How to purify n-Heptane?

Taking n-heptane as the model compound of alkanes in light straight run naphtha, the cracking reaction of n-heptane on HZSM-5 catalyst was studied and compared with the cracking reaction of 1-heptene. The effects of hydrothermal treatment and carrier properties on the cracking reaction were investigated The results show that the content of small molecular alkanes such as hydrogen, methane and ethane in n-heptane cracking products is much higher than that in 1-heptane cracking. It is speculated that it is mainly caused by the unique single molecular cracking path of alkanes, and the content of low-carbon olefins such as propylene and butene in liquefied gas (LPG) is low; After hydrothermal treatment, the amount of acid decreased sharply, and the relative content of strong B acid decreased, resulting in significant reduction of catalyst activity, reduction of hydrogen transfer reaction and significant increase of olefin degree in cracking gas At the same time, the molar ratio of C3 / C4 in the product decreased, which reduced the probability of inferring the single molecular path in the cracking reaction The carrier also has a great influence on the cracking reaction behavior of n-heptane. The presence of Lewis acid in the carrier can promote the conversion of n-heptane and increase the proportion of BIMOLECULAR CRACKING path in the initial reaction Generally speaking, compared with olefin molecules, alkanes have lower reaction activity and olefin selectivity, so they are not an ideal raw material for catalytic cracking on molecular sieve catalysts to produce low-carbon olefinsRemoving impurities from the heptane stream by contacting the heptane stream with an acidic catalyst, wherein the contact reduces the concentration of one or more near boiling impurities, one or more olefins, or both. Impurities are isomerized into substances with low octane number or boiling point not close to the boiling point of n-heptane through contact with acidic catalyst, which helps to separate impurities by distillation. Near boiling point impurities may include compounds such as cis-1,2-dimethylcyclopentane and methylcyclohexane, or compounds with boiling points in the range of about 96.5 to about 100.5 degrees Celsius at a standard pressure of 760 Torr, including compounds such as cis-1,2-dimethylcyclopentane and methylcyclohexane. The concentrations of cis-1,2-dimethylcyclopentane and methylcyclohexane can be reduced by at least 25% and 10% by weight, respectively. The olefin concentration measured by bromine index can be reduced by at least about 25% (by weight).

1. After nickel catalyzed hydrogenation, a small amount of normal olefins are saturated and converted into normal alkanes, and the iodine value is reduced to less than 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.

Light naphtha isomerization oil does not contain sulfur, aromatics, olefins and other substances. It is one of the blending components of clean gasoline with high octane number. Normal C5 and C6 isomerization in light naphtha is easy and has realized industrial production, while long-chain alkane isomerization represented by n-heptane is difficult. Once a breakthrough is made, it will bring great technological progress to the production of high octane number gasoline. Ptwo3 / ZrO2 Catalyst has the advantages of good thermal stability, strong acidity, simple preparation method, reusable and good isomerization performance. It has become a research hotspot of n-heptane isomerization catalyst. In this paper, Pt / WO3 / ZrO2 Catalyst was further modified by Cr and other metals to improve the performance of the catalyst in n-heptane isomerization. The main conclusions are as follows: (1) Pt / WO3 / ZrO2 Catalyst Modified by rare earth metals such as PR, CE, La and Rb and transition metals such as Cr, Co, Zn and Fe was prepared by impregnation method. The modified catalyst was characterized by XRD, NH3-TPD, bet, H2-TPR and SEM, Combined with the fixed bed reactor, the catalytic performance of the catalyst for n-heptane isomerization was analyzed and evaluated. The results show that among the above metal modified catalysts, Cr2O3 Pt / WO3 / ZrO2 Catalyst has large specific surface area and strong acidity, and shows better catalytic activity in n-heptane isomerization. (2) The effects of WO3 content, Cr content, calcination temperature and calcination time on the isomerization of n-heptane over Cr2O3 Pt / WO3 / ZrO2 Catalyst were investigated. The results showed that the isomerization performance of the catalyst was better when the load of WO3 was 18wt%, the content of Cr was 1.0wt%, the calcination temperature was 800 ℃ and the calcination time was 3H. At this time, the yield of isoheptane was about 73% and the conversion of n-heptane was about 82%. (3) The effects of reaction pressure, reaction temperature, molar ratio of hydrogen to hydrocarbon and space velocity reaction conditions on n-heptane isomerization over Cr2O3 Pt / WO3 / ZrO2 Catalyst were investigated. The results show that the catalytic performance is the best when the reaction pressure is 1.0MPa, the reaction temperature is 220 ℃, the molar ratio of hydrogen to hydrocarbon is 9 and the space velocity is 1.05 ~ 1.4h-1. The yield of n-heptane is about 75%. (4) The stability of Cr2O3 Pt / WO3 / ZrO2 Catalyst was investigated, and Cr2O3 Pt / WO3 / ZrO2 Catalyst was applied to the isomerization of light naphtha raw materials. The results showed that Cr2O3 Pt / WO3 / ZrO2 Catalyst did not inactivate after 500 hours of n-heptane isomerization, and the catalyst was stable; Cr2O3 Pt / WO3 / ZrO2 Catalyst has good isomerization performance in actual naphtha raw materials, and the octane number of chromatography is increased by about 28 units.