Hydrogenation

Cited by 51 publications

References 6 publications

NMR imaging of mass transport processes and catalytic reactions

NMR imaging of mass transport processes and catalytic reactions

Self-oscillations on a partially wetted catalyst pellet in ?-methylstyrene hydrogenation: Experiment and mathematical modeling

An NMR Imaging Study of Steady-State and Periodic Operation Modes of a Trickle Bed Reactor

Contact Info

Product

Resources

About