The Study On The Nitration Of Simple Aromatic Compounds Catalyzed By Solid Acid

Using solid acids as catalysts in organic synthesis was one of the important research fields in chemistry and chemical engineering. By adding right solid acid as catalyst in reaction systems the reaction yield and selectivity could be improved. Nitration of aromatic compounds was one of the most important and widely studied in fine organic synthesis reactions, and industry still largely relies upon early technology involving mixtures of nitric acid and sulfuric acid. However there were many disadvantages: low selectivity, corrosive and hard to separate, causing pollution in mixed-acid nitration. Using solid acid for the nitration of aromatic compounds was one of the technologies for rising green chemical synthesis.The dissertation is consisted two parts. First, synthesis of MCM-41 mesoporous molecular sieves by hydrothermal and characterization by XRD and IR. Second, the study on the activities of MCM-41, Al-MCM-41, ZSM-5, zeolite B, SAPO-11, NH4Y, ReY, SSY, and heteropoly acid (H3PMo12O40 and H3PW12O40) in the nitration of benzene , toluene and cholrobenzene.Mesoporous molecular sieve MCM-41 were synthesized from sodium silicate, tetraethyl orthosilicate ( TEOS ), cetyltrimethylammonium bromide ( CTMABr ), the ratio of weigh water to SiO2 is 40. Used tetraethyl orthosilicate ( TEOS ) and sodium aluminate (NaAlO2) as sources of Si and Al, molar composition of the gels subjected to hydrothermal synthesis was as follows: Si / Al = 20, TEAOH / Si = 0.3, CTMABr / Si = 0.2, Water / Si = 60, the Al-MCM-41 was synthesized. All the samples were characterized by X-ray diffraction ( XRD ) and fourier transformed infrared ( FT - IR ), and the results were consistent with those in literatures.For the nitration of benzene, solid acids as MCM-41 (T), MCM-41 (W), ZSM-5 and NH4-Y had better catalytic activities. When used MCM-41 (T) as catalyst , aoptimization was as follows: n ( nitration ) / n ( benzene ) = 2.5 : 1, W ( benzene ) /W ( catalyst) = 35.1 : 1, and reacted for 7 hours in 76 ℃. The yield of nitrobenzene was 85.6 %. For the nitration of toluene, ReY and ZSM-5 in high ratio of silicon hadbetter catalytic activities. The ratio of nitric acid to toluene could influence the selectivity and the yield of the nitrotoluene. With the nitric acid ratio reducing, the regioselectivity would rising. The Wp- / Wo- would rise to a better level when n ( nitric acid ) / n (toluene ) equals 0.6. The Wp- / Wo- was 2.30 when ReY was used as the catalyst, anda optimization was as follows: n (nitric acid ) / n (toluene ) = 1.5 : 1, W (toluene ) / W( catalyst ) = 8.7 : 1, reacted for 8 hours in 80℃, nitrotoluene yield was 62.7% and the Wp- / Wo- was 1.14. For the nitration of cholrobenzene, the catalysis activity would be found out when the temperature was high. MCM-41 ( T ) had the highest catalysis activity with 100℃, nitrocholrobenzene yield reached 27.2 % and the Wp- / Wo-was 1.21 when n (nitric acid) / n ( cholrobenzene ) = 1 : 1, W ( cholrobenzene ) / W (catalyst )= 22.1 : l,and reacted for 7 hours.