利用噴霧乾燥方法製備矽鋁觸媒

Abstract

噴霧乾燥造粒是一種常用來造粒的方法，透過將一次顆粒分散於溶劑中並加入黏合劑，利用霧化器將液體進料霧化成液滴形式，再以高溫的熱風與液滴進行快速的熱交換使液滴裡的溶劑蒸發並形成固體的二次顆粒，最後使用氣固分離裝置來收集造粒完成後的二次顆粒。 本研究先利用組成FCC觸媒矽溶膠溶液進行噴霧乾燥造粒，並改變不同參數討論對產物的粒徑和形貌的影響。研究發現矽溶膠的液滴粒徑經驗式會在韋伯數數值120以上時，對實驗數據有較好的擬合結果，溶膠凝膠化反應則在熱風進口溫度95℃－96.5℃和pH = 3.3酸性條件下，形成了較大的二氧化矽顆粒。同時也觀察到了在高溫條件下形成的甜甜圈狀顆粒環形區域較薄，表明高溫增強了熱泳現象的作用，在pH = 3.3下，由於矽溶膠的界達電位較低，受到靜電排斥作用的影響較小，液滴中的一次顆粒更容易形成圓球狀。整體而言，在酸性條件下，矽溶膠更容易形成連續的介質形態，適合用於製備FCC觸媒顆粒。在旋風分離器收集率方面利用除溼後的空氣並在切向速度達到13.5 m/s，旋風分離器收集率可達到最大值61.4%。 依據上述結果，本研究認為將FCC觸媒的進料調配於酸性條件有利於造粒後的粒徑尺寸的增長以及圓球的形貌。造粒完後的觸媒顆粒經XRD圖譜分析後仍保有Y型沸石的結晶，BET比表面積為233.7 m2/g，在裂解反應測試時轉化率也達到了90.4%，物理強度則是利用磨耗測試機決定，經5小時的測試後磨耗損失為21.43%。

Spray drying is a commonly used granulation method that involves dispersing primary particles in solvent with the addition of binder. The liquid feed is atomized into droplets using atomizer, and then rapid heat exchange with hot air at high temperatures causes solvent evaporation and the formation of secondary particles. Finally, an air-solid separation device is used to collect the secondary particles.

In this study, spray drying granulation was employed to silica sol solution, and the effects of different parameters on the particle size and morphology of the resulting SiO2 products were investigated. It was found that the empirical equation describing the droplet size exhibited a better fit when the Weber number exceeded 120. The sol gel reaction was observed to form larger silica particles with a hot air inlet temperature of 95°C to 96.5°C and a pH of 3.3. Additionally, it was observed that the ring region of the doughnut shape particles formed at high temperatures was thinner, indicating an enhanced thermophoretic effect. Under pH = 3.3 conditions, the lower zeta potential of silica sol led to less electrostatic repulsion, making it easier for the primary particles in the droplets to form spherical shapes. Overall, under acidic conditions, the silica sol tended to form a continuous intermediate morphology, which is suitable for the preparation of FCC catalyst particles. The yield of the particles in the cyclone separator reached a maximum of 61.4% when using dehumidified air at a tangential velocity of 13.5 m/s.

Based on these results, it was concluded that adjusting the feed of the FCC catalyst under acidic conditions promotes an increase in particle size and the formation of spherical shapes. XRD analysis confirmed the presence of crystalline Y-type zeolite in the as-prepared catalyst particles, with a BET specific surface area of 233.7 m2/g. The catalyst exhibited a conversion of 90.4% in the cracking reaction test. The physical strength was determined by using an attrition tester, and after a 5-hour test, the attrition loss was measured to be 21.43%.