Process for removing carbonyl compound impurities from hydrocarbon streams

Abstract

The present disclosure relates to a method for removing carbonyl compound impurities from mixed hydrocarbon streams derived from naphtha and gas stream cracking processes. The method of the present disclosure is simple, economical and environmentally friendly. The method of the present disclosure is capable of efficiently removing higher content of carbonyl compound impurities. The method of the present disclosure is easily scalable to production scale to meet commercial application needs.

Description

[0001] field

[0002] This disclosure relates to a method for removing carbonyl compound impurities from a hydrocarbon stream.

[0003] definition

[0004] As used in this disclosure, the following terms are generally intended to have the meanings specified below, unless otherwise specified in the context in which they are used.

[0005] Mixed C4 hydrocarbon stream: The term “mixed C4 hydrocarbon stream” refers to a C4 hydrocarbon stream obtained from a naphtha cracker, gas-steam cracker, or gas-naphtha dual cracker, which consists of C4 hydrocarbons (e.g., butadiene) and other hydrocarbons.

[0006] Condensate: The term "condensate" refers to water available on-site, which is produced under high-pressure and medium-pressure steam conditions. Condensate is often used to make processes more economical.

[0007] Carbonyl compound scrubbing tower: The term "carbonyl compound scrubbing tower," also known as "scrubber," refers to a tower typically used to remove carbonyl compound impurities from a mixed C4 stream.

[0008] background

[0009] The following background information is related to this disclosure, but is not necessarily prior art.

[0010] Butadiene is an important industrial chemical used in the manufacture of synthetic rubber, latex paint, nylon, and other products. It is also a commonly used chemical in Diels-Alder condensation processes to synthesize a variety of different compounds. Butadiene is typically recovered from a mixture of C4 hydrocarbon streams obtained from naphtha or gas vapor crackers. During butadiene recovery, trace amounts of carbonyl compound impurities (such as acetaldehyde and acetone) are found. These impurities can adversely affect subsequent processes using butadiene as a feedstock. Therefore, removing these carbonyl compound impurities from the C4 hydrocarbon stream mixture is crucial.

[0011] Traditionally, organic compounds containing carbonyl groups are removed from mixed C4 hydrocarbon streams using "washing solutions" such as hydrazine hydrate scrubbing solutions. For this purpose, carbonyl compound scrubbing towers are used in butadiene (BD) plants to remove carbonyl compound impurities. However, hydrazine hydrate scrubbing solutions are not effective at removing all carbonyl compound impurities present in mixed C4 hydrocarbon streams, nor can they meet the desired specification requirement of aldehyde content below 10 ppm in mixed C4 hydrocarbon streams.

[0012] Furthermore, the mixed C4 hydrocarbon stream contains carbonyl compound impurities, such as acetaldehyde, acetone, and other carbonyl compounds, which can be effectively removed by treatment with alkali metal bisulfites. However, due to the acidity of alkali metal bisulfites, direct addition to the tower may cause corrosion.

[0013] The composition of the mixed C4 hydrocarbon stream varies depending on the process in which the equipment is operated, i.e., from a gas pyrolyte, naphtha pyrolyte, or gas-naphtha dual pyrolyte process. The gas pyrolyte product stream has a lower percentage of C4 hydrocarbons compared to the naphtha pyrolyte product stream. Therefore, the naphtha pyrolyte product stream is preferred for butadiene production because it contains a significant amount of C4 hydrocarbons in addition to compounds such as ethylene, propylene, and other hydrocarbons. Furthermore, depending on process optimization, a mixture of the naphtha pyrolyte product stream and the gas pyrolyte product stream can also be processed to produce a mixed C4 hydrocarbon stream.

[0014] The product stream from the gas pyrolyzer has a high carbonyl compound feed content (>350 ppm). Furthermore, when the product stream from the gas pyrolyzer is mixed with the product stream from the gas-naphtha dual pyrolyzer, the resulting mixed C4 hydrocarbon stream can have a carbonyl compound content exceeding 500 ppm. In this case, the removal efficiency of carbonyl compounds from the mixed C4 hydrocarbon stream in the scrubbing tower cannot meet the product specification requirements. For the butadiene process, it is desirable that the carbonyl compound impurity content in the product C4 hydrocarbon stream be <10 ppm.

[0015] Furthermore, an increased content of carbonyl compound impurities in the mixed C4 hydrocarbon stream typically increases the consumption of fresh condensate in the carbonyl compound scrubbing tower. This increased consumption of fresh condensate can further corrode the processing unit.

[0016] Therefore, there is a need for an efficient process to remove carbonyl compound impurities from mixed C4 hydrocarbon streams to mitigate the drawbacks described above, or at least provide a useful alternative.

[0017] Target

[0018] Some of the objectives of this disclosure are as follows (at least one embodiment of this document satisfies these objectives).

[0019] One object of this disclosure is to alleviate one or more of the problems in the background, or at least to provide a useful alternative.

[0020] Another object of this disclosure is to provide a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream.

[0021] Another object of this disclosure is to provide a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream containing a large amount of carbonyl compound impurities.

[0022] Another object of this disclosure is to provide an efficient method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream.

[0023] Other objects and advantages of this disclosure will become more apparent from the following description, but such description is not intended to limit the scope of this disclosure. Summary of the Invention

[0024] This disclosure relates to a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream. The method includes: mixing a mixed C4 hydrocarbon stream containing carbonyl compound impurities with a predetermined amount of an aqueous washing solution with a pH value in the range of 6.5 to 7.0 in a carbonyl compound washing tower maintained at a predetermined temperature and pressure to obtain an aqueous phase and an organic phase, wherein the aqueous phase contains carbonyl compound impurities in the form of water-soluble reaction products, and the organic phase contains a C4 hydrocarbon stream with reduced or no carbonyl compound impurities.

