Pentaethylenehexamine-Loaded Hierarchically Porous Silica for CO2 Adsorption

Abstract

Recently, amine-functionalized materials as a prospective chemical sorbent for post combustion CO2 capture have gained great interest. However, the amine grafting for the traditional MCM-41, SBA-15, pore-expanded MCM-41 or SBA-15 supports can cause the pore volume and specific surface area of sorbents to decrease, significantly affecting the CO2 adsorption-desorption dynamics. To overcome this issue, hierarchical porous silica with interparticle macropores and long-range ordering mesopores was prepared and impregnated with pentaethylenehexamine. The pore structure and amino functional group content of the modified silicas were analyzed by scanning electron microscope, transmission electron microscope, N2 adsorption, X-ray powder diffraction, and Fourier transform infrared spectra. Moreover, the effects of the pore structure as well as the amount of PEHA loading of the samples on the CO2 adsorption capacity were investigated in a fixed-bed adsorption system. The CO2 adsorption capacity reached 4.5 mmol CO2/(g of adsorbent) for HPS−PEHA-70 at 75 °C. Further, the adsorption capacity for HPS-PEHA-70 was steady after a total of 15 adsorption-desorption cycles.

Development of Silica-Based Monoliths for the Capture of CO2

“…Two other absorption bands, 2818 cm -1 and 2934 cm -1 , were also identified which refer to the symmetrical and asymmetric stretches of CH 2 , respectively. The presence of these bands suggests that the amine PEHA was introduced into the material and have also been reported by 42,55,56 . It is visible from the figures that Ti/M1-P has more pronounced bands referring to the amine group, thus indicating that this sample has higher amine content than the other samples.…”

“…It is also possible to observe for all samples the appearance of bands, namely: the band around 1360 cm -1 that is associated with vibration δ(C-N) 42 , the band of 1474 cm -1 that can be attributed to symmetrical flexion of amines (-NH 2 ) 55 , and the band of 1550 cm -1 , which refers to the δ(N-H) of -NH- 42 . The presence of these peaks was also described by Liu et al 42 , who synthesized the material MCM-41 impregnated with PEHA and Ji et al 55 , which have developed a porous silica material supported with PEHA. This is an indication that the material was successfully functionalized.…”

“…8, there is a diminution of the band near the 960 cm -1 region, a fact that can be justified due to the interaction between the surface Si-OH groups and the molecules PEHA. Ji et al 55 also obtained a decrease in the intensity of the absorption band designated for vibrations of the Si-OH group on the porous silica material supported with PEHA.…”

In Situ IR Study on Effect of Alkyl Chain Length between Amines on Its Stability against Acidic Gases

“…This was an effect of the increased diffusion of CO 2 molecules into the adsorption sites and amine stretching, which enhanced the catalytic adsorption activity. Organic amine stretching occurs at a high temperature, which can cause an increase in the number of exposed adsorption catalytic sites [26]. However, at 130 and 150 • C, only small differences were observed for both of the adsorbents.…”

“…Catalysts 2019, 9, x FOR PEER REVIEW 4 of 14 adsorption catalytic sites [26]. However, at 130 and 150 °C, only small differences were observed for both of the adsorbents.…”