Carbon monoxide (CO) is a key material in C1 chemistry for chemical production and CO2 reduction, whereas in applications, such as H2 for fuel cells, its concentration must be kept below 0.2 ppm. Adsorption technology is useful for both CO removal and production to provide environmental sustainability for the energy and chemical industries. In this review, the CO adsorption performances of various adsorbents, such as activated carbons, zeolites, metal–organic frameworks, activated alumina, mesoporous silicas, and their modified adsorbents, are collected, and their physical and chemical properties and CO selectivities are summarized. Cu+ impregnation is a powerful and widely used modification method to enhance the CO adsorption of adsorbents. Therefore, the preparation methods and their effects on CO adsorption are also compared and reviewed. The data and analysis in this review can provide insights for the development of novel adsorbents and processes for CO removal and production. 

Overview of Carbon Monoxide Adsorption Performance of Pristine and Modified Adsorbents

Hydrothermal carbonization (HTC) is a prominent thermochemical technology that can convert high-moisture waste into a valuable product (called hydrochar) at a relatively mild treatment condition (180–260 °C and 2–10 MPa). With rapidly growing research on HTC and hydrochar in recent years, review articles addressing the current and future direction of this research are scarce. Hence, this article aims to review various emerging applications of hydrochars, e.g., from solid fuel to soil amendment, from electron storage to hydrogen storage, from dye adsorption, toxin adsorption, heavy metal adsorption to nutrient recovery, and from carbon capture to carbon sequestration, etc. This article further provides an insight in the hydrochar’s working mechanism for various applications and how the applications can be improved through chemical modification of the hydrochar. Finally, new perspectives with appropriate recommendations have been made to further unveil potential applications and its improvement through hydrochar and its modified version.

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Recent Progress on Emerging Applications of Hydrochar

Cuprous ion-based zeolites have been proven as promising carbon monoxide (CO) adsorbents by virtue of their excellent adsorption and regeneration properties due to π complexation. However, existing preparation methods still suffer from the problems of a cumbersome process and low loading amounts of cuprous ions. Herein, we proposed a one-step synthesis strategy of using ethanol as a solvent to provide a reducing protective environment, which enabled the facile and controllable preparation of highly dispersed CuCl over 5A zeolites. Using CuCl as a copper source, to ensure the integrity of the 5A zeolite structure, CuCl species were directly loaded onto the 5A support in one step. Ethanol solution could effectively protect Cu(I) from being oxidized by oxygen in air and improve the stability of cuprous ions in Cu(I)/5A adsorbents. The results demonstrated that the Cu(I)/5A prepared by this method exhibited a superior CO adsorption performance to the pristine 5A zeolite. The adsorption capacity of CO over Cu(I)/5A attained 3.44 mmol·g–1 at 298 K and atmospheric pressure, which was evidently superior to those of CuY (2.7 mmol·g–1) and CuSAPO34 (1.84 mmol·g–1) reported in the literature, while the adsorption capacity of H2 was only 0.069 mmol·g–1 under the same condition. According to the ideal solution adsorption theoretical model, CO was preferentially adsorbed and the IAST selectivity of CO in the CO/H2 binary mixture over Cu(I)/5A was about 273.4. This study provides a novel and effective way to synthesize high-efficiency CO adsorbents. 

Facile Preparation of Cu(I)/5A via One-Step Impregnation with Highly Dispersed CuCl in Ethanol Single Solvent toward Selective Adsorption of CO from H2 Stream

Preparation of K-N co-doped commercial cylindrical carbon via the coal partial steam gasification for CO2 adsorption

In this study, mung bean-based nanoporous activated carbons with different pore properties were prepared by varying the mass ratio of activating agent (KOH) and activation temperature. The low-temperature nitrogen adsorption...

Suk-Hoon Hong

Papers

Adsorption equilibria and kinetics of CO2, CH4, CO, N2, and H2 on KOH-treated activated carbon pellets up to 1000 kPa