EP1420882A1

EP1420882A1 - Catalytic converter for food cooking appliances

Info

Publication number: EP1420882A1
Application number: EP02796328A
Authority: EP
Inventors: Jean-Marc Payen
Original assignee: SEB SA
Current assignee: SEB SA
Priority date: 2001-08-31
Filing date: 2002-08-30
Publication date: 2004-05-26
Also published as: FR2829040A1; FR2829040B1; US7069838B2; WO2003018190A1; US20050011369A1

Abstract

The invention concerns a catalytic converter designed to be incorporated in a food cooking appliance for treating, during a cooking cycle under closed atmosphere without external oxygen input, the cooking flux smells before said flux is expelled outside, said converter comprising a base substrate (30) provided with perforations (31) allowing through the cooking flux to be treated, said substrate (30) being coated with an intermediate layer (32) having a wide surface area, provided itself with a surface component (33) formed with an inorganic solution based on precious metal to form an active catalytic layer of the converter. The invention is characterised in that the intermediate layer (32) comprises alumina and albanite to form an intermediate layer (32) with a surface area not less than 150m<2>/g, the alumina/albanite input on the base substrate (30) ranging between 30 and 35 g/m<2>, of which 15 to 25 g/m<2> of albanite. The invention concerns catalytic converters, in particular for fryers.

Description

CATALYTIC CONVERTER FOR FOOD COOKING APPLIANCES

TECHNICAL AREA

The present invention relates to the general technical field of catalytic converters enabling the treatment of odorous fluids to make them odorless, the present invention more particularly relating to catalytic converters intended to treat cooking odors, in particular fried odors, resulting from cooking food in a household food cooking appliance.

The present invention relates to a catalytic converter intended to be integrated in a food cooking appliance, of the fryer type, for treating, during a cooking cycle in a closed atmosphere and without external oxygen supply, the odors of the flow. cooking before the discharge to the outside of said stream.

PRIOR ART

In food cooking appliances, in particular in fryers, it is known that the immersion of the food to be cooked in oil or fat heated at high temperature is accompanied by the release into the air of chemical substances. , with a strong typical and unpleasant odor characteristic of the actual frying operation. The chemicals released into the air and responsible for the unpleasant odor are known and are mainly volatile organic substances (VOC), aldehydes and acids. It is obviously already known to have recourse to various treatment means having the aim of avoiding or treating the steam flows resulting from the cooking of food in such cooking appliances.

One of the first known processing means obviously consists in cooking the food in a closed atmosphere by making a sufficiently tight junction between the tank and the cover of the appliance.

However, for obvious safety reasons, in particular in fryers where, due to the importance of the vapors produced by food during frying (especially potatoes), it is necessary to leak the flow of cooking, such devices are equipped with cooking odor processing means to rid the cooking flow of all or part of the volatile molecules responsible for the cooking odor.

Various devices have been envisaged, and the use of activated carbon filters is known in particular making it possible to retain all or part of the fat, as is for example described in patent FR-1,568,985 or in patent EP-150 516 for example.

However, to be effective, activated carbon filters must be changed frequently in the cooking appliance, which constitutes an additional constraint in the design of the appliance, since it is imperative to plan to design a mounting system and disassembly of the activated carbon filter. Furthermore, it can be seen that the user frequently forgets to change the activated carbon filter, such an operation being moreover perceived as a constraint. All of these factors combine to make the use of activated carbon filters ineffective for the treatment of cooking odors. In addition, they are not absolutely and universally effective while leaving visible the treated flow then rejected and out of the device. There is also known a fryer odor treatment system which consists in condensing the cooking vapors in a condensing system mounted in the appliance. Such a system does not have the drawbacks of changing all or part of the system as required by the activated carbon filters, but requires on the part of the user a relatively tedious handling with each cooking operation. Indeed, the condensing system must be kept at very low temperature, for example in a freezer, during all periods of non-use to be mounted in the cooking appliance itself before any cooking operation, all the more that this system requires emptying the tray after cooking. Reloading in the cold does not allow a second cooking before 24 h with the same system. This systematic assembly can be perceived as an additional constraint by the user. Furthermore, it turns out that the condensing systems are generally of a large volume, which constitutes an additional design constraint, insofar as it is necessary to integrate this system into the cooking appliance, which should generally be limited. size.

Finally, it is already known to use a catalytic converter mounted in the lid of a fryer to ensure the treatment of cooking odors. The use of catalytic converters avoids any specific manipulation in comparison with systems including activated carbon filters or condensing systems, since the catalyst is permanently installed in the device and therefore forms a permanent odor treatment unit.

