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Catalysis

Catalysis

The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation

Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide

Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.

Reduction of Alkenes: Catalytic Hydrogenation

Reduction of Alkenes: Catalytic Hydrogenation

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Reduction of Alkenes: Asymmetric Catalytic Hydrogenation

Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

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Related Experiment Video

Updated: Sep 9, 2025

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

Published on: July 4, 2017

Boosting Ag/Al₂O₃ Catalytic Activity for NO_x Removal via C₃H₆-SCR through Functional TiO₂ Support Engineering.

Yun Zhong^1,2, Yingsheng An^3,4, Zidi Yan²

¹School of Rare Earths, University of Science and Technology of China, Hefei 230026, China.

Environmental Science & Technology

|August 28, 2025

Summary

A novel TiO2-modified alumina catalyst significantly boosts hydrocarbon selective catalytic reduction (HC-SCR) of nitrogen oxides. This advanced Ag/TiO2/Al2O3 catalyst offers superior activity and stability for cleaner emissions.

Keywords:

Ag state Ag/Al2O3 HC-SCR TiO2 nitrogen oxide

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The Effect of Interfacial Chemical Bonding in TiO2-SiO2 Composites on Their Photocatalytic NOx Abatement Performance

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Published on: July 4, 2017

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Synthesis of Platinum-nickel Nanowires and Optimization for Oxygen Reduction Performance

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Published on: April 27, 2018

Area of Science:

Catalysis
Materials Science
Environmental Chemistry

Background:

Alumina-supported silver (Ag/Al2O3) is a potential catalyst for hydrocarbon selective catalytic reduction (HC-SCR) of nitrogen oxides (NOx).
Current Ag/Al2O3 catalysts exhibit limited performance, hindering practical application in emission control.

Purpose of the Study:

To develop a highly efficient Ag/TiO2/Al2O3 catalyst for enhanced HC-SCR performance.
To investigate the role of TiO2 modification in improving catalyst activity, durability, and stability.

Main Methods:

Fabrication of a TiO2-modified AlOOH precursor for catalyst synthesis.
Evaluation of the catalyst's performance in C3H6-SCR across a wide temperature range.
Mechanistic studies using electron transfer and activation energy analysis.

Main Results:

The Ag/TiO2/Al2O3 catalyst demonstrated significantly enhanced activity, durability, and stability compared to Ag/Al2O3.
TiO2 incorporation strengthened Ag-support interaction, promoting electron transfer and forming highly dispersed Agny+ clusters.
A new NOx reduction pathway via -CN intermediates was identified, lowering the activation energy barrier.

Conclusions:

The novel TiO2 modification strategy effectively enhances HC-SCR performance by optimizing active sites and reactivity.
Agny+ clusters are identified as key active species, accelerating hydrocarbon oxidation and facilitating NOx reduction.
This research provides valuable insights for designing advanced catalysts for HC-SCR applications.