scholarly journals A Review on the Hydroisomerisasion of n-Parafins over Supported Metal Catalysts

2021 ◽  
Vol 15 (2) ◽  
pp. 141
Author(s):  
Muhammad Safaat ◽  
Indri Badria Adilina ◽  
Silvester Tursiloadi
Keyword(s):  
Active Sites ◽  
Noble Metals ◽  
Catalyst Activity ◽  
Catalyst Support ◽  
Metal Catalyst ◽  
Supported Metal Catalysts ◽  
Reaction Conditions ◽  
High Level ◽  
Long Chain ◽  
Supported Metal

Catalytic hydroisomerization of n-paraffin aims to produce branched paraffin isomers and suppress cracking reactions in the production of the low cloud point of biodiesel. The development of the type of metal and catalyst support, amount of metal loading, and reaction conditions are important to increase the catalyst activity. A high performace catalyst for hydroisomerization bears bifunctional characteristics with a high level of hydrogenation active sites and low acidity, maximizing the progress of hydroisomerization compared to the competitive cracking reaction. In addition, a catalyst support with smaller pore size can hinder large molecular structure isoparaffins to react on the acid site in the pore thus providing good selectivity for converting n-paraffin. Catalysts loaded with noble metals (Pt or Pd) showed significantly higher selectivity for hydroisomerization than non-noble transition metals such as Ni, Co, Mo and W. The reaction temperature and contact time are also important parameters in hydroisomerization of long chain paraffin, because long contact times and high temperatures tend to produce undesired byproducts of cracking. This review reports several examples of supported metal catalyst used in the hydroisomerization of long chain hydrocarbon n-paraffins under optimized reaction conditions, providing the best isomerization selectivity results with the lowest amount of byproducts. The role of various metals and their supports will be explained mainly for bifunctional catalysts.

scholarly journals In situanomalous small-angle X-ray scattering from metal particles in supported-metal catalysts. II. Results

2005 ◽  
Vol 38 (2) ◽  
pp. 324-332 ◽  
Author(s):  
H. Brumberger ◽  
D. Hagrman ◽  
J. Goodisman ◽  
K. D. Finkelstein
Keyword(s):  
Small Angle ◽  
Platinum Metal ◽  
Metal Particles ◽  
Metal Catalyst ◽  
Supported Metal Catalysts ◽  
X Ray ◽  
Average Value ◽  
X Ray Scattering ◽  
Supported Metal ◽  
Ray Scattering

Information about the metal phase in a supported-metal catalyst can be obtained using anomalous small-angle X-ray scattering (ASAXS). The difference between the scattering profiles for SAXS at two different wavelengths near the metal's absorption edge is essentially the scattering of the metal alone. Novelin situASAXS measurements are made on mordenite impregnated with platinum metal while the temperature and composition of gas in the sample cell are changed. Measurements are made 62 times during treatment of the catalyst. The metal particles are assumed to be randomly distributed spheres withN(R)dR= number of spheres with radii betweenRandR+ dR. It is found thatN(R) is always a monotonically decreasing function ofR, and that the average value ofR, obtained fromN(R), decreases by a factor of two over the time (approximately 6 h) for which the system is observed.

scholarly journals Redispersion strategy for high-loading carbon-supported metal catalysts with controlled nuclearity

2021 ◽  
Author(s):  
Vera Giulimondi ◽  
Selina Kaiser ◽  
Mikhail Agrachev ◽  
Frank Krumeich ◽  
Adam Hugh Clark ◽  
...  
Keyword(s):  
Metal Catalysts ◽  
Synthetic Methods ◽  
High Loading ◽  
Supported Metal Catalysts ◽  
Single Atoms ◽  
High Level ◽  
Small Clusters ◽  
Supported Metal

Supported low nuclearity metal catalysts integrating single atoms or small clusters have emerged as promising materials for diverse applications. While sophisticated synthetic methods provide a high level of nuclearity control...

scholarly journals Boosting selective hydrogenation through hydrogen spillover on supported-metal catalysts at room temperature

2021 ◽  
Author(s):  
Sai Zhang ◽  
Zhaoming Xia ◽  
Mingkai Zhang ◽  
Yong Zou ◽  
Xiao Chen ◽  
...  
Keyword(s):  
Low Temperatures ◽  
Active Sites ◽  
Room Temperature ◽  
Metal Catalysts ◽  
Hydrogen Spillover ◽  
Binding Energies ◽  
Supported Metal Catalysts ◽  
High Turnover ◽  
Scaling Relationship ◽  
Supported Metal

Highly efficient hydrogenation of unsaturated substrates with strong absorption on metals at low temperatures is a long-term pursuit. However, due to the scaling relationship of high binding energies on metals, the poor activity and/or selectivity are frequently observed. Herein, we described a strategy of hydrogen spillover to break this scaling relationship to enable highly performed hydrogenation at low temperatures by constructing the dual-active site in supported-metal catalysts. Hydrogen and reactants are selectively activated on metal and the second active sites on support, respectively. Hydrogenation sequentially occurs on the second active sites via hydrogen spillover from metal to support. Easy desorption of surface-bounded products substantially re-generates the active sites. Guided by this design, for cinnamaldehyde hydrogenation, PtCo alloys (for H2 dissociation) supported on hydroxyl-abundant CoBOx (for aldehyde activation) delivered a high turnover frequency of 2479 h-1 (two orders of magnitude over PtCo/C) and 94.5% selectivity of cinnamyl alcohol at room temperature.

