Catalyst for Producing Light Olefins From C4-C7 Hydrocarbons

Abstract

The present invention relates to a catalyst for producing light olefins from C4-C7 hydrocarbons from catalytic cracking reaction and the production process of light olefins from said catalyst, wherein said catalyst has core-shell structure comprising a zeolite core with mole ratio of silicon to aluminium (Si/Al) between 2 to 250 and layered double hydroxide shell (LDH). The catalyst according to the invention provides high percent conversion of substrate to products and high selectivity to light olefins product.

Claims

1. A catalyst for producing light olefins from C4-C7 hydrocarbons, wherein said catalyst has a core-shell structure comprising a zeolite core with mole ratio of silicon to aluminium (Si/Al) between 2 to 250 and a layered double hydroxide shell and said zeolite is a hierarchical zeolite.

2. The catalyst according to claim 1, wherein said zeolite is the hierarchical zeolite comprising a micropore with size between 0.3 to 0.6 nm, a mesopore with size between 2 to 10 nm, and a macropore with size larger than 50 nm, wherein the mesopore and macropore proportions are greater than or equal to 15 to 60% when compared to a total pore volume.

3. The catalyst according to claim 1, wherein said zeolite has the mole ratio of silicon to aluminium between 15 to 30.

4. The catalyst according to claim 3, wherein said zeolite has the mole ratio of silicon to aluminium of equal to 15.

5. The catalyst according to claim 1, wherein said zeolite is selected from zeolite types ZSM-5, FAU, MOR, BETA or FER.

6. The catalyst according to claim 1, wherein the core of said zeolite has a crystal size between 100 to 3,000 nm.

7. The catalyst according to claim 1, wherein said layered double hydroxide comprises main compositions which are the group 2 metals and the group 3 metals.

8. The catalyst according to claim 7, wherein said layered double hydroxide comprises the main compositions which are magnesium (Mg) and aluminium (Al).

9. The catalyst according to claim 1, wherein said layered double hydroxide has a mole ratio of magnisium to aluminium between 1 to 3.

10. The catalyst according to claim 9, wherein said layered double hydroxide has the mole ratio of magnisium to aluminium between 1 to 2.

11. The catalyst according to claim 1, wherein said layered double hydroxide has a thickness between 100 to 1,000 nm.

12. The catalyst according to claim 1, wherein said catalyst comprises a core and a shell which has a mass ratio of shell: core between 1:1 to 1:7.

13. The catalyst according to claim 1, wherein said catalyst comprises the core and the shell which has the mass ratio of shell: core between 1:2 to 1:6.

14. A production process of light olefins from catalytic cracking reaction of C4-C7 hydrocarbons using the catalyst according to claim 1.

15. The process according to claim 14, wherein said process is operated at temperature between 450 to 650° C. and pressure between atmospheric pressure 1 to 5 bars.

16. The process according to claim 14 or 15, wherein the hydrocarbon compound is selected from butane, pentane, hexane, or heptane.

17. The process according to claim 16, wherein the hydrocarbon compound is pentane.

18. The process according to any one of claims 2 to 17, wherein products are light olefins.

19. The process according to claim 18, wherein the preferable products are ethylene and propylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 shows the crystal characters of the samples according to the invention and the comparative samples.

[0015] FIG. 2 A) and B) show the results from the electron scanning microscope and the electron transmission microscope of the sample according to the invention Cat 2.

[0016] FIG. 3 shows the composition percentage of the elements changed according to the crystal size by the X-ray photoelectron spectroscopy (XPS) for the sample according to the invention Cat 2.

[0017] FIG. 4 A) and B) show the light olefins product selectivity of the samples according to the invention Cat 1 and Cat 2 across times for the catalytic cracking of pentane respectively.

[0018] FIG. 5 shows the percentage of light olefins product selectivity of the samples according to the invention and the comparative samples for the catalytic cracking of pentane.

[0019] FIG. 6 shows the percentage of light olefins product yield of the samples according to the invention and the comparative samples for the catalytic cracking of pentane.

[0020] FIG. 7 shows the percentage of products selectivity of the samples according to the invention and the comparative samples for the catalytic cracking of pentane.

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates to the catalyst for producing light olefins from C4-C7 hydrocarbons which will be described according to the following embodiments.

[0022] Any aspect that being described here is meant to include the application to the other aspects of this invention, unless stated otherwise.

[0023] Technical terms or scientific terms used here have definitions as by person skilled in the art unless stated otherwise.

[0024] Any tools, equipment, methods, or chemicals named here mean tools, equipment, methods, or chemicals being used commonly by person skilled in the art unless stated otherwise that they are tools, equipment, methods, or chemicals specific only in this invention.

[0025] Use of singular noun or singular pronoun with “comprising” in claims or specification means “one” and including “one or more”, “at least one”, and “one or more than one” too.

[0026] All compositions and/or methods disclosed and claims in this application aim to cover embodiments from any action, performance, modification, or adjustment without any experiment that significantly different from this invention, and obtain with object with utility and resulted as same as the present embodiment according to person ordinary skilled in the art although without specifically stated in claims. Therefore, substitutable or similar object to the present embodiment, including any little modification or adjustment that clearly seen by person skilled in the art should be construed as remains in spirit, scope, and concept of invention as appeared in appended claims.

[0027] Throughout this application, term “about” means any number that appeared or showed here that could be varied or deviated from any error of equipment, method, or personal using said equipment or method.

[0028] Hereafter, invention embodiments are shown without any purpose to limit any scope of the invention.

[0029] This invention relates to the catalyst for producing light olefins from C4-C7 hydrocarbons from the catalytic cracking and the production process of olefins using said catalyst, wherein said catalyst has core-shell structure comprising zeolite core with mole ratio of silicon to aluminium between 2 to 30, and layered double hydroxide shell.

[0030] In one embodiment, the zeolite core is the hierarchical zeolite comprising a micropore with size between 0.3 to 0.6 nm, a mesopore with size between 2 to 10 nm, and a macropore with size more than 50 nm, wherein the mesopore and macropore proportions are 15 to 60% or more based in total pore volume.

[0031] In one embodiment, the mole ratio of silicon to aluminium of said zeolite is between 2 to 250. Preferably, the mole ratio of silicon to aluminium of said zeolite is between 15 to 30. Most preferably, the mole ratio of silicon to aluminium of said zeolite is 15.

[0032] In one embodiment, said zeolite is selected from ZSM-5 FAU MOR BETA or FER zeolite, preferably is ZSM-5.

[0033] In one embodiment, the crystal size of said zeolite is between 100 to 3,000 nm.

[0034] In one embodiment, the layered double hydroxide comprising the group 2 metals and the group 3 metals as the main compositions, preferably are magnesium (Mg) and aluminium (Al).

[0035] In one embodiment, the mole ratio of magnesium to aluminium of said layered double hydroxide is between 1 to 3. Preferably, the mole ratio is between 1 to 2.

[0036] In one embodiment, the thickness of said layered double hydroxide is between 100 to 1,000 nm.

[0037] Preferably, the catalyst according to the invention comprising hierarchical zeolite core and layered double hydroxide shell which comprising magnesium and aluminium, wherein said catalyst has a mass ratio of shell to core between 1:1 to 1:7, preferably is 1:2 to 1:6.

[0038] In another embodiment, the catalyst according to the invention has been improved in its property for the production of light olefins such as the product selectivity, the production yield, and the conversion from precursor to light olefins product, also comprising IIA, IIIA, VA, IIB, IIIB, VIB, and VIII metal group according to the periodic table of elements, which may be selected from but not limited to lanthanum, strontium, palladium, phosphorus, platinum, gallium, or zinc.

[0039] In one embodiment, the catalyst according to the invention may be prepared according to the following steps:

[0040] (a) preparing a solution comprising a compound for the preparation of zeolite and a soft template;

[0041] (b) subjecting the mixture obtained from step (a) to the hydrothermal process at the determined temperature and time in order to convert said mixture into the hierarchical zeolite;

[0042] (c) preparing a solution comprising a compound for preparing layered double hydroxide shell;

[0043] (d) preparing the solution comprising the zeolite obtained from step (b) and sodium carbonate;

[0044] (e) dropping the solution prepared from step (c) onto the solution prepared from step (d) while controlling pH of the solution;

[0045] (f) stirring the mixture obtained from step (e) for about 1 hour and washing with deionized water under stirring condition continuously for about another 1 hour, then washing with acetone under stirring condition continuously for about 10 to 14 hours;

[0046] (g) centrifuging the mixture washed with acetone obtained from step (f) in order to separate the synthesized catalyst;

[0047] (h) drying the catalyst obtained from step (g); and

[0048] (i) contacting the obtained sample with ammonium nitrate (NH.sub.4NO.sub.3) solution by ion exchange method using 100 mL of ammonium nitrate solution to 1 g of the catalyst at the temperature of 80° C. for about 2 hours, then drying and repeating 3 times, and finally calcining at the temperature of 550° C. for about 6 to 8 hours.

[0049] characterized in that the soft template in step (a) is a quaternary ammonium salt that may be selected from but not limited to tetraalkyl ammonium salt selected from tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

[0050] In one embodiment, the compound used for preparing zeolite is a mixture of the alumina compound selected from aluminum isopropoxide, sodium aluminate, or aluminium sulfate, and the silica compound selected from tetraethyl orthosilicate, sodium silicate, or silica gel.

[0051] In one embodiment, step (b) is operated at the temperature between 130 to 180° C. In another embodiment, the preparation process of the catalyst according to the invention may further comprising the drying and calcining steps.

[0052] Drying may be performed by normal drying using oven, vacuum drying, stirred drying, and rotary evaporator.

[0053] Calcination may be performed under atmospheric condition for about 4 to 10 hours and temperature between about 350 to 650° C., preferably is for about 5 to 6 hours and temperature between about 350 to 400° C.

[0054] In another embodiment, the present invention relates to the use of the catalyst according to the invention in the production process of light olefins from catalytic cracking of C4-C7 hydrocarbons.

[0055] In one embodiment, the catalytic cracking of C4-C7 hydrocarbons may be occurred wherein the feeding of C4-C7 hydrocarbons is contacted with the catalyst according to the invention at the suitable conditions for the reaction which may be operated in fixed bed system.

[0056] The catalytic cracking of C4-C7 hydrocarbons may be occurred at the temperature between about 450 to 650° C., preferably is between about 550 to 600° C. under atmospheric pressure to 5 bars, most preferably is at the atmospheric pressure.

[0057] In one embodiment, the C4-C7 hydrocarbons is selected from butane, pentane, hexane, or heptane, preferably is pentane.

[0058] In one embodiment, the product obtained from the catalytic cracking of C4-C7 hydrocarbons using said catalyst is the light olefins, preferably are ethylene and propylene.

[0059] The weight hourly space velocity (WHSV) of the feeding of the hydrocarbon compound in the catalytic cracking is between about 1 to 50 hours.sup.−1, preferably is between about 2 to 7 hours.sup.−1.

[0060] Normally, the persons skilled in the art can modify the reaction conditions of the catalytic cracking of C4-C7 hydrocarbons to be suitable for type and composition of the feeding, the catalyst, and the reactor system.

[0061] The following example is only for demonstrating the embodiments of this invention, not for limiting the scope of this invention in any way.

[0062] Preparation of the Catalyst

[0063] The preparation of the catalyst can be performed according to the following methods.

