Nitro hydrogenation catalyst for the pigment Gold Glow Red!

Chinese people love red, the New Year's red envelope, the wedding add red makeup, the days to live red hot, stars also want to red purple, it is clear that the status of red in the hearts of the country is very high. During the New Year holidays, the country's streets are decorated with all kinds of red. Among them, there is a kind of golden red, with its bright colors and golden luster can best accentuate the festive atmosphere, but also naturally the most popular.

Golden red belongs to the β-naphthol class of single azo pigments, mainly used to manufacture ink and used in rubber, educational supplies coloring. Like our New Year hanging red lanterns, stickers, and red packets, are colored with this pigment, it is said that the Chinese brand cigarette packaging is also used in the golden red!

CLT acid, abbreviated as C acid, chemical name 2-chloro-5-aminotoluene-4-sulfonic acid, is a very important red organic pigment intermediate, can synthesize golden red, plastic big red, Xinbao red 36b and other color precipitated organic pigments. China's CLT acid production ranks first in the world, and the amount is also the largest. 

Traditional CLT acid synthesis using 2-chloro-5-nitrotoluene-4-sulfonic acid by iron powder reduction, due to the iron powder reduction process energy consumption, heavy pollution, this process has been eliminated. The existing production of CLT acid adopts green catalytic hydrogenation process, which can significantly reduce energy consumption and solid waste generation.

The catalytic hydrogenation production of CLT acid is nitrobenzene hydrogenation, but the key to its hydrogenation technology is that there are also Cl atoms and sulfonic acid roots in the molecule, which will be accompanied by the side reaction of decluttering in the process of hydrogenation, and the presence of sulfonic acid roots will also increase the toxicity of the catalyst, resulting in a decrease in product purity and high catalyst consumption. 

2-chloro-5-nitrotoluene-4-sulfonic acid catalytic hydrogenation production The commonly used catalysts for CLT acid are: Pt/C, Pd/C and other noble metals and Ni, Cu and other transition metals two types of catalysts. Good results were achieved in the preparation of CLT acid using Pd/C as the catalyst, and the selectivity of CLT acid reached 98.0% under the condition of adding dechlorination inhibitor, but it was difficult to industrialize the precious metal catalysts due to high cost. 

The use of conventional skeletal nickel for the preparation of CLT acids by liquid-phase hydrogenation is accompanied by severe dechlorination side reactions, which will be improved to some extent by adding a certain amount of dechlorination inhibitor. If the high selectivity of CLT acid can be achieved by improving the catalyst and hydrogenation process to 2-chloro-5-nitrotoluene-4-sulfonic acid with the combination of suitable nickel catalyst and dechlorination inhibitor, it will be an effective means to solve the industrialization of CLT acid catalytic hydrogenation production.