Research Paper Thermodynamic research of adsorbent materials on energy efﬁciency of vacuum-pressure swing adsorption cycle for CO 2 capture Ruikai Zhao a , Shuai Deng a,⇑ , Shengping Wang b , Li Zhao a , Yue Zhang a , Bowen Liu a , Hailong Li c , Zhixin Yu d a Key Laboratory of Efﬁcient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin 300350, China b Key Laboratory for Green Chemical Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China c School of Business, Society and Engineering, Mälardalen University, SE-72123 Västerås, Sweden d Department of Petroleum Engineering, University of Stavanger, 4036 Stavanger, Norway highlights  Adsorbent effects on the energy- efﬁciency performance of VPSA are investigated.  Mg-MOF-74, zeolite 13X, zeolite 5A, activated carbon and silica gel are compared.  For the 5 adsorbent materials, the highest second-law efﬁciency is silica gel.  Proportionality factor of working capacity is a key parameter for cycle design.  The development of new adsorbents for Type III would be extremely urgent for VPSA. graphical abstract 2.0 2.5 3.0 3.5 4.0 4.5 5.0 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Zeolite 5A Zeolite 13X Mg-MOF-74 Activated carbon Silica gel Second-law efficiency (%) Energy consumption (MJ/kg CO2 ) Vacuum-pressure swing adsorption cycle article info Article history: Received 18 July 2017 Revised 30 August 2017 Accepted 15 September 2017 Available online 18 September 2017 Keywords: VPSA Second-law efﬁciency Adsorbent materials Carbon capture abstract This paper presents a comprehensive thermodynamic research on energy efﬁciency of vacuum-pressure swing adsorption (VPSA). The study examined the inﬂuence from four types of typical adsorbent materials on the energy efﬁciency of VPSA by cycle parameters. The selected adsorbent materials are acti- vated carbons, zeolite 5A, zeolite 13X, silica gels, and metal-organic frameworks (MOFs). The study also analyzes the effects of separation temperature, adsorption pressure, desorption pressure, CO 2 concentra- tion and percent of unused bed on the energy-efﬁciency of VPSA cycle. The examined performance parameters are CO 2 working capacity, proportionality factor, energy consumption and second-law efﬁciency. The results show that the energy consumption is approximately 2.0–4.5 MJ/kg and the second-law efﬁciencies are 4–7% for VPSA cycles using the ﬁve adsorbent materials. The effect of adsor- bent materials on the energy efﬁciency mainly depends on the proportionality factor of CO 2 working capacity (b) of VPSA cycle, which is important to screen materials at the ﬁxed cyclic boundary conditions and preliminary calculation of second-law efﬁciency for VPSA cycles. For existing adsorbent materials which are Type I commonly, the lower values of b would lead to the higher second-law efﬁciencies. The development of new adsorbents of Type III would be extremely urgent in near future. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction In the recent years, signiﬁcant efforts have been invested in the ﬁeld of materials and processes to capture CO 2 from anthropogenic http://dx.doi.org/10.1016/j.applthermaleng.2017.09.074 1359-4311/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: sdeng@tju.edu.cn (S. Deng). Applied Thermal Engineering 128 (2018) 818–829 Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng