Study For Selective Hydrogenation To α, β-unsaturated Aldehyde And Security Analysis Of Preparation Process

The synthesis ofα,β-unsaturated alcohols is often from selective hydrogenation ofα,β-unsaturated aldehydes（ketones）that are important chemical raw materials.Theα,β-unsaturated alcohols are defined as fine chemicals with high economic value,which are widely used in cosmetics,fragrances and medicine fileds.It is difficult to obtain a single C=O bond hydrogenation product from those conjugatedα,β-unsaturated aldehydes（ketones）as the thermodynamic more favor of C=C bond hydrogenation than C=O bond hydrogenation.Therefore,It attaches theoretical and practical significance to develop efficient catalysts for single C=O bond hydrogenation inα,β-unsaturated aldehydes（ketones）.Precious metals and organic ligands containing nitrogen and phosphorus are often involved in traditional homogeneous catalytic system with excellent catalytic performance.However,their high cost and the catalytic active components easy to loss are obvious disadvantage for recycle use.Meanwhile,most heterogeneous catalysts with tedious preparation process have poor COL selectivity,which makes it difficult to efficiently catalyze single C=O bond hydrogenation.In view of the above difficulties,three new catalytic systems are brought forward to solve the problem of selective hydrogenation ofα,β-unsaturated aldehydes to produceα,β-unsaturated alcohols with low cost,high efficiency and more safety.（1）The CoPt alloy is formed by doping a small amount of precious metal Pt to improve the Co nanoparticles catalytic performance.Then,The CoPt nanoclusters are anchored on the surface of magnetic Fe₃O₄ to prepare magnetic CoPt/Fe₃O₄ catalyst.The magnetic CoPt/Fe₃O₄catalysts are detailedly characterized by XRD,XPS,HRTEM,H₂-TPD,H₂-TPR and VSM.Subsequently,the effects of different supports（γ-Al₂O₃、TiO₂、Fe₃O₄）and different catalytic active components MPt（M:Fe,Co,Ni）on catalytic performance of selective hydrogenation of cinnamaldehyde are investigated.At the same time,reaction conditions such as solvents,temperature,H₂ pressure and time are optimized for cinnamaldehyde selective hydrogenation over magnetic CoPt/Fe₃O₄ catalyst.Furthermore,the catalytic performance for differentα,β-unsaturated aldehydes is studied and the stability of magnetic CoPt/Fe₃O₄ catalyst is also investigated.The XRD and SEM are used to explain the reason for the magnetic CoPt/Fe₃O₄loss of catalytic activity during recycle tests.Finally,the proposal catalytic mechanism of magnetic CoPt/Fe₃O₄ is put forward.Under the optimum reaction conditions of 160℃,3 MPa H₂,5 mL i-PrOH and 180 min,the conversion of cinnamaldehyde is 94.8%with 84.1%selectivity of cinnamyl alcohol.（2）The low dimensional Co-based nanorods（Co-NRs）are synthesized by solvothermal method,which is applied to loading Pt nanoparticles by impregnation method to prepare the low dimensional Pt/Co-NRs catalyst.Using the low dimensional Pt/Co-NRs catalyst,the transformation of cinnamaldehyde into cinnamyl alcohols with high efficiency could be achieved under low temperature.The XRD,FT-IR,XPS,HRTEM and TGA are used to characterize the low dimensional Pt/Co-NRs catalysts in detail.The effects of Pt loading,alkali and metal salts type,solvents,KOH concentration,temperature,H₂ pressure and duration on the catalytic performance of the low dimensional Pt/Co-NRs are investigated.Then,the catalytic performance of low dimensional Pt/Co-NRs to differentα,β-unsaturated aldehydes（ketones）is studied.Whereafter,the stability of Pt/Co-NRs catalyst is investigated and the reason for the decrease of catalytic activity is explained by TEM after recycle tests.Finally,the appropriate catalytic mechanism of low dimensional Pt/Co-NRs is proposed.Under the optimum reaction conditions of 30℃,2MPa H₂,0.02M KOH and 5mL ethanol,the conversion of Cinnamaldehyde and the selectivity of cinnamyl alcohol are 97.9%and 92.7%,respectively.（3）Four Al-MOFs materials are prepared by hydrothermal synthesis method.Their catalytic performance for catalyzing hydrogen transfer of C=O group inα,β-unsaturated aldehydes（ketones）are investigated using i-PrOH as the molecular hydrogen source.By means of XRD,SEM,BET and TGA,the influence of synthesis conditions（synthesis temperature,regulator,Al/BDC molar ratio,synthesis time）on the catalytic performance of MIL-53（Al）are analyzed.Then,MIL-53（Al）catalytic reaction conditions such as reaction solvents,reaction temperature,catalyst dosage and reaction time are optimized.The MIL-53（Al）catalytic mechanism that unsaturated Al^δ+metal sites act as Lewis acid to promote six-membered ring transition stated are presented.MIL-53（Al）achieves the best catalytic performance under the synthesis conditions of 160℃,n（Al/BDC）=2/1,50 mL DMF,24 h.Finally,under the optimized reaction conditions（180℃,100 mg catalyst dosage,15mL i-PrOH,60 min）,the conversion of cinnamaldehyde reaches 92.7%and the selectivity of cinnamyl alcohos is higher than 99%.（4）The three catalytic processes of cinnamaldehyde conversion into cinnamyl alcohol are analyzed by pre-analysis method.The hazardous chemicals involving in the catalytic process are identified and their properties and hazards are further analyzed.By dividing different operation units,the risk factors and its distribution in each operation unit are identified,meanwhile,occupational hazards and major hazards are identified.In view of the potential safety hazards in above three catalytic processes,the corresponding preventive measures and emergency preplans are formulated to achieve the goal of safe productionα,β-unsaturated alcohols.