Process method for preparing cyanamide by catalyzing urea dehydration

A process method, the technology of cyanamide, applied in the field of urea dehydration to prepare cyanamide, and the design of new catalytic system, can solve the problem of low selectivity of cyanamide, achieve simple raw materials, improve the conversion rate of urea and cyanamide The effects of selectivity and easy access to raw materials

Pending Publication Date: 2022-07-15
TIANJIN UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0008] Aiming at the problems of many by-products and low selectivity of cyanamide in the process of preparing cyanamide from urea dehydration, the present invention designs a method for preparing cyanamide by catalytic urea dehydration using Nano-ZSM-5 catalyst

Method used

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  • Process method for preparing cyanamide by catalyzing urea dehydration
  • Process method for preparing cyanamide by catalyzing urea dehydration
  • Process method for preparing cyanamide by catalyzing urea dehydration

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] Preparation of Na-type Nano-ZSM-5 catalytic material with Si / Al ratio of 20:

[0035] Dissolve 10.0 g of template TEOS in 32.5 mL of deionized water, and use concentrated H 2 SO 4 Adjust the pH value to 1 and stir for 20h. Add 1.2g TPA-Br and 0.75gAl 2 (SO 4 ) 3 , using 1mol / L NaOH solution to adjust the pH value to 10, and aging for 10h. The aged mixed solution was put into a 100 mL crystallization kettle equipped with a polytetrafluoroethylene lining, and the temperature was kept at 180° C. in an oven for 72 hours. Suction filtration, drying at 60°C overnight. The catalyst was calcined in a muffle furnace at 550 °C for 6 h to obtain the final Na-type Namo-ZSM-5 catalyst.

Embodiment 2

[0037] Preparation of H-type Nano-ZSM-5 catalytic material with Si / Al ratio of 20:

[0038] Use 1mol / LNH before use 4 The Cl acid was exchanged 4 times, each exchange time was 2h, the exchange temperature was 90°C, after the exchange was completed, suction filtration, and drying at 60°C overnight. The muffle furnace was activated at 550 °C for 3 h to obtain the final Namo-ZSM-5 catalyst.

Embodiment 3

[0040] Take 8ml of the prepared H-type Nano-ZSM-5 catalytic material and fill the fixed bed reactor with 75g of glass beads, 10g of quartz sand, 8ml of catalyst and 8g of glass beads respectively in the fixed bed reactor in the order from bottom to top. Subsequently, the reaction was carried out at 550° C., the residence time was 0.5s, and the reaction time was 30min under the condition of ammonia gas atmosphere. The product was cooled by a serpentine condenser to obtain product crystallization, and the volume was constant with a 250ml volumetric flask.

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Abstract

The invention relates to a process method for preparing cyanamide by urea dehydration, which comprises the following steps: (1) filling a fixed bed reactor with a certain amount of Nano-ZSM-5 catalyst, the usage amount of the catalyst being related to the reaction retention time; (2) filling the dried solid urea into a fixed bed urea feeding device, and heating to 150 DEG C at a heating rate of 1 DEG C / min; (3) pushing the molten urea at a constant speed at a reaction temperature of 550 DEG C in an ammonia gas atmosphere at a constant pushing speed; and (4) collecting product crystals at low temperature, and fixing the volume by using a volumetric flask. Compared with a common ZSM-5 catalyst, the used catalyst has larger pore volume and pore diameter and specific surface area, and has more acidic sites. When the catalyst is applied to a process for preparing cyanamide through urea dehydration, the urea conversion rate and the cyanamide selectivity can be effectively improved, generation of byproducts such as dicyandiamide, biuret and melamine is reduced, the urea conversion rate reaches 90% or above, and the cyanamide selectivity is larger than 30%. The process method has a good application prospect in large-scale industrialization of the process for preparing the mono (bis) cyanamide through urea dehydration.

Description

technical field [0001] The invention relates to the technical field of chemical catalytic reactions, and belongs to the design of a novel catalytic system and a new technological research method for preparing cyanamide by dehydration of urea. Background technique [0002] Monocyanamide is an important chemical raw material, an organic chemical intermediate, and a very important pharmaceutical raw material. It can also be used as an intermediate in pesticide products to produce pesticides. In addition, cyanamide can also be used in health care products and feed additives. Synthesis, the synthesis of pesticide intermediates and the synthesis of flame retardants, etc., have a wide range of uses. At present, their application research is actively carried out at home and abroad, and the market prospect of cyanamide is relatively optimistic. [0003] In terms of pharmaceutical raw materials, cyanamide is mainly used to produce cytarabine hydrochloride, intermediate 3-amino-5-hydro...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C277/08C07C279/24C01C3/16B01J29/40
CPCC07C277/08C01C3/16B01J29/40C07C279/24
Inventor 吕树祥董利兵许晓安
Owner TIANJIN UNIV OF SCI & TECH
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