Researchers Develop New Hybrid Membrane With High Hydrothermal Stability; Potential Energy-Efficient Replacement for Distillation Techniques in Biofuel Production
07 February 2008
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| The cylinder is the carrier of a hybrid membrane: a layer of about 100 nanometer thickness. The insert is a close-up of the layer showing the organic links and pores. From the left of the tube, only water molecules leave the sieve. Click to enlarge. |
Researchers at the University of Twente in The Netherlands have developed a new hybrid organic–inorganic nanosieve membrane with high hydrothermal stability that enables energy-efficient molecular separations, including dehydration up to at least 150° C, even after long periods of continuous exposure to water.
The hybrid membranes are suitable for dehydrating solvents and biofuels, an application for which there is a large potential market worldwide. The main advantage of membrane technology is that it consumes far less energy than common distillation techniques. The scientists also foresee opportunities in separating hydrogen gas from gas mixtures and also in water desalinization applications.
Hydrothermal stability over long periods of time has been one of the barriers to more widespread applications of molecular sieving membrane technologies in areas such as in energy-efficient separation of biomass fuel and hydrogen, dehydration of condensation reactions, and breaking of azeotropic mixtures during distillation (e.g., hydrous ethanol).
Of the materials considered for membranes—including polymers, zeolites and metal oxides—a supported 30–100 nm thin film of nanoporous silica (SiO2) is one of the most promising systems for molecular separation of gases and liquids, according to the researchers. Amorphous silica combines high permeability for molecules <3 Å (e.g., H2O, H2) with very low permeability for larger ones. It has high mechanical, thermal and solvent stability and can be applied at 600 °C in dry atmospheres.
However, prolonged exposure to water at temperatures as low as 60° C leads to hydrolysis, resulting in large non-selective pores and cracks.
Replacement of silica by other candidate materials, the researchers note in their paper, has not resulted in stable membranes while retaining both selectivity and a high permeation rate. Instead, the Dutch team replaced part of the ceramic links with organic links.
The strategy behind the present work was to replace as many siloxane bonds as possible by hydrolytically stable Si–C links, while raising the CHx : Si ratio to 1... We aimed at a microporous material with pore diameters of 2–4 Å, similar to the kinetic diameter of small molecules. Our prime aim was, however, to prepare a material with a high hydrothermal stability, i.e., a persisting high selectivity towards molecular separation at high temperatures in the presence of water.
After 18 months of testing of the hybrid membrane for the dehydration of n-butanol (5 wt% water) by pervaporation at 150 °C, the membrane remained stable and still highly selective.
Manufacturing the new hybrid membrane is simpler than manufacturing ceramic membranes, because the material is flexible and will not show cracks. What the new membranes have in common with ceramic membranes is the rapid flow—one advantage of this is that the membrane surface can be kept small.
The scientists, who cooperated with colleagues from the Energy research Centre of the Netherlands (ECN) and the University of Amsterdam, present their invention in an open access article in the journal Chemical Communications.
Resources
Hessel L. Castricum, et.al., Hybrid ceramic nanosieves: stabilizing nanopores with organic links. Chem. Commun., 2008, DOI: 10.1039/b718082a
The downside of this is that the membrane is permeable to the 95% water. The energy to evaporate this has to come from somewhere, and I can't see any way to improve the performance without e.g. multiple-effect pervaporation .
Posted by: Engineer-Poet | 07 February 2008 at 11:39 AM
@ Engineer-Poet -
I'm not sure if I understand you correctly, are you saying this membrane material will only remove 95% of the water from an aqueous solution of e.g. ethanol? Given that the azeotrope of that mixture is at 93% ethanol, this would permit its production using mechanical pressure alone.
Posted by: Rafael Seidl | 07 February 2008 at 12:14 PM
Ah. Sorry, you're right; I mis-read the article.
Still, the bugs which produce butanol tend to produce very dilute solutions of same (per Robert Rapier). The problem isn't going to be getting from 93% to anhydrous, it'll be going from 2% to 93% without wasting more energy than is in the product.
Posted by: Engineer-Poet | 07 February 2008 at 02:01 PM
@EP,
But doesn't Butanol naturally separate from water? Can't you skim it off the top if you set it up right?
Posted by: | 07 February 2008 at 02:10 PM
I'm done with the nameless. Get yourself a nick and we'll talk.
