Can CO₂ and Steam React in the Absence of Electrolysis at High Temperatures?

Abstract

The fundamental question of whether CO2 can react with steam at high temperatures in the absence of electrolysis or high pressures is answered. These two gases are commonly co‐present as industrial wastes. Herein, a simple experiment by flowing CO2 and steam through a CaCl2 matrix at 500–1000 °C and atmospheric pressure was designed. Comprehensive characterizations and density functional theory calculations were conducted. Meanwhile, this study aims to recover HCl from CaCl2 via a low‐emission oxy‐pyrohydrolysis process. As confirmed, CO2 and steam interact strongly on the CaCl2 surface, leading to an explicit formation of CaCO3/CaO and a nearly complete release of HCl. This is mainly contributed to a halved energy required for the splitting of H2O, resulting from the formation of a bicarbonate‐like structure to replace Cl− out of CaCl2, an otherwise industrial waste, whilst an important dopant for carbon capture, utilization and storage, and medium for electrochemical synthesis.

Density functional theory analysis of the adsorption behaviors of H2O and CO2 on the CaCl2(110) surface

“…Zhou et al investigated the HCl generation rate from CaCl 2 by flowing steam on the CaCl 2 surface with and without CO 2 . 16 The release extent of the HCl under the interaction of CO 2 and steam was significantly facilitated by up to four times the value obtained without CO 2 . Kondo et al studied the recovery of chlorine gas from CaCl 2 by blowing oxygen into molten CaCl 2 at temperatures above 950 °C.…”

“…Zhou et al calculated the surface energy of four index surfaces and concluded that the (110) surface is the most stable CaCl 2 surface. 16…”

“…Zhou et al calculated the surface energy of four index surfaces and concluded that the (110) surface is the most stable CaCl 2 surface. 16 However, systematic computational research is still missing for the H 2 O and CO 2 molecules adsorbed on the CaCl 2 (110) surface. The reaction mechanisms of pyro-hydrolysis of CaCl 2 in the presence of CO 2 remain unclear.…”

“…2 as a chemical eqn(2). Zhou et al investigated the HCl generation rate from CaCl 2 by flowing steam on the CaCl 2 surface with and without CO 2 16. The release extent of the HCl under the interaction of CO 2 and steam was significantly facilitated by up to four times the value obtained without CO 2 .…”