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Phosgenation reactions are accompanied by the formation of the byproduct hydrogen chloride , as well as the production of carbon dioxide. Byproduct recovery and valorization may have implications for resource recovery and elimination of pollutive practices. However, phosgene-related byproducts with respect to resource utilization, environmental performance, and techno-economic issues are yet to be investigated using a proactive and integrated approach. This study aims to systematically investigate the comprehensive utilization of phosgenation reaction byproducts. Different detailed utilization routines are proposed. The hydrogen chloride processing methods were evaluated and compared in terms of equipment investment, operation cost, waste discharge, and profit. The results show that, based on the processing of 1 t of hydrogen chloride, polyvinyl chloride , and epichlorohydrin have the best economic benefits, which are CNY 1418.73 and CNY 1463.22, respectively. However, they are wastewater-intensive. The operation cost of preparing hydrochloric acid and the amount of wastewater (CNY 305.72 and 0.028 t, respectively) are both less than that of alkali neutralization (CNY 3903.92 and 3.718 t, respectively). This study establishes an industrial chain scheme for phosgene-related byproducts that meet the requirements of a circular economy to achieve environmental sustainability . Introduction Phosgene is an important organic intermediate, and phosgenation products have many types. Phosgene and its products are crucial in many fields, such as engineering plastics, and synthetic material auxiliaries (Gad, 2014). Since China, the world's most important producer and consumer of phosgenation products (Yan, 2022), started producing phosgene and phosgenation products, their production scale has significantly increased. Given its high toxicity and the potential danger of phosgenation production, phosgene has gradually become a special development resource. Phosgene and phosgenation products can lead to high-quality and high-end development. Optimizing the industrial development structure, increasing the proportion of high-end products, and comprehensively utilizing byproduct resources are the main paths of high-end development and the development trend of the phosgenation sector. All phosgenation reactions produce hydrogen chloride as a byproduct, and some reactions can also produce carbon dioxide as another byproduct (Brenner and Photaki, 1956; Yang et al., 2021). With the large-scale expansion of toluene diisocyanate and 4,4′-diphenylmethane diisocyanate and industrial development, the total amount of byproduct hydrogen chloride continuously grow (Liu et al., 2021). With the development of polyurethane, chlor-alkali, pesticides, and many other industries, removal and utilization of many byproducts of hydrogen chloride has become a problem. If hydrogen chloride can be comprehensively utilized, they can improve economic benefits, fundamentally eliminate environmental pollution caused by the byproduct hydrogen chloride, and promote healthy development, optimization, and upgrade of phosgene products (Bechtel et al., 2018). The most traditional processing methods for hydrogen chloride are divided into two categories. One is the preparation of hydrochloric acid through the absorption of water and recycling or selling it cheaply. Its utilization is greatly limited because of the presence of organic impurities. The industrial preparation of hydrochloric acid involves electrolysis. Electrolysis of saturated brine produces hydrogen and chlorine at the cathode and anode, respectively. In the reactor, hydrogen and chlorine are passed to the quartz burner for ignition and combustion to generate hydrogen chloride, emitting a large amount of heat. After cooling, hydrogen chloride was absorbed by water, resulting in hydrochloric acid, which is widely used in organic synthesis, analytical chemistry, food, and medicine. The presence of organic impurities limits their application in various fields. For example, the chlor-alkali industry is an important source of the byproduct hydrochloric acid, which contains many toxic impurities, such as organic chlorine. Toxic substances cannot be used in food or medicine. In analytical chemistry, the presence of organic impurities significantly affects the precision and accuracy of the analysis. The other is directly drained after neutralization with alkali, affecting the economic benefits and causing severe environmental pollution (Zhuang et al., 2020). The two main methods for the comprehensive utilization of byproduct hydrogen chloride are (1) recycling of hydrogen chloride, which mainly converts hydrogen chloride into chlorine, and (2) producing downstream products and developing upstream and downstream industrial chains (Ma et al., 2016). Two main techniques to produce chlorine from hydrogen chloride are electrolysis and oxidation (Ding et al., 2013). Electrolysis is divided into dry and wet methods, including diaphragm electrolysis and oxygen cathodic electrolysis (Motupally et al., 1998), Oxidation methods are divided into direct oxidation and catalytic oxidation (Martinez et al., 2014). Both diaphragm (Zhao et al., 2015) and oxygen cathode (Mohammadi et al., 2009) electrolyses must absorb of HCl into hydrochloric acid before electrolysis and have cumbersome processes, high energy consumption, and large investments (Paidar et al., 2016; Singh et al., 2017). Research on the production of chlorine gas from hydrogen chloride is still ongoing. The electrolysis method has not yet been entirely developed wherein it still is energy intensive and high investment. Therefore, this concept has gained increasing attention. Wang et al. (2011) conducted electrolysis experiments on hydrochloric acid wastewater from chlorinated polyethylene production using the diaphragm electrolysis method. Hydrogen chloride was electrolyzed using a filter pressure electrolyzer, and the generated chlorine could directly enter the chemical synthesis process, providing a new idea for the resource utilization of waste hydrochloric acid (Wang et al., 2011). The Bayer–Uhdenora process is the most effective electrochemical process for producing chlorine from hydrogen chloride in the industry using hydrochloric acid as the raw material and oxygen cathode