Archive for April, 2013

A Green Cocktail for the Industrial Synthesis of Lactic acid

Posted on behalf of Shreesha Bhat

Lactic acid is a versatile chemical having wide applications in food, cosmetics and chemical industry. They are generally prepared by acid catalyzed reactions of hexoses and trioses, and one such triose i.e. glycerol has been found to be produced in surplus amounts as byproducts in production of biodiesel. Glycerol offers great potential to be used as a renewable feedstock for the production of various value-added products like lactic acid.

So far, base catalysts have not been explored for this purpose, except for the hydrothermal conversion of glycerol to lactic acid using alkali metal catalysts like NaOH/KOH. This method presents several drawbacks for the industrial synthesis like harsh reaction conditions (excess temperature, excess amount of strong base, etc.) and cost-intensive isolation of soluble alkali metal lactates (excess catalysts) which is highly uneconomical. As a solution to this problem, scientists at Graz University of Technology, Austria have come up with a “green” method for the industrial synthesis of lactic acid by mixing a cocktail of dihydroxyacetone and calcium hydroxide.

Glycerol to lactic acid

The sparingly soluble calcium hydroxide facilitates the easy removal of excess catalyst by simple mechanical filtration making this a highly economical and industrial friendly method. Another component of the cocktail Dihydroxyacetone– is easily obtained by the microbial oxidation of glycerol in high yields, thus reducing the glycerol burden in the biodiesel industry.

The present paper discusses the catalytic effects of various earth metal hydroxides like barium hydroxide, calcium hydroxide and magnesium hydroxide on the lactic acid formation from dihydroxyacetone. The screening studies indicate that calcium hydroxide is highly selective towards formation of lactic acid owing to its chelation properties. The intriguing mechanism of lactic acid formation by alkali earth metal catalysis was investigated by the means of mechanistic and kinetic studies which suggested two major pathways for lactate synthesis. It was found that the temperature differences play an important role in the preference of the reaction to proceed via either pathway. Various other studies like the effect of concentration of catalyst, feed concentration, temperature variations provide a detailed insight into the synthesis of lactic acid from dihydroxyacetone.

The extensive studies done by the Austrian scientists, has not only provided a potential solution to the enigmatic problem of industrial synthesis of lactic acid, but has also provided a way to recycle the surplus glycerol into a high value product like lactic acid.

To know how the green cocktail made its way to become an industrially feasible method for the synthesis of lactic acid, read the article:

Synthesis of lactic acid from dihydroxyacetone: use of alkaline earth-metal hydroxides
Susanne Lux and Matthäus Siebenhofer
Catal. Sci. Technol., 2013, DOI: 10.1039/c3cy20859a

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Platinum ‘peanuts’ to make better fuel cells

Sara Coles is a guest web-writer for Catalysis Science & Technology. She currently works for Johnson Matthey in Royston, UK.

Shape controlled synthesis of catalytically active metal nanostructures is an important field of scientific research for both industry and academia. The arrangement of atoms on the particle surface is believed to play a critical role in the adsorption and desorption of substrates and products – which in turn affects the activity and selectivity of the catalyst. The chance to fine-tune these properties is too good to miss.

With this aim in mind, Sourov Ghosh and colleague, working in India, have experimented with different ways to shape platinum nanoparticles. Their report in Catalysis Science & Technology explains how they Platinum peanut shaped nanoparticles performing hydrogenation and oxygen reductionmade and characterised ‘peanut-like’ and ‘dendrimer-like’ platinum nanoparticles to compare their performance in the hydrogenation of unsaturated alcohols and, supported on carbon nanotubes, in the oxygen reduction reaction (ORR).

The peanut-like particles showed significantly higher specific activity towards the ORR than the aggregated dendrimer-like particles or conventional quasispherical platinum nanoparticles. This makes them a promising choice for the fuel cell cathode due to their ability to promote faster electron transfer kinetics.

Read more about this work in the full paper.

Shape-controlled synthesis of Pt nanostructures and evaluation of catalytic and electrocatalytic performance
Sourov Ghosh and C. Retna Raj
Catal. Sci. Technol., 2013, 3, 1078, DOI: 10.1039/c2cy20652h

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Top ten most accessed articles in February

This month sees the following articles in Catalysis Science & Technology that are in the top ten most accessed:-

Nickel nanoparticles catalyse reversible hydration of carbon dioxide for mineralization carbon capture and storage 
Gaurav A. Bhaduria and Lidija Šiller 
Catal. Sci. Technol., 2013,3, 1234-1239 
DOI: 10.1039/C3CY20791A  

Graphene-based materials for catalysis 
Bruno F. Machadoab and Philippe Serp 
Catal. Sci. Technol., 2012,2, 54-75 
DOI: 10.1039/C1CY00361E  

Advances in conversion of hemicellulosic biomass to furfural and upgrading to biofuels 
Saikat Dutta, Sudipta De, Basudeb Saha and Md. Imteyaz Alam 
Catal. Sci. Technol., 2012,2, 2025-2036 
DOI: 10.1039/C2CY20235B  

Functional group dependence of the acid catalyzed ring opening of biomass derived furan rings: an experimental and theoretical study 
Christopher R. Waidmann, Aaron W. Pierpont, Enrique R. Batista, John C. Gordon, Richard L. Martin, L. A. “Pete” Silks, Ryan M. Westd and Ruilian Wu 
Catal. Sci. Technol., 2013,3, 106-115 
DOI: 10.1039/C2CY20395B  

High CO2 and CO conversion to hydrocarbons using bridged Fe nanoparticles on carbon nanotubes 
Justin P. O’Byrne, Rhodri E. Owen, Daniel R. Minett, Sofia I. Pascu, Pawel K. Plucinski, Matthew D. Jones and Davide Mattia 
Catal. Sci. Technol., 2013,3, 1202-1207 
DOI: 10.1039/C3CY20854K  

Emerging catalytic processes for the production of adipic acid 
Stijn Van de Vyvera and Yuriy Román-Leshkov 
Catal. Sci. Technol., 2013, Advance Article 
DOI: 10.1039/C3CY20728E  

Direct C–H bond arylations and alkenylations with phenol-derived fluorine-free electrophiles 
Sergei I. Kozhushkov, Harish Kumar Potukuchia and Lutz Ackermann 
Catal. Sci. Technol., 2013,3, 562-571 
DOI: 10.1039/C2CY20505J  

Role of mixed metal oxides in catalysis science—versatile applications in organic synthesis 
Manoj B. Gawande, Rajesh K. Pandeyb and Radha V. Jayaram 
Catal. Sci. Technol., 2012,2, 1113-1125 
DOI: 10.1039/C2CY00490A  

Metal–organic frameworks as catalysts: the role of metal active sites 
Pieterjan Valvekens, Frederik Vermoortelea and Dirk De Vos 
Catal. Sci. Technol., 2013, Advance Article 
DOI: 10.1039/C3CY20813C  

Metal–organic frameworks as heterogeneous catalysts for oxidation reactions 
Amarajothi Dhakshinamoorthy, Mercedes Alvaroa and Hermenegildo Garcia 
Catal. Sci. Technol., 2011,1, 856-867 
DOI: 10.1039/C1CY00068C   

Why not take a look at the articles today and blog your thoughts and comments below.

Fancy submitting an article to Catalysis Science & Technology ? Then why not submit to us today or alternatively email us your suggestions.

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A Fine Catalysis Meeting in Sicily

The second “FineCat – Symposium on heterogeneous catalysis for fine chemicals” was held in Palermo, Italy, on April 10-11, 2013. With delegates coming from all over the world, it was two intense days of lectures and poster presentations. Some of the topics covered included biomass conversion, flow chemistry, catalysis with metal nanoparticles, heterogeneous photocatalysis and doped hybrid silicas. A poster prize was also offered, which Natcha Wongpraphairoat from Chulalongkorn University, Thailand, won with her poster on the the catalytic conversion of glycerol to propylene glycol over supported copper/ZnO catalysts.

To find out more about the conference, a more detailed report can be found here, or you can download the conference report in pdf.

Next year’s conference will be held Sicily on April 9-10, 2014, with further details here. So if you are interested in catalysis, why not consider a working holiday in Sicily next year?

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Green synthesis of polyurea with microwaves

Polyureas, which contain the –NHCONH– unit in their backbone, have a wide variety of uses, such as in foams, fibres and biomedical applications. Traditionally, they are made via a process that uses toxic carbonylating agents such as phosgene or isocyanate, and the by-products of the reaction are also hard to recycle. Needless to say, it would be desirable to produce polyureas by a more environmentally friendly method.

In this paper, the authors report one such technique. They have synthesised a polyurea, [6]-oligourea, with a microwave assisted method that uses a green carbonylating agent and an organocatalyst. After optimising the experimental conditions, they found that with 10W of fixed-mode microwave energy applied to the reactants, they were able to achieve almost 100% yield. The by-products of the reaction are also more easily recycled than from traditional methods.

This synthetic method opens the way to producing polyureas in a eco-friendly, efficient way.

Highly efficient isocyanate-free microwave-assisted synthesis of [6]-oligourea

Read their paper to find out more:

Highly efficient isocyanate-free microwave-assisted synthesis of [6]-oligourea
Abdussalam K. Qaroush, Asmaa S. Al-Hamayda, Yasmeen K. Khashman, Sergei I. Vagin, Carsten Troll and Bernhard Rieger
Catal. Sci. Technol., 2013, Advance Article
DOI: 10.1039/C3CY00117B, Paper

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Cleaner diesel engines – not just a pipe dream!

Selective catalytic reduction (SCR) to date presents the most promising deNOx technology for diesel engines.  Removal of NOx from diesel exhaust is problematic due to the wide temperature range (373–923 K) at which diesel engines operate.  This is due to inefficient conversion at low temperature (below 423 K) with the commonly used ionic exchanged zeolites or low selectivity to N2 with supported MnOx catalysts.

