Synthesis and catalytic properties of chromia pillared clays

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7302575

Brewer, T D

Host clay layer charge and chromium pillaring solution synthesis conditions have a profound effect on the resulting physical properties of chromia pillared clays. Large gallery chromia pillared clays, with gallery heights greater than 10[angstrom], can be obtained from smectite clay hosts of relatively low layer charge. As the host clay layer charge increases, chromia pillared clay gallery heights decrease. Surface areas in excess of 500 m[sup 2]/g have been observed for chromia pillared montmorillonite after calcination at 500[degrees]C. The chromia pillared clays also show interesting thermal stabilities. Chromia pillared clays are unique bifunctional catalysts which exhibit both acidic and redox properties. The chromia pillars, which prop the smectite clay layers apart, are the source of the catalytic activity. The vertical height and lateral spacing of the pillars define a two-dimensional nanoporous environment for possible catalytic shape selectivity. The acidic properties of chromia pillared clays have been examined using decane cracking and a standard gas oil microactivity test as probe reactions. In addition, since chromia is a known dehydrocyclization catalyst, the aromatization of n-octane to p-xylene has been used to study the redox and shape selective properties. While chromia pillared clays do not exhibit exceptional shape selectivity for the n-octane dehydrocyclization reaction, a pore effect on the product distribution has been observed when compared to that of a non-microporous chromia on alumina catalyst. The hydroconversion of n-heptane over a chromia pillared montmorillonite catalyst and an alumina pillared montmorillonite catalyst are also compared. The yield of cracked products closely followed the conversion for the chromia pillared clay catalyst, while the formation of isomerized products was dependent upon the pretreatment temperature in air.

• Research Organization: Michigan State Univ., East Lansing, MI (United States)
• OSTI ID: 7302575
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
CATALYTIC CRACKING
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
CLAYS
CRACKING
DECOMPOSITION
HYDROCARBONS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POROSITY
PYROLYSIS
REDOX REACTIONS
SURFACE PROPERTIES
SYNTHESIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS