Study Of Catalytic Hydrogenation Of Hydroquinone Over Ru/HZSM-5 Catalyst

1,4-Cyclohexanediol is widely used in organic synthesis, fine chemical industry and other fields. In the catalytic hydrogenation process for the preparation of 1, 4-Cyclohexanediol by using hydroquinone as reactant, because the raw materials are cheap and easy to get, the product 1, 4-Cyclohexanediol has higher practicability and economic benefit. It has a very important significance both in the economic point of view and and the research & development of catalyst of Hydrogenation of aromatic compounds.In this paper, the HZSM-5 is taken as the carrier with different Si/Al molar ratio, and supported Ru/HZSM-5 are made up catalysts by using precipitation method and chemical reduction method. And, the influence of morphology & structure of catalyst and particle size & dispersion of active component by 2 kinds of preparation methods is also analyzed and compared in this paper through the use of Characterization methods of BET, TEM and XRD. The results show that the framework of HZSM-5 molecular sieve is not destroyed by two preparation methods, and the active component Ru particles exist as non-crystalline structure. The reduction from Na BH4 to Ru3+ is accompanied by hydrogen generation in chemical reduction method, so compared to that of preparation by precipitation method, the particle size of Ru in the Ru/HZSM-5 catalyst is small and with high degree of dispersion.Under the Ru/HZSM-5 catalytic system prepared by these two methods, and by taking catalytic hydrogenation of hydroquinone as probe reaction experiment, this paper explores the selective effect of the fractional conversion of the reactant hydroquinone and target product 1,4-Cyclohexanediol by the molar ratio and the reaction conditions of silicon and aluminum of molecular sieve HZSM-5, and also the paper compares and analyzes the optimal reaction conditions under these 2 kinds of catalytic system. The molar ratio of Si/Al has a significant influence on the performance of the catalyst, when the Si/Al molar ratio is 740, the content of Br?nsted acid is minimum, and the selectivity of 1,4-Cyclohexanediol in the reaction is the highest, which means the activity of the catalyst is the best. However, the Ru particle size of the catalyst prepared under chemical reduction method is small and dispersed evenly, and the catalyst also gains amorphous ruthenium boron alloy with a small amount of boron during the chemical reduction, so the catalytic property of Ru/HZSM-5 catalyst is better than that prepared under precipitation method. The optimal reaction conditions under Catalyst system prepared by chemical reduction method are as followings: Reaction temperature is 140 ℃, reaction time is 2.5 h, hydrogen pressure is 2.5 MPa and the load of Ru is 1.0 %, under these conditions, the conversion of the reactant is 100 %, and the selectivity of the target product is 91.13 %. While, the best reaction conditions by precipitation method are: Reaction temperature is 160 ℃, reaction time is 2.5 h, hydrogen pressure is 3.0 MPa and the load of Ru is 2.0 %, under these conditions, the conversion of the reactant is 100 %, and the selectivity of the target product is 80.12 %. Therefore, by the combination of product distribution with time-variation under the Ru/HZSM-5 catalytic system, the paper analyzes and explores the path of Hydrogenation reaction of hydroquinone.