油茶壳原料制备木糖和高品质活性炭的研究

Preparation of activated carbon and xylose using Camellia oleifera shell as a feedstock

油茶壳中半纤维素含量丰富,可作为制备木糖的潜在原料。笔者通过稀酸(H_2SO_4)水解方法处理油茶壳原料,采用正交实验法详细分析了稀硫酸浓度、反应温度、反应时间3个因素对木糖得率的影响。结果表明:在稀酸质量分数为1.0%、催化温度为80℃、反应时间为2.0 h的最佳反应条件下,可实现最高为98.2%的木糖得率。稀硫酸水解油茶壳的同时也通过酸洗的方式去除了油茶壳原料中的灰分。用磷酸法活化水解后的固体残渣制备活性炭,所得活性炭的碘吸附值和亚甲基蓝吸附值分别为937.9和145.5 mg/g,其灰分仅为0.60%。在相同条件下,以油茶壳作为原料制备的活性炭的碘吸附值和亚甲基蓝吸附值分别为881.5和121.5 mg/g,其灰分为2.40%。采用FT-IR和XRD对水解后的固体残渣进行分析,结果表明稀硫酸催化水解油茶壳主要水解其中的半纤维素,并未水解或破坏其中的纤维素和木质素。本研究中油茶壳的高值化综合利用方法制备出了高得率木糖及低灰分活性炭,实现了油茶壳的全值化利用。

Camellia oleifera shell is a by-product and waste from agriculture and forestry industry. It has abundant reserves on earth and is still unexploited for its high value-added utilization. C. oleifera shell contains high amount of hemicellulose,which can be used as potential raw materials for the preparation of xylose. In this work,dilute sulfuric acid（ H2SO4） was employed as the catalyst to directly hydrolyze C. oleifera shell raw materials. The effects of acid concentration,reaction temperature and reaction time on the final yield of xylose were investigated through orthogonal experiment design. The results showed that the highest yield of xylose of 98.2% was achieved when using1.0% H2SO4 as the catalyst under 80 ℃ for 2.0 h. The H2SO4 not only hydrolyzed the C. oleifera shell but also removed the ash from the C. oleifera shell material at the same time by pickling. The solid residue which generated from the hydrolysis procedure under the optimal condition were used as the raw material to prepare the low-ash content activated carbon by activation with phosphoric acid. It was found that the iodine number and the methylene blue adsorption of the activated carbon prepared from the solid residue with acid hydrolysis treatment were 937.9 mg/g and 145.5 mg/g,respectively,while the iodine number and the methylene blue of the activated carbon prepared from the raw materials without acid hydrolysis were 881.5 mg/g and 121.5 mg/g,respectively. When it came to the ash content,the activated carbon prepared from the hydrolyzed solid residue was only 0.6%,compared with the activated carbon prepared from the raw materials without acid hydrolysis which could be up to 2.40%. The FT-IR and XRD were used to analyze the hydrolyzed solid residue. The results showed that the catalytic hydrolysis of C. oleifera shell by H2SO4 was mainly to hydrolyze the hemicellulose and did not hydrolyze or destroy the cellulose and lignin structure.