Optimal Policies of Operation of a Fixed-Bed Reactor for Oxidation of o-Xylene into Phthalic Anhydride

Abstract

Using the methods of mathematical simulation, the opportunities for application of a dual salt bath and a dual catalyst bed to the conventional and low air ratio processes of oxidation of o-xylene into phthalic anhydride are studied. It is established that both systems lead to a significant increase of the yield of the raw phthalic anhydride, as well as to a drastic reduction of the undesired side product phthalide. The optimal characteristics of a dual salt bath and a dual catalyst bed are determined. Experimental temperature profiles obtained in an industrial reactor for oxidation of o-xylene during all the time of catalyst use are studied. Both the nature of variation of the catalyst activity along the bed and its influence on the effectiveness of the process are defined.

A catalyst deposited over the external surface of the reactor tubes—A new solution for carrying out heterogeneous catalytic processes

“…According to our investigations (Anastasov and Nikolov, 1998, 1999a, 1999b, the same is valid for the application of a dual salt bath and a dual catalyst bed. Except for a dual salt bath and a dual catalyst bed, a general disadvantage of the opportunities mentioned is their difficult technical realization.…”

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

“…According to our industrial and pilot investigations Anastasov, 1992a, 1992b;Anastasov and Nikolov, 1998), the kinetic dependencies discussed, together with the kinetic parameters suggested (Calderbank et al, 1977), describe quite satisfactorily the oxidation process carried out by the low-productivity catalyst O 4-25. This catalyst too is a vanadia-titania one, but it operates with inlet reagent concentration of up to 40 g/m 3 (STP).…”

“…In this investigation, as well as in all our more important studies concerning the simulation of the oxidation process (Anastasov, 2003a(Anastasov, , 2003bAnastasov, 1992a, 1992b;Anastasov et al, 1988;Anastasov and Nikolov, 1998;Anastasov, 2002), we use the kinetics proposed by Calderbank et al (1977). A doubtless and very important merit of this kinetics is the reporting of phthalide, whose content determines the quality of the final product.…”

“…The kinetic model and scheme remain unchanged (Anastasov, 2003 b (STP)), the industrial fixed bed is usually composed of two forms of different activities. In order to improve the process effectiveness (Anastasov and Nikolov, 1998), the lower activity form is loaded in the front part of the bed, while in its rear, where the reagent is practically exhausted and the temperature is low, the more active sample is placed. A similar organization of the fixed bed is also observed for O 4-28 catalyst.…”

“…A similar organization of the fixed bed is also observed for O 4-28 catalyst. In this case, the first 160 cm of the bed contain a sample of an activity assumed as one relative unit, while the remaining 120 cm are composed of a catalyst that is 1.35 times as active (Anastasov and Nikolov, 1998). Brazilian Journal of Chemical Engineering Vol.…”