[0025] According to embodiments of this disclosure, the carbonyl compound impurities include acetaldehyde and acetone.

[0026] According to embodiments of this disclosure, the mixed C4 hydrocarbon stream is obtained from at least one of the following: naphtha cracking process, gas-gas cracking process, and gas-naphtha dual cracking process.

[0027] According to embodiments of this disclosure, the aqueous washing solution is prepared by using at least one selected from distilled water and condensate.

[0028] According to the embodiments disclosed herein, the aqueous phase and the organic phase are colorless.

[0029] According to the embodiments of this disclosure, the pH value of the aqueous washing solution is in the range of 6.7 to 6.8.

[0030] According to embodiments of this disclosure, the aqueous washing solution contains 1% to 5% by mass of an alkali metal salt solution.

[0031] According to embodiments of this disclosure, the alkali metal salt is at least one selected from sodium bisulfite, potassium bisulfite, sodium hydroxide, and potassium hydroxide.

[0032] According to embodiments of this disclosure, the carbonyl compound impurities in the mixed C4 hydrocarbon stream are in the range of 50 ppm to 700 ppm.

[0033] According to the embodiments of this disclosure, a mixed C4 hydrocarbon stream is fed into a carbonyl compound scrubbing tower at a feed rate of 15 tons / hour to 20 tons / hour.

[0034] According to embodiments of this disclosure, an aqueous washing solution is fed into a carbonyl compound washing tower at a feed rate of 150 kg / h to 300 kg / h.

[0035] According to another embodiment of this disclosure, an aqueous washing solution is fed into a carbonyl compound washing tower at a feed rate of 160 kg / h to 250 kg / h.

[0036] According to one implementation scheme, the stoichiometric ratio of carbonyl compound impurities to aqueous washing solution is in the range of 1:1 to 1:1.5.

[0037] According to embodiments of this disclosure, the carbonyl compound scrubbing tower is maintained at a temperature ranging from 25°C to 40°C and a pressure of 4 kg / cm³. 2 g to 8 kg / cm 2 Under pressure within the range of g.

[0038] According to embodiments of this disclosure, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower contains reduced carbonyl compound impurities ranging from 0 to 10 ppm.

[0039] According to embodiments of this disclosure, the mixed C4 hydrocarbon stream contains impurities selected from p-tert-butylcatechol (p-TBC) and soluble iron substances to provide a C4 hydrocarbon stream that is colorless and has reduced or no carbonyl compound impurities.

[0040] Brief description of the attached figures

[0041] The contents of this disclosure will now be described with reference to the accompanying drawings, in which: Figure 1 An apparatus for collecting a mixed C4 stream according to the present disclosure is shown, wherein (a) a stainless steel (SS) spring reactor is shown, (b) a container containing an aqueous washing solution is shown, and (c) a connector is shown. Figure 2 Test results observing the effects of condensate from the device on the washing solution and impurity components are shown, wherein (a) shows a colorless solution formed when the condensate is mixed with p-tert-butylcatechol (p-TBC); (b) shows a colorless solution formed when the condensate is mixed with p-TBC solution and sodium bisulfite (SBS) solution; and (c) shows a deep red color when the condensate is mixed with p-TBC solution and sodium hydroxide solution, which is consistent with the color observed in the device according to this disclosure.

[0042] Detailed description

[0043] This disclosure relates to a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream.

[0044] The embodiments of this disclosure will now be described with reference to the accompanying drawings.

[0045] The embodiments provided are intended to fully and completely communicate the scope of this disclosure to those skilled in the art. Numerous details relating to particular components and methods are given to provide a complete understanding of the embodiments of this disclosure. It will be apparent to those skilled in the art that the details provided in the embodiments should not be construed as limiting the scope of this disclosure. In some embodiments, known processes, well-known apparatus or structures, and well-known technologies are not described in detail.

[0046] The terminology used in this disclosure is for the purpose of explaining particular embodiments only and should not be construed as limiting the scope of this disclosure. Unless the context explicitly teaches otherwise, the forms “a,” “an,” and “the” as used in this disclosure may also be intended to include plural forms. The terms “comprises,” “composing,” “including,” and “having” are open-ended transitional phrases and thus only indicate the presence of the stated feature, integer, step, operation, element, module, unit, and / or component, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof. The specific order of steps disclosed in the methods and processes of this disclosure should not be construed as requiring them to be performed in the manner described or shown. It should also be understood that additional or alternative steps may be employed.

[0047] The terms first, second, third, etc., should not be construed as limiting the scope of this disclosure, as these terms may be used only to distinguish one element, component, region, layer, or part from another. Unless expressly taught in this disclosure, the terms first, second, third, etc., as used herein, do not imply a particular order or sequence.

[0048] The term “and / or” as used herein includes any and all combinations of one or more of the related listed elements.

[0049] Butadiene is an important industrial chemical used in the manufacture of synthetic rubber, latex paint, nylon, and other products. It is also a commonly used chemical in Diels-Alder condensation processes to synthesize a variety of different compounds. Butadiene is typically recovered from a mixture of C4 hydrocarbon streams obtained from naphtha or gas vapor crackers. During butadiene recovery, trace amounts of carbonyl compound impurities (such as acetaldehyde and acetone) are found. These impurities can adversely affect subsequent processes using butadiene as a feedstock. Therefore, removing these carbonyl compound impurities from the C4 hydrocarbon stream mixture is crucial.

