3.1. Catalyst Characterization. The physical properties of the sulfonated naphthalene based catalyst and conventional Dowex 50-WX4-200 and Amberlite IR120 ion-exchange resins such as surface area, pore volume, and catalyst acidity are given in Table 1. The BET measurement indicates that the catalyst shows low specific surface area and pore volume compared with Dowex 50-WX4-200 and Amberlite IR120 hydrogen form. As shown in Table 1, the acidity of the catalyst analyzed by
neutralization titration was also lower than those of Dowex 50WX4-200 and Amberlite IR120 hydrogen form and the values of acidity agree closely with the acid site densities calculated in the form of sulfonic acid site (estimated by elemental analysis). The sulfonic group on carbon-based catalyst was confirmed by the Nicolet NEXUS 670 FTIR as shown in Figure 2. The IR spectrum shows strong absorption at 1600-1800 cm-1, which confirms the SdO stretching bands of the catalyst, and a broad band at 2600-3500 cm-1 confirms the presence of OH.10 Furthermore, the XRD of the catalyst shown in Figure 3 confirms that the sulfonated carbon-based catalyst consists of a sulfonated group and carbon (at 2θ ) 12 and 2θ ) 25).13 In addition, the TGA analysis result shown in Figure 4 indicates that the catalyst started to rapidly decompose in the temperature range between 200 and 400 °C, and all catalyst disappeared completely above 600 °C. 3.2. Test of Catalyst for Acetalization in Aqueous Solution. In applying the carbon-based catalyst for acetalization in the model mixture aqueous solution, the suitable amount of catalystwasfirstdeterminedbyvaryingthemassratioofcatalyst to 1,3-PDO from 0.1 to 0.9. The reaction was carried out at the temperature of 35 °C and the reaction time of 120 min. As shown in Figure 5, the conversion increased with increasing the catalyst to 1,3-PDO ratio from 0.1 to 0.7, in which the maximum value of 92% was achieved. At higher ratios, however, the conversion was not significantly changed; hence all subsequent experiments were carried out with 0.7 g of catalyst to 1 g of 1,3-PDO. In addition, the chemical equilibrium constants at various temperatures were determined and the results are shown in Table 2. These chemical equilibrium data were used for the calculation of enthalpy and entropy changes of the reaction using a graphical method following eq 3.
3.1. catalyst จำแนก คุณสมบัติทางกายภาพของ catalyst แน็พทาลี sulfonated ตามธรรมดา Dowex 50-WX4-200 และ Amberlite IR120-สารกรองเรซิ่นเช่นพื้นที่ผิว ปริมาตรที่รูขุมขน และเศษมีแสดงไว้ในตารางที่ 1 เดิมพันการประเมินบ่งชี้ว่า catalyst การแสดง specific ต่ำพื้นผิวตั้งและรูขุมขนปริมาณเปรียบเทียบกับแบบไฮโดรเจน Dowex 50-WX4-200 และ Amberlite IR120 ดังแสดงในตารางที่ 1 มีของ catalyst ที่วิเคราะห์โดยneutralization titration was also lower than those of Dowex 50WX4-200 and Amberlite IR120 hydrogen form and the values of acidity agree closely with the acid site densities calculated in the form of sulfonic acid site (estimated by elemental analysis). The sulfonic group on carbon-based catalyst was confirmed by the Nicolet NEXUS 670 FTIR as shown in Figure 2. The IR spectrum shows strong absorption at 1600-1800 cm-1, which confirms the SdO stretching bands of the catalyst, and a broad band at 2600-3500 cm-1 confirms the presence of OH.10 Furthermore, the XRD of the catalyst shown in Figure 3 confirms that the sulfonated carbon-based catalyst consists of a sulfonated group and carbon (at 2θ ) 12 and 2θ ) 25).13 In addition, the TGA analysis result shown in Figure 4 indicates that the catalyst started to rapidly decompose in the temperature range between 200 and 400 °C, and all catalyst disappeared completely above 600 °C. 3.2. Test of Catalyst for Acetalization in Aqueous Solution. In applying the carbon-based catalyst for acetalization in the model mixture aqueous solution, the suitable amount of catalystwasfirstdeterminedbyvaryingthemassratioofcatalyst to 1,3-PDO from 0.1 to 0.9. The reaction was carried out at the temperature of 35 °C and the reaction time of 120 min. As shown in Figure 5, the conversion increased with increasing the catalyst to 1,3-PDO ratio from 0.1 to 0.7, in which the maximum value of 92% was achieved. At higher ratios, however, the conversion was not significantly changed; hence all subsequent experiments were carried out with 0.7 g of catalyst to 1 g of 1,3-PDO. In addition, the chemical equilibrium constants at various temperatures were determined and the results are shown in Table 2. These chemical equilibrium data were used for the calculation of enthalpy and entropy changes of the reaction using a graphical method following eq 3.
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