Sorption enhanced reforming requires in-situ removal of CO2 from reaction media at temperatures about 400-450 ºC. there is much literature on the subject that describes several materials that are potentially stable carbon dioxide scavengers at elevated temperatures, such as metal oxides, alkaline metal carbonates, zeolites and hydrotalcites . At MEL we have developed 2 different technologies for CO2 capture.
Our MELSORB range is based on modified lithium zirconates, The capture of carbon dioxide on lithium zirconate is based on a reversible solid-gas reaction that occurs in the temperature range 450-550 °C.
Li2ZrO3 + CO2 ↔ ZrO2 + Li2CO3
This ensures high selectivity of separation of CO2 from gaseous mixtures. Reversible reaction starts at temperatures above 650 °C. According to the reaction stoichiometry, lithium zirconate theoretically can uptake 28.75 % of CO2 by weight, and our products can achieve very close to this over numerous cycles.
Our unique patented process for the production of modified lithium zirconates also enables a lower temperature sorption of CO2 at 100-150°C of typically 7-10wt% due to physical sorption, this is then desorbed by heating above 300°C.
For further information please see our joint paper with Bath university and UOP "High temperature sequestration of CO2 using lithium zirconates " in Chemical Engineering Journal Volume 146, Issue 2, 1 February 2009, Pages 249-258.
Our our exhibition poster, or poster from the 5th international conference on environmental catalysis held in Belfast 21-28th august 2008, which MEL Chemicals sponsored.
At MEL we have developed a range of products based on the traditional Mg/Al hydrotalcites but where we had subsituted some of the metals with Zr, this gives rise to high surface area materials, but also potentially can increase the capacity for CO2.
Hydrotalcites typically have a much lower capacity than the lithium zircoantes for CO2 sorption but ~ 10times faster kinetics.
For further information please view a copy of poster on our current products.