Hydrogenolysis of methyl formate over copper on silica. II. Study of the mechanism using labeled compounds

Journal Article · Tue Jul 01 04:00:00 EDT 1986 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(86)90068-0· OSTI ID:5595972

Monti, D M; Cant, N W; Trimm, D L; Wainwright, M S

Deuterium labeling has been used to investigate processes occurring during the conversion of methyl formate to methanol over silica supported copper at 293 to 419 K. Unlabeled and labeled methyl formates (CH/sub 3/OCDO and CD/sub 3/OCHO) react with hydrogen and deuterium at identical rates. The product distribution is that expected for successive simple additions without exchange at methyl or aldehyde positions (e.g., the initial products of the reaction between CH/sub 3/OCHO and D/sub 2/ are CH/sub 3/OD and CHD/sub 2/OD). The only complication is a rapid transesterification equilibrium (e.g., CH/sub 3/OCHO + CHD/sub 2/OD in equilibrium CHD/sub 2/ + CH/sub 3/OD. Control experiments show that this process, and a similarly rapid CH/sub 3/OH + D/sub 2/ in equilibrium CH/sub 3/OD + HD equilibration, are catalyzed by copper and not the silica support. The mechanism suggested for hydrogenolysis involves formation of a surface hemiacetal species which, on cleavage of the C-O bond, gives surface methoxy groups and formaldehyde. It is unclear if the slow step is this bond cleavage or the addition step which forms the intermediate. During reaction between CH/sub 3/OCHO and H/sub 2//D/sub 2/ mixtures equilibration to HD is 10 to 30 times faster than hydrogenolysis. Added CO inhibits both hydrogenolysis and equilibration but the latter is inhibited to a greater extent. Both effects can be explained in terms of the displacement of adsorbed hydrogen by adsorbed CO with equilibration being affected more because of its higher kinetic order in adsorbed hydrogen. The lower concentration of surface hydrogen concentration in the presence of CO also reduces the rate of hydrogenation of the formaldehyde intermediate causing its diversion into a polymeric by-product which poisons the catalyst.

• Research Organization: Macquarie Univ., North Ryde, Australia
• OSTI ID: 5595972
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 100:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

090221* -- Alcohol Fuels-- Chemical Synthesis-- (1976-1989)
10 SYNTHETIC FUELS
ADSORPTION
ALCOHOLS
ALDEHYDES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CARBOXYLIC ACID SALTS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COPPER
DATA
DEUTERIUM
ELEMENTS
EXPERIMENTAL DATA
FORMALDEHYDE
FORMATES
HIGH TEMPERATURE
HYDROGEN
HYDROGEN ISOTOPES
HYDROGENATION
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
MEDIUM TEMPERATURE
METALS
METHANOL
MINERALS
NONMETALS
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
REACTION INTERMEDIATES
REACTION KINETICS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENTS