Archive for the ‘Reviews’ Category

Nanoflower photocatalysts

This ‘advance article’ minireview from Liwu Zhang and Yongfa Zhu covers the interesting topic of converting photon energy into chemical energy to decompose organic contaminants. There are many types of heterogeneous photocatalyst which can do this, however many of them work only in the UV region of the spectrum. The authors here look at the family of Bi2WO6 compounds which are highly active under visible light, the photocatalytic mechanism of the nanoplates is revealed and several methods to develop and improve the catalysts is discussed.

All articles in Catalysis Science & Technology are free to access for 2012, which covers topics including biocatalysis, heterogeneous catalysis, homogeneous catalysis and organocatalysis. Accepted manuscripts are also published as soon as possible in a citable form.

A review of controllable synthesis and enhancement of performances of bismuth tungstate visible-light-driven photocatalysts
Yongfa Zhu and Liwu Zhang
Catal. Sci. Technol., 2011, Accepted Manuscript
DOI: 10.1039/C2CY00411A
Received 05 Oct 2011, Accepted 11 Dec 2011
First published on the web 12 Dec 2011

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Biofuel synthesis – cutting winter fuel bills?

Looking briefly over the year in Catalysis Science & Technology we can see an interesting area of research has been in the generation of Biodiesel, a particularly interesting prospect given recent hikes in fuel prices and the seasonal drop in temperature in the Northern Hemisphere. Bert Sels et al. gave an interesting Perspective ‘Chemocatalytic conversion of cellulose: opportunities, advances and pitfalls’, which outlines the great chemical potential locked up in cellulose such as sugars, hexitols, ethylene glycol, gluconic acid and biofuels. Unlocking these valuable chemicals is a hot topic for research in catalysis but as you can see in their article there are several catalytic steps required and this can be expensive.

A route to making biodiesel more financially favourable is to use cheaper raw materials, but these can contain high levels of free fatty acids which aren’t compatible with current homogeneous base catalysts used for transesterification, an important reaction for biodiesel production. In their paper  Nakka Lingaiah et al. discuss the use of 12-tungstophosphoric acid (TPA) supported on SnO2 as a solid acid catalyst, catalysing the esterification and transesterification of fatty free acids and triglycerides in palmitic oil and methanol. Chunli Xu and Qiang Liu doped KF onto mixed oxide or single oxide supports containing Mg, Cu, Zn, Co, Al, Cr, Ni and Fe. When they tested for transesterification with vegetable oil and methanol their solid base catalysts produced biodiesel yields in the range of 73–98%, their article discusses the activities of their compounds in detail.

 

 

Soybean oil is one of the widest used biodiesels in the world however it is highly susceptible to oxidation. Paulo Suarez and colleagues discuss in their research paper a process for selective partial hydrogenation, protecting the fuel from degradation and increasing storage shelf life. Interestingly in situ generated palladium nanoparticles play a key role in this process.

Follow developments of all things catalysis in Catalysis Science & Technology, which is free to access for the duration of 2012.

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Hot Perspective: Organocatalytic enantioselective catalysis

Lately, the use of Morita–Baylis–Hillman (MBG) carbonates and acetates in organocatalysis has grown exponentially opening new gates for the synthesis of C–C or C-heteroatom bonds in an enantioselective fashion and under mild conditions. This work provides access to many highly functionalized structures. In his recent Hot Perspective article, Ramon Rios covers these exciting reactions, paying special attention on the nature of the MBH adduct……

Organocatalytic enantioselective methodologies using Morita–Baylis–Hillman carbonates and acetates
A Perspective by Ramon Rios
Catal. Sci. Technol., 2012, DOI: 10.1039/C1CY00387A

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HOT Article: Asymmetric Iron Catalysts

From the Haber process to discrete enzymatic reactions iron is an important element in catalytic chemistry. Up until recently, however, iron has been significantly under-utilised as a homogeneous catalyst in organic synthesis compared to other transition metals. Recently homogeneous iron-based catalysts have undergone much development with some notable breakthroughs. Muftah Darwish and Martin Wills have compiled a thorough review of these in their HOT Perspective “Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?”. If you’re looking to reduce ketones or imines, perform transfer hydrogenation or asymmetric hydrosilylation this review will bring you up to date on the latest and greatest capabilities of these advanced iron complexes.

Read the full article for free in Catalysis Science & Technology.

 

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?
Muftah Darwish and Martin Wills
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C1CY00390A, Perspective

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HOT Minireview: Graphene & catalysis

Catalytic uses of graphene and its composities have shown promising results.

Catalytic uses of graphene and its composities have shown promising results.

In this Catalysis Science & Technology HOT Minireview Bruno Machado and Philippe Serp give a broad overview of topics relating to graphene and its application in synthesis and catalysis.  The outstanding physical, chemical and mechanical properties of graphene have attracted huge amounts of attention and Machaso and Serp attempt to distill out the properties and characterisation techniques of graphene that are pertinent to catalysis.

Read more for free until the 29th November 2011 at:

Graphene-based materials for catalysis
Bruno F. Machado and Philippe Serp
Catal. Sci. Technol., 2012, Advance Article
DOI: 10.1039/C1CY00361E

Why not check-out some other articles published in Catalysis Science & Technology featuring graphene:

In situ green synthesis of Au nanostructures on graphene oxide and their application for catalytic reduction of 4-nitrophenol
Yingwei Zhang, Sen Liu, Wenbo Lu, Lei Wang, Jingqi Tian and Xuping Sun
Catal. Sci. Technol., 2011, 1, 1142-1144
DOI: 10.1039/C1CY00205H

Microwave-assisted synthesis of ZnO–graphene composite for photocatalytic reduction of Cr(VI)
Xinjuan Liu, Likun Pan, Tian Lv, Ting Lu, Guang Zhu, Zhuo Sun and Changqing Sun
Catal. Sci. Technol., 2011, 1, 1189-1193
DOI: 10.1039/C1CY00109D

Graphene support for enhanced electrocatalytic activity of Pd for alcohol oxidation
Ravindra Nath Singh and Rahul Awasthi
Catal. Sci. Technol., 2011, 1, 778-783
DOI: 10.1039/C1CY00021G

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Capturing carbon dioxide electrochemically

Over the past several years, there has been a growing interest in the capture of carbon dioxide emissions and either their permanent immobilization or chemical conversion to industrially relevant products. Though several processes have been developed to capture CO2, many of them are quite expensive since they require either ultra high purity CO2 or are energy intensive. Also, many purely chemical methods show low product selectivity.

This Perspective article, by William Mustain and co-workds, looks at ways in which electrochemical, photoelectrochemical and bioelectrochemical methods could be used for CO2 conversion. Electrochemical processes can reduce cost and increase reaction selectivity because they allow for direct control of the surface free energy.

Find out more about electrochemical solutions to the carbon capture problem in Mustain’s Hot Catalysis Science & Technology Perspective:

Recent progress in the electrochemical conversion and utilization of CO2
Neil S. Spinner, Jose A. Vega and William E. Mustain
Catal. Sci. Technol., 2012, DOI: 10.1039/C1CY00314C

You can read this article for free – if you haven’t already why not sign up for free access to Catalysis Science & Technology here.

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Review article: Molecular kinetics of the Fischer-Tropsch reaction

This review article by Rutger van Santen and colleagues from Eindhoven University of Technology, looks at how the Fischer-Tropsch reaction converts synthesis gas into hydrocarbons.

Read the full article to find out more…

Structure sensitivity of the Fischer–Tropsch reaction; molecular kinetics simulations
Rutger A. van Santen, Mohammed Minhaj Ghouri, Sharan Shetty and Emiel M. H. Hensen
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00118C

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Flattening catalysts

Hans Niemantsverdriet, Eindhoven University of Technology

In their recent Catalysis Science & Technology Perspective article, Hans Niemantsverdriet and colleagues look at how nanoparticle model systems on planar supports can be used to study changes under realistic reaction conditions. 

This work has allowed the group to gain insight into many aspects of catalysis – for example it provides a window into the mechanisms of catalyst regeneration. Read this Hot Article now to find out more about recent advances in studying catalyis using planar supports – FREE to read!

Studying Fischer–Tropsch catalysts using transmission electron microscopy and model systems of nanoparticles on planar supports
P. C. Thüne, C. J. Weststrate, P. Moodley, A. M. Saib, J. van de Loosdrecht, J. T. Miller and J. W. Niemantsverdriet
Catal. Sci. Technol., 2011, DOI: 10.1039/C1CY00056J

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Perspective: MOFs as heterogeneous oxidation catalysts

In this Catalysis Science & Technology perspective, Hermenegildo Garcia and colleagues from the Polytechnic University of Valencia describe the use of MOFs as heterogeneous catalysts for oxidation reactions using hydroperoxides or molecular oxygen.

The authors predict that the field of MOFs as solid catalysts will grow enormously in the near future due to the easy design and synthesis of chiral MOFs.

Read more:

Metal–organic frameworks as heterogeneous catalysts for oxidation reactions
Amarajothi Dhakshinamoorthy, Mercedes Alvaro and Hermenegildo Garcia
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00068C, Perspective

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Tackling pollution; one car at a time. NOx Storage/Reduction catalysts.

While waiting for the golden age of green energy and sustainable, environmentally friendly fuels to arrive, chemical research is focusing on efficient methods to contain the damage caused by the exploitation of fossil fuels. One important issue is reducing the dangerous emissions of automotive and industrial exhausts, which contribute to the production of highly polluting volatile nitrogen oxides.

The review by Liu and Gao, just published in Catalysis Science & Technology explores in detail the NOx storage/reduction process (NSR), one of the three common disposal techniques for nitrogen oxides together with direct decomposition and selective catalytic reduction (SCR). Among these, the direct decomposition suffers from an high activation energy, the SCR process is best suited for stationary sources and very large engines, while NSR was designed for small car engines.

The NSR process works in a stepwise fashion; first the NOx are trapped in the storage component of the NSR catalyst during the lean-burn cycle (high air-to-fuel ratio) to be successively released during the rich burn cycle (low air-to-fuel ratio) and reduced to N2 on the catalyst by hydrocarbons hydrogen and CO produced in the rich cycle. The common catalyst for NSR is generally composed of precious metals, storage components and support metal oxides (Pt/BaO/Al2O3).

In this Minireview a comprehensive description of the mechanisms in operation in each step is presented in detail, together with an explanation of the role of each component and the advantages of different materials and supports.

To know more about the workings of these catalysts, click here.

A review of NOx storage/reduction catalysts: mechanism, materials and degradation studies
Gang Liu and Pu-Xian Gao
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00007A, Minireview

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