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Avelino Corma - One of the best experts on this subject based on the ideXlab platform.
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Control of the Reaction Mechanism of Alkylaromatics Transalkylation by Means of Molecular Confinement Effects Associated to Zeolite Channel Architecture
ACS Catalysis, 2019Co-Authors: Vicente J. Margarit, Cristina Martínez, Sulaiman S. Al-khattaf, Mogahid Osman, Mercedes Boronat, Avelino CormaAbstract:Transalkylation of alkylaromatics catalyzed by acid zeolites is a process widely employed in the petrochemical industry for upgrading aromatic fractions. The reaction mechanism is complex as it can...
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One-pot co-crystallization of beta and pentasil nanozeolites for the direct conversion of a heavy reformate fraction into xylenes
Applied Catalysis A: General, 2019Co-Authors: Vicente J. Margarit, M. Teresa Portilla, M. Teresa Navarro, Raed Abudawoud, Ibrahim M. Al-zahrani, Sohel Shaikh, Cristina Martínez, Avelino CormaAbstract:Abstract Upgrading of the heavy reformate fraction (HR), containing mainly C9+ aromatics, is usually performed by dealkylation or by Transalkylation with added benzene and/or toluene to obtain the more valuable xylenes. However, when the costs related to the use of benzene and toluene are considered, the one-step dealkylation/Transalkylation of the C9+ alkylaromatics to xylenes becomes economically attractive. Thus, in a first step, ethylmethylbenzenes (EMB) will have to be dealkylated to toluene, which will then react with the trimethylbenzenes (TMB) present in the HR feed to produce xylenes by Transalkylation. Medium pore zeolites will favor dealkylation, whereas large pore zeolites will be more adequate for carrying out the Transalkylation reaction. In this work, we present the one-pot synthesis of beta-pentasil aggregates with tunable ratios of the large pore beta to the medium pore component. We show that the close proximity of the beta and pentasil nanocrystals obtained by one-pot co-crystallization synthesis, results in a highly efficient catalyst for the consecutive dealkylation/Transalkylation process. The bifunctional catalyst based on the co-crystallized aggregate is more active and selective to xylenes than a catalyst based on a physical mixture of equivalent beta and pentasil nanozeolites synthesized following an analogous procedure. The small crystallite sizes of the co-crystallized zeolites provide the additional advantage of a lower deactivation rate as compared to a reference benchmark catalyst. Results are shown on both, model molecules and industrial HR feed.
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Diffusion of Trimethylbenzenes and Xylenes in Zeolites with 12- and 10-Ring Channels as Catalyst for Toluene-Trimethylbenzene Transalkylation
The Journal of Physical Chemistry C, 2016Co-Authors: Jordi Toda, Avelino Corma, German SastreAbstract:A molecular dynamics study of the diffusion of trimethylbenzene (TMB) and xylene molecules involved in toluene and TMB Transalkylation reaction has been performed over 6 different pure-silica zeolites, containing 10- and 12-ring channels: BOG, MSE, IWR, SFS, SOF, and UWY. The shape selective properties of these six frameworks have been tested using two different loadings: one loading characteristic of the early stage and another of the late stage of the reaction. The collected data explains the diffusion behavior of these molecules in the zeolite frameworks and allows researchers to obtain trends and also rationalize their performance as candidates for the selective production of p-xylene during Transalkylation of toluene and TMB. UWY appears a promising zeolite that allows the reaction of the TMBs in the 12-ring channels, is able to host the transition states, and favors the preferential diffusion of p-xylene in the 10-ring channels.
