Spent Fluid Catalytic Cracking Research Articles

IMPACT OF ALUMINOSILICATE WASTES ON THE HYDRATION, PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT PASTE

The impact of aluminosilicate wastes (spent fluid catalytic cracking catalyst from oil companies and metakaolin containing waste from the production of expanded glass granules) on the hydration and compressive strength of the cement paste was analysed when a proportion of cement was replaced by one waste material or two waste materials. The article presents results of X-ray diffraction and thermal analysis of hardened cement pastes. It was determined that the spent catalytic cracking catalyst accelerates cement hydration because of its high surface area and pozzolanic activity; and metakaolin containing waste has a retarding effect. X-ray diffraction and thermal analysis showed that the specimens with metakaolin containing waste had the lowest amount of portlandite, and the compressive strength of these specimens was similar to that of the control specimens when a superplasticizer was used. It was found that a mix of aluminosilicate wastes has a different effect on cement hydration and makes it possible to adjust the hydration time of the binder within a certain interval.

Mild activation of spent fluid catalytic cracking (FCC) catalysts for the pilot synthesis of zeolite a with commercial quality and excellent Co2+ removal ability

Fluid catalytic cracking (FCC) plays a pivotal role in the transformation of crude oil into fuels and bulk chemicals, crucial within petroleum refining. However, it also generates a substantial volume of hazardous spent FCC catalysts. Thus, developing an effective method to convert these hazardous spent catalysts into high-value products is essential for the sustainable advancement of the petrochemical industry. In this study, we introduce a simple, mild, and environmentally friendly activation approach for spent FCC catalysts, followed by a straightforward synthesis of zeolite A meeting commercial standards. The resulting zeolite A (referred to as SFCC-A) exhibited high crystallinity, exceptional selectivity, and efficient Co2+ removal capabilities from wastewater. Even at a solid/liquid ratio of 1/1000 g·mL−1, a removal efficiency of approximately 99 % was achieved. SFCC-A demonstrated a high adsorption capacity (180.5 mg·g−1) for Co2+ and a broad operational pH range (4–8). Furthermore, the pilot synthesis was successfully scaled up to 100 L, maintaining consistent product performance compared to lab-scale production. Additionally, we investigated the evolution of species during the activation of spent FCC catalysts using multiple characterization techniques, elucidated the phase diagram of SFCC-A and the crystallization process under optimal conditions. The combination of a simple, mild, and eco-friendly activation method with a convenient synthesis process, yielding high-value zeolite A products, transforms spent FCC catalysts into valuable resources rather than hazards.

Use of spent fluid catalytic cracking catalyst (FCC) in Limestone Calcined Clay Cement (LC3) systems: Studies in pastes and mortars

This study evaluates the substitution of calcined clay for a waste from the petrochemical industry, spent fluid catalytic cracking catalyst (FCC), as a source of reactive aluminosilicates in Limestone Calcined Clay Cements (LC3) systems. Three carbonate types were used to make cement-type LC3: a high-purity calcium carbonate, waste from the marble industry, and another from a dolomite soil source. LC3 blends were prepared by mixing 50 wt% OPC, 5 wt% calcium sulfate dihydrate, 30 wt% FCC and 15 wt% from each carbonate source. A mixture than substituting the carbonate source for a siliceous source was prepared to analyse the influence of carbonate phases in LC3 systems. The hydration process of the LC3 blends was studied by X-ray diffraction, thermogravimetric analyses, isothermal calorimetry and FESEM. Mechanical properties were studied by measuring compressive strength at 7, 28 and 90 days. The obtained results corroborated that the mortars prepared with LC3 cements using the FCC obtained higher compressive strength than the control mortar prepared with ordinary Portland cement (OPC) at 28 and 90 curing days. It has been demonstrated that FCC is a by-product that can substitute calcined clay, and the different sources of carbonates such as high purity, waste or contaminated with magnesium do not interfere with the performance of this type of cement.

In vitro assessment of cytotoxicity of spent fluid catalytic cracking refinery catalysts on cell lines and identification of critical toxic metals

The Purpose of the present study was to quantify the responses of ten cell lines (HeLa, HepG2, HEK293, MDA-MB-231, A498, A549, A357, 3 T3, BALB-C3 T3, and NIH-3 T3) to spent fluid catalytic cracking catalysts (SFCCCs) from different petroleum refineries, and relate these responses to metal concentrations of SFCCC leachates (SFCCCLs). Cytotoxicity of SFCCCs were significantly different depending on cell lines. A357 and 3 T3 cell were the most sensitive, and A498 and HeLa cells were the least sensitive. HEK293 cells showed the least fluctuation in toxic response to different SFCCCLs among all cells. Cytotoxic IC50 values of SFCCCs to 7 kinds of cells were the most correlated with vanadium (V) concentration in SFCCCLs. V is the most critical toxic factor of SFCCC. Glutathione synthesis was induced in HepG2 cells exposed to higher concentrations of SFCCCLs. SFCCCLs with low concentration of V can induce the decrease of GSH/GSSG ratio in HepG2 cells, suggesting that high concentration of V inhibits the detoxification of glutathione.

A Study on the Microstructure and Mechanical Properties of Portland Cement Incorporating Aluminosilicate Waste.

The influence of aluminosilicate pozzolanic waste, specifically spent fluid catalytic cracking waste (FCCW) and metakaolin waste (MK) from the expanded glass industry, on the properties of hardened Portland cement paste were analysed. The study involved replacing part of cement with FCCW and MK and observing their impact on the hydration, microstructure, density, and compressive strength of hardened cement paste. Various analysis methods were employed, including X-ray diffraction (XRD), thermogravimetric analysis (TG), and scanning electron microscopy (SEM), to understand the changes in the structure of the hardened cement paste during hydration. The findings revealed that FCCW tends to accelerate the cement hydration process due to its high surface area and pozzolanic activity. Notably, the formation of portlandite crystals was observed on FCCW particle surfaces in a specific direction. These crystals appeared smaller and developed in different directions in compositions containing a composite binder with mixture of FCCW and MK in a ratio 1:1. This could be influenced by pozzolanic reactions activated by fine particles of MK and the formation of calcium silicate hydrates (C-S-H) and calcium alumino silicate hydrates (C-A-S-H) in the presence of portlandite. The XRD and TG results indicated that the specimens containing a composite binder exhibited the least amount of portlandite. The compressive strength of these specimens increased compared to the control specimens, although the amount of cement was 9% lower.

Biodiesel synthesis using spent FCC catalyst and CaO from a mixture of sunflower oil and oleic acid

A physical mixture of two heterogeneous catalysts, calcium oxide (CaO) and spent fluid catalytic cracking (SFCC) catalyst, was used to produce biodiesel from a mixture of refined sunflower oil (RSFO) and 5 wt% oleic acid. The reaction was performed with a 6: 1 M ratio of methanol to oil at 65 °C and 3 wt% catalyst loading. The SFCC catalyst loading was also varied to investigate its effect on soap formation and biodiesel production. The presence of the SFCC catalyst reduced the reaction time from 14 h to 7 h to achieve conversion >99 %. It also decreased the soap formation compared with the reaction catalyzed by CaO alone. The lowest oleic acid conversion to soap (~20%) was obtained for CaO + 20 % SFCC case. Calcium diglyceroxide (CaD) was also tested as a catalyst – it further reduced the reaction time to 1 h for 99 % conversion.

Bioleaching of metals from spent fluid catalytic cracking catalyst using adapted Acidithiobacillus caldus.

In this study, an adapted bioleaching strain of Acidithiobacillus caldus UVS10 was successfully developed. Batch tests and tests in bioreactor were conducted to evaluate the metals bioleaching performance of A. caldus UVS10 to spent FCC catalyst (SFCCC). Results of batch experiments showed the bioleaching efficiency of Ni, V, La, and Ce in SFCCC reached 19.40%, 22.06%, 53.75%, and 59.56%, respectively. High SFCCC pulp density inhibited the leaching of metals. Sb leaching was inhibited in acidic environment caused by A. caldus UVS10. Contents of Ni, V, La, and Ce in extracellular polymeric substances (EPS) were significantly higher than those intracellular. Accumulation of metal in EPS and cytosol increased with the increase of SFCCC pulp density. V was less intercepted by EPS than Ni, La, and Ce, because of lower toxicity. Experimental results in bioreactor showed that Ni, V, La, and Ce could be effectively leached by A. caldus UVS10 under 10% pulp density. The aeration and stirring operating environment in bioreactor improved the leaching efficiency of metals in SFCCC. After bioleached in bioreactor, the available fraction content of four metals in SFCCC decreased significantly. Ecological risk analysis demonstrated the environmental risks of bioleached SFCCC were significantly lower than raw SFCCC. Different reaction kinetic models were used to represent metals leaching behavior under bioleaching of A. caldus UVS10, leaching of La and Ce showed good agreement with the product layer diffusion model, while Ni and V leaching kinetics fit well with the surface chemical reaction models.

