Similarities and Differences in Activation of Small Alkanes by Liquid and Solid Strong Acids: An NMR, MS, and UV Spectroscopic Study

Sommer, Jean; Sassi, Alain; Hachoumy, Mohammed; Jost, Roland; Karlsson, Annika; Ahlberg, Per

doi:10.1006/jcat.1997.1809

Cited by 32 publications

(15 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The product distribution for the n-butane conversion on zeolite H-ZSM-5, which is revealed by 13 C MAS NMR spectroscopy, appears to be similar to that typically observed earlier for conjunct polymerization of olefins and alkanes in concentrated sulfuric acid, [38][39][40] for olefins and alcohols on acidic zeolites, [14,27,42] as well as for n-pentane and n-butane conversion on sulfated zirconia. [16,17] It should be emphasized that isobutane (as well as propane) is produced in the course of all stages of the conjunctpolymerization process rather than only through the pure oligomerization-cracking process (Scheme 2) observed earlier (e.g., for the n-butane isomerization on SZ).…”

Section: Resultssupporting

confidence: 50%

“…Trienes are further protonated and cyclized on the acidic zeolite. This intermolecular process, which is called conjunct polymerization, [38][39][40] gives rise to the stable CPC and an additional amount of propane and isobutane after a long reaction time. Conjunct polymerization provides a method for the formation of both the alkanes with two 13 C labels and 13 Cmultilabeled CPC.…”

Section: Resultsmentioning

confidence: 99%

“…www.chemeurj.org can be rationalized in terms of two processes: oligomerization-cracking and conjunct polymerization, [38][39][40] as depicted in Scheme 2. These processes involve a variety of stages including dimerization (oligomerization) of carbenium ions with equilibrated alkenes, isomerization of the dimer, b scission, hydride transfer from alkanes and oligomeric olefins (and, afterward, from dienes) to carbenium ions, and cyclization.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Luzgin

Stepanov

Arzumanov

et al. 2005

Chemistry A European J

View full text Add to dashboard Cite

By using 13C MAS NMR spectroscopy (MAS = magic angle spinning), the conversion of selectively 13C-labeled n-butane on zeolite H-ZSM-5 at 430-470 K has been demonstrated to proceed through two pathways: 1) scrambling of the selective 13C-label in the n-butane molecule, and 2) oligomerization-cracking and conjunct polymerization. The latter processes (2) produce isobutane and propane simultaneously with alkyl-substituted cyclopentenyl cations and condensed aromatic compounds. In situ 13C MAS NMR and complementary ex situ GC-MS data provided evidence for a monomolecular mechanism of the 13C-label scrambling, whereas both isobutane and propane are formed through intermolecular pathways. According to 13C MAS NMR kinetic measurements, both pathways proceed with nearly the same activation energies (E(a) = 75 kJ mol(-1) for the scrambling and 71 kJ mol(-1) for isobutane and propane formation). This can be rationalized by considering the intermolecular hydride transfer between a primarily initiated carbenium ion and n-butane as being the rate-determining stage of the n-butane conversion on zeolite H-ZSM-5.

show abstract

Section: Resultssupporting

confidence: 50%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Luzgin

Stepanov

Arzumanov

et al. 2005

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…These findings are typical for an acid-catalyzed reaction, proceeding via a pentacoordinated transition state (Scheme 17). This observed regiospecific H/D exchange (which is typical of branched paraffins, where only the hydrogen atoms vicinal to the branching carbon are exchanged) is in agreement with a general mechanism [108,109,[113][114][115] based on the intermediate formation of carbenium ions and olefins (Scheme 18). This concerted mechanism should minimize the effect of differently long alkyl groups, as well as that of primary and secondary C − H groups.…”

Section: A H/d Exchange Of Hydrocarbons Over Metal and Acid Catalystssupporting

confidence: 84%

Isotopic Labeling and Kinetic Isotope Effects

Bauer

2008

Handbook of Heterogeneous Catalysis

View full text Add to dashboard Cite

The sections in this article are Introduction Synthesis and Analysis of Labeled Compounds Kinetic Isotope Effects Applications of Labeled Compounds Carbon Isotopes ( 11 C , 13 C , 14 C ) A Methanol‐to‐Gasoline Reactions; Methylation of Olefins and Aromatics B Isomerization of Alkylaromatics C Isomerization of Olefins and Paraffins D Paraffin Dehydrocyclization E Coke Formation Hydrogen Isotopes ( 2 H , 3 H ) A H / D Exchange of Hydrocarbons over Metal and Acid Catalysts B Deuterium Kinetic Isotope Effects of Hydrocarbon Reactions Oxygen Isotopes ( 17 O , 18 O ) Miscellaneous Isotopes ( 15 N , 29 Si , 35 S ) Conclusions

show abstract

“…In all experiments, no presence of hydrogen or higher alkanes-a sign of methane oligomerization-was found by GC, but SO 2 and CO 2 were detected by mass spectrometry, which arose from the reduction of D 2 SO 4 and the oxidation of methane, respectively. For the formation of these species, we suggest a reaction similar to the one proposed for the activation of isobutane in H 2 SO 4 [34] [Eq. (1)].…”

Section: Resultsmentioning

confidence: 99%

Methane Activation and Oxidation in Sulfuric Acid

et al. 2002

View full text Add to dashboard Cite

In a versatile modular scaffold system, gradient nonwovens of in situ crosslinked gelatin nanofibers (CGN), fabricated by reactive electrospinning, are laminated with perforated layers and nonwovens of thermoplastic non‐crosslinked biodegradable polyesters. The addition of glyoxal to a gelatin solution in a non‐toxic solvent mixture consisting of acetic acid, ethyl acetate, and water (5:3:2 w/w/w) enables the in situ crosslinking of gelatin nanofibers during electrospinning. The use of this fluorine‐free crosslinking system eliminates the need of post‐treatment crosslinking and purification steps typical for conventional CGN scaffolds. The slowly progressing crosslinking of the dissolved gelatin in the presence of glyoxal increases the viscosity of the gelatin solution during electrospinning so that the average diameter of the crosslinked gelatin nanofibers gradually increases from 90 to 680 nm. During the subsequent lamination process, alternating layers of CGN and polycaprolactone (PCL) nonwovens, produced by 3D microextrusion of micrometer‐sized PCL fibers, are bonded together upon heating above the PCL melting temperature. In contrast to the water‐soluble gelatin nanofibers and the comparatively weak CGN, the CGN/PCL/CGN layered biocomposites are water‐resistant and very robust. In such modular scaffold systems, strength, biodegradation rate, and biological functions can be controlled by varying the type, composition, fiber diameter, porosity, number, and sequence of the individual layers. The CGN/PCL multilayer biocomposites can be cut into any desired scaffold shape and attached to tissue by surgical sutures in order to suit the needs of individual patients.

show abstract

Similarities and Differences in Activation of Small Alkanes by Liquid and Solid Strong Acids: An NMR, MS, and UV Spectroscopic Study

Cited by 32 publications

References 20 publications

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Isotopic Labeling and Kinetic Isotope Effects

Methane Activation and Oxidation in Sulfuric Acid

Contact Info

Product

Resources

About

Similarities and Differences in Activation of Small Alkanes by Liquid and Solid Strong Acids: An NMR, MS, and UV Spectroscopic Study

Cited by 32 publications

References 20 publications

Mechanism Studies of the Conversion of 13C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using 13C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Mechanism Studies of the Conversion of 13C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using 13C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Isotopic Labeling and Kinetic Isotope Effects

Methane Activation and Oxidation in Sulfuric Acid

Contact Info

Product

Resources

About

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

Mechanism Studies of the Conversion of ¹³C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using ¹³C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis