Catalysis Science & Technology Blog

Biodiesel can be derived from oil found in animal and plant matter or even from recycled cooking oil. Much research has investigated the catalysis of the esterification and transesterification reactions needed to synthesize biodiesel. In this advance article, Patel and Narkhede contribute a novel catalyst towards the advancement of biodiesel as a competitive renewable energy source.

The authors used mono-lacunary silicotungstate supported on MCM-41, a mobile crystalline material hexagonal silicate, for the acid catalyzed esterification of oleic acid. They optimized the reaction up to 81% conversion with elevated temperature and prolonged reaction times. The researchers demonstrated the heterogenous catalyst could be reused in four iterative reactions without any appreciable loss in activity.

The transesterification of other oils including waste cooking oil, jatropha oil, sunflower oil, cotton seed oil and mustard oil was catalyzed in excellent yields. This catalyst is promising as an environmentally benign component of biodiesel production, though more research needs to be done to decrease the high catalyst loadings.

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Biodiesel synthesis via esterification and transesterification over a new heterogeneous catalyst comprising lacunary silicotungstate and MCM-41
Anjali Patel and Nilesh Narkhede

Tien Nguyen is working towards her PhD in David Nicewicz’s research group at the University of North Carolina at Chapel Hill, USA. Her current area of research focuses on anti-Markovnikov hydroamination of alkenes using photoredox catalysis.

Nitrogen containing aromatic compounds are important in pharmaceutical, materials and agrochemical applications. A direct, catalytic and selective reduction of nitroarenes is a desirable transformation that many groups have targeted.

In this advance article, researchers employed a ceria-supported heterogeneous gold catalyst in combination with 2-propanol as a hydrogen source as a mild system for the selective reduction of nitroarenes. Cao and colleagues obtained excellent yields of azoxyarenes, azoarenes and anilines by varying simple components of the reaction conditions. Running the reduction in the presence of 0.5 equivalents of KOH and water selectively yields the azoarene, while just lowering the amount of water diverts conversion to azoxyarenes. Exclusion of base at elevated temperatures furnishes the primary amine. Though the authors do not know the precise mechanism they propose involvement of a metal-hydride species similar to the Haber electrochemical hydrogenation.

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Mild, selective and switchable transfer reduction of nitroarenes catalyzed by supported gold nanoparticles
Xiang Liu, Sen Ye, Hai-Qian Li, Yong-Mei Liu, Yong Cao and Kang-Nian Fan
Catal. Sci. Technol., 2013, Advance Article

Tien Nguyen is working towards her PhD in David Nicewicz’s research group at the University of North Carolina at Chapel Hill, USA. Her current area of research focuses on anti-Markovnikov hydroamination of alkenes using photoredox catalysis.

Synthetic chemists have long been attempting to attain the exquisite levels of substrate selectivity offered by enzymes. Heterogeneous catalysts can provide high selectivities through the control of their porosity. While there are some strategies for achieving selectivity with homogeneous catalysis, this field still lags behind its enzymatic and heterogeneous counterparts.

In this advance article, Strukul and co-workers demonstrated substrate selectivity in the hydration of alkynes using a NHC-Au(I) catalyst encapsulated in a hexameric resorcin host. In the presence of the encapsulated catalyst the cyclic aliphatic alkyne was converted to product faster than the longer chain linear substrates. The authors ascribe this effect to the better fit of the cyclic substrate into the host cavity. Aromatic substrates were also tested and showed low yields likely due to their increased rigidity. Overall, aliphatic and aromatic alkynes were hydrated in low to modest yields but the observed trends serve as a valuable proof of concept.

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Substrate selectivity in the alkyne hydration mediated by NHC-Au(I) controlled by encapsulation of the catalyst within a hydrogen bonded hexameric host
Alessandra Cavarzan, Joost N. H. Reek, Francesco Trentin, Alessandro Scarso, and Giorgio Strukul
Catal. Sci. Technol. 2013, Advance Article, DOI: 10.1039/c3cy00300k

Tien Nguyen is working towards her PhD in David Nicewicz’s research group at the University of North Carolina at Chapel Hill, USA. Her current area of research focuses on anti-Markovnikov hydroamination of alkenes using photoredox catalysis.