Study On The Conversion Of Glucose To Levulinic Acid Catalyzed By Solid Acid

Levulinic acid (LA), which can be prepared from biomass, is an important chemical raw material whose applications will be wider and wider in various industries. So, LA can become a new green platform chemical. But the traditional preparation processes of LA from biomass using liquid acid catalysts such as hydrochloric acid and sulfuric acid. Since these liquid acids are corrosive and produce a large amount of waste, replacement of the liquid catalysts with solid acid catalysts is desirable for developing environmentally benign process.The methods for the determination of 5-HMF and LA by an ion chromatograp in the glucose hydrolyzate were developed respectively. After handling samples simply, they were analyzed by Dionex ICS-3000 ion-exchange chromatography with elution consisting of sodium hydroxide. The column temperature was 30℃. After optimized analysis conditions, linear dependence, correlation coeffient, detection limits and repeatability were obtained by experiments.In this work, the hydrolysis behaviors of glucose to LA over three types solid acid catalysts included solid super acid SO₄^2-/TiO₂-Al₂O₃-SnO₂, zeolite molecular sieve ZSM-5 and self-prepared catalyst SO₄^2-/ZrO₂ supported on ZSM-5. The optimum synthetic conditions were established.SO₄^2-/TiO₂-Al₂O₃-SnO₂ is a kind of composite bearing base solid super acid, and exhibited good catalytic activity in the reaction of hydrolysis of glucose to produce LA. It was found that the highest yield of LA can reach 74.05% (molar percent) in the conditions of the amount of catalyst 3g, reaction temperature 180℃, reaction time 2h and mass concentration of glucose 20g/L. Surface structure changes of catalyst before and after the reaction were also analyzed, indicating that carbonization covered the surface catalyst was the main reason of catalyst deactivation. The recycling utilization of regenerated catalysts was also examined.ZSM-5 is a kind of high silica and five-membered ring zeolite and its basic cell structure is made up of eight five-membered rings. Results show that under the optimal conditions as follows: the amount of catalyst 3g, reaction temperature 190℃, reaction time 2.5h, the levulinic acid yield can reach 69.32%(molar percent). Surface structure changes of catalyst before and after the reaction were also analyzed. When the carbonization was removed by baking method,the yield of LA was 57.02% catalyzed by the regenerated catalysts.After tentative exploration, the preparation of SO₄^2-/ZrO₂ supported on ZSM-5 was studied. The influence of the SO₄^2-/ZrO₂ loading,impregnation concentration of sulfuric acid,and the calcination temperature on catalyst activity was invested, so that the optimum praparation conditions for catalyst were found. The process conditions of hydrolysis of glucose to produce LA catalyzed by self-prepared catalyst were also studied.