Adsorbent for removing methanol or CO2 from hydrocarbon streams

Abstract

A process for removing methanol, CO2, or both from a hydrocarbon stream is described. The process uses an adsorbent comprising a binderless 3A type zeolite. The adsorbent has high methanol removal capacity and low olefin co-adsorption capacity, as well as low reactivity in the olefin stream. This allows for reduced adsorbent loading while maintaining downstream catalyst performance and product quality. The adsorbent comprises a 3A type zeolite comprised of less than 5% binder and an ion exchange ratio of 30%-70%. The adsorption process allows for an outlet methanol content of 1 ppmw or less to be obtained.

Description

Technical Field

[0001] (Priority Claim) This application claims priority to U.S. Provisional Patent Application No. 63 / 266,290, filed Dec. 31, 2021, which is hereby incorporated by reference in its entirety.

Background Art

[0002] The presence of methanol and / or CO2 in certain hydrocarbon streams can cause problems in downstream reactions. For example, methanol can react with catalysts in downstream processes, reducing catalyst performance. CO2 can cause plugging of equipment and reduction of catalyst performance. As a result, methanol must be removed from hydrocarbon streams to concentrations of less than 1 ppmw in some processes, for example.

[0003] Various techniques have been used to remove methanol from hydrocarbon streams, such as olefins. U.S. Patent No. 4,371,718 describes the use of activated alumina for removing methanol from hydrocarbon streams. Chinese Patent Nos. 105582885 and 105585405 describe the use of MFI / FAU / CHA type zeolites for removing methanol from hydrocarbon streams. Other zeolites such as modified 4A type zeolite, AZ-300 (a spherical alumina-zeolite composite available from UOP), and OG-491 (a 3A type alkali metal aluminosilicate available from UOP) have also been used. However, these methods have problems including low capacity, co-adsorption, and high reactivity in the case of olefins. Many different methods have been used to remove CO2 from hydrocarbons. Amine adsorption is widely used for CO2 removal. Carbon molecular sieves have also been used to separate CO2 and C2H4 due to the difference in diffusion / adsorption rates. However, carbon molecular sieves have low static adsorption selectivity and low strength, making it impossible to remove water simultaneously. Zeolites are not used to separate CO2 and C2H4 because their similar molecular size and properties make separation difficult.

[0004] Therefore, an improved method for separating methanol and CO2 from hydrocarbon flows is needed. [Brief explanation of the drawing]

[0005] [Figure 1] This graph compares the methanol vapor adsorption isotherms of the 3A-type zeolite adsorbent of the present invention and a commercially available 3A-type zeolite adsorbent. [Figure 2] This graph shows the adsorption isotherms of the 3A-type zeolite adsorbent of the present invention for methanol and ethylene. [Modes for carrying out the invention]

[0006] The present invention satisfies the need by providing an adsorbent containing a type 3A zeolite that can be used to remove methanol and CO2 from hydrocarbon streams. The adsorbent has a higher methanol removal capacity, a lower olefin co-adsorption capacity, and low reactivity in olefin streams. This allows for a reduction in the amount of adsorbent packed while maintaining downstream catalyst performance and product quality.

[0007] The adsorbent contains a type 3A zeolite with less than 5% binder. It may contain optional additives. In that case, the total amount of binder and additives must be less than 5%.

[0008] The adsorption process can produce an outlet methanol content of 10 ppmw or less, or 7 ppmw or less, or 5 ppmw or less, or 3 ppmw or less, or 1 ppmw or less.

[0009] The adsorption process can produce an outlet CO2 content of 10 ppmv or less, or 8 ppmv or less, or 6 ppmv or less, or 4 ppmv or less, or 2 ppmv or less.

[0010] Type 3A zeolite is a potassium-exchanged Linde type A (LTA) zeolite with the following chemical formula. mNa2O·nK2O·2.0 SiO2·Al2O3 Here, m+n=1. The pore opening is 3Å. When used as an adsorbent, zeolite-binder aggregates in the form of spheres or pellets with high mechanical abrasion resistance and strength are required. The binder content is at least 10%, and in most cases exceeds 15%. Considering the pore opening size of 3A zeolite and the molecular sieving properties of the zeolite, 3A zeolite has been mainly used as a dehydration adsorbent. Here, a binderless 3A zeolite adsorbent in which the binder was converted to zeolite was used.

[0011] 3A type zeolite can have a K ion exchange rate (K moles / (K moles + Na moles)) of 30% to 70%. For example, at an ion exchange rate of 30%, m=0.7 and n=0.3, and at an ion exchange rate of 60%, m=0.4 and n=0.6. When potassium is present at 30% to 60% in the cation exchange sites within the 3A zeolite adsorbent, the potassium content is in the range of 8% to 16% by weight of the 3A zeolite adsorbent, based on the standard of not containing volatile substances.

