(3.227.0.150) 您好!臺灣時間:2021/05/06 12:47
字體大小: 字級放大   字級縮小   預設字形  
回查詢結果

詳目顯示:::

我願授權國圖
: 
twitterline
研究生:詹朝安
論文名稱:高抗硫性加氫飽和觸媒之開發
論文名稱(外文):Developing Hydrogenation Catalysts of High Sulfur Resistance
指導教授:張仁瑞
學位類別:碩士
校院名稱:國立中正大學
系所名稱:化學工程研究所
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:1995
畢業學年度:83
語文別:中文
論文頁數:86
中文關鍵詞:觸媒醋酸鈀
相關次數:
  • 被引用被引用:2
  • 點閱點閱:154
  • 評分評分:系統版面圖檔系統版面圖檔系統版面圖檔系統版面圖檔系統版面圖檔
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0

白金載體觸媒可以藉著加入第二種金屬,如鈷(Co)、鉬(MO)、鎳(Ni)、錸(Re)、銀(Ag)及鈀(Pd)等予以改質。我們首先利用加速老化試驗(accelerated aging test)來測試所添加之第二金屬在觸媒對硫容忍性之效應,此試驗為含l000ppm硫之四氫化奈(tetralin)在溫度280℃,壓力380psig,及氫油比(mole)=2.7之條件下進行加氫飽和反應,其結果顯示鈀-白金觸媒具有最好之耐硫性。白金載體觸媒及鈀-白金觸媒更進一步以直餾柴油(Straight run distillate diese1)為進料進行芳香煙減量(aromatic reduction)、加氫脫硫(hydrodesulfurization,HDS)及加氫脫氮(hydrodentrogenation,HDN)的長期穩定性試驗,其操作條件與商業上柴油之加氫處理程序相同。試驗結果再一次指出,鈀-白金觸媒具有較佳之催化能力。這些結果與利用FFT-IR光譜儀測定金屬群(metalclusters)在觸媒上之電子性質相結合,提供我們推論鈀在增強耐硫性上所扮演的角色,即鈀-白金因雙金屬間的交互作用,降低白金金屬之電子密度,抑制硫化氫對白金金屬的吸附。
利用快速傅利葉轉換紅外線光譜測定Pt-Pd/γ-Al2O3雙金屬觸媒之CO吸附,發現金屬群之電子性質,雙金屬間之交互作用及白金之電子密度,受所使用鈀先驅物的不同及觸媒製備之前處理條件所影響。使用醋酸鈀(palladium acetate)所製備之Pt-Pd燭媒未經鍛燒直接還原者,有明顯之雙金屬交互作用,此交互作用可由觸媒之CO吸附紅外線光譜中,白金金屬群之吸附波峰往高頻率方向偏移,而鈀之CO吸附波峰往低頻率方向偏移,以及Pt-Pd(OAc)2/γ-Al2O3之併催化還原效應得到證實。相反地,對於製備自醋酸鈀及銨鹽鈀且經過450℃鍛燒之Pt-Pd觸媒,則沒有明顯之雙金屬交互作用。為了了解Pt-Pd雙金屬間交互作用對觸媒在商業工場模式操作下之選擇性及穩定性之影響,我們利用直餾柴油在340℃、580psig及氫油比=2.5進行加氫處理試驗,結果顯示不論在芳香煙減量,加氫脫硫及加氫脫氮的選擇性上,都隨著Pt-Pd雙金屬的交互作用而增加。
添加硼酸於Pt/γ-Al2O3可以增加觸媒之酸性,我們首先利用含l000PPm硫之四氫化奈當進料,在溫度280℃、壓力460psig、氫油比=3.85的條件下進行加氫飽和反應,發現硼酸化之鉑/氧化鋁(Pt/γ-Al2O3(B))觸媒比鉑二氧化鋁(pt/γ-Al2O3)觸媒具有較佳之耐硫性。復以柴油當進料,其反應條件與商業上柴油之加氫處理程序相同,試驗結果並未如四氫化奈之飽和反應有明顯之差異,即Pt/γ-Al2O3(B)之耐硫性比Pt/γ-Al2O3僅有些微提高。利用紅外線光譜特性分析檢測兩種觸媒之一氧化碳吸附,發現Ptr-Al2O3(B)之吸附波峰並無偏移(shit)現象,說明硼酸對鉑觸媒之影響並無電子效應存在,因此推測硼酸僅是扮演增加擔體酸性基之角色。為了證明所作的推測,我們以含1000ppm硫及100ppm氮之四氫化奈當進料,於相同條件下進行反應,其結果與柴油進料類似,Pt/γ-Al2O3(B)之耐硫性並沒有明顯之提高。顯然,所添加之有機氮化合物減弱擔體表面之酸性基,而降低其催化活性。


