Mesoporous ZSM-22 for increased propylene production

Abstract

The present invention relates to mesoporous ZSM-22 for increased propylene production. The present invention relates to the use of a mesoporous ZSM-22 zeolite in a process for cracking or converting a feed comprising hydrocarbons, such as hydrocarbons obtained from processing crude oil, to a propylene-rich mixture. Furthermore, the present invention relates to the field of fluid catalytic cracking (FCC) processes and to the preparation and use of additives based on zeolites with increased mesoporosity, such as altered ZSM-22. More specifically, the present invention discloses a process for improving propylene production in an FCC unit.

Description

[0001] This application is a divisional application of the parent application with application number 201780039172.1. The parent application was filed on June 24, 2017; the invention is entitled "ZSM-22 for increasing the mesopores in propylene production". Technical Field

[0002] This invention relates to the use of mesoporous ZSM-22 zeolite in methods for cracking or converting feed containing hydrocarbons, such as hydrocarbons obtained from processed crude oil, into a propylene-rich mixture. Furthermore, this invention relates to the field of fluid catalytic cracking (FCC) methods and to the preparation and use of additives based on zeolites with increased mesoporosity, such as modified ZSM-22. More specifically, this invention discloses an improved method for propylene production in an FCC unit. Background Technology

[0003] Fluid catalytic cracking (FCC) is carried out by contacting hydrocarbons in a tubular reaction zone or riser with a catalyst composed of fine particulate material. The feedstocks most commonly subjected to FCC processes are typically streams of refined oil from the vacuum column side fraction (called heavy vacuum gas oil (HVGO)) or heavier streams from the bottom of an atmospheric distillation column (called atmospheric residue (RAT)), or mixtures of such streams. These streams typically have densities in the range of 8° API to 28° API, and they require chemical processes (such as catalytic cracking) to fundamentally alter their composition, converting them into lighter hydrocarbon streams with greater economic value.

[0004] During the cracking reaction, a significant amount of coke (a byproduct of the reaction) deposits on the catalyst. The spent catalyst is directed to a regeneration zone where the coke is burned off to remove it from the catalyst. Removing the coke through combustion allows for the restoration of catalyst activity and releases sufficient heat to meet the thermal requirements of the catalytic cracking reaction.

[0005] Since its initial conception, the FCC process has primarily focused on the production of high-octane gasoline, and is also responsible for LPG production. The resulting middle distillate (LCO) is predominantly aromatic compounds, making it difficult to incorporate these into the diesel fuel. However, current and future trends indicate declining gasoline consumption and increasing diesel demand. Fluid catalytic cracking units are playing an increasingly important role in propylene production.

[0006] In FCC practice, there are two methods to improve the selectivity for light olefins. The first method is to increase the reaction temperature. This will increase the contribution of thermal cracking, thereby increasing the formation of lighter products. For example, in the so-called DCC (deep catalytic cracking) process, a specific type of FCC method is used, with higher temperatures and increased steam volume. However, thermal cracking is not very selective and produces a large number of relatively low-value products such as hydrogen, methane, ethane, and ethylene in the “wet gas” (which contains H2 and C1-C4 products). Wet gas compression often limits the operation of refining plants.

[0007] The second approach involves adding an additive containing a zeolite with olefin selectivity, such as an additive containing ZSM-5. Conventional additives typically contain phosphorus-activated ZSM-5, which selectively converts primary cracking products (e.g., gasoline olefins) into C3 and C4 olefins. It is known that improving activity or selectivity with phosphorus can enhance the effectiveness of ZSM-5. For example, EP-A-511 013 describes treating ZSM-5 with phosphorus to improve propylene selectivity. Furthermore, U.S. Patent No. 5,472,594 describes a method for converting a hydrocarbon feedstock into a product with an increased C4 / C5 olefin yield using a catalyst composition containing zeolite Y and an additive containing a phosphorus-containing mesoporous zeolite (e.g., ZSM-5). Additionally, Mobil's WO 98 / 41595 describes a method for catalytically cracking a hydrocarbon feedstock to produce an increased C3 to C5 olefin yield using a catalyst composition comprising a macroporous molecular sieve (e.g., zeolite Y) and an additive containing phosphorus-containing ZSM-5 blended with a base catalyst containing zeolite Y. The method is described in U.S. Patent No. 5,456,821. WO 94 / 13754 describes the same method using a catalyst composition containing a macroporous molecular sieve and an additive containing a specific ZSM-5, wherein the ZSM-5 optionally contains 1.5 wt% to 5.5 wt% elemental phosphorus. Additionally, U.S. Patent No. 5,521,133 describes the preparation of the ZSM-5 additive by injecting a slurry of ZSM-5 and kaolin containing phosphoric acid, followed by spray drying.

