*2.1. The Model*

Carbon molecular sieves (CMS) are basically a type of activated carbon, but the area of pore size distribution is very narrow, so it can selectively adsorb according to its molecular size (sieve, see Figure 1). The majority of carbon molecular sieves on the market today are made of anthracite coal with a tightly controlled activation process. The capillary structure can be modified by subsequent heat treatment process including cracking of hydrocarbons in the micropore and partial gasification under strict control conditions. Thus, the carbon molecular sieve obtained has an e ffective pore diameter ranging from 0.4 to 0.9 nm, but the porosity and adsorption capacity will be lower than that of conventional activated carbon. The largest application on an industrial scale is air separation. Surprisingly, surface oxidation by oxygen adsorption does not a ffect the e fficiency of the separation process. It is also used in the process of hydrogen purification or the cleaning of gas mixtures [15–18].

**Figure 1.** Selective adsorption mechanism of CMS material.

In this study, carbon molecular sieves (CMS-240) is selected to study the adsorption process in a column of N2 gas generator working according to PSA pressure change cycle [15–18]. Material CMS-240 means that it can produce 240 m<sup>3</sup>/h.1ton CMS (N2 99.5%) at standard conditions. The capacity of the column is 14 L/minute N2 99.5% at standard conditions.

The construction of a single fixed bed experimental model is shown in Figure 2, including the following main equipment:



**Figure 2.** A single bed model.

The real model of this study is shown in Figure 3. To operate this equipment as a single fixed bed model, herein, we use two valves V1 and V7, and the other valves are completely closed.

**Figure 3.** The experimental equipment system.
