Step Changes and Deactivation Behavior in the Continuous Decarboxylation of Stearic Acid

Abstract

Deoxygenation of dilute and concentrated stearic acid over 2% Pd/C beads was performed in a continuous reactor at 300 °C and 20 bar pressure of Ar or 5% H2/Ar. Stable operation was obtained in 5% H2 atmosphere, with 95% conversion of 10 mol % dilute stearic acid in dodecane and 12% conversion of pure stearic acid. Deactivation took place in H2-deficient gas atmosphere, probably as a result of the formation of unsaturated products and coking in the pore system. Transient experiments with step changes were performed: 1 h was required for the step change to be visible in liquid sampling, whereas steady states were achieved after a total of 2.5–3 h. Postreaction analysis of the spent catalyst revealed that a deactivation profile was formed downward over the catalyst bed.

Deoxygenation of fatty acid to produce diesel-like hydrocarbons: A review of process conditions, reaction kinetics and mechanism

“…Mature understandings on the influences of specific process conditions are yet to be established in view of the complex reactions involved. However, some recent works reported managed to shed some light on this area [48,50,60].…”

“…Pd, Pt and Ni on γ-Al 2 O 3 have been investigated for deoxygenation of waste fat containing a mixture of oleic acid and tripalmitin in the presence of solvent under hydrogen atmosphere. It has been observed that Pd/γ-Al 2 O 3 catalyst is more active than the Pt/γ-Al 2 O 3 catalyst and also more selective for production of the C17 and C15 diesel-like hydrocarbons [60]. The higher activity was due to the higher content of active metal (Pd) in the Pd/γ-Al 2 O 3 catalyst than the active metal (Pt) in the Pt/γ-Al 2 O 3 catalyst.…”

“…10. [60] reported that fatty acid deoxygenation in the presence of Pd/C catalyst using reaction atmosphere with small quantity of H 2 in inert gas (5% H 2 in argon or 5% H 2 in helium) gave higher catalytic activities compared to those using inert or rich hydrogen atmospheres. This was because the presence of a small quantity of H 2 in inert gas in the reactions generated lower amounts of unsaturated hydrocarbons and aromatic hydrocarbons leading to coke formation and also generated a smaller molecular weight compounds in the product mixture.…”

“…Complete stearic acid conversion with 98% selectivity to n-heptadecane was achieved after 5 h. Besides, the use of Pd/C catalyst for deoxygenation of C 18 free fatty acid in heptadecane has also been studied using fed-batch reactor [79]. Continuous processes of solventless deoxygenations of stearic acid over Pd/C catalyst were successfully carried out either under inert atmosphere or under the flow of H 2 in Ar [60,80]. Stearic acid conversions of around 12-15% with n-heptadecane (C 17 H 36 ) as the main liquid product were achieved using these processes.…”

Deoxygenation of Palmitic Acid to Produce Diesel-like Hydrocarbons over Nickel Incorporated Cellular Foam Catalyst: A Kinetic Study

“…It could also be produced through water gasshift reaction and methanation [28,29] in which molecules of H 2 from dehydrogenation reactions react with molecules of other gaseous products, i.e., CO 2 and CO (by-products from decarboxylation and decarbonylation), as given in the following reactions;…”