However, it turns out that the design of a catalytic converter intended to be integrated in a food cooking appliance, and in particular in a fryer, is difficult to implement, and the converters known catalytics applied, moreover exceptionally to fryers, are not satisfactory.

The design of a catalytic converter intended to be integrated into a food cooking appliance is made particularly delicate because of the need to keep the cooking appliance completely closed during a cooking cycle, which implies that no input external oxygen does not take place during a complete cooking cycle, which therefore takes place in an atmosphere which is substantially closed, except for leaks.

This constraint implies on the one hand that the entire cooking flow passes through the catalytic converter, and on the other hand that the catalytic converter can react properly during the entire cooking cycle without any external supply of oxygen, by being satisfied to optimally use the initial volume of fluid contained inside the cooking chamber.

Furthermore, to be effective, the catalytic converter must be designed in such a way that the vapors resulting from the cooking flow can pass freely through the converter, without, however, excessive passage speeds, in order precisely to ensure a good treatment of vapors in the active part of the catalyst itself.

Finally, it is understood that the catalytic converters intended for an application in the household appliance sector must meet conventional criteria of reliability, reduced costs and longevity.

STATEMENT OF THE INVENTION

The object assigned to the invention therefore aims to remedy the various drawbacks of the prior art mentioned above and to to meet the needs also mentioned previously, and to propose a new catalytic converter intended to be integrated in a food cooking appliance, to treat, without external oxygen supply, the odors of the cooking flow before their rejection towards the outside , said converter being of good efficiency while being of a size suitable for its application, and of a reduced cost.

Another object of the invention is to propose a new catalytic converter which is of high efficiency and which makes it possible to ensure optimal contact between the flow to be treated and the active parts of the converter.

Another object of the invention is to propose a new catalytic converter which is effective for a substantial service life, in particular for a domestic fryer.

The objects assigned to the invention are achieved using a catalytic converter intended to be integrated into a food cooking appliance for processing, during a cooking cycle in a closed atmosphere and without external input of oxygen, the odors of the cooking flow before the discharge to the outside of said flow, said converter comprising a base substrate provided with perforations for the passage of the cooking flow to be treated, said substrate being coated with an intermediate layer having a large surface area, itself provided with a surface component formed of an inorganic solution based on precious metals to form the catalytic active layer of the converter, characterized in that the intermediate layer comprises alumina and cerine for forming an intermediate layer with a surface area at least equal to 150 m ² / g, the addition of alumina / cerine to the base substrate being between 30 and 35 g / m ^{2 of} which 1 5 to 20 g / m ² of cerine. SUMMARY OF DRAWINGS

Other objects and advantages of the invention will appear in more detail on reading the description which follows, with reference to the appended drawings given by way of illustrative and nonlimiting examples in which:

- Figure 1 illustrates, in a general perspective view, a food cooking appliance according to the invention, in this case a fryer incorporating a catalytic converter according to the invention.

- Figure 2 illustrates, in a partial sectional view taken along a cross section, an embodiment of a catalytic converter according to the invention.

- Figure 3 shows a comparative graph from practical tests illustrating the efficiency of the catalytic converter according to the invention.

- Figure 4 shows a comparative graph from practical tests illustrating the influence of platinum deposition on the efficiency of a catalytic converter according to the invention.

- Figure 5 illustrates, in a schematic view in cross section, an embodiment of a catalytic converter according to the invention.

BEST WAY TO IMPLEMENT THE INVENTION

In the exemplary embodiments illustrated in Figures 1 to 5, the food cooking appliance according to the invention and described is constituted by a fryer intended for and designed for the production of fried foods of all kinds in fat, such as an oil bath for example. Within the meaning of the invention, it should nevertheless be understood that the term food cooking appliance covers all household food cooking appliances capable of cooking food, the application to fryers of the fryer type being only a preferred application, the invention which can obviously also be applied to other applications such as rice cookers or multipurpose cookers, from the moment when these cooking appliances implement cooking in a cooking fluid contained in a closed enclosure that is substantially sealed .

The food cooking appliance illustrated in FIGS. 1 and 2, in this case an electric fryer, comprises a base 1 intended to form the base of the appliance and intended to rest on a surface or a support. The base 1 is generally secured to an external skirt 2 or attached to the latter, which is made for example of metallic material or of plastic material resistant to heat and forming the external envelope of the fryer. The outer skirt 2 is nevertheless conventionally made of an inexpensive plastic material that is not very resistant to heat such as polypropylene, not resistant to the thermal energy dissipated continuously by the high-temperature heating element or elements conventionally used in electric fryers, and generally arranged at the bottom close to the base 1.

The device's heating means (not shown in the figures) may be internal to the device and conventionally composed of shielded elements or equivalent elements, also conventionally connected to an electrical connection block (not shown) and electrical wiring to connect the device to the network. In a manner also known to those skilled in the art, the cooking appliance according to the invention will be provided with all of the electrical and electronic safety means such as temperature sensors, fuses, etc., required for the design of these devices. These elements being well known to those skilled in the art, they will therefore not be described in more detail in the following description. The heating means can also be external to the device and separate or separable from the latter.

According to the invention, the fryer will have a cover 7 removably mounted, articulated relative to the main body of the fryer and intended to close, in a substantially sealed manner, for example by means of seals (not shown in the figures ), said main body during cooking.

Advantageously, and as shown in Figures 1 and 2 in particular, the cover 7 may be provided on its upper face 8 with a window 9 for monitoring the progress of cooking or frying during the cooking cycle, and when the cover is closed on the main body.

The cooking of food in a closed environment in a cooking fluid, whether it is steam cooking or frying, generates the production of characteristic and often unpleasant odors resulting from the chemical reactions linked to the cooking proper, and in particular to the emission of volatile organic substances.

The appliance for cooking food in a closed atmosphere therefore comprises a tank (not shown), a cover 8 and internal or external means for heating the appliance for cooking. It further comprises a thermal treatment system for cooking odors, namely a catalyst sub-assembly 10, to ensure the treatment of odors from the cooking flow before they are discharged to the outside of the appliance.

According to the invention, and as illustrated for example in FIG. 2, the catalyst sub-assembly 10 comprises at least one heating element 11, the appliance further comprising means for regulating the temperature of said heating elements 11, said regulating means being arranged to sense the temperature of the cooking zone.

Thanks to this arrangement, it is therefore possible to regulate the temperature of the heating elements 11 of the catalyst 10 by a thermal image which is not located in the catalyst itself but which corresponds to an image representative of that prevailing in the fluid. Cooking.

According to a particularly advantageous version of the invention, the catalyst sub-assembly 10 is formed by a housing 15, which is mounted and integrated in the cover 8 of the device.

The housing 15 contains a catalytic cell or catalytic converter 16 forming the upper part of the housing 15 and extending in the vicinity of the external face of the cover 8. The housing 15 also contains the heating elements 11 which extend in the vicinity and under the catalytic converter 16 for heating it by radiation, without the appearance of hot spots. The housing 15 is provided with inlet orifices 17 for the cooking flow to be treated, said orifices 17 being for example formed through a lower plate 18 made of stainless steel of said housing 15 located substantially in line with the cooking vessel, the elements of heater 11 being interposed between the orifices 17 and the catalytic cell 16, and arranged substantially in line with said orifices 17.

Thanks to this arrangement, a homogeneous and efficient heating of the cooking flow to be treated is obtained, which ensures proper operation and good efficiency of the catalyst.

Advantageously, the heating elements 11 are formed by an electrical resistance in a coil or in a helix for example. Advantageously, and to obtain excellent efficiency in the treatment of odors, the heating elements 11 will have a maximum thermal load at most equal to 3 w / cm ² , and preferably less than or equal to 2.5 w / cm ² . This makes it possible to obtain a maximum temperature of the order of 600 ° C. in treatment, which avoids overheating and makes it possible to maintain homogeneity in the treatment of the vapors.

According to an advantageous feature of the invention, the heating elements 11 are connected to an electrical circuit comprising a switch 20, such as a microswitch associated with the position of the cover 8, so that the switch 20 cuts the power supply to the heating elements 11 as soon as the cover is opened or removed.

The safety of use of the appliance can be increased by mounting an ambient safety thermostat 25 in the appliance in the vicinity of the catalyst 10.

Advantageously, a counterplate 26 can be integrated under the housing 15 and at a distance from the latter to provide a thermal brake and protect the plastic structure of the cover 8 in the event of temporary overheating.

Conventionally, the catalytic cell 16 may be made of material of the cordierite, ceramic or Zirconia Nullity type with standard calibrated holes of 100 or 400 CPSI (15.52 or 62.09 cells / cm ² ) or of foam type in the supports 20 PPI (196.85 g / cm) for example, such as those of the company SICAT. It is also possible to envisage using silicon carbide foams.

