| 2-ethylanthraquinone is one of the most important2-alkylanthraquinone. It is one kind offine chemical raw materials and has a wide range of applications in various fields, especiallyin the use as the catalyst for the production of hydrogen peroxide with the anthraquinonemethod. In the traditional two-step reaction, the use of liquid acid catalyst generates a largeamount of waste acid, which pollutes the environment and makes too much trouble for thepost-process. So it is very important to explore a new type of catalyst and synthesis processfor the green synthesis of2-ethylanthraquin.Based on the former research works, the best suitable modification condition weredetermined: the heating power of the microwave radiation was390W, the heating time of themicrowave radiation was15min; the drying power of microwave radiation was325W, thedrying time of microwave radiation was20min. One-step reaction of ethyl benzene withphthalic anhydride was catalyzed by Hβ zeolites modified under the best microwaveradiation conditions to synthesize2-ethylanthraquinone. The optimal reaction conditionswere fixed by orthogonal experiment and single factor study, that is, H-exchange times was1; n(ethyl benzene):n(phthalic anhydride) was6:1; reaction temperature was240oC; reactiontime was6h; the percentage of catalyst was14.34%in weight. Then the yield of2-ethylanthraquinone could reach up to25.99%, the conversion of phthalic anhydride was55.13%and the selection of2-ethylanthraquinone was47.14%.One-step Friedel-Crafts reaction of ethyl benzene with phthalic anhydride for2-ethylanthraquinone was achieved over Hβ zeolites modified respectively byAl2(SO4)3·18H2O,(NH4)2SO4, Fe(NO3)3·9H2O, Ce(NH4)2(NO3)6, Ce(NO3)3·6H2O andTi(SO4)2under ion-exchange, common impregnation and ultrasonic impregnation. On thebase of the catalytic performance of modified zeolite, it can be discovered that the ultrasonic impregnation was the best modification method. The catalytic performance of Hβ zeolitesmodified by Ce(NO3)3·6H2O was optimal and the best modified concentration was0.4g-Ce2O-13·(g-zeolite). The yield of2-ethylanthraquinone could reach up to26.54%, theselection of2-ethylanthraquinone was54.01%, and the conversion of phthalic anhydride was49.14%. The modified zeolites were characterized by means of NH3-TPD, Py-IR and XRD.The results show that strong acid sites were the active sites for the reaction and the maincatalytic active sites were B acid but L acid and B acid could catalyze synergistically thereaction. The modified zeolites supported with highly dispersed or amorphous componentexhibited the best catalytic performance.Then Hβ zeolites were modified by inorganic acids (sulfuric acid, nitric acid andphosphoric acid) and organic acids (citric acid, maleic acid and tartaric acid) undermicrowave radiation. The catalytic performance of Hβ zeolites modified by maleic acid wasoptimal and the best modified concentration was0.1mol·L-1.2-ethylanthraquinone yield andselection was20.15%and39.10%, and the conversion of phthalic anhydride was51.53%. Thecatalytic performance of Hβ zeolites modified by two groups of combination including maleicacid with Ce(NO3)3·6H2O and (NH4)2SO4with Ce(NO3)3·6H2O were investigated. Thecatalytic performance of Hβ zeolites modified by second group was better and2-ethylanthraquinone yield and selection was24.46%and59.82%, and the conversion ofphthalic anhydride was40.89%. The best modified concentration of (NH4)2SO4andCe(NO3)3·6H2O was0.05g-(NH4)2SO4·(g-zeolite)-1and0.4g-Ce2O3·(g-zeolite)-1.In the paper, the inactive zeolites were regenerated by four methods. The best regenerationmethod was calcining at550oC for5h before drying by microwave radiation. The catalyticactivity of reused zeolites decreased significantly after being regenerated8times. Finally, theseparation and purification methods of the reaction product were researched.2-ethylanthraquinone could be separated with petroleum ether and recrystallized withisopropanol. The purity of2-ethylanthraquinone could reach up to more than99%. |
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