Zn-and Ti-Modified Hydrotalcites for Transesterification of Dimethyl Terephthalate with Ethylene Glycol: Effect of the Metal Oxide and Catalyst Synthesis Method
Zn-and Ti-Modified Hydrotalcites for Transesterification of Dimethyl Terephthalate with Ethylene Glycol: Effect of the Metal Oxide and Catalyst Synthesis Method
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DOI：
10.1021/acsomega.9b02230
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发表时间：
2020-02-11
期刊：
影响因子：
4.1
通讯作者：
Yadav, Ganapati D.
中科院分区：
文献类型：
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作者：
Jadhav, Amarsinh L.;Malkar, Radhika S.;Yadav, Ganapati D.
添加不同的金属氧化物可以适当提高水滑石的活性和选择性。锌和钛是这种修饰的潜在候选者。对苯二甲酸二甲酯(DMT)和乙二醇酯(EG)在碱性催化剂作用下的酯交换反应是生产对苯二甲酸二(2-羟乙基)酯(BHET)的重要工艺。BHET是聚对苯二甲酸乙二醇酯(PET)的前体，用于生产薄膜、纤维和模塑材料。与使用污染液体的碱相比，可以使用固体碱。在本工作中，我们研究了改性的HT碱催化剂上DMT和EG的酯交换反应，其中的HT是通过添加锌和钛来活化的。这些催化剂是用不同的燃料通过燃烧合成得到的。用扫描电子显微镜、能量色散X-射线能谱、Brunauer-Emmett-Teller比表面积分析仪、程序升温脱附和X-射线衍射仪对锌和钛改性的HT进行了表征。考察了几个参数对反应速度和限制试剂转化率的影响。以甘氨酸为燃料的锌改性HT型催化剂(锌-羟基甘氨酸)被认为是选择性最高、活性最高、可重复使用的催化剂。采用Langmuir-HinShelwood-Hougen-Watson模型建立了反应机理和动力学模型。所有物种都被弱吸附，表现为二级动力学。当DMT与EG的摩尔比为1：2，负载量为0.05g/cm(3)时，在180℃下反应4h，DMT的转化率为64.1%，BHET的选择性为96.1%，表观活化能为9.64 kcal/mol。催化剂坚固耐用，可重复使用。
The activity and selectivity of hydrotalcites (HTs) can be suitably enhanced by the addition of different metal oxides. Zinc and titanium are prospective candidates for such a modification. Transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) using basic catalysts is an industrially important process for the production of bis(2-hydroxyethyl)terephthalate (BHET). BHET is a precursor for polyethylene terephthalate (PET) which is used in production of films, fibers, and molding materials. As against use of polluting liquid bases, solid bases could be employed. In the current work, transesterification of DMT with EG was studied over modified HT base catalysts wherein the HT was activated with the addition of zinc and titanium. These catalysts were prepared by the combustion synthesis using different fuels. The modified HT using Zn and Ti were well characterized by scanning electron microscopy, energy-dispersive X-ray spectrometry, Brunauer-Emmett-Teller surface area analyzer, temperature-programmed desorption, and X-ray diffraction. Effects of several parameters on the rate of reaction and conversion of the limiting reagent were investigated. Zinc-modified HT using glycine as fuel (Zn-HT-glycine) was found to be the most selective, active, and reusable catalyst. The Langmuir-Hinshelwood-Hougen-Watson model was used to establish the reaction mechanism and kinetics. All species were weakly adsorbed leading to a second-order kinetics. Using a mole ratio of 1:2 of DMT to EG and 0.05 g/cm(3) Zn-HT-glycine loading resulted in to 64.1% conversion of DMT and 96.1% selectivity to BHET in 4 h at 180 degrees C. The apparent activation energy was 9.64 kcal/mol. The catalyst was robust and reusable.