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Photosynthesis inspired photoreactor

17 May 2011

Scientists from China have developed a way to intensify photocatalytic processes, and they have utilised it for efficient photoreactor design.

Currently, photocatalysis has few commercial or industrial applications because of the complex configuration of the photoreactor that would be required, and thus difficult engineering and scale-up issues. However, Zhuhong Yang and co-workers from Nanjing University of Technology, China have developed a new photoreactor design which separates the process into two parts and has been inspired by photosynthesis in plants.

Photosynthesis can be considered as a tandem reaction consisting of the light reaction and the dark reaction. In the reactor designed by Yang, the first part of the reactor is the heterogeneous reaction, where surface-bound radical species are generated (the ‘light’ reaction) and the second part is the homogeneous reaction mediated by the radicals generated in part one (the ‘dark’ reaction). The team used a static mixer which greatly improved the overall efficiency of the reaction by increasing radical mobility in the solution.

By separating the illumination and mixing parts of the photoreactor, scale-up and engineering applications will be made much easier.

For more information, please see the full article, free to read until 13th June:

Photosynthesis-inspired design approach of a liquid phase heterogeneous photoreactor, Dong Li, Kui Xiong, Kangzhong Shi, Zhuhong Yang, Chang Liu, Xin Feng and Xiaohua Lu, Green Chem., 2011, DOI: 10.1039/C1GC15082K.

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Hydrogen storage and release: a recyclable system

01 Apr 2011

Scientists from Germany have reported a simple and robust ionic liquid-based system for the selective decomposition of formic acid to hydrogen and carbon dioxide.

Formic acid has been proposed as an attractive hydrogen carrier substance as it can easily be stored and transported to be catalytically decomposed to release hydrogen (and CO₂) on demand. Wasserscheid and his team have developed a simple and robust catalytic system involving the ionic liquid [EMMIM][OAc] and the ruthenium catalyst RuCl₃ which gave excellent yields of hydrogen from formic acid. As ionic liquids have extremely low volatility, this avoids solvent contamination of the produced hydrogen stream. In addition, the system is very selective, with no carbon monoxide form during the decomposition, thereby avoiding complicated gas purification procedures later on.

However, one of the most striking features of the system reported by Wasserscheid is the recyclability of this ionic liquid-catalyst system. The RuCl₃/[EMMIM][OAc] could was reused for at least another nine runs after its first use, with no decline in the selectivity or yields, illustrating the robust nature of this system. This has clear implications for further development of this process and its application in industry.

To read more please see link below for the full journal article. This article will be free to access until 2 May 2011.

Simple and recyclable ionic liquid based system for the selective decomposition of formic acid to hydrogen and carbon dioxide

M. E. M. Berger, D. Assenbaum, N. Taccardi, E. Spiecker and P. Wasserscheid, Green Chem., 2011, DOI: 10.1039/C0GC00829J,

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Processing of metals and metal oxides using ionic liquids – a review

16 Feb 2011

Andrew Abbott and co-workers at the University of Leicester have reviewed the use of ionic liquids for the processing of metals and metal oxides.

Processing of metals and metal oxides using ionic liquids

The processing and reprocessing of metals is possibly one of the largest energy consumers and generators of waste in the industry sector. Typically, metal extract and recovery (also known as hydrometallurgy) in solution is done in melts or very basic or acidic solutions, as metal oxides are insoluble in most molecular solvents. However, these methods have disadvantages due to their high energy demands, the amount of waste generated, and the numerous steps involved.

Ionic liquids, salts which are liquid below 100 °C, possess useful physical properties which allow them to be applied to many different reactions and processes. In this case, some ionic liquids have demonstrated much higher solubilities for metal salts than most organic solvents. Potential advantages of using ionic liquids in this field include the ability to simplify processing techniques and avoid the formation of oxide and hydroxide products during processing.

In this review Abbott and co-workers critically review the potential efficacy of ionic liquids in metal and metal oxide processing over existing methods.

This article is freely available until the 16 March 2011:

Processing of metals and metal oxides using ionic liquids, Andrew P. Abbott, Gero Frisch, Jennifer Hartley and Karl S. Ryder, Green Chem., 2011, DOI: 10.1039/C0GC00716A.

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Switchable solvents

10 Feb 2011

Philip Jessop and co-workers report tertiary amine solvents with switchable-hydrophilicity which have been applied to recycling polystyrene foam.

These switchable-hydrophilicity solvents (SHS) have very low miscibility with water and air, but are completely miscible in the presence of a CO₂ atmosphere. Jessop and his team had previously reported using N,N,N’-tributylpentanamidine as a SHS which could easily be removed from organic products. However, N,N,N’-tributylpentanamidine is very difficult to synthesise and is not commercially available.

Switchable solvents

In this work, Jessop reports the use of several tertiary amines which are either commercially available or easily prepared. As well as investigating the factors which affect the rate of switching, the group also applied one of the amines studied to the recycling of polystyrene foam. The polystyrene foam was dissolved in one of the SHSs, and after addition of carbonated water formed dense polystyrene. In future, this could potentially make the transportation and recycling of polystyrene foam waste less energy intensive and more efficient.

Access this article for free by clicking on the link below:

Tertiary amine solvents having switchable hydrophilicity

Philip G. Jessop, Lisa Kozycz, Zahra Ghoshouni Rahami, Dylan Schoenmakers, Alaina R. Boyd, Dominik Wechsler and Amy M. Holland, Green Chem., 2011, DOI: 10.1039/C0GC00806K

For a related article, please see:

A solvent having switchable hydrophilicity
Philip G. Jessop, Lam Phan, Andrew Carrier, Shona Robinson, Christoph J. Dürr and Jitendra R. Harjani, Green Chem., 2010, 12, 809-814
DOI: 10.1039/B926885E

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