Two-step pyrolysis characteristics of bean stalks

Two-step pyrolysis of soybean stalk was investigated using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The results indicate that with the increase of the first-step pyrolysis temperature (t₁), the total peak area of the first-step products becomes higher. However, for the second-step, the total peak area decreases gradually with the increase of t₁. The products in the first-step pyrolysis have higher contents of acids, ketones and furans when t₁ is 400 or 450 ℃. This is because that the products are originated from cellulose and hemicellulose. The content of hydrocarbon products in the second-step is more than 20% when t₁ is 450 or 500 ℃. With two-step pyrolysis some products with high content can be obtained in the first or second step, respectively, such as acetic acid, furfural, guaiacol, methylbenzene and benzene etc., thus preliminarily achieving the selective pyrolysis of biomass.