Synthesis Of CLT Acid And Related Pigments From O-chlorotoluene

Since o-chlorotoluene is a byproduct of manufacture p-chlorotoluene, its soure is abandent and price is also cheap. Therefore, the synthesis of CLT acid from o-chlorotoluene is becomeing a popular topic. At present, the synthesis of CLT acid by bromination of o-chlorotoluene has been widely researched, unfortunately, this method still not finds application in industrial production, because of higer requirements for equipment and cost.This paper made a systematic study of synthesis of CLT acid through nitration of o-chlorotoluene. The target compound was synthesized by using o-chlorotoluene as starting material by nitration, reduction and sulfonation. In these process the yield of CLT acid mainly is decided by nitratin. In order to achieve high selectivity of nitration, we made a large amount of experiments, improved the mixed-acid nitration. Details are as follows:(1)The best nitration result was obtained by zeolite-beta in its proton form as catalyist and acetyl nitrate as nitrating agent, and the yield of main product was approximately 78.38%.(2) After improvement of the process of mixed acid nitration, the yield of main product was raised to 53.06%. Through brief treatment, the waste acid can be reused in sulfonation, therefore, waste acid pollution was minimised.(3) Instead of H2/Ni,2-chloro-5-nitrotoluene was reducted by iron, reducted product was isolated by steam distillation, in distillate donot exist any residual Fe3+. 2-chloro-5-aminotoluene was further purified by recrystallization.2-chloro-4-aminotoluene was isolated from mother liquor, used for the synthesis of 2B acid.(4)Solvent was applied for sulfonation and the solvent can be uesd repeatedly and continuously.(5) Lake Red C,the red pigment R1 and R2 were synthetised from CLT acid、2B acid and Component B, and yellow pigment Y was synthetised from the component A.As a result, nitration, reduction, isomer separation and sulfonation process were improved. Overall yield of CLT acid was 61%. And we also exploited the application of byproducts.