Study On Green Oxidationhydrazide To Dihydrazide From Cycloolefin

Dibasic acid and dihydrazide have important application value in the medicine,chemistry and construction fields.It is a green path for the synthesis of diacid with cycloolefin and H₂O₂ as raw material and oxidant,respectively.However,,the process is still not industrialized due to the lack of efficient and recyclable catalyst at present,Compare with the industrial homogeneous catalysts,solid catalysts have gradually become the research focus of epoxenes oxidation with their easy separation.Dihydrazide is usually synthesized via two-step（esterification and hydrazide）strategy from adipic acid（AA）,it is difficult to separate catalyst and sulfuric acid can corrode the instrument.A series of solid acid catalysts were prepared for the dibasic acid hydrazidation and the cycloolefins oxidation:WO₃/SO₄^2--ZrO₂-TiO₂,H₃O₄₀PW₁₂·x H₂O-Zr MOF（HPW-Zr MOF）and SO₄^2--ZrO₂-TiO₂ were successfully synthesised in this paper.Three solid acid catalysts were applied for the synthesis of adipic acidand,glutaric acid and adipicdihydrazide,respectively.Then this paper explored the reaction process conditions,catalyst preparation conditions and reaction mechanism.The intrinsic structure-activity relationship among the preparation method,structure characteristics and reaction performance of SO₄^2--ZrO₂-TiO₂ catalyst was systematically studied by selecting adipic acid hydrazide as the probe reaction.It was found that SO₄^2--ZrO₂-TiO₂ catalyst had abundant pore structure（7.15nm）and large specific surface area(347.28m²·g^-1),which could effectively improve the mass transfer efficiency of the catalyst.NH₃-TPD analysis showed that the superacid centre appear at516℃,which was conducive to accelerating the cleavage of C=O in carboxylic acid and improving nucleophilic attack reaction rate of hydrazine hydrate.WO₃/SO₄^2--ZrO₂-TiO₂ catalyst was prepared by introducing WO₃ active site into the SO₄^2--ZrO₂-TiO₂ support,which was employed in the catalytic oxidation of cyclohexene（CHE）to adipate reaction.NH₃-TPD technology research found that SO₄^2--ZrO₂-TiO₂ support could effectively enhance the catalyst acid strength.Studies have shown that when ammonium tungstate was used as the tungsten source,SO₄^2--ZrO₂-TiO₂ was used as the support,and the WO₃ content was 30wt%,the catalyst activity reached the best without solvent（the AA yield is 42.5%）.The preparation conditions of HPW-Zr MOF catalyst was optimized by adopting the cyclopentene green oxidation to produce glutaric acid as a probe.The thermal stability of HPW-Zr MOF catalyst could be effectively improved by embedding HPW molecules into rod-shaped Zr MOF by hydrothermal method.The reaction conditions of cyclohexene oxidation were optimized with WO₃/SO₄^2--ZrO₂-TiO₂ as catalyst.Under optimal reaction conditions(95°C,n CHE:n H₂O₂=1:4.4,25mmol CHE,0.28g WO₃/SO₄^2--ZrO₂-TiO₂ and 6h),the CHE conversion was as high as 92.5%,the yield and selectivity of AA were 52.5%and 56.8%,respectively.The reaction conditions of cyclopentene green oxidation to glutaric acid were investigated with HPW-Zr MOF as catalyst.The cyclopentene conversion reached up to 95.1%,the glutaric acid yield was 62.5%and the glutaric acid selectivity reached 65.7%under the best conditions（26mmol cyclopentene and 110mmol H₂O₂,85℃,7h and 0.19g HPW-Zr MOF catalyst）.SO₄^2--ZrO₂-TiO₂ exhibited excellent catalytic performance in the preparation of adipicdihydrazide from hydrazine adipic acid,the product highest yield reached up to96.27%,the purity was 97.5%and the by-product content was less than 1.0%.The SO₄^2--ZrO₂-TiO₂ catalyst was reusable,and it was found to sustain satisfactory catalytic activity during five consecutive cycles.At this moment,the adipicdihydrazide yield was still higher than 80%.The influence of SO₄^2-on the ZrO₂-TiO₂ electron distribution was studied by DFT calculation.