Activity features of catalysts for thermocatalytic hydrogenation processing of polymer waste published by Ural Federal University eISSN 2411-1414; chimicatechnoacta.ru ARTICLE 2022, vol. 9(3), No. 20229302 DOI: 10.15826/chimtech.2022.9.3.02 1 of 6 Activity features of catalysts for thermocatalytic hydrogenation processing of polymer waste Zheneta Kh. Tashmukhambetova a , Tanakoz O. Kalamgali a , Yermek A. Aubakirov a , Larissa R. Sassykova a* , Firuza Zh. Akhmetova b , Albina S. Alpysbay a a: Al-Farabi Kazakh National University, Almaty 050040, Kazakhstan b: Zhangirkhan West-Kazakhstan Agrarian Technical University, Uralsk 090009, Kazakhstan * Corresponding author: larissa.rav@mail.ru This paper belongs to the CTFM'22 Special Issue: https://www.kaznu.kz/en/25415/page. Guest Editors: Prof. N. Uvarov and Prof. E. Aubakirov. © 2022, the Authors. This article is published in open access under the terms and conditions of the Creative Com- mons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Abstract The aim of this study was to obtain new catalysts for the processing of carbon-containing polymer waste based on polyethylene and poly- propylene, represented mostly by lids from beverages bottled in plas- tic containers, which accumulate in huge quantities in landfills, by the method of thermocatalytic hydrogenation into liquid fuels and oth- er products. The process was carried out in the presence of fuel oil as a binder, a source of hydrogen and additional hydrocarbons. Thus, two tasks can be solved simultaneously: recycling the polymer waste and obtaining the alternative raw materials from the polymer waste in or- der to save resources and improve the environmental situation in gen- eral. New catalysts based on activated zeolite modified with Mo(VI) and W(VI) salts of various concentrations for the thermocatalytic hy- drogenation processing of waste plastics into motor fuels were synthe- sized. The composition, structure, morphology and adsorption proper- ties of the catalysts were determined by different physicochemical methods. The suitability of the obtained catalysts for use in the thermocatalytic hydrogenation processing of plastic waste into fuels was determined. The catalysts were tested during the processing of a mixture of polyethylene-polypropylene: a paste-forming agent (fuel oil) at T=450 °C and a pressure of 0.6 MPa. The individual and group composition of gasoline, diesel and gas oil fractions was determined by chromatography coupled with mass spectrometry. The maximum yield of the gasoline fraction (16.9 wt.%) and diesel fraction (39.31 wt.%) was obtained on a 2%W(VI)/diatomite catalyst. Keywords polymer waste thermocatalysis hydrogenation catalyst fuel diatomite Received: 12.06.22 Revised: 28.06.22 Accepted: 30.06. 22 Available online: 05.07.22 1. Introduction The problem of environmental pollution with carbon- containing industrial and household waste based on poly- mer and rubber products needs to be addressed. The main ways of the disposal of such waste are incineration and storage [1–15]. If we consider these carbon-containing wastes as an alternative source of hydrocarbons, then the development of new integrated technologies based on the use of effective catalysts will allow us to fully solve the existing environmental threats in the future. Moreover, it will make it possible to saturate the market with the nec- essary fuels, products and materials [16–23]. In the laboratory of the Department of Physical Chem- istry, Catalysis and Petrochemistry of the Al-Farabi Ka- zakh National University, tests of new composite catalysts for the thermocatalytic hydrogenation processing of poly- mer waste were carried out. Composites based on Mo(VI) and W(VI) salts deposited on a diatomite substrate were studied for the first time as catalysts. As is known, diatomite is a natural aluminosilicate material of a macroporous structure with a large internal surface formed as a result of the vital activity of organisms – diatomies. It has a complex “cemented” composition and contains inclusions of various minerals, such as silica, quartz, kaolin, opal, etc. Such a structure http://chimicatechnoacta.ru/ https://doi.org/10.15826/chimtech.2022.9.3.02 http://orcid.org/0000-0003-4125-4114 http://orcid.org/0000-0003-0225-0049 http://orcid.org/0000-0001-5405-4125 http://orcid.org/0000-0003-4721-9758 http://orcid.org/0000-0002-8869-3053 http://orcid.org/0000-0001-5717-0842 mailto:larissa.rav@mail.ru https://www.kaznu.kz/en/25415/page http://creativecommons.org/licenses/by/4.0/ https://crossmark.crossref.org/dialog/?doi=https://doi.org/10.15826/chimtech.2022.9.3.02&domain=pdf&date_stamp=2022-7-5 Chimica Techno Acta 2022, vol. 9(3), No. 20229302 ARTICLE 2 of 6 allows us to consider it as a natural ion exchanger and adsorbent, as well as a substrate for the deposition of active catalysts [24–27]. The aim of this work was to synthesize new catalysts for the processing of carbon-containing polymeric wastes based on polyethylene and polypropylene, mainly represented by lids from drinks poured into plastic containers, which accumulate in large quantities in landfills, by thermal catalytic hydrogenation into liquid fuels and other products. The process was carried out in the presence of fuel oil as a binder, a source of hydrogen and additional hydrocarbons. 2. Experimental In this work, diatomite from the Aktobe deposit of the Re- public of Kazakhstan was studied. The concentration of the active metal in the composite was varied in the range from 1 to 2 wt.%. The effect of 4 different catalysts on the thermocatalytic hydrogenation processing of plastic waste was studied: diatomite activated by the acid-free method, 2% Mo(VI)/diatomite, 2% W(VI)/diatomite, and (1%Mo(VI) and 1%W(VI))/diatomaceous earth. As a feed- stock, polymeric wastes crushed to the state of crumbs from a waste processing plant in Almaty, represented by a mixture of polyethylene and polypropylene lids, were studied. To impart viscous paste-forming properties to the polymer mixture, fuel oil with a boiling point of more than 350 °С, obtained during the distillation processing of oil from the Kumkolskoe field, was used. As is known from our previous studies [6, 28–31], fuel oil was used not only as a paste-forming agent, but also as an additional source of hydrocarbons and hydrogen necessary for the hydro- genation reaction to proceed. In order to determine the composition, structure, morphology and adsorption prop- erties of the studied catalysts, such physico-chemical methods of analysis as X-ray fluorescence, IR spectrosco- py, Scanning Electron Microscopy (SEM), adsorption ni- trogen porometry (BET), X-ray Diffraction analysis (XRD), thermogravimetric analysis (TGA) and differential ther- mogravimetric analysis (DTGA) were used. 3. Results and discussion The presence of tungsten immobilized on the surface of diatomite during ion exchange in the composition of cat- alysts was established by X-ray fluorescence (Figure 1). The process of ion exchange was accompanied by a de- crease in the structure of diatomite of the concentrations of potassium, chromium, iron, as well as aluminum and silicon, which may indicate a possible destruction of the M–O–Si (where “M” is a metal) bond, a slight destruction of the Si–O–Si bond, and a partial removal of the six- coordinate aluminum. Figure 1 Data of X-ray fluorescence analysis: 2% W(VI)/diatomite catalyst (a); the catalyst 1% Mo(VI) – 1% W(VI)/ diatomite (b); an activated diatomite (c). (b) (a) (c) Chimica Techno Acta 2022, vol. 9(3), No. 20229302 ARTICLE 3 of 6 So, for example, in the composition of activated diato- mite, the concentration of Si was 65.30%, in 2% W(VI)/diatomite – 33.40%; in 2% Mo(VI)/diatomite – 45.40% in (1% Mo(VI) and 1% W(VI))/diatomite – 49.10%, respectively. The Al concentration was 12.22%, in 2% W(VI)/diatomite – 8.74%; in 2% Mo (VI)/diatomite – 22.45% in (1% Mo(VI) and 1% W(VI))/diatomite – 0%, respectively. The presence of molybdenum in the catalyst samples could not be determined by this method. The study of the morphology of catalysts by SEM at dif- ferent magnifications showed the presence in the images of distinct sections of the cellular structure inherent in diatomite, as well as loose and convex oval inclusions, most likely corresponding to the sites of destruction of diatomite and the introduction of molybdenum and tung- sten ions into the substrate structure as a result of ex- change with other ions (Figure 2). The images clearly show integral fragments of the flaps of various organisms – diatoms with their inherent cellular structure, macropores with the inclusion of meso- and mi- cropores, which indicates the heterogeneity of the surface of the diatomite. The samples of the studied catalysts, regard- less of the content of the active metal, have a sufficiently de- veloped specific surface area and are of interest for studying their structure by nitrogen porometry with a view to further use as a carrier of the active phase of the catalyst. According to the data of the BET analysis (Table 1), in pure diatomite, the adsorption and desorption indices dif- fer from those in the samples of catalysts with Mo and W active centers immobilized on them. This is also apparent- ly due to a change in the structure of the catalyst after ion exchange treatment. The maximum value of the specific surface corresponds to the sample of 2% W(VI)/diatomite – 42.71 m2/g. Figure 2 Study of the morphology of the catalysts by SEM: 2% W(VI)/diatomite (10 μm (a), 20 μm (b), 100 μm (c)); 2% Mo(VI)/diatomite (10 μm (d), 20 μm (e), 100 μm (f)); 1% Mo(VI) – 1% W(VI)/diatomite (10 μm (g), 20 μm (h), 100 μm (i)). Chimica Techno Acta 2022, vol. 9(3), No. 20229302 ARTICLE 4 of 6 Table 1 Determination of the specific surface area of catalysts by the BET method. Catalyst Sspecific surface area, m²/g 2% W(VI)/diatomite 60.76 2% Mo(VI)/diatomite 42.71 1% Mo(VI) – 1% W(VI)/diatomite 14.39 Activated diatomite 34.41 The study of catalyst samples by IR spectroscopy showed the presence in the spectra, mainly, of absorption bands characteristic of diatomite, since it has a complex composition and contains, in addition to Si and Al oxides, a number of oxides of various metals, such as Mn, Fe, Ti, Cr, K, etc. However, during the processing of Mo(VI) and W(VI) diatomite separately and with the total presence, a slight shift of the peak at 1098.94 cm–1 from 0.038 to 0.045 cm–1 is observed, corresponding to strong valence and deformation vibrations of Si–O–Si silica and quartz, as well as weak vibrations in the region of 460, 550, 804, 951 cm–1, valence fluctuations at 3450–3500 cm-1, correspond- ing to the OH group; valence fluctuations in the region of 3630–3695 cm–1, characteristic of clay and mica. The activated diatomite and W(VI)/diatomite catalyst samples were analyzed by TGA and processed by DTGA. As the analyzes showed, the destruction of samples under the influence of temperature occurs intensively up to 130– 135 °С, then it somewhat slows down until reaching 450– 470 °С and then the final destruction occurs up to 898 °С (Figure 3 and 4). The TGA curves for both catalysts are ap- proximately the same. The greatest mass loss of the sample, therefore, will be achieved already at the temperature of thermodestructive hydrogenation processing, which is 450 °С. However, the percentage of mass loss by the acti- vated diatomite is insignificant and amounts to only 4.553%, and by the W(VI)/diatomite catalyst – 6.323%, respectively, which may indicate their resistance to tem- perature and the formation of disilicates (600–650 °С) with their further transition to the melt above 700 °С. Figure 3 Data of TGA and DTA analysis of activated diatomite. Figure 4 Data of TGA and DTGA analysis of the catalyst W(VI)/diatomite. Based on the X-ray phase analysis (XRD) of the studied catalysts, it was also found that the main contribution is made by the crystalline and amorphous phases of diato- mite and minor fluctuations in intensity may be due to the presence of Mo(VI) and W(VI) salts. The obtained catalysts were tested for processing a polyethylene-polypropylene mixture in the presence of a paste-forming agent at T = 450 °С and a pressure of 0.6 MPa. The maximum yield of the gasoline