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研究了异丙醇,2-丁醇和1-苯乙醇在铜铬氧化物上的催化脱氢反应。实验得到的异丙醇,2-丁醇和1-苯乙醇脱氢的活化能分别为21.0,20.9和16.9千卡/克分子。脱氢速率的顺序为2-丁醇≈异丙醇>1-苯乙醇。与伯醇相比,两种直链仲醇的脱氢活化能比伯醇低7千卡/克分子左右。仲醇的脱氢速率比伯醇快。六种直链烷醇在铜铬氧化物上的脱氢速率常数(k),与醇分子中α碳上取代基的Taft极性取代基常数(σ~*)和空间取代基常数(E_s)密切有关。符合方程式: log (κ/κ_0)=ρ[(σ~*-σ_0~*)+(E_s-E_(s0)]在625K时,式中ρ=-0.7。由此可以认为,醇在铜铬氧化物上脱氢时,表面中间化合物的形成是反应速度的控制阶段。乙醇(或异丙醇)在铜铬氧化物上催化脱氢,在200～400℃之间发现有两个脱氢活性区。低温活性区(280℃左右)有较好的活性和选择性。高温活性区(330℃以上)有相当量的脱水副反应。乙醇在两个活性区中有不向的脱氢活化能。两个活性区的出现可能是由于催化剂存在两种脱氢活性相。把它与在氧化铜上的催化脱氢进行比较,发现低温活性区的活性相可能与有载体的金属铜有关。高温活性区的活性相尚难断定。
The catalytic dehydrogenation of isopropanol, 2-butanol and 1-phenylethanol over copper-chromium oxide was investigated. The activation energies of dehydrogenation of isopropanol, 2-butanol and 1-phenylethanol were 21.0, 20.9 and 16.9 kcal / mol, respectively. The dehydrogenation rates are in the order of 2-butanol ≈ isopropanol> 1-phenylethanol. Compared with primary alcohols, the dehydrogenation activation energy of the two linear secondary alcohols is about 7 kcal / mol lower than that of primary alcohols. The secondary alcohol dehydrogenation rate faster than the primary alcohol. The dehydrogenation rate constants (k) of six linear alkanols on copper-chromium oxide and the Taft polar substituent constants (σ ~ *) and the space substituent constants (E_s) of the substituents on the α-carbon in the alcohol molecule Closely related. The equation is: ρ = -0.7 at 625K, log (κ / κ_0) = ρ [(σ ~ * -σ_0 ~ *) + (E_s-E_ (s0) The formation of intermediate compounds on the surface during the dehydrogenation of the oxide is the control stage of the reaction rate.Ethanol (or isopropanol) is catalytically dehydrogenated on the copper-chromium oxide and two dehydrogenation activities are found between 200 and 400 ° C Area.High temperature active zone (about 280 ℃) has good activity and selectivity.High temperature active zone (above 330 ℃) has a considerable amount of dehydration side reactions.Ethanol in the two active regions have not the dehydro activation energy The two active regions may be due to the presence of two dehydrogenation active phases in the catalyst.Comparing it with the catalytic dehydrogenation on copper oxide, it is found that the active phase in the low temperature active region may be related to the copper metal with carrier. The active phase of the active phase is still difficult to determine.