Direct Observation of Cyclic Carbenium Ions and Their Role in the Catalytic Cycle of the Methanol‐to‐Olefin Reaction over Chabazite Zeolites

Xu, Shutao; Zheng, Anmin; Wei, Yingxu; Chen, Jingrun; Li, Jinzhe; Chu, Y. P.; Zhang, Mozhi; Wang, Quanyi; Zhou, You; Wang, Jinbang; Deng, Feng; Liu, Zhongmin

doi:10.1002/anie.201303586

Cited by 213 publications

(242 citation statements)

References 31 publications

Supporting

Mentioning

229

Contrasting

Order By: Relevance

“…86, 87 Wulfers and Jentoft investigated the occurrence of hydrocarbon pool species in H-ZSM-5 and H-beta by using in situ UV/Vis spectroscopy. 422 Detailed insight into these mechanisms is of utmost importance to address the factors controlling the selectivity towards C2 and C3 species. The growth of the band could be correlated with the increase in ethene formation during an induction period.…”

Section: View Article Onlinementioning

confidence: 99%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

View full text Add to dashboard Cite

Zeolites are versatile and fascinating materials which are vital for a wide range of industries, due to their unique structural and chemical properties, which are the basis of applications in gas separation, ion exchange and catalysis. Given their economic impact, there is a powerful incentive for smart design of new materials with enhanced functionalities to obtain the best material for a given application. Over the last decades, theoretical modeling has matured to a level that model guided design has become within reach. Major hurdles have been overcome to reach this point and almost all contemporary methods in computational materials chemistry are actively used in the field of modeling zeolite chemistry and applications. Integration of complementary modeling approaches is necessary to obtain reliable predictions and rationalizations from theory. A close synergy between experimentalists and theoreticians has led to a deep understanding of the complexity of the system at hand, but also allowed the identification of shortcomings in current theoretical approaches. Inspired by the importance of zeolite characterization which can now be performed at the single atom and single molecule level from experiment, computational spectroscopy has grown in importance in the last decade. In this review most of the currently available modeling tools are introduced and illustrated on the most challenging problems in zeolite science. Directions for future model developments will be given.

show abstract

Section: View Article Onlinementioning

confidence: 99%

Advances in theory and their application within the field of zeolite chemistry

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Several other correlations between aliphatic ( 13 C/ 1 H: 20-30/2.2-2.4 ppm) and aromatic moieties Figure 3c reveal the presence of various HCP-type intermediates;t hat is,c onjugated polyenes,m ethylated neutral benzenes and benzeniums, which are known to be formed in the alkene and arene cycles of the HCP mechanism (Scheme S1 and Table S1). [2,[11][12][13][32][33][34][35] However,t he lack of signals in the 65-90 ppm region signifies the absence of aC H 3 OCH 2 CH 2 OR (R = H, CH 3 )m oiety,a spreviously proposed by Fana nd coworkers. [17] Based on the above-described results,w ep ropose in Scheme 1apathway for the formation of the first CÀCbond during the initial stages of the MTO process.F irst, the CH 3 group of SMS,formed by methylation of aBrønsted acid site (denoted as ZeOH, Scheme 1), interacts initially with another molecule of methanol/DME (Species A in path a, Scheme 1).…”

mentioning

confidence: 94%

“…Thefollowing features were observed:i )18-22 ppm aliphatic methyl groups,ii) 50-65 ppm methoxy groups,iii)90-105 ppm acetal moiety,i v) 120-155 ppm (methylated) aromatic/olefinic groups,a nd v) 170-185 ppm carbonyl groups. [2,[11][12][13][32][33][34][35] Because of the overlap with spinning side bands,weemployed higher MAS rates to unambiguously identify weak signals at 200 and 220 ppm, indicative for poly-methylbenzenium ions ( Figure S4 and Table S1). Interestingly,w ed on ot observe strong signals around 40 ppm, which indicates the absence of typical sp 3 CH 2 groups.T he strongest aliphatic signal at 52 ppm was due to the methanol, whereas the peaks at 55, 57, and 62 ppm are due to acetate,m ethoxy/SMS,a nd adsorbed (side-on) DME, respectively (Table S1).…”

mentioning

confidence: 99%

Initial Carbon–Carbon Bond Formation during the Early Stages of the Methanol‐to‐Olefin Process Proven by Zeolite‐Trapped Acetate and Methyl Acetate

et al. 2016

View full text Add to dashboard Cite

Methanol-to-olefin (MTO) catalysis is av ery active field of researchb ecause there is aw ide variety of sometimes conflicting mechanistic proposals.A ne xample is the ongoing discussion on the initial C À Cb ond formation from methanol during the induction period of the MTOprocess.Byemploying ac ombination of solid-state NMR spectroscopyw ith UV/Vis diffuse reflectance spectroscopya nd mass spectrometry on an active H-SAPO-34 catalyst, we provide spectroscopic evidence for the formation of surface acetate and methyl acetate,aswell as dimethoxymethane during the MTOp rocess.A saconsequence,new insights in the formation of the first C À Cbond are provided, suggesting ad irect mechanism may be operative,a t least in the early stages of the MTOr eaction.

show abstract

“…Therefore, how the first C−C bond is formed in the induction period remains intriguing. 2,17 Recent studies implied that the direct route, which takes place at a very low rate during the induction period, 20−22 can be eclipsed by traces of impurities. Recent experimental and theoretical study proposed a new mechanism over H-SAPO-34 including methoxylmethy cation (CH 3 O CH 2 + ) intermediate.…”

Section: Introductionmentioning

confidence: 99%

Stability and Reactivity of Intermediates of Methanol Related Reactions and C–C Bond Formation over H-ZSM-5 Acidic Catalyst: A Computational Analysis

Wei

Chen

et al. 2016

J. Phys. Chem. C

View full text Add to dashboard Cite

On the basis of density functional theory including dispersion correction [ωB97XD/6-311+G(2df,2p)//B3LYP/6-311G(d,p)], the thermodynamics and kinetics of the reactions of CH 3 OH and CH 3 OCH 3 over H-ZSM-5 have been systematically computed. For the reaction of the methylated surface (CH 3 OZ) with CH 3 OH, CH 3 OCH 3 formation is kinetically controlled and the competitive formation of CH 2 O + CH 4 is thermodynamically controlled, in agreement with the observed desorption temperatures of CH 3 OH, CH 3 OCH 3 , and CH 2 O under experimental conditions. For the reaction between ZOCH 3 and CH 3 OCH 3 , the formation of the framework stabilized (CH 3 ) 3 O + is kinetically controlled, consistent with the NMR observation at low temperature, and the competitive formation of surface CH 3 OCH 2 OZ + CH 4 is thermodynamically controlled. On the basis of the thermodynamically more favored CH 2 O and CH 3 OCH 2 OZ, there are two parallel routes for the first C−C bond formation, from the coupling of CH 3 OCH 2 OZ with CH 3 OH and CH 3 OCH 3 as well as from the coupling of CH 2 O with CH 3 OH and CH 3 OCH 3 . The most important species is the methylated surface (CH 3 OZ), which can react with CH 3 OH and CH 3 OCH 3 to form the corresponding physisorbed CH 2 O and chemisorbed CH 3 OCH 2 OZ, and they can further couple with additional CH 3 OH and CH 3 OCH 3 to result in first C−C formation, verifying the proposed formaldehyde (CH 2 O) and methoxymethyl (CH 3 OCH 2 OZ) mechanisms.

show abstract

Direct Observation of Cyclic Carbenium Ions and Their Role in the Catalytic Cycle of the Methanol‐to‐Olefin Reaction over Chabazite Zeolites

Cited by 213 publications

References 31 publications

Advances in theory and their application within the field of zeolite chemistry

Advances in theory and their application within the field of zeolite chemistry

Initial Carbon–Carbon Bond Formation during the Early Stages of the Methanol‐to‐Olefin Process Proven by Zeolite‐Trapped Acetate and Methyl Acetate

Stability and Reactivity of Intermediates of Methanol Related Reactions and C–C Bond Formation over H-ZSM-5 Acidic Catalyst: A Computational Analysis

Contact Info

Product

Resources

About