Ammonia and graphite interaction

[gasgod]

Does anyone know what is the interaction between ammonia and graphite at 800-1200 C under 100-400 torr?

 

[kenvlach]

One thermodynamically possible reaction is ammonia decomposition/methane formation:

4 NH₃ + 3 C(gr.) --> 2 N₂ + 3 CH₄ delta G_Rxn,298K = -20.6 kcal/mol

As there is an increase in gas volume associated with this rxn., it should be favored by the reduced pressure.

 

[nbucska]

HCN ??? <nbucska@pcperipherals.com>

 

[kenvlach]

There are several C_xN_yH_z compounds, but they don't seem thermodynamically likely, i.e., have delta G_f > 0.

Take a look at the thermo data for 25^o in Perry's, 6th Edn. p. 3-149. I don't believe that the increase in T will make a qualitative change. Most of the C_xN_yH_z compounds will thermally decompose, especially with a solid surface to catalyze the reaction.

 

[25362]

Although ammonia is expected to be at least partly dissociated in the absence of catalysts, books say that with carbon, at read heat, ammonia reacts to give ammonium cyanide.

 

[gasgod]

Thank you for the responses so far, what I observed in my reactor systems are, the porous solid graphite turns into powderly carbon compound. This could be that the graphite is slowly decomposing according to reaction:
4 NH3 + 3 C(gr.) --> 2 N2 + 3 CH4 delta GRxn,298K = -20.6 kcal/mol
The graphite as it looses methane it become more porous and began to collapse.