CN1336358A

CN1336358A - Carbonyl synthetic gas preparing process through vapor transformation of hydrocarbon and CO2

Info

Publication number: CN1336358A
Application number: CN 00111252
Authority: CN
Inventors: 郝树仁; 程玉春; 李春禄; 梁卫忠; 尹长学; 胡玉才
Original assignee: Qilu Petrochemical Co of Sinopec
Current assignee: China Petroleum and Chemical Corp
Priority date: 2000-08-01
Filing date: 2000-08-01
Publication date: 2002-02-20
Anticipated expiration: 2020-08-01
Also published as: CN1167606C

Abstract

The present invention relates to method of preparing carbonyl synthetic gas through conversion of hydrocarbon vapour, it includes: light oil, liquified gas or refinery gas and steam and carbon dioxide are set on to reaction bed layer containing hydrocarbon vapour conversion catalyst to proceed hydrocarbon vapour conversion reaction and one step produce reforming gas containing carbon monoxide, carbon dioxide, hydrogen gas and small amount methane, then separate out carbonyl synthetic gas composed of carbon monoxide and hydrogen gas, the residual gas is recycled and used as raw material, thereby. It makes carbon in raw material hydrocarbon completely convert into carbon monoxide. Advantages include: one step reaction, simple technology, high carbon monoxide content in reforming gas.

Description

Method for preparing oxo-synthesis gas by steam conversion of hydrocarbon and carbon dioxide

The invention relates to a method for preparing oxo-synthesis gas by a hydrocarbon steam conversion method, in particular to a process method for preparing oxo-synthesis gas with high carbon monoxide content by one-step conversion reaction of heavy hydrocarbons, carbon dioxide and water vapor.

The oxo synthesis plays a very important role in the field of petrochemical and organic synthesis, such as the synthesis of alcohols, aldehydes, ketones, anhydrides, acid chlorides, lactonesQuinones, etc. and to prepare solvents, plasticizers, etc. The composition of the oxo gas is CO and H₂According to different applications H₂The ratio of/CO is 1.0-3.0. At present, reformed gas with relatively high CO content can be obtained by steam reforming reaction using light hydrocarbon raw material, such as light hydrocarbon, water steam and CO in U.S. Pat. No. 4,894,394₂To give H₂The CO is 2.8-4.5, and the methanol is continuously synthesized by using the converted gas. At present, in the reformed gas generated in the conventional steam reforming of hydrocarbon feedstock, H₂The ratio of/CO is generally between 4.0 and 5.0. Such a high H₂If the gas with the/CO ratio is used directly as oxo gas, the CO content is insufficient, while H₂The content is excessive. Thus, when syngas is produced by a hydrocarbon steam reforming process, the CO content of the reformed gas must be increased.

The reaction mechanism for steam reforming of hydrocarbons is as follows:

(1)

ΔH＝-206KJ/mol (2)

ΔH＝+247KJ/mol (3)

ΔH＝-41KJ/mol (4)the reaction (1) is a strong endothermic reaction with increased volume, and the reaction is favorably carried out rightward and is favorably generated by reducing the pressure and increasing the temperature; the reaction (2) is an exothermic reaction with reduced volume, and increasing the temperature, decreasing the pressure and increasing the partial pressure of water will cause the reaction (2) to move to the left, which is beneficial to the generation of CO; reaction (3) is an endothermic reaction with increased volume, increased temperature, reduced pressure and increased CO₂Partial pressure, which will cause reaction (3) to move to the right, favoring the generation of CO; the reaction (4) is an exothermic reaction with unchanged volume, and the reaction (4) moves leftwards by increasing the temperature and reducing the water partial pressure, so that CO is generated. By analyzing the above mechanism of the hydrocarbon steam reforming reactionTo know that: increasing reaction temperature, reducing reaction pressure, reducing water-carbon ratio and increasing CO₂The concentration is an important means for increasing the content of CO in the converted gas.

At present, the low H is prepared by utilizing heavy hydrocarbon raw materials such as light oil and the like₂For the oxo gas/CO ratio, light oil or the like is pre-converted to convert it into a methane-rich gas, and then CH is added₄＋CO₂To produce oxo gas.

The invention aims to provide a process method for preparing oxo-synthesis gas by one-step conversion of heavy hydrocarbons such as light oil.

