摘要
對異丙基甲苯(p-Cymene)在工業上具有重要的用途，它可以用來生產殺菌劑、殺蟲劑、香料等物質。製得對異丙基甲苯的方法之一是經由甲苯與丙烯在以經CLD(Chemical Liquid Deposition)方法修飾過的沸石上之烷化反應。為了在工業界使用，通常會將粉末(Powder)觸媒加入黏著劑(Binder)使其變成具有一定硬度之顆粒(Pellet)觸媒，以避免在連續式操作時觸媒被帶出反應器及減少壓力降。而這些黏著劑通常具有酸性點，此酸性點會造成丙烯之裂解及產生異構化反應。為了減少丙烯裂解的情況及避免異構化反應的產生，本研究以利用CLD方法修飾過的不含黏著劑之ZSM-5觸媒顆粒做為催化甲苯與丙烯之烷化反應，並且使用超臨界二氧化碳當作載體，藉由超臨界二氧化碳優於氣體的溶解力與優於液體的輸送性質，能有效地溶解焦炭的前趨物，迅速將其帶走，以延長觸媒的壽命；且因其為均一相，可降低質傳阻力，使整體反應速率提高。實驗結果顯示當操作條件為修飾劑TEOS量為1.6 (ml of TEOS)/(g of catalyst)、壓力為1700 psi、溫度為250 ℃、甲苯/丙烯莫耳比為7.65、甲苯WHSV為4.56 (g of toluene/h)/(g of toluene)時，可得到最高的p-Cymene產率(約58 ％)及p-Cymene選擇率(約98 ％)和最少的丙烯裂解(約13 ％)。
為了再有效地降低丙烯裂解的情況，本計畫同時亦利用以矽沸石(Silicalite)包覆經硫酸化(Sulfated)過的氧化鋯(S-ZrO2)所形成之核殼結構做為觸媒，於超臨界二氧化碳中進行甲苯及丙烯之烷化反應以生成對異丙基甲苯。當硫酸化劑為每克ZrO2加入1.5 ml 1 N之硫酸時，可得更高的Cymene產率(約69 ％)和更少的丙烯裂解(約11 ％)，以達到了減少丙烯裂解的情況，而p-Cymene選擇率約為32 ％。當以奈米及次微米矽沸石包覆S-ZrO2觸媒時，但不論使用何種比例的奈米矽沸石皆無法提升p-Cymene選擇率。雖然使用次微米矽沸石時可將p-Cymene選擇率從32 ％略微提升至45 ％，但距以CLD方法修飾過之ZSM-5觸媒還有一段距離(p-Cymene選擇率約98 ％)。原因可能是外表層之矽沸石無法形成一完美連續的薄膜，故有Pinhole的存在，使得三種Cymene異構物均會從Pinhole流出而無法達到分子篩的作用。因此仍需對矽沸石之包覆方法加以探討及改進以提升p-Cymeme的選擇率。

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