[0008] EP 1445297 discloses the use of zeolite ITQ-21, a three-dimensional macroporous zeolite with a very open structure, which is more active in selectively converting vacuum gas oil and propylene into commercially available USY zeolite (described as ultra-stable). WO2008 / 014920 shows that ITQ-33 zeolite, with an average pore size of extra-large 18MR (12.2 Å) and 10MR interconnected channels, simultaneously produces high yields of diesel oil and light olefins, particularly propylene. However, the practical application of these new materials is limited due to their high manufacturing costs.

[0009] Propylene production in FCCs can be increased by altering the operating conditions of the equipment, such as increasing the reactor temperature. However, this solution results in a significant increase in gases, particularly unwanted dry gases. The use of zeolite ZSM-5 as an additive in FCC catalysts increases the C3 and C4 content of olefins (see, for example, US-3758403, US-3769202, US-3894931, US-3894933, US-3894934; US-3926782, US-4309280, US-4309279, US-437458, and Buchanan, JS and Adewuyi, YG, Applied Catalysis: A General, 134, 247 (1996), Madon, RJ, Journal of Catalysis 129 (1), 275 (1991).

[0010] Therefore, there is still a need in the field to develop novel catalyst additives that can selectively increase propylene production, generate low-carbon aromatic compounds, and are cost-effective. Summary of the Invention

[0011] This invention describes a cracking method for organic compounds, preferably using modified zeolite materials from petroleum fractions or synthetic hydrocarbons, characterized by the presence of additional mesoporosity. ZSM-22 is modified to achieve this mesoporosity. The optimal structure provides sufficient space for olefin cracking without aromatization. This implies a trade-off between the ratio of unimolecular to bimolecular cracking and between the ratio of cracking to hydrogen transfer. Therefore, ZSM-22 with increased mesoporosity can be used as an additive in FCC processes.

[0012] These and other embodiments, advantages, and features of the invention will become even clearer from the following detailed description (including the appended claims). Attached Figure Description

[0013] Figure 1 A graph showing the selectivity of propylene and aromatic compounds obtained by cracking C5-C6-C7 olefins with 0.3 g of mesoporous ZSM-22 and 1 g of commercial ZSM-5 at 520 °C and 30 sec TOS.

[0014] Figure 2 Graphical representation of the selectivity of propylene and aromatic compounds for cracking C5-C6-C7 olefins using FCC+ commercial ZSM-5 and FCC+ commercial ZSM-5+ mesoporous-ZSM-22 at 520 °C and 30 sec TOS. Detailed Implementation

[0015] Unless otherwise indicated, weight percentages (wt%) used herein are weight percentages of a particular substance or form of substance as a percentage of the total weight of a product containing its components or parts. It should also be understood that when steps, components, or elements are described herein as preferred, they were preferred up to the initial date of this disclosure, and such preferences are subject to change as given circumstances or future developments in the art.

[0016] One of the most preferred methods for converting heavy hydrocarbon feedstocks into lighter products (e.g., gasoline and distillate range fractions) is fluid catalytic cracking (FCC). However, there is a growing need in the art to increase the yields of low-carbon olefins, LPG, propylene, and other light olefin products (C2-C4 hydrocarbons) in the product composition from catalytic cracking methods. This invention relates to an additive, specifically for use in cracking hydrocarbon feedstocks based on a particular catalyst composition to produce conversion hydrocarbon compounds with lower molecular weights than the feedstock hydrocarbons, such as products containing high propylene fractions and increased LPG.