[0050] Traditionally, organic compounds containing carbonyl groups are removed from mixed C4 hydrocarbon streams using "washing solutions" such as hydrazine hydrate washing solutions. For this purpose, carbonyl compound scrubbing towers are used in butadiene (BD) plants to remove carbonyl compound impurities. However, hydrazine hydrate washing solutions are not effective at removing all carbonyl compound impurities present in mixed C4 hydrocarbon streams, nor can they meet the desired specification requirement of aldehyde content below 10 ppm in mixed C4 hydrocarbon streams.

[0051] Furthermore, the mixed C4 hydrocarbon stream contains carbonyl compound impurities, such as acetaldehyde, acetone, and other carbonyl compounds, which can be effectively removed by treatment with alkali metal bisulfites. However, due to the acidity of alkali metal bisulfites, direct addition to the tower may cause corrosion.

[0052] The composition of the mixed C4 hydrocarbon stream varies depending on the process in which the equipment is operated, i.e., from a gas pyrolyte, naphtha pyrolyte, or gas-naphtha dual pyrolyte process. The gas pyrolyte product stream has a lower percentage of C4 hydrocarbons compared to the naphtha pyrolyte product stream. Therefore, the naphtha pyrolyte product stream is preferred for butadiene production because it contains a significant amount of C4 hydrocarbons in addition to compounds such as ethylene, propylene, and other hydrocarbons. Furthermore, depending on process optimization, a mixture of the naphtha pyrolyte product stream and the gas pyrolyte product stream can also be processed to produce a mixed C4 hydrocarbon stream.

[0053] The product stream from the gas pyrolyzer has a high carbonyl compound feed content (>350 ppm). Furthermore, when the product stream from the gas pyrolyzer is mixed with the product stream from the gas-naphtha dual pyrolyzer, the resulting mixed C4 hydrocarbon stream can have a carbonyl compound content exceeding 500 ppm. In this case, the removal efficiency of carbonyl compounds from the mixed C4 hydrocarbon stream in the scrubbing tower cannot meet the product specification requirements. For the butadiene process, it is desirable that the carbonyl compound impurity content in the product C4 hydrocarbon stream be <10 ppm.

[0054] Furthermore, an increased content of carbonyl compound impurities in the mixed C4 hydrocarbon stream typically increases the consumption of fresh condensate in the carbonyl compound scrubbing tower. This increased consumption of fresh condensate can further corrode the processing unit.

[0055] This disclosure relates to a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream.

[0056] The method includes mixing a mixed C4 hydrocarbon stream containing carbonyl compound impurities with a predetermined amount of an aqueous washing solution with a pH value in the range of 6.5 to 7.0 in a carbonyl compound washing tower maintained at a predetermined temperature and a predetermined pressure to obtain an aqueous phase and an organic phase, wherein the aqueous phase contains carbonyl compound impurities in the form of water-soluble reaction products, and the organic phase contains a C4 hydrocarbon stream with reduced or no carbonyl compound impurities.

[0057] According to embodiments of this disclosure, the mixed C4 hydrocarbon stream is obtained from at least one of the following: naphtha cracking process, gas-gas cracking process, and gas-naphtha dual cracking process.

[0058] According to the embodiments of this disclosure, the method is an intermittent method or a continuous method.

[0059] According to embodiments of this disclosure, the carbonyl compound impurities include acetaldehyde and acetone.

[0060] According to embodiments of this disclosure, the aqueous detergent solution is prepared using at least one selected from distilled water and condensed water. In one exemplary embodiment, the aqueous detergent solution is prepared using distilled water. In another exemplary embodiment, the aqueous detergent solution is prepared using condensed water.

[0061] According to the embodiments disclosed herein, the aqueous and organic phases thus obtained are colorless.

[0062] According to embodiments of this disclosure, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is from 50 ppm to 700 ppm. In another embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is from 50 ppm to 550 ppm. In one exemplary embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is 86 ppm. In another exemplary embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is 104 ppm. In yet another exemplary embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is 115 ppm. In yet another exemplary embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is 312 ppm. In yet another exemplary embodiment, the content of carbonyl compound impurities in the mixed C4 hydrocarbon stream is 600 ppm.

[0063] According to embodiments of this disclosure, the pH value of the aqueous detergent solution is in the range of 6.7 to 6.8. In one exemplary embodiment, the pH value of the aqueous detergent solution is 6.75.

[0064] According to embodiments of this disclosure, the aqueous detergent solution comprises 1% to 5% by mass of an alkali metal salt solution. In one exemplary embodiment, the aqueous detergent solution comprises 3% by mass of an alkali metal salt solution.

[0065] According to embodiments of this disclosure, the alkali metal salt is at least one selected from sodium bisulfite, potassium bisulfite, sodium hydroxide, and potassium hydroxide. In one exemplary embodiment, the alkali metal salt is a mixture of sodium bisulfite and sodium hydroxide.

[0066] According to embodiments of this disclosure, mixed C4 hydrocarbons are fed into a carbonyl compound scrubbing tower at a feed rate of 15 to 20 tons per hour. In one exemplary embodiment, the mixed C4 hydrocarbons are fed into the carbonyl compound scrubbing tower at a feed rate of 16 tons per hour.

[0067] According to embodiments of this disclosure, an aqueous washing solution is fed into a carbonyl compound washing tower at a feed rate of 150 kg / h to 300 kg / h. According to another embodiment of this disclosure, the aqueous washing solution is fed into the carbonyl compound washing tower at a feed rate of 160 kg / h to 250 kg / h. According to an exemplary embodiment, the aqueous washing solution is fed into the carbonyl compound washing tower at a feed rate of 250 kg / h.