The promotion effect of π-π interactions in Pd NPs catalysed selective hydrogenation

2021 ◽  
Author(s):  
Miao Guo ◽  
Sanjeevi Jayakumar ◽  
Xiangtao Kong ◽  
Chunzhi Li ◽  
He Li ◽  
...  
Keyword(s):  
Active Sites ◽  
Weak Interactions ◽  
Activation Barrier ◽  
Pd Nanoparticles ◽  
Catalytic Performance ◽  
Supported Metal Catalysts ◽  
Rate Determining Step ◽  
Non Covalent Interactions ◽  
Supported Metal

Abstract The utilization of weak interactions to improve the catalytic performance of supported metal catalysts is an important strategy for catalysts design, but still remains a big challenge. Herein, the weak interactions nearby the Pd nanoparticles (NPs) were finely tuned by using a series of imine-linked covalent organic frameworks (COFs) with different conjugation skeletons. The Pd NPs embedded in pyrene-COF were ca. 3 to 10-fold more active than those in COFs without pyrene in the hydrogenation of aromatic ketones/aldehydes, quinolines and nitrobenzene, though Pd have similar size and surface structure. With acetophenone (AP) hydrogenation as a model reaction, systematic studies imply that the π-π interaction of AP and pyrene rings in the vicinity of Pd NPs could significantly reduce the activation barrier in the rate-determining step. This work highlights the important role of non-covalent interactions beyond the active sites in modulating the catalytic performance of supported metal NPs.

scholarly journals Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
Samira Bagheri ◽  
Nurhidayatullaili Muhd Julkapli ◽  
Sharifah Bee Abd Hamid
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
Catalyst Support ◽  
High Surface Area ◽  
Supported Metal Catalysts ◽  
Support Material ◽  
Oxidation Reactions ◽  
Base Property ◽  
Metal Support Interaction

The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2supported metal catalysts have attracted interest due to TiO2nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2as a support material for heterogeneous catalysts and its potential applications.

scholarly journals Combined Reforming of Clean Biogas over Nanosized Ni–Rh Bimetallic Clusters

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1345
Author(s):  
Nicola Schiaroli ◽  
Carlo Lucarelli ◽  
Maria Carmela Iapalucci ◽  
Giuseppe Fornasari ◽  
Antonio Crimaldi ◽  
...  
Keyword(s):  
Active Sites ◽  
Carbon Deposition ◽  
Bimetallic Nanoparticles ◽  
Catalyst Activity ◽  
Dry Reforming ◽  
Bimetallic Clusters ◽  
Low Carbon ◽  
Reaction Conditions ◽  
Active Particles ◽  
Highly Dispersed

The combined steam/dry reforming of clean biogas (CH4/CO2 = 50/50 v/v) represents an innovative way to produce synthesis gas (CO + H2) using renewable feeds, avoiding to deplete the fossil resources and increase CO2 pollution. The reaction was carried out to optimize the reaction conditions for the production of a syngas with a H2/CO ratio suitable for the production of methanol or fuels without any further upgrading. Ni-Rh/Mg/Al/O catalysts obtained from hydrotalcite-type precursors showed high performances in terms of clean biogas conversion due to the formation of very active and resistant Ni-Rh bimetallic nanoparticles. Through the utilization of a {Ni10Rh(CO)19}{(CH3CH2)4N}3 cluster as a precursor of the active particles, it was possible to promote the Ni-Rh interaction and thus obtain low metal loading catalysts composed by highly dispersed bimetallic nanoparticles supported on the MgO, MgAl2O4 matrix. The optimization of the catalytic formulation improved the size and the distribution of the active sites, leading to a better catalyst activity and stability, with low carbon deposition with time-on-stream.

scholarly journals Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 660 ◽  
Author(s):  
Rola Al Soubaihi ◽  
Khaled Saoud ◽  
Joydeep Dutta
Keyword(s):  
Low Temperature ◽  
Co Oxidation ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Activity ◽  
Cost Effective ◽  
Hysteresis Phenomenon ◽  
Reaction Conditions ◽  
Kinetic Oscillations ◽  
Low Temperature Co Oxidation

There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.

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