| Natural gas is a relatively environmentally friendly high-quality resource,its main component is low carbon alkanes.The molecular structure of alkanes is composed of strong C-C bonds and local C-H bonds.In practical reactions,it is difficult to directly transform into more valuable products.Alkane reforming is used to produce synthetic gas(hydrogen and carbon monoxide),and then the fund-support synthesis reaction(fischer-tropsch reaction)is further converted into various liquid fuels or other organic chemical products.This indirect transformation can effectively utilize alkane resources.Methane dry reforming can prepare syngas by breaking C-H bond,while ethane dry reforming can prepare syngas by breaking C-C bond.At present,the kinetics and reaction mechanism of methane reforming synthetic gas have been studied more mature,but the kinetics and reaction mechanism of ethane reforming synthetic gas are less studied.The reaction mechanism of methane and ethane reforming synthesis gas on nickel catalyst was studied under the control of intrinsic reaction kinetics.The main contents of this paper are as follows:(1)The reaction mechanism of ethane catalytic reforming to syngas on nickel catalyst was studied under the control of intrinsic kinetics.The experimental results show that the forward rate of ethane is linearly related to the partial pressure of ethane,and has no relationship with the partial pressure of co-reactant carbon dioxide and products(hydrogen and carbon monoxide).The accompanying reverse water gas shift reaction is always in equilibrium.The first order rate coefficient of ethane reforming on nickel catalyst decreases slightly with the increase of ethane partial pressure,and at each ethane pressure,the first order rate coefficient of ethane does not depend on CO2CO ratio(PCO2/PCO=6-26)or H2O-H2 ratio(PH2O/PH2=0.6-2.6).The reaction mechanism of reforming of ethane was deduced according to the results of kinetic experiments,and the rate equation of ethane catalysis was also deduced:(?)Ethane rate equation reflects that the forward rate of ethane is only related to the partial pressure of ethane,which is consistent with the kinetic test results.It further shows that the initial C-H bond activation of ethane is a kinetic related step.(2)The C-H bond activation of methane ethane reforming under different reaction conditions was studied under the same conditions,and the C-H activation rate and activation mechanism of methane ethane reforming were compared.Research findings,the C-H bond activation mechanism of methane and ethane reforming is similar,and the C-H bond activation rate catalyzed by methane and ethane is positively correlated with the partial pressure of methane and ethane.It is not affected by co-reactant carbon dioxide and product partial pressure.At the same time,the reverse water-gas shift reaction has been in equilibrium,which provides favorable conditions for the subsequent mechanism derivation.Compared with the first order rate coefficient of methane and ethane reforming on nickel clusters,the first order rate coefficient of methane and ethane catalysis decreases slightly with the increase of their partial pressure.The first order rate coefficient is not affected by the CO2-CO ratio or H2O-H2 ratio at each methane or ethane partial pressure.The rate equation of methane catalysis is derived by the same method:(?)Comparing the rate equations of methane catalysis and ethane catalysis,it is found that the forward rate of methane and ethane are only related to methane partial pressure and ethane partial pressure,which is consistent with the previous experimental results.It is shown that the first step of C-H bond activation is a kinetic step for both methane reforming and ethane reforming... |
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