Abstract:
Water removal from natural gas was carried out over modified and unmodified clinoptilolite. Four different techniques were used to modify origin clinoptilolite: thermal treatment, acid treatment, ion exchange, and combined acid treatment with ion exchange. The results showed that the surface area of clinoptilolite modified by the thermal treatment and ion exchange was rather constant while the porosity and hydrophobicity of the surface of clinoptilolite modified by the acid treatment and acid treatment prior to ion exchange was improved. The XRD and FTIR results suggested that the structures of all modified clinoptilolites were similar to natural clinoptilolite. Dealumination was found in the case of acid treatment and acid treatment prior to ion exchange. A decrease in the crystallinity of clinoptilolite was observed when the calcination temperature was above 300 C or the concentration of the acid was higher than 0.1 M. The results suggested that water adsorption capacity was a function of the Si/Al ratio. On the other hand, the improvement in the surface area hardly enhanced the water adsorption capacity In this work, the water adsorption capacity of clinoptilolite modified by the acid treatment and acid treatment prior to ion exchange increased from 0.0828 to 0.1019 and 0.0873 g adsorbed water/g clinoptilolite. In the simulated natural gas system, the results from the competitive adsorption between water and hydrocarbons the results from the competitive adsorption between water and hydrocarbons showed that the pentane adsorption of clinoptilolite modified by the acid treatment and acid treatment prior to ion exchange increased. The modified and unmodified clinoptilolites preferentially adsorbed water to hydrocarbons. The hydrocarbons were adsorbed on the clinoptilolite surface but they were desorbed later by the replacement of water molecules, which possess higher polarity.
