Development of urea modified CuO pellets for elemental mercury adsorption from natural gas with H2S

Efficiently removing elemental mercury (Hg 0 ) from natural gas is a serious task to both equipment safety and ecosystem. The granulation of adsorbent powder is required to reduce pressure loss and adsorbent elutriation from a fixed-bed demercuration system. Herein, urea modified CuO (Urea/CuO) pellets were developed for Hg 0 adsorption from natural gas with H 2 S. The characterization results show that the addition of urea accelerated the formation of pore structure and surface oxygen, thus enhancing the Hg 0 adsorption performance of CuO pellets. The Urea/CuO pellets with 20 % urea additive amount exhibited 93 % Hg 0 removal efficiency under the existence of 500 ppm H 2 S and a gaseous hourly space velocity of 1.21 × 10 5  h −1 . H 2 S was essential to in-situ convert Urea/CuO pellets into a highly active Hg 0 adsorbent. With the increase of H 2 S concentration from 0 to 1000 ppm, the Hg 0 removal efficiency was raised from 34 % to 93 %. Urea/CuO pellets performed well for Hg 0 adsorption at 10–50 °C, which was the representative temperature window of natural gas processing. The Hg 0 adsorption capacity and uptake rate of Urea/CuO with 500 ppm H 2 S reached as high as 27.06 mg·g −1 and 2.44 μg·g −1 ·min −1 , which largely exceeded those of commercial activated carbons specialized for Hg 0 adsorption as well as typical granulated Hg 0 adsorbents reported in previous literature. The existence of H 2 S in natural gas in-situ converted CuO into CuS. The S 2 2− on the formed CuS could act as active sites for Hg 0 adsorption, in which gaseous Hg 0 was captured as stable mercury sulfide (HgS). The deactivated adsorbent could be regenerated and reused by thermally decomposing HgS and replenishing the consumed surface oxygen and the sintering surface. With these advantages, the developed Urea/CuO pellets appears to be a promising Hg 0 adsorbent from natural gas with H 2 S.