Kinetics of l-arabinoseoxidation over supported goldcatalysts with in situcatalyst electrical potential measurements

Abstract

The kinetics of L-arabinose selective oxidation over Au/Al 2 O 3 catalysts was studied with simultaneous in situ catalyst electrical potential measurements. An oxidative dehydrogenation mechanism was proposed and a kinetic model taking into account the catalyst potential changes was developed. The kinetic model was implemented into the three-phase system and validated with the experimental observations. The agreement of the kinetic model to the experimental data, in line with the suggested reaction mechanism, was satisfactory.

Selective Oxidation of Arabinose on Gold Catalysts: Process Design and Techno‐economic Assessment

“…On the contrary, in slightly basic media (pH 8–9) a complete conversion and total selectivity towards arabinoic acid was obtained after 200 min. As expected, the temperature elevation was beneficial for activity causing at the same time the formation of the undesired species 9.…”

“…Arabinose oxidation over gold catalysts was done isothermally at atmospheric pressure in a semi‐batch mode 6 varying temperature, pH, and some catalytic properties to find the optimum reaction conditions. Kusema et al 9 proved that in acidic media the maximum conversion of arabinose was only 23 % after 200 min giving just 46 % selectivity to the desired product with substantial amounts of the intermediate compound (arabinolactone) formed. On the contrary, in slightly basic media (pH 8–9) a complete conversion and total selectivity towards arabinoic acid was obtained after 200 min.…”

“…Kinetics and reaction conditions for oxidation of arabinose are typically studied in batch and semi‐batch laboratory‐scale reactors 6, 9, even if there are successful examples of continuous operation 30. Bitter and co‐workers 30 did not adjust the pH of the reaction media along the reactor length, thus operating in a pH drift mode.…”

“…Moreover, application of noble metal catalysis allows their reuse in batch reactors or stable operation in continuous reactors. In this context, utilization of gold is even more beneficial as it is not prone to over‐oxidation, contrary to such noble metals as palladium or platinum 9.…”

Catalytic Oxidation Pathways for the Production of Carboxylic Acids from Biomass

“…Higher catalyst activity and selectivity to arabinonic acid were achieved with Au/Al 2 O 3 than Pd /Al 2 O 3 due to the increase of the amount of by-products on the Pd catalyst [ 133 ]. An oxidative dehydrogenation mechanism was proposed, and a kinetic model taking into account the catalyst potential changes was developed for the selective oxidation of L -arabinose over Au/ Al 2 O 3 catalysts [ 134 ]. Au supported on Al 2 O 3 was revealed to be an effective catalyst for the oxidation of D -galactose to galactonic acid with molecular oxygen at 60 °C and a slightly alkaline pH value (8-10) [ 135 ].…”