25348-97-4Relevant articles and documents
Synthesis method of thiourea
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Paragraph 0018; 0021; 0024, (2020/12/08)
The invention relates to a synthesis method of thiourea. A method for generating thiourea from amine and carbon disulfide under the action of tertiary amine alkali is a common synthesis method adoptedin the prior art; and when the method is used for preparing the thiourea, a byproduct, namely hydrogen sulfide is generate, and the hydrogen sulfide needs to be fully absorbed by an alkali absorptionsystem and also reacts with the tertiary amine alkali to generate an amine salt, so a large amount of a tertiary amine alkali catalyst needs to be added in the reaction. In order to solve the above problem, the invention provides the synthesis method for thiourea; and according to the synthesis method, a proper amount of an inorganic base is added into a reaction system, so the inorganic base cantimely react with the byproduct hydrogen sulfide to form an inorganic salt without a subsequent alkali absorption system, the usage amount of the catalyst tertiary amine alkali can be greatly reduced, and the subsequent recovery work of a large amount of the tertiary amine alkali is also reduced.
Efficient synthesis of aluminium-terminated polyethylene by means of irreversible coordinative chain-transfer polymerisation using a guanidinatotitanium catalyst
Obenauf, Johannes,Kretschmer, Winfried P.,Kempe, Rhett
, p. 1446 - 1453 (2015/04/27)
A series of guanidinato-ligand-stabilised titanium complexes has been synthesised and characterised. These compounds can be prepared by carbodiimide insertion into titanium-amide bonds. Reaction of carbodiimides N,N′-bis(2,6-diisopropylphenyl)carbodiimide, N,N′-bis(2,6-dimethylphenyl)carbodiimide and N-tert-butyl-N′-(2,6-diisopropylphenyl)carbodiimide (2a-2c, respectively) with [(Et2N)TiCl3] led to mono(guanidinato)trichloridotitanium(IV) complexes (3a-3c). Subsequent conversion with methylmagnesium chloride gave the corresponding trimethyl complexes (4a and 4b). Single-crystal X-ray diffraction analyses were carried out for all complexes. Compound 4a showed very high activities in the polymerisation of ethylene in the presence of very high amounts of triethylaluminium and undergoes polymeryl chain transfer to aluminium. Irreversible coordinative chain-transfer polymerisation and a unique combination of catalyst economy and high activity were observed. In the presence of 1000 equivalents of aluminium, a chain elongation of 83.3 % could be achieved with an activity of 9900 kgPE molcat-1 h-1 bar-1. The influence of the steric demand of the ligand on the polymerisation capability is significant and was investigated too. A series of novel mono(guanidinato)titanium(IV) complexes has been synthesised and characterised. Single-crystal analyses were performed for all complexes. Compound 4a showed very high activities in the polymerisation of ethylene in the presence of very high amounts of aluminium after activation with fluorinated borates. Irreversible coordinative chain transfer to aluminium was observed.
