Method for assisting methanol alcoholysis of waste PET (polyethylene terephthalate) by using ester solvent

Abstract

The invention belongs to the technical field of PET (Polyethylene Terephthalate) recovery, and particularly relates to a method for assisting methanol alcoholysis of waste PET by using an ester solvent. The method comprises the following steps: by taking waste PET as a raw material, methanol as a solvent and an ester solvent as a cosolvent, catalyzing and depolymerizing the waste PET under the action of an organic strong alkali catalyst to obtain an alcoholysis product, and further separating and purifying the alcoholysis product to obtain DMT and high-value byproducts. The method is mild in reaction condition and rapid in reaction process, the catalyst does not contain metal, and the subsequent purification process can be simplified.

Description

Technical Field

[0001] The invention relates to the technical field of PET recovery, in particular to a method for methanolysis of waste PET assisted by ester solvents. Background Art

[0002] Polyethylene terephthalate (PET) is the main type of thermoplastic polyester, widely used in bottles and fibers, with an annual global production of about 30 million tons. From the perspective of sustainable development, we urgently need an efficient recycling method. However, due to its stable chemical properties, PET is difficult to degrade in the natural environment. Direct landfill or incineration will cause white pollution and release harmful gases. Therefore, the resource recycling of waste PET has become increasingly important.

[0003] At present, there are two methods for recycling PET: physical and chemical. In terms of circular economy, chemical recycling has the greatest potential, but the traditional chemical recycling method has the problem of high energy consumption, such as high temperature (~300℃), high pressure (~15Mpa), and long reaction time. Therefore, the development of low-energy PET degradation methods has attracted more and more attention.

[0004] PET and methanol can undergo ester exchange to generate dimethyl terephthalate (DMT) and ethylene glycol (EG). The ester exchange reaction is theoretically reversible, so the key to achieving efficient catalysis is to make the PET methanolysis reaction shift in the direction of generating reactants. US9550713B1 discloses a method of promoting PET depolymerization by combining an inorganic base with a conventional organic solvent, but a high catalyst load (20 mol%) and a long reaction time (24 h) are required to obtain a high yield of DMT. Other scholars also use acetonitrile to enhance the methanolysis of PET polyester. PET can be completely depolymerized at 120 ° C and 2 h, but the pressure is relatively high (> 4 MPa), and the catalyst contains metal elements, which are prone to residues that affect the quality of the product. Therefore, finding a suitable solvent to achieve efficient depolymerization of PET under mild conditions has broad application prospects and important practical significance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for methanolysis of waste PET assisted by an ester solvent, so as to solve the problems existing in the above-mentioned prior art and realize efficient depolymerization of PET under mild conditions.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a method for methanolysis of waste PET assisted by an ester solvent, the steps comprising:

[0008] With waste PET as raw material, methanol as solvent and ester solvent as co-solvent, waste PET is catalytically depolymerized under the action of organic strong base catalyst to obtain alcoholysis product.

[0009] Furthermore, the amount of methanol used is 100% to 500% of the mass of the waste PET.

[0010] Furthermore, the ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl malonate, methyl propionate and methyl butyrate.

[0011] Furthermore, the usage of the ester solvent is 50% to 1000% of the mass of the waste PET.

[0012] Further, the organic strong base includes at least one of 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,1,3,3-tetramethylguanidine (TMG), triethanolamine (TEA), N-methylmorpholine (NMM), N,N-diisopropylethylamine (DIPEA) and (tert-butylimino)tri(pyrrolidino)phosphine (BTPP).

[0013] Furthermore, the dosage of the organic strong base is 1% to 10% of the mass of the waste PET.

[0014] Furthermore, the temperature of the catalytic depolymerization of waste PET is 80 to 150° C. and the time is 15 to 60 minutes.

[0015] Furthermore, it also includes separation and purification of the alcoholysis product.

