The present invention addresses to the use of NaY zeolite with a Si/Al ratio>2.6 as a solid adsorbent in the process of removing H.sub.2S from natural gas through a PSA process. The described adsorbent has the capacity of removing H.sub.2S from natural gas from offshore exploration platforms, enabling in situ regeneration. The experimental development proved the high capacity of capturing H.sub.2S by the NaY zeolite in consecutive cycles of pressurization, adsorption, depressurization and purging. This capture capacity remains at 74.2% of the initial capacity, remaining stable in subsequent cycles. The structure of the material maintained crystallinity above 95% in use, in 15 consecutive cycles, allowing the reuse of the adsorbent for a prolonged period of operation, preventing the solid from being constantly changed, which is quite common in a non-regenerative process.

A method for upgrading biogas comprising methane and nitrogen, where the biogas is provided in at least one pressurized vessel at a pressure of at least 65 atm (6586 kPa). The method includes a pressure swing adsorption (PSA) cycle having a feed phase, where biogas is fed into a first adsorbent bed when the inlet end is open and the outlet end is closed, followed by a first depressurization phase, where a gas enriched in methane is withdrawn through the outlet end with the inlet end being closed. This gas enriched in methane can be pipeline quality and at pipeline pressures. A methane recovery phase is provided, which can improve methane recovery, wherein gas is withdrawn and the pressure drops to one or more lower values, and where this gas can be recycled for use in the feed phase, used in a regeneration phase, and/or fed to a second bed.