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Propane Fuel Basics

Also known as liquefied petroleum gas (LPG) or propane autogas, propane is a clean-burning alternative fuel that's been used for decades to power light-, medium-, and heavy-duty propane vehicles.

Propane is a three-carbon alkane gas (C3H8). It is stored under pressure inside a tank as a colorless, odorless liquid. As pressure is released, the liquid propane vaporizes and turns into gas that is used in combustion. An odorant, ethyl mercaptan, is added for leak detection. (See fuel properties.)

Propane has a high octane rating, making it an excellent choice for spark-ignited internal combustion engines. If spilled or released from a vehicle, it presents no threat to soil, surface water, or groundwater. Propane is produced as a by-product of natural gas processing and crude oil refining. It accounts for about 2% of the energy used in the United States. Of that, less than 3% is used for transportation. Its main uses include home and water heating, cooking and refrigerating food, clothes drying, and powering farm and industrial equipment. The chemical industry also uses propane as a raw material for making plastics and other compounds.

Propane as an Alternative Fuel

Interest in propane as an alternative transportation fuel stems from its domestic availability, high-energy density, clean-burning qualities, and relatively low cost. It is the world's third most common transportation fuel, behind gasoline and diesel, and is considered an alternative fuel under the Energy Policy Act of 1992.

Propane used in vehicles is specified as HD-5 propane and is a mixture of propane with smaller amounts of other gases. According to the Gas Processors Association's HD-5 specification for propane, it must consist of at least 90% propane, no more than 5% propylene, and 5% other gases, primarily butane and butylene. (See fuel properties.)

For vehicle fueling, the quick-release "Type K15" dispenser connector is required to be installed on all new vehicles beginning January 1, 2020, per National Fire Protection Association Code 58. This connector allows for one-handed fueling and does not require the use of personal protective equipment such as gloves and face shield (which are required for the older style connector).

Propane is stored onboard a vehicle in a tank pressurized to about 150 pounds per square inch—about twice the pressure of an inflated truck tire. Under this pressure, propane becomes a liquid with an energy density 270 times greater than its gaseous form. Propane has a higher octane rating than gasoline, so it can be used with higher engine compression ratios and is more resistant to engine knocking. However, it has a lower British thermal unit rating than gasoline, so it takes more fuel by volume to drive the same distance.

Why is dichloromethane a good solvent?

Dichloromethane is an organic solvent and therefore it can dissolve many non-polar organic molecules (establishing London type interactions). However, it has a large dipole moment (see figure) and therefore it can also dissolve polar molecules (with London type interactions and dipole-dipole interactions). Because of the high dipole moment, it is a good non-aqueous solvent for chemical reactions involving polar molecules.

Adipic Acid

Adipic acid, or more formally hexanedioic acid, is a white crystalline solid that melts at 152 oC. It is one of the most important monomers in the polymer industry.

Adipic acid is found in beet juice, but the article of commerce—≈2.5 million tonnes of it per year—is manufactured. In 1906, French chemists L. Bouveault and R. Locquin reported that adipic acid can be produced by oxidizing cyclohexanol. Today, the most common manufacturing process is the nitric acid (HNO3) oxidation of a cyclohexanol–cyclohexanone mixture called KA (for ketone–alcohol) oil.

Almost all adipic acid is used as a comonomer with hexamethylenediamine to produce nylon 6-6. It is also used to manufacture other polymers such as polyurethanes.

ethanol

ethanol, also called ethyl alcohol, grain alcohol, or alcohol, a member of a class of organic compounds that are given the general name alcohols; its molecular formula is C2H5OH. Ethanol is an important industrial chemical; it is used as a solvent, in the synthesis of other organic chemicals, and as an additive to automotive gasoline (forming a mixture known as a gasohol). Ethanol is also the intoxicating ingredient of many alcoholic beverages such as beer, wine, and distilled spirits.

There are two main processes for the manufacture of ethanol: the fermentation of carbohydrates (the method used for alcoholic beverages) and the hydration of ethylene. Fermentation involves the transformation of carbohydrates to ethanol by growing yeast cells. The chief raw materials fermented for the production of industrial alcohol are sugar crops such as beets and sugarcane and grain crops such as corn (maize). Hydration of ethylene is achieved by passing a mixture of ethylene and a large excess of steam at high temperature and pressure over an acidic catalyst.

There are two main processes for the manufacture of ethanol: the fermentation of carbohydrates (the method used for alcoholic beverages) and the hydration of ethylene. Fermentation involves the transformation of carbohydrates to ethanol by growing yeast cells. The chief raw materials fermented for the production of industrial alcohol are sugar crops such as beets and sugarcane and grain crops such as corn (maize). Hydration of ethylene is achieved by passing a mixture of ethylene and a large excess of steam at high temperature and pressure over an acidic catalyst.

Ethanol produced either by fermentation or by synthesis is obtained as a dilute aqueous solution and must be concentrated by fractional distillation. Direct distillation can yield at best the constant-boiling-point mixture containing 95.6 percent by weight of ethanol. Dehydration of the constant-boiling-point mixture yields anhydrous, or absolute, alcohol. Ethanol intended for industrial use is usually denatured (rendered unfit to drink), typically with methanol, benzene, or kerosene.

Maleic anhydride (CAS 108-31-6) derives from natural malic acid. Maleic anhydride as well as maleic and fumaric acids were first prepared in the 1830s. However, commercial manufacture did not begin until a century later. In 1933, the National Aniline and Chemical Co., Inc., used a process for producing maleic anhydride based on benzene oxidation using a vanadium oxide catalyst. Advances in catalyst technology, increased regulatory pressures, and continuing cost advantages of butane over benzene have led to a rapid conversion of benzene- to butane-based plants. By the mid-1980s in the United States, 100% of maleic anhydride production used butane as the feedstock.

At room temperature, maleic anhydride is a white crystalline solid with an acrid odor, but is a liquid or gas during chemical production. Two acid carbonyl groups and a double bond appear in its formula, which make it useful for broad industrial applications. Manufacturing processes for maleic anhydride include those using fixed-, fluidized-, and transport-bed technologies for selective oxidation of butane.

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