Supported Pt catalysts were modified by adding second metal such as Co,Mo,Ni,Re,Ag, and Pd. The effects of second metal on the sulfur resistance were first investigated by accelerated aging test reactions. The test reactions were hydrogenation oftetralin containing 1000ppm sulfur at 280℃,380psig, and H2/Oil(mole)=2.7. The results indicated that Pd-Pt catalyst had the highest sulfur resistance. Aromatics reduction, hydrodesulfurization, and hydrodenitrogenation of straight run distillate diesel over supported Pt and Pd-Pt catalysts were further examined by long term stability tests. The operation conditions of these tests are the same as those run at commerical diesel hydrotreating process. The results again indicated that the Pd-Pt catalyst exhibited much better catalytic performance. These results, together with electronic properties of the metal clusters on the catalysts characterized by FFT-IR spectroscopy provides a basis to speculate the role of Pd in enhancing sulfur resistance that the Pd-Pt bimetallic interactions decrease the electron density of Pt thereby inhibit the adsorption of H2S.
Fast Fourier transform infrared (FFT-IR) spectroscopy was used to characterize the electronic properties of the metal clusters on γ-Al2O3 supported Pt-Pd catalysts. The Pt-Pd bimetallic interactions,and the resulting electron density decrease of Pt,are influenced by Pd precursors and pretreatment condictions of the catalyst preparation. The Pt-Pd catalyst made from palladium acetate without calcination pretreatmant was characterized by significant Pt-Pd bimetallic interactions. This is evidenced by a shift in the infrared absorption peak characteristic of terminal CO ligand adsorbed on the Pt clusters of the reduced catalyst to higher frequency, bridging CO on the Pd to lower frequency, and a catalytic reduction of palladium acetate by Pt.ln contrast,no significant bimetallic interactions were observed for the catalyst made from palladium acetate with a calcination at 450℃ in air and the catalyst made from palladium amine. To understand the effects of Pt-Pd bimetallic interaction on catalyst selectivity and stability in commercial plant running mode, the catalysts were examined in a long term stability test. They are tested for hydrotreating of straight run distillate diesel at 340℃, 580psig. and H2/Oil(mole)=2.5 over a 25-day period. The results indicated that reduction of aromatics, hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) selectivity of the catalysts are increased by the Pt-Pd bimetallic interactions.
Acidity of γ-Al2O3-suppported-Pt catalysts were modified by addition of boric acid to the catalysts. The effect of the boric-acid-addition, on the catalytic performance were first examined by the hydrogenation of tetralin containmg 1000ppm sulfur at 280℃, 460psig, WHSV=3.85h(-1)and H2/Oil(mole)=4.8. The results showed that the sulfur resistance of the modified catalysts were greatly improved. However, stabihty test of the catalysts using straight-run-diesel feed indicated that the difference of stability maintance between Pt/γ-Al2O3(B) and Pt/γ-Al2O3 was insignificant. Furthermore, the catalysts characterized by FFT-IR spectroscopy suggested that the electronic properties of Pt clusters on the Pt/γ-Al2O3(B) catalyst were not varied by the modification. The role of boric acid in improving sulfur resistance of Pt catalysts was infered to be caused by the increased acidity of the support; base nitrogen contained feed will thus kill acid sites thereby lessen the boric-acid-addition effects. The inference was proved by examined the stability of the catalysts with tetralin feed containing 1000ppm sulfur and 100ppm base nitrogen; no significant stabihty maintance was observed for the boric-acid modified catalysts.

QRCODE
 
 
 
 
 
                                                                                                                                                                                                                                                                                                                                                                                                               
第一頁 上一頁 下一頁 最後一頁 top
系統版面圖檔 系統版面圖檔