Abstract: A document classification method includes: obtaining a document; extracting document keywords and a document abstract from the document; determining, according to the document keywords and the document abstract, a first classification label of the document; receiving a second classification label of the document, the second classification label being determined according to the document keywords, the document abstract, and the first classification label; obtaining a classification efficiency value of the documents, the classification efficiency value indicating a confidence level of the second classification label; and determining the second classification label as a final classification label of the document if the classification efficiency value is greater than or equal to a first threshold. The document classification method described above may improve the speed of document classification by computer, thereby improving the efficiency of document classification.

Abstract: A metal detergent and a preparation method thereof and a lubricant oil containing the metal detergent. The metal detergent is sulfurized calcium alkyl phenolate, the method for preparing the metal detergent includes the following steps: a) mixing alkyl phenol, a calcium source and base oil to obtain a mixed solution; b) mixing the mixed solution, ethylene glycol and a sulfur source to carry out sulfurization reaction to obtain a sulfurization reaction solution; c) implementing carbonation reaction between the sulfurization reaction solution and CO2 to obtain a carbonation reaction solution; and d) extracting the carbonation reaction solution with a solvent, upon refining, to obtain sulfurized calcium alkyl phenolate; wherein the solvent includes solvent oil, water and oxygenous derivative of hydrocarbon. Experimental results show that the content of free alkyl phenol is below 1.5 wt % in the sulfurized calcium alkyl phenolate prepared using the preparation method provided by the present application.

Abstract: A metal detergent and a preparation method thereof and a lubricant oil containing the metal detergent. The metal detergent is sulfurized calcium alkyl phenolate, the method for preparing the metal detergent includes the following steps: a) mixing alkyl phenol, a calcium source and base oil to obtain a mixed solution; b) mixing the mixed solution, ethylene glycol and a sulfur source to carry out sulfurization reaction to obtain a sulfurization reaction solution; c) implementing carbonation reaction between the sulfurization reaction solution and CO2 to obtain a carbonation reaction solution; and d) extracting the carbonation reaction solution with a solvent, upon refining, to obtain sulfurized calcium alkyl phenolate; wherein the solvent includes solvent oil, water and oxygenous derivative of hydrocarbon. Experimental results show that the content of free alkyl phenol is below 1.5 wt % in the sulfurized calcium alkyl phenolate prepared using the preparation method provided by the present application.