[0017] This invention provides a fluid catalytic cracking (FCC) method for an FCC unit, employing low-criticality operating conditions to increase LPG and light olefin production and maximize the production of low-carbon aromatic intermediate distillates, which can be incorporated into the diesel fuel. This method differs from prior art methods due to the use of a primitive catalytic system. The invention also provides an additive for the catalytic system, the preparation method of which is disclosed below. The catalyst is an FCC catalyst selective for light olefins, i.e., an FCC catalyst containing an FCC catalyst selective for light olefins (e.g., ZSM-22 type zeolite).

[0018] The primary zeolite used in this invention is typically ZSM-22. ZSM-22 is a zeolite with a TON structure, having a single-dimensional channel system defined by 10 component rings without cavities or intersections. ZSM-22 is typically used in amounts between about 5 wt% and 60 wt% based on dryness.

[0019] It was found that when cracking olefins, propylene can be maximized by restricting aromatization and hydrogen transfer reactions. In this way, the structure of single-dimensional 10MR zeolites does not possess sufficient space to allow bimolecular reactions, such as those that produce aromatic compounds and paraffins. However, compared to three-dimensional 10MR zeolites (e.g., ZSM-5), single-dimensional 10MR zeolites can exhibit restricted diffusion, resulting in lower activity. The reduced overall activity due to diffusion problems in the single-dimensional structure necessitates a larger quantity of zeolite to achieve the desired activity. However, these drawbacks can be overcome by increasing the mesoporosity within ZSM-22.

[0020] Mesoporosity can be obtained by various methods known in the art. It can be obtained through synthetic methods that reduce crystallite size. In this case, the channel length is reduced, thereby allowing reactants and products to diffuse freely and reducing secondary reactions. As an alternative to synthesis, the post-synthetic development of mesoporosity can be carried out by NaOH treatment, as described in the art. For the purposes of this invention, V of treated ZSM-22 is preferred. 中孔 (cm 3 / g) greater than approximately 0.075 cm 3 / g, and more preferably greater than about 0.100 cm 3 / g. Furthermore, it is preferable that the treatment to produce mesoporosity makes V 中孔 (cm 3 / g) increases by at least about 1.5 times, and more preferably increases V 中孔 (cm 3 / g) increases by at least approximately 2 times.

[0021] Although from a catalytic perspective, this effect is very similar to reducing crystal size through synthesis. The process of generating mesoporosity, also known as "desilication," is carried out under aqueous conditions of alkaline pH and moderate temperature. Silica dissolves to create mesopores, the size of which is determined by the Al content (undissolved), temperature, time, and the addition of additives. Excess aluminum deposited as fragments in the mesopores is subsequently removed by moderate acid treatment.

[0022] Controlled desilication in alkaline media has been described in the literature as a cost-effective process that generates additional mesoporosity in the microporous structure of zeolites (see Groen et al., Micro. Meso. Mater. 69 (2004) 29, Perez-Ramirez et al., Chem Soc Rev. 37 (2008) 2530). WO2008 / 147190 describes the preparation of mesoporous mordenite zeolite by generating alkaline extraction of silica mesoporosity. Alkaline treatment can be used independently or in combination with post-synthetic treatments. For example, sequential alkaline and acid treatments can effectively improve the catalytic performance of zeolite materials. Alkali treatment creates mesopores, while acid treatment dissolves aluminum-rich extracellular material and alters the surface acidity of the sample (see, for example, Fernandez et al., Chem Eur J 16 (2010) 6224, Verboekend et al., J. Phys Chem A 115 (2011) 14193, Catal. Technol. 1 (2011) 1331).

