Synthesis And Performance Of Novel Solid Acid-base Catalysts For Styrene From Toluene With Methanol By Side Chain Alkylation

Styrene is an industrially important chemical that is used for production of plastics and rubbers. It is industrially produced by two subsequent reactions: the alkylation of benzene with ethylene to produce ethylbenzene and its dehydrogenation to styrene. There is a potentially interesting alternative route for production of styrene, which involves the direct side-chain alkylation of toluene with methanol.For the side-chain alkylation of toluene with methanol, acid sites catalyze preferentially ring alkylation reactions, but surface acidity is also necessary to catalyze side-chain alkylation via combined acid-base pathways. A base site activates the methyl group of toluene, whereas the acid site interacts with the aromatic ring. Thus, it has been suggested that the side-chain alkylation of toluene with methanol requires a cooperative action of acid/base pairs for efficiently promoting the rate-limiting step in the reaction mechanism?In an attempt to improve activities and selectivities of catalyst for the alkylation of toluene with methanol, novel organic and inorganic solid acid-base catalysts are prepared by using triblock copolymer Pluronic F127 as a template. The catalysts are characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), the acid-base properties of the catalyst were determined by temperature programmed desorption (TPD)using C02 and NH3 as probe molecules, and the side chain alkylation of toluene with methanol over the catalyst has been investigated. The conclusions can be drawn as following:1. According to requirements of catalyst for the alkylation of toluene with methanol, novel organic solid acid-base catalysts are prepared by using triblock copolymer Pluronic F127 as a template. The catalysts are characterized by FTIR,XRD and XPS. Cat-NH(C2H5)2+Al, Cat-TDMMP and Cat-3-HO-Py demonstrate higher than the reference zeolitebased catalysts. It is found the only middle base catalyst can be synthesized from aromatic amine.2. The weak acid-base catalyst is favored to dehydration of methanol to dimethyl ether.3. According to the NH3-TPD-MS of catalysts and catalytic performance, it is concluded that weak (100?200?), middle (200?400?) and strong (400?600?) acid sites are favored to dehydration of methanol, side chain alkylation of toluene and ring alkylation reactions, respectively. Middle acid sites (100?200 ?)catalyze preferentially side chain alkylation of toluene.4. According to the C02-TPD-MS of catalysts and catalytic performance, it is concluded that weak (100?-300?) base site is not sufficient stength to activate the methyl group of toluene, and middle (300?400?) and strong (400?600?)base sites are favored to side chain alkylation of toluene and oxidation of methanol, respectively.5. Considering requirement of adsorption and activation of toluene, model of the distances between acid and base sites is builded, the range of the distance between acid and base sites is about at 3.547±1.000 A. And these results are consistent with experiment.6. Relativity analysis between catalytic performance and character of catalysts showes that significance order is the distances between acid and base sites > Middle base sites(300?400?) > Middle acid sites(200?300?)?7. Five novel inorganic K/Al based catalysts are prepared, Co/Al/K and Co/Sr/Al/K demonstrates the higher conversion of methanol (70.9 % and 90.0%)and styrene selectivity (91.7 % and 82.0 %). And they confirm that the significance order is the distances between acid and base sites > Middle base sites (300?400?) > Middle acid sites (200?300?)?...