What technology uses a material called a molecular sieve to selectively adsorb nitrogen from the air?

The technology that employs a molecular sieve to selectively adsorb nitrogen from the air is known as pressure swing adsorption (PSA). In this process, air is passed through a bed of molecular sieves, which are materials that have tiny pores allowing them to preferentially adsorb nitrogen molecules due to their size and shape. This results in a higher concentration of oxygen being available in the output stream.

Pressure swing adsorption works by cycling the pressure within the sieve bed. During the first phase, air is introduced at high pressure, allowing nitrogen to be captured while oxygen flows through. When the sieve becomes saturated with nitrogen, the pressure is lowered, causing the nitrogen to desorb, which allows the system to prepare for the next cycle. This method efficiently separates nitrogen from oxygen without requiring extensive energy input or complex machinery.

The other technologies mentioned do not use molecular sieves in the same manner as PSA. Membrane separation relies on the different permeation rates of gases through a selective membrane rather than adsorption. Centrifugal compression is a method employed to compress gas rather than separate it by chemical means. Activated carbon filtration primarily targets specific impurities through adsorption processes but does not specifically separate nitrogen and oxygen from the air in the way molecular sieves do.