Improving catalytic performance of Cu-SSZ-13 for NOx abatement via in-situ introduction of La and Ce from spent catalyst

Designing a cost-effective and fast fabrication Cu-SSZ-13 with improved selective catalytic reduction of NO by ammonia (NH3-SCR) performance remains an open question. Here we report that LaCe-SSZ-13 zeolites were synthesized from spent fluid catalytic cracking catalyst within 12 h. After ion-exchanging with CuSO4 solution, the obtained LaCeCu-SSZ-13 catalysts exhibit significantly higher catalytic activity and hydrothermal stability than conventional Cu-SSZ-13. Various characterizations reveal that La and Ce modification not only facilitates the disperse of isolated Cu2+ species, but also effectively mitigates dealumination and inhibits copper species aggregation after hydrothermal aging. In-situ diffuse reflection infrared Fourier transform spectrum analyses demonstrate that La and Ce modification can accelerate the adsorption capacity for NH3 and NOx and promote the decomposition of NH4NO3 intermediate species on the catalyst, benefiting the improvement of low-temperature activity. The combination of experiments and theoretical calculations further demonstrate that the most stable positions of La and Ce are on different eight-membered rings in SSZ-13, and then Cu2+ ions tend to enter eight-membered rings to enhance the NH3 adsorption capacity and decrease the H2O adsorption capacity, which results in higher low-temperature activity and hydrothermal stability than Cu-SSZ-13. Our work provides a feasible strategy for preparing the efficient rare-earth-modified Cu-zeolite based NH3-SCR catalyst for nitrogen oxide abatement.

Home Trash Biomass Valorization by Catalytic Pyrolysis

With the increase in population, large amounts of food waste are produced worldwide every day. These leftovers can be used as a source of lignocellulosic waste, oils, and polysaccharides for renewable fuels. In a fixed bed reactor, low-temperature catalytic pyrolysis was investigated using biomass gathered from domestic garbage. Thermogravimetry, under N2 flow, was used to assess the pyrolysis behavior of tea and coffee grounds, white potato, sweet potato, banana peels, walnut, almonds, and hazelnut shells. A mixture of biomass was also evaluated by thermogravimetry. Waste inorganic materials (marble, limestone, dolomite, bauxite, and spent Fluid Catalytic Cracking (FCC) catalyst) were used as catalysts (16.7% wt.) in the pyrolysis studies at 400 °C in a fixed bed reactor. Yields of bio-oil in the 22–36% wt. range were attained. All of the catalysts promoted gasification and a decrease in the bio-oil carboxylic acids content. The marble dust catalyst increased the bio-oil volatility. The results show that it is possible to valorize lignocellulosic household waste by pyrolysis using inorganic waste materials as catalysts.

Thermodynamic modelling of cements clinkering process as a tool for optimising the proportioning of raw meals containing alternative materials

The valorisation of waste or by-products in Portland clinker production is a promising alternative for developing sustainable cements. The complexity of the chemical reactions during clinkering demands an adequate dosing method that considers the effect of feedstock impurities to maximise the potential substitution of natural resources by waste or by-products, while guaranteeing the clinker reactivity requirements. This study proposes a raw meal proportioning methodology for optimising co-processing of natural feedstocks with alternative raw materials in clinker production, intending to reduce the content of natural raw materials needed, while promoting an optimal clinker reactivity. A thermodynamic modelling sequence was developed considering the variability of raw materials composition and heating temperatures. The model was then validated by comparing simulation outcomes with results reported in previous studies. An experimental case study was conducted for validation of the proposed method using a spent fluid catalytic cracking catalyst (SFCC), a by-product from the oil industry as an alternative alumina source during clinkering. The modelling simulations indicated that substitution of natural feedstocks by 15 wt% SFCC promotes the formation of reactive clinkers with more than 54% tricalcium silicate (C3S). Mixes with the potential to form the highest C3S were then produced, and heating microscopy fusibility testing was applied for evaluating the clinkers’ stability. The main factors governing the reactivity and stability of the clinker phases were the melt phase content, alumina modulus, and formation of C3S and dicalcium silicate (C2S). The self-pulverisation of clinker during cooling was observed in selected mixes, and it is potentially associated with high viscosity and low Fe content in the melt phase. The proposed framework enables optimisation of the dosing of raw meals containing alternative alumina-rich feedstocks for clinker production and allows a deeper interpretation of limited sets of empirical data.

