Dr Jamie Humphrey, Catalysis Science & Technology‘s Managing Editor, will be attending the North American Catalysis Society meeting next week in Detroit.
If you’d like to meet up with Jamie while he is there, please contact us.
To see which other conferences the team will be attending visit our earlier blog post…
Pollutants enter the ecosystem through several pathways. Dangerous substances are released into the atmosphere in many ways, for instance by car exhausts, from industrial fumes and drainage effluents and through degradation of pesticides to name but a few.
A contaminant that appears to be ubiquitous and released through all these pathways is phenol. Phenols are highly toxic by inhalation, causing lung edema, through ingestion, damaging kindneys, brain and liver, and it is also an extreme irritant to the skin, causing severe burns. Some phenols are reported carcinogens.
Degrading and removing phenols from contaminated water is essential before allowing it to enter the ecosystem. Many techniques have been developed and applied in order to do this, such as the use of polymeric resins, microbial or enzymatic degradation, adsorption and other catalytic chemical transformations.
A recently published work by Yao, Shi and Sui focused on the latter.
The group focused on the use of supported titania for the photocatalytic degradation of phenols under UV light in aqueous solutions. The catalyst was prepared by anchoring TiO2 onto fly ash deriving from municipal waste combustion: a less usual support compared to the more widespread silica, alumina and zeolites.
The fly ash was treated with acid, washed and dried before the titanium oxide coating was applied as a sol-gel and the material calcinated. Several calcination temperatures were tested, finding that 500 °C provided the ideal condition to obtain high degree of crystallinity in the catalyst.
The catalytic loading was also explored in the range 10-30 g/L to determine the highest concentration achievable without preventing light from reaching the bulk of the solution; the catalyst also proved robust and reusable, retaining 90% of its photocatalytic activity even after 4 cycles. Several tests were peformed to ensure that the activity of the system was due to the photocatalyst, including test runs with untreated fly ash, only titania and UV irradiation alone.
To better understand the characteristics of the system, a kinetic study of the degradation reaction was also performed, revealing a first order-like behaviour; also, a three-step mechanism for the fly ash-supported catalyst was proposed.
Using the optimal conditions found during the study, the group achieved 94 % of phenol degradation with a catalyst loading of 20 g/L over 4 hours of irradiation, which, with its reusability, could make the catalyst potentially employable for continuous use in water treatment.
Read more about this catalyst here.
Application of fly ash supported titanium dioxide for phenol photodegradation in aqueous solution
Zhongliang Shi, Shuhua Yao and Chengcheng Sui
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00019E
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
It is a fact that the world’s reservoirs of conventional oil are diminishing at a fast pace, forcing mankind to look for alternatives – possibly cleaner, sustainable and more environmentally friendly than fossil fuels.
While the technologies to exploit renewable sources of energy, like wind, tidal or solar power, mature to the point of replacing old-fashioned sources of energy, the use of sustainable fuels may bridge the gap between us and a greener future.
Biodiesel, a mixture of methyl esters of fatty acids, is an alternative to normal diesel that burns producing consistently less greenhouse gases and sulphurated compounds. Biodiesel can be produced via trans-esterification of vegetable or animal oils with methanol generally under acidic conditions; however, the process is as yet not cost-competitive with conventional diesel fuel.
A way to reduce costs is to use cheaper oils, containing free, unesterified fatty acids in the production process introducing an extra esterification step in the process.
Lingaiah et al., in a recently published paper, presented their work on a solid-phase catalyst for the acidic conversion of fatty acids into their correspondent methyl esters that simultaneously catalyses trans-esterification, avoiding the need for a separate reaction.
To provide the necessary acidity, the group employed 12-tungstophosphoric acid (TPA), a heteropolyacid, supported on tin oxide to increase its thermal stability and to reduce catalyst leakage in the reaction media. A full study of the effect of parameters like TPA loading, reaction temperature, stirring speed and catalyst concentration resulted in and optimised TPA loading of 15 wt% to provide ideal surface area and acidity.
The activity test were performed using palmitic acid as the model substrate at 65 °C with a total catalyst loading of 25%, in the presence of an excess of methanol (1:14) to improve conversion (since the esterification is a reversible reaction). After 4 hours, the palmitic acid conversion reached exceeded 70%, and tests showed the catalyst could be washed and reused 5 times without significant loss of activity.
To prove its industrial viability, simultaneous esterification/trans-esterfication in the presence of mixtures of triglycerides and free fatty acids was successfully performed.
Read the full paper here.
Efficient solid acid catalysts for esterification of free fatty acids with methanol for the production of biodiesel
K. Srilatha, Ch. Ramesh Kumar, B. L. A. Prabhavathi Devi, R. B. N. Prasad, P. S. Sai Prasad and N. Lingaiah
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00085C, Paper
The population of Earth is rising day by day, forcing agriculture to boost its production through the use of GM crops, the exploitment of new plant species for human consumption and, more traditionally, by employing increasingly large amounts of fertilizers (see the EFMA EU trend here).
Most of the commonly used fertilizers are sources of phosphate and nitrate ions that if used constantly can percolate through soil and contaminate groundwater and eventually affect the quality of drinking water.
Following the WHO guidelines reviewed in 2003, the maximum limit of nitrate in drinking water is set at 5omg/Litre and a maximum of 3mg/L for nitrite for short term exposure. The main consequences of exposure to higher doses of nitrate and nitrite are methaemoglobinaemia (conversion of hameoglobulin into methaemoglobulin, unable to carry oxygen) and morphological changes in the adrenal glands, lungs and heart (in animal models).
