Method for preparing n-octadecane from stearic acid

Abstract

The invention relates to a method for preparing n-octadecane from stearic acid. According to the invention, the raw material stearic acid and a solvent are mixed and then undergo a hydrogenation reaction in the presence of a catalyst and hydrogen, wherein the catalyst is a palladium / carbon nanotube catalyst, reaction pressure of the hydrogenation reaction is 1 to 10 MPa, reaction temperature is 220 to 320 DEG C, reaction time is 3 to 10 h, the catalyst uses a multi-walled carbon nanotube as a carrier and 2 to 10% by mass of palladium as an active component, and the solvent is one selected from the group consisting of hexane, n-heptane, n-octane and dodecane. Compared with the prior art, the method provided by the invention has the advantages of simple preparation technology, a low reaction temperature, a small usage amount of the solvent, high reaction activity and high yield of a target product.

Description

technical field [0001] The invention relates to a method for generating n-octadecane through liquid-phase catalytic hydrodeoxygenation of stearic acid, belonging to the technical field of catalysis. Background technique [0002] As one of the key components of low-temperature diesel oil improvers and environmentally friendly liquid fuel compositions, n-paraffins have been widely used. important role. N-octadecane, as a n-alkane with a high carbon number, is also used in the fields of pharmaceutical intermediates and phase change materials in addition to the above-mentioned uses. [0003] The existing preparation methods of n-alkanes mainly include the following: 1. The mixture of n-alkanes is prepared by dewaxing molecular sieve or urea, and then sub-stage freezing is carried out to separate n-alkanes monomers. The typical process There is the molex process of Vop Company, and the IVDW process developed by my country itself; 2. The Wurtz reaction is used to prepare symmetri...

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Problems solved by technology

[0004] Although the above methods can obtain the corresponding n-alkane monomers, there are certain problems in each method: as the first method, the process conditions are more complicated, and the requirements for some equipment and materials are very high; the second method is only applicable For symmetrical even-numbered alkanes, the resulting products need to be extracted repeatedly with ether solvent, and the raw materials with a positive octadecyl carbon chain are not easy to obtain; the third and fourth methods are dangerous to operate, and petroleum ether is very easy to erupt in the violent reaction between metal sodium and halogenated alkanes. Low safety factor and high cost

[0005] The corresponding alkanes can be prepared by hydrogenation of higher fatty acid esters, but during the hydrogenation reaction, a large number of decarboxylation and decarbonylation reactions will occur, making the composition of the reaction product complex and producing more alkanes with reduced carbon numbers. On the one hand, it is not conducive to improving the yield of the target product. On the other hand, the decarboxylation reaction and decarbonylation reaction will produce carbon monoxide or carbon dioxide, which will have an adverse effect on the hydrogenation reaction.

[0006] CN200910100260.5 discloses a method for preparing alkanes from higher fatty acid esters, using fatty acid methyl esters containing 8 to 22 carbon atoms or fatty acid ethyl esters containing 8 to 22 carbon atoms as raw materials for hydrogenation reaction to produce alkanes, However, it can be seen that in the obtained alkane products, most of the carbon in the fatty acid is still removed, such as using methyl stearate (stearic acid is octadecyl carboxylic acid) as raw material, the obtained heptadecane The total yield of octadecanes and octadecanes is only 75%, therefore, the yield of non-decarburized direct hydrogenation products (octadecanes) will be lower

At the same time, the difference between the boiling points of heptadecanes and octadecanes is very small, and it is very difficult to further obtain octadecanes through separation technology