Method for molecular sieve shaping by using rice husk as template

Abstract

A method for using a molecular sieve shaped by rice husks as a template is provided. A method using a molecular sieve shaped by rice husks as a catalyst for a thermal cracking reaction for stearic acid is provided. A method for manufacturing a molecular sieve incorporating rice husks, the method includes the following steps. (1) mixing molecular sieve powder containing rice husks, a binder, and an extrusion aid to be homogeneous, then adding a peptizer, and mixing to be homogeneous to obtain a uniform mixture; (2) introducing water to the uniform mixture, mixing to be homogeneous, and performing a kneading process to shape a sticky conglomerate; (3) extruding the sticky conglomerate obtained in the step (2) with an extrusion device to obtain moist strips; and (4) drying, calcining, and shaping the moist strips obtained in the step (3) to obtain the molecular sieve incorporating the rice husks.

Claims

1. A method for preparing a molecular sieve comprising the following steps: (1) mixing ZSM-5 molecular sieve powder incorporated with rice husks, a binder, and an extrusion aid with weight percentages of 72-75%: 7-25%: 2-20% to be homogeneous, then adding a peptizer, and mixing to be homogeneous, an amount of the peptizer is 1-3 wt % of a total weight of a mixture of the ZSM-5 molecular sieve powder incorporated with the rice husks, the binder, and the extrusion aid, wherein a method for preparing the ZSM-5 molecular sieve powder incorporated with the rice husks comprises: mixing water, a tetrapropylammonium hydroxide solution with a concentration of 40 wt %, sodium metaaluminate, tetraethyl orthosilicate, and the rice husks to be homogeneous in sequence with a weight ratio of 79:46:1:77:15; subjecting to a hydrothermal reaction at 170 C. for 24 hours to yield an obtained sample; and washing the obtained sample with deionized water and ethanol, subjecting to centrifugation, drying at a constant temperature of 80 C., and then calcining in a muffle furnace at 550 C. for 6 hours at a heating rate of 5 C. per minute; (2) introducing water to the material obtained in the step (1), mixing to be homogenous, and performing a kneading process to form a sticky conglomerate; (3) extruding the sticky conglomerate obtained in the step (2) with an extrusion device to obtain moist strips; and (4) drying, calcining, and shaping the moist strips obtained in the step (3).

2. The method according to claim 1, wherein an amount of the water introduced in the step (2) is 32-34 wt % of a total weight of the material obtained in the step (1).

3. The method according to claim 1, wherein, in the step (4), the drying and the calcining comprises drying at 79-82 C. for 100-120 minutes and calcining the moist strips at 400-800 C. for 4-8 hours after heating the moist strips at a heating rate of 10-20 C. per minute.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a flow chart of the process of the present disclosure.

(2) FIGS. 2A and 2D illustrate scanning electron microscope (SEM) images of a formation of a nanoscale molecular sieve formation in the absence of the rice husks, FIGS. 2B and 2E illustrate SEM images of a nanoscale molecular sieve formation with the rice husks, FIGS. 2C and 2F illustrate SEM images of a microscale molecular sieve formation with the rice husks, and FIG. 2G illustrates the nano-scale molecular sieve formation with the rice husks.

(3) FIG. 3 illustrates a comparison of the selectivity of pure nanoscale molecular sieve and the nanoscale molecular sieve containing rice husks that function as thermal cracking catalysts for stearic acid.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) The technical solution of the present disclosure will be further described and illustrated below in combination with the accompanying drawings and embodiments.

