Grafted propyldiethanolamine for selective removal of SO 2 in the presence of CO 2 Ritesh Tailor, Abdelhamid Sayari ⇑ Department of Chemistry, Centre for Catalysis Research and Innovation (CCRI), University of Ottawa, Ottawa, Ontario K1N 6N5, Canada highlights  Grafted-diethanolamine adsorbs selectively, quantitatively and reversibly ppm SO 2 in CO 2 .  Material with 1.75 mmol/g amine adsorbs 2.84 at 23 °C in the presence of 1% SO 2 /N 2 .  The SO 2 adsorption capacity is unchanged in the presence of oxygen under dry condition.  The SO 2 uptake increased significantly in the presence of water vapor. article info Article history: Received 21 November 2015 Received in revised form 23 December 2015 Accepted 26 December 2015 Available online 31 December 2015 Keywords: Ethanolamine Pore-expanded MCM-41 Reversible SO 2 adsorption Selective SO 2 adsorption abstract Propyldiethanolamine-grafted pore-expanded mesoporous silica was developed for selective adsorption of SO 2 in the presence of CO 2 . With 1.75 mmol/g amine loading, the adsorption capacity in the presence of 1% SO 2 /N 2 under dry condition was found to be 2.84 and 2.14 mmol/g at 23 and 50 °C, corresponding to SO 2 /N ratios of 1.63 and 1.30, respectively. Not only the material did not capture any CO 2 under typical adsorption conditions, but the presence of CO 2 did not affect SO 2 uptake under dry or humid condition. Moreover, the SO 2 adsorption capacity remained unchanged in the presence of 10% O 2 /N 2 under dry con- dition. The presence of water vapor improved the SO 2 adsorption capacity of the material at room tem- perature by ca. 50% at 83% relative humidity. The SO 2 -saturated adsorbent under dry condition was regenerated completely by flowing N 2 at 130 °C, and the SO 2 working capacity remained unchanged in consecutive adsorption/regeneration cycles. Based on earlier FTIR and 15 N NMR data using similar grafted tertiary amine, it is suggested that the adsorption takes place by charge transfer complexation between SO 2 and the tertiary amine nitrogen. Nonetheless, consistent with literature data, it is speculated that SO 2 adsorption also occurs through zwitterion formation involving interaction between OH groups and SO 2 . Ó 2015 Elsevier B.V. All rights reserved. 1. Introduction Sulfur dioxide is a direct by-product of burning sulfur- containing fossil fuels and a chief component of acid rain and smog [1]. It has a detrimental effect on human health [2] as well as on plants and aquatic animals. As a result, it has been the subject of increasingly stringent regulations since the mid-1980s. SO 2 can be largely captured at the source by the use of sophisticated scrub- bers on smokestacks or by catalytic converters in cars. Commonly, for industrial gases such as power plants flue gas, SO 2 capture may be achieved using dry, wet or semidry flue gas desulfurization pro- cesses [3–6]. Another popular approach is to use scrubbing solu- tions [7], such as amine or ionic liquid solutions [8–14] or physical solvents [14–17]. Although, they have good efficiency, amine absorption processes suffer a number of shortcomings such as high energy consumption for regeneration, large production of wastewater, corrosion issues and excessive amine loss by evapora- tion [13,18,19]. Amine solutions are also prone to chemical deacti- vation in the presence of different gaseous contaminants such as O 2 and SO 2 by forming heat stable chemicals [10,20–22]. Alternatively, removal of SO 2 by solid adsorbents is becoming increasingly more popular because it offers multiple advantages over the above mentioned technologies. This includes simplicity of operation, low energy requirements for regeneration, low or no use of water, no volatility or corrosion issue, no by-products or waste generated, and the availability of a wide range of adsor- bents. This includes activated carbons [5,23–26], carbon fibers [27], zeolites [28–31], supported polymers [32] metal oxides and metal supported materials [33–35] and metal–organic frameworks (MOFs) [36,37]. http://dx.doi.org/10.1016/j.cej.2015.12.084 1385-8947/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: abdel.sayari@uottawa.ca (A. Sayari). Chemical Engineering Journal 289 (2016) 142–149 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej