Cd/SBA-15 heterogeneous catalyst used for acetic acid conversion: pseudo-homogeneous kinetic model, response surface methodology, and historical data design

Abstract

Mesoporous materials (MMs) in the Santa Barbara Amorphous (SBA) family can be used as catalysts or support materials (SMs) for catalysts because they have controllable pore structure, thermal and chemical stability, and their surface properties can be modified easily depending on the desired reaction type. Surfactant (Pluronic p123; it is a symmetric triblock copolymer comprising poly and its chemical formula; HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H), a silica source (such as Tetraethyl orthosilicate: TEOS; SiC8H20O4), and a solvent are used in the synthesis of the SBA family (SBA-15). The SBA-15 was given with the hydrothermal method (HM) a catalyst feature by loading the active substance at a rate of 10, 25 % (cadmium/silica) by mass. Esterification reactions (ERs) were carried out with Cd-SBA-15 (Cd/Si: 10–25 %) catalyst at a feed rate of 1/2 (methanol/acetic acid), in the presence of 0.4 g catalyst, at a reaction temperature of 373 K and for 6–48 h. After 48 h, the catalytic activity (CA) values were obtained as 65 and 68 %, respectively. The re-usability of the catalysts was repeated two times under the same experimental conditions. It was observed that the catalysts maintained their catalytic activity of 73.35 and 68.72 % (3 × 48 h). In addition, the limited effect of catalyst amount on acetic acid conversion was investigated by Response Surface Methodology, and Historical Data Design. Moreover, k 1, k2, equilibrium constant and activation energy values were calculated using the pseudo-homogeneous kinetic model. The physical features of the catalysts were investigated by BET, XRD, FTIR, DRIFT, SEM/EDX, and MAPPING analysis methods.

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“…Figure2shows the results of the low and high-angle XRD analysis of the SBA-15 and the hybrid samples consisting of different loadings of TiO 2 , Fe, and Cd on SBA-15. Similar results are shown in our previous work dealing with the activities of Cd/SBA-15 for the esterification of acetic acid with methanol[27,28]. According to the results of the XRD analysis of the SBA-15, four main Bragg peaks were obtained (Figure2a), corresponding to the d(100), d(110), d(200)[29,30], d(210)[31], and d(300)[32] characteristic peaks.…”

“…The FT-IR analysis of SBA-15 showed that the peaks between wavelengths of 445 cm −1 and 1046 cm −1 belonged to the characteristic structure of SBA-15 (Figure 3) [27,28]. Symmetrical and asymmetrical structures of tensile and flexible vibrations of Si-O and SiO 2 were observed at 938, 789, and 1044 cm −1 [37,38].…”

“…In this work, the TiO 2 /SBA-15 hybrid catalyst was synthesized using the hydrothermal method [25]. On the other hand, SBA-15, Cd/SBA-15, and Fe/SBA-15 were synthesized through the in situ incorporation method using the procedures described in the literature [26][27][28][29]. To obtain pure SBA-15, a solution of the surfactant Pluronic P123 (Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol))(144 mL, 1.7 M-Sigma Aldrich) in water was obtained and amounts of water and Pluronic P123 were adjusted as described earlier [29].…”