Catalysis Science & Technology Blog

Posted on behalf of Tien Nguyen, web-writer for Catalysis Science & Technology

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

On May 8^th 2013, the NOAA’s (National Oceanic & Atmospheric Administration) Mauna Loa observatory recorded a daily mean concentration of CO₂ in excess of 400 ppm, a record high since mankind’s appearance on the planet. As carbon dioxide levels continue to increase at an alarming rate, many laboratories are engaging in alternative energy research to mitigate this problem. 

One such solution involves the methanation reaction, which converts syngas (CO + H₂) to synthetic natural gas (CH₄). This reaction is highly sought after given that energy from burning natural gas releases approximately 30-45% less carbon dioxide than fossil fuels. 

In this article, researchers evaluated a series of α-Al₂O₃-supported Ni catalysts of various Ni particle size (5-10, 10-20 and 20-35 nm) for their catalytic efficiency in the methanation reaction. At high temperatures (300-600 °C), ambient pressure and high WHSV (weight hourly space velocity of 240,000 mL/g/h), Ni particles sized 10-20 nm exhibited the highest CO conversion, CH₄ yield and turnover frequency, as well as the lowest carbon deposition. 

They hypothesized that the smaller Ni particles exhibit more carbon deposition because they have more exposed step edges, which are more susceptible to such formations. They also proposed that Ni particles that are too large may lead to the undesirable growth of carbon nanofibers. Having identified the optimal Ni particle size, the next advancement for the CO methanation reaction lies in improving the stability of these catalysts. 

Read the article here: 

Effect of nickel nanoparticle size in Ni/α-Al₂O₃ on CO methanation reaction for the production of synthetic natural gas
Jiajian Gao, Chunmiao Jia, Meiju Zhang, Fangna Gu, Guangwen Xua and Fabing Su

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.

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

Alexander Todd and Christopher Bielawski from the University of Texas, at Austin have combined zeolites with graphite oxide to enhance their catalytic activities when dehydrating alcohols.

Although both catalysts can be used independently, the team observed a synergistic activity when the catalysts were used in tandem.

Protic zeolites (where H⁺ is the counter cation) are usually prepared by either ion exchange or high temperature calcination of an ammonium ion exchanged precursor, although ion exchange is not really viable for zeolites with low silica content (such as NaY zeolites). However, Bielawski found that NaY zeolites could be used without either preparation step due to a little help from graphite oxide.

The researchers propose that H⁺ is released from the graphite oxide upon its dispersion in solvent which exchanges with the Na⁺ ion in the zeolites to produce the protic form. The graphite oxide–zeolite duo was found to catalyse the dehydration of secondary, tertiary and primary aliphatic alcohols to the corresponding olefinic products with very favourable conversions.

Download the Catalysis Science & Technology article now for more details…

Graphite oxide activated zeolite NaY: applications in alcohol dehydration
Alexander D. Todd and Christopher W. Bielawski