Challenge In Catalysis Research Articles

(RSNSW Scholarship Winner 2013) Past and present challenges in catalysis: developing green and sustainable processes.

(RSNSW Scholarship Winner 2013) Past and present challenges in catalysis: developing green and sustainable processes.

Catalyst Enhancement and Recyclability by Immobilization of Metal Complexes onto Graphene Surface by Noncovalent Interactions

The immobilization of a homogeneous catalyst onto a solid surface is one of the major challenges in catalysis, because it may facilitate the separation of the catalyst and the reaction products and may also give rise to the reutilization of the catalyst in multiple subsequent cycles. Noncovalent interactions between the catalyst and the support are arising as interesting alternatives to the more widely used covalent interactions, because they avoid the functionalization of both the catalyst and the surface, which may in turn lead to the modification of the inherent properties of the catalyst. However, some other problems may arise, such as leaching. In this work, we have obtained two complexes containing an N-heterocyclic carbene ligand with a pyrene tag, which we immobilized onto the surface of reduced graphene oxide (rGO), by π-stacking. The catalytic properties of the parent molecular complexes and hybrid materials have been studied in the palladium-catalyzed hydrogenation of alkenes and the ruthenium-...

Insight into the preference mechanism for C[sbnd]C chain formation of C2 oxygenates and the effect of promoters in syngas conversion over Cu-based catalysts

Cu-based catalysts are often used for the production of C2 oxygenates or hydrocarbons from syngas, although numerous studies have been reported, the exact mechanism remains in debate, and presents a major challenge in catalysis. In this study, the preference mechanism for CC chain formation of C2 oxygenates and the role of promoters in syngas conversion on Cu(211) and metal-doped MCu(211) (M=Rh, Ni) surfaces, including CHx (x=1–3) hydrogenation, dissociation and coupling, as well as CO or CHO insertion into CHx (x=1–3), have been systematically investigated by using density functional theory method. Our results show that pure Cu(211) surface shows a better catalytic activity to C2H4 formation rather than C2 oxygenates. However, promoters Rh and Ni-doped Cu(211) surfaces show a better activity and selectivity to C2 oxygenates rather than hydrocarbons, in which CH2 species is responsible for C2 oxygenates formation by CHO insertion. In addition, the difference between CO and CHO insertion into CHx (x=1–3) to form C2 oxygenates is mainly attributed to the HOMO–LUMO gap of CHxCHO and CHxCO, the smaller HOMO–LUMO gap greatly facilitates the charge transfer and hybridization between adsorbed species and catalysts.

Quantitative Comparison of Chiral Catalysts Selectivity and Performance: A Generic Concept Illustrated with Cyclododecanone Monooxygenase as Baeyer–Villiger Biocatalyst

AbstractWithin this work a generic tool for chiral catalyst evaluation is established based on the application‐oriented properties activity and selectivity; the concept aims at quantitatively comparing catalyst performance in general on a multitude of substrates. It is designed and intended to serve as decision guidance for challenges in catalysis and comprehensible information extraction from already recorded but unrefined data sets. The underlying algorithm assigns function points to catalytic entities via a statistically solid model possessing high flexibility and generates a relative ranking. This is coupled to an automated iterative refinement process towards maximum information content of results employing Shannon entropy optimization. Consequently, the developed work‐flow facilitates high distinguishability between catalysts even in low‐scattering data sets. The numerical ranking is complemented by a clearly arranged graphic representation permitting facile and reliable visual interpretation of generality or niche capabilities of catalysts. Usefulness of the title concept is demonstrated by the performance evaluation of cyclododecanone monooxygenase, a highly versatile Baeyer–Villiger enzyme. To retain broad applicability, an open‐source MATLAB® script is provided in electronic form.

Challenges in Catalysis for Pharmaceuticals and Fine Chemicals III

Challenges in Catalysis for Pharmaceuticals and Fine Chemicals III

An Attempt at Enhancing the Regioselective Oxidation of Decane Using Catalysis with Reverse Micelles

The regioselective oxidation of linear alkanes to give terminal oxidation products represents a major challenge for catalysis. A number of previous approaches have shown that confinement and encapsulation can offer an experimentally viable way forward. Against this background we have investigated the use of a system comprising gaseous oxygen, a homogenous catalyst (ammonium metavanadate) confined in an aqueous solution within reverse micelles formed in decane using bis(2-ethylhexyl)sulfosuccinate. At low conversion and at short reaction times we show that the approach does lead to a small enhancement in the selectivity to terminal products, but unsurprisingly the surfactant is more readily oxidised than decane and so the small positive effects of the micellar catalyst system are short-lived.

