Adsorbents 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] (Statement of priority) This application claims priority to U.S. Provisional Patent Application No. 63 / 266,290, filed December 31, 2021, which is incorporated by reference herein in its entirety. [Background technology]

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

[0003] Various techniques have been used to remove methanol from hydrocarbon streams such as olefins. US Patent No. 4,371,718 describes the use of activated alumina to remove methanol from hydrocarbon streams. CN Patent No. 105582885 and CN Patent No. 105585405 describe the use of MFI / FAU / CHA type zeolites to remove methanol from hydrocarbon streams. Other zeolites such as modified 4A type zeolites, AZ-300 (spherical alumina-zeolite composite available from UOP), and OG-491 (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. Adsorption with amines has been widely used for CO2 removal. Carbon molecular sieves have also been used to separate CO2 and C2H4 due to differences in diffusion / adsorption rates. However, carbon molecular sieves have low static adsorption selectivity and low strength, so they cannot simultaneously remove water. Zeolites have not been used to separate CO2 and C2H4 because their similar molecular sizes and properties make the separation difficult to achieve.

[0004] Therefore, there is a need for improved methods for separating methanol and CO2 from hydrocarbon streams. [Brief description of the drawings]

[0005] [Figure 1] 1 is a graph comparing the methanol vapor adsorption isotherms of the 3A zeolite adsorbent of the present invention and a commercially available 3A zeolite adsorbent. [Diagram 2] 1 is a graph showing the adsorption isotherms of methanol and ethylene for the 3A zeolite adsorbent of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The present invention fills that need by providing an adsorbent comprising 3A type zeolite that can be used to remove methanol and CO2 from hydrocarbon streams. The adsorbent has higher 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.

[0007] The adsorbent comprises 3A zeolite with less than 5% binder, and may contain optional additives, in which case the combined amount of binder and additive is less than 5%.

[0008] The adsorption process can obtain 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 obtain 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] Zeolite type 3A is a potassium-exchanged Linde type A (LTA) zeolite having the following chemical formula: mNa2O nK2O 2.0 SiO2 Al2O3 where m+n=1. The pore opening is 3 Å. When used as an adsorbent, zeolite-binder aggregates as 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 zeolite, 3A zeolite was mainly used as a dehydration adsorbent. Here, a binderless 3A zeolite adsorbent was used, in which the binder was converted into zeolite.

[0011] 3A 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, n=0.3, and at an ion exchange rate of 60%, m=0.4, n=0.6. When potassium is present at cation exchangeable sites in the 3A zeolite adsorbent at 30% to 60%, the potassium is in the range of 8% to 16% by weight of the 3A zeolite adsorbent on a volatile material-free basis.

[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 range from 15% to 50%, or 20% to 40%, or 20% to 35%. The ion exchange ratio may range from 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 3A type zeolite with less than 5% binder and K ion exchange ratio of 0.40-0.44 (K / K+Na). The elemental composition of the molecular sieve samples was analyzed using X-ray fluorescence, inductively coupled plasma optical 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 physical adsorption isotherm using an accelerated surface area and porosimetry system such as Micromeritics'3 Flex Surface Characterization Analyzer or BELSORP-max Surface Area and Pore Size Distribution Analyzer at 298 K. The adsorption selectivity was defined as the adsorption capacity ratio of methanol / C3H6. The adsorbent can also be used to remove CO2 from hydrocarbons such as ethylene. The adsorbent has high CO2 / C2H4 selectivity. The adsorption selectivity of CO2 / C2H4 at 250 mmHg is 23 mol / mol. The equilibrium adsorption capacity of CO2 and C2H4 can be tested by physical adsorption isotherm using an accelerated surface area and porosimetry system at 298 K, such as Micromeritics'3 Flex Surface Characterization Analyzer or BELSORP-max surface area and pore size distribution analyzer. The adsorption selectivity was defined as the adsorption capacity ratio of CO2 / C2H4. It is much higher than the typical selectivity of carbon molecular sieves and other types of zeolite adsorbents. In addition, 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 250mmHg is 4-7%. The C2H4 capacity at 25°C and 250mmHg is 0.11%.

[0015] The adsorbent has 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%. A typical 3A zeolite has a static water capacity of greater than 15-19%, but a dynamic water capacity of greater than 13-14%.

[0016] The adsorbent can be manufactured by the following methods. Binderless base 4A beads or pellets can be formed from a conventional clay conversion process. 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 the 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 ranging from 15 to 50° C. Regeneration of the adsorbent is typically carried out at temperatures above 150° C. under gases including, but not limited to, nitrogen, air, or methane. EXAMPLES

[0018] 3A zeolite was produced from binderless 4A zeolite. Binderless 4A zeolite was made by mixing adsorbent aggregates consisting of 850 g of zeolite A and 150 g of inert kaolin binder. 30 g of CMC was added during the aggregate formation process, which was formed into 8×12 mesh beads in a deposition bead former. The formed aggregates were dried at 150° C. for 2 hours. The dried aggregates were calcined by ramping the temperature to 675° C. at a 5° C. / min ramp and holding for 3 hours to convert the kaolin clay binder to meta-kaolin clay binder. The material was cooled to 100° C. for packaging. The adsorbent was caustic digested with 1.8 N sodium hydroxide solution at a temperature of 88° C. for 20 hours to convert the metakaolin binder to binder-converted zeolite. The liquid was decanted and the solids were washed with ambient temperature deionized water 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 the 3A type binderless zeolite adsorbent.