Posted by: Engineer-Poet | 07 February 2008 at 04:17 PM
@EP,
Sorry, that was me. I reinstalled my browser and didn't notice it didn't remember my nom de GCC.
Butanol doesn't absorb water the way ethanol does, right? Doesn't that mean Butanol can be more readily separated from water by using it's differing density?
Posted by: Healthy Breeze | 07 February 2008 at 05:34 PM
"Get yourself a nick and we'll talk"-EP
Sorry to put something irrelevant on the board, but....
LOL
Posted by: GreenPlease | 07 February 2008 at 06:50 PM
I'm relying on what Robert Rapier has said about butanol. It's quite a bit easier to separate from water than ethanol, but it's also toxic in far smaller proportions. The bugs which make it are poisoned before it gets concentrated enough to separate by itself, IIRC.
Posted by: Engineer-Poet | 07 February 2008 at 08:17 PM
Heard on NPR today where there is information that Bio fuels may be as polluting as fossil fuels! I don't have any details but this is what I feared would be the case. When we continue to use ICEs to burn any fuel in the atmosphere we create byproducts. And, some of those byproducts are toxic to humans. It will be interesting to see how this all pans out. Bio fuel may be just another interium solution leading to solar generation and electric cars, except for jet engines.
Posted by: Lad | 07 February 2008 at 11:36 PM
Electric vehicles are independent of petroleum, but one thing you'll notice about "bio"fuels is that they are carefully selected to be interchangeable with petroleum; if we didn't care, we'd use 190-proof ethanol. Today's biofuel measures have the effect of maintaining the market for petroleum regardless of the claimed goals.
Posted by: Engineer-Poet | 08 February 2008 at 06:41 AM
You still get elements of combustion and new compounds that you did not get with gasoline, like aldehydes from combustion of ethanol in an I.C.E.
Ethanol is an interim step. I consider it an additive to gasoline. E10 replaces almost 10% of the oil used to make gasoline, that is no small thing, considering the size of the situation. That is more than 1 million barrels per day of oil that we do not have to import, once we can get cellulose ethanol on commercial affordable scale, we will have something more sustainable.
We will have to combine this with hybrids, telecommuting, locating jobs and homes closer together and many other efforts. I think we may see some big changes in the next few years and we have to be ready to make them happen.
Posted by: sjc | 08 February 2008 at 06:59 AM
enzymatic ethanol is a waste.
gassification to ethanol looks to be a better path forward then you don't build a giant refinery thats limited in its fuel production.
maybe the way to beat oil is to model how its used and its not utilized by producing one single product
if rather than building these large mono-fuel refineries they had been built as feedstock agnostic we might be farther along than we are.
gassification and/or anaerobic digestion with those two systems you can pretty much handle any feedstock that comes your way: metal, woodwaste, plastic, biomass, household food waste, etc.
with this combo you can scale to locate near just about any size city or town and produce a number of different types of fuels; ethanol biodiesel methane hydrogen, the list goes on
side question: could this membrane be adapted to process water out of ethanol running through a pipeline?
Posted by: phronesis | 08 February 2008 at 08:28 AM
An oil refinery produces lots of different products, gasoline was something created while making kerosene. The main input to the process is still oil. They also use hydrogen reformed from natural gas to make the higher octane fuels.
Transporting ethanol has become a major issue. Since they have to transport the ethanol from where it is produced to where it is used, they require trucks and trains. Much of the train capacity is already used. I would favor making ethanol closer to where it is used.
There were some studies about making ethanol from the rice straw in California's central valley. That would reduce some of the transportation requirements. I have not seen anything definitive come from those studies.
Posted by: sjc | 09 February 2008 at 08:28 AM
Algae
All food crops should be left on the table, other than oil in the fryer that can be recycled as biofuel.
According to Valence Technologies, www.valence.net, using their vertigro system they can make 33,000 gallons of algae biodiesel per acre and turn excess residue into ethanol. This can be done on non productive land.using sunlight, a little water, and carbon. The algae can replicate itself 7 times per day. Also, www.solazyme.com, claims that you can grow algae without sunshine by adding sugar to the algae, increasing its yield beyond what sunshine can provide, and grow algae at night. Algae farms can be sited next to any industry that is producing carbon and recycle that carbon into algae, whose biofuel can then be used in generators to totally electricfy the world and, recycle the carbon generated back into the algae and, on and on, using existing electric transmission lines. No emmisions except for reduced greenhouse gas from aircraft! No wars! Electric vehicles and clean, clean air!!!
