Selective oxidation of o-xylene to phthalic anhydride: from conventional catalysts and technologies toward innovative approaches

Abstract

This paper discusses the gas-phase selective oxidation of o-xylene to phthalic anhydride, one of the chemical processes most studied in the 1980s and 90s. Specifically, it is our aim to examine some aspects which may offer ideas for the development of more innovative reactor technologies or catalyst formulations, and to discuss some peculiarities of this process and of the V/Ti/O catalysts that have been overlooked in the past.

The effect of cesium and antimony promoters on the performance of Ti-phosphate-supported vanadium(V) oxide catalysts in selective oxidation of o-xylene to phthalic anhydride

“…Cesium, due to having high strength of base, neutralizes the acid sites significantly: 364 µmol NH 3 /g for the sample with 15 wt% vanadium to 36 µmol NH 3 /g by adding 0.35 wt% of cesium. It was found out which adding antimony independently as a promoter, acidity of catalyst surfaces is increased, while exposure to cesium, acid sites are reduced significantly [3,35]. The results show that when antimony and cesium are utilized simultaneously, acidic sites are significantly reduced by neutralizing the strong and weaker acid sites.…”

“…The selective oxidation of o-xylene under nearly atmospheric pressure, temperature ranges of 300 to 450 °C and the o-xylene concentration in range of 0.5 to 1.8 mol% within a fixed bed tubular reactor is the major process for the production of PA over the world since 1960s [1,4,5]. The vanadia over the anatas phase of titania (V 2 O 5 /TiO 2 ) is the main catalyst for this process [3][4][5].…”

“…Phthalic anhydride (PA) is an important chemical intermediate used in the synthesis of plasticizers for PVC, phthalocyanine dyes, polyester and alkyd resins [1][2][3]. The selective oxidation of o-xylene under nearly atmospheric pressure, temperature ranges of 300 to 450 °C and the o-xylene concentration in range of 0.5 to 1.8 mol% within a fixed bed tubular reactor is the major process for the production of PA over the world since 1960s [1,4,5].…”

Oxidation

“…Phthalic Acid and Derivatives) is commercially produced by the oxidation of o-xylene or naphthalene with air in the gas phase over V-Ti mixed-oxide catalysts, often containing additional metals as promoters (Eq. 88) [227]. Naphthalene, which had lost much of its importance as a feedstock, is now regaining it due to the increased availability of cheap naphthalene from coal, especially in China.…”

4 Engineering technology

“…Details of the catalysts properties and synthesis were discussed recently by Cavani et al (36). Details of the catalysts properties and synthesis were discussed recently by Cavani et al (36).…”