Continuous deep desulfurization process for carbon five raw material

Abstract

The present application relates to desulfurization process, specifically to a kind of carbon five raw material continuous deep desulfurization process.The present application includes the following steps:1) catalytic hydrogenation: using the subsection hydrogenation method of low temperature first and then high temperature, the diene in the carbon five after diene separation is hydrogenated saturated, and simultaneously, mercaptan is converted into high-boiling sulfide;2) desulfurization: remove active sulfur containing residual mercaptan with desulfurizer;3) rectification separation: after desulfurization, carbon five is separated by rectification column using rectification method to remove sulfur-containing components, and the sulfur content of carbon five obtained at the top of the column is less than 1mgS / L, and sulfur-containing heavy components are enriched in the column bottom.The present application can realize continuous desulfurization of carbon five raw material, and the removal precision is high, and the sulfur content in carbon five after desulfurization is less than 1mgS / L.

Description

TECHNICAL FIELD

[0001] The present application relates to a desulfurization process, in particular to a continuous deep desulfurization process for carbon five raw materials, which can remove sulfur compounds in carbon five to less than 1 mg S / L. BACKGROUND

[0002] A large amount of carbon five fraction (referred to as carbon five) is by-produced when naphtha is cracked to produce ethylene, and the yield is about 12% to 20% of the ethylene yield. The main components of carbon five include more than 20 kinds, which can be used to synthesize many high value-added products, and has become an important chemical resource. Diene in carbon five can be used as a raw material for synthetic rubber, and pentane extracted from carbon five can be used as a polyurethane blowing agent, etc. Carbon five after removing diene can be used as an important raw material for light hydrocarbon aromatization, which provides raw materials for downstream devices to produce high value-added products and improve the competitiveness of enterprises. Therefore, the comprehensive utilization of carbon five has become an important aspect for refining and chemical plants to improve economic benefits. However, carbon five raw materials usually contain 10 to 200 ppm of sulfide impurities, and common sulfide impurities include hydrogen sulfide, carbon disulfide, carbonyl sulfur, mercaptan, sulfide, disulfide and thiophene, etc. The presence of these sulfides not only causes catalyst poisoning and equipment corrosion in the processing of carbon five, but also has an adverse effect on the product quality and performance of cracked carbon five.

[0003] At present, there are many methods for removing sulfides in hydrocarbons in China, such as complex removal method, alcohol amine refining, physical adsorption method, chemical absorption method, hydrogenation refining and catalytic desulfurization, etc. Due to the complexity of C5 components, in addition to dienes, there are also mono-olefins, alkanes and other components, even after removing dienes, there are still a small amount of active conjugated dienes in C5, which causes certain limitations of the current desulfurization technology for C5 desulfurization. The current desulfurization technology such as hydrogenation desulfurization is an industrial method, but the desulfurization also saturates the olefins in C5 at the same time, which loses useful components, and the heat release is large when the olefins are saturated, which can intensify the saturation of the olefins, and make the catalyst bed fly and coking, so the catalytic hydrogenation method is not suitable for C5 desulfurization. Although some non-hydrogenation desulfurization technologies are currently developed, these technologies still have some shortcomings, such as CN201510076936.7 uses an amine-containing solution to react with C5 raw materials for 2 hours, and then separates the desulfurizer and C5, although this method does not change the composition of C5, but it has problems such as long reaction time, desulfurization liquid needs to be treated, etc., which is not suitable for large-scale industrial use; such as CN200810240549.2 uses adsorption method for desulfurization, the adsorbent used can remove almost all sulfur-containing compounds in C5 conjugated diene raw materials, and the sulfur content of the obtained C5 diene raw materials is less than 10 ppm, but the adsorbent has small sulfur capacity and cannot be regenerated, which leads to frequent replacement of the adsorbent and high operating cost; such as CN202010258017.2 uses a liquid membrane bed reactor, first oxidizes sulfides to sulfones, then extracts sulfones with water, then dehydrates, then complexes and distills, oxidizes mercaptans to high-boiling disulfides by using a complexing agent, and then removes these high-boiling sulfides by distillation to obtain refined C5, but this method has a complex process, complicated operation, large investment and high operating cost.

