Upgrading production from the aging natural gas wells by non-cryogenic separation of nitrogen from methane continues to be a topic of intense research. New nano-structured sorbent materials have been developed in the recent past for the purpose of separation of nitrogen/methane mixtures by pressure swing adsorption (PSA). Ackley and Yang have demonstrated the use of carbon molecular sieve (CMS) for this purpose but have also shown that the potential for CMS to achieve the pipeline quality is doubtful [1]. Habgood developed a process using 4A molecular sieves for the same separation, but this process was limited to low temperatures (273 K) and high methane content [2]. Although separation can often be improved through process optimization, maximum performance is limited by the adsorption characteristics of the sorbent. More promising separation of N2/CH4 mixtures was achieved by PSA using calcium-exchanged clinoptilolite, which is a naturally occurring zeolite [3]. The Molecular Gate Technology is the most promising process available commercially at present for N2/CH4 separation and it uses Sr-ETS-4 calcined at 315 oC [4].
Clinoptilolites have a two-dimensional channel structure with multiple indigenous cations located in these channels that can be systematically altered to get desired adsorption characteristics by performing ion exchange [5]. One of the objectives of this work is to prepare mixed ion-exchanged clinoptilolites (i.e., partially exchanged clinoptilolites) and test their effectiveness for CH4 enrichment by means of adsorption measurements. In this study various ion-exchanged forms of clinoptilolites are prepared and the low-pressure adsorption kinetics of nitrogen and methane in them is studied using Micromeritics’ ASAP 2010 (constant volume apparatus).
Upgrading production from the aging natural gas wells by non-cryogenic separation of nitrogen from methane continues to be a topic of intense research. New nano-structured sorbent materials have been developed in the recent past for the purpose of separation of nitrogen/methane mixtures by pressure swing adsorption (PSA). Ackley and Yang have demonstrated the use of carbon molecular sieve (CMS) for this purpose but have also shown that the potential for CMS to achieve the pipeline quality is doubtful [1]. Habgood developed a process using 4A molecular sieves for the same separation, but this process was limited to low temperatures (273 K) and high methane content [2]. Although separation can often be improved through process optimization, maximum performance is limited by the adsorption characteristics of the sorbent. More promising separation of N2/CH4 mixtures was achieved by PSA using calcium-exchanged clinoptilolite, which is a naturally occurring zeolite [3]. The Molecular Gate Technology is the most promising process available commercially at present for N2/CH4 separation and it uses Sr-ETS-4 calcined at 315 oC [4].
Clinoptilolites have a two-dimensional channel structure with multiple indigenous cations located in these channels that can be systematically altered to get desired adsorption characteristics by performing ion exchange [5]. One of the objectives of this work is to prepare mixed ion-exchanged clinoptilolites (i.e., partially exchanged clinoptilolites) and test their effectiveness for CH4 enrichment by means of adsorption measurements. In this study various ion-exchanged forms of clinoptilolites are prepared and the low-pressure adsorption kinetics of nitrogen and methane in them is studied using Micromeritics’ ASAP 2010 (constant volume apparatus).