The method of producing formaldehyde

 

(57) Abstract:

The invention relates to the field of chemical technology and can be used in the manufacture of formaldehyde in the chemical, petrochemical and other industries. The proposed method of producing formaldehyde is that the source of the reaction gas composition, vol.%: 6-12 methanol, and 4.5-7 oxygen, and the rest inert gas, sequentially passed through several layers of catalyst based on metal oxides. The temperature of the reaction gas inlet in each layer is supported at the level of 200-280oC. the partially reacted reaction gas add oxygen in a volume ratio of the reaction gas:oxygen = 1:(0.005 to 0.03 in) so that the oxygen concentration in the reaction gas was 2-6,5 vol.%. 1 C.p. f-crystals.

The invention relates to the field of chemical technology and can be used in the manufacture of formaldehyde in the chemical, petrochemical, woodworking and other industries.

In industry formaldehyde usually get two traditional ways: oxidation of methanol in the presence of the oxide, typically the total catalyst.

A known method of producing formaldehyde by oxidation of methanol in the presence of a catalyst containing the oxides of metals in two stages. In the first stage of the reaction gas, which consists of methanol and oxygen is passed through the catalyst located in the tube, outside the cooled coolant. Partially reacted in the first stage, the reaction gas is fed to the second stage, which consists in passing it through the catalyst bed operating under adiabatic conditions [1] This method imposes limitations on the performance of the unit, producing formaldehyde. The possibilities of modern machinery is not allowed to build units with the number of tubes for placement of the catalyst in the first stage, in excess of 10,000 pieces without compromising the reliability of these units [2]

There is also known a method of producing formaldehyde by oxidation of methanol in the presence of a catalyst containing the oxides of the metals, which consists in the successive passing the reaction gas through a few (mainly three to five layers of catalyst, each of which operates under adiabatic conditions. After the completion of each layer, the reaction gas is preheated with the heat of reaction of the DMA number is similar to the proposed invention features adopted for the prototype.

For the prototype high likelihood of fire and explosion hazard situations at work producing formaldehyde unit. This is because the source of the reaction gas should contain at least about 7. oxygen, which is close to the values characterizing the lower explosive limit. Lowering the oxygen content in the source of the reaction gas with respect to the specified impossible, as it will lead to the fact that in the last layers of the reaction mixture will be supplied with a low oxygen concentration and long-term operation of the catalyst under such conditions will cause its deactivation in these layers. But along with this practice shows that at the specified oxygen content in the source of the reaction gas to the catalyst in the last layers work in unfavourable conditions, as the residual oxygen concentration in particular reacted reaction gas before the last layer is not more than 3.5. which significantly reduces the efficiency of the catalyst, which is quickly deactivated when the lack of oxygen.

The present invention solves the problem of increasing the fire-fighting process for the preparation of formaldehyde by oxidation of methanol in utilizator.

The set task is solved by the fact that the source of the reaction gas composition: about 6-12. methanol, 4.5 to about 7. oxygen, and the rest inert gas, at a temperature of 200-280oC sequentially passed through several operating under adiabatic conditions the catalyst containing the oxides of metals. Thus by adding the partially reacted reaction gas of oxygen-containing gas in a volume ratio of the reaction gas:oxygen = 1: (0.005 to 0.03 in) support it (partly reacted reaction gas) oxygen concentration at the level of 3.8 to 6.0 about.

The method is carried out in a special reactor, performed with several successively installed catalyst. The catalyst contains oxides of metals such as iron, molybdenum, chromium, cobalt and belongs to the so-called oxide catalysts.

In the operating mode in the specified reactor continuously served the source of the reaction gas composition: about 6-12. methanol; 4.5 to about 7. oxygen, and the rest inert gas, for example nitrogen. The temperature of the source of the reaction gas support in the range of 200-280oC. When passing through the catalyst layers of the reaction gas, the oxidation of methanol with oxygen in obrazovanie under adiabatic conditions, after each layer and before applying the next, the reaction gas is cooled to the temperature of the source of the reaction gas. In addition, the partially reacted reaction gas, depleted in relation to the original oxygen add oxygen-containing gas in the ratio of the volume of the reaction mixture and oxygen equal to 1:(0.005 to 0.03 in) so that the oxygen concentration in the partially reacted gas was maintained at 3.8-6. Oxygen-containing gas can be introduced as in the catalyst layers, and between them, as needed. At the exit of the reactor to get high-quality bezmetallny formaldehyde.

Describes a method for formaldehyde in comparison with the known features high reliability in preventing explosion or fire inside the reactor, which is provided by the lower oxygen content in the source of the reaction gas to a safe level (4.5 to about 7.). And oxygen saturation partially reacted reaction gas promotes long-term and efficient operation of the catalyst in all layers.

