BG62558B1 - Catalyst and method for catalytic scrubbing of waste gases in dmt process - Google Patents

Abstract

The invention relates to a catalyst which is used in the method for scrubbing of waste (exhaust) gases under pressure produced after the oxidation of paraxylene (p-X) with air in liquid phase in the preparation of dimethylterephthalate (DMT). The catalyst contains as components: (a) at least one oxide of titanium, and (b) at least one element of Subgroup VIII of the Periodic system of elements in a metal and/or oxide form. The invention also relates to a method for the preparation of such a catalyst where components (b) are applied on moulded bodies containing at least component (a), either independently or in combination and by submerging and/or by continuous impregnation. The invention also relates to a method for scrubbing the exchaust gases under pressure as wastes after the oxidation of paraxylene (p-X) with air in liquid phase in the production of dimethylterephtalate. The oxygen-containing exhaust gas under pressure from the oxidation gets through one- or multi-stage condensation, one- or multi-stage absorption and subsequent additional burning, optionally with the addition of oxygen catalytically under pressure. The mentioned catalyst is used for the additional catalytic burning. 21 claims

Description

The invention relates to a catalyst intended for carrying out a method for purifying pressurized flue gases, such as being dropped off after oxidation of para-xylene (p-X) with liquid phase air to give dimethyl terephthalate (DMT), to a process for the preparation of such a catalyst and a method for purifying pressurized flue gases as they fall off after oxidation of paraxylene (p-X) with liquid phase air to form dimethyl terephthalate (DMT), such as pressurized and containing oxygen a waste gas from the oxidation is subjected to one-stage or multi-stage catalysis, of a single-stage or multistage absorption and, optionally, by introducing oxygen into the afterburning pressure effected catalytically.

BACKGROUND OF THE INVENTION

The modern atmospheric DMT process is known to contain essentially the following steps:

- oxidation of para-xylene (p-X) and para-methyl ester of toluic acid (pTE), with mandatory exhaust gas treatment included,

- esterification of the reaction products by oxidation with methanol,

- separation of the formed fraction (so-called crude ester / DMT - crude), rich in pTE, which usually returns back into the oxidation step, to one DMT fraction containing a total of more than 85% by weight DMT , and a high-boiling residual fraction, optionally further refining, for example by further incorporation of methanolysis or thermolysis, and subsequent regeneration of the catalyst,

- purification of the crude DMT fraction, for example by washing / washing /, recrystallization and purification distillation, / '' Terephtalcauredinethylester '', Ullmann Bd. 22,4, Avtlage, 3.529533, EP 0 464 046 Bl, and DE-03 40 26 733 /.

The preparation of terephthalic acid of the desired quality by purposive hydrolysis of DMT is also known, that is to say, from fractions, especially rich in DMT, from the corresponding DMT - pure.

The oxidation of a mixture of para-xylyl / Px / and para-methyl ester of toluic acid / p-TE or a p ^m -ester / is carried out substantially with atmospheric oxygen in the presence of a heavy metal catalyst / AE-RE 20 10 137 / at a temperature of at least 140 ° C to 180 ° C and a pressure of at least 4 to 8 bar in the liquid phase. As a result of the oxidation step, a reaction mixture is obtained which preferably contains monomethyl terephthalate MMT (p-toluic acid (p-TA) and terephthalic acid (TA) dissolved or suspended in p-TE, respectively. They are esterified at a temperature of at least 250 ° C to 280 ° C and a pressure of 20 to 25 bar with methanol. Oxidation also produces waste gas, which is subsequently saturated with aliphatic as well as aromatic compounds depending on the pressure and temperature. Thus, the waste gas contains, along with the main products, by-products of the reaction. These include low boiling compounds such as acetaldehyde, formaldehyde and the corresponding methyl acetals, dimethyl ether, acetic acid and formic acid, as well as their methyl esters. Together with these organic constituents, oxidation waste gas contains, in particular, atmospheric nitrogen, residual oxygen residues of 0.5 to 4% by weight, carbon dioxide of 1 to 3% by weight and 0.3 to 2.0 % carbon monoxide by weight. In the atmospheric DMT process, the exhaust gas is typically subjected to subsequent multi-stage cooling. In this case, high- and medium-boiling basic products are gradually separated. The major products remaining in the waste gas, mainly methanol and p-xylene, are subsequently separated from the waste gas by multistage absorption to the extent of traces. In this case, the enriched basic products are back in the process.

In many countries, carbon emissions and carbon monoxide are separated from waste gases by law.

EP 0 544 729 B1 describes a method for purifying oxidation effluent gas obtained from atmospheric oxidation of xylene and standing at a pressure of from 5 to 60 bar. This is followed by separation in a pressure washer of at least xylene by absorption with an ester, for example toluic acid para-methyl ester (pTE) or benzoic acid methyl ester (BME) or a mixture of esters, for example a mixture of p -You and VME. It is also possible to include power condensation before absorption. As a consequence, the oxidizing substances contained in the waste gas after the absorption treatment must be burned under pressure and the waste gas under pressure must be used to generate energy in the turbo generator. Such combustion devices for the combustion of waste gas under pressure are costly and difficult to furnish for enterprises. As a result, these preferred pressurized combustion chambers are no longer found on the market.

EP 0 544 726 B1 discloses the possibility of oxidizing components contained in the waste gas to be catalytically burned under pressure. In this case, the combustible waste gas must be saturated with water vapor.

VDI - Richtlinie 3476, “Katalytische Vertahren der Abgasreinigung”, VDI - Handbuch Reinhaltung der Luft, Band 6 (June 1990), also describes the separation of carbon monoxide, hydrocarbons and ΝΟ _χ from exhaust gas by using Pt / Rh / Pd on ceramic supports at a temperature of 300 ° to 950 ° C. Carriers of catalysts for the purification of flue gases are also used as metals in the form of a molded steel sheet, a fabric, a net, molded metal oxide products, such as A1 ₂ 0 ₃ , SiO ₂ , Ti0 ₂ , ZrO ₂ , MgO, as well as natural and synthetic minerals such as pumice stone, mullite, cordierite, steatite or zeolite. For the separation of carbon monoxide as well as vapors from organic compounds contained in the industrial waste gas, catalysts of noble metals or metal oxide catalysts deposited on ceramic carriers or catalysts with a large active surface are generally used.

EP 0 664 148 A1 discloses a method for the purification of pressurized flue gases by additional catalytic combustion at an operating temperature between 250 ° C and 800 ° C and a pressure between 2 and 20 bar, preferably with the addition of platinum catalysts and / or palladium on γ-alumina. Tests show that these catalysts are deactivated under operating conditions in the waste gases from the oxidation of para-xylene upon receipt of DMT after a short technological time and the necessary reduction of harmful substances can no longer be achieved.

SUMMARY OF THE INVENTION

According to the invention, a catalyst system has been created to meet the stated requirements for the purification of the exhaust gases produced during the production of DMT during oxidation, thus purifying waste gases which may be of use to the DMT process and are of economic importance.

It has been found that a catalyst containing at least one titanium oxide and at least one element of the VIII subgroup of the periodic table of elements as a metal and / or oxide form is particularly suitable for use in a pressurized effluent treatment method which are released by the oxidation of para-xylene (p-X) with liquid phase air to form dimethyl terephthalate (DMT). Minimum deactivation has been established, which preserves the necessary values for the waste gases and shows excellent economic advantages.

According to the invention, a catalyst for carrying out a method of purifying pressurized waste gases as they are separated after oxidation of para-xylene (p-X) with liquid phase air to obtain dimethyl terephthalate (DMT), contains the following components: at least one titanium oxide and at least one element of VIII subgroup of the periodic table of elements in metallic and / or oxidic form.

Preferably the catalyst according to the invention contains the following components in wt%:

- components a / from 50 to 99% by weight

- components b / 0.01 to 5% by weight, wherein the components b / are calculated in quantity and as metal.

Preferably, titanium oxide or a starting compound for components a / are derived from the so-called. sulfate process so that the catalyst according to the invention also contains components with / sulfate of 0.1 to 10 wt.% relative to the amount of catalyst.

The sulfate as a component of the catalyst according to the invention may be such as, for example, in the form of hydrosulfate or oxidesulfate or oxidesulfate (containing water) of the corresponding metal, or applied to the surface of an oxide metal compound or sulfuric acid. Sulphate can be in several of the above forms simultaneously.

In the catalyst according to the invention, the components a) may be, for example, preferably in the form of titanium oxide, for example rutile. Preferably, according to the invention, in the catalyst component a / is preferably in an anatasform. It is also possible for the titanium oxides to be together with a certain content of oxygen or with oxides containing water, hydroxides or sulfate, incl. and hydrosulfate, for example, oxysulfate or oxide sulfate of titanium containing water or titanium oxide with sulfuric acid applied. Also, component b / may be in the catalyst of the invention in a proportional amount as a sulfate form.

In a preferred embodiment, the catalyst according to the invention may further comprise barium sulfate and / or tungsten oxide and / or vanadium oxide and / or zirconium oxide and / or the corresponding sulfates and / or phosphates, incl. and hydrophosphate and / or silica and / or silicates.

The structure of the catalyst according to the invention can be circular, tubular, rectangular, top-shaped and saddle-shaped. The form can also be cellular. The catalysts according to the invention generally have from 200 to 2,000 m ³ / m ³ geometrically active surface, preferably for tubular extrudates having a cross-section of 4 mm. The catalysts of the invention may also have a cellular structure, especially those having a hydraulic cross section (4a / U = dh with a = light cross section, U = range of light cross section and dh = hydraulic cross section), single cross section of conductive cell ducts is in the range of 1.5 mm to 6.5 mm.

According to the invention, there is also provided a process for preparing a catalyst according to claims 1 to 9, wherein the components b / are deposited on molded bodies which contain at least components a), alone or in a mixture. The application may be by immersion or optionally spray impregnation.

A process for the preparation of a molded titanium oxide base, also called a molded article, is described in DE PS 26 58 569. For the preparation of a catalyst according to the invention, in particular molded titanium oxide bodies are obtained preparation and extrusion of molded quantities of titanium oxide material obtained by preforming and extrusion of molded quantities of titanium oxide material and preferably having an active surface of from 10 to 200 m ² / g and a pore volume of 0.1 to 0 , 6 cm ³ / g. Molded bodies can be reinforced with glass fibers, for example, to improve their mechanical performance.

As a rule, the b / c catalyst components of the invention are applied to the carrier by so-called. impregnation, wherein the molded bodies are contacted with a solution containing components b / in the form of a soluble salt. In the process according to the invention, a solution is used to impregnate the molded bodies, for the preparation of which the components b / are preferably added in the form of nitrate. The requirement here may be to adjust the pH of the solution appropriately, for example by adding an organic or inorganic acid, for example nitric acid or a base, or a complexing agent or stabilizer, for example to stabilize the corresponding form of the precious metal used. . The impregnation can be accomplished by spraying the molded bodies with a solution once or repeatedly or by repeatedly immersing the molded bodies in a suitable solution.

The impregnated molded bodies are preferably subjected to additional calcination, preferably by blowing with air within a temperature range from 30 ° C to 650 °, which means thermal additional treatment.

The addition of nitrates is a particularly great advantage of the process of preparation, since the components b / can be fixed to the molded bodies by a simple thermal treatment of the impregnated molded bodies in metallic and / or oxidized form and without more residues, for example halides. Economic and technological measures or, for example, reduction measures related to hydrogen in the gas phase can thus be saved.

Preferably, in the catalyst according to the invention, the components b / for the most part are in the area of the surface of the catalyst molded bodies, which means that according to the invention it is preferable to apply the so-called. bath impregnation / immersion in a bath /. The b) catalyst according to the invention preferably comprises platinum and / or palladium and / or rhodium. Particularly preferred catalysts according to the invention are those having a platinum content of 0.05 to 0.5 wt.%, Especially preferably a platinum content of 0.1 to 0.2 wt.% By weight of the catalyst.

According to the invention, there is also provided a method of purifying pressurized flue gases, such as fumigated after the oxidation of para-xylene (p-X) with liquid phase air to produce dimethyl terephthalate (DMT), thus the flue gases, containing oxygen from the oxidation step and under pressure, are subjected to single or multi-stage condensation, one-stage or multi-stage absorption and subsequent additional combustion, thus catalytic, optionally oxygen and pressurized. The method is characterized in that a catalyst according to claims 1 to 13 is used for the catalytic additional combustion.

In the method of purification of waste gases according to the invention, the waste oxidizing gases themselves obtained by oxidation with air of p-X can be largely separated from the useful products contained in the waste gas - mainly p-X, p-TE, DMT, benzoic acid methyl ester (BME) and methanol - and this separation should be carried out in a condensing device, optionally also in an additional dishwasher, respectively absorption device, and appropriately returned. in the technological process. Condensation is generally carried out at a temperature of 15 ° to 8 ° C and a pressure of 3 to 20 bar.

The post-condensation and pressurized waste gases are suitably heated in a counter-flow heat exchanger, for example from 25 ° C to 120 ° C at a pressure of 3 to 20 bar, and then passed through a dishwasher. The absorption device may consist of more washing steps, for example, a flushing of the waste gas with BME or an ester mixture may follow.

Figure 1 shows a preferred embodiment of the method according to the invention (app. Legend).

Following such an absorption device, it is possible to adequately saturate the waste gas (110) with the waste water already in the process (100), whereby the so-called process water contains mainly organic components. Generally, the so-called saturator / AS /. The process water is preferably circulated through a pump (P1) and a heat exchanger (W1) heated by low pressure steam and fed into the head of the saturator (AS). In general, the waste gas is saturated with water and with substantially unidentified organic components contained in the primary process water. In order to eliminate contamination, filling in the saturator (AS), in which it is obtained after enrichment with solids and high boiling components discharged into the saturator tank, a small part of the waste water (120) is separated from the tank part of the saturator / AS / and returns to the appropriate stage of the process.

The waste gas separating from the absorption device, mainly from the saturator (AS), usually contains in the DMT process waste by-products such as carbon monoxide as well as low-boiling compounds such as acetaldehyde, formaldehyde, methyl acetate, dimethyl ether, acetic acid as well as its methyl esters. In order to remove these by-products as environmentally as possible, the pressurized exhaust gas must be subjected to catalytic additional combustion.

For catalytic additional combustion (KNV), the catalyst of the invention is added here. The catalytic additional combustion reactor is generally a fixed catalyst reactor and can absorb both as a bulk catalyst and 10 as a monolithic catalyst. Preferably, cell-structure monoliths are characterized by very limited and low pressure loss, which has a positive effect on the method according to the invention for the treatment of waste gases, especially when recovering energy through a gas turbine.

In the process according to the invention the catalytic additional combustion is carried out for 20 preferably at a pressure between 2 and 20 bar, especially preferably from 5 to 20 bar, and an operating temperature between 160 and 650 ° C, especially preferred from 200 ° to 550 ° S. The catalytic additional combustion 25 in the process according to the invention is preferably carried out at a volumetric rate (GHSV) of 1000 h ' ¹ to 50 000 h ¹ , especially preferably 5000 h' ¹ to 30 000 h ' ¹ .N.

You

GHSV = -V.

Nm ³ m ³ .h _{VT. As} Vi.NV = volume flow at the rate [Nm ³ i ^and ° bam of the catalyst [t ³ ]].

For the first commissioning of the reactor (KNV), the process air is generally heated (141) by means of an electric heat exchanger (W4) and carried through the reactor (KNV), until the desired operating temperature is reached in the latter. catalyst activation. Finally, the waste gas reactor can be started, powered. Preferably, the catalytic additional combustion proceeds further thermally. In the process according to the invention, the catalyst waste gas typically contains vapor water of 0.04 to 2.8 kg / Nm ³ , preferably 0.1 to 0.4 kg of water per Nm ³ waste gas.

Preferably, the waste gas more than 50 (150) for treatment is heated (160, 161, 170) before entering the catalyst region 35 as opposed to the effluent leaving the reactor (purified gas) (180). The heating is effected by a suitable arrangement of the respective heat exchangers (W2, W3).

The oxidation in the DMT process is so arranged in the process that the necessary oxygen in the waste gas used for catalytic combustion is present prior to the entry of the waste gas into the reactor. The oxygen content of the waste gas (130) can be increased if necessary by introducing pressurized air (140). In principle, the organic compounds and carbon monoxide present on the catalyst according to the invention can be almost completely converted to carbon monoxide and water. The oxygen content of the purified gas (180, 190) is preferably from 0.5 to 2 vol. %.

In order to regenerate the compressor energy, it is possible to purify the gas (190) through a single exhaust gas turbine / TU / to expand its volume to produce mechanical or electrical energy. For the recovery of energy, for its regeneration by means of a pressure reducing turbine (turbo expander), such purified gas streams are generally used, preferably at a pressure higher than 3 bar. As the exhaust gas generally meets the requirements, it can be vented through the fireplace / 210 /. It is possible here to adjust the temperature by supplying unheated air so that the exhaust gas leaving the exhaust / waste / gas turbine is at a temperature of 125 ° C.

In the process according to the invention, it is also possible for the flow of purified gas in front of the turbine to be at least partially diverted, cooled after a corresponding drying at a temperature lower than 40 ° C (WS) and then used (200) more appropriately. a way like inert gas, for example, for "purity" in the process.

The particular advantages of the process according to the invention are that, together with the good economic results achieved by the catalyst, the use of exhaust gases, the combustion of all waste by oxidation and the by-products passing into the exhaust and minimizing the content of carbon monoxide in the purification are achieved. gas to such values that cannot be captured by enterprise metering devices.

Examples of implementation

Example 1. Preparation of a catalyst for the purification of exhaust gas from oxidation in an atmospheric DMT process.

2000 g of commercial, tubular catalyst support on a titanium dioxide base (Type H9050 from Huls AG) are placed in a rotating drum and heated by hot gas to 110 ° C. After reaching this temperature for 20 min at 110 ° C, 500 ml of an aqueous solution of platinum nitrate with W / Pt / = 5.2 g / l are injected. The solvent is then evaporated and the metal deposited in a thin boundary zone on the support. Finally, the material was separated and calcined in a gas stream for 4 hours at 450 ° C.

Example 2. Purification of flue gas from oxidation in an atmospheric DMT process.

In FIG. 1 shows a preferred embodiment of the method according to the invention for the purification of exhaust gas under oxidation in an atmospheric DMT process. Tables 1a + c show the flows of substances and their composition during technological conditions (compare legend). The amount of exhaust gas and the amount of exhaust water, as well as their composition, are typical of a DMT / PTA device with a capacity of 240 kt / a.

The effluent and substantially product-free condensate and absorption effluent is introduced as a flow (110) at the bottom of the saturator (AS) and is in the amount of 70 768 kg / h and has a temperature of 120 ° C. Exhaust water (20,000 kg / h / 100) is introduced into the upper part of the saturator, which comes from the DMT / PTA device. The saturator has either a valve floor or a structured arrangement. The spent water is moved by means of a circulation pump / P1 / through one heated by a low pressure steam heat exchanger / \ ¥ 1 / in a closed cycle / 121 /. In order to eliminate the enrichment of solids in the saturator and the possibility of functional disturbances resulting from the device, a small part of the product from the scrubber tank is discarded / 120 / and reintroduced into the DMT / PTA process at the appropriate place. .

