Study On Preparation And Application Of Anthraquinone Hydrogenation Catalyst

Hydrogen peroxide is an important green reagent,only release oxygen and water in the process of use,widely used in pulp bleaching,environmental treatment,organic chemical synthesis,disinfection and a variety of industrial fields.At present,the production of hydrogen peroxide has been industrialized mainly by anthraquinone method,and the main trend of development of anthraquinone method is to improve the efficiency of hydrogenation of anthraquinone and the concentration and quality of hydrogen peroxide.Therefore,the hydrogenation catalyst of anthraquinone method and its process application were explored in this paper.A series of different Pd-M/Al₂O₃monolithic catalysts were prepared by adding metal auxiliaries（Mg and La）to the traditional Pd/Al₂O₃catalysts.The effects of additives（Mg and La）on the structure and hydrogenation performance of traditional Pd/Al₂O₃catalysts were investi-gated.The results showed that the catalysts modified by active metals（Mg and La）showed excellent performance for hydrogenation of anthraquinone.When the addition of Mg reached 2.09 wt.%,the perfor-mance was the best,and the hydrogenation efficiency reached 9.45 g·L^-1.Compared with Pd/Al₂O₃catalyst,the hydrogenation efficiency is increased by 29.8%.The metal additives（Mg and La）increase the specific surface area,decrease the pore volume and average pore diameter,increase the dispersion,and decrease the acid content.In addition,with the increase of La content,the reduction temperature of Pd O decreases and the reduction ability of Pd O increases.When La content was 3.49 wt.%,the hydrogenation efficiency of anthraquinone reached the highest value,and the hydrogenation efficiency was increased by 22.6%.The effects of different alkyl substituents on the hydrogenation activity and thermodynamic equilibrium of anthraquinone molecules in two-step electron transfer hydrogenation were studied.The results show that after the parent anthraquinone is replaced by 2-ethyl,2-tert-butyl and2-tert-amyl,the heat of hydrogenation of alkyl anthraquinone increases obviously.Under the same temperature,the heat of hydrogenation of2-ethyl anthraquinone,2-tert-butyl anthraquinone and 2-pentyl anthraquin-one are-56.5 k J·mol^-1,-63.1 k J·mol^-1,-70.2 k J·mol^-1;respectively.Under the condition of 328.15 K,the parent anthraquinone can be completely converted to hydroanthraquinone,and the equilibrium conversion is 100%.However,at the same temperature,the equilibrium conversion of 2-ethyl-anthraquinone,2-tert-butyl anthraquinone and 2-tert-pentyl anthraquinone decrease successively,which are 83.06%,60.58%and 58.18%,respectively.With the increase of alkyl substituent carbon chain,the solubility of anthraquinone derivatives in organic solvents increases,which can increase the concentration of anthraquinone carrier in the working solution,and then improve the hydrogenation efficiency of the hydrogenation reaction in the working solution.However,with the increase of alkyl substituent carbon chain,the hydrogenation equilibrium conversion of anthraquinone decreases accordingly.Therefore,the selection and optimization of anthraquinone carrier requires comprehensive consideration of the solubility of anthraquinone in the working solution and the thermodynamic equilibrium of the hydrogenation reaction of anthraquinone,so that the working solution can achieve the highest hydrogenation efficiency.The results show that the solubility of2-tert-amyl anthraquinone is much higher than that of 2-ethyl anthraquinone.By changing the content of 2-tert-pentyl anthraquinone in the working solution,the content of active anthraquinone in the working solution was significantly increased.The results show that the hydrogenation efficiency of anthraquinone is significantly increased and the degradation of active anthraquinone is decreased.The best hydrogenation efficiency and selectivity were obtained when the working solution of 2-ethylanthraquinone:2-tert-pentylanthraquinone was 3:2.