The surface area of the catalytic cell 16 is calculated so as to avoid pressure drops and so as to have an acceptable transit vapor speed. By way of example, the base surface of the catalytic cell 16 could be 4,000 mm ² for a height of at least about 30 mm with calibrated holes of 200 or 400 CPSI (15.52 or 62.09 cells / cm ² ). According to another alternative embodiment, the catalytic cell may have a base surface of the order of 8,000 mm ² with a reduced height of 12 mm for holes calibrated with 200 or 400 CPSI (15.52 or 62, 09 cells / cm ² ).

During the cooking operation, the cooking vapors are directed towards the inlet E of the catalyst 10 so as to penetrate into the orifices 17 after being distributed in an inlet channel situated under and along the said orifices. admission 17.

The cooking flow is then preheated or heated by passing over the heating elements 11, then is treated by catalysis by passing through and in the catalytic cell or catalytic converter 16 before escaping and being discharged outside of the fryer, preferably backwards through outlet S.

In addition to the treatment of odors when passing through the hot parts of the catalyst, there is a pyrolysis of the oil vapors contained in the vapors which ensures complete treatment of the cooking flow at its outlet.

Thus, the catalytic converter 16 is intended to be integrated in a food cooking appliance, in this case preferably a fryer, for treating, during a cooking cycle in a closed atmosphere and without external oxygen supply. , the odors of the cooking flow before the discharge to the outside of said flow. The catalytic converter 16 used operates in a known manner on the basis of catalytic reactions involving complete oxidation reactions, allowing the oxygen in the air to react on the active surface of the converter with the odorous substances, in order to obtain odorless transformed elementary substances. The general principle of catalysis is therefore to maintain the catalytic converter at very high temperature, so that the cooking flows, in this case the fried fumes in the case of a fryer, react on the catalyst to transform into dioxide. carbon and water vapor.

According to the invention, the catalytic converter 16 (FIG. 5) comprises a base substrate 30 provided with perforations 31 for the passage of the cooking flow to be treated before being discharged outside the appliance, said substrate 30 being coated with an intermediate layer 32 having a large surface area, itself provided with a surface component 33 therefore constituting the surface area for exchange of the catalyst, said component being formed of an inorganic solution based on metals valuable for forming the active catalytic outer layer of the converter 16. According to the invention, the intermediate layer 32 comprises alumina (aluminum) and cerine (cerium) to form an intermediate layer 32 whose surface area is at least equal to 150 m ² / g. The function of cerine is to compensate for the lack of oxygen during the cooking cycle, and thus allows a permanent catalysis reaction to be obtained, while the minimum surface area (150 m ² / g of intermediate layer) makes it possible to maximize the dispersion of the cooking flows through the converter and optimize the treatment efficiency, while obtaining a long service life of the converter.

Taking into account the particular domestic application aimed implying an intermittent use of the device and a lifespan of the order of 200 hours, the concentration and the contribution of alumina / cerine will be important in comparison with the applications. conventional catalysts, for example in exhaust pipes. Thus, for a fryer, the cerine / alumina ratio will be between 1 and 1.50 and preferably of the order of 1.33, the intake limit being the appearance of a sticky structure of the intermediate layer capable of clogging the pores and therefore reducing the treatment efficiency.

To further improve the efficiency of the catalytic converter according to the invention, it has been found that the surface area of the base substrate 30 must also respect a minimum surface area.

Thus, it appeared that good odor treatment results could also be obtained when the base substrate 30 has a minimum surface area of at least 0.0034 m ² / liters of treated water vapor per minute.

These minimum parameters of the catalytic converter 16 correspond, for example for a fryer having to process a quantity of potato of the order of 1 to 1.25 kg with a heating power of 2000 Watts, to the following criteria:

- average quantity of vapor passing through the catalyst: 600 g, - molecular weight of water: 18 g / mol,

- normal temperature condition: 273 K,

- consistency of ideal gases: 0.0821,

- volume of steam to be treated: 747.11 L,

- cooking time (cooking cycle): 13 min, - quantity of steam passing through the catalyst: 57.5 L / min.

For an untreated cell with a diameter of 102 mm and a height of 12.5 mm with 196 perforations per square inch (PSI) (30.42 perforations / cm ² ) with a wall thickness of 0.24 mm, the surface area of the substrate is base calculated on 2,500 perforations in total is of the order of 0.196 m ² (approximately 0.2 m ² ). A catalytic converter sized this way has been found to give excellent results.

