| As a kind of toxic and harmful weed,which Eupatorium adenophorum is hydrolyzed into reducing sugar(Total Reducing Sugars,"TRS")for industrial ethanol production and pharmaceutical foods,this research will be a new way for the resource utilization of Eupatorium adenophorum.In the paper,the preparation of reducing sugar by oil bath heating-magnetic stirring and ultrasonic-microwave assisted hydrolysis of Eupatorium adenophorum was studied.Then the optimum conditions of ultrasonic-microwave-assisted molecular sieve-assisted hydrolysis of Eupatorium adenophorum to produce reducing sugar were optimized by response surface analysis,and the reaction kinetics model of reducing sugar was established by molecular sieve-catalyzed hydrolysis of Eupatorium adenophorum.As a result of the study,the following main conclusions are drawn:(1)In the oil bath heating-magnetic stirring auxiliary hydrolysis reaction,we use nine kinds of catalysts: inorganic acid(sulfuric acid,phosphoric acid,hydrochloric acid),organic acid(p-toluenesulfonic acid,maleic acid,citric acid),molecular sieve(ZSM-5,MCM-41,H?)to catalyze the hydrolysis of Eupatorium adenophorum to obtain reducing sugar.The test shows that the better catalytic effect is sulfuric acid in inorganic acid,the preferred hydrolysis conditions are reaction temperature 94°C,sulfuric acid concentration 20%,liquid-solid ratio 40:1 and reaction time 7h,and the maximum yield of reduced sugar is 23.71%;that the better catalytic effect is maleic acid in organic acid,the preferred hydrolysis conditions are reaction temperature 95°C,catalyst concentration 2.5%,liquid-solid ratio 50:1 and reaction time 5h,and the maximum yield of reduced sugar is 25.33%;that the better catalytic effect is ZSM-5 in molecular sieve,the preferred hydrolysis conditions are liquid-solid ratio 160:1,catalyst dosage 1:1.4,reaction temperature 90°C and reaction time 3 h,and the maximum yield of reduced sugar is 34.26%.(2)In the ultrasonic-microwave-assisted hydrolysis reaction,we use six kinds of catalysts: organic acid(p-toluenesulfonic acid,maleic acid,citric acid)and molecular sieves(ZSM-5,MCM-41,H?)to catalyze the hydrolysis of Eupatorium adenophorum to obtain reducing sugar.The test results show that the better catalytic effect is p-toluenesulfonic acid in organic acid,the preferred hydrolysis conditions are reaction temperature 70°C,catalyst concentration 2%,liquid-solid ratio 70:1,microwave power 500 w,ultrasonic power ratio 55% and reaction time 25 min,and the maximum yield of TRS is 35.71%;that the better catalytic effect is ZSM-5 in molecular sieve,the preferred hydrolysis conditions are liquid-solid ratio 160:1,reaction temperature 60°C,catalyst dosage 1:0.6,microwave power 400 w,ultrasonic power ratio 50% and reaction time 15 min,and the maximum yield of TRS is 30.67%.Compared with the oil bath heating-magnetic stirring hydrolysis reaction,the ultrasonic microwave hydrolysis reaction requires low temperature and is shortened time of 1 to 3h.(3)Through the test of ultrasonic-microwave-assisted molecular sieve-assisted hydrolysis of Eupatorium adenophorum to produce reducing sugar optimized by response surface analysis,the result shows,when ZSM-5 is used as catalyst,the optimal experimental conditions are liquid-solid ratio 175:1,ultrasonic power ratio 60%,reaction time 26 min,reaction temperature 60°C,catalyst dosage 1:0.6 and microwave power 400 w,and the maximum yield of reducing sugar is 31.01%;when MCM-41 is used as catalyst,the optimal experimental conditions are liquid-solid ratio154:1.Catalyst dosage 1:1,microwave power 615 w,reaction temperature 70°C,ultrasonic power ratio 50% and reaction time 25 min,and the maximum yield of reducing sugar is 23.58%;when H? is used as catalyst,the optimal experimental conditions are optimized liquid and solid ratio 142.5:1,microwave power 634 w,catalyst dosage 1:1.6,reaction temperature 60°C,ultrasonic power ratio 60% and reaction time 15 min,and the maximum yield of reducing sugar is 22.42%.(4)The first-order kinetic model is used to study the reaction kinetics of the preparation of reducing sugar by ultrasonic-microwave-assisted ZSM-5 catalyzed hydrolysis of Eupatorium adenophorum.The reaction kinetic model is obtained as follows: x=1-e-(0.0003T-0.0045)t.The reaction activation energy Ea is 25.01 k J·mol-1 and the frequency factor A is 119.85 min-1 by experiments and related calculations.Through the study of ultrasonic microwave assisted hydrolysis of Eupatorium adenophorum,molecular sieve as a separable solid acid and ultrasonic microwave as an ideal process are expected to be applied to industrial production to optimize the production process to improve the yield of reducing sugar. |
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