Preliminary Assessment of Sorption Capacity on Solid CO2-Sorbents at Condition for Sorption-Enhanced Process

This work aims to investigate on developing sustainable biogas/bio-syngas upgrading systems to green H2 and food grade CO2, through sorption-enhanced reforming (SER) and sorption-enhanced water gas shift (SEWGS) technologies. These technologies combine the catalytic properties for reforming processes with those for CO2 absorption. The main objective of the research project involves the integration and optimization of SER and SEWGS technologies with existing biomass-fueled and industrially operating anaerobic digestion (biogas) and gasification (bio-syngas) plants. The pursued degree of innovation is twofold: (i) the process intensification to produce hydrogen (H2) in a more sustainable industrial practice, allowing the simultaneous CO2 capture and its separation in a high purity stream (ii) the use of biomass as a primary fuel instead of fossil fuels further increases the sustainability of H2 and reduces the CO2 footprint of the whole process. The global H2 market will increase from 70 million tons in 2019 to 120 million tons in 2024 [1], [2], as an indispensable raw material, which is widely used in the petroleum industry, for the synthesis of ammonia, to produce methanol, to produce hydrochloric acid or as a reducing agent in metallurgy [3], but also as a promising energy carrier, playing a key role among the sustainable fuels, due to its peculiar properties such as high calorific value, and non-polluting characteristics [4], [5]. The dominant technology to produce H2 is steam reforming of fossil natural gas [4], a highly energy-intensive industrial practice. Innovative solids with both CO2 sorbent and catalyst capacity for reforming and water gas shift reactions are to be exploited to obtain a real simplification of the unit operations of the traditional process. In this scenario, among the numerous solid sorbents in the state-of-the-art analysis, hydrotalcite like compounds (HTlcs) and metal-based oxides were considered as promising candidates for SEP processes [6]. Compared to the known adsorption data in the literature, which are in the range of 0.28-5.26 mmolCO2/g, one would like to improve the sorbent and catalytic capacity with the addition of suitable elements or salts (K2CO3, Mg, Al, Fe, Co, etc.) [7][8][9]. Different materials were synthetized in the laboratory, such as: (i) calcined commercial hydrotalcite, as reference material; (ii) commercial hydrotalcite impregnated with potassium carbonate; (iii) commercial hydrotalcite impregnated with potassium carbonate and iron; (iv) hydrotalcite based on magnesium and aluminum synthesized via the co-precipitation method and impregnated with potassium carbonate; (v) mixed oxides based on magnesium and aluminum synthesized via a mechanical mixing method and impregnated with potassium carbonate. All materials were characterized via XRD, BET-BJH, FTIR and SEM-EDS analysis. The ongoing activities will involve experimental trials to select the best material with the best performance. The lab scale apparatus is properly designed and built to operate in a wide range of operating parameters (temperature = 300-450°C and pressure = 10-25bar); the core of system is fixed bed reactor equipped with mass flow meters/controllers, a HPLC pump for liquid injection, online gases analyzer. The effect of steam will be also investigated. The whole test campaign, operating under a PSA (pressure swing adsorption) cycle, is addressed to the optimization of process condition at pilot scale and for the validation of modeling analysis of simulation tools. [1] F. Safari and I. Dincer, “A review and comparative evaluation of thermochemical water splitting cycles for hydrogen production,” Energy Convers. Manag., vol. 205, p. 112182, Feb. 2020, doi: 10.1016/J.ENCONMAN.2019.112182. [2] S. Atilhan, S. Park, M. M. El-Halwagi, M. Atilhan, M. Moore, and R. B. Nielsen, “Green hydrogen as an alternative fuel for the shipping industry,” Curr. Opin. Chem. Eng., vol. 31, p. 100668, Mar. 2021, doi: 10.1016/J.COCHE.2020.100668. [3] L. Barreto, A. Makihira, and K. Riahi, “The hydrogen economy in the 21st century: a sustainable development scenario,” Int. J. Hydrogen Energy, vol. 28, no. 3, pp. 267–284, Mar. 2003, doi: 10.1016/S0360-3199(02)00074-5. [4] S. Masoudi Soltani, A. Lahiri, H. Bahzad, P. Clough, M. Gorbounov, and Y. Yan, “Sorption-enhanced Steam Methane Reforming for Combined CO2 Capture and Hydrogen Production: A State-of-the-Art Review,” Carbon Capture Sci. Technol., vol. 1, no. September, p. 100003, 2021, doi: 10.1016/j.ccst.2021.100003. [5] M. Shokrollahi Yancheshmeh, H. R. Radfarnia, and M. C. Iliuta, “High temperature CO2 sorbents and their application for hydrogen production by sorption enhanced steam reforming process,” Chem. Eng. J., vol. 283, pp. 420–444, Jan. 2016, doi: 10.1016/J.CEJ.2015.06.060. [6] L. K. G. Bhatta, S. Subramanyam, M. D. Chengala, S. Olivera, and K. Venkatesh, “Progress in hydrotalcite like compounds and metal-based oxides for CO2 capture: A review,” J. Clean. Prod., vol. 103, pp. 171–196, 2015, doi: 10.1016/j.jclepro.2014.12.059. [7] A. Gil, E. Arrieta, M. A. Vicente, and S. A. Korili, “Synthesis and CO2 adsorption properties of hydrotalcite-like compounds prepared from aluminum saline slag wastes,” Chem. Eng. J., vol. 334, pp. 1341–1350, Feb. 2018, doi: 10.1016/J.CEJ.2017.11.100. [8] A. E. Rodrigues et al., “Study of the effect of the compensating anion on the CO2 sorption capacity of hydrotalcite based sorbents Olive mil wastewater valorization through steam reforming reaction using a hybrid sorption-enhanced membrane reactor for high-purity hydrogen product,” Sep. Purif. Technol., vol. 325, pp. 202–211, 2017, doi: 10.13140/RG.2.2.17530.95682. [9] J. Il Yang and J. N. Kim, “Hydrotalcites for adsorption of CO2 at high temperature,” Korean J. Chem. Eng., vol. 23, no. 1, pp. 77–80, 2006, doi: 10.1007/BF02705695.