{"id":21265,"date":"2014-07-03T02:11:54","date_gmt":"2014-07-03T00:11:54","guid":{"rendered":"http:\/\/www.biofuelsdigest.com\/bdigest\/2014\/06\/30\/rice-university-converts-biodiesel-waste-into-chemicals-with-nanoparticles\/"},"modified":"2014-07-02T13:24:51","modified_gmt":"2014-07-02T11:24:51","slug":"water-cleanup-catalysts-tackle-biomass-upgrading","status":"publish","type":"post","link":"https:\/\/renewable-carbon.eu\/news\/water-cleanup-catalysts-tackle-biomass-upgrading\/","title":{"rendered":"Water-cleanup catalysts tackle biomass upgrading"},"content":{"rendered":"

Rice University chemical engineer Michael Wong has spent a decade amassing evidence that palladium-gold nanoparticles are excellent catalysts for cleaning polluted water, but even he was surprised at how well the particles converted biodiesel waste into valuable chemicals.<\/strong><\/p>\n

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Through dozens of studies, Wong\u2019s team focused on using the tiny metallic specks to break down carcinogenic and toxic compounds. But his latest study, which is available online and due for publication in an upcoming issue of the Royal Society of Chemistry\u2019s journal Chemical Science, examined whether palladium-gold nanocatalysts could convert glycerol, a waste byproduct of biodiesel production, into high-value chemicals.<\/p>\n

In scientific parlance, the data from the study produced a \u201cvolcano plot,\u201d a graph with a sharp spike that depicts a \u201cGoldilocks effect,\u201d a \u201cjust right\u201d balance of palladium and gold that is faster \u2014 about 10 times faster \u2014 at converting glycerol than catalysts of either metal alone.<\/p>\n

\u201cWe\u2019ve now seen this volcano plot at least four times now, first with TCE, then with the dry cleaning contaminant \u2018perc,\u2019 and more recently with chloroform and nitrites,\u201d Wong said. \u201cThe remarkable thing is that the reaction, in each case, is very different.\u201d<\/p>\n

In previous studies, the nanocatalysts were used in reduction reactions, chemical processes marked by the addition of hydrogen. In the latest tests on glycerol conversion, the nanocatalysts spurred an oxidation reaction, which involves adding oxygen.<\/p>\n

\u201cOxidation and reduction aren\u2019t just dissimilar; they\u2019re often thought of as being in opposite directions,\u201d Wong said.<\/p>\n

In chemistry, the role of the catalyst is much like that of a matchmaker; catalysts cause other compounds to react with one another, often by bringing them into close proximity, but the catalysts themselves don\u2019t take part in the reaction. Catalysts often speed up reactions that would otherwise happen too slowly, and drugmakers and chemical companies use catalysts to improve the efficiency of their chemical processing. The global market for industrial catalysts is projected to top $19 billion by 2016.<\/p>\n

Palladium and gold \u2014 and mixtures of the two \u2014 have long been recognized as extremely effective catalysts. Among catalysts, gold is now valued because it doesn\u2019t tarnish or oxidize, a process that can shorten a catalyst\u2019s lifespan. Palladium is typically prized because it is especially good at binding and inducing molecules to reduce or oxidize. Wong and colleagues have demonstrated a way to bring these two metals together with better control. They build their catalysts on gold spheres that are about four nanometers in diameter. The spheres are partially covered with palladium, so that the particles\u2019 surface contains some gold and some palladium.<\/p>\n

Wong and colleagues have shown that covering 60-80 percent of the gold\u2019s surface area with palladium typically produces the ideal catalyst \u2014 though the exact percentage varies for different reactions.<\/p>\n

\u201cOur synthesis knob, the thing we use to dial in the efficiency, is the coverage area, and the precision of that knob is really what sets us apart from other people who are studying bimetallic catalysis,\u201d Wong said. \u201cThat precision is what produces these beautiful volcano plots, but it also helps in another way because it allows us to develop a rigorous explanation for the effects that we\u2019re measuring.\u201d<\/p>\n

In the latest study, Wong, Rice graduate student and lead author Zhun Zhao and colleagues from Rice, Argonne National Laboratory and the University of Groningen in Holland used high-powered X-ray spectroscopy and other techniques to show that the \u201cGoldilocks\u201d coverage area for glycerol catalysis was about 60 percent.<\/p>\n

\u201cPalladium by itself oxidizes, which is not good because it slows down the catalysis,\u201d Zhao said. \u201cWe found that the gold in our catalysts helps stabilize the palladium and prevents it from degrading. The catalysts in our tests had extremely high durability. Our best catalyst produced a glycerol product with higher purity and in less time than anything else we found in the literature.\u201d<\/p>\n

Wong said the research opens up an exciting new area of exploration for his lab.<\/p>\n

\u201cNow that we understand how these work with glycerol, we can study reactions of other biomass molecules like glucose, a building block of plants,\u201d Wong said.<\/p>\n

Additional co-authors include Rice\u2019s Lori Pretzer, Pongsak Limpornpipat, James Clomburg and Ramon Gonzalez, Groningen\u2019s Joni Arentz and Argonne\u2019s Neil Schweitzer, Tianpin Wu and Jeffrey Miller. The research was supported by the National Science Foundation, the Welch Foundation, the Sigma Xi Grants-in-Aid of Research program, Rice University and the Department of Energy.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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