Selective hydrodechlorination of trichloromethane to dichloromethane over bimetallic Pt-Pd/KIT-6: Catalytic activity and reaction kinetics

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2018-01, Vol.331, p.556-569
• Main Authors: Lee, Sae Rom, Cho, Jae Min, Son, Minji, Park, Myung-June, Yong Kim, Woon, Kim, Sang Yob, Bae, Jong Wook
• Format: Article
• Language: English
• Subjects: Dichloromethane (DCM); Pt-Pd/KIT-6; Reaction kinetics; Selective hydrodechlorination (HDC); Trichloromethane (TCM)
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2017.09.035

[Display omitted] •HDC of TCM to DCM was studied on the mesoporous 2wt%Pt-0.05wt%Pd/KIT-6.•At an optimal calcination T=400°C, a maximum DCM yield was obtained.•Close interactions of smaller Pt-Pd nanoparticles with higher oxidation states are beneficial for a higher DCM yield.•The kinetic model based on LHHW was well fitted with experimental results.•Higher DCM productivity was achievable at the highest SV and lowest H2/TCM ratio. Selective hydrodechlorination (HDC) of trichloromethane (TCM, CHCl3) to dichloromethane (DCM, CH2Cl2) was studied on the mesoporous bimetallic Pt-Pd/KIT-6 to verify the roles of the active bimetals to catalytic activity and product distribution. The optimal bimetal ratio of 2wt%Pt-0.05wt%Pd on the highly ordered mesoporous KIT-6 calcined at 400°C showed a maximum TCM conversion with DCM yield, and the optimal calcination temperature of Pt-Pd/KIT-6 was mainly responsible for the formation of homogeneously and closely distributed smaller Pt-Pd nanoparticles with higher oxidation states of Pt crystallites supported by XPS and EXAFS analysis. Based on the proposed kinetic models on the optimal Pt-Pd/KIT-6, the competitive reaction mechanisms of the formations of CH4 and monochloromethane (MCM, CH3Cl) from DCM intermediate can well explain the product distributions. Using the seven different kinetic models, the best model on the basis of the Akaike’s Information Criteria showed the activation energies of the HDC of TCM to be in the range of 18–60kJ/mol. The kinetic model also revealed the inverse relationship between the conversion of TCM and selectivity to DCM. Either an increase of space velocity or decrease of H2/TCM ratio increased the DCM yield, while there existed the optimal operating conditions. The DCM productivity of 1.5mol-DCM/(gcat·h) was achievable at the highest space velocity and lowest H2/TCM ratio under a specific reaction condition of 190°C and 0.1MPa.