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China researchers develop one-pot process for direct conversion of cellulose to ethanol

Researchers in China have developed a one-pot process for the direct conversion of cellulose to ethanol with a yield of 43.2 C% over a multifunctional catalyst Mo/Pt/WOx, which effectively catalyzes the tandem reactions of cellulose to ethylene glycol (EG) and then to ethanol. A paper on their work is published in the journal Joule.

Yang

The researchers suggest that the inherent advantages of a chemocatalytic process in continuous operation and scalability will make it a promising alternative to the current bioprocess for the production of cellulosic ethanol.

The increasing concerns over global climate change have motivated great interest in the utilization of renewable biomass for the production of fuels and chemicals. Among various platform and end-use products derived from biomass, cellulosic ethanol is the most important one. It is envisioned that up to 30% of the transportation fuels will be derived from biomass by the year of 2030 in order to limit CO2 emissions, and cellulosic ethanol will be a leading player as it can be directly used as a drop-in bio-fuel in gasoline.

The current production of cellulosic ethanol is predominantly through the bioconversion process. While great progress has been made in engineering microbes for biofuel production, the economically viable production of cellulosic ethanol remains a great challenge because of the recalcitrance of lignocellulose.

In contrast to the bio-production of cellulosic ethanol, the direct conversion of cellulose to ethanol by a chemical approach is yet to be developed, although a plethora of chemicals other than ethanol have already been synthesized directly from lignocellulose via various chemocatalytic routes. … Herein, we report the one-pot direct conversion of cellulose to ethanol over a multi-functional catalyst Mo/Pt/WOx (2 < x < 3).

—Yang et al.

Under a reaction condition of 245 ˚C and and 6 MPa H2, cellulose was completely converted, and the ethanol yield reached 43.2 C%. In this three-component catalyst, the WOx catalyzed the C-C cleavage of cellulose to form glycolaldehyde, while the sequential introduction of Pt and Mo to the WOx enabled it not only to catalyze the hydrogenation of glycolaldehyde to EG but also to promote the C-O cleavage of EG to form ethanol.

Resources

  • Yang et al. (2019) “One-Pot Production of Cellulosic Ethanol via Tandem Catalysis over a Multifunctional Mo/Pt/WOx Catalyst,” Joule doi: 10.1016/j.joule.2019.05.020

Comments

mahonj

Interesting. The world will be a very fertile place with all that CO2 in the air. MIght be able to grow lots of trees and convert them to ethanol.
Q: When they say "43.2 C%" what do they mean - is the 56.8% waste that never could become ethanol, or waste than could never become ethanol?

The Lurking Jerk

I want to second that question, Mahonj. 43.2% of the material by weight, or 43.2% of the theoretical possible yield, or what??? Can anyone help out?

SJC

That could be the amount of carbon converted, the rest could be gasified to make more fuel.

Arnold

A simple way to read that could be that of the C passing the catalyst , the output retains 43% the rest may be activating the cat. Another reading could be that the remaining 56% C contributes to the whole process energy requirement which includes a heat input.
Either way it does suggest that overall energy conversion efficiency if the cellulose carbon is given as X (C) shows the 43%X converted .
Saying X for (C) saves getting technical r.e. the exact full chemical composition of the 'cellulose input.
The other components H&O are not included in the article.
An example would be. cellulose C6H10O5.

Wiki states. Chemical formula (C6H10O5)n
"Cellulose is an organic compound with the formula ₙ, a polysaccharide consisting of a **linear chain of several hundred to many thousands of β linked D-glucose units**. " **=my add.

Clear as mud?

Arnold

Some amount of the H& O will turn up in the ethanol C2H5OH It's just not mentioned.

Peter_XX

If they say: "... a yield of 43.2 C%...", it must be clear that this is the carbon efficiency. Energy efficiency is not quite the same. Plant mass contains relatively little hydrogen, so for sure, most of the energy is in the carbon. Ethanol contains more hydrogen than the plant but this does not mean that energy efficiency is much higher than carbon efficiency, since a lot of the energy used in the process must come from the carbon in the plants, or from other sources, e.g. electricity. Most likely, the energy efficiency is lower and this would be the most interesting result to know. Another point is that the system boundaries are very important when you try to assess the total energy efficiency. For example, you might get a sizeable share of the energy left in by-products and one of the trickiest things is to credit for this stuff or find a way of expanding the system boundaries to take it into account. This, however, seems to have been beyond the scope of the study.

Engineer-Poet

This piece not only omits any list of the non-EtOH byproducts and their fractional representation, it also fails to mention how much hydrogen is required.  It does say

cellulose was completely converted
but does not mention what happened to any associated lignin or even if that included hemicellulose.

Depending exactly what those non-EtOH products are and how much H2 is required, this might be a very useful conversion.  OTOH if there's lots of methane and other low-value, hydrogen-intensive products it might not.

The upside is that it claims 100% conversion of cellulose, and presumably all of the carbon winds up as something other than CO2.

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