CO₂ Conversion over Supported Ni Nanoparticles

Abstract

To accelerate the reduction of global greenhouse gas emissions represents an urgent response to the climate change and to its devastating effects on human society and planet. The 2030 Agenda for sustainable development written during the last global meeting on climate change (COP 21) requires that greenhouse gas emissions begin to decline within the next two decades, holding the increase in the global average temperature below 2 °C above preindustrial levels. Apart water vapor, the major greenhouse gases present in our atmosphere are CO2 and CH4. Consequently, there is much interest in the scientific world towards new and more efficient methods to use carbon dioxide and methane. Therefore, the password for the humanity future is Decarbonation. The main source of CH4 is from natural gas and its main uses are in the combustion processes, power generation and chemical production from syngas. Syngas represents an important intermediate for ultra-clean liquid fuel production and it is a valid raw chemical as alternative source to petroleum. There are numerous processes for syngas production, such as partial oxidation, steam reforming, auto-thermal reforming, dry reforming and oxy-reforming. Among these, dry reforming (e.g. reforming of methane with CO2), is currently attracting great interest since it utilizes, with respect to the other processes, carbon containing feedstocks. Recently, the CO2 methanation has become of interest as renewable energy storage system based on a Power-to-Gas conversion. The conversion of electricity into methane takes place into two steps: hydrogen is produced by electrolysis and converted into methane by CO2 methanation. Active, selective and stable catalyst is the core of the above-mentioned processes (dry-reforming and CO2 methanation) to produce green fuels. For these reasons, in the last decades several researchers have deeply studied the critical issues in the catalysts preparation for dry reforming and CO2-methanation reactions. Transition metals (Ni, Pd, Pt, Co, Ru, Rh, etc.) are active species in both catalytic processes. Among these metals, Ni, Ru and Rh are the most effective. Ni has been the most studied because it presents a peculiarity that makes it interesting from a commercial point of view: it is the cheapest. To preserve and improve metal activity, technology focused on the development of metal-supported catalysts. Alumina, silica, zeolites, zirconia, ceria and carbon nanotubes are supports largely investigated. In this work we summarize the fundamental properties of supported Ni nanoparticles that make it the most suitable catalyst for conversion of CO2 in the sustainable energy production.