Methylation of benzene with methanol over HZSM-11 and HZSM-5: A density functional theory study

Wen, Zhenhai; Yang, Daqiang; He, Xuan; Li, Yunsheng; Zhu, Xuedong

doi:10.1016/j.molcata.2016.07.051

Cited by 33 publications

(27 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[22][23][24][25] Despite the ubiquity of arene methylation reactions in industrial processes, there are few studies contrasting arene methylation mechanisms with CH3OH and CH3OCH3 and fewer studies elucidating methylation mechanisms across a wide range of methylbenzene reagents. Brønsted-acid-catalyzed alkylation reactions occur via one of two distinct mechanisms 6,[26][27][28][29][30][31] : a sequential mechanism (also known as the dissociative or indirect mechanism) or a concerted mechanism (also known as the associative or direct mechanism). In the sequential mechanism, the methylating agent first methylates the zeolite to form a surface methoxy species (CH3-Z) preceding the methylation of an alcohol, alkene, or arene:…”

Section: Introductionmentioning

confidence: 99%

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

et al. 2019

View full text Add to dashboard Cite

This study uses periodic density functional theory (DFT) to determine the reaction mechanism and effects of reactant size for all 20 arene (C6-C12) methylation reactions using CH3OH and CH3OCH3 as methylating agents in H-MFI zeolites. Reactant, product, and transition state structures were manually generated, optimized, and then systematically reoriented and reoptimized to sufficiently sample the potential energy surface and thus identify global minima and the most stable transition states which interconnect them. These systematic reorientations decreased energies by up to 50 kJ mol −1 , demonstrating their necessity when analyzing reaction pathways or adsorptive properties of zeolites. Benzene-DME methylation occurs via sequential pathways, consistent with prior reports, but is limited by surface methylation which is stabilized by co-adsorbed benzene via novel cooperativity between the channels and intersections within MFI. These co-adsorbate assisted surface methylations generally prevail over unassisted routes. Calculated free energy barriers and reaction energies suggest that both the sequential and concerted methylation mechanisms can generally occur, depending on the methylating agent and methylbenzene being reacted-there is no consensus mechanism for these homologous reactions. Intrinsic methylation barriers for step-wise reactions of benzene to hexamethylbenzene remain between 75-137 kJ mol −1 at conditions relevant to methanol-to-hydrocarbon (MTH) reactions where such arene species act as co-catalysts. Intrinsic methylation barriers are similar between CH3OH and CH3OCH3 suggesting that both species are equally capable of interconverting between methylbenzene species. Additionally, these methylation barriers do not systematically increase as the number of methyl-substituents on the arene increases and the formation of higher methylated arenes is thermodynamically favorable. These barriers are significantly lower than those associated with alkene formation during the aromatic cycle, suggesting that aromatic species formed during MTH reactions either egress from the catalyst-depending on that zeolite's pore structure-or become trapped as extensivelysubstituted C10-C12 species which can either isomerize to form olefins or ultimately create polyaromatic species that deactivate MTH catalysts.

show abstract

Section: Introductionmentioning

confidence: 99%

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Simultaneously, the selectivities to the C 8 -C 9 aromatics decrease and then increase (Figure 7B). Besides the cracking and hydrogen transfer, the side-chain hydrogenolysis of bulky aromatics molecules can also produce small alkanes with aid of H 2 [51,52]. For example,…”

Section: Influence Of Preparation Methods On the Aromatization Of Cofeeding N-butane With Methanolmentioning

confidence: 99%

“…The obvious increase in the methane production with the reaction temperature indicates that cracking is also favored, as the cracking of alkanes is endothermic. Besides the hydrogenolysis of bulky aromatics molecules, dealkylation can also occur because of an obvious decrease in the C 8 -C 9 aromatics formation between 425-475 • C. For instance, the C 6 H 5 + species, which is formed via the demethylation of polymethyl aromatics, could connect with the zeolite framework to compensate for the negative charge in the acid sites, hindering the passage of the reactants and products, and decreasing the reactivity of the catalyst [51]. Therefore, the conversion (ca.…”

