Method for preparing a catalyst for pyrolysis of waste plastics to produce oil and use thereof

Abstract

The present disclosure provides a method for preparing a catalyst for pyrolysis of waste plastics to produce oil, comprising: washing and modifying coal gangue powder with acid, and then placing in an alkaline solution, etching under magnetic stirring for 20-30 minutes, and washing with water until neutral; placing the catalyst washed until neutral in a metal solution, loading the metal by impregnation, and then filtering and washing; then placing the catalyst in the molding machine and adding adhesive and water, to compress into a suitable shape, drying, and finally calcinating to activate to obtain a product. The present disclosure not only solves the problem of waste plastic pollution, but also obtains fuel oil with high valuable products while reducing the cost of waste plastic treatment, and also improves the yield of fuel oil.

Claims

1. A method for preparing a catalyst for pyrolysis of waste plastics to produce oil, wherein comprising: Step 1: washing and modifying coal gangue powder with acid to obtain acid-modified coal gangue powder; Step 2: placing the acid-modified coal gangue powder of Step 1 in an alkaline solution, and etching under magnetic stirring for 20-30 minutes, then washing with water until neutral; Step 3: placing the washed coal gangue powder of step 2 in a solution containing metal ions, and loading the metal ions onto the washed coal gangue powder by impregnation, and then filtering and washing to obtain a catalyst loaded with metal; Step 4: placing the catalyst loaded with metal of Step 3 into a molding machine, and adding with adhesive and water, to compress into a shape; Step 5: drying the compressed catalyst of Step 4, then calcinating in a muffle furnace, and activating to obtain a product; wherein in Step 2, the alkaline solution is a weak base with a concentration of 0.5 mol.Math.L.sup.1; a volume ratio of the coal gangue powder to the weak base is 1:1.0-1.5; and the weak base is a solution of n-butylamine.

2. The method for preparing the catalyst for pyrolysis of waste plastics to produce oil according to claim 1, wherein in step 1, grinding the coal gangue into the coal gangue powder, sieving the coal gangue powder into 30 to 50 meshes, and washing and modifying with acid is to evenly mix the coal gangue powder with an acid solution, and then washing with the acid under ultrasonic at 25 to 50 C. for 10 to 20 minutes, then removing surface impurities by washing with water, and washing until neutral.

3. The method for preparing the catalyst for pyrolysis of waste plastics to produce oil according to claim 2, wherein the acid solution is hydrochloric acid, nitric acid, or a mixture of the two.

4. The method for preparing the catalyst for pyrolysis of waste plastics to produce oil according to claim 1, wherein in step 3, the solution containing metal ions is nickel nitrate, zinc nitrate, manganese nitrate, cobalt nitrate or ammonium molybdate, with a metal loading of 5%.

5. The method for preparing the catalyst for pyrolysis of waste plastics to produce oil according to claim 1, wherein in step 4, the shape is strip, ingot, single column, annular or spherical.

6. The method for preparing the catalyst for pyrolysis of waste plastics to produce oil according to claim 1, wherein in step 5, drying the compressed catalyst in a vacuum dryer at 100-120 C. for 8-10 hours; calcinating in the muffle furnace at 500-600 C. for 4-5 hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of the raw material of a catalyst for pyrolysis of the waste plastics of the present disclosure, i.e. the coal gangue before and after crushed;

(2) FIG. 2 is a schematic diagram of the coal gangue etched by different base during the method for preparing a catalyst for pyrolysis of the waste plastics of the present disclosure, wherein: (a) NaOH, (b) NH.sub.3.Math.H.sub.2O, (c) n-butylamine, (d) pyrrole, (e) not etched;

(3) FIG. 3 shows the yield of the fuel oil and the light oil from the catalytic pyrolysis of the waste plastics using a catalyst prepared by the NaOH etched coal gangue;

(4) FIG. 4 shows the yield of the fuel oil and the light oil from the catalytic pyrolysis of the waste plastics using a catalyst prepared by the NH.sub.3.Math.H.sub.2O etched coal gangue;

(5) FIG. 5 shows the yield of the fuel oil and the light oil from the catalytic pyrolysis of the waste plastics using a catalyst prepared by the n-butylamine etched coal gangue;

(6) FIG. 6 shows the yield of the fuel oil and the light oil from the catalytic pyrolysis of the waste plastics using a catalyst prepared by the pyrrole solution etched coal gangue;

(7) FIG. 7 shows the yield of fuel oil and light oil from the catalytic pyrolysis of waste plastics using a catalyst that have not been etched;

(8) FIG. 8 shows the structural diagram of a two-stage fixed bed reactor for catalytic pyrolysis of the waste plastics in the application of the catalyst of the present disclosure; wherein: 1. Air inlet, 2. Quartz tube reactor, 3. Pyrolysis sleeve, 4. Support pipe, 5. Catalytic sleeve, 6. Ice salt bath, 7. Air bag, 8. Temperature controller, 9. Insulation layer.

DETAILED DESCRIPTION

(9) The present invention is described below in further detail with reference to the accompanying drawings and specific implementations.

(10) The raw materials of the present disclosure can be purchased in commercial.

(11) The adhesive in the present disclosure refers to the high-temperature resistant adhesive HR-8767.

(12) The waste plastics in the present disclosure includes kitchen waste, textiles, rubber or thermoplastic elastomer debris, or a mixture of two or more.

(13) As shown in FIG. 1, the coal gangue is used as the raw material, which is first crushed and then ground into powder for use. A comparison of the coal gangue etched by different base and unearthed during the preparation of a catalyst for pyrolysis of the waste plastics of the present disclosure is shown in FIG. 2.

(14) A method for preparing a catalyst for pyrolysis of waste plastics to produce oil, comprising: Step 1: washing and modifying coal gangue powder with acid to obtain acid-modified coal gangue powder; the specific steps are as follows: grinding the coal gangue into the coal gangue powder, sieving the coal gangue powder into 30-50 mesh, washing and modifying with acid is to evenly mix the coal gangue powder with an acid solution, and washing with acid under ultrasound at 25-50 C. for 10-20 minutes, and then removing surface impurities by washing with water, and washing until neutral; the acid solution is hydrochloric acid, nitric acid, or a mixture thereof. When the acid solution is a mixture of hydrochloric acid and nitric acid, the volume ratio of hydrochloric acid to nitric acid is 1:1 to 2; Step 2: placing the coal gangue powder in an alkaline solution and etching under magnetic stirring for 20-30 minutes, then washing with water until neutral; the alkaline solution is NH.sub.3.Math.H.sub.2O, n-butylamine or pyrrole solution, and the concentration of the alkaline solution is 0.5 mol.Math.L.sup.1; a volume ratio of the coal gangue powder to the alkaline solution is 1:1.0-1.5; Step 3: placing the catalyst of step 2 in a solution containing metal ions, and loading the metal ions onto the catalyst by impregnation, and then filtering and washing to obtain the catalyst loaded with metal; the solution containing metal ions is nickel nitrate, zinc nitrate, manganese nitrate, cobalt nitrate or ammonium molybdate, with a metal loading of 5%; Step 4: placing the catalyst loaded with metal of Step 3 into a molding machine, and adding with adhesive and water, to compress into a suitable shape; if the molding machine is an extrusion machine, a strip shape can be obtained. Step 5: drying the compressed catalyst of Step 4 in a vacuum dryer at 100-120 C. for 8-10 hours; calcinating the dried catalyst in a muffle furnace at 500-600 C. for 4-5 hours, to obtain a product.

(15) A catalyst for pyrolysis of the waste plastics prepared by the preparation method is placed in a two-stage fixed bed reactor for catalytic pyrolysis of the waste plastics as shown in FIG. 8, the bed reactor including an inlet 1, a quartz tube reactor 2, a pyrolysis sleeve 3, a support tube 4, a catalytic sleeve 5, an ice salt bath 6, an air bag 7, a temperature controller 8, and an insulation layer 9. The air inlet 1 is located at the top of the quartz tube reactor 2, and a pyrolysis sleeve 3 is provided in the middle of the quartz tube reactor 2. A support tube 4 is connected below the pyrolysis sleeve 3, and a catalytic sleeve 5 is connected below the support tube 4. The catalyst prepared by the preparation method of the present disclosure is located inside the catalytic sleeve 5. The periphery of the quartz tube reactor 2 is provided with an insulation layer 9, and two groups of the temperature controller 8 is provided, one group connected to the pyrolysis sleeve and the other group connected to the catalytic sleeve. The pyrolysis atmosphere is N.sub.2, which is introduced into the quartz tube reactor from the top inlet. The pyrolysis sleeve is used to place the waste plastics shavings as the raw material, and the support pipe is used to provide a diffusion space for the volatile matter and prevent mixing of the waste plastics with the catalyst. The catalytic sleeve is used to place the catalyst. The quartz cotton can be added to the catalytic sleeve to fix the catalyst, in order to recycle the catalyst conveniently. The liquid phase of the product is cooled by the ice salt bath, and the non-condensable gases are collected by the air bag. The pyrolysis temperature and catalytic temperature are controlled by the temperature controller respectively, and an insulation layer is provided outside the reactor.

