Synthesis And Characteristic Of Cryptophane A, E And Their Sensitivity To Methane

Methane is an inflammable and explosive gas, it's the main constituent of the mine gas. Fire damp explosion usually lead to magnitude economic losses and safety accidents. And therefore it's necessary to monitor the content of methane in mine gas. At present, sensors used to detect methane in mine gas mainly based on thermo catalytic, gas sensory semiconductor, infrared absorption and light-interference types. But these kind of sensors have long testing period, poor accuracy, prone to be poisoned, inconvenient maintenance and other shortages. Thus, develop a safe, reliable and high sensitivity methane sensory system is of great practical meaning. Cryptophanes are an important new type material, they play an important role in life sciences, material sciences, molecular electronics, sensors and other fields. It's detected in recent years that Cryptophane A and Cryptophane E are sensitive to methane, and they are promising to be used in next new generation methane sensors.Cryptophane A and E were prepared from vanillin via a three-step method. Their structures were characterized by means of ¹H NMR, ¹³C NMR, UV, fluorescence spectra etc. A fiber-core mismatch fiber methane sensor was designed and built, and methane sensing mechanisms of Cryptophane A and E were discussed. Main results of the thesis are as follows:(1) The application of methane monitoring technologies, development of new type mine gas monitoring technologies, synthesis of Cryptophane A and E and their sensing characteristics to methane both internal and abroad were reviewed respectively.(2) Cryptophane A and E were prepared from vanillin via a three-step method, and the yields were 3.08% and 9.79% at the optimal synthesis and isolation technology. The optimal synthesis and isolation technology was as follows: firstly, 1,2-bis(4-formyl-2-methoxyphenoxy) ethane, 1,3-bis(4-formyl-2-methoxyphenoxy) propane were prepared with excess vanillin and refluxed for 22h at 80℃, and they were used respectively to dissolve and recrystal the yields, filtered and vacuum dried. Secondly, NaBH₄(M_NaBH4 /M_Compound2=6:1)was added slowly, and refluxed for 25h at 60℃, dilute HCl and methanol/H₂O(volume ratio,1:1) were used to rinse and filter the yields respectively after fully reacted. And thirdly, refluxed in 90% formic acid for 4h at 70℃, and evaporate to dryness, then CH₂Cl₂ was taken to extract, and isolated by chromatographic column on silica gel (CH₂Cl₂/acetone=10:1). (3) 4.41(d, 6H, CH_a), 3.41(d, 6H, CH_e), 36.78(C_a,e) and 4.65(d, 6H, CH_a), 3.43(d, 6H, CH_e), 36.13(C_a,e) observed in the NMR test proved respectively that Cryptophane A and Cryptophane E were successfully synthesized. The maximum fluorescence emission wavelengths were 440nm and 435nm. Cryptophane A and E. In CH₂Cl₂ solvent, UV absorption peaks wereλ₁=236nm,λ₂=284nm for Cryptophane A,λ₁=234nm,λ₂=286nm for Cryptophane E.(4) The sensing experiment for methane showed that the best incidence angle for the methane fiber sensor was 15°, the suitable sensitive length are 3mm to Cryptophane A and 8mm to Cryptophane E. The adsorption and desorption time of the sensitive film to N₂/CH₄ when the velocity of the gas mixture was 100ml·min^-1 both 80s.