Review of catalysis and plasma performance on dry reforming of CH 4 and possible synergistic effects Wei-Chieh Chung, Moo-Been Chang n Graduate Institute of Environmental Engineering, National Central University, No. 300, Zhongda Road, Zhongli District, Taoyuan City 32001, Taiwan article info Article history: Received 15 August 2015 Received in revised form 20 January 2016 Accepted 4 April 2016 Keywords: CCUS Dry reforming of methane Syngas Catalysis Plasma Synergistic effects abstract Global warming has received much public concern and carbon dioxide utilization has been considered as one of viable approaches to reduce the CO 2 emissions and alleviate global warming. Dry reforming of methane (DRM) is regarded as potential technique to reduce anthropogenic (greenhouse gases) GHGs emissions. Both catalysis and plasma technologies have been applied for DRM to investigate the CO 2 and CH 4 conversion as well as syngas generation efficiency. For catalysis, noble metal catalysts exhibit good activity but the cost is too high. Ni-based catalysts are usually investigated and several methods of modifying are postulated to enhance their DRM performance including better metal-support interaction, basicity of catalyst and smaller metal cluster size. However, catalysis needs to be operated at a high temperature which results in high energy consumption. Moreover, coke deposition leads to deactivation of catalyst which also limits the lifetime of catalyst. Plasma reforming which can be operated at a wide range of temperature (from room temperature to over 1000 °C) is another technique for DRM. Both non- thermal plasma and thermal plasma are proved to effectively convert CO 2 and CH 4 into syngas. However, the energy utilization efficiency is still low and relatively low syngas selectivity results in low syngas generation efficiency. Thus, combination of catalysis and plasma can be an alternative to integrate the advantages of catalysis and plasma. Plasma catalysis is proved to have synergistic effects to improve the syngas generation efficiency, since catalysis and plasma can improve the performance of each other. Plasma can enhance catalysis activity and durability, while the existence of catalyst promotes electron density in plasma and energy utilizing efficiency is expected to improve. In this study, the mechanisms of catalysis promotion are described, the synergistic effects between catalyst and plasma are elucidated, and possible approaches to optimize DRM are proposed. & 2016 Elsevier Ltd. All rights reserved. Contents 1. Introduction ......................................................................................................... 14 2. Catalysis reforming ................................................................................................... 15 2.1. Carbon deposition .............................................................................................. 15 2.2. Mechanisms and enhancements of catalysis performance .............................................................. 16 3. Plasma reforming .................................................................................................... 18 3.1. Hydrocarbons as by-products ..................................................................................... 20 3.2. Features among various plasma reactors ............................................................................ 20 4. Combination of catalysis and plasma ..................................................................................... 22 4.1. Pretreatment of catalyst via non-thermal plasma ..................................................................... 23 Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews http://dx.doi.org/10.1016/j.rser.2016.04.007 1364-0321/& 2016 Elsevier Ltd. All rights reserved. Abbreviations: GHGs, greenhouse gases; CCUS, carbon capture, utilization and storage; SRM, steam reforming of methane; F–T process, Fischer–Tropsch process; POM, partial oxidation of methane; DRM, dry reforming of methane; ATR, auto-thermal reforming of methane; DBD, dielectric barrier discharge; APGD, atmospheric-pressure glow discharge; APPJ, atmospheric-pressure plasma jet; RF, radio frequency discharge; PPC, post-plasma catalysis; IPC, in-plasma catalysis; E-R, Eley-Rideal; L–H, Langmuir– Hinshelwood; RWGS, reverse water gas shift; TPD, temperature programmed desorption; XPS, x-ray photoelectron spectroscopy; SPS, smaller particle size; SMSI, stronger metal-support interaction; MABS, more active basic sites; HOA, higher oxygen affinity; SEI, specific energy input; EE, energy efficiency; DAP, direct current arc plasma; SMC, smaller metal clusters; RAS, reduction of active sites; OV, oxygen vacancy; PSV, pore structure variation; EPOC, electrochemical promotion of catalysis n Corresponding author. Tel.: þ886 3 422715134663; fax: þ886 3 4226774. E-mail address: mbchang@ncuen.ncu.edu.tw (M.-B. Chang). Renewable and Sustainable Energy Reviews 62 (2016) 13–31