Glycolysis optimization of different complex PET waste with recovery and reuse of ethylene glycol

doi:10.21203/rs.3.rs-1649601/v1

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Glycolysis optimization of different complex PET waste with recovery and reuse of ethylene glycol

https://doi.org/10.21203/rs.3.rs-1649601/v1

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The poly (ethylene terephthalate) (PET) is a thermoplastic polyester, non-degradable in the environment that due to the huge amount of waste generated and accumulated in the environment, chemical recycling through glycolysis is considered the most successful method for polymer recycling. In this work, glycolysis of virgin PET and different PET waste (highly colored PET, multilayer PET and municipal sorting waste PET) is carried out using excess ethylene glycol in the presence of zinc acetate as catalyst. Glycolysis temperature, glycolysis time, amount of catalyst and amount of solvent are important factors affecting the glycolysis of PET waste. A Taguchi orthogonal array L₉, 3⁴, is applied to study the main interactions between these factors to optimise the yield. The process results in a good yield (79–88%) to the monomer, bis (2-hydroxyethyl) terephthalate (BHET), with optimum conditions. One of the inconvenient of the glycolysis process is the excessive use of EG so the recovery and reuse of the remaining EG from the process is studied in order to optimise the glycolysis of PET waste making it economical and environmentally friendly. BHET is characterized by FTIR and DSC techniques confirming that is a valid and pure monomer.

PET waste

glycolysis

chemical recycling

BHET

ethylene glycol

Plastic materials, especially poly ethylene terephthalate (PET), provide economic benefits as they are widely spread in daily life, and its global production is increasing rapidly due to the simple synthesis, low-priced production, robustness, and durability that are beneficial for the industry, so they are often a better option than other materials [1]. Subsequently plastics have been massively utilized in different sectors and started to be absolutely necessary for modern society [2]. Despite the unexpected challenging circumstances, in 2020, the European plastics industry rapidly adapted its capacities to continue delivering safe and sustainable solutions to society. In the world, the production of plastics has increased from 1.5 million of tonnes in 1950 to 367 million of tonnes in 2020. So, the world plastic production is increased rapidly and expected to reach over 34 billion metric tons in 2050 [3]. As a consequence of the COVID crisis, in 2020, the European plastics value-chain, experienced a decrease in its production and demand levels. Nevertheless, in Europe, plastic production was 55 million of tonnes, which represents 15% of plastic world production, being the forth in the global plastics materials production [4]. The package industry was the main sector responsible for plastic consumption where more than 29 million tonnes of plastic post-consumer waste were collected, of which 23.4% was still sent to landfill, 42% of plastic wastes were sent to energy recovery operations, and 34.6% was sent to recycling facilities [4].

PET is a thermoplastic polyester, non-degradable in the environment with high resistance to chemical and physical agents, with well characterized properties (e.g. excellent tensile and impact strength, light weight, transparency, low permeability of gases and appropriate thermal stability) [5]. Due to the PET incomparable advantages, it is applied in the production of many materials such as textile fibres, copolymers, resins, carpet yarn, PET bottles and packaging films [6]. In 2020, 4.14 Mt of PET were produced in Europe and the global demand for PET packaging was expected to reach 27.13 million tonnes in 2025 [7]. So, there are a substantial amount of PET waste generated that ends up in the landfills and oceans and needs hundreds of years for degradation has attracted global concern [8]. Because of landfilling is a less favoured alternative, and currently, it is gradually phased out in Europe, it is necessary to do a suitable management of waste plastic. The main goals across Europe are to reduce the amount of plastic waste in circulation by enhancing material reuse, designing for recyclability and recycling with improved quality and economic gains [9].

PET waste can be recycled through four main methods: primary recycling (re-extrusion), secondary recycling (mechanical), tertiary recycling (chemical) and quaternary recycling (energy recovery through incineration) [10–13]. Primary Recycling is the recycling of clean, uncontaminated single-type waste industrial scrap. This method ensures simplicity and low cost. The recycled scrap or waste is either mixed with virgin material to assure product quality or used as a second-grade material [14]. In the mechanical recycling, PET waste is cleaned to remove contaminants and then grinding. The material obtained is remelted and spun to produce rPET fibres or aggregate in concretes mixes [15]. Although the mechanical recycling is still the dominant way to recycle PET waste because is the easiest way to recycle, its main disadvantage is the deterioration of product properties in every cycle due to normally suffers from quality loss caused by thermal and hydrolytic degradation [16–17].

Chemical recycling is the process leading to total depolymerization of polymer to the monomers which can be repolymerized to regenerate the original polymer, or partial depolymerization to oligomers and other chemical substances [18–21]. There are several processes for chemical depolymerization of PET such as glycolysis, methanolysis, ethanolysis, aminolysis and hydrolysis. In methanolysis process, methanol is used as alcoholysis reagent and high temperature (> 200ºC) as well as high pressure (> 2MPa) are needed for the depolymerization of PET. Dimethyl terephthalate and ethylene glycol are generated and as the main components [22–24]. In ethanolysis process, ethanol is used under supercritical conditions completely decomposes to the main product of diethyl terephthalate [25–26]. Aminolysis is also a promising way to degrade PET into monomers with the use of amines, however, this method has been less explored compared with other chemical depolymerization processes and large amounts of undesired products limit the large-scale applications of aminolysis [27]. Hydrolysis of PET was carried out under alkaline (aqueous solutions of sodium hydroxide or potassium hydroxide), acidic (aqueous solutions of sulfuric acid) and neutral conditions to obtained main product of terephthalic acid. In general, sub-and supercritical fluids have proven to be excellent reaction media for the rapid and selective conversion of waste materials into a wide range of useful products, such as basic chemicals, alternative energy and fuels, as well as specialty chemicals [28–32]. The glycolysis reaction is the molecular degradation of PET polymer by transesterification between ester groups and a glycol in excess to obtain the monomer, bis(2-hydroxyethyl) terephthalate (BHET). Glycolysis is one of the most promising way for industrial-level depolymerization of PET due to its mild reaction conditions [33–35]. PET degradation is carried out most frequently using ethylene glycol (EG) as solvent due to its high efficiency [36–39] although other solvents also are used such as diethylene glycol, propylene glycol and dipropylene glycol [40–41]. Studies on the kinetics of PET glycolysis have shown that glycolysis without a catalyst is very slow and complete depolymerization of PET to BHET cannot be achieved. So, glycolysis is most frequently carried out with zinc acetate (ZnAc₂) as catalyst due to it considered the benchmark [35–36, 38]. Other metal salts and ionic liquids have been also investigated [42–45].

Finally, energy recovery refers to the recovery of the plastic’s energy content. Incineration, aiming at the recovery of energy, is currently the most effective way to reduce the volume of organic materials. Although polymers are actually high yielding energy sources due to its original source is petroleum, this method has been widely accused of being ecologically unacceptable owing to the health risk from air born toxic substances such as dioxins (in the case of chlorine containing polymers) and antimony and phthalate esters [46]. In the lack of other PET recycling possibilities, incineration energy recuperation is preferring to landfilling but incineration can never give zero emission, hence the necessity to consider other options.

Due to the chemical recycling of post-consumer PET has been considered the most successful method for polymer recycling according previous literature, it has been the chosen for this work to study the viability and efficiency of the different PET waste.

2.1. Materials

Virgin PET used has been supplied by NOVAPET and samples of different PET waste (highly colored, complex multilayer and municipal solid waste (MSW)) have been provided by ECOEMBES, the Spanish integrated management system for the light packaging waste. The composition of the different types of post-consumed PET used is shown in Table 1.

Table 1

Content of polymers in the different types of PET waste
Type of PET waste	Content
Type of PET waste	% PET	% PE	% PA	% PP
Highly colored PET	90	10	-	-
Complex multilayer PET	82–96	5–10	1–5	-
MSW PET	92	6.2	0.05	1.75

Zinc acetate has been purchased from SCHARLAB, ethylene glycol has been supplied by PANREAC and commercial BHET by SIGMA ALDRICH.

2.2. Methods

2.2.1. Glycolysis processes

Glycolysis experiments are carried out in a 2L stainless steel batch reactor with an electrical resistance to heat and control the temperature and a stirrer to assure the correct mixing of the components. An initial purge of nitrogen is used to prevent possible oxidation of the reaction products. The system can operate at a pressure up to 6 bars. In each experimental run, about 200 g of PET are depolymerized; EG is used as solvent and ZnAc₂ as catalyst which have been reported previously as the most active and suitable solvent and catalyst. The starting time for the reaction is taken when the temperature is the desired one. Temperature and stirring are maintained constant during the whole reaction. Once the reaction is finished, an extraction with hot water is carried out to recover the BHET. So, boiling water is added in excess inside the reactor under vigorous stirring in order to dissolve the BHET monomer. Afterwards, the mixture is quickly filtrated, using 0.45 micras Millipore filter paper, to separate un-reacted PET and solid oligomers above the filter, and a liquid phase composed of BHET and EG-H₂O below the filter. This recovered liquid is refrigerated to achieve the crystallization of the BHET. BHET monomer crystals formed, are filtered again to separate from EG and then dried at 65°C until constant weight. The yield of monomer, is calculated based on the Eq. 1, where W_BHET,t and W_PET,0 refer to the weight of BHET at a certain reaction time and the initial weight of PET, respectively. MW_BHET and MW_PETu are the molecular weights of BHET (254 g·mol^− 1) and PET repeating unit (192 g·mol^− 1), respectively.

\(Yield of BHET \left(\%\right)= \frac{{W}_{BHET,t}/{MW}_{BHET}}{{W}_{PET,0}/{MW}_{PET}}x100\) (Eq. 1)

Besides assessing the feasibility of glycolysis, the economics of the process is considered. As the solvent used in the reaction is higher than the stoichiometric needed, EG recovery from the EG-H₂O solution is carried out. For this, a distillation performed at atmospheric pressure has been carried out to recover the remaining EG using a vacuum rotatory evaporator (Buchi) at 75 ºC and thus reuse it in the following glycolysis runs.

2.2.2. Glycolysis optimization by Taguchi’s methodology

When an experiment has several factors that are relevant, the factorial Design of Experiments (DoE) are the best option to identify interactions between variables. So, the glycolysis of PET has been carried out using the Taguchi’s parameter design methodology [47]. The main goal of this study is to find the best conditions for the process to obtain the higher yield of BHET with optimum purity. These control factors (glycolysis temperature, reaction time, mass ratio solvent to PET and percentage ratio catalysts to PET) and their levels are chosen based on its effectiveness in previous studies [33, 41, 43, 48–52]. These factors and levels used appears in Table 2. The configuration of the orthogonal array L₉ combining the different selected levels of each control factor are showed in Table 3. By using orthogonal arrays, the number of experimental parameters can be reduced significantly. Each experiment is repeated three times in order to observe the reproducibility of the glycolysis process. The analysis of variance of the results is performed using Minitab Software to obtain the contribution of the factors and their interactions over the response variable (BHET yield), and to determine the levels that maximize the BHET production.

Table 2

Factors and levels used in the factorial design experiments
Factors	Level 1	Level 2	Level 3
Temperature [ºC]	195	208	220
Time [min]	150	180	210
EG/PET [w/w]	2	4	6
ZnAc₂/PET [%w/w]	0.2	0.6	1.0

Table 3

Experimental glycolysis reaction with different PET waste
Run	Temperature [ºC]	Time [min]	Solvent [w/w]	Catalyst [%w/w]
#1	195	150	2	0.2
#2	195	180	4	0.6
#3	195	210	6	1.0
#4	208	150	4	1.0
#5	208	180	6	0.2
#6	208	210	2	0.6
#7	220	150	6	0.6
#8	220	180	2	1.0
#9	220	210	4	0.2

2.2.3. Analysis of products

A Differential Scanning Calorimetry, DSC, (TA Instruments DSC Q100 Model) is used for thermal analysis to determine the BHET purity. A Fourier Transform Infrared Spectrometer, FTIR, (Varian 670-IR with ATR Pike accessory) is used to identify the chemical structure of BHET. Commercial BHET is used to compare with the recovered products.

3.1. Optimization glycolysis process

The glycolysis results obtained with each type of PET waste are submitted to a Taguchi methodology to determine the levels that maximize the BHET production. In a Taguchi design, the mean is the average response for each combination of control factor levels. So, the means provide an estimate of BHET yield at each factor level to know how the four control factors affect the yield of BHET. Delta is the difference between the highest and lowest average response values for each factor. Table 4 shows the response for the means, where the ranks are based on Delta values; Rank 1 to the highest Delta value, Rank 2 to the second highest, and so on, to indicate the relative effect of each factor on the response. Figure 1 illustrates the influence of the conditions on the yield of BHET.

Table 4

Table response for the glycolysis PET waste means
Level	T [ºC]	t [min]	EG [w/w]	ZnAc₂ [%w/w]	Virgin PET
1	76.59	78.79	67.62	77.11
2	77.19	76.27	76.54	76.04
3	77.02	75.74	86.64	77.65
Delta	0.60	3.05	19.02	1.61
Rank	4	2	1	3
Level	T [ºC]	t [min]	EG [w/w]	ZnAc₂ [%w/w]	Multilayer PET
1	66.83	68.15	57.21	66.61
2	66.76	65.35	65.10	65.07
3	65.34	65.42	76.62	67.25
Delta	1.49	2.8	19.41	2.17
Rank	4	2	1	3
Level	T [ºC]	t [min]	EG [w/w]	ZnAc₂ [%w/w]	Highly colored PET
1	74.26	76.00	64.43	74.35
2	74.29	73.28	73.77	72.84
3	74.04	73.31	84.40	75.41
Delta	0.25	2.72	19.97	2.57
Rank	4	2	1	3
Level	T [ºC]	t [min]	EG [w/w]	ZnAc₂ [%w/w]	MSW PET
1	73.92	74.79	64.36	72.96
2	73.26	72.64	72.69	72.30
3	72.82	72.56	82.94	74.74
Delta	1.10	2.23	18.58	2.44
Rank	4	3	1	2

According to the results obtained by Taguchi (Table 4 and Fig. 1), it is observed that the EG to PET mass ratio (EG/PET) is the most significant factor in all studied PET waste, with a great difference with respect to the others in the Delta value. The next most influential factor is time (in all cases except MSW PET), followed by the ZnAc₂ to PET mass percentage ratio (ZnAc₂/PET). Finally, the least influential factor is temperature, although these last three factors have a very similar and low influence (similar values of Delta) on BHET yield [47, 53]. Therefore, through these results it can be confirmed that the behaviour of the factors studied is the same with all types of PET waste, as well as virgin PET, according to other authors [36, 52].

Focusing on the EG to polymer mass ratio, the best level to achieve the highest BHET yield, is the one with the highest amount of solvent used (6 w/w) due to the yield of the reaction increase with the amount of EG as show the Taguchi results in Fig. 1. As expected and according to literature, the use of an excess of EG is the most important parameter due to the polycondensation step is reversible and in the presence of excess of EG, glycolysis of PET occurs to promote the reverse reaction to give BHET [35, 37, 51, 47, 55–56].

About other factor studied, Fig. 1 illustrates that an increase in time reaction decrease BHET yield. According to literature, as reaction time continues increasing, BHET starts to dimerise and polymerise into oligomers [44]. A similar observation was made by other authors, who found that after a long time of reaction, equilibrium is attained in the obtaining of BHET [39, 49, 57]. So, this is the reason why in this work the highest yield is obtained with the lowest time, due to with a suitable temperature and catalyst, 150 min time is enough time to obtain the maximum yield. On the other hand, if lower times had been used, an increase in BHET yield would have been observed with the increase in time [51].

The effect of using catalyst in the reaction is touchable which decreases the reaction time required [43]. Sometimes, with further increase in the amount of a catalyst, the yield of BHET decreased [55], but in other case increase [49, 56]. This is because this factor is very related and depends on the temperature and reaction time used. For example, ZnAc₂ has the best efficiency when the temperature range is between 180 ºC to 195 ºC [43–44]. In this work, ZnAc₂ has the best efficiency using the highest mass percentage ratio to PET (1%w/w) as it can be seen in Fig. 1 and which is according to literature [37, 56]. However, decreasing the mass percentage ratio of ZnAc₂/PET to the lowest (0.2%w/w) only decreases the yield by 0.6% show a little influence of this factor on the glycolysis. So, due to economic and environmental reasons, it is not worth using the maximum level of catalyst.

Finally, temperature is the least influential factor on yield of BHET, having practically no influence compared to the others factors [20, 43]. Temperatures under 190 ºC produce an excess of sub-products and decrease the yield of BHET [48, 59] and higher temperatures over 208 ºC do not increase the yield of BHET [2, 43, 49]. This is in accordance with most of the reported works on glycolysis of PET which have been carried out at relatively low temperatures in the range of 190–200°C due to the yield of BHET at softening point temperatures is almost constant [47]. So, the best level chosen as optimum for this factor is the lowest (195 ºC) which agrees with literature [46].

According to Taguchi’s methodology, if the best levels of control factors are used (195 ºC, 150 min, 6 w/w EG/PET and 0.2%w/w ZnAc₂/PET), a maximum BHET yield will be obtained whose value would be between 79–88% depending the type of PET used. As expected, virgin PET gives the highest BHET yield (88.33%), followed by highly colored PET (86.41%), MSW PET (84.61%) and multilayer PET (79.28%). In order to demonstrate the theoretical results of Taguchi’s study, a confirmatory experiment is carried out with the optimum conditions to verify the BHET yield expected. In this last confirmatory experiment, the results are close to the theoretical, with yields between 77–87%. These results have only a difference of 2% compared to theoretical as it can be seen in Fig. 2. More in detail, virgin PET also gives the highest BHET yield (86.82%), followed by highly colored PET decreasing yield by only 2.6% (84.52%), MSW PET decreasing by 4.8% (82.65%) and the last is multilayer PET with more difference, decreasing by 11.4% compared to the virgin PET (76.93%), due to has more impurities in its composition. The yield of BHET obtained is similar or even higher considering literature with similar conditions [36–38, 54–56, 58, 60–64]. It has been demonstrating that PET nature, colour and multilayer material has low influence on BHET yield, being the results of complex PET waste similar to virgin PET [36, 54].

3.2. Recovery and reuse of EG

One of the inconvenient of the glycolysis process is the excessive use of EG to obtain high yield of BHET. According to the study carried out in this work and the results obtained by Taguchi with the virgin PET, with an EG/PET mass ratio of 6 w/w, the BHET yield obtained is 88.33%. When the EG/ PET mass ratio decreases to 4 w/w, the BHET yield also reduce by 11.4% (78.23%), reaching a reduction of 21.5% (69.31%) in case of 2 w/w. This excessive use of EG has its drawback in the economy of the process. Increasing the EG/PET mass ratio from 4 to 6 means that the cost of producing 1kg of BHET increases by 28% [48]. Therefore, it is necessary to recover the remaining EG of the process and reuse it for consecutive reactions, in order to optimise the glycolysis of PET making it economical and more environmentally.

The filtrate obtained from BHET crystallization contain mainly unreacted EG and water, and catalyst but at lower levels. A distillation of this solution is carried out recovering the EG which vary from 70–85% of the initial amount. So, for comparison purposes, the EG used for each new glycolysis cycle is 70% of recovered EG and 30% of fresh EG. The aim is to determine the number of cycles conduct with this mixture of recovered and fresh EG and evaluate the evolution of the BHET yield and purity. These global cycles are repeated 10 times. Figure 3 illustrates the evolution of the BHET yield using recovered EG, along the 10 consecutive glycolysis reactions for the different PET wastes evaluated. It is found that yield is maintaining constant at around 71–81% depending the type of PET waste. In general, BHET yield decreased up to 6.6–7.4% from the glycolysis carried out with fresh EG to the glycolysis carried out with 10 times recovered EG and with the same behaviour all types of PET waste studied. Although this observation could lead to assume that recovered EG is as reactive as fresh EG, it has to be pointed out that these results may be affected by increased catalyst concentration during the consecutive reactions [58].

3.3. Analysis of products

In order to check the purity of the BHET recovered after different PET waste glycolysis, this was analysed by means of a number of analytical techniques, and the results were compared with those corresponding to a commercial BHET sample.

Figure 4 shows characteristic signals of BHET molecule through FTIR spectrum. Bands at 2867 and 2960 cm^− 1 correspond to the stretching vibrations, asymmetric and symmetric, of the methyl and methylene groups (aliphatic CH₂ group) which indicate a depolymerization reaction. Bands at 3434 and 3281 cm^− 1 confirm the presence of O-H bond vibrations at chain terminations. The peak at 1132 cm^− 1 confirms the presence of hydroxyl groups related to C-OH alcohol bonds, while the peaks between 1282 − 1020 cm^− 1 are originated from the stretching vibrations of the C-O ester bonds. A transmission band at 1721 cm^− 1 confirms the presence of ester carbonyl group (C = O). Bands at 1509 − 1404 and 720 cm^− 1 correspond to the C = C bonds of the aromatic rings. All these results are according with literature [36, 38, 47, 64–65]. From all these observations it can be confirmed that the glycolysis products correspond with BHET, regardless of the type of PET waste and the use of recovered EG.

Figure 5 shows the DSC thermal analysis of the different BHET obtained from the glycolysis recorded by heating sample 250 ºC at 10 ºC·min^− 1. All the samples show only one sharp endothermic peak at 110 ºC which agrees with the known melting point of commercial BHET (at 112 ºC) [36–37, 44–45, 47, 65–66]. Besides, it can be confirmed that the product is BHET with a high purity due to does not appear any other peak. For example, according to literature, BHET dimmers, trimers and oligomers appear at 151 ºC, 170 ºC and 210 ºC; and a peak in the region of 250 ºC is attributed to the melting of the remaining solid PET [44–45, 63]. So, DSC chromatogram also demonstrate high level of purity of the monomers produced by glycolysis process of different PET waste and by the addition of recovered EG to the process.

In this work, a set of glycolysis process of virgin PET and different complex PET waste (highly colored PET, multilayer PET and sorting municipal waste PET) with EG as diol and ZnAc₂ as catalyst has been studied to optimise the process. The effect of various operation parameters has been investigated through Taguchy methodology in order to optimise glycolysis and efficiently recover its purified monomer, BHET. The sequence of the main effects with higher influence on the glycolysis to increase yield of monomer, in ascending order, is EG/PET mass ratio, reaction time, ZnAc₂/PET mass percentage ratio and temperature. EG/PET mass ratio has the highest influence on the BHET yield, achieving a growth of 27.4% increasing the mass ratio from 2 to 6 w/w. However, the BHET yield does not vary as much with the rest of the factors, less than 1%. Applying the best conditions chosen (195 ºC, 150 min, 6 w/w EG/PET and 0.2%w/w ZnAc₂/PET), gives yields of 86.82%, 84.52%, 82.65% and 76.93% corresponding to virgin PET, highly colored PET, MSW PET and multilayer PET, showing that all of them have similar yield to the one coming from virgin PET, being the multilayer PET the one with the greatest decrease respect virgin PET, 11. 4%, due to has more impurities in its composition, demonstrating that PET nature and colour has little influence on BHET yield.

