THE EFFECT OF CHLORIDE-IONS ON A LI+-MGO CATALYST FOR THE OXIDATIVE COUPLING OF METHANE

被引:53
作者
LUNSFORD, JH
HINSON, PG
ROSYNEK, MP
SHI, CL
XU, MT
YANG, XM
机构
[1] Department of Chemistry, Texas A and M University, College Station
关键词
D O I
10.1006/jcat.1994.1141
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
At Cl/Li atomic ratios approaching unity, Li+-Mgo-Cl- catalysts undergo a marked change in behavior with respect to the oxidative coupling of CH4 to form C2H4 and C2H6 hydrocarbons. Most significant are the large C2H4/C2H6 ratios that may be obtained, primarily as a result of the enhanced activity for the oxidative dehydrogenation of C2H6. The presence Of Cl- ions at the appropriate level modifies the catalyst so that it no longer functions as a strongly basic oxide. In particular, the catalyst is not poisoned by CO2, which normally dominates the kinetic behavior of a Li+-MgO catalyst. The intrinsic activity for CH3 . radical generation over a properly chlorided Li+-Mgo catalyst is less than that of a normal catalyst, but after poisoning by CO2, the activities of the two catalysts are comparable. At the typical reaction temperature Of 650-degrees-C, chlorine is slowly lost from the catalyst, but this chlorine may be replaced by adding a small amount of HCl intermittently to the feed stream. At temperatures as low as 625-degrees-C, a CH4 conversion of 29% and a C2+ selectivity of 60% may be achieved. (C) 1994 Academic Press, Inc.
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页码:301 / 310
页数:10
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