Negative emissions technologies will play an important role in preventing 2 °C warming by 2100. The next decade is critical for technological innovation and deployment to meet mid-century carbon removal goals of 10−20 GtCO 2 /yr. Direct air capture (DAC) is positioned to play a critical role in carbon removal, yet remains under paced in deployment efforts, mainly because of high costs. This study outlines a roadmap for DAC cost reductions through the exploitation of low-temperature heat, recent U.S. policy drivers, and logical, regional end-use opportunities in the United States. Specifically, two scenarios are identified that allow for the production of compressed high-purity CO 2 for costs ≤$300/tCO 2 , net delivered with an opportunity to scale to 19 MtCO 2 /yr. These scenarios use thermal energy from geothermal and nuclear power plants to produce steam and transport the purified CO 2 via trucks to the nearest opportunity for direct use or subsurface permanent storage. Although some utilization pathways result in the re-emission of CO 2 and cannot be considered true carbon removal, they would provide economic incentive to deploying DAC plants at scale by mid-century. In addition, the federal tax credit 45Q was applied for qualifying facilities (i.e., producing ≥100 ktCO 2 /yr).
Liquid ammonia is a high-density (17.7 wt %) hydrogen carrier with a well-established production and distribution infrastructure. Efficient decomposition and purification are essential for its use as a hydrogen-storage material. Here we demonstrate the production of high-purity (>99.7%) H 2 from NH 3 using a catalytic membrane reactor (CMR) in which a Ru catalyst is impregnated within a porous yttria-stabilized zirconia (YSZ) tube coated with a thin, 6 μm Pd film by electroless deposition. The intimate proximity of catalyst and membrane eliminates transport resistances that limit performance in the conventional packed-bed membrane reactor (PBMR) configuration. The addition of a Cs promoter enabled complete NH 3 conversion at temperatures as low as 400 °C, exceeding equilibrium constraints without the need for a sweep gas. A reactor model was developed that captured CMR performance with high fidelity. NH 3 decomposition was observed to follow first-order kinetics due to efficient H 2 removal. Relative to a comparable PBMR, the Ru loading in the CMR was reduced an order of magnitude and the H 2 recovery increased 35%, enabling record volumetric productivity rates (>30 mol m −3 s −1 ) that validate its promise for efficient, compact H 2 delivery from ammonia.
The effect of surface area and polarity ratio of ZnO support on the catalytic properties of CuO/ZnO catalyst for methanol steam reforming (MSR) are studied. The surface area of ZnO was varied changing the calcination temperature, and its polarity ratio was modified using different Zn precursors, zinc acetate and zinc nitrate. It was found that the copper dispersion and copper surface area increase with the surface area of the ZnO support, and the polarity ratio of ZnO strongly influences the reducibility of copper species. A higher polarity ratio promotes the reducibility, which is attributed to a strong interaction between copper and the more polar ZnO support. Interestingly, it was observed that the selectivity of CuO/ZnO catalysts (lower CO yield) increases with the polarity ratio of ZnO carriers. As another key result, CuO/ZnOAc375 catalyst has proven to be more selective (up to 90%) than a reference CuO/ZnO/Al2O3 sample (G66-MR, Süd Chemie).The activity of the best performing catalyst, CuO/ZnOAc-375, was assessed in a Pd-composite membrane reactor and in a conventional packed-bed reactor. A hydrogen recovery of ca. 75% and a hydrogen permeate purity of more than 90% was obtained. The Pd-based membrane reactor allowed to improve the methanol conversion, by partially suppressing the methanol steam reforming backward reaction, besides upgrading the reformate hydrogen purity for use in HT-PEMFC.2
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.