Probing the Origin of the Metabolic Precursor of the CO Ligand in the Catalytic Center of [NiFe] Hydrogenase

The O(2)-tolerant [NiFe] hydrogenases of Ralstonia eutropha are capable of H(2) conversion in the presence of ambient O(2). Oxygen represents not only a challenge for catalysis but also for the complex assembling process of the [NiFe] active site. Apart from nickel and iron, the catalytic center contains unusual diatomic ligands, namely two cyanides (CN(-)) and one carbon monoxide (CO), which are coordinated to the iron. One of the open questions of the maturation process concerns the origin and biosynthesis of the CO group. Isotope labeling in combination with infrared spectroscopy revealed that externally supplied gaseous (13)CO serves as precursor of the carbonyl group of the regulatory [NiFe] hydrogenase in R. eutropha. Corresponding (13)CO titration experiments showed that a concentration 130-fold higher than ambient CO (0.1 ppmv) caused a 50% labeling of the carbonyl ligand in the [NiFe] hydrogenase, leading to the conclusion that the carbonyl ligand originates from an intracellular metabolite. A novel setup allowed us to the study effects of CO depletion on maturation in vivo. Upon induction of CO depletion by addition of the CO scavenger PdCl(2), cells cultivated on H(2), CO(2), and O(2) showed severe growth retardation at low cell concentrations, which was on the basis of partially arrested hydrogenase maturation, leading to reduced hydrogenase activity. This suggests gaseous CO as a metabolic precursor under these conditions. The addition of PdCl(2) to cells cultivated heterotrophically on organic substrates had no effect on hydrogenase maturation. These results indicate at least two different pathways for biosynthesis of the CO ligand of [NiFe] hydrogenase.

The monoanionic pincer–metal platform: a scaffold for meeting challenges in catalysis and materials research

A graphical abstract is available for this content

Water-gas shift reaction on oxide/Cu(111): Rational catalyst screening from density functional theory

Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide∕Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO∕Cu(111) < TiO(2)∕Cu(111), ZrO(2)∕Cu(111) < MoO(3)∕Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide∕Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

Studies of Precious Metal Catalysts in the CARMAC Programme

One of the recurrent challenges in catalysis is how to ensure that the right reactions take place. In a recent collaborative programme between academic and industrial partners, some of the key issues relating to reactant specificity and product selectivity in liquid and gas media have been tackled using a combination of computational modelling, catalyst chemistry and chemical engineering. As well as providing solutions to several real-life problems from the chemical manufacturing industry, essential skills required for in situ studies have been established within the academic centres during the course of the programme. These developing skills are intended to have an ongoing impact on the understanding and application of complex multiphase processes, in which platinum group metals and other precious metals are often present as catalysts.

Is a renaissance of coal imminent?—challenges for catalysis

In the introduction, the reserves and resources of coal and other fossil fuels are discussed, also with regard to the regional distribution and consumption. Then, coalification and the classification of coal are described. The main part of the article is devoted to the most important processes using coal where challenges for catalysis still exist, with a focus on recent literature. First, technologies based on the production of synthesis gas, i.e., Fischer-Tropsch synthesis as well as MTO/MTP (Methanol To Olefins/Methanol To Propylene), are discussed. Secondly, direct coal liquefaction is treated. The last part of the article is devoted to "clean" coal and gives an outlook on the future of coal.

Metal–Organic Frameworks: Opportunities for Catalysis

The role of metal-organic frameworks (MOFs) in the field of catalysis is discussed, and special focus is placed on their assets and limits in light of current challenges in catalysis and green chemistry. Their structural and dynamic features are presented in terms of catalytic functions along with how MOFs can be designed to bridge the gap between zeolites and enzymes. The contributions of MOFs to the field of catalysis are comprehensively reviewed and a list of catalytic candidates is given. The subject is presented from a multidisciplinary point of view covering solid-state chemistry, materials science, and catalysis.

