New one-pot process for conversion of cellulose to n-hexane, a gasoline component
26 June 2014
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| One-pot process for conversion of cellulose to hexane, a gasoline component. Credit: ACS, Liu et al. Click to enlarge. |
Researchers at Tohoku University in Japan have developed a one-pot process to convert cellulose to n-hexane in the presence of hydrogen gas. According to the US Environmental Protection Agency (EPA), unleaded gasoline contains about 11.6% n-hexane.
In a paper in the journal ACS Sustainable Chemistry & Engineering, the Tohuku team reports achieving a yield of n-hexane of 83% from ball-milled cellulose and 78% from microcrystalline cellulose. Even using a high weight ratio of cellulose to water (1:1), a 71% yield of n-hexane could be obtained from ball-milled cellulose.
The biphasic transformation consists of the hydrolysis of cellulose to glucose, hydrogenation of glucose to sorbitol, and successive hydrogenolysis of sorbitol to n-hexane. It involves two catalysts: iridium and rhenium oxide on silica support (Ir-ReOx/SiO2 (Re/Ir = 2) catalyst combined with HZSM-5 as co-catalyst.
Recently, our group conducted conversion of sorbitol, glucose, and cellobiose into n-hexane over the Ir-ReOx/SiO2 catalyst combined with HZSM-5. Over 90% yield of n-hexane could be obtained at ≤443 K. However, production of n-hexane from cellulose via these compounds needs the extra step of hydrolysis of cellulose. Direct conversion of cellulose into n-hexane with a heterogeneous catalyst in high yield at mild reaction conditions would be more meaningful. To the best of our knowledge, this conversion process has not yet been reported.
In this work, the binary Ir-ReOx/SiO2 and HZSM-5 catalyst system was applied to one-pot conversion of cellulose into n-hexane. High (∼80%) yield of n-hexane was obtained from ball-milled cellulose or even microcrystalline cellulose.
—Liu et al.
They found that the preferable reaction temperature is 463 K (190 ˚C) and 483 K (210 ˚C) for ball-milled and microcrystalline cellulose, respectively. They also found that recycling the Ir-ReOx/SiO2 catalyst + HZSM-5 is feasible under the reaction conditions.
Resources
Sibao Liu, Masazumi Tamura, Yoshinao Nakagawa, and Keiichi Tomishige (2014) “One-Pot Conversion of Cellulose into n-Hexane over the Ir-ReOx/SiO2 Catalyst Combined with HZSM-5,” ACS Sustainable Chemistry & Engineering doi: 10.1021/sc5001463
I don't understand why the article quotes the EPA on the concentration of n-hexane in fuel. Any oil company could tell you that too. In fact, any undergraduate chemistry student could tell you that with access to a GC. Is the invocation of the EPA somehow a hint that n-hexane is good or bad? It makes no sense. I don't really think you even need a source for that info since it is so common place.
Additionally, since the amount of n-hexane in gasoline is largely determined by it's natural abundance in crude oil it's not certain that 11% is the optimum level of n-hexane for gasoline if you had a different source of it. What is the probable reason for the specific blend concentrations is what is the natural distilled components in crude, what can be cracked and added, and then what needs to be added to make it work well. You may have a completely different blend that acheives the same performance if you have different sources. Fuel scientists may tell you it's not that simple, but then part of their job is to convince you that you need them and their product. They are not interested in revealing any path to nonconsumption of their product.
Posted by: Brotherkenny4 | 26 June 2014 at 11:35 AM
Hexane is much better used in a diesel fuel; In fact heptane with one more CH2 group from Jeffry Pine, a relative of Ponderosa pine, was once used as the standard of ZERO motor octane gasoline. Someone else can tell you what its cetane rating is; probably about 40. ..HG..
Posted by: Henry Gibson | 27 June 2014 at 08:27 PM
Hexane has an octane rating of about 25. Diesel engines or now tiny turbines from Bladon jets should be used in automobiles for higher efficiencies and very low NOx without catalysts and no particulates. Diesel or jet fuel is cheaper to produce from crude oil and should cost less. the production of gasoline instead of diesel releases more CO2 in production and more Co2 in use. ..HG..
Posted by: Henry Gibson | 27 June 2014 at 08:43 PM
Ball mill cellulose to produce this? You'd be better off using mushrooms and termites to break down your wood. I takes time but I'm sure you backyard biofuel enthusiasts have it.
Posted by: kalendjay | 30 June 2014 at 04:18 PM