Comparative Embodiment 1

(5) (1) A method for preparing Zeolite Socony Mobil-5 (ZSM-5) powder involves a sequential mixing of water, a tetrapropylammonium hydroxide solution (with a 40% concentration of tetrapropylammonium hydroxide by weight), sodium metaaluminate, and tetraethyl orthosilicate in a weight ratio of 79:46:1:77 to obtain a first mixture, and the first mixture is then subjected to a high-temperature hydrothermal reaction at 170 C. for 24 hours to produce a sample. The sample is washed with deionized water, centrifuged, dried at 80 C., and finally calcined in a muffle furnace at 550 C. for 6 hours after heating at a heating rate of 5 C. per minute. (2) 73.5 wt % of the ZSM-5 powder, 24.5 wt % of binder (pseudo-boehmite), and 2 wt % of extrusion aid (sesbania) are mixed to be homogeneous, and a peptizer (nitric acid) with 3 wt % of a total weight of a second mixture of the ZSM-5 powder, the binder, and the extrusion aid is then added and mixed to be homogeneous by a stirring rod or a mixer to produce a uniform mixture. Water equivalent to 32.5 wt % of the uniform mixture is added to the uniform mixture and mixed to be homogeneous, and a kneading process is performed for 20 minutes with a kneader to form a sticky conglomerate. (3) The sticky conglomerate obtained in the step (2) is extruded into moist strips by an extrusion device with an extrusion rotation speed of the extruder adjusted to 50 revolutions/minute. The moist strips rest at room temperature (e.g., 20-25 C.) for 20 minutes and are cut to a uniform length of 6 mm. (4) The moist strips obtained in the step (3) are dried at 80 C. for 120 minutes, calcined at 670 C. for 6 hours after being heated with a heating rate of 13 C./minute, and then polished into regular cylindrical forms with dimensions of 53 mm for testing. A process for shaping a molecular sieve of the ZSM-5 is shown in FIG. 1.

Embodiment 1

(6) A flow chart illustrating a process of this embodiment is shown in FIG. 1. In the step (2), The ZSM-5 powder is replaced with the ZSM-5 powder containing rice husks (as a template). A method for shaping the ZSM-5 powder containing the rice husks is as follows: water, tetrapropylammonium hydroxide solution with a 40% concentration of tetrapropylammonium hydroxide by weight, sodium metaaluminate, tetraethyl orthosilicate, and the rice husks are mixed in a weight ratio of 79:46:1:77:15 in sequence to obtain a third mixture, and the third mixture undergoes a high-temperature hydrothermal reaction at 170 C. for 24 hours to produce a sample. The sample is then washed with deionized water and ethanol, subjected to centrifugation, dried at 80 C., and calcined in a muffle furnace at 550 C. for 6 hours after being heated at a rate of 5 C. per minute. The remainder of this embodiment aligns with Comparative Example 1.

Embodiment 2

(7) In the step (2), the weight content of the binder is modified to 18.75%, and the amount of the peptizer is modified to 2.25% of the total weight of the third mixture of the ZSM-5 powder containing the rice husks, the binder, and the extrusion aid. The remainder of this embodiment aligns with Embodiment 1.

Embodiment 3

(8) In the step (2), the weight content of the binder is modified to 16.67%, and the amount of the peptizer is modified to 2% of the total weight of the third mixture of the ZSM-5 powder containing the rice husks, the binder, and the extrusion aid. The remainder of this embodiment aligns with Embodiment 1.

Embodiment 4

(9) In the step (2), the weight content of the binder is modified to 12.5%, and the amount of the peptizer is modified to 1.5% of the total weight of the third mixture of the ZSM-5 powder containing the rice husks, the binder, and the extrusion aid. The remainder of this embodiment aligns with Embodiment 1.

Embodiment 5

(10) In the step (2), the weight content of the binder is modified to 8.33%, and the amount of the peptizer is modified to 1% of the total weight of the third mixture of the ZSM-5 powder containing the rice husks, the binder, and the extrusion aid. The remainder of this embodiment aligns with Embodiment 1.

(11) The technical effects of the products obtained in Comparative Embodiment 1 and Embodiments 1-5 are compared and shown in Table 1 described below.

(12) TABLE-US-00001 TABLE 1 The technical effects of the products obtained in Comparative Embodiment 1 and Embodiments 1-5 Specific Pore Average surface area Aperture volume compressive (m.sup.2/g) (nm) (cm.sup.3/g) strength (N) Comparative 605 1.5 0.39 14.6 Embodiment 1 Embodiment 1 432 0.7 0.47 63.6 Embodiment 2 522 0.7 0.39 48.1 Embodiment 3 606 0.7 0.40 54.3 Embodiment 4 683 0.7 0.53 47.7 Embodiment 5 476 0.7 0.25 32.6

Embodiment 6: Functions of the Rice Husks in the Mechanical Strength of the Catalysts of the Molecular Sieve of the ZSM-5