[0020] The methanol adsorption capacity of 3A zeolite adsorbent was measured using physical adsorption isotherms 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] FIG. 1 shows the methanol vapor adsorption isotherm comparison between the 3A zeolite adsorbent of the present invention and a commercial 3A zeolite adsorbent.

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

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

[0027] A first embodiment of the invention is a process for removing methanol, CO2 or both from a hydrocarbon stream comprising contacting a hydrocarbon stream comprising a hydrocarbon and methanol, CO2 or both with an adsorbent comprising a type 3A zeolite to remove at least a portion of the methanol, CO2 or both to produce a purified hydrocarbon stream comprising 10.0 ppmw or less of methanol or 10.0 ppmv or less of CO2 or both, wherein the type 3A zeolite comprises less than 5% binder and has an ion exchange ratio of 30% to 70%. An embodiment of the invention is one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the hydrocarbon comprises an olefin. An embodiment of the invention is one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the olefin comprises ethylene or propene. An embodiment of the invention is one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, wherein the ion exchange ratio of the type 3A zeolite is 30% to 50%. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the refined hydrocarbon stream comprises 1.0 ppmw or less of methanol. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the adsorbent has a porosity of 15% to 50%. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the adsorbent further comprises an additive. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the total amount of binder and additive is less than 5 wt%. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the contacting is performed at a temperature in the range of 15° C. to 50° C. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph through the first embodiment of this paragraph, in which the refined hydrocarbon stream comprises 2.0 ppmv or less of CO2.

[0028] A second embodiment of the invention is a process for removing methanol, CO2, or both from an ethylene or propene stream comprising contacting an ethylene stream comprising ethylene or a propene stream comprising propene and methanol, CO2, or both with an adsorbent comprising a type 3A zeolite to remove a portion of the methanol, CO2, or both to produce a purified ethylene or propene stream comprising 1.0 ppmw or less of methanol, or 10.0 ppmv or less of CO2, or both, wherein the type 3A zeolite comprises less than 5% binder and has an ion exchange ratio of 30% to 70%. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the ion exchange ratio of the type 3A zeolite is 30% to 50%. An embodiment of the invention is one, any, or all of the preceding embodiments of this paragraph through the second embodiment of this paragraph, wherein the purified ethylene or propene stream comprises 2.0 ppmv or less of CO2. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph up to the second embodiment of this paragraph, where the adsorbent has a porosity of 15% to 50%. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph up to the second embodiment of this paragraph, where the adsorbent further comprises an additive. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph up to the second embodiment of this paragraph, where the total amount of binder and additive is less than 5 wt. An embodiment of the invention is any one, any or all of the preceding embodiments of this paragraph up to the second embodiment of this paragraph, where the contacting is performed 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 3A zeolite consisting of less than 5% binder, an ion exchange rate of 30% to 60%, and a porosity of 15% to 50%. An embodiment of the present invention is one, any, or all of the previous embodiments of this paragraph up to the third embodiment of this paragraph, in which the ion exchange rate is 30% to 50%.

[0030] Without further elaboration, it is believed that, using the preceding description, one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of the present invention without departing from the spirit and scope of the present invention, and can make various changes and modifications to the present invention to adapt it to various uses and conditions. The preceding preferred specific embodiments are therefore to be construed as merely illustrative, and are not limitative of the remainder of the disclosure in any way, but are intended to cover various modifications and equivalent arrangements falling within the scope of the appended claims.

[0031] Above, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise stated.

Claims

1. Hydrocarbon streams to methanol, CO ２ or both, Hydrocarbons and the methanol, the CO ２ or both, contacting a hydrocarbon stream containing methanol, CO, or both with an adsorbent comprising a 3A type zeolite to remove the methanol, CO, or both. ２ or at least a portion of both to obtain 10.0 ppmv or less of methanol or 10.0 ppmv or less of CO ２ or both, wherein the Type 3A zeolite contains less than 5% binder and has an ion exchange ratio of 30% to 70%.

2. The process of claim 1 , wherein the hydrocarbon comprises an olefin.

3. 3. The process of claim 2 wherein the olefin comprises ethylene or propene.

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

5. The refined hydrocarbon stream has 1.0 ppmv or less of methanol or 2.0 ppmv or less of CO ２ or both.

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

7. The process of any one of claims 1 to 2, wherein the sorbent further comprises an additive.

8. 8. The process of claim 7, wherein the total amount of said binder and said additives is less than 5% by weight.

9. The process of any one of claims 1 to 2, wherein the contacting is carried out at a temperature in the range of from 15°C to 50°C.

10. An adsorbent comprising: An adsorbent comprising a 3A type zeolite consisting of less than 5% binder, an ion exchange rate of 30% to 60%, and a porosity of 15% to 50%.

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