Kinetic study of dry reforming of Methane with Ni over different supports and Pt/Al2O3

This thesis presents a kinetic study on Ni series catalysts for dry reforming of methane (DRM) and comparison with a commercially noble metal catalyst Pt/Al2O3. For each catalyst, a corresponding kinetic model needs to be established. These kinetic schemes should be sophisticated enough to describe the consumption rates, meanwhile rather simple for industrial applications. In this thesis, we intend to investigate three aspects. The first is to establish individual kinetic models for each catalyst. Second, based on the similarity and difference of Ni series catalysts in the models, we want to know the support influence on the catalytic performance. Third, by comparing Ni series catalysts with noble metal catalyst Pt, it is interesting to see what is the similarity and difference among the different kinetic models. Here three kinds of supports were used to support Ni nanoparticles: Al2O3, SBA-15, and ZrO2. In order to investigate CH4 and CO2 influence of on the DRM reaction, the different partial pressure of CH4 and CO2 were dosed into the reactors in a parameter field test. In order to study the influence of products CO and H2 on reaction network, respective co-feeds CO and H2 were added. Therefore, the complete kinetic test can be divided into three parts: stabilization period, parameter field test, and co-feed test. For the stabilization period, the feed composition amounted to 10% CH4, 10% CO2, 10% N2 and 70% He. For the parameter field test, CH4 and CO2 concentration were varied from 5 to 20%. The reaction temperature was adjusted to 500, 600, and 700°C. By applying different catalysts masses, different space velocities were obtained. Fresh catalysts and spent catalysts were characterized by TEM, CHN, XRD, ICP, and XPS. Significant coke deposition was observed for Ni/Al2O3 and Pt/Al2O3. Ni/ZrO2 shows better stability with no significant change in morphology, no particle size change, and no visible coke deposition. Based on the experimental data, two theories were used for modeling: power-law and Langmuir-Hinshelwood theory. For each theory, different assumptions were used to form different models to find the best fitting model for the reaction data. From the research, Ni series catalysts are all very active, especially Ni/Al2O3 and Ni/SBA-15. Ni/ZrO2 is not comparably active, but the stability is outstanding. For Ni/Al2O3 and Ni/SBA-15, one power-law model and one Langmuir-Hinshelwood model fit well the reaction data, and the Langmuir-Hinshelwood model with the assumption of one type of active site on the surface provided the best agreement with the experimental data. Even though the best-fitting models for Ni/Al2O3 and Ni/SBA-15 were the same, the respective model parameters of each catalyst, like reaction orders, apparent activation energy, are different. However, due to the reaction system complexity, which means that reverse water gas shift reaction could be dominant in the Ni/ZrO2 reaction system, it is difficult to apply the similar models of DRM for Ni/ZrO2. As for Pt/Al2O3, in this study, it appears to be not active enough to have reliable data for the kinetic study, and the catalyst stability is terrible too. Therefore, it is also challenging to build up a fitting model for Pt/Al2O3.

Author dc:creator

• Guan, Chengyue

Advisors dc:contributor.advisor

• Krähnert, Ralph
• Rosowski, Frank
• Schomäcker, Reinhard

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Identifier URI

http://dx.doi.org/10.14279/depositonce-8655

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/9609