Other point studied on this work is the recovery of EG due to the excessive use of solvent to achieve high yield of BHET, damaging the economics of the process and the environment. Through distillation, a 70% of EG is recovered which is used adding 30% of fresh EG in new glycolysis cycles. This gives very good results, showing that the use of recovered EG does not affect the yield and quality of BHET, maintaining constant at around 71–81%, and decreasing only about 7% during 10 times glycolysis cycles. This trend has been observed in all the different PET waste evaluated.

Finally, the DSC and FTIR results have verified that the BHET products derived from all types of PET waste and with the use of recovered EG, have been equivalent to the one derived from virgin PET with high purity and similitude with commercial BHET, so PET nature and colour also have no influence on the quality and purity of the monomer obtained.

Thus, it has been demonstrated that glycolysis with EG and ZnAc₂ is suitable for chemical recycling of PET waste with more complex nature and characteristics (highly colored PET, multilayer PET and MSW PET) than virgin PET, used as a reference waste in this study. Therefore, glycolysis has been verified as a process with a great relevance given the increased presence of this type of complex waste, and a promising and efficient option for the recycling of these non-mechanically recoverable PET waste that currently ending up in landfill or incinerated.

Acknowledgements

The authors wish to acknowledge the confidence for and economic support of the Spanish Ministry of Education and Science to this work.

Funding: This study was funded by the Spanish Ministry of Education and Science.

Competing interests: The authors have no relevant financial or non-financial interests to disclose.

Author Contributions: All authors contributed to the study conception, material preparation, data collection and analysis. The manuscript was written by Alicia Aguado and all authors read and approved the final manuscript.

(Note: The affiliation of the authors Lucía Becerra and Lidia Martínez is only the city and country due to these people are no longer working at CARTIF Centro Tecnológico¹).

Data Availability: All data generated or analysed during this study are included in this published article.

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Glycolysis optimization of different complex PET waste with recovery and reuse of ethylene glycol

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Abstract

Figures

1. Introduction

2. Materials And Methods

2.1. Materials

2.2. Methods

2.2.1. Glycolysis processes

2.2.2. Glycolysis optimization by Taguchi’s methodology

2.2.3. Analysis of products

3. Results

3.1. Optimization glycolysis process

3.2. Recovery and reuse of EG

3.3. Analysis of products

4. Conclusions

Declarations

References

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Version 1

Run	Temperature [ºC]	Time [min]	Solvent [w/w]	Catalyst [%w/w]
#1	195	150	2	0.2
#2	195	180	4	0.6
#3	195	210	6	1.0
#4	208	150	4	1.0
#5	208	180	6	0.2
#6	208	210	2	0.6
#7	220	150	6	0.6
#8	220	180	2	1.0
#9	220	210	4	0.2

Run	Temperature [ºC]	Time [min]	Solvent [w/w]	Catalyst [%w/w]
#1	195	150	2	0.2
#2	195	180	4	0.6
#3	195	210	6	1.0
#4	208	150	4	1.0
#5	208	180	6	0.2
#6	208	210	2	0.6
#7	220	150	6	0.6
#8	220	180	2	1.0
#9	220	210	4	0.2

Run	Temperature [ºC]	Time [min]	Solvent [w/w]	Catalyst [%w/w]
#1	195	150	2	0.2
#2	195	180	4	0.6
#3	195	210	6	1.0
#4	208	150	4	1.0
#5	208	180	6	0.2
#6	208	210	2	0.6
#7	220	150	6	0.6
#8	220	180	2	1.0
#9	220	210	4	0.2