Introduction to n-heptane:
Content: 97%
Package: 137kg / barrel
CAS No.: 142-82-5
Chinese Name: n-heptane
Alias: heptane
Molecular formula: C7H16; ch? (CH?) 5CH?
Appearance and character: colorless and volatile liquid
Molecular structure: C atom is bonded with SP3 hybrid orbital and the molecule is nonpolar.
Molecular weight: 100.21
Steam pressure: 5.33kpa/22.3 ℃
Flash point: – 4 ℃
Density: relative density (water = 1) 0.68;
Relative density: (air = 1) 3.45
Stability: stable
N-heptane is a colorless and volatile liquid, which is often used as the standard and solvent for octane number determination, as well as for organic synthesis and preparation of experimental reagents.
Storage precautions:
Store in a cool and ventilated warehouse. Keep away from fire and heat sources. The storage temperature should not exceed 30 ℃. Keep the container sealed. It should be stored separately from oxidant and should not be mixed. Explosion proof lighting and ventilation facilities are adopted. It is forbidden to use mechanical equipment and tools that are easy to produce sparks. The storage area shall be equipped with leakage emergency treatment equipment and appropriate materials.
The price and quantity of n-heptane, a domestic and imported organic chemical raw material, is favorable
Industrial grade n-heptane; price of high quality organic chemical raw material heptane in national standard
Application of n-heptane: organic synthesis, pharmaceutical solvent, cleaning agent, determination of anti riot value, etc. N-heptane is an organic compound with the chemical formula C7H16. It is a colorless, volatile liquid. It is mainly used as the standard substance for the determination of octane number, as well as the preparation of anesthetics, solvents, raw materials for organic synthesis and experimental reagents.
Organic synthesis refers to the process of making simple substance, simple inorganic substance or simple organic matter into complex organic matter by chemical method. For example, methanol is prepared from hydrogen and carbon dioxide; vinyl chloride is prepared from acetylene and then polymerized to obtain polyvinyl chloride resin; adipic acid and hexanediamine are prepared from phenol through a series of reactions, and then condensed into polyamide 66 fiber. At present, most organic compounds such as resin, rubber, fiber, dye, medicine, fuel and perfume can be synthesized by organic synthesis.
In 1828, F. Weiler synthesized urea, an animal metabolite, from the inorganic ammonium cyanate. A few years later, H. Colby synthesized acetic acid. From then on, organic synthetic chemistry developed rapidly. Organic synthesis can be divided into two aspects: ① basic organic synthesis. Including coal, oil, water, air and other raw materials to synthesize important chemical industrial raw materials, such as synthetic fiber, plastics and synthetic rubber raw materials, solvents, plasticizers, gasoline, etc., its output is nearly the order of magnitude of steel. ② Fine organic synthesis. It includes the synthesis of compounds with more complex molecules from simpler raw materials, such as chemical reagents, pharmaceuticals, pesticides, dyes, perfumes and detergents. Since the 1970s, new fields of organic synthesis have developed rapidly, such as the synthesis of natural complex molecules with certain stereoconformation, and some new theories and methods, such as reaction mechanism, conformation analysis and photochemistry, The progress in the application of various physical methods, especially the principle of conservation of molecular orbital symmetry, has greatly promoted the organic synthesis chemistry.
Background and overview] [1] [2]
Heptane is heptane, CAS No. 142-82-5, molecular formula C7H16, molecular weight: 100.20200, PSA: 0.00000, logP: 2.97670. Melting point 130 ° c-4h2o. Colorless liquid. The results showed that the density was 0.71g/ml at 20 ° C, melting point − 91 ° C (lit.), boiling point 98 ° C (lit.), flash point 30 ° F, refractive index N20 / D 1.397. The storage conditions were room ventilation, low temperature and dry, separated from oxidants and acids, partially soluble in water, vapor pressure 45.2mmhg at 25 ° C, vapor density 3.5 (vs air). Highly flammable liquids and vapors can cause skin irritation. Swallowing and entering the respiratory tract may be fatal. It can cause drowsiness or dizziness. It is highly toxic to aquatic organisms and has a long-term lasting impact. If skin contacts, you should take off the contaminated clothes and wash the skin thoroughly with soapy water and water. If you have discomfort, see a doctor. If your eyes are in clear contact, you should separate the eyelids and use flowing water or Rinse with normal saline and seek medical advice immediately; gargle immediately if ingested, do not induce vomiting, and seek medical advice immediately. The advice to protect the rescuer is as follows: transfer the patient to a safe place and consult the doctor. If conditions permit, please show the safety technical specification of the chemical to the doctor at the scene. If it leaks, small leakage can be collected as much as possible in a closed container, absorbed by sand, activated carbon or other inert materials, and transferred to a safe place. No water is allowed to be washed into the sewer. If a large number of leaks are found, a dike or pit will be installed to seal the drainage pipe, cover with foam, inhibit evaporation, and use explosion-proof pump to transfer to the tank or special collector for recovery or transportation. To the waste disposal site.