[0068] According to embodiments of this disclosure, the stoichiometric ratio of carbonyl compound impurities to aqueous washing solution is in the range of 1:1 to 1:1.5. In one exemplary embodiment, in a batch process, the stoichiometric ratio of carbonyl compound impurities to aqueous washing solution is 1:1.1.

[0069] According to embodiments of this disclosure, the carbonyl compound scrubbing tower is maintained at a temperature ranging from 25°C to 40°C and a pressure of 4 kg / cm³. 2 g to 8 kg / cm 2 Under pressures within the g range. In one exemplary embodiment, the top temperature of the column is 29°C, and the bottom temperature is 29°C. In this exemplary embodiment, the top pressure is 5.6 kg / cm². 2 g, the pressure at the bottom of the tower is 6.7 kg / cm². 2 g.

[0070] In batch operations, the mixing time for the C4 hydrocarbon stream and the aqueous washing solution is from 5 to 30 minutes. In one exemplary embodiment, the mixing time for the C4 hydrocarbon stream and the aqueous washing solution in batch operations is 20 minutes.

[0071] In continuous flow operation, the C4 hydrocarbon stream and aqueous washing solution are mixed and flow from the top to the bottom of the column, and the mixing time of the C4 hydrocarbon stream and aqueous washing solution does not exceed 60 seconds.

[0072] In one embodiment, the mixing time of the C4 hydrocarbon stream with the aqueous washing solution is from 1 second to 60 seconds. In an exemplary embodiment, the mixing time of the C4 hydrocarbon stream with the aqueous washing solution is 5 seconds. The reaction of the carbonyl compound with the aqueous washing solution involves an initial attack on the carbonyl compound carbon via nucleophilic addition of a bisulfite ion.

[0073] According to embodiments of this disclosure, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower has a reduced carbonyl compound impurity level ranging from 0 to 10 ppm. In one exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower is free of carbonyl compound impurities. In another exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower has a reduced carbonyl compound impurity level of < 5 ppm. In yet another exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower has a reduced carbonyl compound impurity level of 2 ppm. In yet another exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower has a reduced carbonyl compound impurity level of 1 ppm. In yet another exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower has a reduced carbonyl compound impurity level of 3 ppm. In yet another exemplary embodiment, the C4 hydrocarbon stream from the carbonyl compound scrubbing tower is free of carbonyl compound impurities.

[0074] According to embodiments of this disclosure, the mixed C4 hydrocarbon stream contains impurities from p-tert-butylcatechol (p-TBC) and soluble iron substances to provide a C4 hydrocarbon stream that is colorless and has reduced or no carbonyl compound impurities.

[0075] p-tert-butylcatechol (p-TBC) and soluble iron are introduced into the process through process equipment or added to the process.

[0076] The optimal feed rates of the aqueous washing solution and the mixed C4 hydrocarbon stream, as well as the pH value of their mixture during the reaction process, enable the effective removal of carbonyl compound impurities from the mixed C4 hydrocarbon stream, even in the presence of soluble iron and p-TBC, resulting in a colorless hydrocarbon stream and a colorless aqueous stream.

[0077] The method disclosed herein is a commercially viable process for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream generated during naphtha / gas vapor cracking.

[0078] Carbonyl compound impurities were removed from the mixed C4 hydrocarbons entering the carbonyl compound scrubbing tower of the butadiene (BD) dual pyrolyzer equipment by treatment with an aqueous washing solution, according to the method of this disclosure.

[0079] The method disclosed herein reduces the consumption of fresh condensate used in conventional methods for preparing detergent solutions. The method also reduces the discharge load on wastewater treatment plants (ETPs).

[0080] The present invention provides an economical and commercially viable method comprising contacting a mixed C4 hydrocarbon stream (e.g., butadiene) with an aqueous washing solution.

[0081] This disclosed method is an environmentally friendly approach for removing carbonyl compound impurities. Because the mixed C4 hydrocarbon stream is free of carbonyl compound impurities, this method minimizes the loss of butadiene polymerization catalyst activity. This mixed C4 hydrocarbon stream is the feedstock for the butadiene polymerization process. This disclosed method reduces process complexity while obtaining high-quality butadiene products. Furthermore, because the wastewater is colorless, this disclosed method has no impact on wastewater treatment. The annual cost-effectiveness is approximately INR 15 million.

[0082] The method disclosed herein can be easily scaled up.

[0083] The method disclosed herein can be commercialized in carbonyl compound scrubbing towers and can operate efficiently for more than 365 days.

[0084] The method disclosed herein can reduce the consumption of fresh condensate and improve the efficiency of carbonyl compound scrubbers.

[0085] The method disclosed herein solves the problem of condensate color changing from dark red to light red, a color change that may be due to the presence of p-tert-butylcatechol (p-TBC) or soluble iron in the mixed C4 hydrocarbon stream. The mixed C4 hydrocarbon stream also contains p-TBC, which can act as a stabilizer and polymerization inhibitor for butadiene and other reactive monomers in the stream.