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Diffusion of Trimethylbenzenes and Xylenes in Zeolites with 12- and 10-Ring Channels as Catalyst for Toluene-Trimethylbenzene Transalkylation
2016Co-Authors: Jordi Toda, Avelino Corma, German SastreAbstract:A molecular dynamics study of the diffusion of trimethylbenzene (TMB) and xylene molecules involved in toluene and TMB Transalkylation reaction has been performed over 6 different pure-silica zeolites, containing 10- and 12-ring channels: BOG, MSE, IWR, SFS, SOF, and UWY. The shape selective properties of these six frameworks have been tested using two different loadings: one loading characteristic of the early stage and another of the late stage of the reaction. The collected data explains the diffusion behavior of these molecules in the zeolite frameworks and allows researchers to obtain trends and also rationalize their performance as candidates for the selective production of p-xylene during Transalkylation of toluene and TMB. UWY appears a promising zeolite that allows the reaction of the TMBs in the 12-ring channels, is able to host the transition states, and favors the preferential diffusion of p-xylene in the 10-ring channels
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gold nanoparticles promote the catalytic activity of ceria for the Transalkylation of propylene carbonate to dimethyl carbonate
Green Chemistry, 2009Co-Authors: Raquel Juarez, Avelino Corma, Hermenegildo GarciaAbstract:A series of metal oxide nanoparticles with acid or basic properties exhibit low to moderate activity towards the Transalkylation of propylene carbonate with methanol; deposition of gold nanoparticles on nanoparticulated ceria significantly increases the activity of this metal oxide towards Transalkylation.
Jiří Čejka - One of the best experts on this subject based on the ideXlab platform.
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Transalkylation of ethyl benzene with triethylbenzene over ZSM-5 zeolite catalyst
Chemical Engineering Journal, 2010Co-Authors: M. Naseem Akhtar, Sulaiman S. Al-khattaf, N. M. Tukur, Nabil Al-yassir, Jiří ČejkaAbstract:Abstract Transalkylation of 1,3,5-triethylbenzene (TEB) with ethylbenzene (EB) has been studied over ZSM-5 zeolite using a riser simulator reactor with respect to optimizing DEB yield. The reaction temperature was varied from 350 to 500 °C with contact time ranging from 3 to 15 s to report on the effect of reaction conditions on TEB conversion, DEB selectivity and isomerization of TEB. The Transalkylation of TEB with EB was compared with the reactions of pure 1,3,5-TEB and EB (disproportionation, isomerization and cracking). A synergistic effect was observed on the conversion of 1,3,5-TEB and DEB yield. The 1,3,5-TEB conversion increased from 40% to 50% with simultaneous increase in the DEB selectivity from 17% to 36% in Transalkylation reaction (EB + 1,3,5-TEB) as compared with the reaction of pure 1,3,5-TEB. It was found that pure 1,3,5-TEB underwent cracking reaction to produce DEB and EB. The isomerization of 1,3,5-TEB was more active at low temperature while cracking was more active at high temperature. The temperature of 350 °C was observed as the optimum for production of maximum amount of DEB. Kinetic parameters for the disappearance of 1,3,5-TEB during its transformation reaction via cracking and isomerization pathways were calculated using the catalyst activity decay function based on time-on-stream (TOS). The apparent activation energies decrease in order Esecondary cracking > Eprimary racking > Eisomerization for ZSM-5 catalysts.
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Transalkylation of toluene with trimethylbenzenes over large-pore zeolites
Applied Catalysis A-general, 2010Co-Authors: Andrea Krejčí, Sulaiman S. Al-khattaf, Muhammad Ali, Martina Bejblová, Jiří ČejkaAbstract:Abstract Zeolites Beta, mordenite and Y were evaluated for their activity in Transalkylation reaction of toluene with trimethylbenzenes. Zeolite Beta was found to possess the highest conversion in toluene–trimethylbenzene Transalkylation as well as a higher stability in time-on-stream compared with mordenite and zeolite Y. The effect of Si/Al ratio in zeolite Beta was evaluated and it was found that Transalkylation activity and xylene yields increase with decreasing Si/Al ratio. Zeolite Beta with the lowest Si/Al ratio of 12.5 (the highest concentration of active sites) exhibited the highest 1,2,4-trimethylbenzene (124TMB) conversion and maximum xylene yield. The highest xylene yield was obtained at optimum equimolar ratio (1:1) of 124TMB to toluene. With increasing 124TMB concentration in the feed, the conversion of 124TMB and xylene yield decreased while toluene conversion simultaneously increased. The increase in the concentration of toluene in the feed resulted in the increase in the conversion of 124TMB. However, addition of higher concentrations of toluene led to a significant decrease in xylene yield.
Sulaiman S. Al-khattaf - One of the best experts on this subject based on the ideXlab platform.
