Dehydration Of 2-(4'-ethylbenzoyl) Benzoic Acid To 2-Ethylanthraquinone Over β Catalysts

2-Ethylanthraquinone (2-EAQ) is an important intermediate for the synthesis of hydrogen peroxide, pharmaceuticals, pesticides, and dyes. With the increasing demands for hydrogen peroxide in the international market, it needs to increase the production of 2-EAQ. The traditional manufacture process of 2-EAQ consists of two reaction steps: The second step is the dehydration of 2-(4' -ethylbenzoyl) benzoic acid (BE acid), which commonly catalyzed by concentrated H2SO4 or oleum. In the traditional process, a large amount of waste acid is generated, which hazards to environments, human being and production system. Therefore, an alternative process, which is environmentally benign is desired. Using solid acid catalysts may be a very promising way for the synthesis of 2-EAQ considering their activity, selectivity and re-usabilityIn the paper, the dehydration of BE acid into 2-EAQ over zeolite catalyst, including H-β , H-Y and H-ZSM-5, H-M and H-MCM-22 catalysts, was carried out in a batch reactor. Among the solid catalysts, a H-B zeolite shows the best catalytic performance. By optimizing the catalyst preparation and reaction parameters, a selectivity to 2-EAQ as high as 98.5 % is achieved. These results indicate that the H-B zeolite is an environmentally friendly catalyst alternative to the concentrated H2SO4 or oleum for the dehydration of BE acid reaction. In our study we come to the following conclusion:1. The dehydration of BE acid into 2-EAQ was catalyzed over H-β , H-Y and H-ZSM-5, H-M and H-MCM-22. Among the catalysts, a H-B shows the best catalytic performance. The difference of catalytic performance may be due to the difference of pore structure. Over H-B catalyst, the conversion of BE acid is 99.5%, the selectivity to 2-EAQ is up to 97.0%.2. H-B zeolite which was modified by HNO3 show better catalytic performance. The SiO₂/Al₂O₃ molar ratio has a great effect on the conversion of BE acid and the selectivity to 2-EAQ.The optimal reaction conditions over H-B (107) are BE acid to H-B zeolite weight ratio 3.0-3.5, reaction temperature 260 ℃-280 ℃, reaction time 1.5 h. The conversion of BE acid can reach 99.5%, and the selectivity to 2-EAQ is up to 97.2%.3. The dehydration of BE acid into 2-EAQ was investigated over H-β catalyst modified by HNO3 solution, the different feed-in methods and the reaction conditions have great influence on the conversion of BE acid.4. When H-fi zeolites (Si/Al = 15.1) was treated by a proper concentration of citric acid, its surface acid properties will change in the way that: 1) the amount of Lewis acid sites decrease, 2) the B/L acidity sites increase, 3) the amount of nonframework aluminum decrease. A H-fl zeolites, which was treated by citric acid with different concentration, show excellent catalytic performance. Over H-B-0.75, the conversion of BE acid can reach 97.9%, and the selectivity to 2-EAQ is up to 96.2% at 230 °C.5. In the dehydration of BE acid, the strong B acid sites are the active sites, a proper amount of active sites is needed. The existence of non-framework Al can inhibit the dehydration of BE acid into 2-EAQ.6. The deactivated catalyst can be regenerated by C2H5OH washing at room temperature, and then the catalyst was calcined at 550 °C for 4 h.