scholarly journals Selective hydrogenation of benzyl cyanide to 2-phenylethylamine over a Pd/Al2O3 catalyst promoted by synergistic effects of CO2 and water

2015 ◽  
Vol 17 (2) ◽  
pp. 1299-1307 ◽  
Author(s):  
Ashvini Bhosale ◽  
Hiroshi Yoshida ◽  
Shin-ichiro Fujita ◽  
Masahiko Arai
Keyword(s):  
Selective Hydrogenation ◽  
Catalyst Deactivation ◽  
Synergistic Effects ◽  
Benzyl Cyanide ◽  
Al2o3 Catalyst

Synergistic effects of water and CO2 appear for the selective hydrogenation of benzyl cyanide to phenylethylamine in n-hexane over a Pd/Al2O3 catalyst with no catalyst deactivation.

Kinetics of Selective Hydrogenation of Pyrolysis Gasoline over Pd/Al2O3 Catalyst

2021 ◽  
Vol 62 (6) ◽  
pp. 750-755
Author(s):  
Haowen Ma ◽  
Minglin Chen ◽  
Limin Sun ◽  
Huixia Feng ◽  
Xuecheng Zhan ◽  
...  
Keyword(s):  
Selective Hydrogenation ◽  
Pyrolysis Gasoline ◽  
Kinetics Of ◽  
Al2o3 Catalyst

An egg-shell bifunctional CeO2-modified NiPd/Al2O3 catalyst for petrochemical processes involving selective hydrogenation and hydroisomerization

2020 ◽  
Author(s):  
Franklin J. Méndez ◽  
Javier A. Alves ◽  
Yahsé Rojas-Challa ◽  
Oscar Corona ◽  
Yanet Villasana ◽  
...  
Keyword(s):  
Selective Hydrogenation ◽  
Egg Shell ◽  
Al2o3 Catalyst

scholarly journals An Experimental Approach on Industrial Pd-Ag Supported α-Al2O3 Catalyst Used in Acetylene Hydrogenation Process: Mechanism, Kinetic and Catalyst Decay

Processes ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 136
Author(s):  
Ourmazd Dehghani ◽  
Mohammad Rahimpour ◽  
Alireza Shariati
Keyword(s):  
Kinetic Model ◽  
Experimental Approach ◽  
Catalyst Deactivation ◽  
Catalyst Activity ◽  
Hydrogenation Process ◽  
Support Surface ◽  
Acetylene Hydrogenation ◽  
Wide Range ◽  
Α Al2o3 ◽  
Al2o3 Catalyst

The current research presents an experimental approach on the mechanism, kinetic and decay of industrial Pd-Ag supported α-Al2O3 catalyst used in the acetylene hydrogenation process. In the first step, the fresh and deactivated hydrogenation catalysts are characterized by XRD, BET (Brunauer–Emmett–Teller), SEM, TEM, and DTG analyses. The XRD results show that the dispersed palladium particles on the support surface experience an agglomeration during the reaction run time and mean particle size approaches from 6.2 nm to 11.5 nm. In the second step, the performance of Pd-Ag supported α-Al2O3 catalyst is investigated in a differential reactor in a wide range of hydrogen to acetylene ratio, temperature, gas hourly space velocity and pressure. The full factorial design method is used to determine the experiments. Based on the experimental results ethylene, ethane, butene, and 1,3-butadiene are produced through the acetylene hydrogenation. In the third step, a detailed reaction network is proposed based on the measured compounds in the product and the corresponding kinetic model is developed, based on the Langmuir-Hinshelwood-Hougen-Watson approach. The coefficients of the proposed kinetic model are calculated based on experimental data. Finally, based on the developed kinetic model and plant data, a decay model is proposed to predict catalyst activity and the parameters of the activity model are calculated. The results show that the coke build-up and condensation of heavy compounds on the surface cause catalyst deactivation at low temperature.

Selective hydrogenation of γ-valerolactone to 2-methyltetrahydrofuran over Cu/Al2O3 catalyst

2020 ◽  
Vol 590 ◽  
pp. 117309 ◽  
Author(s):  
Daolai Sun ◽  
Takeshi Saito ◽  
Shota Otsuka ◽  
Tomohiro Ozawa ◽  
Yasuhiro Yamada ◽  
...  
Keyword(s):  
Selective Hydrogenation ◽  
Al2o3 Catalyst

scholarly journals Contrasting Arene, Alkene, Diene, and Formaldehyde Hydrogenationin H-ZSM-5, H-SSZ-13, and H-SAPO-34 Zeolite Frameworks during MTO

2019 ◽  
Author(s):  
Mykela DeLuca ◽  
Christina Janes ◽  
David Hibbitts
Keyword(s):  
Selective Hydrogenation ◽  
Density Functional ◽  
High Pressures ◽  
Catalyst Deactivation ◽  
Zeolite Catalysts ◽  
Functional Theory ◽  
As Species ◽  
Methanol To Olefin ◽  
Alkene Hydrogenation ◽  
Thermodynamic Instability

<p>Co-feeding H<sub>2</sub> at high pressures increases zeolite catalyst lifetimes during methanol-to-olefin (MTO) reactions while maintaining high alkene-to-alkane ratios; however, the mechanisms and species hydrogenated by H<sub>2</sub> co-feeds to prevent catalyst deactivation remain unknown. This study uses periodic density functional theory (DFT) to examine hydrogenation mechanisms of MTO product C<sub>2</sub>–C<sub>4</sub> alkenes, as well as species related to the deactivation of MTO catalysts such as C<sub>4</sub> and C<sub>6</sub> dienes, benzene, and formaldehyde in H-MFI and H-CHA zeolite catalysts. Results show that dienes and formaldehyde are selectively hydrogenated in both frameworks at MTO conditions because their hydrogenation transition states proceed via allylic and oxocarbenium cations which are more stable than alkylcarbenium ions which mediate alkene hydrogenation. Diene hydrogenation is further stabilized by protonation and hydridation at α,δ positioned C-atoms to form 2-butene from butadiene and 3-hexene from hexadiene as primary hydrogenation products. This α,δ-hydrogenation directly leads to selective hydrogenation of dienes; pathways which hydrogenate dienes at the α,β-position (e.g., forming 1-butene from butadiene) proceed with barriers 20 kJ mol<sup>-1</sup> higher than α,δ-hydrogenation and with barriers nearly equivalent to butene hydrogenation, despite α,β-hydrogenation of butadiene also occurring through allylic carbocations. Hydrogenation of formaldehyde, a diene precursor, occurs with barriers that are within 15 kJ mol<sup>-1</sup> of diene hydrogenation barriers, indicating that it may also contribute to increasing catalyst lifetimes by preventing diene formation. Benzene, in contrast to dienes and formaldehyde, is hydrogenated with higher barriers than C<sub>2</sub>–C<sub>4</sub> alkenes despite proceeding via stable benzenium cations because of the thermodynamic instability of the product which has lost aromaticity. Carbocation stabilities predict the relative rates of alkene hydrogenation and in some cases shed insights into the hydrogenation of benzene, dienes, and formaldehyde, but cation stabilities alone cannot account for the poor hydrogenation of benzene or the facile hydrogenation of dienes, boosted by stabilization conferred by a,δ-hydrogenation. This work suggests that the main mechanisms of catalyst lifetime improvement with high H<sub>2</sub> co-feeds is reduction of diene concentrations through both their selective hydrogenation and hydrogenation of their precursors to prevent formation of deactivating polyaromatic species.</p>

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