[0016] Preferably, the separation and purification step comprises:

[0017] S1, distilling the alcoholysis product under reduced pressure to remove the ester solvent and methanol, then washing with a methanol aqueous solution, and filtering to obtain a filtrate and DMT;

[0018] S2, rotary evaporating the filtrate, cooling and crystallizing to obtain a by-product.

[0019] When the ester solvent is dimethyl carbonate, the by-product is ethylene carbonate;

[0020] When the ester solvent is diethyl carbonate, the by-product is ethylene carbonate;

[0021] When the ester solvent is ethyl methyl carbonate, the byproducts are ethylene carbonate and ethylene glycol carbonate;

[0022] When the ester solvent is dimethyl malonate, the by-product is ethylene glycol malonate;

[0023] When the ester solvent is methyl propionate, the by-product is ethylene glycol propionate;

[0024] When the ester solvent is methyl butyrate, the by-product is ethylene glycol butyrate.

[0025] More preferably, the volume ratio of methanol to water in the methanol aqueous solution is 1:3 to 3:1.

[0026] More preferably, the temperature of the reduced pressure distillation is 40-200°C.

[0027] More preferably, the temperature of the rotary evaporation is 60-150°C.

[0028] In the preparation method of the present invention, methanol depolymerizes PET to generate DMT and EG, and the reaction is reversible. The ester solvent undergoes an ester exchange reaction with the product EG to generate other ester products, thereby promoting the alcoholysis reaction of PET to move to a positive equilibrium, so that it can be quickly depolymerized at a lower temperature and pressure. When the ester solvent is dimethyl carbonate, it can be seen from the following reaction formula that dimethyl carbonate is used as a solvent, and can further react with the product EG to generate methanol and ethylene carbonate. Ethylene carbonate is a cyclic structure that is more stable and promotes the reaction to move to a positive equilibrium.

[0029]

[0030] Technical solution 2 of the present invention: A method for preparing DMT by promoting the forward reaction of PET by methanolysis, comprising the following steps:

[0031] Using PET as raw material, methanol as solvent and ester solvent as co-solvent, PET is catalytically depolymerized under the action of organic strong base catalyst to obtain alcoholysis product;

[0032] The alcoholysis product is distilled under reduced pressure to remove the ester solvent and methanol, then washed with a methanol aqueous solution and filtered to obtain DMT.

[0033] The third technical solution of the present invention is a method for recycling waste PET, comprising the following steps:

[0034] Using waste PET as raw material, methanol as solvent, and ester solvent as co-solvent, the waste PET is catalytically depolymerized under the action of an organic strong base catalyst to obtain an alcoholysis product;

[0035] The alcoholysis product is subjected to reduced pressure distillation to recover the ester solvent and methanol, then washed with a methanol aqueous solution, and filtered to obtain a filtrate and DMT;

[0036] The filtrate is subjected to rotary evaporation and cooling crystallization to recover methanol and organic strong base catalyst to obtain a by-product.

[0037] The present invention discloses the following technical effects:

[0038] The product obtained by the preparation method of the present invention is easy to separate and purify from impurities, ester solvents have good solubility for DMT, while impurities are insoluble in ester solvents, and after the depolymerization reaction is completed, the product and impurities can be better separated, and the method is applicable to different raw materials and can realize the recovery of different impurity-containing polyester materials.

[0039] The present invention adopts different ester solvents to assist the methanolysis of waste PET to obtain high-value by-products. For example, by using dimethyl carbonate to assist the methanolysis, the by-product ethylene carbonate can be obtained, which can be used as a liquid electrolyte for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0041] Figure 1 This is the gas chromatogram of the product of PET methanolysis catalyzed by dimethyl carbonate;

[0042] Figure 2 It is a schematic diagram of the process flow of a specific implementation scheme of the present invention. DETAILED DESCRIPTION

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0045] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0046] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0047] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0048] The waste PET used in the specific embodiment of the present invention includes PET bottles, PET films or PET fibers.

[0049] Unless otherwise specified, the “parts” referred to in the specific embodiments of the present invention are all “parts by mass”.

[0050] Example 1

[0051] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0052] S1, adding 10 parts of PET bottle flakes after washing and drying, 0.5 parts of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of dimethyl carbonate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0053] S2, washing the alcoholysis product with 50 parts of dimethyl carbonate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 40° C. to remove excess dimethyl carbonate and methanol, and washing the obtained solid product with a cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0054] S3, the filtrate obtained in step 2 is subjected to rotary evaporation at 60° C. to remove excess solvent to obtain ethylene carbonate as a by-product.

[0055] Example 2

[0056] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0057] S1, adding 10 parts of washed and dried PET bottle flakes, 1 part of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of diethyl carbonate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0058] S2, washing the alcoholysis product with 50 parts of diethyl carbonate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 75° C. to remove excess diethyl carbonate and methanol, and washing the obtained solid product with a cold methanol / water (volume ratio 1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0059] S3, the filtrate obtained in step 2 is subjected to rotary evaporation at 80° C. to remove excess solvent and organic strong base catalyst to obtain by-product ethylene carbonate.

[0060] Example 3

[0061] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0062] S1, adding 10 parts of PET bottle flakes after washing and drying, 1 part of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of ethyl methyl carbonate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0063] S2, washing the alcoholysis product with 50 parts of ethyl methyl carbonate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 70° C. to remove excess ethyl methyl carbonate and methanol, and washing the obtained solid product with a cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0064] S3, rotary evaporating the filtrate obtained in step 2 at 100° C. to remove excess solvent and organic strong base catalyst to obtain by-products ethylene carbonate and ethylene glycol carbonate.

[0065] Example 4

[0066] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0067] S1, adding 10 parts of washed and dried PET bottle flakes, 1 part of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of dimethyl malonate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0068] S2, washing the alcoholysis product with 50 parts of dimethyl malonate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 150° C. to remove excess dimethyl malonate and methanol, and washing the obtained solid product with a cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0069] S3, the filtrate obtained in step 2 is subjected to rotary evaporation at 150° C. to remove excess solvent and organic strong base catalyst to obtain a by-product, ethylene glycol malonate.

[0070] Example 5

[0071] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0072] S1, adding 10 parts of PET bottle flakes after washing and drying, 1 part of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of methyl propionate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0073] S2, washing the alcoholysis product with 50 parts of methyl propionate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 60°C to remove excess methyl propionate and methanol, and washing the obtained solid product with cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0074] S3, the filtrate obtained in step 2 is subjected to rotary evaporation at 60° C. to remove excess solvent and organic strong base catalyst to obtain a by-product, ethylene glycol propionate.

[0075] Example 6

[0076] The steps of ester solvent-assisted methanolysis of waste PET are as follows:

[0077] S1, adding 10 parts of PET bottle flakes after washing and drying, 1 part of 1,5-diazabicyclo[4.3.0]non-5-ene, 30 parts of methanol, and 50 parts of methyl butyrate into a reactor, heating to 130°C and reacting for 1 hour, cooling to room temperature after the reaction stops to obtain an alcoholysis product;

[0078] S2, washing the alcoholysis product with 50 parts of methyl butyrate and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 70°C to remove excess methyl butyrate and methanol, and washing the obtained solid product with cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0079] S3, the filtrate obtained in step 2 is subjected to rotary evaporation at 70° C. to remove excess solvent and organic strong base catalyst to obtain a by-product, ethylene glycol butyrate.

[0080] Example 7

[0081] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0082] Example 8

[0083] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0084] Example 9

[0085] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of 1,1,3,3-tetramethylguanidine.

[0086] Example 10

[0087] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of triethanolamine.

[0088] Embodiment 11

[0089] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of N-methylmorpholine.

[0090] Example 12

[0091] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of N,N-diisopropylethylamine.

