Oxidative Coupling Of Methane Over NaF/Sm₂O₃ Catalysts

Methane is the main component of natural gas, its activation and conversion has drawn much attention in recent years. Take the prospect and environment protection in consideration,utilization of methane resource is of significance. Oxidative Coupling of Methane is one of the main routes for methane direct conversion .Since 1982,many researchers have focused on the study of this reaction.The purpose of this thesis lies in :first ,to improve the activity and stability of Sm^Oj Catalysts;second .to decrease the reaction temperature.The catalytic performance of the NaF/ SirbO.i catalysts were investigated.The main results obtained are as follows:l.OCM performance over NaF/ Sm2O3 catalystsOCM performance over NaF/ Srr^Oj catalysts has been investigated.The results show that the catalyst has higher activity for OCM.At 823K,conversion of methane is 22.3%,and yield of Ci is 9.2%.But with rising of reaction temperature, yield of C2 decrease.The higher of C2 ocured at lower temperature.this for inherent activity of catalyst at lower temperature. The addition of NaF improve conversion of methane and selectivity of C2,decrease selectivity of CO2,and promote yield of C2.The activity of OCM is enchanced to some extent.But with the addition of NaF,the temperature with highest activity of catalyst rises.Comparing the activity of catalysts by different methods,it is found that mixing method is better than other method,and catalyst prepared with higher calcinations temperature has better OCM performanc than that prepared with lower calcinations temperature.2.The optimum reaction conditions of OCM1.The optimum reaction conditions of OCM is that space rate is 4000h-1 .the reaction temperature is 700C, and the reaction pressure is atmosphere, .At this conditions a 31.8% of CFU conversion with 49.5% of C2 selectivity was obtained on NaF/Sm2O3 catalyst.2.A 14.2% of C2 average yields was obtained after 50h with higherstability,and the activity of catalyst does not decrease abvioustly.3.Performance of Carbon dioxide as oxidant for the conversionof methane over NaF/Sm2O31 .The effect of partial pressure of CO2 on the reactionWith the increase of partial pressure of CO2. conversion of methane was promoted,when the partial pressure of CO2 reach 30KPa, conversion of methane is maxium.The partial pressure of CO2 increased furtherly, conversion of methane change very little,but selectivity and yield of C2 promoted.The results shows that the increase of partial pressure of CO2 favors the reaction.2.The effect of reaction temperature on the reactionWith the increase of reaction temperature,conversions of CH4 and CO2 and the selectivity of C2 promoted,in the meantime,the ratio of ethylene and ethane promoted also,this means that part of ethylene formed from ethane dehydrogenation.At 820C, a 4.71% of CH4 conversion with 94.5% of CT selectivity was obtained on NaF/SirbOj catalyst. This means higher temperature favors this reaction .it also suggests that higher temperature is favourable for the activity of CO2 on the surface of catalyst.