Embodiment 1

(16) A catalyst for pyrolysis of the waste plastics using the coal gangue as the raw material, comprising: (1) grinding 10 g of the coal gangue into powder, selecting 40 mesh coal gangue powder, and placing into an acid mixture. The acid mixture includes 16% hydrochloric acid and 30% nitric acid by mass, with a volume ratio of 1:1. After mixing the coal gangue powder and the acid mixture evenly, placing on a shaking oscillator at 30 C. for 15 minutes, and then washing with pure water until neutral to obtain acid-modified coal gangue powder; (2) placing the acid-modified coal gangue powder of step (1) into a NaOH solution, and etching under magnetic stirring for 25 minutes, then washing with water until neutral; (3) washing the catalyst of step (2) with water until neutral and mixing with different solutions containing metal ions. The solutions containing metal ions are nickel nitrate, zinc nitrate, manganese nitrate, cobalt nitrate, or ammonium molybdate solution; loading the catalyst with a loading capacity of 5% for each metal using an equal-volume impregnation method; after filtration, washing with deionized water until neutral to obtain a catalyst with a loading capacity of 5%. (4) placing the metal loaded catalysts of step (3) into the molding machine, and adding 4 g of high-temperature resistant adhesive HR-8767 and an appropriate amount of water; after molding, drying in a vacuum dryer at 110 C. for 10 hours until the liquid disappears; then calcinating the catalyst in a muffle furnace at 550 C. for 4 hours to activate and ultimately produce five different metal modified catalysts.

(17) Performing the experiments pyrolysis of the waste plastics using the five catalysts prepared in this embodiment:

(18) Four catalytic pyrolysis experiments are performed on the kitchen waste, textiles, rubber, and thermoplastic elastomer debris from a garbage treatment plant using the catalyst prepared in Embodiment 1. 10 g of waste plastic and 5 g of metal modified coal gangue catalyst are placed in the pyrolysis section and catalytic section sleeves of a two-stage fixed bed reactor for the catalytic pyrolysis experiments. The pyrolysis section and catalytic section temperatures are 550 C. and 500 C., respectively. The pyrolysis is performed for 30 minutes, and the bottom liquid phase product pyrolysis oil is collected. Light oil and heavy oil are extracted and separated, and weighed separately. The production of the pyrolysis product fuel oil and light oil are shown in Table 1, and the yield of the pyrolysis fuel oil and light oil are shown in FIG. 3.

(19) TABLE-US-00001 TABLE 1 Production of light oil and heavy oil from pyrolysis of the waste plastics using catalyst prepared by NaOH solution etching Ni modified Zn modified Mn modified Co modified Mo modified light heavy light heavy light heavy light heavy light heavy oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g kitchen waste 1.929 3.256 1.802 3.285 1.884 3.177 1.809 3.232 1.891 3.219 textiles 1.903 3.297 1.749 3.369 1.828 3.276 1.868 3.242 1.821 3.214 rubber 1.868 3.305 1.795 3.307 1.906 3.202 1.843 3.277 1.786 3.273 thermoplastic 1.891 3.287 1.821 3.294 1.944 3.123 1.857 3.206 1.802 3.258 elastomer debris

(20) Research has shown that the catalyst obtained by NaOH etching has low fuel oil yield and quality in catalytic pyrolysis of the waste plastics, even lower than the catalyst without etching treatment, because of its strong alkalinity, which damages the main structure of silicon and aluminum, and reacts with exposed metal elements. The reaction products adhere to the surface of the catalyst, covering the active sites, resulting in the catalyst lose most of its catalytic effect.

Embodiment 2

(21) The same process is performed, except that: in step (2), placing the acid-modified coal gangue powder of step (1) in a NH.sub.3.Math.H.sub.2O solution, etching under magnetic stirring for 25 minutes, and then washing with water until neutral.

(22) Performing the pyrolysis experiments of the waste plastics on the catalyst prepared in this embodiment:

(23) The kitchen waste, textiles, rubber, and thermoplastic elastomer debris from a waste treatment plant are used. The steps of the pyrolysis experiment are the same as Embodiment 1. The production of the fuel oil and the light oil of the pyrolysis product are shown in Table 2, and the yield of the fuel oil and the light oil of the pyrolysis product are shown in FIG. 4.

