The present invention relates to a pre-hydrotreatment and purification method for waste lubricating oil, the method comprising the following steps: mechanical impurities are removed from waste lubricating oil, and then the oil is subjected to flash distillation to separate free water and a portion of light hydrocarbons; a bottom product of the flash distillation column is mixed with hydrogen and a self-sulfurizing oil-soluble transition metal catalyst, and then enters a slurry bed reactor for pre-hydrotreatment; a gas product obtained by performing separation on a reaction effluent is subjected to adsorption purification and then enters a hydrogen recycle compressor for cyclic use; a liquid product obtained by performing separation on a reaction effluent is subjected to hydrocyclone separation and solvent washing to remove solid residue, and finally a purified lubricating oil component is obtained. The method of the present invention has such advantages as simple processing procedures, a high non-ideal component conversion rate, a high oil liquid yield, and good quality. In addition, the oil-soluble catalyst features simple dispersion, no need for vulcanization, a small catalyst adding amount, high low-temperature hydrogenation activity, and is capable of effectively preventing the coking that could occur during a process of preheating the waste lubricating oil, markedly extending the operational lifespan of a waste lubricating oil hydrogen treatment device.

A method for hydrotreating and recycling waste lubricating oil, the method comprising the two steps of slurry bed pre-hydrotreatment and deep hydrotreatment, specifically as follows: mechanical impurities are removed from waste lubricating oil, and then the oil is subjected to flash distillation to separate free water and a portion of light hydrocarbons; a bottom product of the flash distillation column is mixed with hydrogen and a self-sulfurizing oil-soluble transition metal catalyst, and then enters a slurry bed reactor for pre-hydrotreatment; a liquid product obtained by performing separation on a reaction effluent is subjected to hydrocyclone separation and solvent washing to remove solid residue, and then a pre-treated lubricating oil component is obtained; said component is mixed with hydrogen and then enters a hydrofining reactor, an isomerization-dewaxing reactor, and a supplementary refining reactor, connected in series, for hydrotreatment; and the reaction products are separated to obtain high-quality naphtha, diesel oil and a lubricating base oil. The method of the present invention has such advantages as simple processing procedures, a high oil liquid yield, good lubricating oil base oil quality, and can implement full-fraction resource utilization of waste lubricating oil. In addition, the oil-soluble catalyst features simple dispersion, no need for vulcanization, a small catalyst adding amount, high low-temperature hydrogenation activity, is capable of effectively preventing the coking that could occur during a process of preheating the waste lubricating oil, and ensures long-term stable operation of the device.