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C19H25NO8, monoclinic, P21/n (no. 14), a = 10.149(2) Å, b = 12.338(3) Å, c = 15.898(3) Å, β = 97.58(3)°, V = 1973.2(7) Å3, Z = 4, Rgt(F) = 0.0581, wRref(F2) = 0.1842, T = 293(2) K.

Every late autumn, fluttering poplar leaves scatter throughout the campus and city streets. In this work, poplar leaves were used as the raw material, while H3PO4 and KOH were used as activators and urea was used as the nitrogen source to prepare biomass based-activated carbons (ACs) to capture CO2. The pore structures, functional groups and morphology, and desorption performance of the prepared ACs were characterized; the CO2 adsorption, regeneration, and kinetics were also evaluated. The results showed that H3PO4 and urea obviously promoted the development of pore structures and pyrrole nitrogen (N–5), while KOH and urea were more conductive to the formation of hydroxyl (–OH) and ether (C–O) functional groups. At optimal operating conditions, the CO2 adsorption capacity of H3PO4– and KOH–activated poplar leaves after urea treatment reached 4.07 and 3.85 mmol/g, respectively, at room temperature; both showed stable regenerative behaviour after ten adsorption–desorption cycles. [ABSTRACT FROM AUTHOR]

Organic amine-modified mesoporous carriers are considered potential CO2 sorbents, in which the CO2 adsorption performance was limited by the agglomeration and volatility of liquid amines. In this study, four additives of ether compounds were separately coimpregnated with polyethylene polyamine (PEPA) into MCM-41 to prepare the composite chemisorbents for CO2 adsorption. The textural pore properties, surface functional groups and elemental contents of N for MCM-41 before and after functionalization were characterized; the effects of the type and amount of additives, adsorption temperature and influent velocity on CO2 adsorption were investigated; the amine efficiency was calculated; and the adsorption kinetics and regeneration for the optimized sorbent were studied. For 40 wt.% PEPA-loaded MCM-41, the CO2 adsorption capacity and amine efficiency at 60 °C were 1.34 mmol/g and 0.18 mol CO2/mol N, when the influent velocity of the simulated flue gas was 30 mL/min, which reached 1.81 mmol/g and 0.23 mol CO2/mol N after coimpregnating 10 wt.% of 2-propoxyethanol (1E). The maximum adsorption capacity of 2.16 mmol/g appeared when the influent velocity of the simulated flue gas was 20 mL/min. In addition, the additive of 1E improved the regeneration and kinetics of PEPA-loaded MCM-41, and the CO2 adsorption process showed multiple adsorption routes. [ABSTRACT FROM AUTHOR]

C19H25NO8, monoclinic, P21/n (no. 14), a = 10.149(2) Å, b = 12.338(3) Å, c = 15.898(3) Å, β = 97.58(3)°, V = 1973.2(7) Å3, Z = 4, Rgt(F) = 0.0581, wRref(F2) = 0.1842, T = 293(2) K. [ABSTRACT FROM AUTHOR]

C19H25NO8, monoclinic, P21/n (no. 14), a = 10.149(2) Å, b = 12.338(3) Å, c = 15.898(3) Å, β = 97.58(3)°, V = 1973.2(7) Å3, Z = 4, Rgt(F) = 0.0581, wRref(F2) = 0.1842, T = 293(2) K. [ABSTRACT FROM AUTHOR]

