| The relationships between methanol formation process and demethoxy process during the alkaline cooking of the reed, silvergrass, wheat straw, bagasse cotton straw and bamboo was studied in this paper. At the same time, the effect of cooking parameters on the methanol formation and demethoxy rate of bamboo, bagasse during the cooking process were studied.It can be regard as two stages of methoxy removal process and methanol produce process during the soda-AQ cooking of reed. Mass demethoxy stage is from initiate to 140℃. Full pressure period is regard as a little demethoxy stage. Methanol formation process were also divide into two stages. One is steam to 80℃,the amount of methanol is a little.The other is mass methanol formation phase which is from 80℃to cooking terminate.The demethoxy process during soda-AQ cooking of bagasse can be divide into two period.The first period is steam to 140℃,the second is from 140℃ to stillstand 60min. The methanol release process is fall into little methanol formation stage and mass methanol formation stage.The former is from 50℃ to the 105℃,the latter is 105℃ to stillstand 60min.The demethoxy stage of wheat straw during soda-AQ cooking include removal methoxy plently and removal methoxy slightly.The two phase respectively is temperature rise from 50℃ to 135℃ and from 135℃ to the terminate.Methanol increasing in the whole process.Compare with bagassel, the methanol formation rate of wheat staw is smaller than bagasse, and the methanol produce process no emerge stage. The demethoxy process of silvgrasses with soad-AQ cooking can be divide into two period.Removal methoxy rapidry is initiate to 125℃,and removal methoxy slowly is 125℃ to the terminate. The initial stage of methanol is from initiate to stillstand 30min and the later stage is from stillstand 30min to 60min. Compare with reed, the methanol generation is less in the whole process, and the rate of methanol produced in the later stage is less volatile, while it is increasing during the soda-AQ cooking of reed.The demethoxy phase of cotton straw during sulfate process is fall into two period.One is from initial to keep 45min, the other one is from keep 45min to keep 180min.In early period, the rate of demethoxy is great. The methanol generation process of cotton straw can be fall into three phase, the first is befor 105℃,the later phase is from 105℃ to cooking tempreture stillstand 45min. From keep 45min to 180min in cooking tempreture is regared as last phase.The demethoxy process and methanol formation process of bamboo with sulfate cooking can be divide into two period.From initial to maximum tempreture is called the first phase, and the demethoxy rate is fester than cotton straw.The second stage is from max tempreture to stillstand 180min. The first stage of methanol generation process is from initial to 105℃.The second stage is from 105℃to terminate.But in the whole process,the amounteof methanol is smaller than cotton straw,however the rate of methanol is greater in the final stage of bamboo cooking.Different materials in relief methanol generation and methoxyl removal rate are different. Two kinds of bagasse generation and methoxyl removal rates have little difference.In addition, the effect of the bagasses and bamboo cooking parameters on methanol formation and demethoxy was studied. The results show that sulfidity, alkali charge, hold time and cooking temperature have a certain effect on methanol release, but to methoxy removal rate have less influece all over. |
