A sodium catalyst refers to an elemental sodium or sodium compound which has a catalytic function. Sodium is a silver-white metal with a soft texture, good ductility and magnetic permeability. Sodium is very chemically active, and can react with oxygen at room temperature and under heating. Sodium also reacts violently with water. Metallic sodium and some sodium compounds have very good catalytic activity and can therefore be used as catalysts.
Although the types of sodium catalyst are not abundant, it has applications in the fields of organic synthesis and environmental protection because the sodium catalyst exhibits good catalytic activity in some reactions and is simple to prepare.
- Esterification reaction: Sodium bisulfate is a strong ionic compound that is inexpensive and readily available. Since sodium hydrogen sulfate is easily soluble in water but insoluble in the reaction system of organic acids and alcohols, it can be used as a catalyst for the esterification of carboxylic acids and alcohols. The advantages of sodium hydrogen sulfate as a catalyst are that the reaction liquid can be directly separated from the catalyst, the reaction process is simple, the operation is convenient, the equipment is not easy to be corroded, the environmental pollution is small, and the catalytic activity is good, so it is widely used in esterification reactions. Sodium bisulfate can catalyze the synthesis of various types of esters. For example, fenofibrate (isopropyl 2-methyl-2-[4-(4-chlorobenzoyl)phenoxy]propionate) is a second-generation phenylacetic acid drug with important clinical effects. Sodium hydrogen sulfate can catalyze the esterification of fenofibrate acid and isopropyl alcohol to synthesize fenofibrate.
- Beckmann rearrangement reaction: Amides are an important class of organic compounds. The Beckmann rearrangement reaction is an effective method for the preparation of amides in organic synthesis and plays an extremely important role in the chemical industry. The sulfonic acid functional group often has a special catalytic activity and thus can be used as a catalyst. Among them, sodium octane sulfonate (SOS) exhibits very excellent catalytic activity for the Beckmann rearrangement reaction and is therefore often used as a catalyst in the Beckmann rearrangement reaction. For example, sodium octane sulfonate (SOS) can be used as a catalyst to catalyze the Beckmann rearrangement of ketone oxime to synthesize the corresponding amide compound. Using sodium octane sulfonate as catalyst, the Beckmann rearrangement reaction has the advantages of mild reaction conditions, high synthesis efficiency, high yield and simple post-treatment, which provides an effective method for the synthesis of amide compounds.
Figure 1. Sodium catalyst catalyzed Beckmann rearrangement reaction
- Condensation reaction: The use of sodium catalysts in condensation reactions is also extensive. The Knoevenagel condensation reaction between a carbonyl compound and an active methylene compound is an important method for synthesizing carbon-carbon double bonds. In the absence of solvents, the Knoevenagel condensation reaction between aromatic aldehyde and 1-butyronitrile can be catalyzed by using Na2TeO3, which is inexpensive and readily available, as catalyst. Using Na2TeO3 as a catalyst, the Knoevenagel condensation reaction has the advantages of mild conditions, short reaction time, excellent yield, simple and convenient post-treatment.
Figure 2. Sodium catalyst catalyzed condensation reaction
- Environmental protection: Excessive ammonia nitrogen in sewage will cause eutrophication of the water body and deterioration of water quality, which seriously harms the environment and human health. As a strong oxidizing agent, sodium hypochlorite has the advantages of low cost and good sterilization effect, so it is often used in the catalytic oxidation of ammonia-containing wastewater. In addition, nitrogen oxides in the air are toxic to humans and vegetation. Nitrogen oxides can also interact with hydrocarbons to form photochemical smog, reduce air quality, and even damage the ozone layer. Selective catalytic reduction (SCR) technology is one of the effective methods for removing nitrogen oxides from the air. Na has a high catalytic activity for the gasification reaction of CO2, H2O and O2 with semi-coke. Using sodium semi-coke-supported sodium as a catalyst, nitrogen oxides in the air can be effectively removed by selective catalytic reduction (SCR) technology.
- Wang, Fey-Long. (2001). “Catalytic synthesis of propionitrile from methanol and acetonitrile over activated carbon-supported sodium catalysts.” Catalysis Letters 73(2-4), 215-219.
- Grzybek, Teresa. (1993), “Surface composition and selectivity of sodium-compound-im pregnated calcium oxide catalysts for the oxidative coupling of methane.” Applied Catalysis, A: General 107(1), 115-24.
- Wan, Qing-me. (2015), “Synthesis of tristyrylphenol polyoxyethylene ether oleate by sodium bisulfate.” Yingyong Huagong 44(6), 1026-1028.
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