[0086] p-TBC is a weak acid that dissociates in alkaline media and associates in acidic media (reversibly during pH adjustment). p-TBC is a widely used industrial antioxidant and potent decolorizing agent. The dissociated state of p-TBC is highly soluble in water, while the associated state is insoluble. Under alkaline conditions, p-TBC can react with iron ions (Fe²⁺). 3+ The reaction proceeds and forms a red complex. Normally, aqueous solutions of FeCl3 are green, while alkaline solutions rapidly turn green upon exposure to air, eventually becoming black. The association-dissociation of p-TBC is represented as:

[0087] Sodium bisulfite (SBS) can be effectively used to remove carbonyl compound impurities from the C4 column feed in a carbonyl compound scrubbing tower via chemical treatment. The concentration of sodium bisulfite depends on the concentration of carbonyl compounds present in the feed. However, to drive the equilibrium towards the desired reaction direction, sodium bisulfite needs to be at or slightly above stoichiometric levels.

[0088] The reaction of carbonyl compounds (especially aldehydes and ketones) with sodium bisulfite takes place in aqueous solution and involves the initial attack on the carbonyl compound by the nucleophilic addition of the bisulfite ion. SBS is an acidic salt formed by the neutralization of a strong acid and a weak base. It readily dissociates in water to form an acidic solution. The bisulfite-carbonyl compound adduct is a non-volatile, thermally stable, and highly water-soluble substance. The dissociation of the bisulfite ion and its nucleophilic addition to the carbonyl compound are represented as follows:

[0089] The foregoing description of the embodiments is provided for illustrative purposes and is not intended to limit the scope of this disclosure. The components of a particular embodiment are generally not limited to that particular embodiment and are interchangeable. Such variations should not be considered a departure from this disclosure, and all such modifications are considered to be within the scope of this disclosure.

[0090] The present disclosure is further described below with the aid of the following experiments. The experiments used herein are intended only to help understand how the embodiments described herein can be practiced and to further enable those skilled in the art to practice the embodiments described herein. Therefore, these experiments should not be construed as limiting the scope of the embodiments described herein. These laboratory-scale experiments can be scaled up to industrial / commercial scale, and the results obtained can be extrapolated to industrial / commercial scale.

[0091] Experiment details: Experiment 1: Method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream according to this disclosure (laboratory scale) Samples of a mixed C4 hydrocarbon stream and condensate were collected from a certain device for three consecutive days. The mixed C4 hydrocarbon stream was collected in a container such as... Figure 1 In the stainless steel (SS) container (bomb reactor) shown.

[0092] Analysis was performed to determine the carbonyl compound (aldehyde) content in the mixed C4 hydrocarbon stream and the pH value of the condensate. The results are listed in Table 1.

[0093] Table 1: Analysis of total aldehydes and pH value of condensate in mixed C4 hydrocarbon samples from different test dates

[0094] As shown in Table 1, the carbonyl compound content in the mixed C4 hydrocarbon stream ranged from 92 ppm to 118 ppm. Due to the presence of dissolved hydrazine compounds, the condensate was alkaline, with a pH value ranging from 8.7 to 9.3.

[0095] First, preliminary laboratory experiments were conducted to identify the source of the color observed in the carbonyl compound scrubbing tower of the equipment. Solutions of NaOH, sodium bisulfite, p-TBC, and iron (FeCl3) were prepared separately. By mixing condensate with p-TBC, a colorless solution was observed (see...). Figure 2 (a)). When the condensate, p-TBC solution, and SBS solution were mixed, another colorless solution was observed (see Figure 2 (b)). However, when the condensate, p-TBC solution, and NaOH solution were mixed together, a deep red solution was observed (see [link]). Figure 2 (c)). This deep red color matches the color observed in the device very well.

[0096] In another set of experiments, the color of the carbonyl compound scrubber emissions observed in the device differed slightly from the color of the solution obtained by mixing iron with a solution of NaOH and p-TBC. However, the color observed in the device was in perfect agreement with the color of the solution obtained by mixing a solution of iron (FeCl3) and SBS with a solution of NaOH and p-TBC.

[0097] In conventional processes, the removal efficiency of carbonyl compounds was observed to decrease with time and pH, eventually requiring the cessation of SBS addition to the equipment. Observations revealed that the deep red color was due to the presence of NaOH, Fe ions, and p-tert-butylcatechol (p-TBC) in the reaction mixture. Inductively coupled plasma (ICP) analysis confirmed the presence of iron impurities at the carbonyl compound scrubber outlet, and X-ray diffraction (XRD) analysis detected SBS. Furthermore, observations confirmed that in the absence of alkali (NaOH), all reaction mixture solutions exhibited no color.

[0098] The collected mixed C4 hydrocarbon stream, containing carbonyl compound impurities (primarily acetaldehyde and acetone) ranging from 92 ppm to 118 ppm, was treated in an aqueous medium with a reducing agent such as sodium bisulfite (SBS), or under ambient conditions with sodium bisulfite adjusted to pH using NaOH solution, to remove the carbonyl compound impurities. Gas samples were collected from the scrubber outlet for carbonyl compound content analysis. The carbonyl compound content in the mixed C4 hydrocarbon stream was analyzed using the ASTM D7423 method on a LowPX GC from QC-HMD.

[0099] Example 1 - Removal of carbonyl compound impurities by excess SBS under acidic pH conditions

[0100] Carbonyl compounds were removed from mixed C4 hydrocarbons by washing a fixed amount (~25 g) of mixed C4 hydrocarbon gas from a commercial facility into an SBS solution. 200 g of 3 wt% SBS prepared in distilled water (DI) was added to the scrubber. The pH of the SBS solution was 4.1. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 86 ppm. After passing a 25 g sample of mixed C4 hydrocarbons through the scrubber, the pH of the aqueous phase was 4.4. After the reaction, the carbonyl compound content in the effluent C4 hydrocarbon sample (organic phase) was 1 ppm.

[0101] Example 2 - Removal of carbonyl compound impurities by excess SBS under neutral pH conditions

[0102] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of the gas into an SBS solution. 200 g of a 3 wt.% SBS solution prepared in DI water was added to the scrubber. The pH of the SBS solution was adjusted to 7 by adding NaOH solution. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 86 ppm. After passing through a 25 g sample of the mixed C4 hydrocarbons, the pH of the aqueous phase was 6.9. After the reaction, the carbonyl compound content in the outlet C4 hydrocarbon sample (organic phase) was 2 ppm.

[0103] Example 3 - Removal of carbonyl compound impurities by excess SBS under alkaline pH conditions

[0104] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of the gas into an SBS solution. 200 g of a 3 wt.% SBS solution prepared in DI water was added to the scrubber. The pH of the SBS solution was adjusted to 9 by adding NaOH solution. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 86 ppm. After passing through a 25 g sample of the mixed C4 hydrocarbons, the pH of the aqueous phase was 9. After the reaction, the carbonyl compound content in the outlet C4 hydrocarbon sample (organic phase) was 2 ppm.

[0105] Example 4 - Removal of carbonyl compound impurities by excess SBS under acidic pH conditions

[0106] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of the gas mixture into an SBS solution. 200 g of a 3 wt.% SBS solution prepared in condensate was added to the scrubber. The pH of the SBS solution was 5.3. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 104 ppm. After passing a 25 g sample of the mixed C4 hydrocarbons, the pH of the aqueous phase was 5. After the reaction, the carbonyl compound content in the outlet C4 hydrocarbon sample (organic phase) was 6 ppm.

[0107] Example 5 - Removal of carbonyl compound impurities by excess SBS under neutral pH conditions

[0108] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of the gas mixture into an SBS solution. 200 g of a 3 wt.% SBS solution prepared in condensate was added to the scrubber. The pH of the SBS solution was adjusted to 7.1 by adding NaOH solution. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 104 ppm. After passing through a 25 g sample of the mixed C4 hydrocarbons, the pH of the aqueous phase was 7.1. After the reaction, the carbonyl compound content in the outlet C4 hydrocarbon sample (organic phase) was 3 ppm.

[0109] Example 6 - Removal of carbonyl compound impurities by excess SBS under alkaline pH conditions

[0110] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of the gas into an SBS solution. 200 g of a 3 wt.% SBS solution prepared in condensate was added to the scrubber. The pH of the SBS solution was adjusted to 9.1 by adding NaOH solution. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 104 ppm. After passing through a 25 g sample of the mixed C4 hydrocarbons, the pH of the aqueous phase was 9.1. After the reaction, the carbonyl compound content in the outlet C4 hydrocarbon sample (organic phase) was 2 ppm.

[0111] Example 7 - Removal of carbonyl compound impurities by stoichiometric amounts of SBS under near-neutral pH conditions

[0112] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~75 g) of mixed C4 hydrocarbon gas into an SBS solution. A stoichiometric amount of SBS (0.009 g) relative to 75 g of mixed C4 hydrocarbons containing 100 ppm carbonyl compounds was added to 200 g of condensate. The pH of the SBS solution was 6.5. The total carbonyl compound impurity content of the mixed C4 hydrocarbons was 115 ppm. After passing through the 75 g mixed C4 hydrocarbon sample, the pH of the aqueous phase was 7.1. After the reaction, the carbonyl compound content in the outlet mixed C4 hydrocarbon sample (organic phase) was 4 ppm.

[0113] Example 7A - Removal of carbonyl compound impurities by stoichiometric amounts of SBS under alkaline pH conditions.

[0114] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~75 g) of mixed C4 hydrocarbon gas into an SBS solution. A stoichiometric amount of SBS (0.009 g) relative to 75 g of mixed C4 hydrocarbons containing 100 ppm carbonyl compounds was added to 200 g of condensate. The pH of the SBS solution was adjusted to 7.1 by adding NaOH solution. The total carbonyl compound content of the mixed C4 hydrocarbons was 115 ppm. After passing through the 75 g mixed C4 hydrocarbon sample, the pH of the aqueous phase was 8.1. After the reaction, the carbonyl compound content in the outlet mixed C4 hydrocarbon sample (organic phase) was 7 ppm.

[0115] Example 8 - Removal of carbonyl compound impurities by stoichiometric SBS under alkaline pH conditions

[0116] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~75 g) of mixed C4 hydrocarbon gas into an SBS solution. A stoichiometric amount of SBS (0.009 g) relative to 75 g of mixed C4 hydrocarbons containing 100 ppm carbonyl compounds was added to 200 g of condensate. The pH of the SBS solution was adjusted to 8.1 by adding NaOH solution. The total carbonyl compound content of the mixed C4 hydrocarbons was 115 ppm. After passing through the 75 g mixed C4 hydrocarbon sample, the pH of the aqueous phase was 8.6. After the reaction, the carbonyl compound content in the outlet mixed C4 hydrocarbon sample (organic phase) was 14 ppm.

[0117] Example 9 - Removal of carbonyl compound impurities by stoichiometric SBS under alkaline pH conditions

[0118] Carbonyl compounds were removed from the mixed C4 hydrocarbons by washing a fixed amount (~25 g) of mixed C4 hydrocarbon gas into an SBS solution. A stoichiometric amount of SBS (0.009 g) relative to 75 g of mixed C4 hydrocarbons containing 100 ppm carbonyl compounds was added to 200 g of condensate. The pH of the SBS solution was adjusted to 10.9 by adding NaOH solution. The total carbonyl compound content of the mixed C4 hydrocarbons was 115 ppm. After passing a 25 g sample of mixed C4 hydrocarbons, the pH of the aqueous phase was 11. After the reaction, the carbonyl compound content in the outlet mixed C4 hydrocarbon sample (organic phase) was 15 ppm.

