You may already be familiar with various technologies that minimize the generation of carbon dioxide (CO2) emissions like hybrid-electric vehicles, biodegradable plastics, or even solar panels. But what happens when CO2 IS generated? Carbon capture and storage methods are used.
Researchers at Georgia Tech in the United States, in collaboration with colleagues at Osaka University in Japan, reported in the Journal of American Chemical Society a new approach for improving the efficiency of solid adsorbent materials that can be used to capture carbon dioxide directly from the air or from smokestacks.
They discovered it’s possible to improve adsorption efficiency by modifying the chemical structure of the adsorbent material, whereas previous research largely focused on varying the amount/ type of chemisorbent polymers used or changing the physical structure of the adsorbent material (i.e. porosity) to improve absorption efficiency. Carbon dioxide is chemically adsorbed onto the material’s surface as air passes through this honey-comb shaped adsorbent material.
There has been growing concerns over global climate change resulting from carbon dioxide emissions during fossil fuel combustion. This has led to significant research focusing on the development of materials and technologies that could be used to capture CO2 from the gas streams (called flue gases) of combustion sources like coal-fired power plants.
“Even if we removed CO2 from all the flue gas, we’d still only get a portion of the carbon dioxide emitted each year,” noted David Sholl, a professor in Georgia Tech’s School of Chemical & Biomolecular Engineering, in a recent press release. “If we want to make deep cuts in emissions, we’ll have to do more – and air capture is one option for doing that.”
The researchers believe capturing CO2 directly from the air is a complimentary technique that could be implemented with existing flue-gas CO2 capture technologies, to decrease global CO2 emissions from both mobile sources (think vehicles) and stationary sources (think power plants). The captured CO2 could then supply industrial applications, like fuel production from algae or enhanced oil recovery.
One of the biggest challenges for the team is to design a material that could capture CO2 that exists in dilute amounts. There is typically about 10% carbon dioxide in flue gases whereas the air we breathe contains about 400 ppm CO2.
So the team selected a combination of silica and amine-containing polymer which would have high adsorption capacities at low CO2 concentrations. The adsorbent material is a made of a honeycomb-shaped silica material that’s interdispersed with zirconium atoms, and is combined with poly(ethyleneimine) (PEI). The amine groups of the PEI polymer react with CO2 in a chemical reaction to form a product (carbamate or bicarbonate) that’s adsorbed on the surface of the material.
Researchers exposed the composite material to 10% or 400 ppm CO2/Ar flow at 100 mL/min and analyzed its adsorption capacity. The conventional absorbent materials (without zirconium additions) absorbed CO2 at 0.19 and 0.65 mmol/g under 400 ppm and 10% CO2 conditions. In comparison the adsorbent materials with zirconium additions showed 4.0 and 2.1 times higher efficiencies than the conventional adsorbent materials under the same conditions, respectively.
They concluded that the adsorbent materials containing zirconium atoms were very effective for capturing CO2. Further research lies in optimizing the process of CO2 capture to bring costs down even further according to the press release.
“Because the atmosphere is generally consistent, you could operate the capture equipment wherever you had a sequestration site,” said Christopher Jones, also a professor in the Georgia Tech School of Chemical & Biomolecular Engineering and a co-author of the paper, in the press release. “I don’t think air capture will ever produce carbon dioxide as cheaply as capturing it from flue gas. But on the other hand, it doesn’t seem to be wildly more expensive, either.”
Stephanie A. Didas, Ambarish R. Kulkarni, David S. Sholl, & and Christopher W. Jones (2012). Role of Amine Structure on Carbon Dioxide Adsorption
from Ultradilute Gas Streams such as Ambient Air ChemSusChem DOI: 10.1002/cssc.201200196
Yasutaka Kuwahara, Dun-Yen Kang, John R. Copeland, Nicholas A. Brunelli, Stephanie A. Didas, Praveen Bollini, Carsten Sievers, Takashi Kamegawa, Hiromi Yamashita, & Christopher W. Jone (2012). Dramatic Enhancement of CO2 Uptake by Poly(ethyleneimine) Using Zirconosilicate Supports J. Am. Chem. Soc DOI: 10.1021/ja303136e
Feature Image source: Press Release Georgia Tech 2012