(24) TABLE-US-00002 TABLE 2 Production of light oil and heavy oil from pyrolysis of the waste plastics using catalyst prepared by NH.sub.3H.sub.2O etching Ni modified Zn modified Mn modified Co modified Mo modified light heavy light heavy light heavy light heavy light heavy oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g kitchen waste 2.512 3.787 2.436 3.706 2.479 3.747 2.534 3.782 2.464 3.722 textiles 2.473 3.754 2.492 3.710 2.488 3.684 2.502 3.754 2.421 3.698 rubber 2.499 3.761 2.449 3.701 2.396 3.749 2.435 3.785 2.497 3.724 thermoplastic 2.450 3.796 2.427 3.694 2.468 3.731 2.498 3.767 2.433 3.712 elastomer debris

(25) Research has shown that the catalyst obtained from NH.sub.3.Math.H.sub.2O etching catalyzes the pyrolysis of the waste plastics, resulting in lower fuel oil yield and quality. Due to its stronger alkalinity than organic weak bases, the pore size formed by etching is larger, and there are fewer reactive sites, resulting in poorer catalytic performance.

Embodiment 3

(26) The same process is performed, except that: in step (2), placing the acid-modified coal gangue powder of step (1) in a n-butylamine solution, etching under magnetic stirring for 25 minutes, and then washing with water until neutral.

(27) Performing the pyrolysis experiments of the waste plastics on the catalyst prepared in this embodiment:

(28) The kitchen waste, textiles, rubber, and thermoplastic elastomer debris from a waste treatment plant are used. The steps of the pyrolysis experiment are the same as Embodiment 1. The production of the fuel oil and the light oil of the pyrolysis product are shown in Table 3, and the yield of the fuel oil and the light oil of the pyrolysis product are shown in FIG. 5.

(29) TABLE-US-00003 TABLE 3 Production of light oil and heavy oil from pyrolysis of the waste plastics using catalyst prepared by n-butylamine solution etching Ni modified Zn modified Mn modified Co modified Mo modified light heavy light heavy light heavy light heavy light heavy oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g kitchen waste 3.694 4.117 3.538 4.013 3.708 4.039 3.634 3.968 3.619 4.063 textiles 3.573 4.284 3.488 4.173 3.502 4.204 3.544 4.200 3.568 4.255 rubber 3.285 4.409 3.193 4.386 3.247 4.459 3.191 4.413 3.271 4.394 thermoplastic 3.397 4.353 3.171 4.311 3.317 4.405 3.289 4.376 3.427 4.326 elastomer debris

(30) Research has shown that catalysts obtained by n-butylamine etching have good catalytic effects on the pyrolysis of the waste plastics. The coal gangue catalysts modified with different metals have a catalytic yield of 74-79% for the pyrolysis of the waste plastics to produce fuel oil, which is high. The yield of the light oil can reach over 30%. Although the catalytic effects of the different catalysts on different types of the plastics vary, a precise selection should be made in actual production based on cost and the type of waste plastics required for pyrolysis treatment.

Embodiment 4

(31) The same process is performed, except that: in step (2), placing the acid-modified coal gangue powder of step (1) in a pyrrole solution, etching under magnetic stirring for 25 minutes, and then washing with water until neutral.

(32) Performing the pyrolysis experiments of the waste plastics on the catalyst prepared in this embodiment:

(33) The kitchen waste, textiles, rubber, and thermoplastic elastomer debris from a waste treatment plant are used. The steps of the pyrolysis experiment are the same as Embodiment 1. The production of the fuel oil and the light oil of the pyrolysis product are shown in Table 4, and the yield of the fuel oil and the light oil of the pyrolysis product are shown in FIG. 6.

(34) TABLE-US-00004 TABLE 4 Production of light oil and heavy oil from pyrolysis of the waste plastics using catalyst prepared by pyrrole solution etching Ni modified Zn modified Mn modified Co modified Mo modified light heavy light heavy light heavy light heavy light heavy oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g kitchen waste 2.316 3.468 2.291 3.395 2.287 3.416 2.301 3.417 2.324 3.426 textiles 2.281 3.493 2.253 3.467 2.236 3.461 2.272 3.469 2.297 3.481 rubber 2.226 3.421 2.282 3.412 2.227 3.392 2.231 3.424 2.275 3.431 thermoplastic 2.199 3.489 2.186 3.461 2.184 3.455 2.194 3.481 2.216 3.488 elastomer debris

(35) Research has shown that the catalyst obtained by pyrrole solution etching catalyzes the pyrolysis of the waste plastics, resulting in poor yield and quality of pyrolysis oil. This is mainly due to weak alkalinity, poor etching effect, failure to obtain a uniform pore size with high accessibility, fewer reaction active sites, and poor catalytic effect.

