Green Chemistry Blog

Charles Wyman and colleagues have demonstrated a highly effective lignocellulosic bio-refinery model, producing unrivalled quantities of furfural, 5-hydroxymethylfurfural (HMF), and levulinic acid as products. Proposed as a basis for the production of renewable fuels, the furan derivatives generated by this process are also a promising platform onto many other intriguing bio-based molecules. Additionally, more than 90% of the lignin contained within the maple wood feedstock was reclaimed, making the process as a whole exceptionally appealing.

Instead of the typical acidified aqueous media often used, the hydrolysis of the lignocellulose feedstock (and subsequent sugar dehydration) was enhanced with the addition of the potentially renewable solvent tetrahydrofuran. The organic solvent increased yields of HMF by an order of magnitude over what could be obtained otherwise in a one-pot reaction conducted at 170 °C. Under these optimised conditions, 87% of the total pentose (C5) sugar content was accountable in the form of furfural, while the hexose (C6) sugar content was converted from cellulose into HMF (in up to yields of 21% of the theoretical maximum), levulinic acid (up to 40%), and free sugars. The authors believe this represents a key step towards achieving commercial viability for sustainable, sugar derived bio-fuels.

By James Sherwood

This article is free to access for 4 weeks! Click the link below to read more:

THF co-solvent enhances hydrocarbon fuel precursor yields from lignocellulosic biomass, Charles M. Cai, Taiying Zhang, Rajeev Kumar and Charles E. Wyman, Green Chem., 2013, DOI: 10.1039/c3gc41214h

Here are the latest HOT papers published in Green Chemistry, as recommended by the referees:

Pharmaceutical Green Chemistry process changes – how long does it take to obtain regulatory approval?
Peter J. Dunn  
Green Chem., 2013, Advance Article, DOI: 10.1039/C3GC41376D

Preparation of waterborne functional polymers using a bifunctional coupler
Subrata Chattopadhyay, Helmut Keul and Martin Moeller  
Green Chem., 2013, Advance Article, DOI: 10.1039/C3GC41406J

An efficient and flexible synthesis of model lignin oligomers
W. Graham Forsythe, Mark D. Garrett, Christopher Hardacre, Mark Nieuwenhuyzen and Gary N. Sheldrake  
Green Chem., 2013, Advance Article, DOI: 10.1039/C3GC41110A

All the papers listed above are free to access for the next 4 weeks!

Albert Matlack, one of the founding educators of green chemistry and author of the book ‘Introduction to Green Chemistry’, selects his favourite papers in Green Chemistry this month…

Olefin metathesis in aqueous media, Jasmine Tomasek and Jürgen Schatz, Green Chem., 2013, 15, 2317–2338, DOI: 10.1039/C3GC41042K

This should cause one to think about how many discoveries leading to this result were made by chance. Herbert Eleuterio of duPont discovered metathesis when he used a molybdenum catalyst in a Ziegler polymerization of ethylene in 1957. Efforts to get consistent results with tungsten hexachloride were futile until it was found that tungstenoxytetrachloride worked well. Most metathesis catalysts were sensitive to air and moisture. However, a run with a hydrated ruthenium salt worked just as well as the anhydrous compound. This review covers work since then. The field of polymers today arose from accidental discoveries.

Low density polyethylene was found when chemists at ICI tried to react benzaldehyde with ethylene and got a trace of air in the bomb. High density polyethylene was discovered by Karl Ziegler who was studying the oligerimerization of ethylene with triethylaluminum when a trace of nickel from a partially cleaned bomb gave only 1-butene. When he tried titanium tetrachloride HDPE formed. Natta discovered stereoselective polymerization when he extended the reaction to propylene. Metallocene catalysts for the polymerization of olefins by Kaminsky were discovered when a student failed to blanket a polymerization with nitrogen. Plunkett of duPont discovered poly(tetrafluoroethylene) when a cylinder known to be full of the monomer released no monomer. Conducting polymers were found by Shirakawa, MacDiarmid and Heeger when a student put 1000 times too much catalyst in a polymerization of acetylene. An iodine reaction, presumably to determine the content of double bonds, showed how to dope it.

Add to these results of serendipity, H.C. Brown’s discovery of hydroboration while trying to reduce a double bond with diborane. Notice the number of Nobel prizes awarded for the various discoveries.

The message is, if something unusual happens, check to see why.

Organic solvent-free and efficient manufacture of functionalized cellulose nanocrystals via one-pot tandem reactions, Lirong Tang, Biao Huang, Nating Yang, Tao Li, Qilin Lu, Wenyi Lin and Xuerong Chen, Green Chem., 2013, 15, 2369–2373, DOI: 10.1039/C3GC40965A

Functionalized cellulose nanocrystals were formed via ball milling followed by ultrasonication. The reaction was run with a large excess of maleic anhydride in 20% aqueous sulfuric acid. No organic solvent was present. After balling for an hour, ultrasonication for 7 hours gave a 61% yield with 0.34 degree of substitution. It might be good to substitute less maleic acid and to run a final ring closure by heating. Other monomers could be tried as well.