Phthalic anhydride catalyst developments

Transport Properties. Because the feed is primarily air and because substantial amounts of N2 and 02 are present in the effluent stream, we will assume that the fluid viscosity is that of air for purposes of pressure drop calculations. For the temperature range of interest, the fluid viscosity may be taken as equal to 320 micropoise. The pressure range of interest does not extend to levels where variations of viscosity with pressure need be considered. The effective diffusivities of naphthalene and phthalic anhydride in the catalyst pellet may be evaluated using the techniques developed in Section 12.2. 

LAR [Low air ratio] A process for oxidizing o-xylene or naphthalene to phthalic anhydride, using a titania/vanadia catalyst containing molybdenum. Developed by Alusuisse Italia in the 1980s. A plant was operated at Valdamo, Italy, in 1984. 

The oxidation of aromatic hydrocarbons originating from coal is one of the first organic gas phase oxidation processes carried out on an industrial scale. The development of these processes was initiated by the discovery that the V2Os catalyst used for the oxidation of sulphur dioxide was also applicable to the partial oxidation of benzene to maleic anhydride and naphthalene to phthalic anhydride. Remarkably, V2Os-based catalysts are still used in these processes today as they appear superior to any other type of catalyst. 

Oxirane/cyclic acid anhydride alternating copolymers of controlled molecular weight with a narrow molecular weight distribution were found by Aida et al. [188,189] to be formed under mild conditions when copolymerising ethylene oxide and phthalic anhydride in the presence of the (tpp)AlCl-quater-nary phosphonium salt catalyst system. The copolymerisation carried out with (tpp)AlCl alone proceeded very slowly, and the product was not polyethylene terephthalate) but contained ether linkages in considerable amount. The development of the living character and the tendency towards alternation of the copolymerisation when using the aluminium porphyrin catalyst, coupled with a quaternary salt, have been postulated [188,189] to be due to the formation of... 

This method is based on the potassium salts isomerization of phthalic adds. Developed to the industrial stage by Teijin and Kawasaki in Japan, it employs phthalic anhydride or its precursor, o-xylene, as the raw material. If the raw material is phthalic anhydride, the essential step is the potassium salts isomerization of phthalic adds. This reaction, conducted under carbon dioxide pressure at 2.106 Pa absolute and 400°C, in the presence of cadmium salts as catalyst, is followed by exchange reactions of the potassium salts. 

The use of zeolites in the organic chemical industry took a great step forward with their adoption in the isomerization of w-xylene to p- and o-xylenes used in the manufacture of terephthalic acid and phthalic anhydride, respectively. The ZSM-5 catalysts developed by Mobil Corporation became the prime catalysts for this process all over the world. Remember, however, that catalysts are developed specifically to meet certain criteria and to suit a given feedstock specification. We illustrate this through the following example. 

Since that time, sulfur-resistant catalysts have been developed. However, the importance of the fluidized-bed phthalic anhydride process is declining since the proportion of raw material costs is about 70% of total production costs, the feedstocks o-xylene and coal tar naphthalene can be more cost-effectively oxidized in fixed-bed reactors. 

A little more than a decade ago, Clariant decided to venture into the field of partial oxidation reactions. Catalysts for selective partial oxidation reactions thus belong to the most recent developments in the catalyst portfolio of Clariant. The portfolio of oxidation catalysts currently comprises SulfoMax for sulfuric acid production, FAMAX for formaldehyde production, PHTHALIMAX for phthalic anhydride production, SynDane for maleic anhydride production, and most recently VAM ax for vinyl acetate production. 

An example of the general research strategy in the department is the development of PHTHALIMAX , currently the most selective catalyst for phthalic anhydride (PA) production, which will be described in this chapter. In 2003, Clariant decided to start the development of its own PA catalyst. One year later, in 2004, the most iimovafive production technology was developed and installed. Since the first customer at the end of 2004, Clariant could win more than 80 catalyst installations globally. 

Groppi, G., Tronconi, E., Cruzzolin, E, et al. (2012). Conduchve Honeycomb Catalysts Development and Industrial Pilot Tests for the Oxidation of o-Xylene to Phthalic Anhydride, Ind. Eng. Chem. Res, 51, pp. 7590-7596. 

The oxidation of CH3OH to HCHO is considered as a probe reaction for other selective oxidation reactions such as butane to maleic anhydride, o-xylene to phthalic anhydride, and ODH of alkanes to alkenes. Consequently, the concepts developed for the selective oxidation of methanol over vanadium oxide catalysts can be easily transferred to other catalytic reactions. Weckhuysen and Keller [82] carried out methanol oxidation as a probe reaction over various V2O5/S oxides (S = HO2, Zr02, Nb205, Ce02, and AI2O3). The relative independence of turnover frequency (TOP) to vanadia loading on amorphous oxide supports indicated that the reaction was first order with respect to surface vanadium oxide site. 

Multicomponent (P04)jf(V205), catalysts are applied in processes to produce maleic anhydride and phthalic anhydride intermediates for polymers. In the classical industrial process, maleic anhydride is the product from benzene and phthalic anhydride the product from naphthalene. Vanadium oxide-based catalysts have a stronger interaction with their substrates than molybdenum oxide-based catalysts. Whereas on M0O3 catalysts the hydrocarbon skeleton remains intact, oxidation on vanadium oxides proceeds with rupture of carbon-carbon bonds and the total number of carbon atoms in the molecule is not maintained in the reaction products. A new development is the use of butane as a reactant in these processes. 

Complete combustion of organic materials to form carbon dioxide was, of course, well known By 1920 the partial combustion of organic chemicals was being investigated and selective catalysts were gradually developed to control the reactions taking place. Two important processes to produce maleic anhydride and phthalic anhydride from the benzene and naphthalene in coal tar were among the first to be developed commercially. 

Phthalic anhydride, produced in Germany as early as 1916 and in other parts of the world in the 1920s, was nsed initially in the synthesis of indigo dyes. At first naphthalene was oxidized by chromic acid or olenm bnt, by a convenient accident, it was found that mercury catalyzed the oxidation reaction. Later work by BASF in Germany and H. D. Gibbs and C. Condover in the United States developed catalysts for the vapor phase oxidation reaction. 

Titanium dioxide catalysts were first described in the 1940s and 1950s, when mixed oxide catalysts were being investigated and used in a number of oxidation reactions. Mixtures of vanadium pentoxide with titanium dioxide gave better operation and longer life as phthalic anhydride demand increased. An early catalyst that did not sinter and clearly increased the stability of vanadium pentoxide was described in a patent as Ti0(V03)2. At about the same time vanadium pentoxide/phosphorous pentoxide mixtures were also being developed for use in maleic anhydride processes. 

Benzene oxidation using a vanadium pentoxide/pumice catalyst was first studied at the time that the phthalic anhydride process was being developed. Weiss and Downs discovered that maleic anhydride was formed in significant amounts. They concluded that the maleic anhydride was produced via benzoquinone as the intermediate. The yields of maleic anhydride were not high with the unselec-tive vanadium or molybdenum oxide catalysts being tested at that time. 

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