Cold property

On the other hand, in order to preserve the cold properties of the fuel (Cloud Point, Pour Point and low-temperature filterability), it is mandatory not to increase the melting point, that in turn depends on both the saturated compound (stearic acid, C18 0) content and the extent of cis/trans and positional isomerization as the difference in melting point between the cis and trans isomer is at least 15°C according to double bond position as shown in Table 1. 

This prompted us to investigate the possibility of selectively hydrogenate highly unsaturated oils, unsuitable for the production of Biodiesel, in order to improve their oxidative stability while keeping the cold properties. 

A comparison test carried out over a commercial Ni catalyst showed that early formation of stearic acid (C18 0) results in a very high pour point, thus indicating that very high selectivity is required to improve oxidative stability while retaining cold properties. 

As soon as a treatment principle is established, the composition plan and treatment strategies can be arranged. For instance, to treat the syndrome of excess heat in the Lung and Stomach, one would first prescribe herbs that have sweet-cold, bitter-cold or salty-cold properties, and which have the functions of clearing heat and reducing fire in the Lung and Stomach. Second, herbs that are sweet and cold and that can nourish body fluids and protect the Yin, which has been severely consumed by the excess heat, should be selected. Herbs that can tonify the Qi should be selected if the Qi is weakened severely by the heat. Herbs that moderate the actions of the harsh herbs in the formula, and reduce their side effects, should also be added. 

Bai Shao Yao is sour and cold, and primarily enters the liver meridian. The sour and cold properties can generate the Yin. It can be used in formulas that warm the Yang so as to protect the Yin from hot and pungent herbs. Moreover, its sour taste can stabilize the Yang and the Qi, as well as moderating the speed of the pungent and hot herbs. 

Bai Shao Yao is bitter, sour and slightly cold. It enters the Liver and Spleen meridians. Its sour and cold property can nourish the Yin directly and generate the substantial part of the blood. It is particularly effective for softening the Liver, thereby relieving cramp of the muscles and tendons. It can also effectively moisten the internal organs and the orifices, so it can treat the symptoms of dryness of skin and eyes caused by Liver-blood deficiency. 

These three substances are able to nourish blood and moisten dryness. E Jiao can directly stop bleeding. Bai Shao Yao can stabilize the blood due to its sour and cold properties. These substances are often used in the formula to treat bleeding due to blood deficiency. 

In this formula, herbs are selected with pungent, bitter and cold properties to treat Bi syndrome. 

Since the herbs that stop bleeding have sour, astringent and cold properties, they may cause blood stagnation and complicate the syndrome. Formulas that stop bleeding should not be used for a long period of time. 

Bai Shao Yao is sour, bitter and slightly cold. It can generate the blood and Yin. This function can be enhanced by sweet herbs. In addition, its bitter and cold properties can clear heat and reduce empty-heat in the blood caused by deficiency of blood and Yin. In this way, the blood can circulate in a moderate way. Bai Shao Yao is often used as deputy in the formula to tonify the substantial part of the blood and Yin and reduce heat. 

However, one of the limitations of using biodiesel fuel for diesel engines is higher cold flow properties compared with petroleum diesel fuel (4). Cold properties consist of cloud point, pour point, and cold filter plugging point. The cloud point is a temperature at which the fuel starts to thicken and cloud, the pour point is a temperature at which the fuel thickens and no longer pours, and the cold filter plugging point is the lowest temperature at which fuel still flows through a specific filter. These... 

Cold properties of biodiesel are highly correlated to the fatty acid composition. Biodiesel with a high content of saturated fatty acids, such as that from palm oil and coconut oil, possesses poor cold flow properties. On the other hand, biodiesel with a high content of unsaturated fatty acids possesses better flow properties at lower temperatures. However, biodiesel from highly unsaturated fatty acids with more than two double bonds has combustion problems. Therefore, in some countries, the content of highly unsaturated fatty acid methyl esters in biodiesel is kept low (5). 

To improve the cold properties of biodiesel, the use of alcohol with longer alkyl chain has been studied in the alkaline-catalyzed method. The cloud point for ethyl esters is approx 2°C lower than that of the corresponding methyl esters, while butyl esters are 10°C lower than methyl esters (6). Furthermore, cetane number is appropriate for alkyl esters from the alcohol with the longer alkyl chain (7). 

We have developed a catalyst-free method of biodiesel fuel production by supercritical methanol (10-12), and we found that the process becomes much simpler and that the yield of biodiesel is higher compared with the alkaline-catalyzed method. The aim of the present work was, therefore, to investigate the possibilities of biodiesel fuel production from rapeseed oil with various alcohols by supercritical treatment. In addition, the super-critically prepared biodiesel fuel was studied for its cold properties. 

To be acceptable, the ester must meet certain specifications (in Europe EN14214). The critical specifications are related to the cold properties and stability. These specifications limit the choice of starting vegetable oils, as discussed below. In Europe, rapeseed and oleic sunflower oils are used, in Brazil soybean oil. 

The Young s bending modulus is a measure of the stiffness of a material—a higher value indicates a stiffer material. The sodium polybutadiene is, of course, considerably inferior to both of these polymers in this low temperature test. Table IV similarly illustrates the superiority, in compounded stocks, of lithium polybutadiene in low temperature shear recovery tests, also a measure of cold properties of a rubber. In this test the relative superiority of the lithium polymers to the emulsion and sodium polymer is even greater than that in the former test. 

However, the excellent cold properties of the lithium polymer can be explained on the basis of microstructure in Table II. It seems reasonable to assume that of the three possible microstructures the 1,2 structure is the least desirable for low temperature flexibility followed by the frans-1,4 structure, with the cis-1,4 structure the most desirable. A comparison of the low temperature flexibility of balata (or gutta-percha) vs. Hevea rubber would indicate a preference for the cis-1,4 structure over the trans-1,4 structure, although these natural products are polyisoprenes rather than polybutadienes. In the case of the 1,2 structure, it is generally assumed that the prevalence of this structure in sodium-catalyzed polybutadiene, or butadiene copolymers, accounts for its poor cold properties however, the occurrence of a natural or synthetic product with an entirely 1,2 structure would help to confirm this more definitely. The relative predominance of any single structure is another important consideration in the performance of a rubber at low temperatures because a polymer with a large percentage of one structure would be more likely to crystallize at a low temperature. 

The factors mentioned above adequately explain the superior cold properties of the lithium-catalyzed polybutadiene. Compared to emulsion polybutadiene, the lithium-catalyzed polybutadiene has more of the cis-1,4 structure and less trans-1,4 and 1,2 structures. All of these changes are in the direction to increase the relative amounts of more desirable microstructures, at least from the standpoint of cold properties. In addition, there is also a decrease in the predominant structure, trans-1,4, compared to the emulsion polybutadiene. Therefore, it would be less crystalline or orient less. 

The superior cold properties of lithium polymers were even more pronounced in the case of butadiene-styrene copolymers than in the poly butadienes. As Figure 2 shows, a butadiene-styrene copolymer (33% styrene) prepared with lithium outperformed LTP (23.5% styrene, emulsion recipe, 5°C.) by 21 °C. in regard to the temperature at which Young s bending modulus reaches 10,000 pounds per square inch. The fact that the lithium polymer had a higher styrene content and also a higher Mooney viscosity (130 vs. 49) than LTP should have affected its cold properties adversely therefore, the superior performance of the lithium copolymer is significant. 

Density — Sulfur — Mercaptans — Octane — FIONA — Chromatography — Density — Sulfur — Viscosity — Cetane — Cold properties — Aniline — Aromatics — Nitrogen — Density — Sulfur — Viscosity — Refractive Index — Cold properties — Aniline — Nitrogen — Metals — Asphaltenes — Carbon residue — Density — Sulfur — Viscosity — Carbon residue — Cold properties — Metals — Asphaltenes — Asphalt properties ... 

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