The use of DRIFTS-MS and kinetic studies to determine the role of acetic acid in the palladium-catalyzed vapor-phase synthesis of vinyl acetate

Journal Article · Thu Jul 01 00:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1210· OSTI ID:5621591

Augustine, S M; Blitz, J P ^[1]

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1. Quantum Chemical Corp., Cincinnati, OH (United States)

Supported palladium catalyzes the synthesis of vinyl acetate (VA) by oxyacetylation of ethylene. Alkali promoters increase activity and selectivity. The role of acetic acid (HOAc) in these processes is not well understood. Activation energy studies show that HOAc alters the catalyst site and lowers the reaction barrier to VA formation. After correction for this effect, the kinetics reveal that as a reagent HOAc is zero order. This is probably due to a strong adsorption of HOAc and Pd which forms the catalyst active phase. Detailed spectroscopic studies support this conclusion. The surface processes on a supported vinyl acetate catalyst were studied using a method which couples diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with mass spectrometry (MS). The DRIFTS-MS technique combines the capability of selectively analyzing IR-active surface species with sensitive detection of transient reaction products. By comparing the catalyst with mixtures of palladium acetate powder physically dispersed in potassium chloride, it is determined that the active phase on the catalyst is a form of palladium acetate. Compound formation is consistent with the strong chemisorption of HOAc on Pd. Kinetic analysis of temperature-programmed reaction(TPRxn) data suggests that Pd metal or metal oxide adjacent to the active site is important in the reaction mechanism. 25 refs., 10 figs., 2 tabs.

• OSTI ID: 5621591
• Journal Information: Journal of Catalysis; (United States), Vol. 142:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ACETIC ACID ESTERS
CHEMICAL PREPARATION
PALLADIUM
CATALYTIC EFFECTS
ABSORPTION SPECTROSCOPY
ACETIC ACID
ACTIVATION ENERGY
CATALYST SUPPORTS
CATALYSTS
CHEMICAL REACTION KINETICS
CHEMISORPTION
MASS SPECTROSCOPY
PROMOTERS
CARBOXYLIC ACID ESTERS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
ELEMENTS
ENERGY
ESTERS
KINETICS
METALS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PLATINUM METALS
REACTION KINETICS
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties