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The critical role of methanol pressure in controlling its transfer dehydrogenation and the. corresponding effect on propylene-to-ethylene ratio during methanol-to-hydrocarbons catalysis on H-ZSM-5
被引:56
作者:
Arora, Sukaran S.
[1
]
Bhan, Aditya
[1
]
机构:
[1] Univ Minnesota, Dept Chem Engn & Mat Sci, 421 Washington Ave SE, Minneapolis, MN 55455 USA
基金:
美国国家科学基金会;
关键词:
Propylene-to-ethylene ratio;
Dual-cycle;
Formaldehyde;
Prins condensation;
Methanol-to-hydrocarbons;
H-ZSM-5;
CO-REACTION;
METHYLATION REACTIONS;
OLEFINS CONVERSION;
REACTION-MECHANISM;
ZEOLITE CATALYSTS;
DIMETHYL ETHER;
PRODUCT SELECTIVITY;
GAS CONVERSION;
O-COMPOUNDS;
SAPO-34;
D O I:
10.1016/j.jcat.2017.10.014
中图分类号:
O64 [物理化学(理论化学)、化学物理学];
学科分类号:
070304 ;
081704 ;
摘要:
A monotonic increase (2-18) in the effluent propylene-to-ethylene molar ratio as inlet methanol pressure is varied from 52.5 to 0.6 kPa during methanol-to-hydrocarbons catalysis (similar to 30%C conversion) on H-ZSM5 at 673 K reveals methanol pressure as the salient process parameter that allows control over the relative rates of propagation of the olefins- and aromatics-based methylation/cracking events. The enhanced propagation of the olefins-based cycle over its aromatics-based counterpart and consequently, decoupiing of the two catalytic cycles at low influent methanol pressures is observed to persist irrespective of the reaction temperature (623-773 K). Reactions involving formaldehyde co-feeds (3-20 Pa or 0.5-5%C) with low-pressure (0.6 kPa) methanol at 623 K result in a monotonically decreasing trend in propylene-to-ethylene molar ratio from 24.7 in the absence of formaldehyde to 0.8 in the presence of 20 Pa formaldehyde implicating suppressed formaldehyde production from methanol transfer dehydrogenation events at low methanol pressures as the mechanistic basis for the observed effect of enhanced olefin cycle propagation. Co-reacting formaldehyde (11 Pa or 3%C) with propylene (0.1 kPa) on H-ZSM-5 at 623 K results in a 5.5-fold increase in aromatics selectivity suggesting Prins condensation reactions between formaldehyde and olefins are likely involved in aromatics production during methanol-to hydrocarbons catalysis over H-ZSM-5. (C) 2017 Elsevier Inc. All rights reserved.
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页码:300 / 306
页数:7
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