[0119] Table 2: Removal of carbonyl compounds from mixed C4 hydrocarbon streams by applying various washing solutions from different water streams. DI: Distilled water As shown in Table 2, although some solutions had neutral or alkaline pH values ​​before the reaction, the removal efficiency of carbonyl compounds was very significant in each case. The neutral or alkaline SBS solutions were prepared by adding NaOH. Effective removal of aldehyde impurities was achieved by adding stoichiometric amounts of SBS and maintaining a near-neutral pH value (Examples 7, 7A). When similar studies were conducted under alkaline conditions with pH values ​​above 8, the aldehyde removal efficiency was relatively low (Example 8).

[0120] Example 10

[0121] Another laboratory test was conducted when the aldehyde impurity content in the mixed C4 hydrocarbon stream was 600 ppm. Furthermore, the efficiency of the process in the presence of other impurities (e.g., p-TBC and iron) was tested. Iron impurities may be introduced into the carbonyl compound tower due to leaching from the carbon steel alloy. Details and results of this laboratory test are shown in Table 3.

[0122] Table 3: Laboratory Tests

[0123] SBS: Sodium bisulfite; TBC: p-tert-butylcatechol

[0124] Observations revealed that when the mixed C4 hydrocarbon stream was at pH 6.5 and contained other impurities such as iron and p-TBC, treatment with 5 mL of 3 wt% SBS solution yielded a colorless aqueous phase with pH 7.1. The aldehyde impurity content in the mixed C4 hydrocarbon product stream was 8%.

[0125] On a laboratory scale, a slight excess of SBS beyond the stoichiometric amount helps to keep the reaction proceeding in the forward direction, thus effectively removing carbonyl compounds. Maintain a carbonyl compound:SBS ratio of 1:1.1.

[0126] For laboratory analysis, the mixed C4 hydrocarbons were mixed with an aqueous washing solution (SBS solution) for 10, 15, and 20 minutes. Better results were observed when the mixed C4 hydrocarbons were flown in the SBS solution for 20 minutes.

[0127] The planned and constructed facility demonstrates an effective process for removing carbonyl compound impurities from mixed C4 hydrocarbon streams via chemical means.

[0128] Experiment 2: Commercial process operation data for the removal of carbonyl compound impurities

[0129] Table 4 shows the composition of the mixed C4 hydrocarbon stream collected from the naphtha cracker and entering the carbonyl compound scrubbing tower, indicating the presence of 312 ppm carbonyl compound impurities.

[0130] Table 4: Examples of feed composition for mixed C4 hydrocarbon streams entering a carbonyl compound scrubbing tower

[0131] The equipment and process operating conditions for the carbonyl compound scrubbing tower in the naphtha cracker are shown in Table 5.

[0132] Table 5: Operating conditions of C4 carbonyl compound scrubbing tower

[0133] Examples 11-15

[0134] In the commercial operation of a C4 carbonyl compound scrubbing tower in a certain commercial facility, the flow rate of the C4 feed into the carbonyl compound scrubbing tower is 16.5 ± 0.5 tons per hour (TPH). The sodium bisulfite solution is adjusted to the desired pH value by adding an alkaline solution (3 wt% NaOH).

[0135] The pH-adjusted SBS solution was added to the C4 carbonyl compound scrubbing tower at different feed rates. The results of carbonyl compound impurity removal are summarized in Table 6.

[0136] Table 6: Effect of SBS addition rate on the removal rate of carbonyl compound impurities in the C4 carbonyl compound scrubbing tower of the equipment

[0137] Observation results : In the experiment of Example 11, a pH of 9.8 / 9.9 was observed at the bottom of the carbonyl compound scrubber, which was unusually high compared to the SBS feed solution with a pH of ~7. The reported Fe content (soluble iron) was 4 ppm to 4.1 ppm, and the solution at the bottom of the carbonyl compound scrubber was dark red.

[0138] In the carbonyl compound scrubbing tower, a higher SBS feed rate (125 ± 5 kg / h) showed better results in carbonyl compound removal. When the pH of the inlet SBS solution was 6.7 to 6.8, the carbonyl compound removal efficiency increased from 80% to over 98%. With increasing scrubbing solution addition rate, the pH of the outlet stream changed from alkaline to neutral. When the outlet stream pH was alkaline, the treated mixed C4 hydrocarbon stream was also observed to be dark red. Under optimized pH 7 conditions, when the SBS feed rate was increased to 170 ± 10 kg / h, the efficiency reached 90%, and the aldehyde content in the treated stream outlet was below 10 ppm. Furthermore, optimizing the pH and feed rate of the scrubbing solution also resolved the color issue, reducing the color from dark red to light. Furthermore, when the pH value is adjusted to 6.7-6.8 and the SBS feed rate is maintained at 170±10 kg / hour, the carbonyl compound removal efficiency reaches over 98%, and the carbonyl compound impurity content in the outlet feed is < 5 ppm.

[0139] When the SBS feed rate was increased to 250 kg / hr and the pH was 6.7-6.8, the throughput of the C4 carbonyl compound scrubbing tower was further increased, and no aldehyde impurities were observed in the treated mixed C4 hydrocarbon sample at the outlet.