[0092] Example 13

[0093] Compared with Example 1, the only difference is that 1,5-diazabicyclo[4.3.0]non-5-ene is replaced by an equal amount of (tert-butylimino)tri(pyrrolidine)phosphine.

[0094] Embodiment 14

[0095] Compared with Example 1, the only difference is that the PET bottle flakes are replaced by an equal amount of PET film.

[0096] Embodiment 15

[0097] Compared with Example 1, the only difference is that the PET bottle flakes are replaced by an equal amount of PET fiber cloth.

[0098] Example 16

[0099] Compared with Example 1, the only difference is that the PET bottle flakes are replaced by an equal amount of PET aluminum-containing ground film.

[0100] Embodiment 17

[0101] Compared with Example 1, the only difference is that the PET bottle flakes are replaced with an equal amount of polyester-cotton blended fabric.

[0102] Embodiment 18

[0103] Compared with Example 1, the only difference is that the PET bottle flakes are replaced by an equal amount of PET fishing nets.

[0104] Embodiment 19

[0105] Compared with Example 1, the only difference is that the amount of 1,5-diazabicyclo[4.3.0]non-5-ene is changed to 1 part.

[0106] Embodiment 20

[0107] Compared with Example 1, the only difference is that the amount of 1,5-diazabicyclo[4.3.0]non-5-ene is changed to 0.1 parts.

[0108] Comparative Example 1

[0109] Compared with Example 1, dimethyl carbonate was not added, and the specific steps were as follows:

[0110] S1, take 10 parts of PET bottle flakes after washing and drying, 0.5 parts of 1,5-diazabicyclo[4.3.0]non-5-ene, and 30 parts of methanol, add them into a reactor, heat to 130°C and react for 1 hour, and cool to room temperature after the reaction stops to obtain an alcoholysis product;

[0111] S2, washing the alcoholysis product with 50 parts of hot methanol and filtering, removing the filter residue (unreacted PET) and then distilling under reduced pressure at 40°C to remove excess methanol, and washing the obtained solid product with cold methanol / water (1:1) solution and filtering and drying to obtain a filtrate and DMT;

[0112] S3. The filtrate obtained in step 2 is subjected to rotary evaporation at 130° C. to recover the catalyst, and the remaining liquid is ethylene glycol.

[0113] Comparative Example 2

[0114] Compared with Example 1, the only difference is that no catalyst is added.

[0115] Comparative Example 3

[0116] Compared with Example 1, the only difference is that the amount of catalyst is changed to 2 parts.

[0117] Test example

[0118] The PET conversion rate, DMT yield and by-product yield of the methods of Examples 1 to 20 and Comparative Examples 1 to 3 were detected and calculated, and the results are shown in Tables 1 to 4.

[0119] PET conversion rate (%) = (total amount of PET - remaining PET after alcoholysis) / total amount of PET;

[0120] DMT yield (%) = actual DMT production / theoretical DMT production;

[0121] By-product yield (%) = actual by-product yield / theoretical by-product yield.

[0122] Table 1 Conversion rate, DMT yield and by-product yield of PET degradation assisted by different ester solvents

[0123]

[0124]

[0125] Table 2 Effect of different catalysts on catalytic methanolysis of PET assisted by dimethyl carbonate

[0126]

[0127] Table 3 Effect of methanolysis of different commercial PET wastes catalyzed by dimethyl carbonate

[0128]

[0129] Table 4 Effect of different catalyst contents on catalytic methanolysis of PET assisted by dimethyl carbonate

[0130]

[0131] It can be seen from the data in Table 1 that compared with not adding ester solvents, adding dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate has better depolymerization effect and higher DMT yield; among several ester solvents, dimethyl carbonate has the best auxiliary effect on methanolysis of PET, and a higher yield of DMT (>97%) and by-products (>88%) can be obtained at 130°C and 1h. In addition, it can be found that organic strong bases have good catalytic effects on PET alcoholysis; in addition, it can be seen from Table 3 that the method is suitable for different commercial PET wastes, and has higher DMT yields and EC yields; comparing Example 1 in Table 1 and Examples 19 and 20 in Table 4 and Comparative Examples 2 and 3, it can be found that the catalyst content has a greater influence on the PET conversion rate and DMT yield. Compared with not adding a catalyst, adding a catalyst has better PET conversion rate and DMT yield, and a low catalyst content will reduce the reaction rate, and a higher content of catalyst promotes the occurrence of side reactions (such as DMT repolymerization to form dimers) to reduce the yield of DMT. This method provides a new idea for the low-temperature methanol depolymerization of PET and has certain industrial prospects.

[0132] Figure 1 This is the gas chromatogram of the products of PET methanolysis catalyzed by dimethyl carbonate.

[0133] Figure 2 It is a schematic diagram of the process flow of a specific implementation scheme of the present invention.

[0134] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for ester solvent-assisted methanolysis of waste PET, characterized in that the steps include: With waste PET as raw material, methanol as solvent and ester solvent as co-solvent, waste PET is catalytically depolymerized under the action of organic strong base catalyst to obtain alcoholysis product.

2. The method according to claim 1, characterized in that The amount of methanol used is 100% to 500% of the mass of the waste PET; the amount of the ester solvent used is 50% to 1000% of the mass of the waste PET; and the amount of the organic strong base used is 1% to 10% of the mass of the waste PET.

3. The method according to claim 1, characterized in that The ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl malonate, methyl propionate and methyl butyrate; the organic strong base includes at least one of DBN, DBU, TBD, TMG, TEA, NMM, DIPEA and BTPP.

4. The method according to claim 1, characterized in that The temperature of the catalytic depolymerization of waste PET is 80-150° C. and the time is 15-60 minutes.

5. The method according to claim 1, characterized in that The method also includes separation and purification of the alcoholysis product.

6. The method according to claim 5, characterized in that The separation and purification step comprises: S1, distilling the alcoholysis product under reduced pressure to remove the ester solvent and methanol, then washing with a methanol aqueous solution, and filtering to obtain a filtrate and DMT; S2, subjecting the filtrate to rotary evaporation, cooling and crystallization to obtain by-products and catalyst.

7. The method according to claim 6, characterized in that When the ester solvent is dimethyl carbonate, the by-product is ethylene carbonate; when the ester solvent is diethyl carbonate, the by-product is ethylene carbonate; when the ester solvent is ethyl methyl carbonate, the by-products are ethylene carbonate and ethylene carbonate; when the ester solvent is dimethyl malonate, the by-product is ethylene malonate; when the ester solvent is methyl propionate, the by-product is ethylene propionate; when the ester solvent is methyl butyrate, the by-product is ethylene butyrate.

8. The method according to claim 6, characterized in that The volume ratio of methanol to water in the methanol aqueous solution is 1:3 to 3:1; the temperature of the reduced pressure distillation is 40 to 200° C.; and the temperature of the rotary evaporation is 60 to 150° C.

9. A method for preparing DMT by promoting the forward reaction of methanolysis of PET, characterized in that the steps include: Using PET as raw material, methanol as solvent and ester solvent as co-solvent, PET is catalytically depolymerized under the action of organic strong base catalyst to obtain alcoholysis product; The alcoholysis product is distilled under reduced pressure to remove the ester solvent and methanol, then washed with a methanol aqueous solution and filtered to obtain DMT.

10. A method for recycling waste PET, characterized in that the steps include: Using waste PET as raw material, methanol as solvent, and ester solvent as co-solvent, the waste PET is catalytically depolymerized under the action of an organic strong base catalyst to obtain an alcoholysis product; The alcoholysis product is distilled under reduced pressure to remove the ester solvent and methanol, then washed with a methanol aqueous solution, and filtered to obtain a filtrate and DMT; The filtrate is subjected to rotary evaporation and cooling and crystallization to obtain by-products and catalyst.

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