Mimic Enzyme Based Cellulose Nanocrystals/PVA Nanocomposite Membranes for Enrichment of Biogas as a Natural Gas Substitute

Abstract

Nanocomposite membranes promoted by mimic enzyme was developed and optimized for biogas upgrading at moderately high pressure applications up to 15 bar. Zn based mimic enzyme (Zn-cyclen) was synthesized. Different concentrations of selected mimic enzyme were added in nanocomposite membranes containing 1% crystalline nanocellulose (CNC) and 2% polyvinyl alcohol (PVA). The addition of mimic enzyme improved separation performance. The optimal results were obtained with 5 µmol/g addition of mimic enzyme at 10 pH. Furthermore, the addition of mimic enzyme showed abrupt change in moisture uptake ability and the maximum values were found for addition of 0.005wt% of mimic enzyme loading. Permeation testing showed that presence of moisture content plays important role in the activation of mimic enzyme. Furthermore, at high pH values mimic enzyme showed improved CO2 hydration rates. SEM results exhibited smooth morphology and no significant different in membrane thickness with increase in the mimic enzyme concentration. Moreover, the decline in membrane performance was observed with increasing pressure up to 15 bar. CNC/PVA based membranes with optimal loading of mimic enzyme showed significantly high separation than pure PVA membrane; a permeance of 0.34 [m3(STP)/m2 bar hr] and selectivity of 42.