Catalysts For Oxidation Of O-xylene Research Articles

Performance of platinum doping on spent alkaline battery-based catalyst for complete oxidation of o-xylene.

Oxidation of o-xylene was performed using alkaline battery-based catalyst doped with platinum to investigate the properties and activities. O-xylene was selected as the model of volatile organic compound (VOC) in this work. Physicochemical properties of the selected catalysts were characterized by FE/TEM (field emission transmission electron microscopy), BET (Brunauer-Emmett-Teller) analysis, XRD (X-ray powder diffraction), SEM/EDX (scanning electron microscopy/energy dispersive X-ray spectroscopy), and H2-TPR (hydrogen temperature programmed reduction). Major elements of the spent alkaline battery-based catalyst treated with sulfuric acid solution [SAB (400) catalyst] were manganese, zinc, iron, oxygen, carbon, chlorine, aluminum, sodium, silicon, and potassium. Increasing the doping amount of platinum on SAB (400) catalyst from 0.1 to 1 wt% increased particle size of platinum and lowered the temperature of TPR (TTP) for SAB (400) catalyst. Better redox properties were achieved with an increase in the o-xylene conversion according to the doping amount of platinum. When GHSV (gas hourly space velocity) was 40,000 h-1, o-xylene was oxidized completely over SAB (400) catalyst and 1.0 wt% Pt/SAB(400) catalyst at temperatures of 400 °C and 280 °C, respectively.

Deactivation properties of a high-productive vanadia-titania catalyst for oxidation of o-xylene to phthalic anhydride

The behavior of a high-productive V2O5-TiO2 (anatase) supported O 4-28 catalyst for oxidation of o-xylene to phthalic anhydride was investigated in the first three years of its exploitation in industry. By using a suitable mathematical model, an identification problem was solved and activation profiles of the catalyst along a fixed bed located in the tubes of an industrial reactor were determined. Experimental temperature regimes and yields of the main and side products for different periods of the catalyst life were used. The proper technological regimes providing for a maximum yield according to the requirements of the catalyst producer company were defined.

The behaviour of a low-productive non-pretreated V2O5–TiO2 (anatase) catalyst for oxidation of o-xylene to phthalic anhydride

The behaviour of a low-productive V2O5–TiO2 (anatase) supported catalyst for oxidation of o-xylene to phthalic anhydride is investigated. The catalyst operates by inlet reagent concentration 40 g m−3(STP) (usual concentration in the industry) and is calcined under conditions, which differ in comparison with those applied in the industry. It is experimentally specified that the amount of the vanadium chemically bonded with the TiO2 support depends considerably on the conditions of calcination. Experiments are carried out in a pilot installation with a fixed catalyst bed composed by a catalyst, which is calcined, but has not undergone other preliminary operations. The dependence of the hot spot temperature on the variation of the process parameters is studied. By means of a heterogeneous two-dimensional model an identification problem is solved. As a result the energies of activation valid for the calcined catalyst are determined. It is found that a calcined but not pretreated sample is considerably more active than the pretreated form. A brief statistic analysis of the experimental and predicted results is performed.

An investigation of the kinetic parameters of the o-xylene oxidation process carried out in a fixed bed of high-productive vanadia–titania catalyst

The behavior of a reactor of a fixed bed composed by high-productive V 2O 5–TiO 2 (anatase) supported catalysts for oxidation of o-xylene into phthalic anhydride is theoretically and experimentally investigated. A two-dimensional heterogeneous mathematical model, as well as experiments obtained in an industrial multitube fixed bed reactor, is used. The kinetic parameters in the kinetic relations suggested by Calderbank et al. (Chem. Eng. Sci. 32 (1977) 1435) for description of the oxidation process are corrected in a proper way. New formal values of the parameters mentioned are determined. They interpret well the temperature regime and the yields of phthalic anhydride and the main side product (phthalide) obtained in the industrial reactor during the initial periods of the catalyst life.

Deactivation of an industrial V 2O 5–TiO 2 catalyst for oxidation of o-xylene into phthalic anhydride

A quantitative description of the observed deactivation in the process of oxidation of o-xylene ( o-XL) into phthalic anhydride (PA) is given in this paper. Experimental temperature profiles along the length of the fixed bed obtained in an industrial reactor during various periods of the catalyst life are studied. With the help of a two-dimensional heterogeneous mathematical model the degree of the catalyst deactivation along the bed is determined as a function of time. The activation profiles obtained interpret very well the magnitude and the location of the hot spot, the PA yield and the content of the main undesired product phthalide (PH). A terraced change of the catalyst activity along the bed is found out, while a maximum decrease of the activity is registered in the hot spot zone. Optimal temperature regimes valid for different periods of the catalyst life are determined.

Possible effects of site isolation in antimony oxide-modified vanadia/titania catalysts for selective oxidation of o-xylene

Titania-supported vanadia catalysts were modified by addition of antimony oxide for application in o-xylene selective oxidation to phthalic anhydride. It was shown that active and selective catalysts can be prepared by ball-milling mixtures of powders of TiO2, V2O5and Sb2O3followed by calcination. X-ray photoelectron spectroscopy proves the formation of highly dispersed overlayers of vanadium oxide and antimony oxide, in which V5+is partially reduced to lower oxidation states and Sb3+is partially oxidized to Sb5+. Antimony oxide segregated into the outermost surface layers. It is therefore inferred that the presence of the antimony oxide modifier spatially separates V–O species and leads to “site isolation” which may be responsible for the positive effect of the modifier for the catalyst's selectivity.