Applied Catalysis A: General ( IF 5.5 ) Pub Date : 2017-08-05 , DOI: 10.1016/j.apcata.2017.08.005 Karen A. Resende , Carla E. Hori , Fabio B. Noronha , Hui Shi , Oliver Y. Gutierrez , Donald M. Camaioni , Johannes A. Lercher
The impact of particle size of ZrO2-supported Pd and of alloying with Ag was explored for hydrogenation of phenol in aqueous phase. Kinetic assessments were performed in a batch reactor, on monometallic Pd/ZrO2 samples with different Pd loadings (0.5%, 1% and 2%), as well as on a 1% PdAg/ZrO2 sample. The catalytic activity normalized to accessible Pd (turnover frequency, TOF) increased with the particle size of Pd. Reaction orders in phenol and H2 and lower activation energies suggest that smaller particles bind the reacting substrates more strongly, leading to higher surface coverages by phenol. However, surprisingly, smaller Pd particles exhibited lower TOFs. The lower activity of the small Pd particles is attributed to lower activation entropies for the strongly bound species. The presence of Ag increased the catalyst activity by decreasing the apparent energy of activation and increasing the coverages of phenol and H2, without negatively affecting the activation entropy.
中文翻译:
Pd和PdAg在ZrO 2上催化的苯酚水相加氢
研究了ZrO 2负载的Pd的粒径以及与Ag合金化对水相中苯酚加氢的影响。在间歇反应器中,对具有不同Pd含量(0.5%,1%和2%)的单金属Pd / ZrO 2样品以及1%PdAg / ZrO 2样品进行动力学评估。归一化为可及Pd的催化活性(周转频率,TOF)随Pd粒径的增加而增加。苯酚和H 2中的反应顺序较低的活化能表明较小的颗粒更牢固地结合反应的底物,从而导致苯酚具有较高的表面覆盖率。但是,令人惊讶的是,较小的Pd颗粒显示出较低的TOF。小Pd颗粒的较低活性归因于强结合物种的较低活化熵。Ag的存在通过降低活化的表观能量和增加苯酚和H 2的覆盖率而增加了催化剂活性,而对活化熵没有负面影响。