[0023] ZSM-22 precursor materials can be prepared as is known in the art, for example, as shown in US 7,094,390. Typical ZSM-22 samples appear as rods or needles approximately 2 micrometers long (by SEM morphology), but can have dimensions known to those skilled in the art. The Si / Al ratio ranges from 25 to 75, and their acidity variation is higher for ZSM22-C, with a greater amount of Brönsted acidity measured by pyridine adsorption. ZSM-22 can be characterized as follows: As a typical example, ZSM22-C was alkaline-treated for 30 minutes at 65°C with stirring using a 0.2M NaOH solution at a liquid-to-solid ratio of 33:1. After washing and filtration to pH=7, the solid was resuspended in oxalic acid solution (1 g zeolite, 2.5 g oxalic acid, 25.5 g water) at 70°C for 2 hours, followed by washing, filtration, and calcination at 375°C for 3 hours. The sample was named mesoporous-ZSM-22. As shown in the table below, the mesopore volume doubled while maintaining microporosity, indicating that the crystal structure was also maintained. The final Si / Al ratio was very similar to that of the original sample. As is known in the art, the pore volume was measured using N2 adsorption.

[0024] sample ZSM-22-C Center Hole - ZSM-22 Si / Al 40 35 <![CDATA[BET (m 2 / g)]]> 218 241 <![CDATA[V 微孔 (cm 3 / g)]]> 0.084 0.083 <![CDATA[V 中孔 (cm 3 / g)]]> 0.059 0.114 When mesoporous samples were tested in olefin cracking, they exhibited improved properties and higher propylene yields. Furthermore, although similar conversion levels were achieved compared to the parent sample, the olefin distribution was closer to thermodynamic equilibrium, with a higher C3 / C4 ratio and higher ethylene yield.

[0025] The results below show that ZSM-22 yields a higher propylene yield and increased mesoporosity compared to ZSM-5. The higher propylene content compared to the ZSM-5-based catalyst is believed to be attributed to the reduced amount of aromatic compounds formed in the one-dimensional channels of ZSM-22, which restricts the bimolecular reactions for aromatic compound production. In fact, the yield of aromatic compounds obtained with ZSM-5 is two to three times higher than that obtained with ZSM-22. Furthermore, in the case of ZSM-22, where diffusion is more restricted than in ZSM-5, there is a reduction in isobutane and isobutene, altering the thermodynamic distribution of C2-C6 olefins, and resulting in a higher upper limit for propylene.

[0026] The results show that zeolite ZSM-22, with its increased mesoporosity, exhibits favorable properties for increasing propylene yield. However, with any increase in mesoporosity, care must be taken not to compromise hydrothermal stability. Due to diffusion limitations, the addition amount of ZSM-22 should be greater than that of ZSM-5. In other words, the optimal structure will provide sufficient space for olefin cracking without aromatization. This implies a trade-off between unimolecular and bimolecular cracking ratios. If space is limited, cracking will be slower and unimolecular, resulting in high ethylene yields for pentene. On the other hand, if too much space exists, cracking will also be bimolecular (oligomeric cracking) and much faster through cross-channels or cavities, but cyclization, aromatization, and hydrogen transfer will reduce propylene yields. In this way, ZSM-22 with increased mesoporosity has shown promising zeolite structures.

[0027] When used as an additive or within an FCC catalyst, the mesoporous ZSM-22 of this invention can be combined with other olefin-selective zeolites and other materials. For example, as part of an FCC catalyst, it can be combined with typical Y zeolite compounds. As another example, when ZSM-22 is combined with ZSM-5, an increase in propylene production is observed compared to the single component. Examples of suitable olefin-selective zeolites are MFI-type zeolites, MEL-type zeolites (e.g., ZSM-11), MTW-type zeolites (e.g., ZSM-12), MWW-type zeolites (e.g., MCM-22, MCM-36, MCM-49, MCM-56), and BEA-type zeolites (e.g., zeolite β). MFI-type zeolites are preferred. MFI type zeolites are as defined in ATLAS OF ZEOLITE STRUCTURE TYPES, WM Meier and DHOlson, 3rd revision (1992), Butterworth-Heinemann, and include ZSM-5, ST-5, ZSM-8, ZSM-11, siliceous rocks, LZ-105, LZ-222, LZ-223, LZ-241, LZ-269, L2-242, AMS-1B, AZ-1, BOR-C, boralite, encilite, FZ-1, NU-4, NU-5, T5-1, TSZ, TSZ-III, TZ01, TZ, USC-4, USI-108, ZBH, ZB-11, ZBM-30, ZKQ-1B, and ZMQ-TB. Furthermore, as is known in the art, phosphorus compounds can be used to stabilize mesoporous ZSM-22. When used, the additional zeolite can be added in an amount between about 2 wt% and about 60 wt%.