[0004] In summary, in the prior art, there are still some problems in the desulfurization of C5 raw materials, especially the continuous deep desulfurization process of C5 has not been reported. SUMMARY

[0005] The present application aims to provide a continuous deep desulfurization process for C5 raw materials to overcome the shortcomings of the prior art. The present application can realize continuous desulfurization of C5 raw materials, and has high removal precision, and the sulfur content in the desulfurized C5 is less than 1 mgS / L.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A continuous deep desulfurization process for C5 raw materials is provided, which comprises the following steps:

[0008] 1) Catalytic hydrogenation: a staged hydrogenation method of low temperature first and then high temperature is adopted to hydrogenate and saturate the residual dienes in C5 after separating dienes, and convert active sulfides such as mercaptans into high-boiling sulfides. Catalytic hydrogenation converts dienes into mono-olefins, and part of active sulfides such as mercaptans are added to dienes to generate high-boiling sulfide compounds;

[0009] 2) desulfurization: removing active sulfur including residual mercaptan with a desulfurizer;

[0010] 3) rectification separation: after desulfurization, C5 is separated by rectification tower to remove sulfur-containing components, and C5 with sulfur content less than 1 mg S / L is obtained at the top of the tower, and the sulfur-containing components are enriched in the tower bottom. After desulfurization by the desulfurization tower, the C5 system is distilled, and sulfides and a small amount of heavy components are left in the tower bottom, and C5 with sulfur content less than 1 mg S / L is obtained at the top of the tower.

[0011] According to the above scheme, in the step 1) of the segmented hydrogenation, the low-temperature hydrogenation temperature is the catalyst activation temperature, and the high-temperature hydrogenation temperature is 20-30°C higher than the catalyst activation temperature.

[0012] The present scheme adopts segmented catalytic hydrogenation, first low-temperature hydrogenation, and then hydrogenation at a higher temperature, so that the diene is converted into a relatively stable mono-olefin, and part of the active sulfides such as mercaptan is added to the diene to form a high-boiling-point sulfide compound, avoiding excessive bed temperature rise caused by excessive reaction heat in one-time hydrogenation, and preventing the generation of low-boiling-point sulfides due to high temperature, which further affects the desulfurization of the subsequent section.

[0013] According to the above scheme, the segmented hydrogenation is specifically as follows: C5 containing diene and hydrogen are mixed in proportion, heated and then fed into the upper section of the hydrogenation reactor, the inlet temperature of the upper section of the reactor is the catalyst activation temperature, the diene in C5 is hydrogenated to be saturated, and part of the active sulfides such as mercaptan and olefins are added to form sulfides, after the hydrogenation reaction in the upper section is completed, the C5 material is heated again for reaction in the lower section, and the inlet temperature of the lower section of the reactor is controlled to be 20-30°C higher than the inlet temperature of the upper section of the reactor.

[0014] According to the above scheme, the hydrogenation catalyst in the step 1) is a palladium-based, nickel-based, palladium-nickel-based or nickel-molybdenum-based catalyst.

[0015] According to the above scheme, the liquid space velocity of the hydrogenation catalyst used in the step 1) is 0.1-2.0 h -1 , the temperature is 40-180°C, the pressure is 0.5-3.0 MPag, the hydrogen / oil ratio is 1-10:1, and preferably 3-10:1.

[0016] According to the above scheme, the diene content after catalytic hydrogenation in the step 1) is ≤100 ppm.

[0017] According to the above scheme, the desulfurizer in the step 2) is a desulfurizer containing one or more components of copper, nickel, silver and zinc metal oxides, which removes mercaptan and other active sulfur in C5 under the conditions of pressure 1.0-3.0 MPag, liquid space velocity 0.3-3 h -1 , temperature 100-180°C, and the content of mercaptan after removal is less than 0.5 mg S / L.

[0018] According to the above scheme, the desulfurizer in the step 2) can be used to remove residual mercaptan, COS and hydrogen sulfide and other active sulfur.

[0019] According to the above scheme, the rectification column used in the step 3) is a packed column or a plate column, the carbon five after removal of active sulfur is fed from the lower part of the column, the carbon five with sulfur content less than 1 mg S / L is taken out from the top of the column, and the sulfur-containing heavy component is taken out from the bottom of the column.

[0020] According to the above scheme, the operating pressure of the rectification column in the step 3) is 0.5-3.0 MPag, the bottom temperature is 90-180 ℃, the top temperature is 60-120 ℃, and the top reflux ratio is 1-30:1.

[0021] According to the above scheme, the sulfur-containing heavy component enriched in the column bottom in the rectification separation process is subjected to catalytic hydrogenation, the sulfur-containing compounds in the sulfur-containing heavy component are converted into hydrogen sulfide, and the unsaturated hydrocarbons in the heavy component are saturated at the same time.

