OP-II-3

OP-II-13catalyst bed was 6 mm. Three different liquid flow rates and seven different gas flowrates were investigated to perform the reaction in the trickle flow regime.Fig. 1. Production rate (left) and selectivity (right) of hydrogen peroxide at -10°C and 10 bar,gas composition in the inlet CO 2 /O 2 /H 2 respectively 80%/16%/4%.Results are shown in Fig. 1 (left). Experiments carried out by feeding themethanol at 1 ml/min and the gas between 0.11 and 0.37 min/ml behave differentlywith respect to the case a larger liquid flow rate (2 ml/min) and the same gas flow. Ata lower liquid flow rate, i.e. larger liquid residence time, the productivity (moles ofH 2 O 2 /min) is larger, as expected. On the other hand, gas flow rate affectsproductivity non-linearly, passing through a maximum. Note that a larger H 2 O 2 flowrate at the lower liquid flow rate imply a gain in concentration. It also confirms theopportunities of affecting the reaction course in a TBR by suitably combining vapourliquidequilibrium, interphase mass-transfer, and catalyst surface renewal. The majorconcern in direct synthesis is poor selectivity because of the complex reactionnetwork, involving product degradation steps and by-products (H2O). The assumptionis that independent manipulation of gas and liquid contact time, as well as theconcentrations of the gases, provides opportunities to control the reaction paththrough its mechanism. Fig. 1 (right) shows how contact time between catalyst andliquid-gas components can affect the selectivity. The results achieved are about twotimes higher than in the reactor used to develop and test the catalyst [3], which wasoperated by continuously flowing gas through the liquid and solid, well stirred, batchsuspension. The full results with other catalysts are presented in the full manuscript.References[1]. Samanta, C. Direct synthesis of hydrogen peroxide from hydrogen and oxygen: An overview ofrecent developments in the process. Applied Catalysis A: General. 2008, 350, 2, 133-149.[2]. Basse, C.; Jaewger, B.; Elem.-Degussa Sci-Newsletter, 2008, 17, 4.[3]. Menegazzo, F.; Burti P.; Signoretto, M.; Manzoli, M.; Vankova, S.; Boccuzzi, F.; Pinna, F.;Strukul, G. Effect of the addition of Au in zirconia and ceria supported Pd catalysts for the directsynthesis of hydrogen peroxide. Journal of Catalysis. 2008, 257, 2, 369-38.123