Highly reduced MoO sub 3 /Al sub 2 O sub 3 catalysts I. Characterization

Journal Article · Fri Mar 31 23:00:00 EST 1989 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(89)90117-6· OSTI ID:6188801

Chung, Jong-Shik; Zhang, J P; Burwell, Jr, R L ^[1]

---

1. Northwestern Univ., Evanston, IL (USA)

MoO{sub 3}/Al{sub 2}O{sub 3} containing 0.89-7.4% Mo and reduced at 950{degree}C by H{sub 2} (MoO{sub 3}/Al{sub 2}O{sub 3};H{sub 2};950{degree}C) is Mo(O)/Al{sub 2}O{sub 3}. It has been studied and compared with Mo(0)/Al{sub 2}O{sub 3} prepared by Mo(CO){sub 6}/dehydroxylated Al{sub 2}O{sub 3};He,300-500{degree};H{sub 2},650-950{degree} and found to be essentially equivalent in chemisorptive behavior. MoO{sub 3}/Al{sub 2}O{sub 3};H{sub 2},650 has also received some attention. The high purity alumina support treated H{sub 2},950{degree} becomes gray and is reduced by an amount representable as Al{sup 2+}/Al{sup 3+} = 0.0012. It is reoxidized to white material by O{sub 2},800{degree} but not by O{sub 2},650{degree}. Content in O{sub 2} must be kept below 0.03 ppm in the other gases if a clean metallic molybdenum surface is to be maintained for a reasonable period of time. The amount of CO adsorbed at 25{degree}C appears to be a measure of the percentage exposed of Mo(0)/Al{sub 2}O{sub 3}. If a molecule of CO is taken to occupy 1.5 sites, the percentage exposed of Mo varied from 25 to 58%. At 25{degree}C, H{sub 2} is chemisorbed rapidly but rather weakly on Mo(0)/Al{sub 2}O{sub 3}, and at least two forms of activated adsorption exist at higher temperatures. Under the conditions of this work the Mo particles in the samples of Mo(0)/Al{sub 2}O{sub 3} are not carbide but rather,a s evidence by high resolution TEM and EXAFS, metallic bcc Mo.

• OSTI ID: 6188801
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 116:2; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020400 -- Petroleum-- Processing
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BCC LATTICES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYSTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CHEMISORPTION
COLOR
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CUBIC LATTICES
ELECTRON MICROSCOPY
ELEMENTS
HYDROGEN
MICROSCOPY
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
NONMETALS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REDUCTION
REFRACTORY METAL COMPOUNDS
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY SPECTROSCOPY