How is the "semi-refined paraffin supply" paraffin derived from oil?

　　The process of obtaining paraffin wax from petroleum is generally the lubricating oil fraction obtained by distilling the oil, the paraffin wax obtained by dewaxing and degreasing process, and then the paraffin wax obtained by refining and molding can be packaged into paraffin products.

　　Paraffin wax is derived from oil in this way:

　　The first step is distillation. At the refinery, crude oil is first 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 fractions, kerosene fractions, diesel distillates, lubricating oil fractions (also known as wax-containing oil fractions) and so on. Lubricating oil and paraffin wax can be obtained after the lubricating oil fraction is separated by processing. Since paraffin wax and lubricating oil are products of the same fraction, the hydrocarbon composition contained in paraffin wax depends on certain properties of the lubricating oil fraction. The boiling point range of paraffin wax is substantially consistent with the boiling point range of lubricating oil containing this paraffin wax. Since it is practically impossible to completely dewater the oil during the wax degreasing process, the types of trace cyclic hydrocarbons and non-hydrocarbon impurities contained in paraffin wax depend on the lube oil fraction.

　　The second step is the separation of the oil and wax. Lubricating oil fractions with more wax have a higher freezing point. In order to obtain oils with a low freezing point, the wax must be removed. Similarly, only n-alkanes in lubricating oils are the ideal component of commercial paraffin waxes. Although it is not possible to obtain solid paraffins of pure positive alkanes, it is necessary to remove various hydrocarbons such as naphthalkrakanes, isoparaffins, aromatics and other hydrocarbons present in liquid oils in the fraction. At the same time, in order to obtain paraffin with a certain melting point, it is also necessary to separate the hydrocarbons with a lower melting point from it. Because in processing, the separation of oil wax is carried out according to the different freezing points of the oil and wax or the solubility of the solvent. In China, the lubricating oil fraction is usually de-waxed first, and then the resulting wax paste is further degreased to obtain paraffin with a certain melting point and hardness. However, it is best to first refine the lubricating oil distillate through the solvent and then dewaxe, although the processing capacity of the solvent refining device needs to be increased, however, the amount of treatment of the dewaxing device can be reduced, and the more important thing is that further degreasing and refining of the wax paste is more advantageous, especially when producing waxes for the food industry and medicine.

　　Dewaxing containing wax fractions can be used by pressing and solvent methods. Usually the solvent dewaxing process used in the solvent has a mixture of methyl ethyl ketone and toluene, these solvents have a large solubility of the oil at a certain freezing temperature, while the solubility of the wax is small, and due to the addition of the solvent, the oil is diluted, the viscosity is reduced, so when the oil is frozen to a certain temperature, the wax crystallizes out. It is then filtered to separate the crystalline wax from the oil. Lubricating oil distillate dewaxing oil obtained is further refined into lubricating oil, the separated wax is called wax paste, it is a paste-like wax and oil mixture, generally oil content of 10% to 20%, but also need to be further degreased in order to produce commercial paraffin wax.

　　The degreasing of wax paste is often used in the production of solvent degreasing and sweating degreasing methods. The process of solvent degreasing is immediately after the solvent dewaxing process, the filter cake obtained by the solvent dewaxing is then added with solvent, and the temperature filter is heated according to the specifications of the required paraffin products to obtain a coarse wax with lower oil content, also known as degreasing wax.

　　The third step is the refining of paraffin wax. After the wax paste has gone through dewaxing, degreasing and other processes, the melting point and oil content have reached the quality index of commercial paraffin wax. However, at this time, the wax generally contains the remaining substances in the processing process, mainly a little gum and asphaltene. In addition, trace amounts of restless olefins 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, paraffin refining methods are adopted, mainly including adsorption refining, hydrogenation refining and so on.

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

　　Hydrorefining is under the action of the catalyst, under certain temperature and hydrogenation conditions, through the hydrogenation reaction, so that the non-hydrocarbon components containing sulfur, oxygen, nitrogen and unsaturated hydrocarbon components contained in the wax are converted and removed, thereby improving the quality of paraffin wax. Some paraffins contain thick cyclic aromatic hydrocarbons that are harmful to the human body, which can be greatly reduced after hydrorefining to the point that they are almost free of this hydrocarbon.