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As necessary preamble for nonlinear control-estimation design, in this study fundamental stationary, transient and robustness characteristics of a spatially distributed tubular throated gasification tristable reactor are studied with efficient PDE-to-ODE discretization. The reactor is described by 15 nonlinear PDEs and has 5 steady-states (SSs): (i) 3 stable ones and (ii) 2 unstable ones. On the basis of process insight and extensive numerical simulation, perturbed initial conditions close to the hypersurface separatrix that divides the basins of attraction of the nominal and recently reported grate stable SSs were identified, verifying: the existence of the hypersurface separatrices that divide the basins of attraction of the stable nominal-H unstable saddle and L unstable saddle-stable extinction SS pairs. The comparison of the shapes and caloric efficiency of the nominal, grate stable as well as high-conversion unstable SS profiles yielded that: (i) the nominal stable SS exhibits the smallest production of undesirable tar, followed by the H unstable SS and the grate stable SS, and (ii) the temperature and biomass concentration profiles of the high-yield unstable SS and the grate stable SS are rather similar, and appreciable different from the nominal stable SS. With transients induced by pos/negative initial profile temperature deviations it was found: (i) which stable SSs is reached, and (ii) what the settling time, damping and profile front displacement are.