[0022] Further, the catalytic hydrogenation product is subjected to desulfurization in a desulfurization tank to remove hydrogen sulfide, and then is cooled and gas-liquid separated to obtain a column bottom heavy component saturated by hydrogenation and free of sulfur, and the unreacted hydrogen is recycled.

[0023] Further, the hydrogenation catalyst for catalytic hydrogenation desulfurization of the column bottom sulfur-containing heavy component is a cobalt-molybdenum or nickel-molybdenum hydrogenation catalyst, and the hydrogenation conditions are: pressure 1.0-3.0 MPag, reaction temperature 200-450 ℃, liquid space velocity 0.5-1.0 h-1, and hydrogen / oil ratio 100-300 (volume ratio). -1 Under the conditions, the sulfur-containing compounds in the column bottom sulfur-containing heavy component are converted into hydrogen sulfide, and the unsaturated hydrocarbons are saturated by hydrogenation at the same time. The column bottom heavy component can also be directly used as fuel or raw material without hydrogenation desulfurization.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. The carbon five after removal of diene is subjected to staged hydrogenation in the present application, on the one hand, the carbon five after removal of diene still contains 1-2% of diene, and this part of diene is easy to polymerize on the surface of the desulfurization catalyst, affecting the activity of the desulfurizer, and the diene hydrogenation can avoid the polymerization of diene on the surface of the desulfurization catalyst, affecting the activity of the desulfurizer, on the other hand, the staged hydrogenation makes the active sulfur such as mercaptan fully and controllably converted into high-boiling-point sulfide compounds, which are then removed by rectification, avoiding the active sulfur such as mercaptan in the carbon five to be desulfurized into low-boiling-point sulfide which is difficult to remove, achieving the purpose of greatly reducing the desulfurization reaction load, improving the desulfurization precision, and obtaining carbon five with ultra-low sulfur content, the sulfur content in the carbon five being less than 1 mg S / L; at the same time, the service life of the desulfurizer is prolonged, and the desulfurization cost is reduced.

[0026] 2. The process can realize continuous desulfurization of carbon five raw materials, is simple and reliable, the outlet sulfur content is controllable, the product quality is stable, and the shortcomings of frequent switching of desulfurization adsorbent and large fluctuation of outlet sulfur content in the adsorption method are avoided.

[0027] 3. The enriched sulfur compounds in the kettle and a small amount of heavy component mixture are hydrogenated by the catalyst to convert organic sulfur into hydrogen sulfide and remove it, and the heavy component is saturated, since most of the carbon five is taken out from the top of the rectifying tower, the result that the entire carbon five raw material is saturated in the traditional hydrogenation desulfurization is avoided, not only the investment and energy consumption are saved, but also the useful olefins in the carbon five raw material are greatly reserved, and the utilization efficiency of the carbon five is improved. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The figure is a process flow diagram in the embodiment of the present application; wherein: 1, hydrogenation reactor, 2, desulfurization reactor, 3, rectifying tower, 4, hydrogenation desulfurization reactor, 5, desulfurization tank, 6, gas-liquid separator, 7, tower top reflux tank, 8, heavy component storage tank. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0030] The carbon five composition after separating dienes in the example is shown in Table 1, and the form and content of sulfur are shown in Table 2.

[0031] Table 1. Carbon five composition after separating dienes in the example

[0032]

[0033] Table 2. Form and content of sulfur in carbon five after separating dienes in the example

[0034]

[0035] Example 1

[0036] A kind of carbon five raw material continuous deep desulfurization process is provided, as shown in Figure 1 , comprising the following steps:

[0037] 1) catalytic hydrogenation: the carbon five separated from dienes is mixed with hydrogen gas at a hydrogen oil ratio of 5:1 (volume ratio), then heated to 50 DEG C and entered into the upper section of hydrogenation reactor 1, with a liquid space velocity of 1 h -1, pressure 2.5 MPag, under the action of Pd / Al2O3 catalyst, diene in C5 is hydrogenated and saturated, and part of thiol and other active sulfides adduct with olefins to form sulfide; after the reaction in the upper section, the C5 material is heated to 70°C and continues to react in the lower section, and the content of diene in C5 is ≤100 ppm, and the content of thiol and other active sulfur is ≤2 mg S / L.

[0038] 2) Desulfurization: the hydrogenated C5 is heated to 140°C by a heater and sent to a desulfurization reactor 2, and under the condition of liquid space velocity 1 h -1 , pressure 2.5 MPag, the thiol and other active sulfides are removed by contacting with CuO-NiO / Al2O3 catalyst.

