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The Contribution to the Study of Kinetics of the Oxidative Dehydrogenation of Isobutyrylaldehyde
Authors: Čičmanec Pavel | Bulánek Roman | Tichý Josef
Year: 2003
Type of publication: článek v odborném periodiku
Name of source: Przemysl Chemiczny
Publisher name:
Place:
Page from-to: 182-186
Titles:
Language Name Abstract Keywords
cze isobutyrylaldehyd, dehydrogenace
eng The contribution to the study of kinetics of the oxidative dehydrogenation of isobutyrylaldehyde Cesium phosphomolybdate, 12MoO(3).Cs2HPO4, precipitated with Cs2CO3, dried 12 h/120 °C, heated 6 h/180°C, 6 h/300°C in 120 L/h air, powdered, compressed to yield 0.25-0.5 mm particles, sp. surface 4.13 m2/g, preoxidized 1 h/523 K with O-2, was used to catalyze oxidative dehydrogenation in [x:14:(86-x) by moles] (x = 2, 3, 4) or (3:9:91) isobutyraldehyde (I)-O-2 -N-2 mixtures, 5 dm3/h (F), at 523 K over 0.02-1.5 g (w) catalyst in a fixed-bed integral reactor, time factor w/F = 14,400-1.08.10(6) g.s/m(3), to yield methacrolein and CO. At the start, the catalyzed reaction went together with homogeneous decomposition of I. In the T-programmed (TP) reaction (297-623 K; 10 K/min; F, 150 mL/min; I/O-2 mole ratio, 3/1, 1/1, 1/3), methacrolein appeared at 100°C and CO2 at 200°C. CO attained max. at 100°C. TP desorption studies showed methacrolein to form on the catalyst surface by the Mars-van Krevelen redox mechanism. Keggin's structure (Cs surrounded by 12 molybdate octahedra) remained unaffected by any reaction conditions. The catalyst was active and selective up to 90% toward methacrolein at about 470 K. Adsorption of (a) / and (b) methacrolein on the fresh catalyst at 80, 100 and 120°C, best reproduced by Langmuir isotherms involving no dissociation of adsorbates, gave ÄHo ÄGo and ÄSo at 298 K (a) -14.8. 33.8 kJ/mol and -163 J/(K mol), (b) -26.8, 28.8 kJ/mol and -185 J/(K mol), resp. isobutyrylaldehyde, dehydrogenation

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