To achieve the "double carbon" (carbon peak and carbon neutrality) target, low-cost CO 2 capture at large CO 2 emission points is of great importance, during which the development of low-cost CO 2 sorbents will play a key role. Here, we chose peanut shells (P) from crop waste as the raw material and KOH and K 2 CO 3 as activators to prepare porous carbons by a simple one-step activation method. Interestingly, the porous carbon showed a good adsorption capacity of 2.41 mmol/g for 15% CO 2 when the mass ratio of K 2 CO 3 to P and the activation time were only 0.5 and 0.5 h, respectively, and the adsorption capacity remained at 98.76% after 10 adsorption-desorption cycle regenerations. The characterization results suggested that the activated peanut shell-based porous carbons were mainly microporous and partly mesoporous, and hydroxyl (O-H), ether (C-O), and pyrrolic nitrogen (N-5) functional groups that promoted CO 2 adsorption were formed during activation. In conclusion, KOH- and K 2 CO 3 -activated P, especially K 2 CO 3 -activated P, showed good CO 2 adsorption and regeneration performance. In addition, not only the use of a small amount of the activator but also the raw material of crop waste reduces the sorbent preparation costs and CO 2 capture costs., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The accumulation and incineration of crop waste pollutes the environment and releases a large amount of CO 2 . In this study, corncob crop waste was directly activated using solid KOH in an inert atmosphere to prepare porous activated carbon (AC) to capture CO 2 , and to introduce N-containing functional groups that favour CO 2 adsorption, urea was mixed with corncob and KOH to prepare N-doped AC. The physical and chemical properties of the AC were characterized, and the effects of the mass ratio of KOH and urea to corncob, the activation temperature and time as well as regeneration were investigated to explore the optimal preparation process. The pores in the AC are mainly micropores, with the specific surface area and pore volume reaching 926.07 m 2 g -1 and 0.40 cm 3 g -1 for KOH-activated corncob and 1096.70 m 2 g -1 and 0.48 cm 3 g -1 after N-doping; the C-O plus O-H ratio and the -NH- ratio, which favour CO 2 adsorption in N-doped AC were 6.04 and 1.92%, respectively. The maximum adsorption capacities for KOH-activated corncob before and after N-doping were 3.49 and 4.58 mmol g -1 , respectively, at 20 °C and remained at 3.44 and 4.52 mmol g -1 after ten regenerations. The prepared corncob-based AC showed good application prospects for CO 2 capture., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

To reduce the cost of CO 2 capture, polyethylene polyamine (PEPA), with a high amino density and relatively low price, was loaded into MCM-41 to prepare solid sorbents for CO 2 capture from flue gases. In addition, methoxypolyethylene glycol (MPEG) was codispersed and coimpregnated with PEPA to prepare composite sorbents. The pore structures, surface functional groups, adsorption and regeneration properties for the sorbents were measured and characterized. When CO 2 concentration is 15%, for 30, 40 and 50 wt% PEPA-loaded MCM-41, the equilibrium adsorption capacities were respectively determined to be 1.15, 1.47 and 1.66 mmol g -1 at 60 °C; for 30 wt% PEPA and 20 wt% MPEG, 40 wt% PEPA and 10 wt% MPEG, and 50 wt% PEPA and 5 wt% MPEG codispersed MCM-41, the equilibrium adsorption capacities were respectively determined to be 1.97, 2.22 and 2.25 mmol g -1 at 60 °C; the breakthrough and equilibrium adsorption capacities for 50 wt% PEPA and 5 wt% MPEG codispersed MCM-41 respectively reached 2.01 and 2.39 mmol g -1 at 50 °C, all values showed a significant increase compared to PEPA-modified MCM-41. After 10 regenerations, the equilibrium adsorption capacity for codispersed MCM-41 was reduced by 5.0%, with the regeneration performance being better than that of PEPA-loaded MCM-41, which was reduced by 7.8%. The CO 2 -TPD results indicated that the mutual interactions between PEPA and MPEG might change basic sites in MCM-41, thereby facilitating active site exposure and CO 2 adsorption., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

To systematically study CO 2 adsorption performance, semicoke from the low-rank lignite was further activated and functionalized for CO 2 capture from flue gases. The effect of the activation conditions, such as the activation temperature, activation time and HCl washing, and the tetraethylenepentamine (TEPA)-functionalization on CO 2 adsorption were investigated; the pore structure and surface morphology of the semicoke under different activation conditions were characterized. Both the surface structure and adsorption performance of the activated semicoke could be improved under appropriate activation and acid-treatment conditions. The optimal breakthrough and equilibrium adsorption capacity for the TEPA-functionalized HCl-washed activated semicoke were separately 2.68 and 3.70 mmol g -1 at 60 °C for the simulated flue gas of 15 vol% CO 2 and 85 vol% N 2 . After ten adsorption-desorption cycles, the equilibrium adsorption capacity was still 3.43 mmol g -1 , and the semicoke-based sorbent showed good regenerability., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)