Continuous production process of dinitrotoluene for synthesis of toluenediamine by low-pressure hydrogenation, catalyst and catalyst preparation method

Abstract

The invention discloses a process for continuously producing toluenediamine through low-pressure hydrogenation synthesis of dinitrotoluene. The process comprises the steps of preparing a fresh Raney nickel catalyst and dinitrotoluene into fresh catalyst slurry, and adding the fresh catalyst slurry into a hydrogenation reactor; respectively adding raw materials, namely, dinitrotoluene and hydrogen into the hydrogenation reactor to react, overflowing a liquid-phase reaction product into a clean reactor, pumping the liquid-phase product in the clean reactor into a catalyst thickener, enabling gases to enter a purge gas separator from the top, returning the thickened catalyst slurry to the hydrogenation reactor, delivering clear liquid into a filter for filtering to obtain a crude toluenediamine product. The process has the advantages of low equipment investment, low energy consumption and capability of synthesizing toluenediamine through dinitrobenzene hydrogenation under the conditions that no additional solvent is added and the low pressure is kept at about 1MPa.

Description

Technical field [0001] The invention belongs to a process for synthesizing toluene diamine, and in particular relates to a continuous production process for synthesizing toluene diamine by low-pressure hydrogenation of dinitrotoluene, and a method for preparing the used Raney nickel catalyst and the catalyst. Background technique [0002] Toluene diamine (TDA), also known as diaminotoluene, is an important chemical raw material and chemical intermediate, mainly used in the synthesis of polyurethane materials. In industry, toluene diamine is usually synthesized by hydrogenation of dinitrotoluene (DNT) in the presence of an organic solvent and a catalyst. At present, there are two main DNT hydrogenation technologies: the first is to use supported Pd / C and Pt / C The DuPont technology of Sweden and the United States of other precious metal catalysts has the advantages of low reaction pressure and high catalyst activity, but it has the disadvantages of difficult catalyst separation, ex...

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Problems solved by technology

[0008] In order to achieve the above-mentioned purpose, the present invention breaks through the shackles of conventional technical cognition that nickel-based catalysts need to add solvents and reaction pressures up to 2MPa in the hydrogenation reaction of dinitrotoluene, and through a large number of catalyst modification experiments, activity evaluation experiments and mechanism research The analysis screened and compared various nickel-based catalysts, and successfully developed a Raney nickel catalyst with activity similar to noble metal catalysts under the condition of low pressure 1MPa and no external solvent; and according to the catalytic performance of the developed Raney nickel catalyst, Strength and settling properties, through a large number of theoretical calculations and experimental research, a new process for the continuous production of toluenediamine by hydrogenation of dinitrotoluene was further developed; the invention of a new process for the hydrogenation of dinitrotoluene with Raney nickel catalyst It not only completely overcomes the shortcomings of the existing two industrial DNT hydrogenation technologies, but fundamentally solves the two industrial dinitrotoluene hydrogenation technologies such as Sweden and DuPont in the United States. The problems existing in the reaction with BASF technology require additional solvent, high reaction pressure and large investment in equipment

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