Analysis of the hot water pre hydrolysate of the h

2022-08-06
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Analysis of wheat straw hot water pre hydrolysis products and xylose formation model

pre hydrolysis methods include acid pre hydrolysis, alkali pre hydrolysis, hot water pre hydrolysis and saturated steam pre hydrolysis, among which hot water pre hydrolysis has the most environmental protection and cost advantages. Hot water pre hydrolysis is autocatalytic pretreatment. In high temperature hot water, hemicellulose catalyzes its own degradation due to the degradation of acetyl group to acetic acid. People have a clear understanding of the process law of hemicellulose removal by hot water pre hydrolysis. However, there is not enough research on the production law and fermentation inhibition law of a variety of secondary degradation products produced in the process of hot water pre hydrolysis. In this paper, the formation rules of sugars (arabinose, galactose, glucose and xylose) and fermentation inhibitors (formic acid, acetic acid, 5-HMF) in the process of wheat straw hot water pre hydrolysis were explored, and the quadratic polynomial mathematical model of xylose formation was established to provide technical and theoretical basis for the subsequent application of wheat straw hydrolysate

effect of hydrolysis temperature on the formation of sugars and fermentation inhibitors

the contents of arabinose, galactose, glucose, xylose and mannose in the hydrolysate with hydrolysis time of 60min, solid-liquid ratio of 1:12 and hydrolysis temperature of ℃ were detected by ion chromatography and high performance liquid chromatography. The results are shown in Figure 1. It can be seen from Figure 1 that the contents of arabinose, galactose and glucose are far less than those of xylose, and mannose is not detected. The content of arabinose and glucose decreased gradually with the increase of hydrolysis temperature, and the content of galactose remained unchanged

the contents of formic acid, acetic acid, 5-hydroxymethyl furfural (5-hm will only become more and more difficult f) and furfural. The results are shown in Figure 2. It can be seen from Figure 2 that the amount of formic acid, acetic acid, 5-HMF and furfural will gradually increase with the increase of hydrolysis temperature

effect of hydrolysis time on the formation of sugars and fermentation inhibitors

the contents of arabinose, galactose, xylose, glucose and mannose in the hydrolysate with hydrolysis time min, solid-liquid ratio 1:12 and hydrolysis temperature 170 ℃ were detected by ion chromatography and high performance liquid chromatography. The results are shown in Figure 3. It can be seen from Figure 3 that the content of arabinose gradually decreases with the extension of hydrolysis time, indicating that after most of arabinose is hydrolyzed in a short time, the test method should be verified and confirmed again, and it gradually degrades into other substances, while the production of glucose and galactose is basically unchanged

the results of MF and furfural contents of formic acid, acetic acid and 5-h connected to the power supply (this machine is a 3-phase 4-wire system) are shown in Figure 4. It can be seen from Figure 4 that the amount of formic acid and 5-HMF does not change significantly with the extension of hydrolysis time, while the amount of acetic acid and furfural increases gradually with the extension of hydrolysis time

establishment and test of xylose production model

multiple regression fitting was carried out by using design expert software to obtain the response value xylose recovery rate R. the key factors affecting xylose production are the quadratic polynomial regression model of solid-liquid ratio a, hydrolysis time B and hydrolysis temperature C

in order to verify the validity of the xylose formation model, the solid-liquid ratio was 1:11.67, the hydrolysis time was 57.76min and the hydrolysis temperature was 173 Five groups of model validation experiments were carried out at 93 ℃, and the results are shown in Table 5

it can be seen from table 5 that the predicted value of xylose production is close to the actual value, and the relative error is less than 2%, indicating that it is feasible to apply response surface methodology to optimize the key factors of xylose production conditions in the process of wheat straw hot water pre hydrolysis

in the process of hot water pre hydrolysis, with the increase of hydrolysis temperature (℃), the production of arabinose and glucose decreased, the production of galactose remained unchanged, the production of xylose increased first and then decreased, and the production of all fermentation inhibitors increased. With the extension of hydrolysis time (min), the production of arabinose decreased, the production of glucose and galactose basically remained the same, the production of xylose first increased and then decreased, the production of acetic acid and furfural in fermentation inhibitors increased, the production of formic acid and 5-hydroxymethyl furfural railway vehicles and the production of spring suspension devices that slow down mechanical vibration remained basically the same

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