The assessment of a Novel Nitration of Benzene and Toluene

[[abstract]]芳香族硝化物用途甚廣，是染料、製藥、香水與塑膠等工業產品的主要原料。傳統的硝化程序是為高放熱反應，危險性高，災變層出不窮，而且是在大量的濃硝酸與濃硫酸中進行，會產生大量的廢酸，回收處理困難，亟須以低污染、高安全性的綠色化學反應取代。以沸石CP-814E為觸媒，可以有效的促進芳香族硝化反應的進行，以及增進特定同分異構產物的選擇率，而且沸石CP-814E可以回收再利用，是綠色化學中最具潛勢的觸媒。 本研究的主要目的在於探討以沸石CP-814E為觸媒所催化的苯與甲苯單硝化反應之基本物理化學特性，包含反應熱力學、動力學、相關參數（溫度、攪拌速率、觸媒量）之影響，以及反應失控條件，作為日後進行製程放大及製程安全評估所需的基本數據及依據，以加速其商業化，並可開啟與帶動綠色化學的研究風氣。 在苯與甲苯單硝化反應半批次的製程中，反應物只需要依劑量學上的比例添加，即可完全反應，不會有過量的未反應物須處理。本製程使用濃度百分之九十的濃硝酸與醋酸酐反應合成的硝酸乙醯酯作為硝化劑，與苯、甲苯比率為百分之十與二十的沸石CP-814E作為觸媒，攪拌速率設為每分鐘二百轉的情況下，苯與甲苯的轉化率可以高達百分之九十五以上，苯與甲苯進入硝化反應槽後立即反應，不會有反應物與熱累積的情況發生，而且能增加對-硝基甲苯的選擇率至百分之四十五，也能降低反應的活化能。沸石觸媒CP-814E可以回收再利用，副產物只有醋酸，可以在高溫下再製成醋酸酐，不會產生廢酸與酸性廢水，是對環境較友善的製程，有環境保護上的優勢。 應用反應熱卡計進行測試後歸納發現，在苯單硝化反應中，反應級數為1.2級，反應熱為每莫耳一百一十五點六千焦；在甲苯單硝化反應中，反應級數為1.4級，反應熱為每莫耳一百三十五點六七千焦。不過製程操作安全上須注意，一旦反應槽溫度超過攝氏五十五度，硝化劑硝酸乙醯酯即會爆炸分解，所以反應溫度應控制在攝氏三十度以下，而且冷卻熱移除系統的設計應符合製程的需求。[[abstract]]Nitroaromatic compounds are widely used as the feedstocks for a great many materials, such as pharmaceuticals, dyes, perfumes and plastics. Since the conventional nitration processes that occur in the mixture of concentrated nitric and sulfuric acids are highly dangerous and produce excess waste acids difficult to recover, it is ideal to find alternative processes. Recently a few studies show that acetyl nitrate prepared from a stoichiometric quantity of nitric acid and acetic anhydride was an effective nitration agent and used zeolite CP-814E as a catalyst. This alternative process is definitely worth of further investigation. The purpose of this research program is to study the physical chemical properties, of a such as reaction thermal assessment, kinetics analysis, reaction parameters（temperature, speed of agitate）effect of the zeolite catalyzed nitration of benzene and toluene. The program will provide necessary data for future scale-up and development work, accelerate the commercialization process, and promote the R & D of green chemistry. Benzene and toluene are nitrated in excellent yields （more than 95﹪）with high regioselectivity under mild conductions using zeolite CP-814E as the catalyst and a stoichiometric quantity of nitric acid and acetic anhydride. Nitration of toluene gives a quantitative yield of mononitrotoluenes, of which 45﹪is 4-nitrotoluene. The reaction calorimeter experimental data show that the zeolite CP-814E can reduce the activation energy. In the benzene nitration, the reaction was 1.2 order on benzene and the heart of reaction was 115.6 kj/mole; in the toluene nitration, the reaction was 1.4 order on toluene and the heart of reaction was 135.67 kj/mole. The new process has several advantages. The zeolite CP-814E can be recycled; the products can be separated by vacuum distillation and the only byproduct is acetic acid, which can be used to make acetic anhydride at higher temperature. Since acetyl nitrate will decomposes at 55℃, the reaction temperature has to be controlled below 30℃