In the present invention, heavy hydrocarbons such as light oil, liquefied gas, or refinery gas, and steam, CO₂Mixing, introducing into a reformer containing a steam reforming catalyst, and converting in one step to obtain a product containing CO and CO₂、H₂And a small amount of methane; separating the converted gas to obtain carbonyl synthesis gas, the main component of the residual gas is CO₂Also contains small amounts of unconverted methane, and small amounts of CO and H which are not completely separated off₂(ii) a After separation of the oxo gas, with CO₂The residual gas mainly circulates back to the inlet and is used as raw material CO₂Continuously participate in the steam conversion reaction of the hydrocarbon, thereby achieving the purpose that carbon in the raw material hydrocarbon is basically completely converted into CO, and the whole conversion reaction process can be free of CO₂And (5) discharging.

In the gas separation, a PSA (pressure swing adsorption) method, a cryogenic method, a liquid phase method, or the like can be used.

When hydrocarbons are steam converted and completely converted to CO, the total package reaction is:

(5) for heavy hydrocarbons such as light oil, n is about 2.2, and 1 + n/2 is 2.1, so that when the hydrocarbon is completely converted to CO, H is present₂2.1: 1 of/CO; and for methane (CH)₄) In other words, H when it is completely converted to CO₂and/CO is 3: 1. Thus, the production of carbonyl from heavy hydrocarbons such as light oilThe synthesis gas is more beneficial to improving the concentration of CO in the product gas.

Water to carbon ratio (H)₂O/C) is an important parameter which influences the conversion process according to the invention. The water-carbon ratio is reduced, the content of carbon monoxide in the converted gas is increased, and H₂The ratio/CO is reduced, which is beneficial to the production of the oxo-gas. However, as the water to carbon ratio decreases, the propensity for carbon deposition on the conversion catalyst increases. In the present invention, since the carbon dioxide in the reformed gas is separated and recycled to the raw material inlet, the carbon dioxide can play the same role as water in terms of carbon resistance and carbon elimination to some extent (compare the following reactions):

(6)

(7) thus, the circulation of carbon dioxide in the present invention is also advantageous in preventing the carbon deposition of the catalyst, so that a smaller water-carbon ratio can be used, for example, the water-carbon ratio can be reduced to about 1.5. Generally, when the process of the present invention is used to prepare oxo gas, the water-to-carbon ratio can be selected within the range of 1.5 to 3.5, and the preferred range is 2.0 to 3.0.

The choice of conversion catalyst is also important to the process of the present invention. Besides the catalytic active metal element and the anti-carbon component, the catalyst also contains a component capable of catalyzingReaction of And in addition, selecting proper catalyst carrier. Wherein the catalytically active metal element may be nickel and/or cobalt, preferably nickel; the anti-carbon composition may be a compound or mixture of alkali and/or alkaline earth metals, preferably a potassium compound; the support of the catalyst may be a refractory metal oxide or a mixture thereof, preferably calcium aluminate cement and/or iron cement; catalysis The components of (A) can be selected from iron and/or rare earth elements and the like.

Although the higher the reaction temperature, the higher the concentration of carbon monoxide in the product gas from the viewpoint of thermodynamic equilibrium, the choice of the reaction temperature is limited by various factors such as the heat resistance of the reformer and the catalyst used. If the reformer tube has good heat resistance, the reaction temperature can be increased accordingly. In the conversion reaction of the invention, the outlet temperature is generally selected within the range of 800-950 ℃, which is beneficial to improving the concentration of carbon monoxide and ensuring that the conversion furnace tube and the catalyst have longer service life.

In the present invention, the change in the space velocity of the feedstock has little effect on the composition of the product gas, especially when a conversion catalyst with good performance is selected. If the hydrocarbon feedstock used is a light oil, the space velocity of the carbon in the light oil can be selected within a relatively wide range depending on the actual conditions of the process and other conditions, and is generally controlled to be 300h^-1～3000h^-1Within the range of (1).

The reduction of the reformer pressure is not only beneficial to increase the content of carbon monoxide in the reformed gas, but also to increase the content of hydrogen in the reformed gas, but also to increase the content of H₂The ratio of/CO does not vary much. However, the selection of a lower pressure, where permitted, allows to reduce the residual methane content of the reformed gas, making the single-pass reforming reaction more complete and advantageous for the production of oxo gas. In industrial applications, the pressure is selected in relation to the pressure rating of the system before and after the conversion process, and is generally selected between 1.0MPa and 4.0 MPa.

