Ibeh Paul O, García-Mateos Francisco J, Ruiz-Rosas Ramiro, Rosas Juana María, Rodríguez-Mirasol José, Cordero Tomás
Departamento de Ingeniería Química, Campus de Teatinos s/n, Universidad de Málaga, 29010 Málaga, Spain.
Materials (Basel). 2019 Jul 26;12(15):2394. doi: 10.3390/ma12152394.
Activated carbon monoliths (ACMs), with 25 cells/cm, were prepared from the direct extrusion of Alcell, Kraft lignin and olives stones particles that were impregnated with phosphoric acid, followed by activation at 700 °C. These ACMs were used as catalysts for methanol dehydration reaction under air atmosphere. ACM that was prepared from olive stone and at impregnation ratio of 2, OS2, showed the highest catalytic activity, with a methanol conversion of 75%, a selectivity to dimethyl ether (DME) higher than 90%, and a great stability under the operating conditions studied. The results suggest that the monolithic conformation, with a density channel of 25 cells/cm avoid the blockage of active sites by coke deposition to a large extent. Methanol conversion for OS2 was reduced to 29% in the presence of 8%v water, at 350 °C, although the selectivity to DME remained higher than 86%. A kinetic model of methanol dehydration in the presence of air was developed, while taking into account the competitive adsorption of water. A Langmuir-Hinshelwood mechanism, whose rate-limiting step was the surface reaction between two adsorbed methanol molecules, represented the experimental data under the conditions studied very well. An activation energy value of 92 kJ/mol for methanol dehydration reaction and adsorption enthalpies for methanol and water of -12 and -35 kJ/mol, respectively, were obtained.
采用直接挤出法，以磷酸浸渍的阿尔塞尔纤维素、硫酸盐木质素和橄榄石颗粒为原料，在700℃下活化制备了孔密度为25孔/平方厘米的活性炭整料（ACM）。这些ACM被用作空气气氛下甲醇脱水反应的催化剂。由橄榄石制备且浸渍比为2的ACM，即OS2，表现出最高的催化活性，甲醇转化率为75%，对二甲醚（DME）的选择性高于90%，并且在所研究的操作条件下具有很高的稳定性。结果表明，孔密度为25孔/平方厘米的整体结构在很大程度上避免了活性位点被焦炭沉积堵塞。在350℃、存在8%（体积分数）水的情况下，OS2的甲醇转化率降至29%，尽管对DME的选择性仍高于86%。建立了空气存在下甲醇脱水的动力学模型，同时考虑了水的竞争吸附。一种以两个吸附甲醇分子之间的表面反应为限速步骤的朗缪尔-欣谢尔伍德机理，很好地拟合了所研究条件下的实验数据。得到甲醇脱水反应的活化能值为92 kJ/mol，甲醇和水的吸附焓分别为-12 kJ/mol和-35 kJ/mol。
