- A quantitative one-pot synthesis method for industrial azo pigments with recyclable wastewater
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Most industrial azo pigments are synthesized by diazotization in one pot and then coupling in another. This two-pot process has been transformed into a one-pot method by adding granular PTFE (polytetrafluoroethylene) to a mechanically agitated aqueous mixture of NaNO2, HCl, a diazo component and a coupling component. This method avoids the step of using a base or a surfactant to dissolve the coupling component. The reactions were fast and quantitative. The granular PTFE, wastewater and excess HCl were then reused 11 times without deteriorating the reaction rate and product purity. Altogether, 22 industrial pigments and 3 azo compounds were synthesized and the reaction can produce up to 22.7 g of product in the laboratory. Some reactions require less than 2 equiv. of HCl and a mechanism explaining this is proposed. In addition, an o-nitro group effect is advanced to explain the differences in coupling reaction rates for o-, m- and p-nitroaniline.
- Feng, Guangyuan,Zhu, Meiling,Liu, Lei,Li, Chunbao
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supporting information
p. 1769 - 1776
(2019/04/08)
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- Method used for synthesizing azo compound using solid particle one kettle method
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The invention relates to a method used for synthesizing an azo compound using solid particle one kettle method. The method comprises following steps: solid particles are introduced into a reaction container, an inorganic acid, an aromatic primary amine, sodium nitrite, water, and a coupling component are added, mechanism stirring is carried out, when the reaction is monitored to be finished, filtering and rinsing are carried out, and the obtained filter cake is a finished product; or the solid particles are introduced into the reaction container, the inorganic acid, the aromatic primary amine,sodium nitrite, and water are added, mechanical stirring is carried out, after complete conversion of the aromatic primary amine, the coupling component is added, mechanical stirring is carried out,when the reaction is monitored to be finished, filtering and rinsing are carried out, and the obtained filter cake is a finished product. The solid particles are preferably selected from polytetrafluoroethylene particles, haw seeds, or stainless steel sand. The solid particles are added into the reaction system to promote reaction, no pre-heating or alkali adding dissolving of diazo components orthe coupling component is needed; most reaction is finished in 1h; reaction time is short; product quality is high; and reaction filtrate and excess inorganic acid can be recycled for a plurality of times.
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Paragraph 0115; 0116; 0117
(2019/01/07)
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- Method for preparing azo compounds with narrow particle size distribution
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The invention relates to a method for preparing azo compounds with narrow particle size distribution. The method mainly comprises the following steps: coating the surfaces of titanium dioxide particles with narrow particle size distribution, with a coupling component to obtain titanium dioxide particles with surfaces coated with the coupling component; performing a coupling reaction between the obtained titanium dioxide particles with surfaces coated with the coupling component and a diazonium salt component to obtain target objects. According to the method provided by the invention, azo compounds with narrow particle size distribution (especially azo compounds with D90 between 0.10mum and 0.15mum) can be prepared by a relatively simple method, and the problems (including complex and lengthy steps, expensive high-precision sanding machinery and the like) of the prior art are overcome.
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Paragraph 0028; 0029; 0030; 0031; 0032; 0033; 0034-0036
(2018/03/25)
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- A Simple Route for the Synthesis of Chlorosubstituted Arylazobenzenes, Arylazonaphtalenes, and Arylazopyrazoles
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The reaction of arylazophenoles and arylazohydroxypyrazoles (or their tautomer hydrazones) 10, 11, and 15 with POCl3 in dimethylformamide yields chlorosubstituted arylazobenzenes or arylazopyrazoles 12, 13 and 16, resp., in moderate to high yields.The substitution of the OH-group by the Cl-moiety is favoured by acceptor substituents in the aryl fragments ortho- and/or para-linked to the azo group.In case that arylazocompounds derived from resorcinol are used the substitution reaction runs in a stepwise manner giving raise to the formation of o-hydroxy-p-chlorosubstit uted azo compounds 18 primarily and then of dichlorosubstituted azo compounds 19.
- Guenther, R.,Jaehne, E.,Hartmann, H.,Schulze, M.
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p. 945 - 954
(2007/10/02)
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