Natural gas treating by selective adsorption: Material science and chemical engineering interplay

Most known adsorbents preferentially adsorb methane over nitrogen due to larger polarizability of methane.

“Most known adsorbents preferentially adsorb methane over nitrogen due to the larger polarizability of the former (see Table 2).298,451,452”

Titanosilicate materials ETS-4, CTS-1, Ba-ETS-4, and Sr-ETS-4 have been demonstrated to be excellent adsorbents for nitrogen removal from natural gas at small scale.

“Titanosilicate materials developed by Engelhard Corporation (now BASF), such as ETS-4, CTS-1, Ba-ETS-4, and Sr-ETS-4, have been demonstrated to be excellent adsorbents for this application at a small scale.448,451,457−459”

H2O, CO2, and other minor components, such as H2S, need to be removed to prevent corrosion and plugging problems in processing and transportation operations.

“Furthermore, H2O, CO2, and other minor components, such as H2S, need to be removed to prevent corrosion and plugging problems in the processing and transportation operations.451,469,480”

Adsorption (PSA) and membrane technologies have potential to be much less energy intensive and to reduce operation costs significantly for CO2 separation from methane.

“Adsorption (more specifically PSA, pressure swing adsorption) and membrane technologies have the potential to be much less energy intensive and to reduce the operation costs significantly.449−451,463,483,484”

Separation of CO2 from mixtures with methane, nitrogen, water, hydrogen, etc., is a very active research topic.

“Its separation from mixtures with methane, nitrogen, water, hydrogen, etc., is a very active research topic.5,58,451,461”

Components with no calorific value, such as CO2, H2O, and N2, have to be kept below specific levels to allow use of methane-containing mixtures as fuel.

“Components with no calorific value, such as CO2, H2O, and N2, have to be kept below specific levels in order to allow for the use of the mixture as a fuel.”

PSA processes for CO2 separation from methane have been studied on zeolites, MOFs, carbon molecular sieves, activated carbons, porous polymers, and amine-impregnated mesoporous silica.

“PSA processes for carbon dioxide separation from methane have been studied on a wide range of materials, such as zeolites, metal–organic frameworks (MOFs), carbon molecular sieves, activated carbons, porous polymers, or amine-impregnated mesoporous silica.449,451,463,485,486”

CO2 partial pressures at inlet of a CO2 removal unit are 0.4-35 bar, most frequently above 1 bar; thus, pressures from 1-10 bar are typical for feed.

“Note that CO2 partial pressures at the inlet of a CO2 removal unit are 0.4–35 bar,450,519 most frequently above 1 bar. Thus, pressures from 1–10 bar are typical for the feed.451,483,520”

In ETS-4 and related MolecularGate technology, efficiency of process is based on molecular sieving, with right pore size selected by controlled thermal treatment.

“In the case of ETS-4 and related MolecularGate technology,451,492 the efficiency of the process is based on molecular sieving. The right pore size of the adsorbent is selected by controlled thermal treatment.”