Low Temperature High Pressure Adsorption of Nitrogen by RPM3-Zn Using a Differential Pressure Adsorption Unit

Open Access
Belnick, Andrew D
Area of Honors:
Chemical Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Angela Lueking, Thesis Supervisor
  • Michael John Janik, Honors Advisor
  • adsorption
  • MOFs
  • separation
  • RPM3-Zn
Adsorption as a method of separating air is highly preferable over other processes like cryogenic distillation due to the lower cost of utilities and more moderate temperature and pressure conditions. Metal organic framework materials are a promising way to accomplish this separation of nitrogen and oxygen. One of which is RPM3-Zn, a material synthesized and tested by collaborators at Rutgers University. This material warrants further research, as preliminary data has shown it to be selective to oxygen over nitrogen at low temperature. Because the molar ratio of oxygen to nitrogen is nearly 1:4, a company needs only a quarter of the material and process utilities for an oxygen selective MOF over a nitrogen selective MOF. Experiments were conducted using this material and nitrogen gas at 195K and 20 bar/65 bar. They were completed on a custom differential pressure adsorption unit built by Dr. Angela Lueking at Penn State University. Helium was used as the blank non-adsorbing gas differential pressure correction. The sample cells were maintained at 195K using a bath of acetone and dry ice. All experiments were run for 16 hours. Extreme fluctuations in dP with time were observed and thought to be a function of changes in the temperature in the room as well as changes in the height of the temperature bath. Consequently, only the first 2 hours of data were used in determining the moles of nitrogen adsorbed. Similar fluctuations in dP with time were observed in the helium blank experiments. In the 20 bar experiments 0.540 and 0.854 mmol N2/g RPM3-Zn were observed and in the 65 bar experiments 1.222 and 0.711 mmol N2/g were observed. This is close to the value of 1.8 mmol/g found on the IGA for 195K/ 20 bar, with the deviation likely due to problems in controlling temperature and possible contamination of the sample.