It is a known fact that catalyst is actually an addition substance, which increases the rate of chemical reaction. A catalyst which increases the rate of reaction is called positive catalyst and if a catalyst decreases or retards the rate of reaction is called negative catalysts. Recently, a group of researchers from Abdullah University of Science and Technology developed a highly efficient catalyst that can easily convert propane gas into heavier hydrocarbons.
Researchers said, the speed of chemical reaction is now significantly high and it is known as alkaline metathesis. It could be used to produce liquid fuels, Phys.Org reported. Actually, this catalyst rearranges propane which contains three atoms such as butane, pentane, and ethane. Chemist Manoja Samantaray from the KAUST Catalysis Center said their aim is to convert lower molecular weight alkanes to valuable diesel-range alkanes.
The catalyst is actually composed of two material, titanium and tungsten which are anchored to a silica surface via oxygen atoms. Apart from this, the previous study showed monometallic catalysts were engaged in two functions, alkane to olefin and then olefin metathesis. Here, titanium was chosen because it has several advantages. It has the power to activate the C-H bond of paraffin to transform them to olefins, and tungsten was also chosen for its high activity for olefin metathesis, ACS Publication reported.
Here one question may arise that how they create the catalyst. At first, researchers heated the silica to remove the water from it, and then they added hexamethyl tungsten and tetraneopentyl titanium. Furthermore, the team studied the catalyst using nuclear magnetic resonance and they found the tungsten and titanium atoms lie extremely close together as close as 0.5 nanometers, on the silica surfaces.
After that lead researcher, Jean-Marie Basset again tested the catalyst by heating it to 150°C with propane for three days. Then, he found main products of the reaction were ethane and butane and that each pair of tungsten and titanium atoms could catalyze an average of 10,000 cycles before losing their activity. According to researchers, this turnover number is the highest ever reported for a propane metathesis reaction.
Researchers propose this success is an expected cooperative effect between the two metals. When a titanium atom removes hydrogen atoms from propane and then a neighboring tungsten atom breaks open propene's carbon-carbon double bond, creating fragments that can recombine into other hydrocarbons.But they also found that the tungsten or titanium did not perform well. When these two powders were mixed together, their performance did not good for the cooperative catalyst. Finally, the researchers are still trying to create an efficient catalyst with a high turnover number and long lifetime.