[0140] Technological progress

[0141] The present disclosure described above has several technical advantages, including but not limited to a method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream, wherein the method: Simple, economical, and environmentally friendly; It can effectively remove high levels of carbonyl compound impurities; It can be easily scaled up for commercial purposes; Reduce the wastewater load on the wastewater treatment plant (ETP); Reduce the consumption of fresh condensate and improve the efficiency of carbonyl compound scrubbers; The color issues of the effluent (organic phase) and aqueous phase have been resolved; It can run for a longer time.

[0142] In the following description, embodiments thereof and their various features and advantageous details will be explained with reference to non-limiting embodiments. To avoid unnecessarily obscuring the embodiments herein, descriptions of well-known components and processing techniques have been omitted. The examples used herein are intended only to help understand how the embodiments herein can be practiced and to further enable those skilled in the art to practice them. Therefore, these examples should not be construed as limiting the scope of the embodiments herein.

[0143] The above description of the specific implementation schemes fully reveals the general nature of the schemes described herein, enabling others to easily modify and / or adjust these specific implementation schemes to suit various applications by applying existing knowledge without departing from the general concepts. Therefore, such modifications and adjustments should and are intended to be understood as falling within the meaning and scope of the disclosed implementation schemes. It should be understood that the wording or terminology used herein is for descriptive purposes only and not for limiting purposes. Therefore, although the implementation schemes have been described herein by way of preferred embodiments, those skilled in the art will recognize that the implementation schemes herein can be implemented by modifications within the spirit and scope of the schemes described herein.

[0144] The use of the expressions "at least" or "at least one" indicates the use of one or more elements, components, or amounts, as may be used in embodiments of this disclosure, to achieve one or more desired purposes or results.

[0145] The discussion of any documents, actions, materials, equipment, articles, or similar items included in this specification is for the purpose of providing background to this disclosure only. It should not be construed as an admission that any or all of these matters constitute part of the prior art or common general knowledge existing anywhere in the relevant field of this disclosure prior to the priority date of this application.

[0146] The values ​​mentioned for various physical parameters, dimensions or quantities are only approximate values, and unless otherwise expressly stated to the contrary in the specification, values ​​higher or lower than those assigned to these parameters, dimensions or quantities are conceivable to fall within the scope of this disclosure.

[0147] While this document has focused considerably on the components and elements of the preferred embodiments, it should be understood that various embodiments are possible, and various modifications can be made to the preferred embodiments without departing from the principles of this disclosure. These and other modifications to the preferred and other embodiments will be apparent to those skilled in the art from the disclosure herein. Therefore, it should be clearly understood that the above description is for illustrative purposes only and not for limiting the scope of this disclosure.

Claims

1. A method for removing carbonyl compound impurities from a mixed C4 hydrocarbon stream, the method comprising: The following substances are mixed in a carbonyl compound scrubbing tower maintained at a predetermined temperature and pressure: The mixed C4 hydrocarbon stream containing the carbonyl compound impurities, and A predetermined amount of aqueous washing solution with a pH value in the range of 6.5 to 7.

0. An aqueous phase and an organic phase are obtained, wherein the aqueous phase contains carbonyl compound impurities in the form of water-soluble reaction products, and the organic phase contains a C4 hydrocarbon stream with reduced carbonyl compound impurity content.

2. The method of claim 1, wherein the carbonyl compound impurity comprises acetaldehyde and acetone.

3. The method of claim 1, wherein the mixed C4 hydrocarbon stream is obtained from at least one of the following: naphtha cracking process, gas stream cracking process, and gas-naphtha dual cracking process.

4. The method of claim 1, wherein the aqueous washing solution is prepared by using at least one selected from distilled water and condensate.

5. The method of claim 1, wherein the aqueous phase and the organic phase are colorless.

6. The method of claim 1, wherein the pH value of the aqueous washing solution is in the range of 6.7 to 6.

8.

7. The method of claim 1, wherein the aqueous washing solution comprises 1% to 5% by mass of an alkali metal salt solution.

8. The method of claim 7, wherein the alkali metal salt is at least one selected from sodium bisulfite, potassium bisulfite, sodium hydroxide, and potassium hydroxide.

9. The method of claim 1, wherein the carbonyl compound impurities in the mixed C4 hydrocarbon stream are in the range of 50 ppm to 700 ppm.

10. The method of claim 1, wherein the mixed C4 hydrocarbon stream is fed into the carbonyl compound scrubbing tower at a feed rate of 15 tons / hour to 20 tons / hour.

11. The method of claim 1, wherein the aqueous washing solution is fed into the carbonyl compound washing tower at a feed rate of 150 kg / h to 300 kg / h.

12. The method of claim 1, wherein the aqueous washing solution is fed into the carbonyl compound washing tower at a feed rate of 160 kg / h to 250 kg / h.

13. The method of claim 1, wherein the stoichiometric ratio of the carbonyl compound impurity to the aqueous washing solution is in the range of 1:1 to 1:1.

5.

14. The method of claim 1, wherein the carbonyl compound scrubbing tower is maintained at a temperature in the range of 25°C to 40°C and a pressure of 4 kg / cm³. 2 g to 8 kg / cm 2 Under pressure within the range of g.

15. The method of claim 1, wherein the C4 hydrocarbon stream from the carbonyl compound scrubbing tower contains reduced carbonyl compound impurities ranging from 0 to 10 ppm.

16. The method of claim 1, wherein the mixed C4 hydrocarbon stream comprises impurities selected from p-tert-butylcatechol (p-TBC) and soluble iron substances.

17. The method of claim 16, wherein the method provides a C4 hydrocarbon stream that is colorless and has reduced or no carbonyl compound impurities.

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