In addition, the organization of the production of formaldehyde as described above also enables the preparation reactor polucha, before operation of the reactor the catalyst layers must be reheated to the temperature of the beginning of the oxidation reaction of methanol with oxygen. Usually with this aim through the reactor miss hot air or any inert towards the catalyst a gaseous coolant. The heated coolant out of the reactor from any suitable source of heat. Coolant, sequentially passing through the catalyst layers and giving heat, in the same sequence heats the layers. As a result, when the temperature of the first layer reaches the desired value 200-280oC, the last layer is not hot. In such cases, either continue to pass the coolant through the layers up until the last layer is not heated to the desired value, or the reactor is in operation, and begin to apply the source of the reaction gas. In the first case, high energy consumption, the second in the initial period of reactor operation receive substandard formaldehyde with high methanol content.

As for the implementation of the inventive method of producing formaldehyde in the reactor should be performed additional ducts for the supply kislorodsodyerzhascikh gas, they can be sources of ionizing radiation portion of the hot fluid (air or inert gas to a temperature not lower than 200oC) submit to the reactor inlet and sequentially passed through all layers of the catalyst. Through the other, provided by the design of the reactor ducts for supplying oxygen-containing gas, or only through a portion of them, simultaneously serves the same carrier, which first passes through the nearest point of entry of the catalyst bed and then through the other layers.

The use of any additional ducts for quick and efficient heating of the reactor is optional. For example, you can use only the flue, before the last layer of the catalyst and simultaneously with the first heat with great speed other than the last layer. In this case, when the temperature of the first and the last layer 200-280oC reactor was transferred to the operating mode and begin to pass through it the source of the reaction gas. In the course of the oxidation reaction of methanol with oxygen generates heat and the rest of the catalyst layers located between the first and the last are heated to the operating temperature at high speed. In the last layer, oxidation of the remaining methanol oxygen therefore obtained at the outlet of the reactor formaldehyde in the initial pertama increase fire-fighting process for the preparation of formaldehyde while increasing the efficiency of the catalyst, the invention allows to reduce the time and energy costs preproduction phase to work.

Example 1. In the reactor with four successive adiabatic layers of oxide of iron-molybdenum catalyst serves 35000 nm3/h initial mixture with a temperature of 200oC, containing about 6. methanol, 6,5 about. oxygen and the rest nitrogen. The average temperature at the outlet of the layers 315-330oC. during the reaction the oxygen content in the mixture decreases and is output from the third layer 4,2 about. To prevent deactivation of the catalyst in the fourth layer is made positive pressure air between 3 and 4 layers in a volume ratio of the initial mixture:oxygen, equal (1:0,005). The consumption podavaemogo air is 875 nm3/PM

The process is stable, it eliminates the possibility of fire and explosion hazard conditions. The service life of the catalyst in all layers is not less than 3 years. The specific consumption rate of the catalyst is 0.05 kg per 1 ton of 37% formalin in the year.

The initial heating of the catalyst is accomplished by passing before the start of the air heated in the start-up heat exchanger superheated steam with a temperature of 2503/h passes through the first and sequentially through all other layers * b + (' b.'), and the second with a flow rate of 10000 nm3/h through the last layer of the catalyst, during heating of the first and fourth layers of catalyst to 200oC 8 h After reaching this temperature is up for the production of standard formalin.

Example 2. Similar to example 1, characterized in that the composition of the mixture to about 6. methanol, about 7. oxygen and the rest nitrogen. The oxygen content in the mixture at the outlet of the third layer 4,6 about. To prevent deactivation of the catalyst in the fourth layer is made positive pressure air in the middle of the fourth layer and the volumetric ratio of the initial mixture:oxygen, equal (1:0,005). The consumption podavaemogo air is 875 nm3/PM

Life, the specific consumption rate of the catalyst and the method of initial heating of the layers such as the one outlined in example 1.

Example 3. Similar to example 1, characterized in that the composition of the mixture to about 8. methanol, 6,5 about. oxygen and the rest nitrogen, and the temperature at the inlet into the first layer of catalyst in each of the subsequent layers is equal to 280oC. during the reaction the oxygen content in the mixture is reduced and sostav is positive pressure air between 2 and 3 layers in a volume ratio of the initial mixture:oxygen, equal (1:0,02). The consumption podavaemogo air is 3500 nm3/PM

The process is stable, it eliminates the possibility of fire and explosion hazard conditions. The service life of the catalyst in all layers is not less than 3 years. The specific consumption rate of the catalyst is equal 0,038 kg per 1 ton of 37% formalin in the year.

The initial heating of the catalyst is accomplished by passing before the start of the air heated in the start-up heat exchanger superheated steam, and then a gas burner to heat the air up to 350oC. the Hot air is supplied into the reactor by two parallel streams, the first of which, with the consumption of 20000 nm3/h passes through the first and sequentially through the remaining layers of the catalyst, and the second with a flow rate of 10000 nm3/h in two of the last layer of the catalyst. Heating the first and fourth layers of catalyst to 280oC 12 hours After reaching this temperature is up for the production of standard formalin.

