Basic Research On Preparation And Application Of Feldspar Catalysts For Nonoxidative Conversion Of Methane Into Alkanes And Olefins

In our country,nearly three billion tons of livestock in poultry manure can be generated into nearly 200 billion cubic meters of biogas by resource reuse of biogas.Biogas contains 50～80%methane,and the low-cost industrial resource utilization of biogas has always been a key technology issue for popularization and application of biogas energy engineering.In recent years,significant progress has been made in the nonoxidative conversion of methane to ethylene,aromatics and hydrogen,and a new approach has been opened up for the successful development of new and highly efficient Fe(?)SiO2 catalysts.In this paper,the preparation and application of feldspar-based catalysts which catalyze methane into high hydrocarbons were systematically studied.The effects of different kinds of metal ions on the nonoxidative conversion of methane were investigated systematically using natural albite minerals as the basic raw material for methane nonoxidative conversion.The four kinds of Sr/Ab,Cd/Ab,Ce/Ab and Pb/Ab catalysts were successfully obtained by ion exchange of Sr2+,Cd2+,Ce3+ and Pb2+with Na+ in albite(Ab),and alkali metal sites were determined to be the catalytic sites of albite for methane nonoxidative conversion.Moreover,the ion exchange mechanism of catalyst formation process and catalytic mechanism were presumed.Here are the results below:(1)The alkaline-earth element Sr has little effect on the promotion of albite-catalyzed nonoxidative conversion of methane.XRD,XPS,ICP and TEM results indicated that Sr2+ ion exchanged with Na+ in albite,and entered the alkali metal site of albite without changing the basic structure of albite.Under the optimal experimental conditions of 2.7 wt%Sr/Ab,reaction temperature of 1073 K and feed gas spacevelocity of 1 L/h,the conversion of methane was 4.61%and the selectivity of C2 hydrocarbons was more than 97%and the selectivity of ethylene was 44.54%.(2)The sub-group element Cd has a certain impact on methane nonoxidative conversion catalyzed by albite.XRD,XPS,ICP and TEM results indicated that Cd2+ ion exchanged with Na+ in albite and entered the alkali metal site of albite without changing the basic structure of albite.Under the optimal experimental conditions of 2.9wt%Cd/Ab,reaction temperature of 1073 K and feed gas spacevelocity of 1 L/h,the conversion of methane and the selectivity of C2 hydrocarbons were 6.41%and more than 98%,respectively.Of these,the selectivity of ethylene was 44.67%.(3)The effect of rare earth Ce on the promotion of nonoxidative methane conversion catalyzed by albite is relatively significant.XRD,XPS,ICP and TEM results showed that Ce3+ ion exchanged with Na+ in albite and entered the alkali metal site of albite without damaging the basic structure of albite.Under the optimal experimental conditions of 2.6wt%Ce/Ab,reaction temperature of 1073 K and feed gas spacevelocity of 1 L/h,the conversion of methane and the selectivity of C2 hydrocarbons were 6.98%and more than 98%,respectively.The selectivity of ethylene was 44.72%therein.(4)The main group element Pb has a significant impact on nonoxidative conversion of methane catalyzed by albite.XRD,XPS,ICP and TEM results demonstrated that Pb2+ ion exchanged with Na+ in albite and entered the alkali metal site of albite without demaging the basic structure of albite.Under the optimal experimental conditions of 2.2wt%Pb/Ab,reaction temperature 107 3 K and feed gas spacevelocity 1 L/h,the conversion of methane was 8.19%and the selectivity of C2 hydrocarbons was more than 99%.Moreover,the selectivity of ethylene was 44.95%.To sum up,Pb/Ab has a great effect on albite for nonoxidative conversion of methane,which has a great industrial application prospect.