A catalyst for preparing unsaturated aldehydes by oxidation of low-carbon olefins and its preparation method

Abstract

The invention provides a catalyst used for preparing unsaturated aldehyde through low-carbon olefin oxidation, and a preparation method thereof. According to the method, raw materials are subjected to multi-time hot material coating, such that a three-layer multi-metal oxide catalyst with a gradient distribution of catalytic activities is prepared. The catalyst is used for catalyzing propylene oxidation for preparing acrolein, or catalyzing isobutylene oxidation for preparing isobutyraldehyde. The catalyst comprises active components of various metal oxides, wherein the compositions of the active components can be represented as the following general formulas: MoaBibNicFedCoeSifAgBhOx (I); MoaBibNicTijOm (II); and MoaBibSifAlkOn (III). The catalyst is suitable for propylene or isobutylene selective oxidation, such that corresponding unsaturated aldehydes are produced. With the catalyst, high hot spot caused by preliminary contact of propylene and the catalyst can be effectively inhibited, and catalytic selectivity can be improved.

Description

technical field [0001] The invention relates to a multi-metal composite oxide catalyst and a preparation method thereof, which are used to catalyze the selective oxidation of light olefins to produce corresponding unsaturated aldehydes, especially for the production of acrolein by the oxidation of propylene or the production of isobutyraldehyde by the oxidation of isobutene. Background technique [0002] The selective oxidation of low-carbon olefins to produce corresponding unsaturated aldehydes is a strong exothermic reaction. At present, the selective oxidation of olefins and molybdenum-bismuth catalysts is mainly used to produce aldehydes in industry. The excessive heat generated in the catalyst reaction zone should not form a heat accumulation zone, otherwise it will lead to the sublimation and loss of the active components of the catalyst, which will reduce the activity of the catalyst and lead to the formation of by-products due to excessive oxidation reactions, and eve...

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Problems solved by technology

Such as: CN1210511A, prepare a variety of loaded catalysts with different activity types or place them in the reaction tubes sequentially after dilution in different proportions to minimize the temperature of the hot zone. Although this method can dilute the heat of reaction to a certain extent, it is not effective for the Filling etc. bring many inconveniences, what is more serious is that the method of diluting has actually permanently reduced the catalyst activity of this part bed layer; In an active catalyst, the catalytic activity decreases temporarily, and the temperature of the overheated part can be reduced. This method seems to be very good in theory. The catalyst activity is temporarily reduced by the toxic component, but the slow release process of the toxic component is difficult to control, and even It may be released excessively, resulting in a significant decrease in catalyst activity or even deactivation. In addition, this slow-release toxic component is also a problem that must be considered for environmental protection.

CN1472008A provides a catalyst with different activities loaded on a carrier with a multidimensional structure, which is used for the oxidation of paraffins to unsaturated carboxylic acids and the ammoxidation of paraffins to unsaturated nitriles, but how to control the catalyst components on the multidimensional structure according to the predetermined mode The load will be a relatively big problem, especially in the process of industrial production, it is a bottleneck that is difficult to solve

[0006] However, due to the complex preparation process of the catalyst for the selective oxidation of olefins, the use of more elements, and the preparation of the co-precipitation method, it is very important to ensure the repeatability of the catalyst preparation

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