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Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4

Paper ID Volume ID Publish Year Pages File Format Full-Text
39249 45815 2015 10 PDF Available
Title
Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4
Abstract

•Pd/AlPO4 oxidises butan-2-ol into butanone at temperatures around 40 °C.•Above 200 °C, Pd/AlPO4 converts completely butan-2-ol into carbon dioxide.•Butan-2-ol conversion exhibits a hysteresis in activity versus O2 concentration.•Self-sustained oscillations in butan-2-ol oxidation were displayed below 100 °C.•During oscillatory regime the reaction produces exclusively methyl ethyl ketone.

Palladium loaded AlPO4 catalysts were synthesised and characterised by XRD, IR, UV–vis spectroscopy, temperature programmed desorption (TPD) and temperature programmed surface reaction (TPSR). The Pd2+ ions of the dispersed palladium on the amorphous surface of AlPO4 are in D4h symmetry. They can partially be reduced into Pd0 even in dynamic conditions by a mixture of butan-2-ol and oxygen. TPD/TPSR showed that the active sites are formed by the couple PdO/Pd. The presence of PdO on the surface favours the production of methyl ethyl ketone (MEK). The CO2 formation was never observed below 100 °C. Moreover, desorption of the MEK takes place in two waves arising from two different types of sites. Only the reactivity of the first set of sites which are located around 80 °C was considered in the present study. As a matter of fact, the oxidation of butan-2-ol into MEK (<1.3%) at 74.2 °C describes a counter-clockwise hysteresis attributed to a bistability induced by the competition between the redox processes that the surface and the reagents undergo. This sensibility of the catalyst to the parameters governing the reaction resulted in an oscillating oxidation of butan-2-ol. Spontaneous oscillations of the MEK production (αone) appear around 85 °C and stop before 100 °C. Oscillations of the temperature of the catalyst bed were also recorded but their amplitude never exceeds 7 °C. An oscillatory regime appears also for butan-2-ol pressures ranging from 0.61 to 1.65 kPa and for a total flow rate between 80 and 260 mL min−1. The oscillating oxidation of butan-2-ol is accompanied by a significant enhancement of the methyl ethyl ketone production.

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Keywords
Pd(x)/AlPO4; TPD/TPSR; Butan-2-ol oxidation; Hysteresis loop; Oscillating oxidation
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Surface reactivity and self-oscillating oxidation of butan-2-ol over palladium loaded AlPO4
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 503, 25 August 2015, Pages 84–93
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
Online Support
Any Questions? feel free to contact us