CS198252B2 - Method of producing phthalic acid anhydride - Google Patents

Description

The present invention relates to a process for the production of phthalic anhydride by gas phase oxidation of aromatic hydrocarbons, in particular naphthalene and / or o-xylene. The oxidation is carried out with air or other oxygen-containing gas in the presence of a supported catalyst bed and made on the basis of a mixture of vanadium oxide and antimony trioxide with an addition of sulphate or alkali metal oxides, at a temperature of 300 to 600 ° C.

It is known that in the hydrocarbon oxidation process, the course of the reaction is essentially dependent on the type of catalyst used. The known catalysts most commonly used for the production of phthalic anhydride are systems in which the catalyst masses are supported on a support.

Substances with low specific surface area are used as carriers, for example .alpha.-Al2O4, carborundum, quartz, etc. The catalytic mass consists of vanadium oxide, which is most often mixed with oxides of one or more elements, for example M0O3, tungsten WO3 TiO ₂ , stannous oxide and / or alkali metal sulphates or pyrosulphates.

In addition to the above-mentioned mixtures, which form the major part of the catalytic masses, so-called promoters, such as phosphorus pentoxide P2 ° 5> magnesium oxide MgO, manganese oxide MnO, zirconia ZrO ₂ , silver oxide Ag ₂ O, oxides, sulphates and pyrosulphates of alkali metals, which are added to the mass in small amounts.

A larger number of known and used catalysts consists of several components. For example, a catalyst comprising the following oxides mixed in certain weight ratios is known from Polish Patent No. 66,965: vanadium oxide V2O5, molybdenum oxide MoOj, tungsten oxide WO3, titanium dioxide TiO ₂ , stannic oxide SnO ₂ , potassium oxide K ₂ 0, sodium oxide Na ₂ O, sulfur trioxide SO 2. Catalysts comprising the following oxide systems are also known: vanadium oxide V ₂₀ O, tungsten oxide WO 1, phosphorus ^p 2 O 5> sodium oxide Na ₂ 0j vanadium oxide V _{20 0} , tungsten oxide WO 3,

98252

98252 phosphorus pentoxide PjOj, sodium oxide Na ₂ O, titanium dioxide TiO _2> sides potassium K ₂ SO ₄ ; vanadium oxide V ₂ O ₅ , tungsten oxide W ₃ , phosphorus pentoxide P ₃ O ₃ , sodium oxide Na ₂ 0, manganese oxide MnO, potassium sulfate K 3 SO 4, as well as magnesium oxide MgO and zirconium oxide ZrO ₂ / see German Patent Specification No. 1,250 806), as well as a catalyst which, according to Japanese Patent Specification No. 7,305,739, contains vanadium oxide V ₂ 0 ₅ , titanium dioxide TiO ₂ , potassium oxide K ₂ O and silver oxide Ag ₂ O.

The large number of components in the active mass of the catalysts presents many difficulties in their preparation.

Methods are also known in which naphthalene or o-xylene is oxidized in two stages and a different catalyst is used in each stage. According to one method described in Japanese Patent No. 7,326,749, a catalyst comprising vanadium pentoxide ^at 2 ° C> titanium dioxide TiO ₂ and potassium sulphate is used in the first step and a catalyst comprising vanadium pentoxide V ₂ 0 _5> titanium dioxide TiO ₂ and lithium sulfate Li 2 SO 4. According to DOS No. 2,020,482, in the first stage is vanadium pentoxide V ₂ 0j, titanium oxide TiO ₂ pentoxide PjOj and the second stage vanadium pentoxide V ₂ O _5> titanium dioxide TiO ₂ and sodium sulphate Na ₂ SO _fourth

In the two-step process for the oxidation of hydrocarbons in the presence of the two three component catalysts, while a favorable conversion of naphthalene to phthalic anhydride was achieved, two different catalysts had to be produced, and filling the individual tubes of the process reactor with two catalysts created additional difficulties.

To achieve higher yields of phthalic anhydride catalysts are sometimes treated with sulfur dioxide from gaseous S0 ₂ and this is carried out additionally in the reaction mixture of hydrocarbons, where the sulfur dioxide supplied together with the air. The presence of sulfur dioxide in the reaction system initiates catalysts, as found, for example, in a catalyst comprising vanadium pentoxide V ₂ O _5> potassium sulphate K ₂ SO ₄ and silica gel (Kinetics i Kataliz 1974, 15/1, 127-31) or in a catalyst containing oxygen vanadium V ₂ ° 5 'antimony trioxide Sb ₂ O ₂ , dipotassium double sulphate KjSjO?, barium sulphate Cs ₂ S ₂ O ₂ , titanium dioxide (mass ratio of oxides: 3: 4: / 17 to 27 /: / 66 to 67 /) in which a favorable conversion of o-xylene to phthalic anhydride was achieved (see DOS No. 2 321 799).

Introducing the gaseous sulfur dioxide S0 ₂ in the reaction mixture prepared however complicates the process of oxidation of hydrocarbons.