[0064] Preparation of the Zeolite Core

[0065] The solution comprising sodium aluminate and tetraethyl orthosilicate was prepared, wherein the mole ratio of silicon to aluminum was 15. Tetrapropyl ammonium hydroxide was used as the template of zeolite. Then, the obtained mixture was subjected to hydrothermal process at the temperature about 130-180° C. for about 2 to 4 days in order to convert said mixture into zeolite. Then, the obtained zeolite was washed with deionized water until the pH was lower than 9. The obtained substance was dried at the temperature about 100 to 120° C. for about 12 to 24 hours. Then, the calcination was performed in order to remove the template at the temperature about 500 to 650° C. for about 8 to 12 hours. The hierarchical zeolite was obtained as white powder.

[0066] Preparation of Layered Double Hydroxide Shell

[0067] The precursor solution of the layered double hydroxide comprising 2.4 to 4.8 mmol of magnesium nitrate and 1.2 to 2.4 mmol of aluminium nitrate was prepared. Then, the prepared solution was dropped onto the mixture comprising 0.2 to 0.5 g of sodium carbonate and 0.5 g of determined type of zeolite. The pH was controlled to be about 10.

[0068] Then, said mixture was stirred for about 1 hour and washed with deionized water. Then, acetone was added and stirred for 10 to 14 hours. Finally, the mixture was dried in vacuum oven according to the method disclosed by Chunping et al. (Chemical Science, 2016, 7(2), 1457-61).

[0069] Then, the ion exchange was performed on the catalyst of the mixture material of zeolite and layered double hydroxide synthesized from sodium ion into proton ion by ion exchanged method. The obtained catalyst of the mixture material of zeolite and layered double hydroxide was dissolved in 0.1 molar of ammonium nitrate (NH.sub.4NO.sub.3) solution at the temperature about 80° C., stirred for about 2 hours, and washed with pure water. The obtained zeolite was dried. Then, the obtained zeolite was calcined in order to remove contaminants at the temperature about 350° C. for about 6 hours.

[0070] Comparative Sample Cat A (Com ZSMS)

[0071] The ZSM-5 nano-zeolite having mole ratio of silicon to alumina of 15 that was commercially available was used as the comparative sample Cat A.

[0072] Comparative Sample Cat B (ZSMS)

[0073] The sample according to the invention Cat B was prepared by the method described in the preparation of the zeolite core above.

[0074] Comparative Sample Cat C (ComZSM5-Mg-Al(imp))

[0075] The comparative sample Cat C was prepared by contacting the comparative sample A with the magnesium and aluminium salt solution by impregnation method using 10 mL of magnesium nitrate and aluminium nitrate at the concentration from 0.4 to 1 molar at the temperature of 80° C. for 1 to 3 hours. Then, it was dried by rotary evaporator and dried in oven at the temperature of 100° C. for 24 hours. Then, sample was calcined at the temperature of 350° C. for 6 hours.

[0076] Sample According to the Invention Cat 1 (ComZSM5-LDH(ex))

[0077] The sample according to the invention Cat 1 was prepared by subjecting the comparative sample Cat A as core and prepared by the preparation method of catalyst according to the invention as described above in order to obtain the catalyst having zeolite core and layered double hydroxide shell.

[0078] Sample According to the Invention Cat 2 (ZSMS-LDH(ex))

[0079] The sample according to the invention Cat 2 was prepared by subjecting the comparative sample Cat B as core and prepared by the preparation method of catalyst according to the invention as described above in order to obtain the catalyst having zeolite core and layered double hydroxide shell.

[0080] Testing of Catalytic Cracking of C4-C7 Hydrocarbons for Producing Light Olefins Product

[0081] The testing of catalytic cracking of C4-C7 hydrocarbons for the production of light olefins might be performed in the following conditions.

[0082] The catalytic cracking was operated in fixed-bed reactor by using about 0.2 to 0.4 g of catalyst. Before the reaction, the catalyst was contacted with nitrogen gas with flow rate about 10 to 50 ml/min for about 1 to 3 hours. Then, the C5 hydrocarbon compound was fed at the flow rate about 1.25 g/h. The reaction was continued at the temperature about 500 to 600° C. at the atmospheric pressure and the weight hourly space velocity (WHSV) was about 2 to 5 hour.sup.1.