For the reactor (KNV) to be put into operation, process air (141) is introduced through an electrically heated heat exchanger (W4) into the catalytic afterburner until such a temperature is reached. which guarantees the start of the reaction. The flushed exhaust gas (130), which is saturated with water and also with the substances contained in the exhaust water, is heated from a temperature of 121.5 ° C at a pressure of 7.1 bar through a heat exchanger with a counter flow to a temperature of 250 ° C / 150, 160, 170 / and is introduced into the catalytic supplementary combustion reactor.

The inlet temperature of the exhaust gas before the reactor can be regulated both at start-up, at start-up, and during normal operation on the mass flow rate (161). The oxygen required for combustion of air can be introduced further through the mass flow rate (140).

The reactor / KNV / is complete with Huls AG type H 5922 catalyst (compare Example 1) and is operated at a volumetric rate calculated by the formula 30,000 [·

The combustion is complete and only relatively small excess oxygen is required.

Due to the reaction heat of the exothermic combustion process, the purified exhaust gas (pure gas) leaves the reactor at a temperature of 401 ° C / 180 / and is fed into the heat exchanger housing (W2, W3) to heat the exhaust gas, whereby the pure gas is cooled. to a temperature of 277 ° C (190) and through the exhaust gas turbine (TLJ), which is connected to the air compressor, expands to normal pressure (210) and is discharged into the atmosphere through the chimney.

For the production of inert gas, it is possible to partially cool the purified gas / 190 / and reuse it in the DMT / PTA device such as Blanket / 200 /.

Legend to Figure 1, Table 1 and flow mass flow

Figure 1 shows a preferred embodiment of the method according to the invention for the purification of exhaust gases from oxidation in the atmospheric - DMT process.

Flow rates in Figure 1 and Table 1a and b.

100 - process water:

110 - exhaust gas from the condensation or absorption device, respectively;

120 - tank product, return to process;

121 - Saturation cycle;

130 - Exhaust gas from the saturator;

140 - pressurized air;

141 - pressurized air for starting the reactor;

142 - intake air;

150 - exhaust gas enriched with oxygen;

160 - exhaust gas flow for heat exchangers W 2 + 3;

161 - Exhaust gas flow to control reaction temperature:

170 - exhaust gas through the heat exchanger with counterflow heated before the reactor;

180 - purified gas after reactor;

190 - purified gas after the heat exchanger with counterflow;

200 - cooled and pressurized partial stream of clean gas, returning it back into the process as inert gas;

210 - partial, low pressure stream of clean gas, before the fireplace;

Technical equipment in Figure 1. AS-saturator;

P1 - pump;

W1 - steam-driven heat exchanger; W2 + 3 - counter-current heat exchanger; KNV - Catalytic Combustion Reactor;

W4 - electrically driven heat exchanger;

W5 - heat exchanger;

TU - volume expansion turbine / pressure reduction /;

Legend to Tables 1a and b.

for Figure 1, the flow rates, their composition and operating conditions are shown in Tables 1 a and b.

Legend for abbreviations p-X - paraxylene;

p-TA - paratoluyl acid;

p-TE - paratoluyl acid methyl ester;

BME - benzoic acid methyl ester;

HM-BME - Hydroxymethylbenzoic acid methyl;

MM-BME - methoxymethylbenzoic acid methyl ester;

DMT - dimethyl terephthalate;

DMT crude - crude ester (DMT flow esterification trail DMT);

crude-DMT - fraction of dimethyl terephthalate after distillation of the crude ester;

DMT-pure - dimethyl terephthalate-pure (DMT with high purity - intermediate or final product);

DMO - dimethylorthophthalic acid;

