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Climate Change: Not Just CO2

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Helios223

Helios223

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Okay firstly, unnatural climate change is happening and it is due mainly to carbon dioxide from fossil fuels. This is immediately obvious to anyone who bothers to do any research, but I recommend the work of John Cook on 'Skepticalscience' for anyone who does not want to trail through literature. However those who do, I will point in the direction of Meehl 2004, and the IPCC AR4.
This, however, is not the topic of this thread.
A fairly common complaint against climate scientists, among those who accept that it is happening, is that CO2 is being overhyped as a smoke-screen (puns intended) to distract attention from industrial processes and such, which often have far more toxic and dangerous by-products. That we are effectively focussing on CO2, and ignoring the rest. Carbon dioxide is responsible for the majority of the *warming*, but climate change is FAR more than just temperatures. It encompasses environmental compositions, changes to ecosystems, and pollution as a whole.
This thread is an attempt to dispel this misconception, by introducing the field of green chemistry. I am trying to show you the extent to which being environmentally conscious is adopted where it really matters: in the chemical industry.
The industrial production of chemicals is probably the most polluting action we ever do as a species. You end up with millions of tonnes of very toxic by-products, such as aluminium waste, carcinogenic solvents (benzene, for example), and in some cases even radioactive materials like technetium waste. A fairly dramatic example of this is the recent disaster in Hungary, where a million cubic metres of toxic red sludge leaked from an alumina plant, killed several people, and injured many more. It has also poisoned several rivers beyond repair and destroyed about 1000 hectares of land.
As well as being environmentally friendly, green chemistry aims to avoid disasters such as this by using fundamentally safer processes.
*Hélios~

02-Mar-2011 14:08:06 - Last edited on 02-Mar-2011 14:13:33 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
Post 1: Introduction
Post 2: Contents
Post 3: Green Chemistry
Post 4: The 12 principles
Post 5: The Purpose of Catalysis
Post 6: Solid Catalysts
Post 7: Enzymes and Bioengineering
Post 8: The ALMA Process
Post 9: Continued
Post 10: Reserve
Post 11: Reserve
Post 12: Reserve
Post 13: Reserve
Post 14: Reserve
Post 15: Reserve
Post 16: Reserve
Post 17: Reserve
Post 18: Reserve
Post 19: Reserve
Post 20: Conclusion
~Hélios~

02-Mar-2011 14:08:11 - Last edited on 02-Mar-2011 14:14:06 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
Green Chemistry
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Green chemistry, put simply, is a philosophy. It focuses on improving existing chemical processes to be as environmentally friendly as they can be. This can be by modifying reagents, methods, plant design, catalysts, and all manner of things. The field operates by 12 principles, which were compiled by Paul Anastas (of the EPA in 1998), and these are in the next post.
There are a few things in there which might be unfamiliar to non-chemists, but the message is clear. Reduction of waste, reducing the number of reaction steps, using less energy, creating less waste, and so on. Every single chemical company these days is seeking to apply these principles to their production lines, as not only does it make their operations as environmentally friendly as possible, it actually SAVES money in most cases. This is because the principles involve using less energy, and less materials.
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EDIT: Apologies, principle 12 would not fit in the below post. Here is is:
12.INHERENTLY SAFER CHEMISTRY FOR ACCIDENT PREVENTION
Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions, and fires.
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~Hélios~

02-Mar-2011 14:08:14 - Last edited on 03-Mar-2011 22:38:46 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
The 12 principles
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1. PREVENTION
It is better to prevent waste than to treat or clean up waste after it has been created.
2. ATOM ECONOMY
Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
3. LESS HAZARDOUS CHEMICAL SYNTHESES
Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
4. DESIGNING SAFER CHEMICALS
Chemical products should be designed to effect their desired function while minimizing their toxicity.
5. SAFER SOLVENTS AND AUXILIARIES
The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
6. DESIGN FOR ENERGY EFFICIENCY
Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
7. USE OF RENEWABLE FEEDSTOCKS
A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
8. REDUCE DERIVATIVES
Unnecessary derivatization (use of blocking groups, protection/ deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible, because such steps require additional reagents and can generate waste.
9. CATALYSIS
Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
10. DESIGN FOR DEGRADATION
Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
11. REAL-TIME ANALYSIS FOR POLLUTION PREVENTION
Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.

02-Mar-2011 14:08:19 - Last edited on 02-Mar-2011 15:41:06 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
The Purpose of Catalysis
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Chemical reactions proceed by forcing two materials together into an unfavourable transition state, before a tipping point is reached and the products are formed. You can think of this as pushing a boulder up a hill. Once you reach the top of the hill - the most unfavourable position - and push it over the crest, it will roll down the other side of its own accord. You must put energy in to 'activate' it and trigger this change.
For a lot of reactions, the energy you need to put in like this is extremely high. Some reactions do not proceed at all at any temperature, because some other reaction has a lower activation energy and this one just proceeds instead of the one you want. Or you completely decompose your materials. Anyway we usually input energy by using heat, as heat is energy. A lot of reactions require temperatures of hundreds of degrees or more to proceed at an appreciable rate, which of course is very energy intensive. That energy has to come from somewhere, and that is usually from burning fossil fuels - thus contributing to climate change and driving up costs.
What a catalyst basically does is give you an alternative route for a reaction, by giving you a more favourable transition state. It may even make the reaction proceed by a completely different route. The upshot of this is that it makes reactions much faster, makes them require lower temperatures, and reduces the need for what are called 'stoichiometric reagents'. These are things which are consumed in the reaction and can contribute significantly to the waste.
Anyway, a catalyst is only a catalyst if it is *not* used up in the reaction itself. This means that one catalyst molecule can potentially catalyse millions of molecules, making it a very attractive method for industry.
~Hélios~

02-Mar-2011 14:08:19 - Last edited on 02-Mar-2011 14:16:33 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
Solid Catalysts
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Catalysts like I have described above have traditionally been homogeneous. That is, they are dissolved in the same liquid which the reaction takes place in. They do work very well, but in this form they can present a number of problems.
Firstly, there is the problem of separation. It is extremely difficult to get the catalyst out of the reaction mixture at the end, especially on an industrial scale. So while it is a catalyst, it is often thrown away with the waste or sometimes even left in the product. In fact, regular sticky plasters (band-aids) often have traces of platinum in their linings, as platinum is used as a catalyst in the reaction which produces them and it is just too difficult to remove.
But chemists are resourceful fellows, and we have a way around these problems. The use of solid and insoluble catalysts. You can take a metal and imprint it into a solid with an extremely high surface area, and then perform the reaction in the presence of this. You will get your products, and removal of the catalyst is as simple as filtering it off.
A tremendous amount of work has been done in this area, and among the best materials for this are zeolites. Zeolites are made out of sand, effectively. You take silicon oxide and a little aluminium oxide and crystallise them together, making a structure with a massive surface area. Zeolites typically have the surface area of a football field in just one spoonful of the material. Your reactive materials can diffuse into this, and interact with the metals you have imprinted inside, and this works very well as a catalyst.
There are a few downsides to solid catalysts as opposed to homogeneous catalysts, mainly due to the slower diffusion rates, but on the whole they provide a far more friendly way to perform reactions.
~Hélios~

02-Mar-2011 14:08:20 - Last edited on 02-Mar-2011 14:16:45 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
Enzymes and Bioengineering
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This is a relatively new field, which has popped up since our understanding of genetics and the genome has flourished.
I'll start off by saying that Nature is brilliant. Evolution over millions of years has produced thousands of enzymes, which are used to perform reactions we could only dream of doing. What our body can do in a water-rich environment, at 35ish degrees, far surpasses what the grandest chemical plants can achieve. This is all down to the enzymes.
An enzyme is a type of catalyst, made in living systems out of amino acid chains. They are incredibly large molecules, often weighing thousands of times more than regular molecules, and they are very highly folded and can be thought of as being like a ball of string. They have a hole in the side though. A very specifically-shaped hole which creates just the right conditions for a transition state (as discussed earlier) to form. This means that each enzyme can only catalyse one specific reaction, for one specific molecule. They are the ultimate in fine tuning.
What we can do as chemists, is extract these enzymes and use them in chemistry to catalyse the reactions they perform in our bodies, on a large scale in chemical plants. This brings all of the benefits of enzymes to industrial processes, and means that a tremendous amount of waste and energy is saved.
Biologists, with the new advances in genetics, are able to actually modify the genome of bacteria and such to produce very specific enzymes and specific properties, and then we can use this bacteria to perform the reactions. For example insulin, a vital hormone which is lacking in diabetic people, is commonly produced by bacteria now. To produce this molecule using regular chemistry would likely take thousands of steps, each one would require separation and would give side products. It would be an absolute nightmare to try and do this without the bacteria.
~Hélios~

02-Mar-2011 14:08:20 - Last edited on 02-Mar-2011 14:16:58 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
The ALMA Process
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This is a case study, an example of sorts, of the history of a very specific reaction. ALMA stands for Alu(censor)suisse Lummus Maleic Anhydride, which is quite a mouthful. Alu(censor)suisse and Lummus are the companies who collaborated to produce this, and Maleic Anhydride is the chemical produced. It is an extremely useful one, and has many further reactions.
Originally, maleic anhydride was manufactured from benzene. As said earlier, benzene is a carcinogen (meaning it is known to cause cancer) and is otherwise very toxic in other regards. A thoroughly nasty chemical to deal with, and this requires some very specific and high-energy equipment to safely handle and react. Furthermore benzene has 6 carbon atoms while maleic anhydride has 4, meaning that for every molecule you produce you are wasting two carbon atoms. These go out as waste.
The reaction also gives out a lot of heat, and this is very problematic in a reactor as it can lead to hot spots, and then potential explosions. The reaction requires a lot of heat anyway, which is very energy-intensive. Altogether this is a terrible reaction. Something had to change.
This is where the ALMA process comes in.
The most important shift in the ALMA process was the use of butane as a starting material instead of benzene. Butane is far less problematic than benzene to work with, meaning a cheaper plant is needed and the whole process is far less energy-intensive. It also results in less waste, as all four carbon atoms in butane end up in the final product.
(continued in next post)
~Hélios~

02-Mar-2011 14:08:21 - Last edited on 03-Mar-2011 22:38:28 by Helios223

Helios223

Helios223

Posts: 21,708 Opal Posts by user Forum Profile RuneMetrics Profile
Continued
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The first stage in the transformation of this reaction was finding a new catalyst. The new one chosen is called vanadyl pyrophosphate, which is rather cheap to produce. It is vanadium-based which is not an expensive metal, and it is very powerful and able to perform the reaction very well. It is also a solid, which brings all the benefits discussed above about separation. This reaction is actually performed as a continuous process where butane is flowed over beads of the catalyst, which is an extremely energy-efficient way of doing it.
From all of this, a new and much more eco-friendly plant design was put together and eventually created. It is also a significant cost-reduction on the previous method. Processes like this are being discovered all the time in green chemistry. New ways of performing old reactions. This is just one example which I learned of recently as part of a module and thought it relevant.
~Hélios~

02-Mar-2011 14:08:22 - Last edited on 02-Mar-2011 14:38:48 by Helios223

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