Catalytic performance of different zeolites for propane and CO2 coupling to propylene
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摘要: 丙烷脱氢制丙烯为吸热反应,同时伴随氢气的生成,而CO2加氢制低碳烯烃为放热反应,因此,将这两个反应耦合,可打破单一反应在热力学和动力学上的平衡限制,提高丙烯的产率。在此基础上进一步探究了不同晶型分子筛(HZSM-5、SAPO-34和Al-SBA-16)对丙烷与CO2耦合制丙烯反应性能的影响。通过XRD、SEM、NH3-TPD、N2吸附-脱附、TG等手段对不同晶型分子筛的性质进行表征,并在固定床反应器上考察了三种分子筛在丙烷和二氧化碳耦合制丙烯反应中的催化性能。实验结果表明,HZSM-5分子筛弱酸位点含量较高、比表面积大,且展现出优异的催化性能。当丙烷与CO2的体积比为1: 4,反应压力为0.1 MPa,反应温度为580 ℃,催化剂用量为0.2 g,空速为6000 mL/(gcat·h)时,丙烷转化率为10.5%,CO2转化率为3.0%,丙烯选择性为38.4%、产率为4.0%。Abstract: CO2 hydrogenation to light olefins is an exothermic reaction, while propane dehydrogenation to propylene is an endothermic reaction, and with generating of hydrogen. Coupling of the two reactions can break the equilibrium limit of thermodynamics and dynamics of the single reaction and improve yield of propylene. Therefore, the effects of different crystalline zeolites (HZSM-5, SAPO-34 and Al-SBA-16) on the reactivity of propane coupled with CO2 to propylene were investigated. The properties of different zeolites were characterized by means of XRD, SEM, NH3-TPD, N2 desorption and TG, and the catalytic performance of the three different zeolites in the reaction of propane and carbon dioxide coupling to propylene was investigated in a fixed bed reactor. The experimental results showed that HZSM-5 zeolite had high content of weak acid, large specific surface area and excellent catalytic activity. Typically the propane conversion rate is 10.5%, the CO2 conversion is 3.0%, the propylene selectivity is 38.4 and the yield is 4.0% when the volume ratio of propane to CO2 is 1:4, the reaction pressure is 0.1 MPa, the reaction temperature is 580 ℃, the catalyst mass is 0.2 g and the space velocity is 6000 mL/(gcat·h).
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Key words:
- zeolites /
- coupling reaction /
- propane /
- carbon dioxide /
- propylene
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表 1 催化剂的酸浓度和酸位强度
Table 1 Concentration and strength of acid sites of catalysts
Sample Concentration of
acid sites (a.u.·g−1)Strength of
acid sites/℃weak medium strong weak medium strong HZSM-5 75 132 134 126 183 347 SAPO-34 1058 866 1445 191 327 429 Al-SBA-16 26 10 35 114 306 340 表 2 催化剂的结构特性
Table 2 Textural properties of the catalysts
Sample SBET/
(m2·g−1)Smic/
(m2·g−1)Smes/
(m2·g−1)vmic/
(cm3·g−1)vtotal/
(cm3·g−1)HZSM-5 326.50 193.43 133.07 0.104 0.194 SAPO-34 219.67 200.97 18.71 0.117 0.119 Al-SBA-16 274.25 80.55 193.70 0.043 0.279 SBET (surface area calculated by BET), Smic (surface area of micropores by t-plot method),Smes = SBET − Smic, vmic (micropore volume by t-plot method), vtotal ((total pore volume) -
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