Formation of carbonaceous deposits on Pd-based hydrodechlorination catalysts: Vibrational spectroscopy investigations over Pd/Al2O3 and Pd/SOMS
Formation of carbonaceous deposits on Pd-based hydrodechlorination catalysts: Vibrational spectroscopy investigations over Pd/Al2O3 and Pd/SOMS
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DOI：
10.1016/j.cattod.2018.05.001
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发表时间：
2019-02
期刊：
影响因子：
5.3
通讯作者：
G. Celik;Saurabh Ailawar;S. Gunduz;P. Edmiston;U. Ozkan
中科院分区：
文献类型：
--
作者：
G. Celik;Saurabh Ailawar;S. Gunduz;P. Edmiston;U. Ozkan
由于催化剂失活问题（例如在 HDC 的还原环境下形成碳质沉积物），基于钯基催化剂的加氢脱氯（HDC）作为一种修复技术的广泛应用和商业化受到阻碍。在这项研究中，我们研究了使用一种新型活性材料——可溶胀有机改性二氧化硅（SOMS）作为三氯乙烯（TCE）HDC的催化剂支架，以开发一种抗碳形成的催化系统。表征了 Pd/SOMS 上吸附的 TCE 的聚集状态。研究发现，SOMS 支架的独特性质导致 SOMS 基质中吸附剂发生凝结。考虑到由于冷凝而导致反应物局部浓度增加可能增强催化反应的动力学这一事实，这一点特别重要。为了确定反应条件下对碳质材料形成的抵抗力，在反应物流中存在和不存在水蒸气的情况下，在掺钯 SOMS 上进行了原位振动光谱实验（漫反射红外傅里叶变换光谱 (DRIFTS) 和激光拉曼光谱）。为了进行比较，还对常用的 HDC 催化剂 Pd/Al2O3 进行了研究。在 Pd/Al2O3 上观察到不同性质的碳沉积物的形成，而在 Pd/SOMS 上没有观察到可检测到的碳形成。已证实呈碱性的表面羟基起到焦化剂的作用。 Pd/SOMS的抗积碳行为与表面羟基的性质和低浓度密切相关。
The widespread utilization and commercialization of hydrodechlorination (HDC) over Pd-based catalysts as a remediation technique has been impeded because of catalyst deactivation problems such as formation of carbonaceous deposits under the reductive environment of HDC. In this study, we investigated the use of a novel animated material, swellable organically-modified silica (SOMS), as a catalyst scaffold for HDC of trichloroethylene (TCE) to develop a catalytic system resistant to carbon formation. The state of aggregation of adsorbed TCE on Pd/SOMS was characterized. It was found that the unique nature of SOMS scaffold caused condensation of adsorbents in the SOMS matrix. This is of particular importance considering the fact that the increase of local concentration of reactants due to condensation may enhance the kinetics of catalytic reactions. To determine the resistance to the formation of carbonaceous materials under reaction conditions, in-situ vibrational spectroscopy experiments (diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and laser Raman spectroscopy) were undertaken over Pd-incorporated SOMS in the absence and presence of water vapor in the reactant stream. The commonly used HDC catalyst Pd/Al2O3was also studied for comparison purposes. Formation of carbonaceous deposits of different nature were observed over Pd/Al2O3whereas no detectable carbon formation was observed over Pd/SOMS. It was confirmed that surface hydroxyl groups which are in basic character act as coking agents. The carbon formation resistant behavior of Pd/SOMS is closely related to the nature and low concentration of surface hydroxyl groups.