The process of obtaining paraffin from petroleum generally involves dewaxing and deoiling the lubricating oil fraction obtained by distilling petroleum, and then refining and molding it. It can be packaged into paraffin products.
Paraffin wax is obtained 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 tower, the various components of petroleum are divided into various fractions according to their boiling point ranges, such as gasoline fraction, kerosene fraction, diesel fraction, lubricating oil fraction (also called waxy oil fraction), etc. Lubricating oil and paraffin can be obtained after processing and separation of the lubricating oil fraction. Since paraffin wax and lubricating oil are products of the same fraction, the composition of the hydrocarbons contained in paraffin wax depends on certain properties of the lubricating oil fraction. The boiling point range of paraffin wax is basically the same as the boiling point range of the lubricating oil containing this paraffin wax. Since the actual wax deoiling process cannot completely remove the oil, the type of trace cyclic hydrocarbons and non-hydrocarbon impurities contained in the paraffin wax depends on the lubricating oil fraction.
The second step is oil and wax separation. Lubricating oil fractions containing more wax have higher freezing points. In order to obtain an oil with a low pouring point, the wax must be removed. Similarly, in lubricating oils, only n-alkanes are the ideal components of commercial paraffin. Although it is impossible to obtain pure normal paraffin paraffin, it is necessary to remove various hydrocarbons such as naphthenes, isoparaffins, aromatic hydrocarbons, etc. that exist as liquid oil in the distillate. At the same time, in order to obtain paraffin with a certain melting point, hydrocarbons with lower melting points must be separated from it. During processing, the separation of oil and wax is carried out based on the different freezing points of oil and wax or the different solubility in solvents. In our country, the lubricating oil fraction is usually dewaxed first, and then the resulting wax paste is further deoiled to obtain paraffin wax with a certain melting point and hardness. However, it is best to first refine the lubricating oil fraction through solvent and then dewax it. Although the processing capacity of the solvent refining device needs to be increased, the processing capacity of the dewaxing device can be reduced. More importantly, the wax paste can be further processed. Deoiling and refining are more advantageous, especially when producing waxes for the food industry and medicine.
Two methods, pressing and solvent, can be used to dewax waxy fractions. Usually the solvent used in the solvent dewaxing process is a mixture of methyl ethyl ketone and toluene. These solvents have high solubility for oil but low solubility for wax at a certain freezing temperature. Due to the addition of the solvent, the oil product is Dilution reduces the viscosity, so when the oil freezes to a certain temperature, the wax crystallizes out. The crystallized wax and oil can be separated by filtration. The oil obtained by dewaxing the lubricating oil fraction is further refined into lubricating oil. The separated wax is called wax paste, which is a paste-like mixture of wax and oil. Generally, the oil content is about 10% to 20%. Further deoiling is required to produce commercial paraffin.
For the degreasing of wax paste, two methods commonly used in production include solvent degreasing and sweating degreasing. The solvent deoiling process follows the solvent dewaxing process. The filter cake obtained by solvent dewaxing is added with solvent, and the temperature is increased and filtered according to the specifications of the required paraffin product to obtain crude wax with lower oil content, which is also called dewaxing. Oil wax.
The third step is the refining of paraffin wax. After the wax paste has undergone dewaxing, deoiling and other processes, its melting point and oil content have reached the quality indicators of commercial paraffin wax. But at this time, the wax generally also contains substances leftover during the processing, mainly a small amount of colloid and asphaltene. In addition, trace amounts of unstable olefin and aromatic polymers remain, as well as colored impurities generated by overheating in containers or pipes. The purpose of refining is to remove these colored, unstable and odorous impurities. Currently, the methods used for paraffin refining include adsorption refining, hydrogenation refining, etc.
Adsorption refining uses a highly active adsorbent to remove some impurities in paraffin. Clay refining uses 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 to allow the impurities in the wax to be fully adsorbed on the surface of the white clay. Then, the white clay and other mechanical impurities in the wax are filtered out, so that the color reaches the quality index of white wax.
Hydrorefining is to use a catalyst to remove the sulfur and oxygen contained in wax through a hydrogenation reaction at a certain temperature and hydrogenation conditions. , nitrogen non-hydrocarbon components and unsaturated hydrocarbon components are converted and removed, thereby improving the quality of paraffin wax. Some paraffins contain condensed ring aromatic hydrocarbons that are harmful to the human body. After hydrorefining, they can be greatly reduced to almost no such hydrocarbons.
微信扫一扫打赏
