Study On Catalysts And Reaction Process For Isobutyl Benzene Acylation

Aromatic ketones,significant fine chemical products,are widely used in medicine,spices,dyes,and pesticides,etc.Friedel-Crafts?F-C?acylation reaction is one of the most effective ways in the synthesis of aromatic ketones.Traditional route for the synthesis of 4-isobutyl acetophenone?IBAP?by isobutyl benzene acylation reaction was catalyzed via AlCl₃,which is cheap and efficient.However,this method employs a large amount of AlCl₃?close to the stoichiometric ratio?and produces a large amount of untreatable salt-containing wastewater.In order to realize the recycling of AlCl₃,heterogeneous catalyst AlCl₃/?-Al₂O₃ was synthesized via immobilizing AlCl₃ on?-Al₂O₃.Under the optimal reaction conditions?reaction temperature=0-10?C,n?isobutyl benzene?:n?AlCl₃/?-Al₂O₃?=1:1.2,and reaction time=3 h?,AlCl₃/?-Al₂O₃ catalyst exhibited good catalytic performance in the isobutyl benzene acylation reaction with 98%of IBAP yield,and AlCl₃/?-Al₂O₃catalyst could be reused 2 cycles without distinct reduction of IBAP yield?>80%?.To further improve the stability of AlCl₃-based catalysts,[Bmim]X-AlCl₃?X=Cl,Br?ionic liquids were prepared,and the structure of[Bmim]X-AlCl₃ were characterized by IR and ¹H NMR,etc.In the isobutyl benzene acylation reaction,[Bmim]Cl-AlCl₃ showed better catalytic performance than that of[Bmim]Br-AlCl₃.Under the optimal reaction conditions?n?[Bmim]Cl?:n?AlCl₃?=1:2,reaction temperature=70?C,reaction time=6 h,and n?isobutyl benzene?:n?acetyl chloride?=1:1.1?,isobutyl benzene conversion was 93.6%and IBAP yield was 82.2%.In addition,[Bmim]Cl-AlCl₃ could be recycled 3 times with IBAP yield>72.9%.Aluminum-based catalysts exhibited excellent catalytic performance in isobutyl benzene reaction with the disadvantages of sacrificial catalysts.Therefore,a series of SO₄^2--based solid superacid catalysts SO₄^2-/Fe₂O_3,SO₄^2-/ZrO₂,and SO₄^2-/TiO₂ were synthesized using hydrothermal synthesis-impregnation method,and characteristic properties of SO₄^2-/Fe₂O₃/ZrO₂/TiO₂ were characterized via XRD,SEM,NH₃-TPD,N₂ adsorption and desorption,XPS,FT-IR,and Py-IR.The characterization results indicated that Lewis acid sites existed in SO₄^2-/Fe₂O₃/ZrO₂/TiO₂ catalysts,and the order of acidity was SO₄^2-/ZrO₂>SO₄^2-/Fe₂O₃>SO₄^2-/TiO₂.Furthermore,specific surface areas and thermal stability of SO₄^2-/Fe₂O₃/ZrO₂/TiO₂ were better than these of Fe₂O₃/ZrO₂/TiO₂.In isobutyl benzene acylation reaction,SO₄^2-/Fe₂O₃ exhibited equivalent catalytic activity to SO₄^2-/ZrO₂.Based on the low price of Fe-based catalysts,the effect of raw material ratio,reaction temperature,reaction time,and SO₄^2-/Fe₂O₃ amount on isobutyl benzene acylation reaction were investigated with SO₄^2-/Fe₂O₃ as catalyst.Under the optimal reaction conditions(reaction time=4 h,reaction temperature=70°C,m(SO₄^2-/Fe₂O₃)=2.5 wt%m?isobutyl benzene?,n?acetyl chloride?:n?isobutyl benzene?=1.04:1),isobutyl benzene conversion was68.3%and IBAP yield was 55.3%.SO₄^2-/Fe₂O₃ catalyst could be recycled 5 runs with isobutyl benzene conversion>52.5%and IBAP yield>41.6%.Composite solid superacid catalysts SO₄^2-/ZrO₂-Fe₂O₃ and SO₄^2-/ZrO₂-TiO₂ were prepared by hydrothermal synthesis-impregnation method to increase the stability and acidity of SO₄^2-/Fe₂O₃/ZrO₂/TiO₂.TG and NH₃-TPD analyses showed that the stability and acidity of SO₄^2-/ZrO₂-Fe₂O₃ and SO₄^2-/ZrO₂-TiO₂ were stronger than these of SO₄^2-/Fe₂O_3,SO₄^2-/ZrO₂ and SO₄^2-/TiO₂ catalysts.Besides,SO₄^2-/ZrO₂-Fe₂O₃exhibited excellent catalytic activity in isobutyl benzene acylation reaction with79.1%of isobutyl benzene conversion and 65.2%of IBAP yield,and SO₄^2-/ZrO₂-Fe₂O₃ could be reused 5 times without distinct reduction of catalytic activity?isobutyl benzene conversion>66.7%and IBAP yield>52%?.