Ion exchange and chlorination, two common water denitrification processes are unable to efficiently remove nitrite due to its solubility and other processes produce a number of undesired toxic products like nitrite and ammonia.
Mishra et al., in a study presented in Catalysis Science and Technology proposed a preliminary but encouraging process to photocatalitically convert nitrate in nitrogen gas with minimal production of side-products.
In the first application in this field, tungsten and nitrogen doped titania was used in association with formic acid (a hole scavenger that increase the rate of reduction) for the reduction of nitrate with visible light produced by a high pressure Hg vapour lamp. After several studies on the ideal combination of doping agents and manufacturing conditions, the group found that a 2% of tungsten yielded the most active form of the catalyst (although larger percentages of the metal increased the absorption in the visible region).
Testing of the material for activity unveiled a selectivity for nitrogen gas of around 95% in contrast with just 50% obtained when tungsten wasn`t incorporated into the catalyst. To mimic potential real-life application, the tests were performed in air and also in the presence of chloride anions, the effect of which appeared to be overall beneficial to the reaction.
A discussion of the factors determining the activity of the system pointed out the importance of the exact combination of doping, hole scavenger, morphology of the material, mesoporosity and the presence of hydroxyl groups on the surface.
The characteristics of the material could make it a good candidate for a solar light-powered version of the process.
Mesoporous WN co-doped titania nanomaterial with enhanced photocatalytic aqueous nitrate removal activity under visible light
T. Mishra, M. Mahato, Noor Aman, J. N. Patel and R. K. Sahu
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00042J, Paper
Nitrogen oxides are among the most harmful pollutants produced by the combustion of fossil fuels, cause of euthropication of waters and soil contamination.
The reduction of the release of these nitrogen oxides from industrial flue gases and diesel engines into the atmosphere is more than ever a hot topic, as testified by the increasing amount of scientific publications on NOx storage and disposal; some of which appeared in Catalysis Science and Technology last month (here and here, also reviewed in this blog).
One of the main strategies to convert these oxides into harmless product is the Selective Catalytic Reduction (SCR) that takes place on supported catalysts like those found in exhausts pipes of modern cars. Due to the presence of alkaline metals in biomass derived and fossil fuels that can poison and deactivate them , though, the activity of these catalysts decreases with time; metals like potassium and barium affect the Brønsted acid sites of the catalysts and prevent the ammonia adsorbtion process, essential in the functioning of the system.
A new study by the Danish research group lead by Rasmus Fehrmann addresses this weakness and proposes a possible improvement to the process; the group postulated that in the presence of a super-acidic support for the catalyst, the alkali would preferentially react with the support, leaving the catalytic species untouched.
The super-acid of choice was a member of the heteropoly acids family, a class of solid acids composed of clusters of hydrogen, oxigen and transition metals coordinated around elements of the p-block like silicon, phosphorus or arsenic.
The chosen heteropoly acids, among which the 12-tungstophoshporic acid (TPA), were added to the titanium oxide support in conjunction with V2O6 as the active catalyst and tested in the NH3 promoted SCR. Traditional V2O6/TiO2 and mixed V2O6-WO3/TiO2 catalysts were used as a reference during the activity tests.
After doping with a source of potassium, the catalysts were tested against their pristine counterparts to measure the difference in activity, resulting in a superior performance of the super-acid supports which retained up to 88% of the original activity compared to 33% of the untreated ones.
Find out about these promising catalysts here.
Heteropoly acid promoted V2O5/TiO2 catalysts for NO abatement with ammonia in alkali containing flue gases
Siva Sankar Reddy Putluru, Anker Degn Jensen, Anders Riisager and Rasmus Fehrmann
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00081K, Paper
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
Last week we heard some exciting news in the Catalysis Science & Technology Editorial Office.
Our new journal has been accepted for indexing in Scopus, outside of the regular evaluation procedures, because it was considered as a “must-have” for the Scopus database. Our contact at Scopus tells us that in some exceptional cases journals receive this priority treatment.
The very positive endorsement comes just as we are about to publish online the second issue of the journal – keep a look out for it, or sign up for the journal’s e-alerts.
In this Catalysis Science & Technology PERSPECTIVE, David Glueck examines several examples of structure–selectivity relationships with the eventual goal of designing substrates for positive cooperativity and enhanced selectivity in asymmetric catalysis. This kind of systematic investigation hopefully is the way forward to rationally improve selectivity.
Read more at:
Selectivity via catalyst or substrate control in catalytic asymmetric transformations of bifunctional symmetrical substrates
Catal. Sci. Technol., 2011, Advance Article
DOI: 10.1039/C1CY00048A, Perspective
Designing substrates for positive cooperativity and enhanced selectivity in asymmetric catalysis
Last week in Anaheim, during the ACS Spring National Meeting, we celebrated the launch of Catalysis Science & Technology.
To a packed audience, Associate Editor Professor Paul Chirik introduced the journal, explaining the ever increasing importance of catalysis to address the global challenges we face today. Catalysis Science & Technology was launched to bring together the best catalysis research, from heterogeneous, homogeneous and biocatalysis, in one journal, owned and published by a society publisher.
Associate Editor Paul Chirik (Princeton University)
At the end of the evening, a prize draw took place, to win an ipod nano. Congratulations to Dr Andrew Dove (University of Warwick, UK), who won the prize!
Issue One of Catalysis Science & Technology is available free online. Take a look today!
Celebrating Catalysis Science & Technology