A question is, "will this new membrane dehydrate the water from algae to make biofuel?"
Posted by: solarnano | 11 February 2008 at 01:54 AM
You got a link for that Vertigro thing?
It sounds over-hyped to me. First, the figures I've been seeing before are in the 10-20 thousand gallon/ac/yr range; 33,000 seems like marketing-speak. Second, "Vertigro" implies a lot of structure, which implies a lot of capital cost. Third, the productivity implies use of concentrated CO2, from e.g. a fossil-fired powerplant; such systems cannot even be carbon-neutral.
Posted by: Engineer-Poet | 11 February 2008 at 06:31 AM
First go to the, www.valcent.net, web site listed in my comment, and check out news to find the 33,000 gallon figure. Second check out their video of their working pilot plant to see the structure and, the claim that they can power the US using an area 1/4 the size of new Mexico. How much infrastructure and acreage would you need to make 33,000 gallons of corn biofuel at 18 gallons per acre? Third,why would you suggest using a fossil fueled power plant when you can use an electric generator that uses algae biofuel, and returns the carbon in a closed loop system to grow more algae? The electricity produced goes into existing power lines. Pretty basic.
Posted by: solarnano | 11 February 2008 at 10:30 PM
Corn ethanol averages 420 gallons per acre, not 18.
Easy Automation, in Welcome, Minnesota, the primary provider of software for feed mills in the U.S., has been developing a biofuels plant that would fit into a shipping container. Here is a report from the VOA: "'...it's a complete self-contained ethanol plant that's about the size of a shipping container that's all pre-wired, all pre-plumbed. All the software and the automation is all part of it. And what the idea is, that these can be dropped into any unused facility across rural America and start making ethanol.' Company president Mark Gaalswyk says his so-called "gas-in-a-box" plant — which is still in development — uses an enzyme process to break down cellulose fibers into ethanol. So instead of using corn or another food plant as the raw material, corn husks or similar waste material goes in one end; ethanol comes out the other, along with a by-product that can be used as animal feed." http://www.voanews.com/english/archive/2006-07/2006-07-07-voa42.cfm?CFID=269670822&CFTOKEN=55012306
Decentralized biofuels processing has many advantages, and membranes that work at low temperatures can help that process along.
Biofuels have been getting a bum rap lately, being blamed for effects not of their own making. The recent media reports on articles in Science magazine on GHG release from biofuels production being greater than fossil fuel burning fail to note that carbon released from living plants and peat bogs is already part of the earth's carbon cycle and do not represent a net increase in carbon, whereas, carbon released from fossil fuels is new carbon introduced into the system. That's a huge, huge difference. All living things die and release their carbon, whether it is sooner or later.
Posted by: fred schumacher | 12 February 2008 at 03:26 PM
- Inadequate raw material to replace petroleum, natural gas and coal, given system losses.
- Incompatibility of liquid-fuel production with aggressive carbon sequestration/climate remediation.
These things have to be considered as a system, and I see no system-level thinking here. Peat bogs can be stable for hundreds or thousands of years, but be released in one season's forest fires. This is a net increase in atmospheric carbon, just like chopping down rainforest.Posted by: Engineer-Poet | 15 February 2008 at 11:08 PM
I am interested in your membrane, and we are designing systems to use various membrane in Mirco to RO type from oil to water. Pls advise if we can buy or get some sample for our applications.
DMC
Posted by: DMC | 18 May 2008 at 02:12 AM
I will update this to clear up the confusion. I only found this link as I just joined ECN. Apologies for that.
The point of the membrane is that it can dehydrate organics. That means that it can replace molecular sieves for ethanol production and can be used instead of the high organic distillation column in butanol.
Therefore it will always be coupled with another process for a mixture coming from the fermenter. This there will be distillation-pervaporation or pervaporation (using an MTR membrane)-pervaporation.
Posted by: riven | 19 October 2009 at 01:59 AM
I will update this to clear up the confusion. I only found this link as I just joined ECN. Apologies for that.
The point of the membrane is that it can dehydrate organics. That means that it can replace molecular sieves for ethanol production and can be used instead of the high organic distillation column in butanol.
Therefore it will always be coupled with another process for a mixture coming from the fermenter. This there will be distillation-pervaporation or pervaporation (using an MTR membrane)-pervaporation.
Posted by: riven | 19 October 2009 at 01:59 AM