The method of producing formaldehyde

 

(57) Abstract:

Usage: in the chemical industry. The inventive product is formaldehyde. Reagent 1: natural gas. Reagent 2: air. Reaction conditions: temperature of 300 - 400oC and a pressure of 3 to 10 MPa, natural gas is mixed with air from getting gas mixture containing 1 - 4% vol. oxygen, which is fed into the reactor, and then optionally introducing the air at the site of maximum heating. 9 table.

The invention relates to organic chemistry, in particular to methods for formaldehyde, and can be used in the chemical industry.

Known methods for producing formaldehyde (FA) as by direct partial oxidation of methane, and by the catalytic oxidative dehydrogenation of methanol oxygen (1). Both methods have disadvantages. Getting FA by catalytic oxidative dehydrogenation of methanol multistage process in which the feedstock (natural gas) sequentially converted into synthesis gas, then in methanol and then in FA. Despite the high selectivity of individual stages of the process requires very high energy costs and complex hardware product is methane conversion in FA.

The closest technical solution is the method of obtaining the FA and the simultaneous achievement of methanol (2), consisting in a partial air oxidation of methane or mixtures thereof with nitrogen at 300-600aboutC and a pressure of 5-200 bar followed by cooling the reaction mixture and separation of target products.

However, the known method (2) has a drawback: low output F (just at the level of 10-19%) due to the low degree of methane conversion.

The aim of the invention is to provide a method for obtaining the FA, which allows to increase the output of F (unreacted methane).

The solution of this problem is achieved by the proposed method of obtaining the FA, including oxidation of natural gas with air at a temperature of 300-400aboutC and a pressure of 3-10 MPa, followed by cooling the reaction mixture and separation of the target product, in which natural gas is mixed with air from getting gas mixture containing about 1-4. oxygen and fed into the reactor, and then optionally introducing the air at the site of the reactor with a maximum heat coming out of the reactor the gaseous mixture to cool and separate the liquid product is heated to 100-120aboutWith and subjected to oxidative dehydrogenation in at the showed the increased oxygen content in the reaction gas mixture leads to an increase in the degree of methane conversion, not at the same time sharply decreases the selectivity of the process output F and methanol drops. The distributed supply of oxygen along the reactor allows to increase the degree of conversion without significant loss of selectivity of the formation of the desired products. But even under optimal conditions, the main oxidation product is methanol. Known methods for catalytic oxidative dehydrogenation of pure methane in FA (1). However, the liquid product methane oxidation in the proposed process is a complex mixture of alcohols, aldehydes, organic acids and water. Given that the main component of this product (about 50%) is methanol, its translation in F will increase the output F in the process more than three times. As was shown by experiments, the catalytic oxidative dehydrogenation of liquid products obtained in the proposed process by oxidation of methane (without separation of methanol) allows to increase the output F in the process.

P R I m e R 1. Natural gas is heated to 350aboutWith the pressure of 10 MPa at a flow rate of 760 nm3/h served in the reaction is t air air consumption 80 nm3/h oxygen Concentration in gas mixture 2. On the site of the reactor with a maximum heating (temperature in the reactor is controlled by thermocouples) impose additional air with the same speed (80 nm3/h). Coming out of the reactor the gaseous reaction mixture is cooled in the heat exchanger and separating the liquid product in the separator. The obtained liquid product has the composition given in table.1.

The liquid product of the specified composition is heated to 120aboutC and sent to the catalytic reactor with a silver catalyst, after completion of the reaction, which occurs with heating, the reaction mixture was cooled in the refrigerator.

The composition of the liquid reaction product after the catalytic dehydrogenation is shown in table.2.

P R I m m e R 2 (comparative). The process is carried out analogously to example 1, but the entire air (air flow 160 nm3/h) is injected in one piece through the mixer.

The composition of the liquid product obtained after oxidation of methane is given in table.3.

The composition of the liquid product after the catalytic dehydrogenation is shown in table.4.

P R I m e R 3. The process is carried out analogously to example 1 but at a temperature of 400aboutC and a pressure of 3 MPa.aboutC). The data are given in table.6.

P R I m e R 4. The process is carried out analogously to example 1, but if 300aboutC. the Composition of the liquid product obtained after oxidation of methane is given in table. 7.

P R I m e R 5. The process is carried out analogously to example 1, but the concentration of oxygen in the gas mixture was about 4. The composition of the liquid product obtained after oxidation of methane is given in table.8.

P R I m e R 6. The process is carried out analogously to example 1, but the concentration of oxygen in the gas mixture was about 1. The composition of the liquid product obtained after oxidation of methane is given in table.9.

The METHOD of producing FORMALDEHYDE, including oxidation of natural gas with air at a temperature of 300 - 400oC and a pressure of 3 to 10 MPa, followed by cooling the reaction mixture and separation of the target product, wherein the natural gas is mixed with air from getting gas mixture containing 1 - 4% vol. oxygen, which is fed into the reactor, and then optionally introducing the air at the site of the reactor with a maximum heat coming out of the reactor a gaseous mixture keaveney in the presence of a silver catalyst.

 

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