New CO 2 Sorbent Synthesized with Nanoporous TiO(OH) 2 and K 2 CO 3 Abdulwahab Tuwati, † Maohong Fan,* ,†,‡,§ Armistead G. Russell, § Jianji Wang, ∥ and Herbert F. M. Dacosta ⊥ † Department of Chemical and Petroleum Engineering, and ‡ School of Energy Resources, University of Wyoming, Laramie, Wyoming 72071, United States § School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States ∥ Henan Key Laboratory for Environmental Pollution Control, School of Chemistry and Environmental Science, Henan Normal University, Henan 453007, People’s Republic of China ⊥ Chem-Innovations, Post Office Box 3665, Peoria, Illinois 61612, United States ABSTRACT: The objective of this study is to develop a new cost-effective CO 2 sorbent, K 2 CO 3 /TiO(OH) 2 or KTi, with inexpensive and widely available K 2 CO 3 and nanoporous TiO(OH) 2 as supporting material. The performance of KTi CO 2 capture was evaluated using a fixed-bed tubular reactor under different experimental conditions, including sorption temperature, flow rate, and moisture concentration of flue gas. Use of TiO(OH) 2 as a support for K 2 CO 3 leads to a significant increase of CO 2 sorption capacity per unit of K 2 CO 3 by about 37 times. The optimal K 2 CO 3 loading on TiO(OH) 2 is 30 wt %. The highest sorption capacity achieved with KTi is 1.69 mmol of CO 2 /g of KTi, whereas the theoretical sorption capacity of KTi with the prepared TiO(OH) 2 could be as high as 3.32 mmol of CO 2 /g of KTi. The enthalpy change of the KTi-based CO 2 sorption is −28.51 kcal/mol. Moreover, KTi is regenerable and stable. Therefore, KTi is a promising CO 2 sorbent. 1. INTRODUCTION Climate change is one of the most serious challenges people are currently facing. The amount of greenhouse gases emitted to the atmosphere has been substantially increased, and it will continue to increase in the foreseeable future. 1−4 One of the major greenhouse gases is carbon dioxide (CO 2 ) because of the use of fossil fuels (oil, natural gas, and coal), solid waste, trees and wood products, and also as a result of chemical manufacturing. The high demand for fossil fuel, which meets more than 98% of the world’s energy needs, is largely responsible for the increase in the CO 2 concentration levels in the atmosphere. The atmospheric CO 2 concentration has risen to ∼280−390 ppm, 5−7 about a 35% increase compared to the level at beginning of the industrial revolution. It is projected that the atmospheric CO 2 concentration will continue to increase unless effective CO 2 emission control measures are taken. Capturing CO 2 emitted from power station flue gas has been considered to be a potentially effective approach to control the atmospheric CO 2 level. People have studied different methods for capturing CO 2 in flue gas, such as cryogenic fractionation, solvent absorption, membrane separation, and chemisorp- tions. 8−11 Each method has its own advantages and disadvantages. For example, the cryogenic fractionation method can be used to produce pure liquid CO 2 , but its energy consumption is high because of the low concentration of CO 2 in flue gas. 12,13 Membrane separation has been considered a promising approach to CO 2 separation, and many progresses have been made in many aspects of the technology, including syntheses of new membrane materials. 14,15 The new membrane materials can be used for both pre-combustion and post- combustion CO 2 separations, which is very encouraging because membranes have been considered to be only applicable to pre-combustion CO 2 separation for a long period of time. 16 People are increasingly interested in the use of chemisorption for the separation of CO 2 from flue gas because the method has been widely considered to be able to reduce energy consumption needed for separation of CO 2 from flue gas. Chemisorption can be classi fied into absorption and adsorption. Absorption mainly uses aqueous amine compounds [e.g., monoethanolamine (MEA)] as CO 2 sorbents. MEA-based CO 2 capture technologies are mature and very successful in the removal of CO 2 in natural gas. However, the energy consumptions associated with the absorption method are relatively high because of the dilute CO 2 characteristics of flue gas and need a large amount of water in an aqueous MEA absorbent. To considerably decrease the energy consumptions of chemisorption-based CO 2 separation processes and, thus, make them economically viable for capture of CO 2 from the flue gas, scientists are increasingly increased in the development of inorganic and organic solid chemisorbents. 17,18 Significant progresses have been made in synthesizing new organic and inorganic solid CO 2 sorbents in recent years. 17−22 Organic solid sorbents are mainly based on amine compounds and new supporting materials. For example, Song’s group successfully developed a CO 2 sorbent called “molecular basket sorbent (MBS)” by impregnating a nanoporous mobil composition of matter number 41 (MCM-41) with polyethylenimine. The CO 2 sorption capacity of the MBS reaches 140 mg of CO 2 /g. 19 Received: July 17, 2013 Revised: October 29, 2013 Published: November 4, 2013 Article pubs.acs.org/EF © 2013 American Chemical Society 7628 dx.doi.org/10.1021/ef401368n | Energy Fuels 2013, 27, 7628−7636