The aforementioned DOS no. 2,321,799 relates to a process for producing phthalic anhydride by oxidation of o-xylene and naphthalene in the presence of a catalyst which comprises 1-10 parts by weight of carbon vanadiěněho V ₂ 0 ^ 30 to 90 parts by weight of titanium dioxide TiO _2> 0 5 to 20 parts by weight of antimony trioxide Sb.sub.2 and 0.2 to 60 parts by weight of alkali metal pyrosulfates, but without introducing gaseous sulfur dioxide into the reaction system.

The alkali metal pyrosulfate consists of 10 to 100 Z of cesium pyrosulfate and the rest of potassium pyrosulfate.

The proportion of the individual components is based on the total weight of these components making a total of 100 Z. vystupujícíIv catalyst component in the largest quantities - titania Iio ₂ - is described in the patent as a carrier. It všhk well known that the process of oxidation of o-xylene and naphthalene contains a number of catalysts useful herein as components of its active material besides carbon vanadiěněho V ₂ 0j i titania TiO ₂ · Titanium dioxide TiO ₂ plays are therefore role inert component of the catalyst, but is its catalytically active component with a substantial percentage.

According to the aforesaid patent, the oxidation process with the above catalyst achieves an conversion of 72.1 moles of o-xylene. and for naphthalene 79 Z mol. at a catalyst load corresponding to 45 g / l / h and 50 g / l / h.

The known processes for the preparation of phthalic anhydrides by gas-phase oxidation of hydrocarbons in the presence of known catalysts are characterized by generally low conversion of raw materials.

All the measures described above, such as the use of catalysts containing more components (more than 4), pretreatment of the catalysts with SO ₂ gas, carrying out the process in two stages or in the presence of SO _2> have a beneficial effect on the catalyst performance with respect to conversion. but they are associated with many additional technical complications.

It has now been unexpectedly found that the gas phase oxidation of hydrocarbons can be carried out with a large yield of phthalic anhydride and a large conversion of raw materials when using a catalyst containing only a mixture of two active oxides, V2O5 and oxides as catalyst. with the addition of small amounts of alkali metal sulphate promoter, preferably sodium sulphate. This mass is deposited on an inert support with a small specific surface, such as alumina of the modification α, α, OO ^ », carborundum, α-AljO ^ ^+, SiO Sí.

According to the invention, the aromatic hydrocarbons, in particular naphthalene and o-xylene, are oxidized in the presence of a catalyst in which the vanadium oxide V2O5 and the antimony trioxide Sb2Og are deposited on a support with a small surface area in a weight ratio of 100: 5 to 30. It is advantageous to introduce additionally an alkali metal sulphate and / or an alkali metal oxide into the catalyst, the content of the constituents in question being in a weight ratio of ≥ 2 ^ 5 ^{: δ} ^ 2θ3 ^: where Me 3 ^{e and} alkali metal ⁼ 100: / 50 to 30 /: / 0 , 2 to 5). Sodium oxide is preferably used as the alkali metal oxide.

The catalyst used in the process according to the invention is universal in relation to the use of raw materials and can be used for both the oxidation of naphthalene and the oxidation of o-xylene. The active substance contains only two, at most three starting components, with high conversion of naphthalene or o-xylene to phthalic anhydride in a one-stage process, and the use of sulfur dioxide gas as a promoter is not necessary.

The novel catalyst is characterized by a high conversion performance with respect to feedstocks, for example 150 to 300 g of naphthalene or 140 to 180 g of o-xylene per liter of catalyst per hour, while at the same time good yield of phthalic anhydride, 82 to 90 mol% using naphthalene; 65 to 70 mol% with o-xylene.

The process according to the invention will be further illustrated by means of examples.

Example 1- Oxidation of Naphthalene

Catalyst, composed of 10.3 wt. vanadium pentoxide ^ 2 ^ 5 ⁹ »2 wt. % of antimony trioxide Sb20g and 88.5 wt. The carrier (prepared corundum) was poured into a 25 mm diameter stainless steel tubular reactor. The catalyst layer height was 200 cm. A mixture of naphthalene and air vapor (41 g of naphthalene per 1 m @ 2 of air) was passed through a catalyst-filled reactor. The oxidation process was conducted at a catalyst bed temperature of 370-440 ° C. Catalyst load about 180 g / l / h.

Observed conversion by analysis of gaseous reaction products:

to phthalic anhydride ................... 85,7 mol% to maleic anhydride .................. ............................... 6.0 mol% naphthoquinone ............ .................. 2,0 mol% per carbon monoxide and carbon dioxide CO + CO2 ................... ............. 6,3 mol%

Example 2 - Oxidation of Naphthalene

Catalyst, composed of 9.8 wt. vanadium trioxide 2 2θ5 wt. % of antimony trioxide Sb ₂ O ₃ , 0.07 wt.%, sodium sulfate and 88.4 wt. The carrier (prepared electrocorundum) was charged into a tubular reactor as in Example 1. A mixture of naphthalene vapor (41.0 g of naphthalene per 1 m ^J air) was passed through a catalyst-filled tubular reactor at a catalyst bed temperature of 370 to 460 ° C. . Naphthalene catalyst loading was 200 g / l / h, contact time 1 second.

