Silicon carbide (SiC) has many attractive chemical and physical properties, which make it an excellent candidate for preparation of nanoporous membranes, especially those that are used for gas separation and hydrogen production under harsh conditions. Preparation of asymmetric nanoporous SiC membranes using chemical-vapor infiltration/chemical-vapor deposition (CVI/CVD) is described. We use macroporous SiC disks and tubes as supports, and tri-isopropylsilane as the precursor. Experimental data for the permeation and selectivity of the membranes are presented. We also develop two dynamic models to describe the process of preparation of the membranes. The models are shown to provide accurate predictions for the experimental data for the permeation characteristics of the membranes, as a function of the preparation conditions. Moreover, we have used an optimization technique in order to specify the best operating conditions for preparation of high quality SiC membranes. Preparing SiC membrane using the CVD technique operating under the optimal conditions results in significant improvement in the transport properties of the membranes. The SiC membranes that we have been preparing are to be utilized in reactive separation applications with the water-gas shift and methane steam reforming reactions, where the membrane must function in the presence of high-temperature steam.