Microwave Synthesis of MCM-41 and Its Application in CO₂ Absorption by Nanofluids

Abstract

Microwave synthesis method is a green chemical process with mild reaction conditions, fast reaction, and low energy consumption. In this work, an order mesoporous silica material MCM-41 was synthesized by microwave technology. Functionalized MCM-41 was prepared by wet impregnation with polyethyleneimine (PEI). XRD, SEM, TEM, DLS, N2 adsorption-desorption, FTIR, and TG were used to characterize the physicochemical properties of samples. Furthermore, CO2 absorption performance in water in the presence of uncalcined MCM-41 and PEI-MCM-41 nanoparticles was evaluated. In addition, the mechanisms of enhanced absorption were also elaborated. The experimental results indicated that the optimum conditions for preparation of MCM-41 were the microwave time of 15 min, microwave temperature of 100°C, and microwave power of 200 W. Under this condition, MCM-41 with narrow particle size distribution, average diameter of 50 nm, and SBET of 1210.3 m2g-1 was obtained. The enhancement effect of PEI-MCM-41 nanoparticles was more obvious than that of uncalcined MCM-41. PEI-MCM-41 as a promoter not only increased the CO2 diffusion rate but also enhanced the adsorption capacity due to the fact that it owns more active sites that may react with CO2. The CO2 absorption improvement of PEI-MCM-41 (0.1 wt%)/H2O was 25.35% higher than that of water.

Accelerating MCM-41 One-Pot Synthesis Through Microwave Irradiation

“…Table 2 presents a bibliographic survey of studies synthesizing MCM-41 silicas by microwaves and performing surfactant removal using different methods. The shorter synthesis + removal time reported by Cheng et al [11] , is equivalent to 315 minutes (15 min of MW synthesis + 5 h of calcination in the mu e). There are still no reports that carry out the synthesis and extraction of the surfactant in one step, therefore, the results obtained from the tests carried out suggest that the one-pot synthesis presents an effective methodology, as it reveals good agreement with the results found in the literature.…”

“…Most surfactant molecules (93%) were removed in a 15 min sonication at 40°C. Cheng et al [11] synthesized MCM-41 silicas by microwave irradiation, varying different conditions, such as time, power, and temperature. However, the surfactant removal process was carried out through calcination.…”

“…There is a clear advantage when using microwave irradiation to obtain MCM-41, where the total time required for synthesis is considerably less for a wide range of conditions. Compared to conventional methods, in which a minimum of 10 h is required to synthesize ordered silica from the MCM family [1,11] . In addition, microwave irradiation provides a more homogeneous temperature distribution in the reaction system, resulting in greater uniformity in the formation of pores in MCM-41.…”

“…As reported, many researchers already report the synthesis of MCM-41 as well as the removal of the surfactant by microwaves [7,11] , however, there are still no studies that carry out these two steps via onepot. To further accelerate the silica formation process, in this work, in addition to the synthesis of MCM-41 by MW, the CTAB surfactant was removed by MW in a single step (one-pot).…”

One-Pot Synthesis and Surfactant Removal from MCM-41 Using Microwave Irradiation

“…Most surfactant molecules (93%) were removed in a 15 min sonication at 40 °C. Cheng et al [ 11 ] synthesized MCM-41 silicas using microwave irradiation, varying different conditions such as time, power, and temperature. The authors reported that microwaves can promote the dissolution and recrystallization of the precursor and accelerate the crystallization rate, in addition to obtaining better results than synthesis carried out using conventional heating.…”