Study On Microwave Catalytic Highly-effective Nonoxidative Direct Conversion Of Methane To CO_x-free Hydrogen

Hydrogen is a high energy density clean energy with great potential,which can improve the energy structure and achieve low carbonization of the energy structure.However,hydrogen is a secondary energy source.There is no mineral hydrogen in nature,and it must be produced from hydrogen-containing substances.Most of the industrial hydrogen is produced by the steam reforming of methane.The resulting impure hydrogen is accompanied by a large amount of CO_x production,which not only causes the greenhouse effect but also cannot be directly used in hydrogen-oxygen fuel cells.Methane nonoxidative direct conversion hydrogen production?MCD?can obtain hydrogen with no CO_x,which has attracted wide attention,but this method has the disadvantages of high energy consumption and easy carbon deactivation of the catalyst.And how to realize the efficient and low energy consumption of MCD hydrogen production has become a difficult problem.microwave heating is widely used in heterogeneous catalytic reactions due to its rapid,efficient and uniform characteristics.In this paper,to study MCD reaction,a microwave field is introduced under the irradiation of microwave.We study the effects of Mo₂C/Si C,Me/?Mo₂C/Si C?-ZSM-5?Me=Ni,Co,Mg?and Mo₂C/Ti C catalysts on the catalytic performance of MCD reaction under different reaction conditions.These reaction conditions include metal loading,reaction time,microwave output power,methane flow rate,methane concentration and reaction bed temperature,etc.The catalysts were characterized by XRD,BET,SEM,TEM-EDX,RAMAN,etc.The kinetic parameters of direct conversion of methane to hydrogen production under microwave irradiation were also calculated.The following conclusions can be drawn from the study:?1?Study on the performance of Mo₂C/Si C catalytic methane cracking and nonoxidative direct hydrogen production under microwave conditions.The reaction conditions are:2 g 45%Mo O₃/Si C catalyst?in-situ carbonization before reaction?,pure methane as feed gas,microwave output power of 800 W,gas flow rate of50m L/min,reaction temperature of 650?.The conversion rate of methane is 40%,and it begins to deactivate after 45 min.The apparent activation energy is 73.2 k J/mol.?2?Study on the performance of Me/?Mo₂C/Si C?-ZSM-5?Me=Ni,Co,Mg?catalytic methane cracking for direct hydrogen production under microwave conditions.The reaction conditions were as follows:2 g 3 wt%Ni Co Mg/?45%Mo₂O₃/Si C?-ZSM-5?3:1?catalyst?in situ carbonization before reaction?,pure methane was used as feedstock gas with a microwave output power of 800 W,the flow rate of the gas was 50 m L/min,the reaction temperature was 650?.The methane conversion was obtained to be about 60%and 960min decreased to 60%.The apparent activation energy is 45.7 k J/mol.?3?Study on the performance of direct hydrogen production Mo₂C/Ti C methane cracking under microwave conditions.The reaction conditions were as follows:2 g50%Mo O₃/Ti C catalyst?in situ carbonization before reaction?,pure methane as raw gas,the output power of microwave was 800 W,the flow rate of gas was 50 m L/min,the reaction temperature was 650?,and the methane conversion was 67%and490min decreased to 40%.The apparent activation energy is 50.4 k J/mol.