Plasma Coupling Reactions Of CH₃OH And NH₃

Methanol and ammonia are cheap and abundant chemical raw materials. Therefore, the direct synthesis of high value fine chemicals from methanol and ammonia has a great application value and a profound scientific significance. In this paper, dielectric barrier discharge (DBD) has been used to study the CH3OH/NH3 plasma and plasma-catalytic coupling reaction. Some results have been achieved as follows:In plasma system, the spontaneous CH3OH/NH3 plasma coupling reaction can directly synthesize N,N-dimethyl cyanamide [(CH3)2NCN],amino acetonitrile [NH2CH2CN] and N,N-dimethyl amino acetonitrile [(CH3)2NCH2CN]. The by-products contained formamide, ethylene glycol, urotropine and triazole. Experimental results indicate that the optimized reaction conditions for synthesis of nitriles compounds were as follows:a single dielectric barrier discharge reactor with a stainless steel high voltage electrode and a aluminum foil ground electrode,25 W input power,12 kHz discharge frequency,0.02 ml/min CH3OH flow rate,44 mL/min NH3 flow rate and 4.5 s residence time. Under the optimal conditions,12.7% nitriles compounds selectivity with 16.9% methanol conversion have been reached. Beside,the CH3OH/NH3 plasma has been diagnosed by optical emission spectroscopy (OES), the discharge current pulses of CH3OH/NH3 plasma has been recorded by oscilloscope (OSC).In plasma-catalysis system, the packing materials or supported metal catalysts have great effects on methanol conversion and nitriles compounds selectivity. In the case of "support+ plasma", the CH3OH conversion decreased as the following sequence:Na-ZSM-5> ?-Al2O3> TS-1> fumed SiO2> TiO2> SiO2> blank pipe> BaTiO3, but the nitriles selectivity decreased as a different sequence as follow:fumed SiO2> TS-1> SiO2> blank pipe> BaTiO3> ?-Al2O3 > Na-ZSM-5> TiO2. So, the optimal condition for synthesis of nitriles compounds is "SiO2+ plasma" with 30 w input power, where 22.1% nitriles selectivity with 51.5% methanol conversion have been achieved. In the case of "plasma+supported metal catalysts", both the methanol conversion and the nitriles selectivity were lower than the results of "plasma+ SiO2". In addition, the nitriles selectivity obtained in the case of thermal catalysis (pure packing materials or supported metal catalysts) is much lower than the above mentioned results.The transformation of low-carbon alcohol(ethanol> N-propanol?Iso-propanol) with ammonia have been explored by DBD. The spontaneous CH3CH2OH/NH3 plasma coupling reaction can directly synthesize 2-propanone hydrazone and the five-member heterocyclic compounds (pyrazole compounds and imidazole compounds). The spontaneous N-propanol/NH3 plasma coupling reaction can directly synthesize 3-Pentanol and 5-methyl-Pyrazole. The spontaneous Iso-propanol/NH3 plasma coupling reaction can directly synthesize 2-Propanone hydrazone and 2,3-Butanediol.