DMI - dimethylisophthalic acid;

DMP - dimethyl phthalate = isomer mixture of DMT, DMO and DMI;

MMT - monoethyl terephthalate (monomethyl terephthalic acid ester);

TA - terephthalic acid;

MTA - Terephthalic acid of medium purity;

PTA - higher purity terephthalic acid;

PTA-p - Terephthalic acid with very high, this means the highest purity / content of MMT and p-TA together of 50 wt-ppm /

TAS - terephthalaldehyde acid (4CBA);

TAE - terephthalaldehyde acid methyl ester formaldehyde-OMA-formaldehyde dimethylacetal; acetaldehyde-OMA-acetaldehyde dimethylacetal;

Table la.

Flow rate 100 110 120 130 140 150 170 180 190 210 Quantity / kg / h / 20000 70768 568 90200 54 90254 90254 90254 90254 90254 Amount / m ³ / h / 16229 7.97 16242 21648 28382 23109 106052 Temperature / ° C / 35 120 105 121.5 110 122 250 401 277 123 Pressure / Lug / 7.1 7.1 7.1 7.1 7.5 7.1 7 7 6,9 1.1 Composition kg kg kg kg kg kg see 150 kg see 180 kg Water 19094 159,3 534 18719 18719 19250 19250 Methanol 2 22 0.1 23,7 23,7 p-TE follow follow follow follow p-xylene 4.6 4,8 4,8 VME follow 26.5 0.03 26.5 26.5 Acetic acid 520 0.03 25.9 494,3 494,3 Formic acid 240 0.3 7.7 232,8 232,8 Formaldehyde Acetaldehyde 132 0.1 131,9 131,9 Methyl acetate 2 11,77 13.7 13.7 Ethyl acetate follow follow follow follow Composition kg kg kg kg kg kg kg kg kg kg Dimethyl ester Methyl- follow follow follow follow formate 10 8 0.1 17,8 17,8 Formaldehyde- FTA Acetaldehyde follow follow follow follow FTA follow follow follow follow Nitrogen 66051 0.04 66051 41,4 66092,4 66090 66090 Oxygen 1957 1957 12.60 1969,6 794 794 with ₂ 2038 0.03 2038 2038 4120 4120 CO., LTD 489,5 489,5 489,5 0 0

Table 16

Flow rate 100 110 120 130 140 150 170 180 190 210 Mengen / kg / h / 20000 70768 568 90200 54 90254 90254 90254 90265 90254 Amount / m ³ / h / 16229 7.97 16242 21648 28382 23109 106052 Temperature / ° C / 35 120 105 121.5 110 122 250 401 277 123 Pressure / Lug / 7.1 7.1 7.1 7.1 7.5 7.1 7 7 6,9 1.1 Composition % by weight % by weight % by weight % by weight % by weight % by weight see 150 % by volume see 180 % by weight Water 95.47 0.23 94.01 20,75 20,74 21.33 21.33 Methanol 0.01 0.03 0.02 0.03 0.03 p-TE follow follow follow follow p-xylene 0.01 0.01 0.01 VME follow 0.04 0.01 0.03 0.03 Acetic acid 2.60 0.00 4,56 0.55 0.55 Formic acid 1,20 0.00 1.36 0.26 0.26 Formaldehyde Acetaldehyde 0.66 0.02 0.15 0.15 Methyl acetate 0.01 0.02 0.02 0.02 Ethyl acetate follow follow follow follow Composition ι % by weight % by weight weight% % by weight % by weight wt. 7 , see 150 weight% Sh180 t % Dimethyl ether follow follow follow follow Formaldehyde methyl formate- 0.05 0.01 0.02 0.02 0.02 FTA follow follow follow follow Acetaldehyde FTA follow follow follow follow Nitrogen 93.33 0.01 73.23 76.67 73.23 73.23 73.23 Oxygen 2.77 2.17 23,33 2.18 0.88 0.88 C0 ₂ 2.88 0.01 2.26 2.26 4,56 4,56 CO., LTD 0.69 0.54 0.54 0 0

