Packing a Pyrolytic Punch
Using their own licensed catalytic fast pyrolysis process for converting nonfood lignocellulosic biomass such as wood, agricultural residues and energy crops into a variety of bioboased compounds equivalent to their petrochemical counterparts, a team of University of Massachusetts Amherst chemical engineers, led by George Huber, has developed a new bifunctional gallium-promoted zeolite (Ga/ZSM-5) catalyst that boosts yield of aromatics, namely benzene, toluene and a mixture of xylene isomers, as well as olefins ethylene and propylene, by 40 percent over previously used zeolite based catalysts. The new process was published in the December edition of the German Chemical Society’s journal Angewandte Chemie.
The increase in yield, according to Huber, is attributed to adding small amounts of gallium oxide to the previously naked zeolite catalyst. In the single-step catalytic fast pyrolysis process, biomass is fed into a fluidized-bed reactor where it’s pyrolyzed into vapors. These vapors subsequently enter the team’s improved gallium-zeolite catalyst, inside the same reactor, which converts the vapors into aromatics and olefins.
Huber explains that when gallium is introduced, it uniquely modifies certain catalytic sites within pores innately featured on the zeolite catalyst, which improves certain key reactions, resulting in improved aromatic and olefin yield.
“There are two key reactions that we think it improves,” Huber tells Biorefining Magazine. “One is in decarbonylation reactions, which are critical to breaking carbon-oxygen bonds to make carbon monoxide, and for removing oxygen found in the biomass. The other is the oligomerization reactions for making olefins so they can be oligomerized better.” Huber says the economic advantages of this new process are three fold: the reaction chemistry occurs in one single reactor, the process uses an inexpensive catalyst, and aromatics and olefins that are produced can easily be dropped into the existing petrochemical infrastructure.
While the research team’s catalytic pyrolysis technology has been licensed to New York-based Anellotech Inc., co-founded by Huber, which is scaling up the process for introduction into the petrochemical industry, Huber notes that work is ongoing to further improve the process.
“We’re trying to understand what the gallium is exactly doing, improve the catalyst even further and demonstrate this on a larger scale, and move this technology forward so we can economically make aromatics and olefins from biomass,” he says.