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Control of the Reaction Mechanism of Alkylaromatics Transalkylation by Means of Molecular Confinement Effects Associated to Zeolite Channel Architecture
ACS Catalysis, 2019Co-Authors: Vicente J. Margarit, Cristina Martínez, Sulaiman S. Al-khattaf, Mogahid Osman, Mercedes Boronat, Avelino CormaAbstract:Transalkylation of alkylaromatics catalyzed by acid zeolites is a process widely employed in the petrochemical industry for upgrading aromatic fractions. The reaction mechanism is complex as it can...
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Influence of toluene–tetramethylbenzene Transalkylation on heavy aromatics conversion to xylenes
Journal of Industrial and Engineering Chemistry, 2015Co-Authors: Sulaiman S. Al-khattaf, Syed A Ali, Mogahid Osman, Abdullah M AitaniAbstract:Abstract Transalkylation of toluene–tetramethylbenzene (TeMB) over MOR and BEA was investigated at 250–400 °C. Conversion of TeMB was higher than trimethylbenzene (TMB) and toluene. Xylene yield was in the following order: toluene − TMB − TeMB > toluene − TeMB > toluene − TMB ≫ toluene . Kinetic modeling for reaction network consisting of toluene–TeMB Transalkylation; toluene disproportionation; and toluene–TMB Transalkylation was carried out. Toluene–TeMB Transalkylation rate was >50% higher than the toluene–TMB Transalkylation while the toluene disproportionation was an order of magnitude slower than Transalkylation reactions. An addition of 5–10 wt.% TeMBs to the heavy reformate caused minor impact on the xylene yield but an improvement in xylene selectivity.
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Transalkylation of ethyl benzene with triethylbenzene over ZSM-5 zeolite catalyst
Chemical Engineering Journal, 2010Co-Authors: M. Naseem Akhtar, Sulaiman S. Al-khattaf, N. M. Tukur, Nabil Al-yassir, Jiří ČejkaAbstract:Abstract Transalkylation of 1,3,5-triethylbenzene (TEB) with ethylbenzene (EB) has been studied over ZSM-5 zeolite using a riser simulator reactor with respect to optimizing DEB yield. The reaction temperature was varied from 350 to 500 °C with contact time ranging from 3 to 15 s to report on the effect of reaction conditions on TEB conversion, DEB selectivity and isomerization of TEB. The Transalkylation of TEB with EB was compared with the reactions of pure 1,3,5-TEB and EB (disproportionation, isomerization and cracking). A synergistic effect was observed on the conversion of 1,3,5-TEB and DEB yield. The 1,3,5-TEB conversion increased from 40% to 50% with simultaneous increase in the DEB selectivity from 17% to 36% in Transalkylation reaction (EB + 1,3,5-TEB) as compared with the reaction of pure 1,3,5-TEB. It was found that pure 1,3,5-TEB underwent cracking reaction to produce DEB and EB. The isomerization of 1,3,5-TEB was more active at low temperature while cracking was more active at high temperature. The temperature of 350 °C was observed as the optimum for production of maximum amount of DEB. Kinetic parameters for the disappearance of 1,3,5-TEB during its transformation reaction via cracking and isomerization pathways were calculated using the catalyst activity decay function based on time-on-stream (TOS). The apparent activation energies decrease in order Esecondary cracking > Eprimary racking > Eisomerization for ZSM-5 catalysts.
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Transalkylation of toluene with trimethylbenzenes over large-pore zeolites
Applied Catalysis A-general, 2010Co-Authors: Andrea Krejčí, Sulaiman S. Al-khattaf, Muhammad Ali, Martina Bejblová, Jiří ČejkaAbstract:Abstract Zeolites Beta, mordenite and Y were evaluated for their activity in Transalkylation reaction of toluene with trimethylbenzenes. Zeolite Beta was found to possess the highest conversion in toluene–trimethylbenzene Transalkylation as well as a higher stability in time-on-stream compared with mordenite and zeolite Y. The effect of Si/Al ratio in zeolite Beta was evaluated and it was found that Transalkylation activity and xylene yields increase with decreasing Si/Al ratio. Zeolite Beta with the lowest Si/Al ratio of 12.5 (the highest concentration of active sites) exhibited the highest 1,2,4-trimethylbenzene (124TMB) conversion and maximum xylene yield. The highest xylene yield was obtained at optimum equimolar ratio (1:1) of 124TMB to toluene. With increasing 124TMB concentration in the feed, the conversion of 124TMB and xylene yield decreased while toluene conversion simultaneously increased. The increase in the concentration of toluene in the feed resulted in the increase in the conversion of 124TMB. However, addition of higher concentrations of toluene led to a significant decrease in xylene yield.