electrolysis technology. Bechtel et al. proposed a new technology based on the direct electrolysis of gaseous hydrogen chloride using oxygen cathode electrolysis, reducing the exergic requirement by 38% compared with the Bayer–Uhdenora process (Bechtel et al., 2021). Producing chlorine through dry electrolysis of hydrogen chloride was invented by DuPont in the mid-1990s (Motupally et al., 2002), and a pilot plant was established (Liu et al., 2012). The significant difference between dry hydrogen chloride electrolysis and wet electrolysis is that hydrogen chloride does not need to be absorbed into hydrochloric acid for electrolysis. The equipment investment has been reduced, and the diaphragm performance can be better maintained because there is no water in the anode system (Grotheer et al., 2006; Perez-Ramirez et al., 2011). The advantage of electrolysis is that it can produce high-purity chlorine; however, energy consumption affects the development of electrolysis. Compared to electrolysis, the advantage of the oxidation method (e.g., catalytic oxidation method) is its low energy consumption. The direct oxidation method (e.g., the Weldson method (PAT Report, 1975) and the Kel–Chlor method (Oblad, 1969)) uses inorganic oxidants to directly oxidize hydrogen chloride to chlorine gas. The development of a direct oxidation method is slow, and relevant research is still in the small-trial stage due to the limitations of high energy consumption and side reactions (Ding et al., 2013). Catalytic oxidation must occur in the presence of a catalyst wherein the most representative of which is the Deacon process (Kuwertz et al., 2013; Pan et al., 1994). Moreover, catalytic oxidation is the most industrialization-worthy process for chlorine production from hydrogen chloride. Related research focused on catalysts and reactors. Zhang et al. (2022) synthesized a Cu/aUiO-66-NH2 catalyst using an amorphous zirconium-based metal–organic framework (aUiO-66-NH2). Amrute et al. (2012) investigated the structure, properties, and mechanism of CeO2 in the oxidation of hydrogen chloride to chlorine, and the results showed that CeO2 has a significant activity and strong stability and is a powerful alternative to RuO2. Han et al. (2011) proposed a new two-zone circulating fluidized bed reactor suitable for the Deacon process. The hydrogen chloride conversion rate was greatly improved compared with that of the traditional fluidized bed reactor. Benson et al. (1997) developed a dual-interconnected fluidized bed reactor system for the Deacon process based on reaction kinetics and thermochemical research. Byproduct hydrogen chloride can also be used as a raw material for downstream products, such as polyvinyl chloride (PVC) (Tian et al., 2016; Wang et al., 2016) and epichlorohydrin (ECH) (Okhlopkova et al., 2019; Santacesaria et al., 2010). Byproduct recovery and valorization may have implications for resource recovery and elimination of pollutive practices. However, phosgene-related byproducts with respect to resource utilization, environmental performance, and techno-economic issues are not yet explored using a proactive and integrated approach. Previous research on the processing of phosgene-related byproducts are based on a specific product or processing method. This gap is addressed by systematically analyzing the comprehensive utilization of byproducts of phosgenation reactions. This study classifies the phosgenation reactions based on different byproducts and introduces the sources and processing methods of byproducts. Based on the perspectives of equipment, operating costs, and waste discharge, a techno-economic assessment was conducted on the processing methods of hydrogen chloride. Different industrial chain schemes that meet the requirements of a circular economy are proposed using the evaluation results. Fig. 1 shows the research framework of this study. Section snippets Classification and sources of phosgene-related byproducts The phosgenation reactions can be divided into two categories: (1) phosgenation reaction with only hydrogen chloride as a byproduct and (2) that with both hydrogen chloride and carbon dioxide as byproducts. Processing methods for byproducts of phosgenation reactions High-purity carbon dioxide can be separated when the byproducts of the phosgenation reactions are hydrogen chloride and carbon dioxide. The separated hydrogen chloride can be treated with the same processing scheme as that when the byproduct is only hydrogen chloride. This study introduces a processing method for hydrogen chloride and a scheme for separating hydrogen chloride and carbon dioxide to obtain high-purity carbon dioxide. Techno-economic assessment of processing methods for phosgenation byproducts The processing process, material balance, and main equipments are provided for the processing of the byproducts of phosgenation and analyzed in terms of equipment investment, operation cost, economic benefit, and discharge of the three wastes. The material balance, operating cost, economic benefit, and discharge data in the following analysis are based on the processing of 1 t of hydrogen chloride gas. Conclusions According to byproduct differences, the phosgenation reactions could be divided into only byproduct hydrogen chloride, byproduct hydrogen chloride, and carbon dioxide, and the byproduct sources were introduced. Various processing schemes for phosgene byproducts were investigated, with the corresponding processes provided. Moreover, techno-economic assessment for different processes are performed. The results show that, based on the processing of 1 t of hydrogen chloride, polyvinyl chloride, and CRediT authorship contribution statement Rongshan Bi: Conceptualization, Methodology, Writing – original draft. Haixing Yang: Formal analysis, Investigation, Data curation, Writing – original draft. Kejia Yan: Resources, Writing – review & editing. Zitong Hou: Visualization, Writing – review & editing. Haifeng Chen: Writing – review & editing. Xiaoping Jia: Conceptualization, Writing – review & editing, Funding acquisition. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was supported in part by the National Key R&D Program of China ( 2020YFE0201400 ) and Natural Science Foundation of Shandong Province ( ZR2020MB124 ). References (53) R. Zhuang et al. 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