According to the invention, excellent results can be obtained when the base substrate 30 has between 190 and 400 perforations 31 per square inch (PSI) (29.49 and 62.09 perforations / cm ² ), and preferably about 200 perforations PSI (31, 04 perforations / cm ² ).

The substrate 30 is a monolithic material with a honeycomb, alumina or cordierite structure, having a very low coefficient of thermal expansion and a high resistance to high temperatures and to thermal shocks.

The perforations 31 may be of any suitable shape and of any suitable section, and for example circular or hexagonal, and are obtained according to techniques well known to those skilled in the art, involving the kneading of selected earths, while retaining a rate specific humidity, then performing a series of cooking and evaporation cycles.

Due to its relatively low cost, cordierite will be the preferred substrate material.

The intermediate layer 32 (washcoat), which acts as a support for the active phase of the catalytic converter, is an inorganic solution which is affixed, by soaking or spraying with alumina, on the base substrate 30. The incorporation of cerine can be carried out during the alumina dipping or spraying operation, to obtain a distribution as homogeneous as possible of the cerine in the intermediate layer.

As is well known to those skilled in the art, different types of alumina are obviously usable. In the example of realization given previously, the coating of the intermediate layer 32 corresponds to a minimum supply of 7 g of alumina / cerine, the surface of the base substrate 30 corresponding to approximately 0.2 m ² (35 g / m ² ) including 4 g of cerine or 20 g / m ² of cerine.

Preferably, the supply of alumina / cerine will therefore be approximately 35 g / m ² of surface area of the base substrate 30. It will also be possible to substantially reduce the supply of alumina and cerine to 3 g each. to arrive at intakes of approximately 30 g / m ² of alumina / cerine, or 15 g / m ² of cerine, while retaining good treatment efficiency, in particular in a domestic fryer operating with a closed lid. In total, the invention therefore involves an addition of alumina / cerine to the surface of the base substrate 30, between approximately 30 and 35 g / m ² , including 15 to 20 g / m ² of cerine.

According to the invention, the surface component 33 is an inorganic solution comprising a precious metal or a mixture of precious metals or else a mixture of oxides of one or more of these precious metals chosen from, in particular, platinum, copper , manganese, palladium, etc. Advantageously, and for cost reasons, the preferred precious metal within the meaning of the invention will be platinum, having a vapor pressure low enough to avoid loss of active substances during operation. The metal chosen must moreover not allow initiation of chemical formation reactions between the surface component, which forms the active part of the catalytic converter, and the intermediate layer 32.

According to the invention, the chosen metal (preferably platinum) may be deposited when the intermediate layer 32 is added or at a later stage, the latter solution being preferable from the economic point of view, since it makes it possible to disperse quantities lower platinum. According to the invention, the chosen metal (preferably platinum) is dispersed in the intermediate layer 32 and on its surface, at a rate of at least 0.02380 mg / m ² and at most 0.06666 mg / m ² , which corresponds respectively to values between 25 and 70 mg of platinum supply on the minimum surface area of the intermediate layer 32. Given the large proportion of cerine in the intermediate layer 32, the good efficiency of treatment necessarily implies that the platinum is on the surface of the intermediate layer 32.

The practical tests carried out, the results of which are given in FIGS. 3 and 4, correspond to the olfactory determination of the odors discharged into the atmosphere by a fryer provided with a catalytic converter having variable characteristics. The olfactory determination was carried out by submitting the odors to a jury, composed of at least nine people minimum, and by comparing the results obtained with the results of olfactometric analyzes carried out using an olfactometer at dilution, the measures selected must be correlated with at least the results noted by half of the jury.

The results obtained relate to the intensity of the odor linked to the scale of the odor felt, which can be more or less pleasant or more or less unpleasant.

The results of FIG. 3 show the incidence of the value of the surface area of the intermediate layer 32. Thus, the results shown in FIGS. 3 and 4 correspond to a standard fryer as defined above and therefore corresponding to a power of heats on the order of 2000 Watts, and a food processing capacity on the order of 1 to 1.25 kg of fries. According to these graphs, it appears that the fryers provided respectively with a catalytic converter Ii and I ₂ , corresponding respectively to a surface area of the intermediate layer 32 of 1,050 m ² (200 PSI perforations) (31,04 perforations / cm ² ) and 2,000 m ² (200 PSI perforations) (31,04 perforations / cm ² ), are the only fryers to reject cooking fumes including l odor is pleasant and of weak intensity, sign of an effective treatment.