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1,3,5-Triethylbenzene Transformation Reactions Compared to Its Transalkylation Reaction with Ethylbenzene
Energy & Fuels, 2009Co-Authors: M. Naseem Akhtar, Sulaiman S. Al-khattafAbstract:The Transalkylation of 1,3,5-triethylbenzene (1,3,5-TEB) with ethylbenzene (EB) has been studied over USY-type catalysts using a riser simulator that mimics the operation of a fluidized-bed reactor. The reaction mixture EB and 1,3,5-TEB was used at a molar ratio of 1:1, which is equivalent to 40:60 wt % of EB/1,3,5-TEB, respectively. The reaction temperature was varied from 350 to 500 °C with a time on stream ranging from 3−15 s. The effect of reaction conditions on 1,3,5-TEB conversion, DEB selectivity, and isomerization of 1,3,5-TEB is reported. The Transalkylation of 1,3,5-TEB with EB has been compared to the transformation reaction of pure 1,3,5-TEB and EB. The experimental results have revealed that reactivity of 1,3,5-TEB and selectivity of DEB is increased during the Transalkylation reaction (EB + 1,3,5-TEB) as compared to the transformation reaction of pure EB or 1,3,5-TEB. The 1,3,5-TEB undergoes isomerization and a cracking reaction to produce DEB and EB but does not undergo any appreciable disp...
German Sastre - One of the best experts on this subject based on the ideXlab platform.
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Diffusion of Trimethylbenzenes, Toluene, and Xylenes in UWY Zeolite as a Catalyst for Transalkylation of Trimethylbenzenes with Toluene
Journal of Physical Chemistry C, 2018Co-Authors: Jordi Toda, German SastreAbstract:A molecular dynamics study has been carried out on the diffusion of trimethylbenzene (TMB), toluene, and xylene molecules in Transalkylation of TMB and toluene in UWY zeolite, containing crossing 10-ring and 12-ring channels. Two models of UWY have been employed, the pure silica and an acidic form of UWY including Al and Bronsted sites, using a recently parameterized general force field for zeotypes, which reproduce pore diameters within ca. ±0.2 A. Molecular traffic has been observed from the result of TMBs using almost exclusively the 12-ring channels and the preferential location of p-xylene and toluene in the 10-ring channels at high loading (reaction conditions). From the three different 10-ring channels, only p-xylene and toluene can fit in the two smallest channels, whereas m-xylene and 1,2,4-TMB can also diffuse in the largest 10-ring channel. An in-depth analysis of transition-state shape selectivity has been performed, showing that all transition states of Transalkylation of toluene and TMBs can...
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Diffusion of Trimethylbenzenes, Toluene, and Xylenes in UWY Zeolite as a Catalyst for Transalkylation of Trimethylbenzenes with Toluene
2018Co-Authors: Jordi Toda, German SastreAbstract:A molecular dynamics study has been carried out on the diffusion of trimethylbenzene (TMB), toluene, and xylene molecules in Transalkylation of TMB and toluene in UWY zeolite, containing crossing 10-ring and 12-ring channels. Two models of UWY have been employed, the pure silica and an acidic form of UWY including Al and Brønsted sites, using a recently parameterized general force field for zeotypes, which reproduce pore diameters within ca. ±0.2 Å. Molecular traffic has been observed from the result of TMBs using almost exclusively the 12-ring channels and the preferential location of p-xylene and toluene in the 10-ring channels at high loading (reaction conditions). From the three different 10-ring channels, only p-xylene and toluene can fit in the two smallest channels, whereas m-xylene and 1,2,4-TMB can also diffuse in the largest 10-ring channel. An in-depth analysis of transition-state shape selectivity has been performed, showing that all transition states of Transalkylation of toluene and TMBs can be formed in the 12-ring channels. Although this is a disadvantage for the selective production of p-xylene, the previous factor of molecular traffic will contribute to a selectivity of p-xylene over the other xylene isomers. Overall, UWY is suggested as a promising catalyst for Transalkylation of toluene and TMBs
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Diffusion of Trimethylbenzenes and Xylenes in Zeolites with 12- and 10-Ring Channels as Catalyst for Toluene-Trimethylbenzene Transalkylation
The Journal of Physical Chemistry C, 2016Co-Authors: Jordi Toda, Avelino Corma, German SastreAbstract:A molecular dynamics study of the diffusion of trimethylbenzene (TMB) and xylene molecules involved in toluene and TMB Transalkylation reaction has been performed over 6 different pure-silica zeolites, containing 10- and 12-ring channels: BOG, MSE, IWR, SFS, SOF, and UWY. The shape selective properties of these six frameworks have been tested using two different loadings: one loading characteristic of the early stage and another of the late stage of the reaction. The collected data explains the diffusion behavior of these molecules in the zeolite frameworks and allows researchers to obtain trends and also rationalize their performance as candidates for the selective production of p-xylene during Transalkylation of toluene and TMB. UWY appears a promising zeolite that allows the reaction of the TMBs in the 12-ring channels, is able to host the transition states, and favors the preferential diffusion of p-xylene in the 10-ring channels.
