1.4 Direct Conversion of Methane for C–O and C–C …
9
on a catalyst that was formed by subjecting MgO and Li 2 CO 3 on an MgO support
to pretreatment at 732 K under oxygen (Li/MgO) [55]. Further details are given in
Chapter 5.
1.4.2.2 C–C Bond Formation via Non-Oxidative Reactions of Methane
The formation of C–C bonds to produce C 2
+ hydrocarbons can also proceed in the
absence of oxygen. These non-oxidative reactions are considered to be dehydrogenation reactions, since they produce hydrogen and C 2
+ hydrocarbons simultaneously.
In this book, non-oxidative reactions of methane are classified into the following
three categories based on their products:
(1) Non-oxidative coupling of methane
(2) Dehydroaromatization of methane
(3) Methylation of hydrocarbons with methane
As mentioned above, hydrogen is commonly produced along with the C 2
+ hydrocarbons in these reactions. The formation of hydrogen makes the non-oxidative reactions less thermodynamically favorable than oxidative reactions such as the oxidative
coupling of methane.
(1) Non-oxidative coupling of methane
In the non-oxidative coupling of methane, a heterogeneous or homogeneous catalyst
generates •CH 3 or M–CH 3 as the key reaction intermediate. Typically, ethane and
ethylene are produced together with hydrogen. However, heterogeneous catalysts
often yield aromatic hydrocarbons at high reaction temperatures. Further details are
given in Chapter 5.
(2) Dehydroaromatization of methane
The dehydroaromatization of methane is typically carried out at around 900 K using
transition metal ions such as Mo and W supported on and/or exchanged into zeolites [16, 19] or supported metal catalysts [56]. The main products are benzene and
naphthalene, with lower molecular weight hydrocarbons such as ethylene also being
formed as initial reaction products. The key reaction intermediates for C–C bond
formation and the reaction mechanism for the formation of aromatic hydrocarbons
are described in Chapter 6.
(3) Methylation of hydrocarbons with methane
C–C bond formation can also proceed via the reaction of methane with any hydrocarbon, including methane. For example, superacids can act as homogenous catalysts
to catalyze the self-coupling of methane at near room temperature. Such reactions
produce low-molecular-weight hydrocarbons in solution, such as C 2 H 6 in the solution of FSO 3 H–SbF 5 . The hydrogen produced by the reaction escapes into the gas
phase [57], as shown in reaction (1.10).
2 CH 4
C 2 H 6 + H 2
(1.10)
9
on a catalyst that was formed by subjecting MgO and Li 2 CO 3 on an MgO support
to pretreatment at 732 K under oxygen (Li/MgO) [55]. Further details are given in
Chapter 5.
1.4.2.2 C–C Bond Formation via Non-Oxidative Reactions of Methane
The formation of C–C bonds to produce C 2
+ hydrocarbons can also proceed in the
absence of oxygen. These non-oxidative reactions are considered to be dehydrogenation reactions, since they produce hydrogen and C 2
+ hydrocarbons simultaneously.
In this book, non-oxidative reactions of methane are classified into the following
three categories based on their products:
(1) Non-oxidative coupling of methane
(2) Dehydroaromatization of methane
(3) Methylation of hydrocarbons with methane
As mentioned above, hydrogen is commonly produced along with the C 2
+ hydrocarbons in these reactions. The formation of hydrogen makes the non-oxidative reactions less thermodynamically favorable than oxidative reactions such as the oxidative
coupling of methane.
(1) Non-oxidative coupling of methane
In the non-oxidative coupling of methane, a heterogeneous or homogeneous catalyst
generates •CH 3 or M–CH 3 as the key reaction intermediate. Typically, ethane and
ethylene are produced together with hydrogen. However, heterogeneous catalysts
often yield aromatic hydrocarbons at high reaction temperatures. Further details are
given in Chapter 5.
(2) Dehydroaromatization of methane
The dehydroaromatization of methane is typically carried out at around 900 K using
transition metal ions such as Mo and W supported on and/or exchanged into zeolites [16, 19] or supported metal catalysts [56]. The main products are benzene and
naphthalene, with lower molecular weight hydrocarbons such as ethylene also being
formed as initial reaction products. The key reaction intermediates for C–C bond
formation and the reaction mechanism for the formation of aromatic hydrocarbons
are described in Chapter 6.
(3) Methylation of hydrocarbons with methane
C–C bond formation can also proceed via the reaction of methane with any hydrocarbon, including methane. For example, superacids can act as homogenous catalysts
to catalyze the self-coupling of methane at near room temperature. Such reactions
produce low-molecular-weight hydrocarbons in solution, such as C 2 H 6 in the solution of FSO 3 H–SbF 5 . The hydrogen produced by the reaction escapes into the gas
phase [57], as shown in reaction (1.10).
2 CH 4
C 2 H 6 + H 2
(1.10)