Challenges in Catalysis for Pharmaceuticals and Fine Chemicals

Challenges in Catalysis for Pharmaceuticals and Fine Chemicals

The kinetics of homogeneous catalytic methane oxidation

Selective, direct oxidation of methane into useful chemicals remains a big challenge in catalysis in the 21st century. The study presents a new and efficient method based on methane esterification and further hydrolysis to methanol. A platinum-catalyzed system using oleum as the reaction medium for the oxidation of methane to methyl bisulfate in the temperature range between 140 and 180 °C at methane pressure 3.0–6.8 MPa has been studied. Analyzing the relationship between the ester concentration and the methane partial pressure, the sulfur trioxide concentration and the temperature, leads to a well-defined equation describing the reaction rate. This equation is applicable for the estimation of the reaction rate and the ester concentration in any moment up to a process time of 22 h. An apparent activation energy is also calculated.

Direct conversion of methane into oxygenates

Direct conversion of methane into useful chemicals remains as a big challenge in catalysis in the 21st century. A large number of studies have contributed to the direct conversion of methane in the past decade. Although there is still no direct process with commercial viability at this moment, many new methods and catalysts have been developed for the direct activation and conversion of methane. This review highlights the recent novel approaches to the partial oxidation of methane into useful oxygenates with an emphasis on the selective formation of methanol in the presence of H 2.

00/03167 Synthetic or reformulated fuels: a challenge for catalysis

00/03167 Synthetic or reformulated fuels: a challenge for catalysis

Synthetic Or Reformulated Fuels: a Challenge for Catalysis

Despite comparative figures for wordwide crude oil and natural gas proven reserves, present time contribution of syngas chemistry to motorfuels remains marginal when the refining industry is faced to main constraints: market demand evolution, stringent specifications and environmental issues. Actually natural gas upgrading via syngas chemistry yields key products (e. g. methanol) among which clean motorfuels (ethers, FT products) should develop despite the huge investments required, mostly for syngas production. Main challenges and corresponding issues for catalysts and related technologies are identified for Fischer-Tropsch synthesis and motorfuels long-term reformulation. Among other, mastering the chain-growth (FT synthesis) improving the FCC products: gasoline, and LCO for Diesel pool. All these issues need significant progresses in catalyst and technology to be solved. Lastly, our economical study, focused on Diesel-fuel production, shows up that clean diesel (from SR-LCO mixtures) and FT Diesel reach similar production costs when cheap NG is available. In the future, FT middle distillates should amount to a few percent (5-150 Mt) of the 1700-2000 Mt of transport middle distillates expected from oil refining. However they should more and more be a compulsory part of diesel pool if the level of investment for an FT process continues to decrease significantly.

ChemInform Abstract: Stereoselectivity. The Ultimate Challenge in Catalysis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New Patents

Johnson Matthey Catalysis and Chiral Technologies, Orchard Road, Royston, Hertfordshire SG8 5HE, UK; E-mail: fabrizio.nerozzi@matthey.com On 20th October 2009 around 100 delegates from the chemical industry and academia met in London, UK, for the second meeting on “Challenges in Catalysis for Pharmaceuticals and Fine Chemicals”.The event was organised jointly by the Society of Chemical Industry Fine Chemicals Group and the Royal Society of Chemistry Applied Catalysis Group. It followed the very successful first event that took place in 2007 and was reviewed in this Journal (1). Topics covered included: the latest developments in coupling redox processes for carbon–carbon bond formation; cross-coupling reactions; nitrile hydrogenation; organocatalysis; amide bond formation by catalysis; and novel techniques for development of catalysed reactions. Like its predecessor, this meeting also focused on one of the principles of ‘green chemistry’: in this case, finding ways of minimising chemical waste by choosing those reagents and catalysts that produce the most atom-efficient processes. A series of seven oral presentations from speakers representing British and international academic institutions and the pharmaceutical industry was supported by a poster display during lunch. John Birtill (Consultant in Catalyst Technology, UK) of the RSC Applied Catalysis Group made the closing remarks. The following is a brief review of the research work on platinum group metal (pgm)-catalysed reactions presented at the meeting.