Selective Hydrogenation Of Phenol To Cyclohexanone Over Palladium Based Catalyst

Cyclohexanone (C6H10O)which molecular weight98.14is a kind of colorless and transparent solvent, with its melting point-45℃and boiling point155.6℃. As an important raw material in organic chemical industry, cyclohexanone is mainly used for the synthesis of epsilon-caprolactam and adipic acid witch are important reaction intermediates for nylon6and nylon66. More then90%of cyclohexanone is synthesized by oxidation process of cyclohexane, while the technics include such problems as high energy consumption, corrosion of equipments, serious pollution and safety in production. Therefore a new kind of environment-friendly and efficient method for selective hydrogenation of phenol to cyclohexanone demands to be developed.In the process of selective hydrogenation of phenol to cyclohexanone, cyclohexanone can be further hydrogenated to other side product as cyclohexanol. In the condition of100%conversion of phenol, it is very difficult to make the selectivity of cyclohexanone approach to 100%. Consequently, to prepare a new kind of catalyst with both high activity and high selectivity means really important.Pd as a noble metal witch is widely used in the catalyst for selective hydrogenation shows low catalytic activity to carbonyl, and shows high catalytic property on selective hydrogenation of phenol. We using phenol as raw material and Pd based catalyst, investigate the effect of following factors on catalytic property of Pd/C catalyst for the selective hydrogenation of phenol, such as feed ratio, solvent variety, supporter, reaction temperature and hydrogen pressure. Then we get these best reaction parameters:supported with acticarbon, with water as green solvent, reaction temperature at85℃and hydrogen pressure at0.1MPa. Effect of Pd loading on catalytic properties of the Pd/C catalyst for the selective hydrogenation of phenol is also simply discussed. Effect of particle size on catalytic properties of the Pd/C catalyst for the selective hydrogenation of phenol gets focused on.Following conclusions are made: the smaller the particle size is(with higher dispersion), the higher catalytic activity can be. In addition, a new kind of pretreatment(pretreated with different concentration of HNO3) witch can control the particle size of Pd is found. At last, effect of different Pd based bimetallic catalysts and reduction temperature on catalytic properties of the catalysts for the selective hydrogenation of phenol is further investigated. We can draw these conclusions as follow:the addition of second kind metal can improve the catalytic activity of Pd/C catalyst, among these Pd-Au/C bimetallic catalyst show best catalytic property totally; the higher the reduction temperature of Pd-Au/C bimetallic catalyst is, the bigger the particle size of Pd can be, then the lower dispersion of Pd can be, Pd and Au tends to form alloy, witch can reduce the catalytic activity of selective hydrogenation of phenol.