Argentine Chemists report method for reducing the cloud point of biodiesel.

[NNadir]

Biodiesel has lately emerged as an alternative fuel of wide acceptance because of its higher cetane number and lubricity and its lower environmental impact as compared to diesel petroleum fuels.1,4 Remarkable reductions in emissions other than nitrogen oxides2,3 and an increase in lubricity have been reported with neat biodiesel or biodiesel/diesel fuel blends. Biodiesel does not contain harmful aromatic hydrocarbons, and it does not produce sulfur oxides (SOx). Particulate emissions are also decreased. Additionally, biodiesel has the appeal of being made from renewable resources and it is biodegradable.5 It can be produced by transesterification of soybean oil, rapeseed oil, canola oil, or other vegetable oils with methyl alcohol.6,7 Lard, tallow, and animal fats can also be transesterified, but their use is less common.8

The use of biodiesel is however limited despite its significant environmental benefits. The cost of producing biodiesel is greater than the cost of producing petrodiesel. Cold flow properties are also a concern when the temperature of operation goes below 10 °C. Problems with biodiesel often develop from plugged fuel lines and filters, and these problems are caused by the formation of crystals. Methyl and ethyl esters of fatty acids have considerably higher crystallization temperatures than diesel fuel. Crystal growth inhibitors for diesel fuel, also known as pour point depressants (PPD), are available commercially.9 Though they have been reported to reduce the pour point of biodiesel, these additives usually do not reduce the cloud point nor improve the filterability of biodiesel at low temperatures.10 The use of PPD (e.g., polymethacrylate or ethylene vinyl acetate) admixed in levels of about 1-2% also increases the price of the fuel...

...Lee et al.14 have reported the reduction in the crystallization temperature of biodiesel by 7-14 °C by the use of branched alcohols in the synthesis of the methyl fatty acid esters of the fuel. methyl, ethyl, propyl, isopropyl, 2-butyl, tert-butyl, and neopentyl esters were synthesized from soybean oil, canola oil, lard, and tallow. In all cases, the crystallization temperatures of the methyl esters were significantly higher than those of the branched esters...

...As indicated in recent studies,15,16 the cloud point is highly related to the fatty acid composition of biodiesel. High percentages of saturated fatty acids of long and linear chains are responsible for high cloud points. Skeletal branching of biodiesel is studied in this work as a simple means of improving its cold flow properties. The branching is supposed to disrupt the van der Waals interaction between the long straight chains of fatty acid methyl esters...

A zeolite based catalyst was used and the cloud point of the biodiesel in question was reduced to -2C.

[John Q. Citizen]

1. What is zeolite?

[NNadir]

2. Zeolites are minerals that have a structure with lots of holes into which ions fit.

Originally all zeolites were obtained from natural sources, but synthetic zeolites have now been synthesized.

They are important in many technological applications, particularly catalysis, since they allow incorporated materials to present themselves on a large surface.

[John Q. Citizen]

7. About five years ago I used to spend lots of time on a bio-diesel discussion board.

While I have no strong background in chemistry, I saw that the public policy initiatives (clean air act) and the utility of bio-diesel presented some interesting opportunities.

I live in Montana so of course cloud point is an issue.

In my reading I discovered that about 75% of the cost of operating a bio-diesel plant is feedstock. One of the best models I saw involved trading out farmers bio-diesel for feedstock, specifically rape seed, which is very well suited for northern wheat growing regions. In fact there is already a utilized crop rotation for wheat which involves growing wheat one year, growing a cover crop the following year (such as rape) and then fallow for a year. With a barter model it significantly lowers feedstock/operating costs and also lowers marketing costs.

One of the more promising conversion methods I saw came from a home bio-diesel researcher in Romania I think it was. He had a method for more complete conversion of feedstock to bio-diesel by using an acid catalyst first (sulphuric acid) then neutralizing and washing and then using a typical methanol/lye catalyst conversion and then running his bio-diesel through a water bubbler to take out remaining impurities.

He said it worked very well, but of course in this climate the cloud point is still an issue. Any ideas on how to incorporate zeolites into this process to lower cloud point?

[NNadir]

8. Well, I can give you the experimental details from the paper, but I don't know

that it would be particularly useful.

You should know that not all oils are created equal. Rapeseed has a different chemical composition than soy oil. The source oil does have an effect on cloud point. Thus if you are using rapeseed oil you may have a different result than if you are using soy oil. Some of these differences have lead to some difficulties. Volkswagen at one time - I don't know if it is still the case - was voiding warranties on vehicles fueled with American soy based biodiesel based on the American fuel specifications. European biodiesel tends to be rapeseed derived or, many times, imported palm oil based.

The paper refers to soy oil prepared by the traditional lye method.

The best zeolite catalyst was a synthetic zirconium based zeolite. Here is a description of the catalyst preparation.

Zirconium hydroxide was prepared by precipitation of ZrOCl2â8H2O (Strem Chemicals, 99.99%) first dissolved in water. Ammonia was added dropwise until a pH of 10 was reached. The Zr(OH)4 gel formed was then filtered and dried overnight at 110 °C. The dried xerogel was sulfated by immersing it in a 2 N H2SO4 (10 mL gcat -1) solution for 1 h. Then, it was calcined in air (10 mL min-1, 600 °C, 3 h). The thus produced SO4 2--ZrO2
catalyst was dried overnight and finally ground and sieved to 35-80 meshes.

According to the paper, the best result was obtained by stirring this catalyst vigorously with nitrogen flushing in a stainless steel autoclave at 150C for 1 hour. The catalyst was filtered and the biodiesel's cloud point was reduced to -2C, just below the freezing point of water. I'm sure you have colder days than that in Montana.

If I were you, I wouldn't necessarily try this at home. It might be simpler to use B100 in summer and B20 or B5 in winter.

If you do try this, come back and let us know how it worked out. My guess is that biodiesel is overall a better deal than ethanol, but officially I'm agnostic about biofuels.

[John Q. Citizen]

9. Thanks.

[NNadir]

10. My pleasure. n/t

[phantom power]

11. That brings back some memories

I once worked on experiment design algorithms for catalyst discovery. Although I came up with useful algorithms for important subsets of the experiments, the full breadth of the problem is nearly impossible to solve, chiefly because catalyst preparation is such black magic. I would be interviewing the chemists, trying to extract some kind of "universal" data structure for describing a catalyst prep. Heh. Good luck.

"First, you soak the zeolite in eye of newt for 30 seconds. Except in these other experiments, where we tried rinsing with snail extract and then soaking in eye of newt. And oh, there was those other experiments where we then heated the prep to 1500K for 14.35 minutes in an atmosphere of pure vaporized mercury..."

Try to design an optimal coverage placement over the set of strings of symbols with arbitrary length, and where they get to make up new symbols every day. :banghead:

Comparatively speaking, the ion mixture designs were easy. Comparatively.

[NNadir]

12. Chemistry has always been an experimental science.

There is, of course, lots of very nice theory in chemistry, but there is still no substitute for trying things out.

[eppur_se_muova]

3. No 1-butyl esters for comparison? (1-butanol is readily available by fermentation.)

True, they'r not branched, but we don't know that's the only thing that matters. Methyl esters are often anamolously high-melting -- look at dimethyl vs diethyl oxalate.

[NNadir]

4. I think the 1 butyl esters are very waxy, and have a high melting point.

In an engine, this is not good.

[eppur_se_muova]

5. Bummer. Another beautiful idea slain by ugly facts. nt

[NNadir]

6. Well, if it makes you feel better, the t-butyl and sec-butyl esters are useful

in exactly the way you suggest. They are, regrettably, more expensive though.