Propane dehydrogenation on chromia/silica and chromia/alumina catalysts

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1183· OSTI ID:6814875

De Rossi, S; Ferraris, G; Fremiotti, S; Campa, M C; Indovina, V ^[1]; Garrone, E ^[2]

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1. Universita La Sapienza, Rome (Italy)
2. Universita di Torino (Italy)

The catalytic activity of CrO[sub x]/SiO[sub 2] (SC, 0.08 to 0.99% chromium by weight), CrO[sub x]/Al[sub 2]O[sub 3] (AC, 0.16 to 1.55%), and [alpha]-Cr[sub 2]O[sub 3] for the dehydrogenation of propane has been investigated at 723 to 823 K in a flow apparatus. Before catalytic experiments, SC and AC samples were activated with oxygen at 773 K (s.o. treatment) followed or not followed by reduction with CO or H[sub 2] at 623 K. Occasionally, SC samples were dehydrated under vacuum at 1023 K before the s.o. treatment. Assuming all chromium to be in the +6 state after s.o., the average oxidation number of chromium ([bar n]) is [bar n] [approx equal] 2 in SC samples reduced with CO and [bar n] [approx equal] 3 with H[sub 2]. In AC catalysts, [bar n] values progressively increase in consecutive reduction experiments, from [bar n] = 2.2 to [bar n] = 4.2. All catalysts are highly selective to propene and undergo a deactivation process during time on stream. The s.o. treatment completely restores the activity. The reduction mode does not influence the catalytic activity. Surface species formed upon adsorption at room temperature (RT) of CO or NO were studied by IR spectroscopy on CrO[sub x]/SiO[sub 2] submitted to treatments analogous to those used before catalytic experiments. In SC catalysts reduced with CO, the formation of carbonyls and nitrosyls of three different Cr[sup II] species was confirmed. Interestingly, all these species were absent when the sample was (i) reduced with H[sub 2] at 773 K, or (ii) heated with H[sub 2]O after reduction with CO, or (iii) exposed to propane after reduction with either CO or H[sub 2]. Relying on (i) the dependence of the activity on chromium content, (ii) IR results, and (iii) ESR data, it is suggested that mononuclear Cr[sup III] with two coordinative vacancies is the active site for the dehydrogenation of propane. 28 refs., 9 figs., 3 tabs.

• OSTI ID: 6814875
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 148:1; ISSN 0021-9517; ISSN JCTLA5
• 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
ABSORPTION SPECTROSCOPY
ALKANES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
DEHYDROGENATION
ELECTRON SPIN RESONANCE
HETEROGENEOUS CATALYSIS
HYDROCARBONS
MAGNETIC RESONANCE
MINERALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PROPANE
RESONANCE
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SPECTROSCOPY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TRANSITION ELEMENT COMPOUNDS