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Titolo:
A persistent carbenium ion on the methanol-to-olefin catalyst HSAPO-34: Acetone shows the way
Autore:
Song, WG; Nicholas, JB; Haw, JF;
Indirizzi:
Univ So Calif, Loker Hydrocarbon Res Inst, Los Angeles, CA 90089 USA Univ So Calif Los Angeles CA USA 90089 es Inst, Los Angeles, CA 90089 USA Univ So Calif, Dept Chem, Los Angeles, CA 90089 USA Univ So Calif Los Angeles CA USA 90089 pt Chem, Los Angeles, CA 90089 USA Pacific NW Natl Lab, Environm Mol Sci Lab, Richland, WA 99352 USA Pacific NW Natl Lab Richland WA USA 99352 Sci Lab, Richland, WA 99352 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 19, volume: 105, anno: 2001,
pagine: 4317 - 4323
SICI:
1520-6106(20010517)105:19<4317:APCIOT>2.0.ZU;2-8
Fonte:
ISI
Lingua:
ENG
Soggetto:
IN-SITU NMR; CHEMICAL-SHIFT TENSORS; SOLID-STATE NMR; BENZENIUM ION; CHEMISTRY; ZEOLITE; ACIDS; HYDROCARBONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
22
Recensione:
Indirizzi per estratti:
Indirizzo: Nicholas, JB Genentech Inc, 1 DNA Way, S San Francisco, CA 94080 USA Genentech Inc 1 DNA Way S San Francisco CA USA 94080 4080 USA
Citazione:
W.G. Song et al., "A persistent carbenium ion on the methanol-to-olefin catalyst HSAPO-34: Acetone shows the way", J PHYS CH B, 105(19), 2001, pp. 4317-4323

Abstract

In situ C-13 NMR with both CAVERN and pulse-quench methods was used to understand the chemistry of acetone on the silico-aluminophosphate catalyst HSAPO-34. The isotropic shift of [2-C-13]acetone shows that most of the acid sites on this catalyst are weaker than those on aluminosilicate zeolites, but a minority site was resolved with a shift higher than that on zeolite HZSM-5. At elevated temperatures, acetone dimerized to diacetone alcohol and dehydrated to mesityl oxide. Mesityl oxide cracked in the presence of waterto acetic acid and isobutylene. Trimerization of butenes formed a significant amount of a persistent carbenium ion with unusual spectroscopic properties, and this is proposed to be the heptamethylcyclopentenyl cation, the first observation of a persistent carbenium ion on a SAPO catalyst. Chemical shift calculations at the GIAO-MP2 level revealed a discrepancy for one signal of the proposed cation but ruled out an alternative assignment. Methylaromatic formation coincided with cyclopentenyl cation synthesis, supportinga mechanistic proposal for aromatic synthesis on zeolites. Conventional flow reactor studies revealed a high selectivity for C-4 olefins and rapid deactivation with acetone as feed. The results of this investigation are interpreted in the context of methanol-to-olefin (MTO) chemistry on HSAPO-34.

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Documento generato il 30/10/20 alle ore 00:42:38