[cracking mechanism] [3]
The atmospheric pressure cracking of n-alkanes has been widely studied. It is generally believed that the cracking process of n-heptane under supercritical conditions can be inferred according to the chain reaction mechanism initiated by free radicals
The cracking products mainly include methane, ethane, ethylene, propane, propylene, n-butane, 1-butene, 1-hexene and coke. In the temperature range studied, with the increase of reaction temperature, the cracking conversion of n-heptane is greatly increased. The secondary reaction of cracking products (olefin polymerization, cyclization and proton elimination) increases the amount of coking precursors, which eventually leads to serious coking. Under supercritical conditions, it is a simple and effective method to reduce the residence time of precursors on the surface of reaction tube by increasing the turbulence of fluid. The results of solid product analysis show that the main coking of n-heptane is filamentous coke produced by metal catalysis. The growth of filamentous coke is an important reason for carburization of stainless steel materials. Inhibiting the growth of filamentous coke can effectively maintain the mechanical strength of stainless steel at high temperature and prolong its service life. When n-heptane is heated, the carbon carbon bond breaks and two free radicals are formed, which leads to chain reaction. The free radicals are very active and prone to isomerization, β – cleavage, proton elimination and hydrogen transfer reactions. In addition, with the increase of temperature, the coking amount increases rapidly, which is because the cracking conversion of n-heptane is greatly increased, and the secondary reaction (olefin polymerization, cyclization, proton elimination) of pyrolysis products increases, which leads to the increase of coking precursors, and finally leads to serious coking. It is generally believed that cycloalkanes, cycloolefins and aromatics are the main coking precursors.
[preparation] [1] [2]
1. The content of n-heptane in the fraction of Pt reforming raffinate (93-102 ℃) is more than 57%. The n-alkanes are adsorbed on 5A molecular sieve gas phase, and then desorbed by steam to obtain n-alkanes. A small amount of n-alkenes were saturated and converted into n-alkanes by nickel catalytic hydrogenation, and the iodine value was below 0.1g iodine / 100g. Finally, standard n-heptane with purity of 99.9% was obtained by distillation. Industrial grade n-heptane can also be purified by concentrated sulfuric acid washing and methanol azeotropic distillation.
2. Hydrocarbon fraction of petroleum. It can contain n-heptane, dimethylcyclopentane, 3-ethylpentane, methylcyclohexane and 3-methylcyclohexane.
3. In addition to alkanes and cycloalkanes with similar boiling points, heptane also contains unsaturated compounds, water and benzene. Benzene is removed in the same way as hexane. Unsaturated hydrocarbons can be removed by washing with concentrated sulfuric acid. Calcium chloride, phosphorus pentoxide, sodium and potassium can be used to remove water, and molecular sieve can also be used as solid desiccant. Finally, it is fractionated and refined.
4. Purification method of high purity organic solvent n-heptane, which is characterized by the following steps:
a. The raw material n-heptane is extracted by adding oxidant into the raw material for oxidation treatment, and then the n-heptane is distilled to remove the impurities of unsaturated hydrocarbon in the raw material n-heptane.
b. The distilled n-heptane is passed into an adsorbent column containing modified activated carbon for adsorption treatment, which is used to remove highly polarized substances and benzene containing substances formed in the process of oxidation and oxidation; namely, high-purity organic solvent n-heptane with purity ≥ 99% (WT) is obtained. Because the carbon carbon double bond contained in benzene ring and unsaturated hydrocarbon is the group which can absorb ultraviolet and visible light, the light transmission effect of n-heptane to remove benzene ring, unsaturated hydrocarbon and other organic compounds is also improved.
[purpose] [1] [2]
N-heptane is mainly used as standard and solvent for octane number determination, organic synthesis and preparation of experimental reagent. N-heptane is one of the widely used hydrocarbon solvents in industry. It is used as extraction solvent of animal and vegetable oil, fast drying rubber adhesive and rubber solvent. It is also used in cosmetics and as a solvent for cleaning coatings, paints, fast drying inks and printing machine parts. Industrial grade n-heptane is mostly obtained from petroleum fraction with low purity.
[References]
[1] Junyuan Petroleum Group Lab Report v20190986
[2] Fan Wenlin; Zhang Qunxing; Zhang Yi; Yang Yongnian. Purification method of high purity organic solvent n-heptane. Cn201410209265.2, application date: May 16, 2014
[3] Xie Wenjie, Fang Wenjun, Li Dan, et al. Cracking and coking of n-heptane under supercritical conditions [J]. Acta Chem Sinica, 2009, 67 (15): 1759-1764