The analysis showed that naphthalene has completely reacted, namely:

to phthalic anhydride .............................................. ...... 89.8 mol% per maleic anhydride ................................... ............... 6.1 7 ₀ mol naphthoquinone ........................... ....... 1> 5 mol% carbon monoxide and carbon dioxide CO + CO2 .............................. 2.6% mol

Example 3- Oxidation of o-xylene

The catalyst having the composition of Example 2 was charged as in Example 1 into a tubular reactor. A mixture of o-xylene vapor (41.5 g o-xylene per 1 m ³ air) was passed through the reactor. The catalyst loading with o-xylene was 160 g / l / h, the catalyst bed temperature was 400 to 466 ° C.

Analysis of the gaseous reaction products indicated that the o-xylene had reacted by:

to phthalic anhydride .............................................. ...... 69,9 Mole per maleic anhydride ...................................... ............... 9,4 mol% per phthalimide ............................ ......................................... 0,2 Z mol per o-toluylaldehyde .................................................. ............ traces of benzoic acid .................................. ......................... traces of carbon monoxide and carbon dioxide CO + θθ £ ............... ........................ 20.1 Z-unreacted o-xylene ................. ........................................... 0,4 Z mol

Example 4- Oxidation of a mixture of naphthalene and o-xylene

The catalyst assembled as in Example 2 was charged as in Example 1 into a tubular reactor. A mixture of hydrocarbon vapors (80 from naphthalene and 20 from o-xylene) was passed through the reactor with 3 chem (41.5 g of hydrocarbon mixture per 1 m of air). The catalyst loading was 165 g / l / h. Catalyst bed temperature 385-462 ° C.

Analysis of the gaseous reaction products showed that the hydrocarbon mixture had reacted by:

to phthalic anhydride .......................... 80.5 Z mol per maleic anhydride ........... ............... 7.8 Z mol per naphtha only ................ 0.2 Z mol per phthalimide .... .... 0,3 mol per o-toluylaldehyde ..................................... ......................... traces of benzoic acid ..................... ...................................... carbon monoxide and carbon dioxide traces CO + CO ^ .. ..................................... 10,7 Z-unreacted o-xylene .... .................................................. ...... 0.5 mol

Example 5- Oxidation of Naphthalene

The catalyst, composed of 10 parts by weight (%) of vanadium pentoxide (VgO 3), 0.6% by weight of antimony trioxide Sb 2 O, 89.4% by weight of the carrier (prepared electrocorundum), was charged into a tubular reactor as in Example 1. Naphthalene / air vapor mixture (40.0 g of naphthalene per 1 m of air) was passed through a tubular reactor filled with catalyst. The oxidation process was conducted at a catalyst bed temperature of 370-440 ° C. The naphthalene catalyst loading was 150 g / l / h.

Analysis of the gaseous products showed that naphthalene had completely reacted, namely:

to phthalic anhydride .............................................. ......

to maleic anhydride .............................................. ....

naphthoquinone ................................................ ..................

for carbon monoxide and carbon dioxide ............................................. ...

79.6 % mo 1 7.2 OF mo 1 0.5 7. mol 12.7 OF mo 1

Example 6- Oxidation of Naphthalene

Catalyst consisting of 9.5 wt. vanadium oxide ^ 2 ^ 5 ´ 2,4 and 88.1% by weight of antimony trioxide. The carrier (prepared electrocorundum) was charged into the tubular reactor as in Example 1. A mixture of naphthalene and air vapor (39.8 g of naphthalene per 1 m 3 of air) was passed through a tubular reactor filled with catalyst.

The oxidation process was conducted at a catalyst bed temperature of 390-440 ° C. The naphthalene catalyst loading was 150 g / l / h.

Analysis of the gaseous reaction products showed that naphthalene had completely reacted, namely:

to phthalic anhydride .............................................. ..... 77.2 Z mol per anhydride / maleic acid ..................................... .............. 10.3 mol% naphthoquinone ............................. .................................... 2,9 mol% for carbon monoxide and carbon dioxide CO + CO2 « .............................. ♦ ...... 9.6 mol.

Claims (2)

SUBJECT OF THE INVENTION A process for the production of phthalic anhydrides by oxidation of naphthalene and / or xylene in the gas phase with air or oxygen-containing gas at a temperature of 300 to 600 ° C, in the presence of a supported catalyst prepared from a mixture of vanadium trioxide and antimony trioxide. characterized in that a catalyst containing vanadium pentoxide, antimony trioxide, as well as a promoter sulfate or an alkali metal oxide, wherein the weight ratio of V2O5: SB20 ^ ^Me 2 ° ^{'K i} * e 3 ^e alkali metal, is from 100: / 5 to 30: (0.2 to 5), preferably 100 ϊ 12: 0.7, and the weight ratio V2O5 of the carrier is 5 to 20: 95 to 80. 2. The method of claim 1, wherein the promoter is sodium sulfate.