High-dispersity cobalt-based Fischer-Tropsch synthesis catalyst as well as preparation method and application thereof

Abstract

The invention discloses a high-dispersity cobalt-based Fischer-Tropsch synthesis catalyst as well as a preparation method and an application thereof. The catalyst comprises an oxide carrier, wherein an active component cobalt and a noble metal addition agent are loaded on the surface of the oxide carrier; the active component cobalt accounts for 3%-40% of the total weight of the catalyst, the noble metal addition agent accounts for 0.01%-1% of the total weight of the catalyst and the oxide carrier accounts for 59%-96.99% of the total weight of the catalyst; and the specific surface area of the catalyst is 20m<2> / g-300m<2> / g. According to the high-dispersity cobalt-based Fischer-Tropsch synthesis catalyst, a high-pH-value complexing metal salt carrier is selected to provide a metal element loading environment; hydrazine hydrate and a heavy metal salt are respectively used as a reducing agent and an induction agent of a reduction reaction; the active component cobalt is obtained by reduction at low temperature, and a water-phase reaction environment and ultrasonic vibration are additionally adopted so that the dispersity and the reduction degree of active grains are improved; the reduction of the mechanical intensity of the carrier and the loss of the active component are effectively avoided; the service life is prolonged; and the catalyst can be directly used for a Fischer-Tropsch synthesis reaction without high-temperature roasting and activation reduction.

Description

technical field [0001] The invention relates to the field of industrial catalytic Fischer-Tropsch synthesis, in particular to a high-dispersion cobalt-based Fischer-Tropsch synthesis catalyst and its preparation method and application. Background technique [0002] In recent years, my country's dependence on imported crude oil has shown an increasing trend year by year, and the import ratio has reached more than 55%. Using syngas mainly composed of carbon monoxide and hydrogen as raw materials, using cobalt catalysts to obtain clean hydrocarbon fuels through Fischer-Tropsch synthesis technology is one of the important ways to solve my country's oil shortage and reduce foreign dependence. This fuel acquisition method has the advantages of diversified raw materials and clean and environmentally friendly fuel oil products, which is conducive to adapting to the adjustment of my country's energy consumption structure and the increasing environmental protection requirements. The ...

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Problems solved by technology

However, this preparation method has the following three shortcomings in the actual application process: 1) In order to increase the metal loading capacity, a high-concentration cobalt salt solution needs to be used, so the pH value of the impregnating solution is often lower than 2, while the commonly used oxide carrier The isoelectric point is generally between 2 and 7, which is higher than the pH value of the impregnating solution, which may easily cause partial dissolution of the carrier during the impregnation process, resulting in a decrease in mechanical strength and the inability of the active components to be firmly combined on the surface of the carrier, resulting in catalyst failure. The surface metal particles are lost during the reaction and deactivated; 2) The calcination and reduction activation temperature of the catalyst is often higher than 300 ° C, while the Huttig temperature (the temperature at which defective atoms can move) of cobalt metal is only 253 ° C. It can accelerate the sintering process between the cobalt particles on the surface of the catalyst, thereby reducing the dispersion of the active metal particles; 3) The particle size distribution range of the metal particles on the catalyst surface prepared by the impregnation method is very wide (usually between 4 and 400nm), during the reaction process The sintering or agglomeration of the active metal particles on the surface of the catalyst will reduce the dispersion of the active metal and the number of active sites, resulting in a reduction in catalyst activity and a shortened life.

[0005] Researchers have made a series of improvements to the deficiencies of the impregnation method, hoping to improve the performance of the catalyst by increasing the dispersion of active metals. For example, the Chinese patent application number 200580015004.6 discloses a preparation method of a cobalt catalyst, which combines cobalt ammonia The aqueous solution of the compound is mixed with the solid catalyst carrier, then heated to 80-110°C and maintained for a long enough time, part of the cobalt ammonium complex decomposes and the insoluble cobalt compound is precipitated on the surface of the carrier, and then heated at 200-600°C under a hydrogen atmosphere Cobalt catalysts suitable for Fischer-Tropsch synthesis were obtained through reduction activation. Although this method overcomes the problem of too low pH value of the impregnation solution and improves metal dispersion, the preparation method takes too long, and the active components obtained by thermal decomposition The combination with the carrier is not strong, and the catalyst still needs to be reduced at high temperature before use; in addition, the Chinese patent application number 200910035350.0 discloses a preparation method of a supported catalyst for hydrogenation, which uses pretreated Silicon oxide is used as the carrier, the transition metal is impregnated on the surface of the carrier and heat-treated, and then the heat-treated catalyst precursor is reduced by using hydrazine hydrate in the alcohol-water system, and the obtained transition metal catalyst is suitable for catalytic hydrogenation of p-nitrophenol

However, the process of this method is relatively complicated, and the particle size of the metal particles on the surface of the obtained catalyst is about several thousand nanometers, and the particle dispersion degree is low.

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