81-20-9Relevant articles and documents
Nitration of aromatics with dinitrogen pentoxide in a liquefied 1,1,1,2-tetrafluoroethane medium
Fauziev, Ruslan V.,Kharchenko, Alexandr K.,Kuchurov, Ilya V.,Zharkov, Mikhail N.,Zlotin, Sergei G.
, p. 25841 - 25847 (2021/08/09)
Regardless of the sustainable development path, today, there are highly demanded chemical productions still operating that bear environmental and technological risks inherited from the previous century. The fabrication of nitro compounds, and nitroarenes in particular, is traditionally associated with acidic wastes formed in nitration reactions exploiting mixed acids. However, nitroarenes are indispensable for industrial and military applications. We faced the challenge and developed a greener, safer, and yet effective method for the production of nitroaromatics. The proposed approach comprises the application of an eco-friendly nitrating agent, namely dinitrogen pentoxide (DNP), in the medium of liquefied 1,1,1,2-tetrafluoroethane (TFE) - one of the most non-hazardous Freons. Importantly, the used TFE is not emitted into the atmosphere but is effortlessly recondensed and returned into the process. DNP is obtainedviathe oxidation of dinitrogen tetroxide with ozone. The elaborated method is characterized by high yields of the targeted nitro arenes, mild reaction conditions, and minimal amount of easy-to-utilize wastes.
2,6-dimethylnitrobenzene synthesis method
-
Paragraph 0015-0026, (2019/05/02)
The invention relates to a method for continuously synthesizing 2,6-dimethylnitrobenzene in a microtubular reactor. The method comprises: (1) immersing a microtubular reactor in an oil bath, wherein an outlet pipe is connected to a liquid-liquid separator, and an inlet pipe is connected to a feeding pump; (2) preparing a mixed acid from 98% nitric acid and 98% sulfuric acid according to a molar ratio of sulfuric acid to nitric acid of 2-4; (3) beating the mixed acid and m-xylene into the microtubular reactor at a certain flow rate by using a two-feeding method, and adjusting the flow rate to achieve a molar ratio of nitric acid to m-xylene of 1.1-1.3; and (4) after completing the reaction, discharging the material to the liquid-liquid separator, carrying out alkali washing on the organic phase, carrying out water washing, and carrying out rectification to obtain the target product. According to the present invention, the reaction kettle is replaced with the microtubular reactor, such that the process is stable, the required space is small, the reaction time is shortened, and the yield of 2,6-dimethylnitrobenzene is improved.
Hydrophobic WO3/SiO2 catalyst for the nitration of aromatics in liquid phase
Kulal,Kasabe,Jadhav,Dongare,Umbarkar
, p. 105 - 113 (2019/02/15)
WO3/SiO2 solid acid catalyst synthesized using sol gel method has shown promising activity (up to 65% conversion) for aromatic nitration in liquid phase using commercial nitric acid (70%) as nitrating agent without using any sulfuric acid. The water formed during the reaction as well as water from dilute nitric acid (70%) was removed azeotropically, however due to the hydrophilic nature of the catalyst, some water gets strongly adsorbed on catalyst surface forming a barrier layer between catalyst and organics. This prevents effective adsorption of substrate on catalyst surface for its subsequent reaction. To improve the activity further, the hydrophilic/hydrophobic nature of the catalyst was altered by post modification by grafting with commercial short chain organosilane (Dynasylan 9896). The modified 20% WO3/SiO2 catalyst when used for o-xylene nitration in liquid phase, showed significant increase in the conversion from 65% to 80% under identical reaction conditions. Catalyst characterization revealed decrease in the surface area of 20% WO3/SiO2 from 356 m2/g to 302 m2/g after grafting with Dynasylan 9896. The fine dispersion of WO3 particles (2–5 nm) on silica support was not affected due to modification. NMR and FTIR study revealed the decrease in surface hydroxyl groups imparting hydrophobicity to the catalyst. Interestingly the total acidic sites of the catalyst remained almost unaltered (0.54 mmol NH3/g) even after modification. Even though, the acidity and other characteristics of the catalyst did not change appreciably, there was a considerable increase in the o-xylene conversion which can be ascribed to the hydrophobic nature of the catalyst.
