Carbonization-resistant refractory castables for use in refractory linings

A method comprising:

• introducing a hydrocarbon feedstock, an oxygen-containing gas, and, optionally, steam into a reactor, wherein the reactor comprises:
• a pressure vessel with an interior wall;
• a refractory lining inside the reactor, wherein the refractory lining comprises:
• a first layer comprising a brick refractory,
• a second layer comprising a refractory castable, wherein the refractory castable comprises an aggregate and a binder, wherein the binder comprises CaO·6Al2O3 and less than 1 wt % of a hydratable calcium aluminate, and
• a third layer comprising a fiber refractory, wherein the second layer is between the first and third layers, and wherein the third layer is closest to the interior wall;
• and
• reacting the hydrocarbon feedstock, the oxygen-containing gas, and the steam, if present, in the reactor to produce a product.