In this HOT article, Tanaka et al. found that the temperature had a significant effect on the photocatalytic reactions in the gas phase over a TiO2 photocatalyst with a maximum conversion of 84% (at GHSV 100,000 h-1 and 433 K).  The amount of NH3 at high temperature was found to be key to a high NO conversion.  The results provide evidence of the potential practicality of the use of photo-SCR for diesel engines.

Effects of reaction temperature on photocatalytic activity

Effects of reaction temperature on photocatalytic activity

Read more about these developments in photocatalysis by downloading the article now:

Effects of reaction temperature on the photocatalytic activity of photo-SCR of NO with NH3 over a TiO2 photocatalyst
Akira Yamamoto, Yuto Mizuno, Kentaro Teramura, Tetsuya Shishido and Tsunehiro Tanaka
Catal. Sci. Technol., 2013, Advance Article
DOI: 10.1039/C3CY00022B

This article is part of a themed issue on photocatalysis that is due to be published later this year.

You may also be interested in a perspective recently published by the same author on the subject:

A unique photo-activation mechanism by “in situ doping” for photo-assisted selective NO reduction with ammonia over TiO2 and photooxidation of alcohols over Nb2O5
Tetsuya Shishido, Kentaro Teramura and Tsunehiro Tanaka
Catal. Sci. Technol., 2011, 1, 541-551
DOI: 10.1039/C1CY00104C, Perspective

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Tannins help in biphasic catalysis

There are pros and cons to both homogeneous and heterogeneous catalytic strategies. One way to get the best of both worlds is to use aqueous-organic biphasic catalysis. This approach hasn’t been widely utilised so far due to interfacial resistance between the phases which causes a low catalytic activity.

Researchers in China have overcome this by using tannins from Black Wattle (an acacia tree species). The tannins “amphiphilicly” stabilise catalytic palladium nanoparticles enabling them to catalyse reactions in the organic phase whilst remaining in the aqueous phase for subsequent re-use, without loss of activity.

Read the full article here:

Using plant tannin as natural amphiphilic stabilizer to construct aqueous-organic biphasic system for highly active and selective hydrogenation of quinoline
Hui Mao, Jun Ma, Yang Liao, Shilin Zhao and Xuepin Liao
Catal. Sci. Technol., 2013, DOI:10.1039/C3CY00108C

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Improving photocatalytic properties of titanium oxide with a new doping method

TiO2 nanotubes demonstrate photocatalytic properties that make them useful in applications such as decomposition of organic pollutants. These nanotubes are commonly grown in an anodization process that takes place in an electrolytic bath, with dopants, which are used to modify the catalytic properties of the nanotubes, added at a later stage.

In this paper, Hahn and co-workers have demonstrated a new growth method in which the desired dopants are dissolved in the electrolyte solution. The nanotubes grown from this solution incorporate the dopants, and no further treatment is required. A test of the photocatalytic properties of the nanotubes also confirms that it behaves very similar to nanotubes grown by conventional methods. This fast and convenient way of manufacturing doped TiO2 nanotubes opens the route to many potential future applications.

 Photocatalytic properties of in situ doped TiO2-nanotubes grown by rapid breakdown anodization

Find out more by reading the full article:

Photocatalytic properties of in situ doped TiO2-nanotubes grown by rapid breakdown anodization
Robert Hahn, Martin Stark, Manuela Sonja Killian and Patrik Schmuki
Catal. Sci. Technol., 2013, Advance Article
DOI: 10.1039/C3CY00021D

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Metal oxide films as water oxidation catalysts

Since hydrogen represents an alternative energy source to carbon-based fuel, there is a need to be able to split water using water oxidation catalysts (WOC) preferably by renewable energy sources such as sunlight.  In this HOT article, the Spiccia group present a facile preparation of NiOx films for use as WOC.  These WOC films, deposited from macrocyclic Ni complexes in alkaline solution, were significantly more catalytically active at higher pH (12.9), therefore widening the range of conditions over which they can be deposited.  Enhanced catalytic activity was also observed in visible light, indicating the films are electrochromic.

Metal films as water oxidation catalysts

To learn more about these catalytic metal oxide films download the full paper now:

Anodic deposition of NiOx water oxidation catalysts from macrocyclic nickel(II) complexes
Archana Singh,  Shery L. Y. Chang,  Rosalie K. Hocking,  Udo Bach and Leone Spiccia
Catal. Sci. Technol., 2013, Advance Article
DOI: 10.1039/C3CY00017F

This article is part of a themed issue on photocatalysis that is due to be published later this year.

You may also be interested in:
Highly active nickel oxide water oxidation catalysts deposited from molecular complexes
Archana Singh, Shery L. Y. Chang, Rosalie K. Hocking, Udo Bach and Leone Spiccia
Energy Environ. Sci., 2013, 6, 579-586
DOI: 10.1039/C2EE23862D

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