Methanol Synthesis from CO₂ Hydrogenation

Abstract

In the future we will be phasing out the use of fossil fuels in favour of more sustainable forms of energy, especially solar derived forms such as hydroelectric, wind and photovoltaic. However, due to the variable nature of the latter sources which depend on time of day, and season of the year, we also need to have a way of storing such energy at peak production times for use in times of low production. One way to do this is to convert such energy into chemical energy, and the principal way considered at present is the production of hydrogen. Although this may be achieved directly in the future via photocatalytic water splitting, at present it is electrolytic production which dominates thinking. In turn, it may well be important to store this hydrogen in an energy dense liquid form such as methanol or ammonia. In this brief review it is emphasised that CO2 is the microscopic carbon source for current industrial methanol synthesis, operating through the surface formate intermediate, although when using CO in the feed, it is CO which is hydrogenated at the global scale. However, methanol can be produced from pure CO2 and hydrogen using conventional and novel types of catalysts. Examples of such processes, and of a demonstrator plant in construction, are given, which utilize CO2 (which would otherwise enter the atmosphere directly) and hydrogen which can be produced in a sustainable manner. This is a fast‐evolving area of science and new ideas and processes will be developed in the near future.

Recent Developments in the Modelling of Heterogeneous Catalysts for CO2 Conversion to Chemicals

“…Pd possesses the ability to activate hydrogen gas into H‐adatoms that can spillover unto metallic oxide supports and in the presence of CO (originated from dissociative adsorption of CO 2 ) form a formate ion which can be further hydrogenated to methanol or methane . The simplest example is Pd supported on ZnO and reduced with temperature >∼300 °C which results in the formation of the 1 : 1 PdZn alloy that shows very good selectivity to methanol . From the computational point of view this shows that DFT calculations are very necessary in studies of transition metals and bimetallic systems.…”

“…[42] The simplest example is Pd supported on ZnO and reduced with temperature >~300°C which results in the formation of the 1 : 1 PdZn alloy that shows very good selectivity to methanol. [148] From the computational point of view this shows that DFT calculations are very necessary in studies of transition metals and bimetallic systems.…”

Zinc Oxide Morphology‐Dependent Pd/ZnO Catalysis in Base‐Free CO2 Hydrogenation into Formic Acid

“…“Greenhouse effect” caused by the emission of CO 2 has led to climate changes and increasing temperatures globally within the past decades and thus a major imperative for the 21 st century will be to reduce the concentration of CO 2 in the atmosphere. A net‐zero‐carbon fuel economy may be realized if it efficiently utilizes CO 2 to produce carbon‐based fuels such as alcohols, hydrocarbons and formic acid (FA) [1–20] . Among these, FA is an attractive product that can be easily generated via CO 2 hydrogenation reaction, which exhibits wide applications in leather tanning, silage preservation and hydrogen storage [21–23] .…”

CO2 Hydrogenation to Methanol over La2O3-Promoted CuO/ZnO/Al2O3 Catalysts: A Kinetic and Mechanistic Study

“…A plethora of studies have been reported dealing with the reaction kinetics and mechanism over CZA-based materials, and several models have been proposed to explain the experimental results [6][7][8][9]. However, there is still debate regarding the reaction mechanism and catalyst requirements [4,10,11]. As far as catalysts are concerned, efforts have been made to improve the performance of CZA by either replacing/doping Cu with noble metals (e.g., Pt, Pd) [12][13][14][15] or by adding oxides in order to enhance the adsorption properties of the support and to increase the dispersion of the Cu phases [16][17][18][19][20][21].…”