  We investigate limit models resulting from a dimensional analysis of quite
general heterogeneous catalysis models with fast sorption (i.e.\ exchange of
mass between the bulk phase and the catalytic surface of a reactor) and fast
surface chemistry for a prototypical chemical reactor. For the resulting
reaction-diffusion systems with linear boundary conditions on the normal mass
fluxes, but at the same time nonlinear boundary conditions on the
concentrations itself, we provide analytic properties such as local-in time
well-posedness, positivity and global existence of strong solutions in the
class $\mathrm{W}^{(1,2)}_p(J \times \Omega; \mathbb{R}^N)$, and of classical
H\"older solutions in the class $\mathrm{C}^{(1+\alpha, 2 + 2\alpha)}(\overline
J \times \overline{\Omega})$. Exploiting that the model is based on
thermodynamic principles, we further show a priori bounds related to mass
conservation and the entropy principle.