Section: Influence Of Preparation Methods On the Aromatization Of Cofeeding N-butane With Methanolmentioning

confidence: 99%

Co-Aromatization of n-Butane and Methanol over PtSnK-Mo/ZSM-5 Zeolite Catalysts: The Promotion Effect of Ball-Milling

et al. 2018

View full text Add to dashboard Cite

The ball-milling (BM) method benefits the stabilization and dispersion of metallic particles for the preparation of the PtSnK–Mo/ZSM-5 catalyst. Based on the TPR, H2-TPD, XPS, and CO-FTIR results, the Pt–SnOx and MoOx species were formed separately on the BM sample. During the aromatization of cofeeding the n-butane with methanol, the yield of the aromatics is 59 wt.% at a n-butane conversion of 86% at 475 °C over the Pt Mo BM catalyst. The more weak acid sites also contribute to the aromatics formation with the less light alkanes formation. For the Pt Ga catalysts, the slow loss of activity suggests that the BM method can restrain the coke deposition on the Pt-SnOx species, because of a certain distance between the Pt–SnOx and GaOx species on the surface of ZSM-5.

show abstract

“…Among various kinds of zeolite catalysts, H-ZSM-11 has similar pore dimensions to H-ZSM-5 with straight intersecting channels and elliptical pore size of 0.53 × 0.54 nm [ 15 , 16 , 17 ]. Its diffusion resistance is lower than H-ZSM-5 [ 18 ]; thereby, H-ZSM-11 showed a higher catalytic activity for catalytic cracking [ 19 ], aromatization, isomerization [ 20 ], and methanol-to-hydrocarbons [ 21 ] than HZSM-5. Nevertheless, catalytic pyrolysis of LDPE with H-ZSM-11 has rarely been investigated, unlike H-ZSM-5.…”

Section: Introductionmentioning

confidence: 99%

Waste-to-Fuels: Pyrolysis of Low-Density Polyethylene Waste in the Presence of H-ZSM-11

et al. 2021

View full text Add to dashboard Cite

Herein, the pyrolysis of low-density polyethylene (LDPE) scrap in the presence of a H-ZSM-11 zeolite was conducted as an effort to valorize plastic waste to fuel-range chemicals. The LDPE-derived pyrolytic gas was composed of low-molecular-weight aliphatic hydrocarbons (e.g., methane, ethane, propane, ethylene, and propylene) and hydrogen. An increase in pyrolysis temperature led to increasing the gaseous hydrocarbon yields for the pyrolysis of LDPE. Using the H-ZSM-11 catalyst in the pyrolysis of LDPE greatly enhanced the content of propylene in the pyrolytic gas because of promoted dehydrogenation of propane formed during the pyrolysis. Apart from the light aliphatic hydrocarbons, jet fuel-, diesel-, and motor oil-range hydrocarbons were found in the pyrolytic liquid for the non-catalytic and catalytic pyrolysis. The change in pyrolysis temperature for the catalytic pyrolysis affected the hydrocarbon compositions of the pyrolytic liquid more materially than for the non-catalytic pyrolysis. This study experimentally showed that H-ZSM-11 can be effective at producing fuel-range hydrocarbons from LDPE waste through pyrolysis. The results would contribute to the development of waste valorization process via plastic upcycling.

show abstract

Methylation of benzene with methanol over HZSM-11 and HZSM-5: A density functional theory study

Cited by 33 publications

References 48 publications

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

Co-Aromatization of n-Butane and Methanol over PtSnK-Mo/ZSM-5 Zeolite Catalysts: The Promotion Effect of Ball-Milling

Waste-to-Fuels: Pyrolysis of Low-Density Polyethylene Waste in the Presence of H-ZSM-11

Contact Info

Product

Resources

About

Methylation of benzene with methanol over HZSM-11 and HZSM-5: A density functional theory study

Cited by 33 publications

References 48 publications

Mechanism and Kinetics of Methylating C6–C12 Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

Mechanism and Kinetics of Methylating C6–C12 Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

Co-Aromatization of n-Butane and Methanol over PtSnK-Mo/ZSM-5 Zeolite Catalysts: The Promotion Effect of Ball-Milling

Waste-to-Fuels: Pyrolysis of Low-Density Polyethylene Waste in the Presence of H-ZSM-11

Contact Info

Product

Resources

About

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites

Mechanism and Kinetics of Methylating C₆–C₁₂ Methylbenzenes with Methanol and Dimethyl Ether in H-MFI Zeolites