Development of carbon-based adsorbent for separation of impurities such as siloxane and ammonia from land-fill gas

Land-fill gas or bio-gas is composed of large portion of methane and carbon dioxide, and small amount of impurities such as nitrogen, oxygen, hydrogen sulfide, siloxane and ammonia. These gases can be used as a gas-fuel after upgrading treatment. For the application of the land-fill gas and bio-gas as a fuel, we developed highly-performing carbon-based adsorbent which can separate siloxane and ammonia residue from these gases. It was quite necessary to consider the chemical properties of siloxane and ammonia for development of suitable adsorbent of each component. The siloxane can be polymerized in acidic or basic condition to form bulkier species which causes adsorbent deactivation and difficult regeneration. The ammonia gas is well known as basic molecules which have strong affinity to acidic species. In these reasons, we prepared neutral carbon materials by various methods for siloxane adsorption. In addition, we developed carbon-based basic ammonia-adsorbent by simple methods such as the chemical treatment of commercial activated carbon or the impregnation of organic molecules into the activated carbon. And then, adsorption-desorption isotherms and breakthrough curve of siloxane and ammonia were measured for thus synthesized adsorbents. Detail results for synthesis and the adsorption measurement of the studied adsorbents will be presented in the conference

Adsorptive removal of CO2 from CO2-CH4 mixture using cation-exchanged zeolites

Raw natural gas and landfill gas contains methane as its major component, but it also contains considerable amounts of contaminants such as CO2 and H2S (i.e. acid gases) that can cause corrosion and fouling of the pipeline and equipment during transportation and liquefaction. Amine-based CO2 gas removal processes have been employed in the gas industry, but these processes have disadvantages including high regeneration energy requirements and inefficiencies; these issues have not been adequately solved to date. Currently, adsorptive acid gas removal technologies have received significant interest because of the simplicity of adsorbent regeneration by thermal or pressure variation1). Numerous micro- and mesoporous adsorbents including zeolites [2-3], titanosilicates[4], activated carbons[5-6], metal-organic-framework (MOF) [7], and silica-alumina materials[8-9] were studied for this type of application. However, the CO2/CH4 selectivity of the aforementioned adsorbents was not high enough for commercial applications.In this study, different cation-exchanged zeolites were synthesized, physicochemically characterized, and evaluated for adsorptive removal of CO2 from CO2-CH4 mixtures. The adsorption isotherms of CO2 and CH4 in the pressure and temperature ranges 0 − 3MPa and 10 – 40 oC, respectively, for different cation-exchanged zeolites were measured and compared. The ideal-adsorbed solution theory (IAST) was employed for the estimation of CO2/CH4 selectivity for the different cation-exchanged zeolites. References 1) D. Aaron, C. Tsouris, Separ. Sci. Technol. 2005, 40, 321–348 2) J. Collins, US Patent No. 3,751,878. 1973. 3) M. W. Seery, US Patent No. 5,938,819. 1999 4) W. B. Dolan, M.J. Mitariten, US Patent No. 6,610,124 B1. 2003 5) A. Kapoor, R.T. Yang, Chem. Eng. Sci. 1989, 44, 1723–1733 6) A. Jayaraman, Chiao, A. S.; Padin, J.; Yang, R. T.; Munson, C. L., Separ. Sci. Technol. 2002 37, 2505–2528 7) L. Hamon, E. Jolimaitre, G. Pringruber , Ind. Eng. Chem. Res. 2010, 49, 7497-7503 8) W.B. Dolan, M.J. Mitariten, US patent No. 2003/0047071, 2003 9) G. Bellussi, P. Broccia, A. Carati, R. Millini, P. Pollesel, C. Rizzo, M. Tagliabue, Micropor. Mesopor. Mat., 2011, 146, 134–14

CO recovery from blast furnace gas by vacuum pressure swing adsorption process: Experimental and simulation approach