[0028] The additive according to the invention can be added to the FCC unit together with the hydrocarbon feed, simultaneously with one or more catalysts, or after the hydrocarbon feed and one or more catalysts have been added. In one embodiment, the additive according to the invention is combined with one or more FCC catalysts. The catalyst composition is suitable for the catalytic cracking of hydrocarbon feedstocks and can efficiently produce light olefins while maintaining a low conversion rate. The catalyst composition can also be used in so-called DCC processes, even at lower temperatures than usual in DCC processes. Example

[0029] All reactions were carried out in a typical MAT reactor (fixed bed) at 520°C, connected to a gas GC (for analyzing the outflow gas) and equipped with a cryogenic liquid collector, after which the outflow gas was analyzed by GC. For a fixed feed, varying amounts of catalyst were introduced into the reactor. The feed consisted of an equal-weight blend of C5 to C7 olefins or a typical VGO crude oil feed. The olefin blend was used as a probe molecule because ZSM-5 primarily cracks olefins in the gasoline range to produce LPG. A typical FCC catalyst was steam-deactivated at 788°C in 100% steam for 20 hours to generate a deactivated FCC catalyst. The ZSM-5 additive was a commercial-grade additive from Albemarle and was used in the FCC catalyst in fresh or steam-deactivated form. ZSM-22 was used in fresh or steam-pure form, but was pressed and sieved to produce particles within the typical catalyst distribution. Feed test additives and ZSM-22 were used with and without an FCC catalyst. Products were analyzed by GC and yields were normalized.

[0030] The initial silica-to-alumina ratio (Si / Al) of ZSM-22 ranged from 25 to 40, and the ZSM-22 was tested both as is and after alkali / acid modification to create mesoporous structures. First, ZSM-22 was treated with an alkaline solution of 0.2 M caustic alkali at a liquid-to-solid ratio of 33:1 for 30 minutes at 65°C with stirring. After filtration and washing to remove excess sodium (to pH 7), the solid was suspended in oxalic acid solution (1 g zeolite to 2.5 g oxalic acid in 25.5 g water) at 70°C and held for two hours, followed by filtration and washing. The sample was calcined at 375°C for 3 hours and labeled as mesoporous-ZSM-22. Experimental results are shown in Tables 1 and 2 below. Figure 1 and Figure 2 middle.

[0031] Table 1 shows the selectivity data for C5-C6-C7 olefin cracking at 520 °C and 30 seconds TOS for mesoporous ZSM-22 and commercial ZSM-5. For this example, the methods described above were used to compare 0.3 g of mesoporous ZSM-22 and 1 g of commercial ZSM-5. The results clearly show that ZSM-22 exhibits higher selectivity for propylene while producing fewer aromatic compounds than the additive containing ZSM-5.

[0032] Table 1: Selectivity data for C5-C6-C7 olefin cracking at 520 °C and 30 seconds TOS for mesoporous ZSM-22 and commercial additives.

[0033] Refer to Table 2 and Figure 2 The graphs show the selectivity of propylene and aromatic compounds for FCC+commercial ZSM-5 and FCC+commercial ZSM-5+mesoporous-ZSM-22 used for cracking C5-C6-C7 olefins at 520 °C and 30 sec TOS. The two samples were compared using the methods described above. The data show how the combination of ZSM-22 with a typical FCC+ZSM-5-containing additive will produce higher amounts of propylene while generating fewer aromatic compounds.

[0034] Table 2: Selectivity data for C5-C6-C7 olefin cracking of FCC + commercial ZSM-5 blends with and without mesoporous ZSM-22 at 520 °C and 30 seconds TOS.

[0035] As used herein, the term "about" when modifying the amount of an ingredient in the compositions or methods of the invention refers to variations in numerical quantities that may occur, for example, typical measurement and liquid handling procedures used to prepare concentrates or to use solutions in the real world; negligent errors in these procedures; differences in the manufacture, origin, or purity of the ingredients used to prepare the compositions or to carry out the methods; and so on. The term "about" also covers amounts that differ due to different equilibrium conditions of the composition resulting from a particular initial mixture. Whether or not modified by the term "about," the claims include equivalents of the stated amounts.

