Study Of Ammoxidation Of P-Cresolon Highly-Dispersed Mo-Ni-P-O/SiO₂ Catalyst

A lot of methods of preparing p- hydroxybenzonitrile not only have too many steps but also pollute the environment. The preparation of catalyst for p-hydroxybenzonitrile ammoxidation from SiO2 and mainly component of Mo-Ni-P was studied as well as mechanism of activation adsorption of NH3 on the catalyst surface.It is the target reaction that to prepare p-hydroxybenzonitrile by gas phase ammoxidation ofp-cresol. During studying, the reaction device, the control system and the analysis system of the materials were developed. The method of isolation and the method of the qualitative& quantitative analysis of the reaction products were also studied. And the spectrum of FT-IR, 1H NMR of p-hydroxybenzonitrile were provided.Ammoxidation of p-cresol to p-hydroxybenzonitrile (p-HBN) was studied over a large number of different catalysts. The results showed that (1) Supporters of catalyst had effect catalytic activity markedly and SiO2 is the optimal carrier. (2) The silica supported Mo-Ni-PD n(Mo):n(Ni):n(P)=l. 19:2.10:1.20 oxide catalysts can increase the conversion of p-hydroxybenzonitrile, while the selectivity is still preferable. (3) Different kind of the third components has different influences to the catalysts' activity. The catalyst contained of molybdenum, phosphor and nickel was selected.The effects of temperature, distribution of porous of catalyst, support and space velocity of the feed gas on catalytic activity were detected. The results showed that the optimal reaction temperature is 385C, n(p-cresol):n (NH3) n (air) = 1:5.25:31.5 D the weight yield of p- hydroxybenzonitrile is 61%. And the influences of these variables were more discussed.The catalysts were characterized by means of FT-IR.BET analysis of specificsurface and pore structure, XRD and XPS. The results showed that(l) The activity of the catalysts is associated with their specific surface area and pore volume. (2) The species of the active component is MoPO4. (3) The active components run off from the catalysts during the reaction. (4) The chemical bonds of supporter were influenced byactive components. (5) Carbon build-up is the prime reason to decrease activity.The mechanism suggested for p-cresol ammoxidation on Mo-Ni-P-O catalysts, a first step oxygen addition to an activated adsorbed p-cresol, and 4-Hydroxy-benzaldehyde like intermediate is obtained, it turn to/7-hydroxybenzonitrile under the attack by adsorbed ammonium ions NH2 or H2N-.