Study On Monolithic Catalysts And Kinetics For 2-ethylanthraquinone Hydrogenation

H₂O₂ is widely used as a green and efficient oxidizer,and mainly used in medical sterilization,pulp bleach,water treatment,chemical synthesis,propellant,etc.More than 98% H₂O₂ produces by the anthraquinone auto-oxidation?AO?process in the world.The liquid-phase hydrogenation of AQs is the key factor and will affect the economic benefit in AO process.So it is very important to research the Pd-based catalyst with high activity and selectivity.Monolith catalyst combining a number of single and parallel channels.So it has large geometrical surface area,low pressure drop and lower mass transfer resistance,and has been widely used in a fast hydrogenation reaction to improve conversion and selectivity.Pd/oxide/cordierite monolithic catalysts were prepared by the impregnation method to study the species and thicknesses of porous oxide layer on catalytic performance.The results of ICP,XRD,SEM-EDX,XPS and N₂ adsorption-desorption measurements revealed that the Pd penetration depth increased with increasing the thickness of oxide layer,and the catalysts with Al₂O₃ layers had the larger pore size than those with SiO₂ and SiO₂-Al₂O₃ layers.Catalytic hydrogenation of 2-ethyl-anthraquinone?eAQ?,a key step of the H₂O₂ production by the anthraquinone process,over the various monolithic catalysts?60 °C,atmosphere pressure?showed that the monolithic catalyst with the moderate thickness of Al₂O₃ layer?about 6 ?m?exhibited the highest conversion of eAQ?99.1 %?and hydrogenation efficiency?10.0 g ·L-1?.This could be ascribed to the suitable Pd penetration depth and the larger pore size,which provides a balance between the distribution of Pd and accessibility of active sites by the reactants.At the same time,we prepared Pd/Al₂O₃-SiO₂ catalysts with different Si:Al ratios to research the structure and acidity of support in affecting Pd-based catalyst of the AO process.We found that the conversion and selectivity increased allowing the Si:Al ratios decreased,which owe to the acid strength increasing with the Si:Al ratios decreased.So it indicated that the acid strength of oxide layer may also an essential factor for high activity.At last,we researched the kinetic by commercial powder catalyst for 2-ethyl-anthraquinone hydrogenation,and a kinetic equation was established.Which indicated that it was first-order reaction for the concentration of eAQ,and the reaction activation energy was Ea=32.76±1.83 kJ/mol.