In theprocess for producing oxo gas according to the present invention, heavy hydrocarbons such as light oil are used as raw materials, and carbon in the raw material hydrocarbons can be completely converted into CO, so that H in the oxo gas finally obtained₂The ratio of the carbon monoxide to the carbon monoxide is lower than that of the process adopting light hydrocarbon raw materials such as methane and the like, and the ratio of the carbon monoxide to the carbon monoxide can be generally between 2.0 and 3.0; of course, if a certain amount of hydrogen is contained or added in the starting hydrocarbon, the H of the oxo gas produced is₂The ratio of/CO will be correspondingly higher, and when the amount of hydrogen is large, H₂The ratio/CO may be higher than 3.0, but the feed is fed with a quantity of hydrogen such that H is produced₂The ratio/CO is higher than 3.0, which still falls within the scope of protection of the present invention.

In the conventional light oil steam reforming process, the CO content in the reformed gas is oneGenerally about 15 percent; according to the process of the invention, CO is generated₂The carbon in the light oil can be completely converted into the form of carbon monoxide, the content of CO in the converted gas can reach about 30 percent, and the conversion reaction is completed in one step, so that the process is relatively simple.

The present invention is further illustrated by the following examples, but the scope of the present invention should not be construed as being limited to the following examples.

Example 1

Filling 10-20 meshes/inch of small catalyst particles in a conversion reaction tube, wherein about 50% of Z405G (volume ratio) is filled in the lower part of the reaction tube, and about 50% of Z409 (volume ratio) is filled in the upperpart of the reaction tube; a thermocouple tube is inserted into the reaction tube, and the thermocouple can move up and down in the thermocouple tube so as to measure the temperature of different positions of the reaction tube; then the catalyst is reduced and heated up, and the temperature is raised under the nitrogen atmosphere, hydrogen and water (H) for reduction₂O/H₂3.0), inlet temperature about 500 deg.c, outlet temperature about 800 deg.c, hydrogen space velocity 1000h^-1The time is about 8 hours.

After the completion of the catalyst reduction, the test was carried out. Desalted water enters a vaporizer to be vaporized through a metering pump, naphtha is mixed with water vapor, carbon dioxide and hydrogen through the metering pump, enters a superheater to be overheated and heated, and then enters a conversion reaction tube to finish conversion reaction. The reformed gas is cooled, chromatographed, and separated by PSA to give a oxo gas, and the remaining gas, which is predominantly carbon dioxide and contains small amounts of methane, carbon monoxide and hydrogen, is recycled to the feed inlet and mixed with naphtha, steam and hydrogen. The whole reaction process simulates the operation condition of an industrial device, and the bed layer temperature is heated and controlled by four sections of furnace wires outside the reaction tube so as to adjust the inlet, the outlet and the bed layer temperature and ensure the reaction heat supply. The pressure is controlled by a pressure controller, the liquid feeding is controlled and regulated by a micro pump and an electronic balance, the gas feeding is controlled by a gas mass flowmeter, and the chromatographic analysis adopts an external standard method.

Control system pressure of2.0Mpa, 480 ℃ of inlet temperature, 2.5 of water-carbon ratio and 2320h of space velocity of medium carbon in naphtha^-1(ii) a Maintenance ofimported CO₂And outlet CO₂The balance of (a) to convert all of the carbon in the naphtha to the CO product form. The composition of the converted gas was measured at different exit temperatures and the results are shown in table 1.

TABLE 1

Outlet temperature	CO₂Airspeed	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO
Outlet temperature	CO₂Airspeed	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO	890℃	1458h^-1	24.2	57.6	16.6	1.65	2.38
860℃	1782h^-1	23.6	54.6	19.6	2.30	2.31	890℃	1458h^-1	24.2	57.6	16.6	1.65	2.38
860℃	1782h^-1	23.6	54.6	19.6	2.30	2.31	830℃	1863h^-1	22.2	52.0	21.7	4.08	2.34
800℃	1944h^-1	20.2	50.2	24.0	5.58	2.48	830℃	1863h^-1	22.2	52.0	21.7	4.08	2.34

Note: the percentages of the components in the table are volume percentages

Example 2 control: h₂2.5O/C, 480 ℃ inlet temperature, 860 ℃ outlet temperature, naphthaThe space velocity of medium carbon is 2320h^-1，CO₂Space velocity of 1782h^-1The system pressure is shown in Table 2, and the rest of the conditions are the same as in example 1. The contents of the components in the reformed gas were measured and the results are shown in Table 2.