[0036] Unless otherwise expressly stated, the article “a (or an)” as used herein is not intended to limit and should not be construed as limiting the description or claim of the single element referred to by the article. Rather, unless otherwise expressly stated in the text, if and as used herein, the article “a (or an)” is intended to cover one or more such elements. The invention is susceptible to considerable variation in its practice. Therefore, the foregoing description is not intended to limit the invention to and should not be construed as limiting it to the specific examples presented above.

Claims

1. An FCC additive comprising ZSM-22 zeolite, wherein the zeolite has been treated to increase the mesoporosity of the zeolite, the mesoporosity being as described by V 中孔 (cm 3 The zeolite, measured as / g), is used to increase propylene production, and the zeolite produces low-carbon aromatic compounds, wherein: The processing causes the V of the ZSM-22 to... 中孔 (cm 3 The concentration of ZSM-22 (g) increased by at least 1.5 times and the treated ZSM-22 had a concentration of at least 0.075 cm⁻¹. 3 / g of mesoporosity, the mesoporosity being measured as V 中孔 (cm 3 / g).

2. The FCC additive according to claim 1, wherein the treated ZSM-22 has a Si / Al ratio of 35.

3. The FCC additive according to claim 1, comprising ZSM-22 in an amount ranging from 5 wt% to 50 wt% based on the weight of the particles.

4. The FCC additive according to claim 1, further comprising a ZSM-5 zeolite in an amount ranging from 2 wt% to 60 wt% based on the weight of the particles.

5. The FCC additive according to claim 4, wherein the catalyst composition is a mixture of at least two particles, at least one first particle comprising the ZSM-22, and at least one second particle comprising the ZSM-5 zeolite.

6. The FCC additive according to claim 4, wherein the catalyst composition comprises particles in which the ZSM-22 and the ZSM-5 are present in the same particle.

7. Use of ZSM-22 zeolite in a method for catalytic cracking of organic compounds, wherein the zeolite has been treated to increase its mesoporosity, such as by V 中孔 (cm 3 The zeolite, measured as / g), is used to increase propylene production, and the zeolite produces low-carbon aromatic compounds, wherein: The processing causes the V of the ZSM-22 to... 中孔 (cm 3 The concentration of ZSM-22 (g) increased by at least 1.5 times and the treated ZSM-22 had a concentration of at least 0.075 cm⁻¹. 3 / g of mesoporosity, the mesoporosity being measured as V 中孔 (cm 3 / g).

8. The use according to claim 1, wherein the treated ZSM-22 has a Si / Al ratio of 35.

9. A method for producing propylene from a hydrocarbon feedstock, the method comprising the following steps: a. Provides an FCC catalyst composition comprising microparticles, said microparticles comprising ZSM-22, wherein said zeolite has been treated to increase the mesoporosity of said zeolite, said zeolite being in the range of 5 wt% to 50 wt% based on the weight of said microparticles, and said zeolite being used to increase propylene production and to produce low carbon number aromatic compounds, and wherein: said treatment reduces the V of said ZSM-22 中孔 (cm 3 The concentration of ZSM-22 (g) increased by at least 1.5 times and the treated ZSM-22 had a concentration of at least 0.075 cm⁻¹. 3 / g of mesoporosity, the mesoporosity being measured as V 中孔 (cm 3 / g); b. Contact the FCC particulate catalyst composition with the hydrocarbon feedstock at one or more temperatures in the range of 400°C to 650°C, wherein the residence time is in the range of 0.5 seconds to 12 seconds.

10. The method according to claim 9, wherein the treated ZSM-22 has a Si / Al ratio of 35.

11. The method of claim 9, wherein the catalyst additive further comprises a mixture of at least two particles, at least one first particle comprising the ZSM-22, and at least one second particle comprising the ZSM-5 zeolite.

12. The method of claim 9, wherein the catalyst additive further comprises particles in which the ZSM-22 and the ZSM-5 are present in the same particle.

13. The method of claim 9, wherein the contact in b) is carried out in a fluidized bed reactor.

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