Claims (21)

1. A catalyst for the purification of pressurized exhaust gases as they fall off after oxidation of paraxylene / p-X / with liquid phase air to form dimethyl terephthalate (DMT), characterized in that it contains the following components: a / at least one titanium oxide and b) at least one element of VIII subgroup of the periodic table of elements in metallic and / or oxidic form. Catalyst according to claim 1, characterized in that it contains as components platinum and / or palladium and / or rhodium. Catalyst according to claims 1 and 2, characterized in that it contains components a) from 50 to 99 wt.% And components b) in an amount from 0.01 to 5 wt.%, Wherein the components b / are calculated in total and as a metal, at some point relative to the weight of the catalyst. A catalyst according to at least one of claims 1 to 3, characterized in that it contains c / sulfate as a component. Catalyst according to claim 4, characterized in that it contains components with / from 0.1 to 10.0 wt.% By weight of the catalyst. Catalyst according to at least one of Claims 1 to 5, characterized in that it contains as additional components barium sulphate and / or tungsten oxide and / or vanadium oxide and / or zirconium oxide and / or the corresponding sulfate and / or phosphate and / or silica and / or silicate. Catalyst according to at least one of claims 1 to 6, characterized in that it contains titanium oxide, which is usually in anatase form. A catalyst according to at least one of claims 1 to 7, characterized in that it has a cellular structure. A catalyst according to at least one of claims 1 to 8, characterized in that the components b / are predominantly located in the area of the surface of the molded catalyst. 10. A process for the preparation of a catalyst according to claims 1 to 9, characterized in that the components b / are applied to molded articles which contain at least the components a /, alone or in a mixture, by immersion and / or impregnation by spraying. A method according to claim 10, characterized in that molded bodies with a BET surface between 10 and 200 m ² / g and a pore volume of 0.1 to 0.6 cm ³ / g are used. 12. The method according to claim 10 or 11, characterized in that a solution is used to impregnate the molded articles, for the preparation of which components b / as nitrate are applied. Method according to at least one of Claims 10 to 12, characterized in that the impregnated molded bodies are thermally treated with air intake. 14. Method for purification of pressurized exhaust gas, such as that which is eliminated after oxidation of paraxylene / p-X / with air in liquid phase in the preparation of dimethyrephthalate (DMT), whereby the pressurized oxygen containing exhaust gas from oxidation further undergoes one-stage or multi-stage condensation, one-stage or multi-stage absorption and then undergoes pressure-triggered catalytic supplementary combustion upon introduction of oxygen, characterized in that it afterburning using a catalyst according to Claims 1 to 13. 15. A method according to claim 14, characterized in that the catalytic additional combustion is carried out at a temperature of 160 ° C to 650 ° C and a pressure of 2 to 20 bar. A method according to claim 14 or 15, characterized in that the catalytic additional combustion is carried out at a volumetric rate (GHSV) of from 1000 h ¹ to 50 000 h '. A method according to at least one of claims 14 to 16, characterized in that, after the last degree of absorption, the process water containing the organic components passes through the exhaust gas saturator. A method according to at least one of claims 14 to 17, characterized in that the exhaust gas before the catalyst contains vapor water from 0.04 to 2.8 kg / Nm ³ . A method according to at least one of claims 14 to 18, characterized in that the purified catalyst and the pressurized exhaust gas reduces its pressure (increases its volume) in a turbine to produce mechanical or electrical energy. 20. A method according to claim 19, characterized in that the catalytic purified exhaust gas is at least partially regenerated by the still contained energy in the exhaust gas, wherein the pressurized gas is greater than 3 bar, the exhaust gas flow is expanded into a turbo generator to produce mechanical and / or electrical energy. A method according to at least one of claims 14 to 20, characterized in that the purified exhaust gas is further used as an inert gas.