The present work evaluates and optimizes CO 2 absorption in a bubble column for the Pz-H 2 O−CO 2 system. We analyzed the impact of the different operating conditions on the hydrodynamic and mass-transfer performance. For the optimization of the process, variable conditions were used in the multivariate statistical method of response surface methodology. The central composite design is used to characterize the operating condition to fit the models by the least-squares method. The experimental data were fitted to quadratic equations using multiple regressions and analyzed using analysis of variance (ANOVA). An approved experiment was carried out to analyze the correctness of the optimization method, and a maximum CO 2 removal efficiency of 97.9%, an absorption rate of 3.12 g/min, an N CO 2 of 0.0164 mol/m 2 •s, and a CO 2 loading of 0.258 mol/mol were obtained under the optimized conditions. Our results suggest that Pz concentration, solution flow rate, CO 2 flow rate, and speed of stirrer were obtained to be 0.162 M, 0.502 l/h, 2.199 l/min, and 68.89 rpm, respectively, based on the optimal conditions. The p-value for all dependent variables was less than 0.05, and that points that all three models were remarkable. In addition, the experiment values acquired for the CO 2 capture were found to agree satisfactorily with the model values (R 2 = 0.944−0.999).

In recent years biodiesel fuel has been considered as an alternative fuel for diesel engines. This fuel is made by transesterification of vegetable oils (or animal fat) and alcohols in the presence of a catalyst. Density and viscosity are two important properties that are useful for selecting fuels. In this study the effects of temperature and volume fraction of biodiesel and diesel on the density and kinematic viscosity of blends were investigated. In the previous studies, some correlations have been presented for the prediction of these two properties, but the constants of these correlations differ depending on the type of biodiesel and diesel. In this study two general correlations were presented for estimating density and kinematic viscosity of the blends at several temperatures. These correlations depend on the temperature, volume fraction of biodiesel and diesel, and properties of pure biodiesel and diesel (pure density at 293.15 K and pure kinematic viscosity at 313.15 K). The predicted results showed high accuracy nevertheless to the generality of their constants.

Energy-efficient solvents with favorable thermodynamic properties that offer significantly low regeneration energy to the state-of-the-art CO2 capture technologies are typically limited by slow reactivity with CO2. To compensate for low absorption rates, herein, we report that the nonporous hypercross-linked polymeric (HCP) networks as rate promoters are capable of drastically accelerating CO2 absorption in N-methyldiethanolamine (MDEA) sorbents. It is a new topic toward the application of HCPs. Two HCPs were synthesized from cost-effective monomers: polystyrene (HCP-S) and benzene (HCP-B), and then the novel slurry solvents were prepared by suspending HCP-S and HCP-B in MDEA solutions. Benefiting from the inherent properties, HCP-S and HCP-B increased the overall rates of CO2 absorption in the MDEA solution by 253 and 130%, respectively, compared to the blank MDEA. The effect of temperature and amine concentration on the promoting performance of HCP-B was investigated. HCP-B promotes CO2 sorption in the whole temperature range from 25 to 80 °C, and at 2 to 4 molar concentrations of MDEA. The promoting effect of HCP-B was also observed in the DEA solvent, demonstrating that it is not unique to MDEA. Moreover, 13C NMR analysis was used to confirm the promoting effect of the network on CO2 sorption, and a possible mechanism was investigated.

Deep eutectic solvents (DESs) are the new generation of green promising CO 2 -capturing solvents, owing to their desirable properties, good stability, and environmentalfriendly features. In this study, a novel hybrid solvent has been developed based on DESs for CO 2 separation from a simulated flue gas flow. DESs: chlorine chloride (ChCl)-monoethanolamine (MEA), glyceline [1 ChCl/2 glycerol (Gly)], and piperazineactivated glyceline (glyceline/Pz) were added to the diethanolamine (DEA) solution in the concentration range of 10−30 wt %. The CO 2 absorption performances of the DES−DEA hybrid solvents were studied from the solubility and mass transfer points of view. Hydrodynamic studies revealed that the addition of DES results in a smaller bubble Sauter mean diameter. Moreover, partial replacement of water with ChCl-MEA or glyceline/Pz increased the CO 2 capture capacity, effective time, empirical enhancement factor, and overall mass transfer coefficient. On the contrary, with increasing glyceline concentration, the enhancement factor and overall mass transfer coefficient decreased under the studied operating conditions, although the CO 2 solubility did not change. Moreover, 13 C NMR analysis was used to characterize carbon-based species in DES−DEA systems before and after CO 2 absorption. Finally, the results of TGA measurements demonstrate that the addition of Gly-based DESs makes more stable hybrid solvents, which could be regenerated.