Comparative Embodiment 1

(36) The preparation steps of a catalyst for pyrolysis of the waste plastics using the coal gangue as the raw material, comprising: (1) grinding 10 g of coal gangue into powder, sieving the coal gangue powder into 40 mesh, placing into a 1:1 mixture solution of 16% hydrochloric acid and 30% nitric acid by volume for uniform mixing, placing on a shaking oscillator at 30 C. for 15 minutes, and washing with pure water until neutral to obtain acid-modified coal gangue powder. (2) mixing the acid-modified coal gangue powder of step (1) evenly with nickel nitrate solution, zinc nitrate, manganese nitrate, cobalt nitrate, and ammonium molybdate; loading catalysts with 5% loading of each metal using the equal-volume impregnation method; after filtration, washing with deionized water until neutral to obtain a catalyst with a loading of 5%. (3) placing the metal modified catalysts of step (2) into the molding machine, and adding 4 g of high-temperature resistant adhesive HR-8767 and an appropriate amount of water; after molding, drying in a vacuum dryer at 110 C. for 10 hours until the liquid disappears; then calcinating the catalyst in a muffle furnace at 550 C. for 4 hours to activate and ultimately produce catalysts modified by different metals.

(37) Performing the pyrolysis experiments of the waste plastics on the catalysts prepared in this comparative embodiment:

(38) Four catalytic pyrolysis experiments are performed on the kitchen waste, textiles, rubber, and thermoplastic elastomer debris from a certain garbage treatment plant using the prepared metal modified catalyst. 10 g of waste plastic and 5 g of metal modified coal gangue catalyst are used respectively, and placed in the pyrolysis section and catalytic section sleeves of a two-stage fixed bed reactor for catalytic pyrolysis experiments. The pyrolysis section and catalytic section temperatures are 550 C. and 500 C., respectively. The pyrolysis is performed for 30 minutes. The bottom liquid phase product pyrolysis oil is collected, and the light oil and heavy oil are extracted and separated, and weighed separately. The production of the pyrolysis product fuel oil and light oil are shown in Table 5, and the yield of the pyrolysis fuel oil and light oil are shown in FIG. 7.

(39) TABLE-US-00005 TABLE 5 Production of light oil and heavy oil from pyrolysis of the waste plastics using unetched catalysts Ni modified Zn modified Mn modified Co modified Mo modified light heavy light heavy light heavy light heavy light heavy oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g oil/g kitchen waste 2.224 3.385 2.177 3.289 2.129 3.341 2.195 3.311 2.104 3.271 textiles 2.206 3.361 2.146 3.295 2.186 3.249 2.176 3.302 2.185 3.246 rubber 2.178 3.349 2.133 3.307 2.193 3.251 2.143 3.286 2.201 3.224 thermoplastic 2.196 3.354 2.141 3.312 2.106 3.288 2.156 3.217 2.109 3.257 elastomer debris

(40) In summary, the preparation of a catalyst for pyrolysis of the waste plastics of the present disclosure is easily operable, the raw materials are easily obtained. Impurities are easily removed by acid modification of the coal gangue, and further alkaline etching is performed to obtain a relatively uniform and highly accessible pore structure. Finally, the catalyst is prepared by loading metal. Experimental research has shown that in the alkaline etching step, the catalyst obtained by n-butylamine etching in weak base has the best effect. Due to its uniform pore structure, the metal loading is also uniform, and contains a large amount of metal elements. When combined with the loaded metal in the catalytic process, a synergistic effect is created, which can achieve efficient and high-quality catalytic effects.

(41) The parts not mentioned in the present disclosure can be implemented by referring to existing technologies.

(42) Certainly, the above descriptions are merely preferred embodiments of the present disclosure. The present disclosure is not limited to the above embodiments listed. It should be noted that, all equivalent replacements and obvious variations made by any person skilled in the art under the teaching of the specification fall within the essential scope of the specification and shall be protected by the present disclosure.