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Diffusion of Trimethylbenzenes and Xylenes in Zeolites with 12- and 10-Ring Channels as Catalyst for Toluene-Trimethylbenzene Transalkylation
2016Co-Authors: Jordi Toda, Avelino Corma, German SastreAbstract:A molecular dynamics study of the diffusion of trimethylbenzene (TMB) and xylene molecules involved in toluene and TMB Transalkylation reaction has been performed over 6 different pure-silica zeolites, containing 10- and 12-ring channels: BOG, MSE, IWR, SFS, SOF, and UWY. The shape selective properties of these six frameworks have been tested using two different loadings: one loading characteristic of the early stage and another of the late stage of the reaction. The collected data explains the diffusion behavior of these molecules in the zeolite frameworks and allows researchers to obtain trends and also rationalize their performance as candidates for the selective production of p-xylene during Transalkylation of toluene and TMB. UWY appears a promising zeolite that allows the reaction of the TMBs in the 12-ring channels, is able to host the transition states, and favors the preferential diffusion of p-xylene in the 10-ring channels
Rinaldo Poli - One of the best experts on this subject based on the ideXlab platform.
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Reactions of Diethylamine and Ethylene Catalyzed by PtII or Pt0 – Transalkylation vs. Hydroamination
European Journal of Inorganic Chemistry, 2011Co-Authors: Pavel A. Dub, Aurélien Béthegnies, Rinaldo PoliAbstract:PtBr2/nBu4PBr (without solvent) or K2PtCl4/NaBr (in water), previously shown to efficiently catalyze the hydroamination of ethylene by aniline, are poor catalysts for the hydroamination of ethylene by diethylamine. A DFT study on the hydroamination mechanism indicates that the energetic span of the C2H4/Et2NH catalytic cycle is close to that of the C2H4/PhNH2 cycle. The poor performance is attributed to rapid catalyst degradation with reduction to metallic platinum. The produced Pt 0 , on the other hand, catalyzes a Transalkylation process, partially transforming Et2NH into Et3N, EtNH2, and NH3. The latter process is inhibited by C2H4. Mechanistic considerations on the Pt 0catalyzed Transalkylation process are presented.
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Reactions of diethylamine and ethylene catalyzed by Pt II or Pt 0 : Transalkylation vs. hydroamination
European Journal of Inorganic Chemistry, 2011Co-Authors: Pavel A. Dub, Aurélien Béthegnies, Rinaldo PoliAbstract:PtBr2/nBu4PBr (without solvent) or K2PtCl4/NaBr (in water), previously shown to efficiently catalyze the hydroamination of ethylene by aniline, are poor catalysts for the hydroamination of ethylene by diethylamine. A DFT study on the hydroamination mechanism indicates that the energetic span of the C2H4/Et2NH catalytic cycle is close to that of the C2H4/PhNH2 cycle. The poor performance is attributed to rapid catalyst degradation with reduction to metallic platinum. The produced Pt 0 , on the other hand, catalyzes a Transalkylation process, partially transforming Et2NH into Et3N, EtNH2, and NH3. The latter process is inhibited by C2H4. Mechanistic considerations on the Pt 0catalyzed Transalkylation process are presented.