利用添加劑與載體改質鈷硼觸媒於硼氫化鈉水解產氫之研究; Hydrogen Production from Catalystic Hydrolysis of NaBH4 solution with modified CoB by using supports and additives

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Title:	利用添加劑與載體改質鈷硼觸媒於硼氫化鈉水解產氫之研究;Hydrogen Production from Catalystic Hydrolysis of NaBH4 solution with modified CoB by using supports and additives
Authors:	王承宇;Chen-Yu Wang
Contributors:	化學工程與材料工程研究所
Keywords:	硼氫化鈉;產氫;鉬;鎢;二氧化矽;二氧化鈦;TiO2;SiO2;Co;Mo;hydrogen generation;sodium borohydride
Date:	2009-06-19
Issue Date:	2009-09-21 12:30:44 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	本研究以硼氫化鈉為還原劑，醋酸鈷為前驅鹽類製備出鈷硼非晶相觸媒，用於硼氫化鈉溶液的水解反應，以鈷硼觸媒為我們反應之觸媒主體，輔以一連串之改質觸媒方式，希望藉由改變觸媒之物理或化學性質以提高產氫速率，此一系列之改質鈷硼觸媒以X-光繞射儀、氮氣吸附儀、穿透式電子顯微鏡、X-光光電子能譜儀等儀器鑑定其物理及表面性質。 CoB活性約為(2400 ml•g-1•min-1)，嘗試以鉬、鑭、鋅、鎢四種添加劑加以改質，其中鉬、鎢元素能提高原素態鈷的含量，表面積也隨之提升，而鉬與鎢均提供部分電子轉移給鈷，其氧化物提供良好的分散作用，降低觸媒聚集的機率，因此觸媒整體活性約提升原CoB觸媒的兩倍，MoCoB的活性達5050 ml•g-1•min-1，WCoB的活性達5464 ml•g-1•min-1。 CoB對於硼氫化鈉產氫反應具有良好活性，但是其具有易氧化、易聚集的缺點，因此我們選用SiO2、Al2O3、TiO2、CeO2以及ZrO2等擔體來改質CoB 觸媒，CoB/SiO2觸媒具有高的比表面積以及較高的Co元素態比例，同時CoB/SiO2、CoB/TiO2觸媒中有較明顯的電子轉移情形，因此兩者的活性表現也較為突出約有原始CoB的三倍，CoB/SiO2的活性達10586 ml•g-1•min-1，而CoB/TiO2活性達8159 ml•g-1•min-1。選用改質效果較佳之擔體、促進劑同步進行改質，故選用Mo-CoB/SiO2, W-CoB/SiO2, Mo-CoB/TiO2 and W-CoB/TiO2等觸媒進行反應性測試，而Mo-CoB/SiO2具有較佳的活性，顯現出在擔體上，鉬元素仍具有促進效果，能進一步提升CoB/SiO¬2的活性，而鎢則不具有促進效果，同樣的結果也顯現在CoB/TiO2上。 Amorphous CoB catalyst was prepared by cobalt acetate using sodium borohydride as the reducing agent in this research. The main reaction was hydrolysis of sodium borohydride solution. Different additives were added into CoB to modify its physical and chemical properties in favor of better hydrogen generation rate. The series of modified CoB catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The hydrogen generation rate for CoB catalyst is about 2400 ml•g-1•min-1. We use four kinds of additives: Mo, La, Zn and W to modify our CoB catalyst. Among these additives, Mo and W can raise the molar ratio of elemental Co which was thought as the active site to the reaction. The oxides of Mo and W can provide dispersion effect, and raise the surface area of the catalyst. Also, the Mo and W can transfer partial electron to Co. Finally, the activity of modified CoB can raise about two times which the hydrogen generation rate of Mo-CoB is 5050 ml•g-1•min-1 and W-CoB is 5464 ml•g-1•min-1. CoB has proved owns good catalytic activity to hydrolysis reaction. There are some disadvantages to CoB catalyst that it is easy to oxide and aggregate. We choose SiO2、Al2O3、TiO2、CeO2 and ZrO2 as our supports to modify CoB catalyst. CoB/SiO2 catalyst has the higher specific surface area and higher molar ratio of Co0. The electron transfer effect is more apparent to CoB/SiO2 and CoB/TiO2.Therefore, the activities of these two catalysts is outstanding that can achieve about three times than original CoB catalyst. The hydrogen generation rate of CoB/SiO2 is 10586 ml•g-1•min-1 and CoB/TiO2 is 8159 ml•g-1•min-1. We found Mo and W had good promotion effects and CoB supported on SiO2 or TiO2 showed good catalytic activities. Therefore, we use Mo-CoB/SiO2, W-CoB/SiO2, Mo-CoB/TiO2 and W-CoB/TiO2 to test our activity. The result is that Mo-CoB/SiO2 can show the better activity. This may indicate that on the support, Mo can show the promoting effect but W can’t. The same situation is appeared to CoB/TiO2. The hydrogen generation rate is 13620 ml•min-1•g-1 to Mo-CoB/SiO2.
Appears in Collections:	[National Central University Department of Chemical & Materials Engineering] Electronic Thesis & Dissertation

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