The innovative chemical process modifies cellulose, present in non-edible plant matter such as wood, straw, grass, cotton, or paper, by removing oxygen bonded to its hydrocarbon chains while preserving the chains’ structure.
There has also been recent progress in developing cellulosic nanomaterials from wood material, stiff and lightweight products from cellulose manipulated at the molecular level.
The development of commercial markets for cellulosic nanomaterials, tiny, naturally occurring structural building blocks, hold great promise for many products in electronics, construction, food, energy, health care, automotive, aerospace, and defence. These products could include jet fuel, aerogels, oil drilling additives, paints, coatings, adhesives, cement, food additives, lightweight packaging materials, paper, health care products, tissue scaffolding, lightweight vehicle armour, space technology, and automotive parts.
The US Forest Service released a report last week “Cellulose Nanomaterials – A Path towards Commercialization” [link: http://www.fpl.fs.fed.us/documnts/pdf2014/usforestservice_nih_2014_cellulose_nano_workshop_report.pdf] out of a workshop it sponsored earlier this year. It will be very helpful to a wood products industry looking for ways to innovate develop new products and markets.
Energy from Cellulose
Back to Belgium, Bert Lagrain, from the Centre for Surface Chemistry and Catalysis at the Catholic University of Leuven, who led the sawdust research said, “This is a new type of bio-refining, and we currently have a patent pending for it. We have also built a chemical reactor in our lab: we feed sawdust collected from a sawmill into the reactor and add a catalyst – a substance that sets off and speeds the chemical reaction.”
Cellulose is the main substance in plant matter. At the molecular level, cellulose contains strong carbon chains, the researchers wanted to conserve these chains while at the same time dropping the oxygen bonded to them, which is undesirable in high-grade gasoline. With the right temperature and pressure, it takes about half a day to convert the cellulose in the wood shavings into saturated hydrocarbon chains.
The new method allows the researches to create a petrochemical product using these wood shavings. That said, this is an intermediary product that still requires another step before it becomes fully-distilled gasoline. Yet it’s an important step forward when it comes to creating sustainable fuel.
The team believes their invention would be particularly valuable for Europe, which doesn’t have abundant resources of oil. The hydrocarbon chains could be added into gasoline, replacing a portion of the fossil fuel. Unlike conventional energy crops, cellulose doesn’t compete for land use with food crops as it is basically a side product of any plant production.
The resulting product does not come out as fully-distilled gasoline, the intermediary product requires one last simple step to become fully-distilled gasoline, said Sels.
“Our product offers an intermediate solution for as long as our automobiles run on liquid gasoline. It can be used as a green additive, as a replacement for a portion of traditionally-refined gasoline,” Sels said.
“The green hydrocarbon can also be used in the production of ethylene, propylene and benzene — the building blocks for plastic, rubber, insulation foam, nylon, coatings and so forth,” Sels added.
“Essentially, the method allows us to make a ‘petrochemical’ product using biomass – thus bridging the worlds of bio-economics and petro chemistry,” Sels’ colleague Bert Lagrain said.
The material can also be used to make chemicals such as ethylene, propylene, and benzene – the building blocks for plastic, rubber, insulation foam or nylon.
The researchers are also excited about the potential of cellulose to replace other products currently derived from petroleum, and its general abundance and accessibility.
“From an economic standpoint, cellulose has much potential,” said Sels. “Cellulose is available everywhere; it is essentially plant waste, meaning it does not compete with food crops.”
“It also produces chains of 5 to 6 hydrocarbon atoms. We are currently facing shortages in this because it is becoming quite difficult and more expensive to distil these specific hydrocarbon chains from crude oil or shale gas.
Two phases are involved within the one container. Tungstosilicic acid in aqueous phase causes the cellulose to hydrolyse and dehydrate, after which hydrogenation creates the liquid alkanes, which are saturated hydrocarbons. The high yield consists of 82 per cent n-decane-soluble products, mainly hexanes, known as light nafta. There is only a small amount of charring and a low percentage of gaseous products. And the length of time this takes is a mere few hours. Although not instant, this is catalytic and therefore able to convert more and more cellulose to glucose, especially with gradual heating of the reaction.
The second phase consists of a Ru/C (ruthenium) catalyst that is hydrothermally modified (ie. tuned) to make it chemo-selectively suitable. More rapid hydrogenation of the correct substrate is therefore possible, while for the whole set of reactions, subsequent batches of softwood cellulose can be introduced. The liquid alkanes can then accumulate over several runs.