Method for continuously synthesizing citral through tubular reactor

Abstract

The invention discloses a method for continuously synthesizing citral through a tubular reactor, the method comprises the following steps: pre-complexing dehydrolinalool and a copper catalyst to form a homogeneous system, adding a titanium catalyst and an acid catalyst into the homogeneous system to form a homogeneous solution, finally, continuously pumping the homogeneous solution into a tubular reactor from a feeding port through a plunger pump at a certain flow speed and staying for reaction in the tubular reactor, enabling a crude product obtained after staying for reaction to continuously flow out from the other port so that a citral crude product can be continuously obtained; and carrying out reduced pressure rectification on the crude citral product to obtain the citral product. According to the invention, citral is continuously synthesized by adopting the tubular reactor, so that continuous production of citral is realized, time cost and labor cost of production are saved, and industrial production is facilitated; the occurrence of safety accidents caused by heat release due to violent reaction in large-scale production is avoided, and the safety is high.

Description

technical field [0001] The invention belongs to the technical field of organic synthesis and relates to the synthesis of spices, in particular to a method for continuously synthesizing citral through a tubular reactor. Background technique [0002] Citral is one of the most important representatives of open-chain monoterpenes. It is a colorless or slightly yellow liquid with a strong lemon fragrance. Citral can be used in the manufacture of citrus-flavored food flavors, and is also used in the synthesis of isopulegol, hydroxycitronellal, and ionone, which is a raw material for the synthesis of vitamin A. [0003] The synthetic method of citral mainly contains at present: [0004] (1) CN112642489A reported a method using linalool as raw material to prepare citral under the condition of bimetallic catalytic oxidation, but this method used precious metals such as ruthenium, rhodium, iridium, gold, platinum, palladium, etc., which was expensive; [0005] (2) CN104292087 report...

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Problems solved by technology

[0004] (1) CN112642489A reported a method using linalool as raw material to prepare citral under the condition of bimetallic catalytic oxidation, but this method used precious metals such as ruthenium, rhodium, iridium, gold, platinum, palladium, etc., which was expensive;

[0005] (2) CN104292087 reported a kind of dehydrolinalool as raw material, in the presence of solvent ethylbenzene and cocatalyst carboxylic acid, adding catalyst 1,2-bis(diphenylphosphine)ethane-bis(2-methanol) Propyl) ruthenium carries out catalytic rearrangement reaction, makes citral, and this method needs to use ethylbenzene as solvent, and ethylbenzene is highly volatile, endangers environment, and this method has used precious metal ruthenium equally, and economic efficiency is poor;

However, triphenylsilyl vanadyl oxide is easy to hydrolyze, has poor stability, and requires anhydrous conditions, and the reaction conditions are harsh. At the same time, this method uses a large amount of expensive trialkylsilanols, which is not suitable for industrial production;

[0007] (4) CN104292087A reported a catalyst composed of dehydrolinalool as raw material, molybdenum dioxide diacetylacetonate and weakly acidic cation exchange resin, petroleum ether as solvent, dimethyl sulfoxide as Co-solvent, react at 120 degrees for 9 h to prepare citral, the molybdenum system catalyst activity of this method is not high, the reaction time is long, and the efficiency is low