臺灣博碩士論文加值系統

摘要 稻殼含熱值約3439 kcal/kg (約為省產煙煤熱值的60%），而且
硫及氯的含量低於0.1 wt.%，顯示稻殼具能源回收的價值；稻殼含15~20
wt.%灰份，灰份中含高純度氧化矽（SiO2＞93 %），可作為合成沸石之矽
源。 沸石是鹼金屬或鹼土金屬的矽鋁酸鹽化合物，沸石具高活性的酸
性催化能力、陽離子交換能力(cation exchange capacity)及分子篩特性
，工業應用包含非均相催化劑、吸附劑與氣體分離。ZSM-5沸石為三度空
間的孔洞結構，具有長直狀孔道(straight channel)及曲折狀孔道(zig-
zag channel)，孔洞大小分別為5.1 A×5.5 A及5.4 A×5.6 A，ZSM-5沸
石具優越之分子形狀選擇性（反應物或生成物選擇性），及高熱穩定性等
特殊性質。 稻殼灰可合成ZSM-5結構的沸石，合成時間40小時以上可
達100%結晶度，合成沸石的飽和吸附量是美孚(Mobil)公司商業化ZSM-5沸
石80%~90%，表面酸性研究指出沸石表面活性基有SiOH、SiOH(NC)、
AlSiOH等Br"nsted酸性活性基及Lewis酸性活性基；IR光譜分析指出苯在
合成沸石ZSM-5孔道(channel)內產生冷凝吸附現象，以液態存在結構內，
苯在合成沸石ZSM-5表面擴散時，吸附溫度愈高其擴散速度愈快（3.48
×10^-11~7.74×10^-11, cm2/s），吸附質的濃度愈高所造的濃度梯度也
會使擴散速度愈快，擴散速率也隨Si/Al比值的增加而增加；苯在合成沸
石ZSM-5的擴散活化能為20.68 kJ/mole。 合成沸石除可應用於石化和
煉油工業製程，其高熱穩定性可發展為汽、機車觸媒轉化器之前置吸附劑
，以有效控制冷起動之排放污染，解決都會區之空氣品質惡化問題；未來
將保留生質無機特性應用於光化學觸媒。

Abstract Rice husk is a
major by-product of the rice-milling industries and is abundary
available. Zeolite ZSM-5 was prepared from a reaction mixture
containing a source of silica (rice husk ash), an organic
compound (tetrapropyl -ammonium, TPA), an alkai metal oxide
(sodium oxide) and water.The mixture was mainatined at 443 K and
20 atm approximately in a stain less-steel autoclave for at
least 40 hours.Structure and mophology of synthesized zeolites
were determined by X-ray diffraction (XRD) and scanning/
transmission electron microscope (S/TEM) spectra. Adsorption
isotherms and diffusivities of benzene in ZSM-5 was also
investigated by the TGA in the temperature range 300-423 K. The
activation energy for diffusion of benzene in the synthesized
ZSM-5 is Ea=20.68 kJmol-1. Furthermore, the infrared difference
spectra also shows that benzene molecules have a high
selectivity for adsorption on the energetic acied sites first.
Four types of active acid sites on ZSM-5 were also identified
SiOH, SiOH(NC), AlSiOH and Lewis acid sites by infrared
spectroscopy.