fraction (Tboiling point=0–180 °С) was observed on a catalyst of 2%W(VI)/diatomite – 16.90 wt. %. The material balance of the most significant process under given conditions is presented in Table 2. Table 3 shows the group composition of hydrocarbons of the gasoline fraction obtained on the catalyst 2% W/diatomite. The hydrocarbon composition of distillates obtained on the synthesized catalysts was studied by chromatography– mass spectrometry. The chromatogram of the gasoline fraction boiling in the range of 0–180 °C obtained on a 2% W/diatomite catalyst is shown in Figure 5. The main conclusions obtained as a result of the physi- cochemical studies and experimental tests of catalysts in this work are in agreement with the data mentioned in the scientific literature [2, 5, 32–41]. Table 2 Material balance of the thermocatalytic hydrogenation processing of polymer waste on a catalyst 2% W(VI)/diatomite (T = 450 °С, P = 0.6 MPa). Taken Wt.% Consumption Wt.% Catalyst 2.00 Gasoline fraction 0–180 °С 16.90 Polymer waste 49.02 Diesel fraction 180–250 °С 39.31 Heavy gas oil fraction 250–320 °С – Fuel oil 49.02 Losses, water, sediment 30.08 Gas 13.68 Total 100 Total 100 Table 3 Chemical composition of the gasoline fraction (Tboiling point = 0–180 °С) obtained on a 2% W/diatomite catalyst. Liquid fraction Hydrocarbons, % Alkanes Isoalkanes Alkenes Cyclo alkanes Cycloal- kenes Aromatic Heterocom- pounds 0–180 °С 58.65 4.08 7.01 5.48 – 22.83 1.08 Chimica Techno Acta 2022, vol. 9(3), No. 20229302 ARTICLE 5 of 6 Figure 5 Chromatogram of the gasoline fraction (Tboiling point = 0–180 °C) obtained on a 2% W(VI)/diatomite catalyst. 4. Conclusions In this paper, the new composite catalysts based on acti- vated zeolite modified with Mo(VI) and W(VI) salts of dif- ferent concentrations for the thermocatalytic hydrogena- tion processing of plastic waste into motor fuels were de- veloped. The basic physicochemical properties of the syn- thesized catalysts: the elemental and phase composition, surface morphology, specific surface area and the optimal destruction temperature were obtained. Based on the re- sults of the experiments and the calculation of the materi- al balance of the process, it was found that the catalyst 2% W/diatomite is the most active in the yield of the total liquid product. The effectiveness of the obtained compo- site catalysts is confirmed by the group hydrocarbon com- position of fractions boiling up to 180 °C, from 180 to 250 °C, from 250 to 320 °C, determined by gas-liquid chromatography-mass spectrometry. Supplementary materials No supplementary materials are available. Funding This research had no external funding. Acknowledgments None. Author contributions Conceptualization: Z.K.T. Data curation: Z.K.T., L.R.S. Formal Analysis: Y.A.A., L.R.S. Funding acquisition: Y.A.A., Z.K.T. Investigation: Z.K.T., T.O.K., A.S.A., F.Z.A. Methodology: Z.K.T., Y.A.A. Project administration: Y.A.A. Resources: Z.K.T., Y.A.A., T.O.K. Software: L.R.S. Supervision: L.R.S., Z.K.T. Validation: Z.K.T., L.R.S. Visualization: Z.K.T., L.R.S., Y.A.A. Writing – original draft: Z.K.T., L.R.S. Writing – review & editing: Z.K.T., T.O.K., L.R.S. Conflict of interest The authors declare no conflict of interest. Additional information Author IDs: Zheneta Kh. Tashmukhambetova, Scopus ID 56459076400; Yermek A. Aubakirov, Scopus ID 55447002200; Larissa R. Sassykova, Scopus ID 56178673800; Firuza Zh. Akhmetova, Scopus ID 57211321422. Websites: Al-Farabi Kazakh National University, https://www.kaznu.kz/en; Zhangirkhan West-Kazakhstan Agrarian Technical Uni- versity, https://wkau.kz/en/. References 1. Soares FA, Steinbüchel A. Natural rubber degradation prod- ucts: Fine chemicals and reuse of rubber waste. Eur Polym J. 2022;165:111001. doi:10.1016/j.eurpolymj.2022.111001 2. Datta J, Kopczyńska P. From polymer waste to potential main industrial products: Actual state of recycling and recovering. Crit Rev Environ Sci. 2016;46(10):905–946. doi:10.1177/00952443221087351 3. Dang TH, Nguyen XH, Chou ChL, Chen BH. 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