Nippon Shokubai Co., Ltd.

Nippon Shokubai Kagaku Kogyo Co., Ltd.

Shinya Tanaka

Masaaki Okuno

Kenji Ueda

Tatsuya Kawabata

Hiroshi Yoshida

Masatoshi Ueoka

Chisako Nishio

Atsushi Ohkubo

The invention relates to a catalyst for producing phthalic anhydride by gas phase catalytic oxidation of o-xylene and/or naphthalene with molecular oxygen or gas containing molecular oxygen and, to a process for producing phthalic anhydride by using said catalyst. The catalyst is made by supporting, on a heat-resistant inorganic carrier, a catalytic active substance which comprises: vanadium oxide; anatase type titanium dioxide having specific surface area of 10 to 60 m.sup.2 /g; niobium; at least one element selected from potassium, cesium, rubidium and thallium; phosphorus; and antimony. The catalytic active substance is prepared by using a five-valent antimony compound as an antimony source. The process for producing phthalic anhydride comprises use of said catalyst.

Catalyst for producing phthalic anhydride and process by using the same

The production of phthalic anhydride by the catalytic vapor-phase oxidation of a mixture of ortho-xylene and naphthalene is accomplished advantageously by a method which comprises packing in a reaction vessel, as a former-stage catalyst, a catalyst produced by supporting on an inactive carrier a catalytic substance composed of vanadium oxide and a specific anatase type titanium dioxide, Nb, P, Sb, and at least one component selected from the group consisting of K, Cs, Rb, and Tl as oxide and, as a latter-stage catalyst, a catalyst similar to the former-stage catalyst excepting the amount of the at least one component selected from among K, Cs, Rb, and Tl is in the range between 17 and 63% by weight as an oxide based on the amount of the same component used in the former-stage catalyst, both in specified bed heights feeding to this reaction vessel the mixture of ortho-xylene and naphthalene and a molecular oxygen-containing gas at a temperature in the range between 300.degree. and 450 .degree. C.

Method for production of phthalic anhydride by vapor-phase oxidation of

The invention presents catalysts for producing phthalic anhydride by vapor phase catalytic oxidation of orthoxylene and/or naphthalene with molecular oxygen or gas containing molecular oxygen. The catalyst is prepared by supporting a catalytic active substance comprising 1 to 20 parts by weight (hereinafter abbreviated 'parts') of vanadium oxide as V.sub.2 O.sub.3, 99 to 80 parts of anatase type titanium dioxide with specific surface area of 10 to 60 m.sup.2 /g as TiO.sub.2 and per 100 parts of the sum of these two ingredients, 0.05 to 1.2 parts of at least one element selected from potassium, cesium, rubidium and thallium as oxide, and 0.05 to 2 parts of silver as Ag.sub.2 O on a heat resistant inorganic carrier. The catalyst may also contain, per 100 parts in total of vanadium oxide and titanium dioxide, 0 to 1 part of niobium as Nb.sub.2 O.sub.5, 0 to 1.2 parts of phosphorus as P.sub.2 O.sub.3, and 0 to 5 parts of antimony as Sb.sub.2 O.sub.3 (however, contents of niobium, phosphorus and antimony will not be zero at the same time).

Catalyst for producing phthalic anhydride

A method of collecting pyromellitic anhydride, which comprises introducing a high-temperature gas containing pyromellitic anhydride together with an inert cooling gas into an empty column-type collecting device whose wall temperature is maintained at 150.degree. to 200.degree. C., effecting heat exchange between the high-temperature gas and the cooling gas in the collecting device to lower the temperature of the high-temperature gas to 150.degree. to 200.degree. C., thereafter passing the gaseous mixture through the collecting device at an average linear gas velocity of 0.05 to 0.5 m/sec with an average residence time to 5 to 60 seconds, and recovering needle-like crystals of pyromellitic anhydride from the bottom of the collecting device.

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Hyogo, Japan

Shinya Tanaka