[0083] Then, the reaction was monitored by measuring the changes of precursor and the formations of other compositions after reacted with the catalyst at any time using gas chromatography connected to the output of the fixed-bed reactor using flame ionization detector (FID) as the detector, and GASPRO capillary column for the analysis of each composition of said substance.

[0084] FIG. 1 shows the crystal characters of the samples according to the invention and the comparative samples that show the core and shell structure of zeolite and layered double hydroxide of the samples according to the invention Cat 1 and Cat 2.

[0085] Furthermore, in order to show the crystal characters, the scanning electron microscope (SEM) and transmission electron microscopy (TEM) were employed. The results were showed in FIG. 2, which demonstrate that the zeolite according to the invention was hierarchical zeolite with the crystal size about 100 to 3,000 nm. From the test of a specific surface area of the micropore, mesopore, and macropore, it was found that both catalyst Cat A and Cat B had the size distribution of micropore, mesopore, and macropore, wherein the proportion of mesopore and macropore were greather than or equal to 15 to 60% when comparing to the total pore volume. Moreover, the hierarchical factor (HF) of the catalyst Cat A and Cat B was about 0.04. This shows that both catalysts had the hierarchical structure. The hierarchical factor can be calculated from the following equation.

Hierarchical factor (HF)=Micropore volume (Vmicro)(cm.sup.3/g)/Total pore volume (Vtotal)(cm.sup.3/g)×Specific external surface area (Sext)(m.sup.2/g)/Specific surface area (SBET)(m.sup.2/g)

[0086] Hence, in order to confirm the core-shell structure of zeolite and layered double hydroxide of the samples according to the invention, the percentage concentration of magnesium and silicon that changed according to the crystal size were analyzed by X-ray photoelectron spectroscopy (XPS). The results were shown in FIG. 3.

[0087] In order to study the effect of the catalyst containing the hierarchical zeolite core and the layered double hydroxide shell to the production efficiency of light olefins from catalytic cracking of C4-C7 hydrocarbons, the catalysts according to the invention were studied with the comparative samples. The results were shown in FIG. 4 to FIG. 7.

[0088] FIG. 4 shows the efficiency of light olefins product selectivity of the samples according to the invention that changed across the time. It was found that the catalyst according to the invention gave better efficiency than the comparative sample, wherein the sample according to the invention Cat 2 showed the highest pentane conversion and having higher light olefins product selectivity than other types of catalyst.

[0089] FIG. 5 shows the efficiency of light olefins product selectivity of the samples according to the invention and the comparative samples. It was found that the catalyst according to the invention gave better efficiency than the comparative samples, wherein sample according to the invention Cat 2 showed the higher pentane conversion and having higher light olefins product selectivity than other types of catalyst.

[0090] FIG. 6 shows the efficiency of light olefins product yield of the samples according to the invention and the comparative samples. It was found that the catalyst according to the invention gave better efficiency than the comparative samples, wherein the sample according to the invention Cat 2 showed the higher pentane conversion and having higher percent yield of light olefins product than other types of catalyst.

[0091] FIG. 7 shows the efficiency of the products selectivity of the samples according to the invention and the comparative samples. It was found that sample according to the invention Cat 2 showed the higher pentane conversion and having higher light olefins product selectivity than other types of catalyst, including having lower light alkane product selectivity.

[0092] From the results above, it can be said that the catalyst comprising the hierarchical zeolite core and the layered double hydroxide shell according to the invention gave high percent conversion of light olefins product yield and selectivity for the catalytic cracking of C4-C7 hydrocarbons as stated in the objective of this invention.

BEST MODE OF THE INVENTION

[0093] Best mode of the invention is as provided in the detailed description of the invention.