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High dispersion of active metal is always approved for better catalytic performance in CO 2 hydrogenation to methanol. Herein, a strategy was proposed to encapsulate copper nanoparticles in supercages of zeolite 13X, and hence the growth of copper nanoparticles can be controlled. In the present work, catalysts were prepared using ion-exchange and hydrogen reduction at a tiny positive pressure. The results show that as-synthesized catalyst consists of metallic copper and FAU-type zeolite. Excessive amount of copper will destroy zeolite frameworks, and the amount of 5.9 at% is appropriate for considerable BET surface area and ideal copper dispersion. Meanwhile, copper nanoparticles may grow outside from zeolite at high reduction temperatures (≥220 °C), resulting in serious surface area decline and metallic copper agglomeration. Afterwards catalytic tests reveal good stability of the optimal CX-220 catalyst in continuous reactions. The CX-220 achieves remarkably high methanol selectivity of ≥ 95% within wide ranges of reaction temperatures and reaction pressures. Further analyses reveal that the encapsulation of copper nanoparticles reduces micropores and enriches mesopores in zeolite. The apparent activation energy for methanol synthesis over CX-220 catalyst has been lowered to a very low level because of the unique microstructure, and thus the methanol synthesis reaction is dominant in CO 2 hydrogenation for dramatic methanol selectivity. Therefore, this work gives important insights and applicable routes for catalysts analyses of CO 2 hydrogenation to methanol. [Display omitted] • Cu nanoparticles are successfully encapsulated in zeolite 13X with the proposed method. • Proper Cu content and reduction temperature are crucial for favorable microstructures. • Prepared samples achieve remarkably high methanol selectivity at studied reaction conditions. [ABSTRACT FROM AUTHOR]

Revealing the life-cycle CO 2 emissions of steel products is of great significance for mitigating CO 2 emissions. However, previous studies did not conduct comparative analysis for steel products produced by different technological pathways, resulting in considerable confusion in the setting of carbon reduction pathways. By using the material flow analysis method, this study revealed the life-cycle CO 2 emissions associated with various technological pathways. The results shows that life-cycle CO 2 emissions per metric ton of steel are: 3620.78 kg for shaft furnace (SF)-electric furnace (EF) routes, 2598.54 kg for blast furnace (BF)- basic oxygen furnace (BOF), 1868.16 kg for Scrap & Molten Iron-EF and 1330.22 kg for scrap-EF. The energy structure (e.g. coal blending mode, power generation mode) material structure (e.g. iron ore matching mode, matching mode of scrap and molten iron), and transportation mode have a significant impact on CO 2 emissions. Undoubtedly, low-carbon or zero-carbon electricity is more effective in reducing CO 2 emissions. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract As one of the energy-intensive and high-polluted industries, steel industry is facing great challenges of energy-saving and emission reduction. In this study, a bottom-up approach is used to build the inventory of air pollutants in China's steel industry. We analyzed the temporal and spatial characteristics of the atmospheric emission inventory of China's steel industry. The results show that: (1) In 2015, the total amount of SO 2 , NOx, PM, PM 2.5 , PM 10 and PCDD/Fs emissions from Chinese steel industry were 1697.58kt, 1017.24kt, 4028.01kt, 849.02kt, 1330.53kt and 1216.83g I-TEQ, respectively. SO 2 , NOx, PM, PM 10 and PCDD/Fs emissions mainly came from the sintering process, and PM 2.5 came from the converter process. (2) NOx emissions show an "upward" trend, while SO 2 emissions depict a "slowdown" trend. PM, PM 2.5 , PM 10 and PCDD/Fs emissions present inverse U-shape trends. (3) The air pollutant inventory of Chinese steel industry indicates obviously spatial characteristics. Taking SO 2 emissions in 2015 as an example, SO 2 emissions from steel industry in North China and East China reached 1006.63kt, accounting for 65.2% of the total emissions. Hebei, Jiangsu and Shandong provinces where locate intensive traditional steel enterprises with majority of steel products generated SO 2 emissions of approximately 404.04kt, 171.83kt and 156.28kt respectively, accounting for 23.80%, 10.12% and 9.20% total emissions of China's steel industry. (4) The simulation model of air pollutants (SO 2 , PM) was established taking adjusted production capacity and layout of steel industry into consideration, the simulation suggests that SO 2 and PM emissions are projected to decrease by 1Mt, 2 Mt, respectively. [ABSTRACT FROM AUTHOR]

Steel industry is an important mainstay industry and key greenhouse gas emitter of China. Employing life cycle assessment method of cradle-to-gate and establishing material flow model for steel production processes, this paper analyzed carbon footprints of steel enterprises to reduce carbon emission efficiently. Taking the function of forest to capture carbon into account, carbon footprint was expressed as the forest area instead of carbon dioxide equivalent (CO 2 e). Taking five typical steel enterprises (J, A, T, N, B) in China as examples, the carbon footprint per ton of steel in each process was calculated and its influence factors were analyzed. Results show that (1) from the perspective of process, the carbon footprint of iron-making, in which a large amount of coke and coal is consumed, is the largest, followed by the process of coking and sintering; (2) analyzing the type of gas, CO 2 contributes over 70% of the total carbon footprint in the whole production process; (3) the average carbon footprint per ton of steel was 0.325 hm 2 /t. Among five companies, carbon footprints of company N were up to 0.342 hm 2 /t, while company B had the lowest carbon footprint, at only 0.291 hm2/t. The gaps of carbon footprint are mainly due to geographical differences, energy consumption construction and product equipment and technology. The carbon footprint of enterprises was compared with the local carbon capacity, and analysis results show that the steel output and local forest areas could be significant factors determining whether the carbon emissions discharged by steel mills exceed the local carbon capacity and cause environment problems. According to analysis results, corresponding opinions and policies were proposed. [ABSTRACT FROM AUTHOR]