Stannous octoate is the most widely used catalyst in the polyurethane industry. It has many kinds of preparation methods. At present, the preparation of stannous octoate mostly adopts the aldehyde disproportionation method, acid anhydride method, and double decomposition method.
Compared with the traditional method for preparing stannous octoate by electrochemical method, the electrochemical method has the characteristics of stable production process control, simple operation, low cost of large-scale production, and good product quality.
Here, Jinbangch will introduce the electrochemical method to prepare stannous octoate in detail. And an additional method for preparing stannous octoate is introduced.
1. Preparation of stannous octoate by electrochemical method
The optimum process condition for the preparation of stannous octoate by the electrochemical method is: to use sodium chloride with a concentration of 6 mol/L as the electrolyte. The metal tin is used as the anode, and the titanium plate is used as the cathode. The anode current density is 100-120 A/m2, the cathode current density is 800-1 000 A/m2, the stirring speed is 100 r/min, the electrolyte temperature is 60-70 ℃, and two synergistic antioxidants are added simultaneously.
Compared with the traditional double decomposition method, the process is short, the operation control is simple, and the product quality and stability have been greatly improved. The process uses refined tin as raw material to replace stannous chloride, which has a higher price and does not need to consume a large amount of alkali, which can greatly reduce production costs. Due to the completely closed loop, the production process of this process has no discharge of three wastes, and the working environment is better. The products produced have been proved by users to be of excellent quality.
Detailed steps
The metal tin is used as the anode, stainless steel, titanium, or graphite is used as the cathode, and a strong electrolyte such as alkali metal salt is used as the electrolyte. Isooctanoic acid and antioxidants are placed in the electrolyzer. It is one of the characteristics of this process to synthesize stannous octoate at one time in the electrolytic cell by using the cathode and anode products and octanoic acid. When a current passes through, the anode is dissolved, thereby reacting with the hydroxide, and is octanoic acid produced by the cathode to form stannous octoate. After the product is taken out, it is purified (if necessary, it can be extracted with a solvent) to obtain the stannous octoate product.
The following reactions take place during electrolysis:
Anode reaction:
Sn→Sn2+
Cathode reaction:
Main reaction:
2H2O→2OH–+H2
Side reaction:
Sn2+→Sn
Reaction between the poles:
Sn2++2C7H15COO–→Sn(C7H15COO)2 ↓
Sn2++2OH–→Sn(OH)2 ↓
C7H15COOH+OH–→C7H15COO–+H2O
Sn(OH)2+2C7H15COOH→Sn(C7H15COO)2 ↓+2H2O
After the stannous octoate product is produced, it can sink to the bottom of the electrolytic tank due to its high density, the product is easy to take out and purified, and the electrolyte can be reused.
2. Reaction of stannous oxide and isooctanoic acid
Put stannous oxide and isooctanoic acid into the reaction kettle in proportion, start stirring, and vacuum pump. Dehydration reaction at 115-130°C until no distillate comes out and continue the reaction for 2-3 hours, then cool down and filter to obtain the finished product stannous octoate.
The reaction equation is:
Sn+2HCI→SnCI2+H2
SnCI2+2NaHCO3→SnO+2NaCl+H2O+2CO2
SnO+2C7H15COOH→(C–H15COO)2Sn+H2O
The specific steps are:
(1) SnCI2Production: 119kg tin is put into the reactor, and then 208.6kg of hydrochloric acid solution with a concentration of 35% by mass is pumped into the reactor (HCl: Sn molar ratio 2: 1). Raise the temperature to reflux state and react for 18 hours. H2is put into the high air with a vent tube, and the reaction solution is filtered to remove unreacted tin. Concentrate the filtered SnCI dilute solution (Sn2+ mass content 10-12%) until the Sn2+ mass percentage is 30%. The Sn2+ contained in the solution was 117.81kg, and the yield was 99%.
(2) 170.478kg sodium bicarbonate is mixed with the aqueous solution that mass percent composition is 10% and puts into an open reactor. Add the SnCI2 solution prepared in step (1) dropwise at 20° C. (the molar ratio of NaHCO3:SnCI2 is 2.05:1), and control the pH value from 6 to 6.2 to the end of the reaction. The reaction solution after the reaction is centrifugally filtered to obtain stannous oxide.
(3) Put stannous oxide and isooctanoic acid into the reaction kettle at a molar ratio of 1:4, start stirring and vacuum pump. Dehydration reaction at 120 DEG C until no distillate comes out to continue the reaction for 2 to 3 hours, then cooling and filtering to obtain the finished product stannous octoate (Sn2+ content 27 to 28%).
In the end
The above is about two methods for preparing stannous octoate. Electrochemical preparation of stannous octoate can replace the currently widely used metathesis method, which can improve the quality of stannous octoate and reduce costs. The use of stannous oxide and isooctanoic acid can obtain stannous octoate with excellent quality, stability and good oxidation resistance.
Jinbangch has many years of experience in manufacturing stannous octoate, if you want to buy stannous octoate, please contact us!