PSU New NG Absorbent (Seedling)
Developing A New Natural Gas Super-Absorbent Polymer (NG-SAP) for A Practical NG Storage System with Low Pressure, Ambient Temperature, and High Energy Density
Recipient Penn State (PI: Mike Chung)
Abstract This project investigates a new natural gas storage method based on absorption mechanism using a newly developed hydrocarbon super-absorbent polymer (SAP) called "Petrogel". This material is composed of two immicible polyolefin polymers with an interpenertrated network (IPN) structure that spontaneously form large free volume between two polymer chains, and the intertwined rigid and soft segments allow the formation of microchannels in the polymer matrix for fast diffusion. Petrogel has shown absorption of liquid hydrocarbons with a very high absorption capacity (40 times of polymer weight) and fast kinetics. In a preliminary test using ethylene gas (C2), we observed the same Petrogel absorption phenomenon under supercritical C2 condition. It may be possible that the supercritical natural gas (mainly C1) can also be absorbed in Petrogel IPN structure with the swollen matrix for accommodating a large quantity of NG molecules. Thus, the project objective is to develop the most suitable Petrogel NG-SAP for onboard NG storage, which shall simultaneously exhibit three essential properties, including: (a) good NG affinity with a binding energy in the range of 15-25 KJ/mole, so that methane gas can be reversibly immobilized (or condensed to supercritical fluid) in the polymer matrix under 15 kJ/mol, volumetric density >263 cm3/cm3 (>180 g/L), energy density >10 MJ/L under 100 bar pressure at ambient temperature, they are higher than the CNG level under 250 bar. If successful (1st go-decision), we will broaden the absorbent to Petrogel (B) IPN structures with p-electron conjugated (rigid) side groups (Figure 1). The research goal for budget period 2 is to further increase NG storage energy density >15 MJ/L, volumetric density 390 cm3/cm3 (>270 g/L) under 500 cm3/cm3 (>360 g/L), and energy density >20 MJ/L under <65 bar pressure at ambient temperature. If successful, this new NG storage technology shall achieve the DOE goal for using NG fuel in heavy- and medium-duty vehicle fleets and beyond. We should significantly close the technical gap for the practical usage of NG fuel in general transportation vehicles. It would also ease several close-related concerns relative to storage cost, energy density, safety, greenhouse gas, etc.