Modification of Active Carbon and Expanded Graphite on SrCl2 for Ammonia Adsorption in Solid Selective Catalytic Reduction

Solid selective catalytic reduction (SCR) is a promising nitrogen oxides abatement technology with advantages over urea-SCR, such as higher ammonia storage density, no low-temperature crystallization, and no exhaust temperature limitation. However, conventional metal chloride adsorbents for solid SCR (SSCR) suffer from two critical issues: ammonia adsorption decay after repeated cycles and poor thermal conductivity, which restrict their practical application. To address these problems, this study aimed to prepare strontium chloride (SrCl 2 )/active carbon and SrCl 2 /expanded graphite (EG) for SSCR systems and systematically investigate their ammonia adsorption characteristics and key influencing factors. The principal findings are as follows: the optimal mass ratio of SrCl 2 to active carbon/EG was 5:1/6:1, respectively, with the optimal expansion ratio of EG being approximately 148 times, which ensures high initial ammonia adsorption capacity and no adsorption decay during multiple adsorption-desorption cycles. A comparative analysis further showed that the SrCl 2 /EG adsorber exhibited higher ammonia bulk density, higher ammonia mass density, and better thermal conductivity than SrCl 2 /active carbon. In conclusion, SrCl 2 /EG is the optimal composite adsorber for SSCR systems, as its excellent thermal conductivity can enhance the material's heating rate and thereby shorten the ammonia start-up time. Graphical It presents cyclic ammonia adsorption capacity changes of SrCl 2 /EG composite adsorbents with different mass ratios. The SrCl 2 :EG = 6:1 ratio exhibits optimal performance—no adsorption decay, initial capacity of 0.803 gNH 3 /g, and significantly outperforming pure SrCl 2 ;, confirming it as an efficient, stable ammonia storage material for SSCR systems.