(13) As shown in FIGS. 2A, 2B, 2C, 2D, 2E, 2F, and 2G, the incorporation of the rice husks facilitates a more uniform adhesion of the molecular sieve of the ZSM-5, acting as an interfacial binder, thereby suggesting that the rice husks can serve as binders in conjunction with silicon to enhance the cohesion of molecular sieve particles of the ZSM-5. Furthermore, silicon can function as a carrier and dispersant for catalysts with some studies reporting an enhancement in the mechanical strength of extrusions through the addition of silicon powder. Consequently, the silicon content within the rice husks exerts a substantial influence on bolstering the mechanical strength of molecular sieve extrusions of the ZSM-5. As shown in Table 2, the addition of the rice husks is conducive to improving mechanical properties.

(14) Scanning electron microscopy (SEM) images of molecular sieve formations of the ZSM-5 incorporating the rice husks are as follows. FIGS. 2A and 2D illustrate SEM images of the nanoscale molecular sieve formation absent from the rice husks, FIGS. 2B and 2E illustrate SEM images of a nanoscale molecular sieve formation with the inclusion of the rice husks, and FIGS. 2C and 2F illustrate SEM images of a of a micro-scale molecular sieve formation with the inclusion of the rice husks.

(15) TABLE-US-00002 TABLE 2 Mechanical properties of different molecular sieves of the ZSM-5 Fracture load with a specific Standard probability of Mean deviation Weibull parameters failure (N) Sample (N) (N) (m) F.sub.0(N) R.sup.2 F.sub.1% F.sub.5% F.sub.10% nanoscale ZSM-5 14.56 2.27 7.586 20.8 0.953 8.5 10.5 11.5 (no rice husks) nanoscale ZSM-5 63.47 16.09 4.6786 69.1 0.952 25.9 36.6 42.7 with the rice husks microscale ZSM-5 84 12.61 7.92 35.6 0.946 49.9 61.3 67.2 with the rice husks

Embodiment 7: Functions of the Rice Husks in a Formation Composition and Mechanical Strength of a Catalyst

(16) As shown in Table 3, the incorporation of the rice husks into the synthesized catalyst samples indicates a trend where mechanical strength of extrusions of the catalyst decreases with the reduction of the binder and the peptizer. However, even when of the binder proportion is reduced to of the initial composition, the molecular sieve of the ZSM-5 containing the rice husks exhibits a mechanical strength of 32.6 N, which is more than twice the 14.56 N observed for the extrusion of the catalyst lacking the rice husks. Consequently, the inclusion of the rice husks can significantly reduce the quantities of the binder and the peptizer required for the extrusion of the catalyst, leading to a substantial decrease in the formulation cost of the catalyst.

(17) TABLE-US-00003 TABLE 3 Mechanical properties of different molecular sieves of the ZSM-5 Fracture load with Amount of the Standard specific probability binder and the Mean deviation Weibull parameters of failure (N) peptizer (N) (N) (m) F.sub.0(N) R.sup.2 F.sub.1% F.sub.5% F.sub.10% Comparison 14.56 2.27 7.6 20.8 0.953 8.5 10.5 11.5 (samples without rice husks) 32.6 7.96 4.8 35.6 0.96 13.63 19.1 22.2 47.68 8.46 6.65 51.1 0.92 25.6 32.7 36.5 54.34 9.41 6.87 58.2 0.92 29.8 37.8 41.9 48.1 8.73 6.35 51.8 0.95 25.1 32.4 36.3 1 63.47 16.09 4.7 69.1 0.952 25.9 36.6 42.7

(18) FIG. 3 is a comparative analysis of the selectivity between pure nanoscale molecular sieve and nanoscale molecular sieve containing the rice husks as a template, both utilized as thermal cracking catalysts for stearic acid.

(19) The findings reveal that the molecular sieve prepared with the rice husks as a template exhibits an improved olefin selectivity in the thermal cracking products. The adjustment is attributed to an adjustment of pores after the formation of the two molecular sieves.

(20) The preceding description is merely preferred embodiments of the present disclosure, but the scope of the present disclosure is not limited to these embodiments. Thus, the present disclosure is intended to encompass all equivalent variations and modifications provided they are made without departing from the claims and the specification provided in the present disclosure.