The Preparation Of Modified Bentonite Catalysts And The Catalytic Organic Reactions

Modified bentonite is a kind of good environmental friendly catalyst, which plays animportant role in organic catalysis, and are widely applied in modern organic synthesis. Thereare many advantages, such as simple preparation process, low pollution level, low price, highcatalytic activity and good selectivity, easy separation from reaction system, and repeated use,for the use of modified bentonite catalysts. This paper describes the preparation andcharacterization of new modified bentonite catalysts, e.g. inorganic acid modified bentonitecatalysts, Lewis acid loaded bentonite catalysts and KF loaded bentonite catalysts. The catalyticactivities of these catalysts are evaluated through the different organic reactions.1. The preparation and characterization of modified bentonite catalystsFirst the raw bentonite were purified, acidized and sodium treated, and acidic treatmentconditions were optimized. Then, the well-purified active bentonite were chosen for furtherloading of active components, and inorganic acid （HNO₃, HCl, H₂SO₄） modified bentonitecatalysts, Lewis acid （ZnCl₂, CuCl₂） loaded bentonite catalysts and KF-loaded bentonitecatalysts were prepared. The internal structure, specific surface area and acid center etc. of thesecatalysts were characterized by FT-IR, XRD, BET, NH3-TPD. The results show that there is nodamage of bentonite layer-shape structure in the inorganic acid-modified bentonite catalystsobtained in a range of appropriate concentration of acid change, the bentonite pore structuresbecome loose, the specific surface areas increase, the surface acidity is enhanced. In the Lewisacid-loaded bentonite catalysts, the Lewis acids are bonded to bentonite with surface hydroxylgroups, forming new active catalytic centers. In the KF-loaded bentonite catalyst, the specificsurface areas decrease, the layer distances reduce with the increasing of roasting temperature.2. The evaluation of catalytic activities of the modified bentonite catalystsThe HCl-modified bentonite catalysts （HCl/bentonite） were used for catalyzing thepreparation reaction of N-cyclohexyl-p-toluenesulfonamide from cyclohexene andtoluenesulfonamide, and the reaction conditions including the amount of catalyst, reaction timeand other effect factors were explored. The results show that the HCl-modified bentonite catalyst,obtained by the treatment of2mol/L hydrochloric acid, has the best catalytic activity. The yieldof N-cyclohexyl p-toluenesulfonamide is as high as83.7%in toluene solvent at atmosphericpressure.Lewis acid-loaded bentonite catalysts show good catalytic performance in alkylationreaction of active methylene. In the Lewis acid-loaded bentonite catalyzed reaction of diethylmalonate and diphenyl methanol, the yield of diethyl2-（diphenyl）methylmalonate reached more than85%.Using the alkylation reaction of bromobutane and ethyl acetoacetate as a probe, thepreparation conditions of KF/bentonite catalysts were optimized. The preparation condition forKF/bentonite catalysts is KF/bentonite=1:5, and the roasting temperature400C. The catalyticreaction of bromobutane and ethyl acetoacetate was also studied, and the results indicate that, inthe condition of ethyl allylacetoacetate: bromobutane=1:2, the reaction temperature85C, andthe reaction time4h, KF/bentonite catalyst0.4g, the yield of ethyl2-n-butylacetoacetate reached38.6%.