We also note the higher efficiency of the catalytic converters having surface areas of the upper intermediate layer 32. The still higher results, corresponding to the upper part of the dotted curve in FIG. 3, moreover correspond to catalytic converters whose number of perforations 31 per unit area is greater and of the order of approximately 400 PSI.

On the other hand, fryers equipped with catalytic converters A, B and C with:

- A: surface area of the intermediate layer 32 of 800 m ² with a calibration of the perforations 31 greater than 200 PSI (31, 04 perforations / cm ² ),

- B: surface area of the intermediate layer 32 of approximately 800 m ² with a calibration of the perforations 31 of the order of 100 PSI (approximately 15.52 perforations / cm ² ),

- C: surface area of the intermediate layer 32 of the order of 500 m ² obtained with foams or metallic grids, do not make it possible to effectively treat frying odors, since an unpleasant odor is constantly perceived, this odor being increasing in intensity when the treatment area decreases, all the more so as the density of the perforations 31 decreases and falls below the critical threshold of approximately 200 PSI.

The graph in Figure 3 therefore clearly highlights (for a fryer designed to process 1 to 1, 2 kg of potatoes) the limit values corresponding to the optimum of the design parameters to be implemented in a catalytic converter to obtain a significant effect on a cooking appliance.

The graph in FIG. 4 shows that for a catalytic converter (for a fryer designed to process 1 to 1.2 kg of potatoes) having a constant surface area of the intermediate layer 32, of the order of 1050 m ² , the catalytic converter C1 (25 mg of platinum filler) has an effective capacity for processing fried odors, and in any case greater than the catalyst C2 (50 to 70 mg of platinum) for the same ratio and supply of cerine. The catalytic converter C3 (25 mg of supply platinum but with a relative decrease in the share of cerine) presents non-significant results, precisely because of the decrease in the supply of cerine, which falls below the threshold of 4 g (for 1050 m ² in the example described) makes the catalytic converter ineffective.

For the catalytic converters C1 and C2, the surprising results obtained which show that beyond an intake of 25 mg of platinum, and for the same intake of cerine, the efficiency of the catalyst decreases the more the intake of platinum increases, can be explained by a kind of camouflage effect of platinum in the intermediate layer 32, not corresponding to a good yield of chemical reactions. This camouflage effect seems to be all the more important the higher the platinum intake, the optimal efficiency being on the contrary obtained for lower intakes (25 mg) of platinum.

The invention also relates to a process for treating smoke and cooking flows during a cooking cycle in a closed atmosphere, without external oxygen supply. POSSIBILITY OF INDUSTRIAL APPLICATION

The invention finds its industrial application in the manufacture and design of catalytic converters for domestic cooking appliances and in particular fryers.

Claims

- Catalytic converter intended to be integrated into a food cooking appliance to treat, during a cooking cycle in a closed atmosphere and without external oxygen supply, the odors of the cooking flow before discharge to the outside of said stream, said converter comprising a base substrate (30) provided with perforations (31) for the passage of the cooking stream to be treated, said substrate (30) being coated with an intermediate layer (32) having a large surface area, itself provided with a surface component (33) formed of an inorganic solution based on precious metals to form the catalytic active layer of the converter, characterized in that the intermediate layer (32) comprises alumina and cerine to form an intermediate layer (32) with a surface area at least equal to 150 m ² / g, the addition of alumina / cerine to the base substrate (30) being between 30 and 35 g / m ² of which 15 to 20 g / m ² of cerin e.

- Converter according to claim 1 characterized in that the base substrate (30) has a minimum surface area of at least 0.0034 m ² / liter of treated water vapor per minute.

- Converter according to claim 2 characterized in that the base substrate (30) has between 190 and 400 PSI perforations (29.49 and 62.09 perforations / cm ² ).

- Converter according to claim 3 characterized in that the surface component (33) is a metal or a mixture of metals or a metal oxide or a mixture of metal oxides chosen from platinum, copper, manganese, palladium. - Converter according to claim 4 characterized in that the surface component (33) is platinum dispersed in the intermediate layer at a rate of at least 0.02380 mg / m ² and at most 0.06666 mg / m ² .

- Converter according to claim 5 characterized in that the platinum is dispersed at the rate of about 0.02380 mg / m ² .

- Converter according to one of claims 1 to 6 characterized in that the base substrate (30) is a monolithic material with honeycomb, alumina or cordierite structure.

- Apparatus for cooking food in a closed atmosphere equipped with a catalytic converter according to one of claims 1 to 7.

- Apparatus according to claim 8 characterized in that it is constituted by a fryer.