How is paraffin wax derived from petroleum?

2022-04-20   Pageview:895

The process of obtaining paraffin from petroleum is generally the lubricating oil fraction obtained by distilling petroleum, the paraffin obtained by dewaxing and deoiling process, and then refined and shaped to package into paraffin products.

Paraffin is derived from petroleum in this way:

The first step is distillation. In a refinery, crude oil is initially separated in a distillation unit. In the distillation column, the components of petroleum are divided into various fractions according to the boiling point range, such as gasoline fraction, kerosene fraction, diesel fraction, lubricating oil fraction (also called waxy oil fraction), etc. The lubricating oil fraction can be obtained by processing and separating lubricating oil and paraffin. Since paraffin wax wholesale and lubricating oil are products of the same fraction, the composition of hydrocarbons contained in paraffin wax depends on certain properties of the lubricating oil fraction. The boiling point range of the paraffin wax is basically the same as the boiling point range of the lubricating oil containing the paraffin wax. Since it is practically impossible for the wax deoiling process to completely remove the oil, the type of trace cyclic hydrocarbons and non-hydrocarbon impurities contained in the paraffin depends on the lubricating oil fraction.

The second step is oil wax separation. The more waxy lubricating oil fraction has a higher freezing point. In order to obtain a low freezing point oil, the wax must be removed. Likewise, only n-paraffins are desirable components of commercial paraffins in lubricating oils. Although it is impossible to obtain the solid paraffin of pure normal paraffins, it is necessary to remove various hydrocarbons such as naphthenic hydrocarbons, isoparaffins, aromatic hydrocarbons, etc., which exist as liquid oil in the fraction. At the same time, in order to obtain paraffin with a certain melting point, hydrocarbons with a lower melting point must also be separated from it. During processing, the separation of oil and wax is carried out according to the different freezing points of oil and wax or the different solubility of the solvent. In my country, the lubricating oil fraction is usually dewaxed first, and then the obtained wax paste is further deoiled to obtain paraffin with a certain melting point and hardness. However, it is best to first refine the lubricating oil fraction with solvent and then dewax. In this way, although the processing capacity of the solvent refining unit needs to be increased, the processing capacity of the dewaxing unit can be reduced, and the more important thing is to further improve the wax paste Deoiling and refining are more advantageous, especially when producing waxes for the food industry and medicine.

Dewaxing of waxy fractions can be done by pressing or solvent. Usually, the solvent used in the solvent dewaxing process is a mixture of methyl ethyl ketone and toluene. These solvents have a large solubility for oil at a certain freezing temperature, but a small solubility for wax. Dilution, the viscosity decreases, so when the oil is frozen to a certain temperature, the wax crystallizes out. The crystallized wax and oil can be separated by filtration. The oil obtained from the dewaxing of lubricating oil fractions is further refined to become lubricating oil. The separated wax is called wax paste. It is a mixture of paste wax and oil. Generally, the oil content is about 10% to 20%. Further deoiling is required to produce commercial paraffins.

For the deoiling of wax paste, two methods are often used in production: solvent deoiling and sweating deoiling. The process of solvent deoiling is to follow the solvent dewaxing process, add solvent to the filter cake obtained by solvent dewaxing, and filter at the temperature according to the specifications of the desired paraffin product to obtain crude wax with lower oil content, also known as dewaxing. Oil wax.

The third step is the refining of paraffin. After the wax paste is dewaxed and deoiled, the melting point and oil content have reached the quality index of commercial paraffin. But at this time, the wax generally also contains substances left over from the processing, mainly a little gum and asphaltene. In addition, traces of unstable olefin and aromatic polymers remain, as well as colored impurities generated by overheating in vessels or pipes. The purpose of refining is to remove these colored and unstable and odorous impurities. At present, the methods of paraffin refining mainly include adsorption refining and hydrorefining.

Adsorption refining is to use a highly active adsorbent to remove some impurities in paraffin. The purification of clay is to use activated clay as an adsorbent, and the dosage is generally 2% to 8%. First, the molten paraffin under the white clay is fully mixed and heated to a certain temperature, and kept for a period of time, so that the impurities in the wax are fully adsorbed on the surface of the white clay, and then the white clay and other mechanical impurities in the wax are filtered out, so that the color and luster can reach the quality index of white wax.

Hydrorefining is to convert and remove non-hydrocarbon components and unsaturated hydrocarbon components of sulfur, oxygen and nitrogen contained in wax through hydrogenation reaction under the action of catalyst, under certain temperature and hydrogenation conditions, so as to improve the quality of wax. quality of paraffin. Some paraffins contain condensed aromatic hydrocarbons that are harmful to the human body, which can be greatly reduced after hydrorefining, so that there is almost no such hydrocarbons.


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