[0012] In some embodiments, the 3A type zeolite may have one or more of the following: a porosity of 20% to 40% (ASTM 4284-17); an ion exchange ratio of 30% to 60% (UOP 961-12 (available from ASTM International)). The porosity may be in the range of 15% to 50%, or 20% to 40%, or 20% to 35%. The ion exchange ratio may be in the range of 30% to 70%, or 30% to 60%, or 30% to 50%, or 35% to 70%, or 40% to 70%, or 40% to 60%.

[0013] In one embodiment, the adsorbent comprises a binder of less than 5% and a type 3A zeolite having a K ion exchange rate of 0.40-0.44 (K / K+Na). The elemental composition of molecular sieve samples was analyzed using X-ray fluorescence, inductively coupled plasma emission spectroscopy (ICP-OES), or both. The adsorbent can be used to remove methanol from hydrocarbons such as propene and isobutylene. The adsorption selectivity of methanol / C3H6 at 1 mmHg and 298 K is greater than 5000 mol / mol. The equilibrium adsorption capacity of methanol and C3H6 can be tested by physicoadsorption isotherms using an accelerated surface area and porosimetry system such as a Micromeritics'3 Flex Surface Characterization Analyzer or a BELSORP-max surface area and pore size distribution analyzer at 298 K. Adsorption selectivity was defined as the methanol / C3H6 adsorption capacity ratio. The adsorbent can also be used to remove CO2 from hydrocarbons such as ethylene. The adsorbent exhibits high CO2 / C2H4 selectivity. The CO2 / C2H4 adsorption selectivity at 250 mmHg is 23 mol / mol. The equilibrium adsorption capacities of CO2 and C2H4 can be tested by physicoadsorption isotherms using accelerated surface area and porosimetry systems at 298 K, such as Micromeritics'3 Flex Surface Characterization Analyzer or BELSORP-max surface area and pore size distribution analyzer. Adsorption selectivity was defined as the CO2 / C2H4 adsorption capacity ratio. This is significantly higher than the typical selectivity of carbon molecular sieves and other types of zeolite adsorbents. Furthermore, CO2 has a smaller molecular size (dynamic diameter 3.3 Å) and a higher affinity for zeolite-type adsorbents, both of which are beneficial for CO2 / C2H4 separation.

[0014] The CO2 capacity at 25°C and 250 mmHg is 4-7%. The C2H4 capacity at 25°C and 250 mmHg is 0.11%.

[0015] Adsorbents have a high water capacity. For example, at 25°C and 17.5 mmHg, the static water capacity may be in the range of 23-25%, and the dynamic water capacity may be greater than 18-20%. Typical 3A type zeolite has a static water capacity greater than 15-19%, but a dynamic water capacity greater than 13-14%.

[0016] The adsorbent can be manufactured by the following method: Binderless base 4A beads or pellets can be formed from a normal clay conversion process. A KCl solution can be used for ion exchange so that the K ion exchange rate of the final product is between 30% and 70%. The ion-exchanged 3A type zeolite can be dried to remove moisture to a range of 8-25%. The dried adsorbent is then calcined at a temperature of 400-750°C to obtain the finished adsorbent.

[0017] The adsorbent can be used in a purification unit that includes adsorption, desorption, and cooling. Adsorption is typically carried out at temperatures in the range of 15 to 50°C. Regeneration of the adsorbent is typically carried out at temperatures above 150°C under a gas containing but not limited to nitrogen, air, or methane. [Examples]

[0018] 3A zeolite was produced from binderless 4A zeolite. Binderless 4A zeolite was prepared by mixing an adsorbent aggregate consisting of 850 g of zeolite A and 150 g of an inert kaolin binder. 30 g of CMC was added during the aggregate formation process and formed into 8×12 mesh beads in an adhering beads forming apparatus. The formed aggregate was dried at 150 °C for 2 hours. The dried aggregate was fired by raising the temperature to 675 °C at a gradient of 5 °C / min and holding for 3 hours, converting the kaolin clay binder to a meta-kaolin clay binder. The material was cooled to 100 °C for packaging. The adsorbent was caustically warm-soaked at a temperature of 88 °C for 20 hours using 1.8N sodium hydroxide solution to convert the meta-kaolin binder to a binder-converted zeolite. The liquid was decanted and the solid was washed using deionized water at ambient temperature until the pH of the wash water was less than 11.

[0019] The binderless 4A zeolite adsorbent was exposed to 1N KCl solution at 45 °C and held for 8 hours for ion exchange to produce a 3A type binderless zeolite adsorbent.

[0020] The methanol adsorption capacity of the 3A zeolite adsorbent was measured using a physical adsorption isotherm and compared with several commercially available adsorbents.

[0021] Table 1 shows the comparison results of the methanol adsorption capacity.