Example 4. Similar to example 3, characterized in that the reactor has 5 consecutive layers, and the composition of the mixture to about 10. methanol, 6,5 about. oxygen and the rest nitrogen. The concentration of oxygen is otvoditsya positive pressure air three parallel streams between 2, 3, 4 and 5 layers in a volume ratio of the initial mixture:oxygen is equal to (1: 0.01) in each thread. The consumption podavaemogo air in one thread is 1750 nm3/PM

Life and the specific consumption rate of the catalyst such as the one outlined in example 3.

The initial heating of the catalyst is carried out analogously to example 6, except that the hot air is supplied into the reactor in four parallel streams: the first with a flow rate of 15000 nm3/h 1 and subsequent layers, the other three with a flow rate of 5000 nm3/h between 2, 3, 4 and 5 layers, respectively. The time needed to run the reactor with the production of standard formalin 12 PM

Example 5. Similar to example 3, characterized in that the reactor has 6 consecutive layers, and the composition of the mixture to about 12. methanol, about 7. oxygen and the rest nitrogen. The oxygen concentration in the mixture at the outlet of the third layer 4% To prevent deactivation of the catalyst in the fourth and sixth layers is positive pressure air three parallel streams between 3, 4 and 5 layers in a volume ratio of the initial mixture:oxygen, equal (1: 0,012) in each thread. The consumption podavaemogo air in one stream composition is of Zagreba layers such as the one outlined in example 3.

Example 6. Similar to example 3, characterized in that the reactor has 6 consecutive layers, and the composition of the mixture to about 12. methanol, and 4.5. oxygen and the rest nitrogen. The oxygen concentration in the mixture is reduced to 3.8% in the middle of the first layer. To prevent deactivation of the catalyst layers produced positive pressure air five concurrent threads: in the middle of the first layer in a volume ratio of the initial mixture:oxygen, equal (1: 0,015) (2625 nm3air h) and between 2, 3, 4, 5, and 6 layers in a volume ratio of the initial mixture: oxygen, equal to (1 0,01) in each thread. The consumption podavaemogo air in one thread is 1750 nm3/PM

Life and the specific consumption rate of the catalyst such as the one outlined in example 3.

The initial heating of the catalyst is carried out analogously to example 3, except that the hot air is supplied into the reactor in four parallel streams: the first with a flow rate of 15000 nm3/h 1 and subsequent layers, the other three with the cost of 5000 nm3/h between 3, 4, 5, and 6 layers, respectively. The time needed to run the reactor with the production of standard formalin 12 PM

Example 7 (the prototype). In the react serves 35000 nm3/h initial mixture containing about 7. methanol, about 7. oxygen and the rest nitrogen, with a temperature of 230oC. the Average temperature at the outlet of the layers 320-340oC. Between the layers through the intermediate heat exchangers is the removal of the reaction heat so that the temperature at the entrance of the subsequent layers were 230-240oC. At such parameters of the fourth layer of the catalyst does not provide the required conversion of methanol to formaldehyde because of the low oxygen content of the inlet layer (about 3,8.). When this occurs, the deactivation of the catalyst, which leads to overload the fourth layer every 3 months. Increasing the concentration of oxygen at the inlet of the reactor leads to a decrease in reliability due to the possibility of inflammable situation. Increasing the concentration of methanol at the inlet to the reactor is impractical for the same reason, and also because of increasing the degree of decontamination of the last layer. This limits the performance of the unit and increases operating costs. Consumption rates of the catalyst reaches 0.1 kg per tonne of 37% formalin in the year.

Example 8 (the prototype). The initial heating of the catalyst is carried out, under the rum with a flow rate of 16 t/h Heating the first layer of catalyst to the reaction start temperature of 220-240oC continues for 12 h, the temperature of the fourth layer is 120-130oC.

In the case of the introduction of the reactor in operation at this point in the next 8-10 hours there is incomplete conversion of methanol due to the low temperature on the last layer and, consequently, receive substandard formalin in the amount of 45-50 so

Example 9 (prototype). Similar to example 8, characterized in that the initial heating of the catalyst is carried out within 38 hours, until all the layers do not reach the temperature of the beginning of the reaction 220-240oC. This leads to increased consumption of superheated steam up to 576 so

1. The method of producing formaldehyde, including the transmission source of the reaction gas containing methanol and oxygen, sequentially through several layers containing a metal oxide catalyst at the inlet temperature of the reaction gas in each layer is 200 to 280C, characterized in that the starting reaction gas contains 6 to 12% methanol, 4.5 to 7% oxygen, the remainder an inert gas, and the process is carried out, supporting the partially reacted reaction gas oxygen concentration level 2 6,5% d, equal to 1:(0,005 0,03).

2. The method according to p. 1, characterized in that the catalyst layers before passing through the source of the reaction gas is pre-heated by passing through them inert to the catalyst gas temperature not lower than 200C, not less than two concurrent threads: the main of them served in the first and sequentially passed through all the subsequent layers of the catalyst, and more is served at or before any except the first layer of the catalyst, and then through all the other layers, the subsequent layer.

 

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