Composite catalyst, preparation method thereof and application thereof in citral synthesis

Abstract

The invention discloses a composite catalyst, a preparation method thereof and an application of the composite catalyst in citral synthesis, the catalyst comprises a loading component and a carrier, and the loading component comprises an active component and other components; the active component is metal salt; the other components comprise a connecting arm R, a ligand L and a component B; in thepresence of the composite catalyst, isopentenal and isopentenol are subjected to alcohol-aldehyde condensation, thermal cracking and rearrangement reaction to synthesize citral with high activity andhigh selectivity, and the catalyst does not need to be replaced in the reaction process. The catalyst provided by the invention improves the selectivity of the product, can obtain higher yield, avoidsthe problem of equipment corrosion, prolongs the service life of the equipment, has obvious environmental protection benefits, is environment-friendly, and is beneficial to industrial mass production.

Description

technical field [0001] The invention belongs to the field of organic synthesis, in particular to a method for synthesizing citral with a new catalyst, in particular to a method for synthesizing citral with prenyl alcohol and prenyl aldehyde as raw materials. Background technique [0002] Citral (also known as 3,7-dimethyl-2,6-octadiene-1-al), present in plant essential oils such as lemongrass oil and eucalyptus oil, has a strong lemon aroma. It is widely used in spices, medicine, daily chemical and food industries, and its acquisition is mainly through chemical synthesis. At present, the mainstream synthesis route in the industry is the C5+C5=C10 route, that is, two C5 raw materials, a total of three steps: the first step: prenol and prenyl aldehyde undergo aldol condensation to generate 3-methyl-2 -butene-1-aldehyde di-prenyl acetal; second step: 3-methyl-2-butene-1-aldehyde di-prenyl acetal pyrolysis to generate prenyl-3- Methyl-2-butenyl ether (citral precursor); the th...

AI Technical Summary

Problems solved by technology

Its disadvantages are: the catalyst is an acid with a low boiling point, the amount of use is not easy to control, it is difficult to recycle and apply mechanically, the requirements for production equipment are high, and there is a hidden danger of environmental pollution

When the reaction substrate is prenol and prenal, the conversion rate of prenal is greater than 97%, and its disadvantage is that the amount of nitric acid is difficult to control

[0007] U.S. Patent No. 5,177,265A discloses prenyl aldehyde and prenol as raw materials, phosphoric acid as a catalyst for condensation reaction, adding toluene as a solvent, wherein toluene can form an azeotrope with water, the reaction temperature is 60-90 ° C, the pressure It is 8000-14000Pa (absolute pressure), the transformation rate of prenaldehyde is 83%, and the yield of acetal is 75.6%, and its shortcoming is: after the reaction finishes, unnecessary acid needs to pass through potassium acetate, sodium acetate, carbonic acid Neutralization with salt or hydroxide, etc., increases the "three wastes", the post-treatment process is complicated, and it is difficult to realize industrialized large-scale production

The disadvantages of this patent are: 1. 3-methyl-2-butene-1-aldehyde di-isopentenyl acetal is used in a large amount; 2. The amount of phosphoric acid is small, the control is difficult, and it is difficult to carry out continuous production

Its disadvantages are: the lithium chloride used is highly corrosive and the reaction is carried out under negative pressure conditions, which is not convenient for continuous production and energy saving

The disadvantages are: under high temperature conditions, protonic acids such as phosphoric acid are used as catalysts, which is not conducive to recycling, easy to produce high boiling point substances, and has high requirements for equipment materials, which increases production costs and is not environmentally friendly.

Its disadvantages are: using isopentonic acid as a catalyst, prone to side reactions, difficult to recycle and apply mechanically, and unfavorable for industrial production

Its disadvantages are: the three-step reaction is completed in the same reactor, resulting in low conversion rate of raw materials, complex products, difficult separation, and difficult actual yield to reach expectations

Its disadvantages are: during the rearrangement reaction, the system contains alcohols and the reaction temperature is high, there will be obvious side reactions, and the product selectivity is low

[0018] In summary, use inorganic acid or organic acid as catalyst to catalyze the reaction of prenyl aldehyde and prenol to prepare citral, the catalyst is not easy to recycle and apply mechanically, and side reactions are prone to occur, which affects the product yield; The equipment is corrosive and requires high equipment materials, which will increase equipment investment; thermal cracking and rearrangement reactions at high temperatures will generate high boiling point substances, which need to be cleaned regularly, affecting product yield and continuous production

In addition, inorganic acid or organic acid is used as a catalyst, because the dosage is not easy to control, and the reaction solution needs to be neutralized at the end of the reaction, which will generate a large amount of waste water, which does not conform to the development concept of economic and environmental protection in modern industrial production.

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