[0022]

Table 1

[0023] The 3A zeolite adsorbent of the present invention has significantly higher methanol adsorption than commercially available adsorbents.

[0024] Figure 1 shows the comparison of the methanol vapor adsorption isotherms between the 3A zeolite adsorbent of the present invention and commercially available 3A zeolite adsorbents.

[0025] Figure 2 shows the adsorption isotherms of the 3A zeolite adsorbent of the present invention for methanol and ethylene. It has a high methanol adsorption capacity even at a low partial pressure, for example, 0.2 mmHg, and can achieve 12% by weight. In the case of ethylene, the adsorption capacity is only 0.15% by weight at 750 mmHg.

[0026] Specific embodiments The following will be described in conjunction with specific embodiments, but it should be understood that this description is illustrative of the scope of the foregoing description and the appended claims and is not intended to be limiting.

[0027] A first embodiment of the present invention is a process for removing methanol, CO2, or both from a hydrocarbon stream, comprising contacting a hydrocarbon stream containing hydrocarbons and methanol, CO2, or both with an adsorbent containing 3A-type zeolite to remove at least a portion of methanol, CO2, or both to produce a purified hydrocarbon stream containing methanol of 10.0 ppmw or less or CO2, or both, of 10.0 ppmv or less, wherein the 3A-type zeolite contains less than 5% of a binder and the process has an ion exchange ratio of 30% to 70%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment of this paragraph, wherein the hydrocarbon contains an olefin. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment of this paragraph, wherein the olefin contains ethylene or propene. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment of this paragraph, wherein the ion exchange rate of the 3A-type zeolite is 30% to 50%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the purified hydrocarbon stream contains methanol at a concentration of 1.0 ppmw or less. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the adsorbent has a porosity of 15% to 50%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the adsorbent further comprises additives. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the total amount of binder and additives is less than 5% by weight. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the contact is carried out at a temperature in the range of 15°C to 50°C. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the first embodiment, wherein the purified hydrocarbon stream contains CO2 at a concentration of 2.0 ppmv or less.

[0028] A second embodiment of the present invention is a process for removing methanol, CO2, or both from an ethylene or propene stream, comprising contacting an ethylene stream containing ethylene or a propene stream containing propene and methanol, CO2, or both, with an adsorbent containing a 3A zeolite to remove a portion of methanol, CO2, or both, to produce a purified ethylene or propene stream containing methanol at 1.0 ppmw or less, or CO2 at 10.0 ppmv or less, or both, wherein the 3A zeolite contains less than 5% of a binder and has an ion exchange ratio of 30% to 70%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the ion exchange ratio of the 3A zeolite is 30% to 50%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the purified ethylene or propene stream contains CO2 at 2.0 ppmv or less. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the adsorbent has a porosity of 15% to 50%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the adsorbent further comprises an additive. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the total amount of the binder and additive is less than 5% by weight. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the second embodiment of this paragraph, wherein the contact is carried out at a temperature in the range of 15°C to 50°C.

[0029] A third embodiment of the present invention is a composition comprising a type 3A zeolite comprising less than 5% of a binder, an ion exchange rate of 30% to 60%, and a porosity of 15% to 50%. Embodiments of the present invention are any or all of the earlier embodiments of this paragraph up to the third embodiment, wherein the ion exchange rate is 30% to 50%.

[0030] Without further detail, it is expected that those skilled in the art will be able to utilize the invention to the fullest extent without departing from the spirit and scope of the invention, readily identify its essential characteristics, and make various changes and modifications to the invention to suit various uses and conditions. Accordingly, the prior preferred specific embodiments should be construed as merely illustrative and not to limit the remainder of this disclosure in any way, but are intended to cover various modifications and equivalent configurations that fall within the scope of the appended claims.

[0031] In the above, all temperatures are given in degrees Celsius, and all parts and percentages are based on weight unless otherwise specified.

Claims

1. From hydrocarbon streams, methanol and CO2 ２ A process to remove either one or both. hydrocarbons and methanol, CO ２ A hydrocarbon stream containing either or both is brought into contact with an adsorbent containing 3A-type zeolite, thereby removing the methanol and CO2. ２ or remove at least a portion of both to obtain methanol with a concentration of 10.0 ppmv or less, or CO with a concentration of 10.0 ppmv or less. ２ The process involves generating a purified hydrocarbon stream containing, or both, wherein the 3A type zeolite contains less than 5% of a binder and has an ion exchange ratio of 30% to 70%. The aforementioned 3A type zeolite is potassium-exchanged Linde type A zeolite. process.

2. The process according to claim 1, wherein the 3A type zeolite has an ion exchange ratio of 30% to 50%.

3. The process according to any one of claims 1 to 2, wherein the adsorbent has a porosity of 15% to 50%.

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