This paper presents experimental and numerical approaches to use a four-bed, six-step CO vacuum-pressure-swing adsorption (VPSA) process with CuCl/boehmite adsorbent to extract carbon monoxide (CO) gas from a simulated blast furnace gas (BFG; N2:CO:CO2 = 60:20:20 mol %) at setting temperature Tset = 60 °C and adsorption pressure 2.5 bar ≤ Pad ≤ 6.4 bar. The cyclic adsorption isotherms of pure CO2 and CO on CuCl/boehmite pellets were measured at temperature range, 20 °C ≤ Tset ≤ 60 °C in a bench-sale apparatus. At Tset = 60 °C, the CO-adsorption capacity was stable during cyclic operation, with negligible hysteresis between adsorption and desorption processes. A mathematical model of four-bed, six-step CO-VPSA was developed; this model successfully reproduced the experimental data. A sensitivity analysis of the effect of feed flowrate, rinse flowrate, and desorption pressure on CO purity and recovery was conducted to improve the efficiency of the CO enrichment. Simulations show that 79.9–87.4 mol % of CO recovery could be attained with >90 mol % purity of CO, and 71.8–81.8% CO recovery could be achieved with >99 mol % purity of CO at Tset = 60 °C and 2.5 bar ≤ Pad ≤ 6.4 bar. This method to recover CO from emissions by the steel-making industry can detoxify them, and the CO can be used in syntheses of value-added chemical products.11Nsciescopu

Bed configurations in CO vacuum pressure swing adsorption process for basic oxygen furnace gas utilization: Experiment, simulation, and techno-economic analysis

CO is a primary component of basic oxygen furnace gas (BOFG) and can be used for producing fuel and various value-added chemicals. It can be typically obtained from steel mill gases via separation. Herein, suitable bed operation configurations for vacuum pressure swing adsorption (VPSA) were determined based on the desired CO product purity (PURCO,P) when separating CO from simulated BOFG (CO:CO2:N2:CH4 = 65:20:10:5 mol%) using a numerical model validated with experimental data. By changing the operation steps, one case of two-bed, four-step (2-bed), one case of three-bed, five-step (3-bed), and two cases of four-bed, six-step (4-bedbase and 4-bedmod) operation configurations were considered at a setting temperature of 60 ℃, desorption pressure of 0.13 kgf cm−2, and adsorption pressure in the range of 2.5–4.0 kgf cm−2. The sensitivities of these four operation configurations were evaluated to compare the separation performance and economic benefits of each operation configuration. In the 2-bed case, the PURCO,P demonstrates a separation limit (92.1–92.7 mol%). When targeting PURCO,P ≥ 99.00 mol%, the 3-bed case presents the most favorable CO recovery values (RECCO,P; 92.97–94.13 %) and unit production costs of CO (UPCCO; 0.252–0.357 US$Nm−3), whereas the 4-bedmod case presents optimal RECCO,P (82.06–91.65$ Nm−3) when targeting PURCO,P ≥ 99.99 mol%, under the same operating conditions. These results indicate cost-effective CO-VPSA process configurations for enriching CO from BOFG, based on the target PURCO,P.11Nsciescopu

Hybrid Postsynthetic Functionalization of Tetraethylenepentamine onto MIL-101(Cr) for Separation of CO₂ from CH₄

To remove CO₂ from CH₄, tetraethylenepentamine was grafted onto coordinatively unsaturated centers of MIL-101­(Cr) by postsynthetic functionalization: wet impregnation at 298 K, followed by grafting, drying, and washing. Compared to MIL-101­(Cr), TEPA–MIL-101­(Cr) showed 54% higher CO₂ adsorption at 1 bar and 98% reduction of CH₄ adsorption at 60 bar. The ideal adsorption solution theory (IAST) selectivity of CO₂/CH₄ for a binary gas mixture of 2% CO₂ + 98% CH₄ at 298 K and 60 bar predicted by the Toth equation was found to be 11 and 598 for ungrafted and grafted MIL-101­(Cr), respectively. Single column breakthrough tests were performed for upgrading the 2% CO₂ + 98% CH₄ mixture to liquefied quality of natural gas (CO₂ < 50 ppm) under various operating conditions including different temperatures and total amount of purge gas at the fixed pressure of 60 bar and temperature of 298 K. At the feed flow rate of 1000 sccm, the TEPA–MIL-101­(Cr) extrudates obtained 0.89 mmol/g CO₂ adsorption capacity and nearly 83% of adsorbed CO₂ can be removed by regenerating extrudates at 393 K with 79 cm³/g_adsorbent of total amount of purge gas