Investigation On The Condensation Of Glycerol And Cyclohexanone Using Soild Catalysts

The condensation of cyclohexanone with glycerol catalyzed by varies solid acid catalysts was investigated aiming to study the effects of catalyst's structure and the acid property on the conversion of cyclohexanone and the reaction selectivity. The reaction parameters of the synthesis cyclohexanone glyceryl ketal were optimized. In order to further improve the catalytic activity and investigate the influence of catalyst acidic properties on the catalytic activity, acid-treated montmorillonite and molecular sieve Hβwere modified by loading Lewis acid and protonic acid treatment. Finally, ab initio HF method with 6-31G* basis set level was employed to preliminary study the mechanism of the reaction catalyzed by acid.The result indicates that Hβmolecular sieve are the excellent catalysts for this reaction. Acid-montmorillonite showed better catalytic activity than HY and HZSM-5 molecular sieve because of its mesopore structure. Solid superacid SO₄^2-/Fe₂O₃ and H₂SO₄/C also showed good catalytic activity. Acidification treatment of activated carbon increased its acid content from 0.16mmol/g to 1.83 mmol/g, therefore its catalytic activity was improved. The highest conversion of cyclohexanone and the selectivity of 1,4-dioxaspiro[4,5]decane-2-menthanol reached 99.5% and 98.5% in 1h, respectively, by using Hβmolecular sieve as the catalyst under the optimum reaction conditions: 0.02g Hβmolecular sieve, 0.1mol cyclohexanone, 0.15 mol glycerol, 10ml cyclohexane under refluxing; and the optimum calcination temperature of Hβmolecular sieve was 500oC.As montmorillonite modified by loading FeCl3 and AlCl3, the conversion of cyclohexanone were improved from 69.8% to 77.8% and 74.7%, respectively. This is because the acid content of the catalysts were increased obviously. But the negative result was obtained when using montmorillonite modified by loading ZnCl2 as the catalyst, probably because the reducing specific surface area of the catalyst. The optimum crop load of FeCl3 was 1mmol/g.The conversion of cyclohexanone catalysised by molecular sieve Hβmodified by FeCl3 was improved from 94.6% to 94.9%, but the catalytic activity were decreased when it modified by protonic acid. Thus we hypothesize that the B acid sites and the strong acid site are favorable to this reaction.Quantum chemical method was employed to preliminary study the mechanism of acid catalyzed the reaction. The transition state of the reaction between glycerol and cyclohexanone carbocations was acquired. By using frequency analysis and inner reaction coordinate analysis the rationality of this transition state was affirmed. And the energy barrier of this reaction using protonic acid and AlCl3 are 120.016kJ/mol and 164.774kJ/mol, respectively, and the energy difference is 44.757kJ/mol. Thus, protonic acid has better catalytic activity.