TABLE 2

Pressure, MPa	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO
Pressure, MPa	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO	3.0	22.9	52.7	20.1	4.33	2.30
2.5	23.5	53.4	19.7	3.43	2.27	3.0	22.9	52.7	20.1	4.33	2.30
2.5	23.5	53.4	19.7	3.43	2.27	2.0	23.6	54.5	19.6	2.30	2.31
1.5	24.2	55.0	19.5	1.33	2.27	2.0	23.6	54.5	19.6	2.30	2.31

Note: the percentage contents of all the components of the surface A are volume percentage contents

It can be seen from the data in table 2 that the pressure drop allows the residual methane content in the reformed gas to be reduced and the reforming process to proceed more completely.

Example 3

Controlling: the system pressure is 2.0MPa, the inlet temperature is 480 ℃, the outlet temperature is 860 ℃, and the space velocity of carbon in naphtha is 2320h^-1Water to carbon ratio and CO₂The space velocity is shown in Table 3, and the rest of the conditions are the same as in example 1. The contents of the components in the reformed gas were measured and the results are shown in Table 3.

TABLE 3

H₂O/C	CO₂Airspeed	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO
H₂O/C	CO₂Airspeed	CO.％	H₂，％	CO₂，％	CH₄，％	H₂/CO	3.0	1863h^-1	21.7	55.9	20.7	1.66	2.58
2.5	1782h^-1	23.6	54.5	19.6	2.30	2.31	3.0	1863h^-1	21.7	55.9	20.7	1.66	2.58
2.5	1782h^-1	23.6	54.5	19.6	2.30	2.31	2.0	1296h^-1	24.5	55.5	16.4	3.60	2.27
1.5	1053h^-1	25.8	54.7	14.1	5.40	2.12	2.0	1296h^-1	24.5	55.5	16.4	3.60	2.27

Note: the percentages of the components in the table are volume percentages

Claims

1. A process for the preparation of oxo-gas by steam reforming of hydrocarbons, comprising:

(1) feeding light oil, liquefied gas or refinery gas, water vapor and carbon dioxide into a reaction bed layer filled with a hydrocarbon vapor conversion catalyst to perform a hydrocarbon vapor conversion reaction to generate converted gas containing carbon monoxide, carbon dioxide, hydrogen and a small amount of methane in one step;

(2) separating the converted gas obtained in the step (1) to separate out oxo gas consisting of carbon monoxide and hydrogen, wherein the rest gas is mainly carbon dioxide and contains a small amount of methane, carbon monoxide and hydrogen, and the rest gas is completely recycled to the step (1) to be used as a raw material for hydrocarbon steam conversion reaction, so that carbon in the raw material hydrocarbon is basically completely converted into carbon monoxide.

2. The process of claim 1, wherein the feed in step (1) has a water to carbon ratio of H₂The O/C is controlled within the range of 1.5 to 3.5.

3. The process of claim 2, wherein the feed in step (1) has a water to carbon ratio of H₂The O/C is controlled within the range of 2.0-3.0.

4. The process according to claim 2 or 3, wherein the steam reforming catalyst used in step (1) comprises the following components:

a. a metal element having catalytic activity for steam reforming reaction;

b. alkali metal and/or alkaline earth metal compounds as anti-carbon components;

c. refractory metal oxides or mixtures thereof as catalyst supports;

d. iron and/or rare earth elements.

5. The process according to claim 4, wherein the steam reforming catalyst used in step (1) comprises the following components:

a. the metallic nickel is used as a catalytic active metal element for steam conversion;

b. potassium compound as the component for resisting carbon deposition;

c. calcium aluminate cement and/or iron cement are/is used as a carrier of the catalyst;

d. iron and/or rare earth elements.

6. The process according to claim 5, characterized in that the oxo gas produced has H₂The ratio of/CO is between 2.0 and 3.0.

7. The process according to claim 6, wherein the steam reforming in the step (1) is carried out while controlling the outlet temperature of the steam reforming reaction bed to be in the range of 800 to 950 ℃.

8. The process according to claim 7, wherein the space velocity of carbon in the hydrocarbon feedstock during the steam reforming in step (1) is controlled to 300h^-1～3000h^-1In the meantime.

9. The process according to claim 8, wherein the pressure in the steam reforming reaction system is controlled to be 1.0MPa to 4.0MPa when the steam reforming is carried out in the step (1).