[0039] 3) Distillation separation: after removing the active sulfur, the C5 is sent to the lower part of a distillation column 3, the distillation column 3 is a packed column, Y450 stainless steel corrugated packing is installed in the column in four sections, the column bottom is heated by steam, the column bottom temperature is ~ 160°C, the column top temperature is ~ 133°C, the column top pressure is 2.45 MPag, the total sulfur in the column top C5 is ≤1 mg S / L, the analysis results are shown in Table 3 and Table 4, the column top C5 vapor is condensed by a cooler and then enters a column top reflux tank 7, part of the C5 in the reflux tank is taken out to go to the downstream, and part of the C5 is refluxed to the column top, and the reflux ratio is 5:1.

[0040] The total sulfur in the column bottom heavy component of the distillation column 3 is about 846 mg S / L, the column bottom heavy component is heated to 350°C and mixed with hydrogen, and then enters a hydrogen desulfurization reactor 4, under the condition of hydrogen to oil ratio 250:1, pressure 2.5 MPag, and liquid space velocity 0.5 h -1 , the hydrogen desulfurization catalyst is NiO-MoO / Al2O3, the hydrogen desulfurization product hydrogen sulfide is removed by a desulfurization tank 5 using zinc oxide desulfurizer, the desulfurization space velocity is 2000 h -1 , then the mixture is cooled and separated into gas and liquid in a gas-liquid separator 6, the unreacted hydrogen gas at the tank top is taken out to go to the hydrogenation cycle, and the liquid at the tank bottom is taken to a heavy component storage tank 8, and the sulfur content in the heavy component after hydrogen desulfurization is ≤5 mg S / L.

[0041] Table 3. Analysis results of C5 after desulfurization in Example 1

[0042]

[0043] Table 4. Formed sulfur and its content after desulfurization of C5 in Example 1

[0044]

[0045] Example 2

[0046] A continuous deep desulfurization process for C5 raw material is provided, which comprises the following steps:

[0047] 1) Catalytic hydrogenation: C5 dienes were mixed with hydrogen at a ratio of 10:1 (hydrogen to oil), then heated to 120°C and fed into the upper section of hydrogenation reactor 1 at a liquid space velocity of 0.8 h -1 , pressure 2.0 MPa, in the presence of a Ni-Mo / Al2O3 catalyst, dienes in C5 were saturated by hydrogenation, and part of the active sulfides such as mercaptans reacted with olefins to form sulfides; after the reaction in the upper section, the C5 material was heated to 150°C and continued to react in the lower section, and the content of dienes in C5 after the reaction was ≤100 ppm, and the content of active sulfides such as mercaptans was ≤2 mg S / L.

[0048] 2) Desulfurization: The hydrogenated C5 was heated to 160°C and fed into desulfurization reactor 2, and reacted with CuO-ZnO catalyst at a liquid space velocity of 1 h -1 , pressure 2.0 MPa, to remove active sulfides such as mercaptans.

[0049] 3) Distillation separation: After removing the active sulfides, the C5 was fed into the lower part of distillation column 3, which was a plate column with 21 float valve trays, and the C5 was fed into the 6th tray from the bottom, the column was heated by steam, the column temperature was ~ 150°C, the overhead temperature was ~ 124°C, the overhead pressure was 1.9 MPa, and the total sulfur in the overhead C5 was ≤1 mg S / L, the analysis results are shown in Tables 5 and 6, and the overhead C5 vapor was condensed by a cooler and then fed into overhead reflux tank 7, part of the C5 in the tank was taken out for downstream use, and part of the C5 was refluxed to the top of the column at a reflux ratio of 4:1.

[0050] The total sulfur in the heavy components in the column was about 730 mg S / L, the heavy components were heated to 380°C and mixed with hydrogen, and then fed into hydrogenation desulfurization reactor 4, the hydrogenation desulfurization catalyst was CoO-MoO / Al2O3, the hydrogen to oil ratio was 150:1, the pressure was 1.8 MPa, and the liquid space velocity was 0.8 h -1 , under the conditions of hydrogenation desulfurization, the hydrogenation product was fed into desulfurization tank 5, hydrogen sulfide generated was removed by zinc oxide desulfurizer, the desulfurization space velocity was 2000 h -1 , then cooled and separated into gas and liquid in gas-liquid separator 6, the unreacted hydrogen gas at the top of the tank was taken out for hydrogenation cycle, and the liquid at the bottom of the tank was taken out for heavy component storage tank 8, and the sulfur content in the heavy components after hydrogenation desulfurization was ≤3 mg S / L.

