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Ammoxidation of Substituted Methyl Aromatics on Vanadium-containing Catalysts

Author: LuZuoFeng
Tutor: ChenYinFei
School: Zhejiang University of Technology
Course: Industrial Catalysis
Keywords: Ammonia oxidation catalyst Aromatic hydrocarbons VPO catalyst Ammoxidation Catalyst structure Methyl Selective Benzonitrile Chlorotoluene V catalyst
CLC: O643.3
Type: Master's thesis
Year: 2002
Downloads: 94
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Abstract


Methyl aromatic ammoxidation the synthetic aromatic nitrile process must Problems to be solved is the catalyst. V / Ti, V / Mo, V / Sb and V / Sn and other catalysts are more common in this field. VPO catalyst is generally used in the C 4 straight chain alkane oxidation reaction. After the study found the the VPO catalysts same outstanding catalytic properties in methyl aromatic hydrocarbons, ammonia oxidation reaction. After the experimental research and studies to obtain a preferred the VPO catalyst preparation method, the resulting catalyst has a considerable mechanical strength, high specific surface area and a longer life. VPO catalyst in toluene ammoxidation reaction, obtained the toluene molar yield of 440 ° C under 94%, between 1 to 2 and the catalyst P / V catalysts have good activity and selectivity for nitrile, benzonitrile The molar yield of between 94 to 78% variation. P / V ratio the higher the better, the reaction selectivity for nitrile. Conditions of this reaction to explore, get the best reaction conditions: T = 400 to 440 ° C, toluene: NH 3 : Air = 1:10:30, toluene feed airspeed 30-40h -1 . The catalyst applied to the remaining methyl aromatic hydrocarbon ammoxidation, such as 3 - methyl-pyridine, p-chloro toluene and xylene. Found that the same VPO catalyst in a better conversion rate nitrile selectivity and smoke in the the 420 ℃ smoke nitrile molar yield 87.5% 3 - methylpyridine. Chlorotoluene due substituents, 400 ° C reaction the chlorobenzonitrile molar yield could only reach 63%. Found in the ammoxidation reaction of p-xylene, a high P / V catalyst at low temperatures, good selectivity single nitrile, double nitrile selective low, but elevated temperatures, good obviously double nitrile selectively variable. Low P / V catalyst ratio is generally only generate the bis-nitrile. At 400 ° C and catalyst P / V = ??1.2 conditions only on the the two benzonitrile highest molar yield of 35%. XRD, IR and TPR characterization of the P / V catalyst structure and surface properties. But also on the carrier and carrier-VPO catalyst were characterized. Find P destruction V 2 O 5 single crystal structure, the P / V for 1.0 hours, due to the polycrystalline phase, and the catalyst P of the dominant crystal phase species aggregate, its obvious characteristic peaks in the XRD diagram amorphous the species V X the O Y and V 3 increased catalyst structure presents amorphous. The catalyst due to the increase in P, vanadium oxide gathered VOV keys disappear, V = bond is strengthened, the catalyst activity increased significantly. The silica gel carrier of high specific surface area the same role the VOV key parallel to the surface of the catalyst weakened enhance the vertical at the surface of the catalyst V = O group. Catalytic performance results and characterization results, the VPO catalyst activity center were discussed. The proposed three-center hypothesis (1) inner layer of V = O reactive oxygen species and P-OH of B acid sites form a composite active center, the redox cycle. (2) α-(NH 4 ) 2 [(VO) 3 (P 2 O 7 ) 2 ] is optional center. (3) amorphous substance V X O Y , the catalyst for the oxygen transmission center. Toluene ammonia oxidation reaction mechanism was discussed that toluene first to oxidation generate benzaldehyde intermediates, and then under the action of ligand NH 4 aniline, after The role of lattice oxygen dehydrogenation benzonitrile.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic
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