[0051] Table 5. Analysis results of C5 after desulfurization in Example 2

[0052]

[0053] Table 6. Form of sulfur and its content after desulfurization of C5 in Example 2

[0054]

[0055] From the carbon five result analysis data before and after desulfurization in the above examples, it can be seen that after the desulfurization by the method, the dienes in the carbon five raw material are basically saturated, the content of other components is basically unchanged, and the carbon five does not contain difficult-to-remove sulfides such as thiophene, but only contains a small amount of low-boiling-point mercaptans and sulfides, the total sulfur is less than 1 mg S / L, and the carbon five raw material with ultra-low sulfur content is obtained.

[0056] It should be understood that, for those skilled in the art, improvements or changes can be made according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A continuous deep desulfurization process for C5 feedstock, characterized in that, Includes the following steps: 1) Catalytic hydrogenation: A staged hydrogenation method, first at low temperature and then at high temperature, is used to hydrogenate and saturate the remaining dienes in the C5 carbon-5 carbon-16 carbon-5 carbon-5 carbon-5 carbon-5 carbon-6 ... 2) Desulfurization: Removing active sulfur containing residual mercaptans using a desulfurizing agent; the desulfurizing agent is a desulfurizing agent containing one or more components of metal oxides of copper, nickel, silver, and zinc; the mercaptan content after removal is less than 0.5 mgS / L; 3) Distillation separation: After desulfurization, C5 is separated and sulfur-containing components are removed by distillation in a distillation column. C5 with a sulfur content of less than 1 mgS / L is obtained at the top of the column, and the heavy sulfur-containing components are enriched in the bottom of the column.

2. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, The segmented hydrogenation process is as follows: the C5 fraction of the separated diene is mixed with hydrogen in a certain proportion and heated before entering the upper section of the hydrogenation reactor. The inlet temperature of the upper section of the reactor is the catalyst activation temperature. The diene in the C5 fraction is hydrogenated to saturation, and at the same time, some thiols undergo an addition reaction with the olefins to form sulfides. After the hydrogenation reaction in the upper section is completed, the C5 fraction is heated again and continues to react in the lower section. The inlet temperature of the lower section of the reactor is controlled to be 20-30°C higher than the inlet temperature of the upper section of the reactor.

3. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, In step 1), the liquid space velocity used for the hydrogenation catalyst is 0.1~2.0 h⁻¹. -1 Operating temperature 40~180℃, pressure 0.5~3.0MPag, hydrogen-to-oil ratio 1~10:

1.

4. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, In step 2), the pressure is 1.0~3.0 MPa and the liquid hourly space velocity is 0.3~3 h⁻¹. -1 Active sulfur in C5 is removed under conditions of 100~180℃.

5. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, The distillation column used in step 3) is a packed column or a plate column. The C5 after the active sulfur is removed is fed from the lower part of the column, and the C5 with a sulfur content of less than 1 mgS / L is collected from the top of the column, and the sulfur-containing heavy components are collected from the bottom of the column.

6. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, In step 3), the distillation column operates at a pressure of 0.5~3.0 MPa, a bottom temperature of 90~180℃, a top temperature of 60~120℃, and a top reflux ratio of 1~30:

1.

7. The continuous deep desulfurization process for C5 feedstock according to claim 1, characterized in that, In step 3), the sulfur-containing heavy components enriched in the distillation column bottom during the distillation separation process are subjected to catalytic hydrogenation, and the sulfur-containing compounds in the sulfur-containing heavy components are converted into hydrogen sulfide, while the unsaturated hydrocarbons in the sulfur-containing heavy components are saturated.

8. The continuous deep desulfurization process for C5 feedstock according to claim 7, characterized in that, The hydrogenation catalyst used for the catalytic hydrodesulfurization of sulfur-containing heavy components in the reboiler is a cobalt-molybdenum or nickel-molybdenum based hydrogenation catalyst; hydrogenation conditions: pressure 1.0~3.0 MPa, reaction temperature 200~450℃, liquid hourly space velocity 0.5~1.0 h⁻¹ -1 With a hydrogen-to-oil ratio of 100 to 300, under these conditions, sulfur-containing compounds in heavy sulfur-containing components are converted into hydrogen sulfide, while unsaturated hydrocarbons are hydrogenated to saturation. The catalytic hydrogenation product is sent to a desulfurization tank to remove hydrogen sulfide, then cooled and separated into gas and liquid components to obtain hydrogenated, sulfur-free heavy components in the bottom of the tower. Unreacted hydrogen is recycled.

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