Reusing spent fluid catalytic cracking catalyst as an adsorbent in wastewater treatment applications

Spent fluid catalytic cracking (FCC) catalyst is a waste from oil industry generated in very high amounts globally, being a major environmental burden as it is mostly landfilled. The direct use of this waste in wastewater treatment applications is rare, and the present study aims to fill the existing research gap. This is the first systematic investigation regarding the use of spent FCC catalyst as adsorbent material, for extracting methylene blue (MB) (pollutant model molecule) from wastewater.The effects of contact time (5 min–48 h), adsorbent dosage (0.5–3 g/L), adsorbate concentration (5–400 mg/L), and the reaction kinetics, were investigated. MB concentrations above 200 mg/L achieved a maximum uptake of 90.8 mg/g after 48 h. For MB concentrations below 10 mg/L, very fast dye removal was observed, reaching 100% after 1 h. The adsorption of MB followed a pseudo-second-order model (chemisorption), and the Langmuir model better described the experimental data (monolayer adsorption). The novel strategy here reported is aligned with key Sustainable Development Goals – 6, 9, 12 and 13 – and with the concept of the Circular Economy, and these results might add value to industrial waste whose availability is still expected to grow substantially soon.

G-C3N4/TiO2 for gas-phase formaldehyde photodegradation under visible light in the humidity control coatings

BackgroundsThe control of relative humidity and degradation of volatile organic compounds are regarded as major considerations in the enhancement of living quality in the indoor environment. From the viewpoints of circular economy, the valorization of inorganic wastes to prepare green building materials is crucial. MethodsFor the practical applications, the multifunctional coatings, applied in the indoor humidity control and photocatalytic degradation of formaldehyde, are prepared by recovering inorganic wastes (i.e., white carbon (WC) and spent fluid catalytic cracking catalysts (sFCCC)) and photocatalysts (graphitic carbon nitride/TiO2, denoted as GCN/TiO2) via a simple sol-gel method. Various physicochemical and analytic tools are used to characterize the coating properties and performance. Significant findingsCompared to commercial coatings, the prepared multifunctional coatings (i.e., W/B/S-47/47/6, where W, B and S represent the weight percentage (%) of white carbon, bassanite and sFCCC, respectively) have superior textural properties which can improve the buffering ability of indoor humidity. Moreover, the W/B/S-47/47/6 coatings exhibit the surpassing photodegradation of formaldehyde over commercial coatings by ca. 3 times. The higher charge transfer kinetics and greater thermodynamic driving force toward superoxide radical formation are responsible for the improved photocatalytic activity of W/B/S-47/47/6 coatings. According to the toxicity characteristic leaching procedure tests, no evident leaching heavy metals are observed, which provides an environmental-friendly and economical route for valorization of inorganic wastes.

Silica wastes derived multifunctional coatings for formaldehyde photodegradation and autonomous indoor humidity buffering

To maintain a comfortable and healthy indoor environment without large amounts of energy consumption is of great importance. The progress of multifunctional indoor coatings with formaldehyde photodegradation and humidity buffering capability is necessary. From the viewpoints of circular economy, the preparation of effective photocatalysts (denoted as sFCC/GCN-x and ESF/GCN-y) via the decoration of recycling industrial wastes (i.e., spent fluid catalytic cracking catalysts (sFCC) and enhancement silica fume (ESF)) onto graphitic carbon nitride (GCN) by using a simple route is reported. The obtained results show that the prepared sFCC/GCN-0.15 and ESF/GCN-0.15 photocatalysts have the rate constants of formaldehyde degradation of 0.0075 and 0.0082 min−1, respectively, which are superior to that of pristine GCN (0.0044 min−1) under visible-light irradiation. The enhanced transfer kinetics of photogenerated electrons and declined recombination of electron-hole pairs may account for the surpassing photocatalytic performance. Results obtained from electron paramagnetic resonance spectra and Mott-Schottky plots indicate that the formation of ･O2− via the reaction of O2 with electrons generated on the conduction band is the major reaction pathway to photodegrade formaldehyde under visible light. To further assess the real applications of prepared photocatalysts, the sFCC/GCN-0.15 and ESF/GCN-0.15 are used to fabricate the multifunctional coatings (denoted as s- and E-coatings) with sFCC and ESF as the main compositions. Experimentally, the E-coatings could reach the formaldehyde degradation efficiency of ca. 84.5% after 3 h of visible light irradiation and excellent humidity buffering ability (293.8 g m−2) which is at least 10-folds higher than commercial coatings (28.9 g m−2). This notable progress of humidity buffering capacity on E-coatings can be attributed to their surface textural properties. Most importantly, this study exemplifies the valorization of inorganic silica wastes to produce sustainable and multifunctional coatings which may offer the practical and cost-effective applications in the indoor living space.

Spent fluid catalytic cracking catalyst derived MCM-41 supported polyethylenimine for post-combustion CO2 capture

The buildup of solid waste as well as the global warming has become one of the major challenges. CO2 capture with solid amine synthesized from solid waste can not only address the issue of large CO2 emissions, but also achieve efficient utilization of solid waste. In this work, spent fluid catalytic cracking catalysts (sFCCc), a type of major wastes in petrochemical industries, are first utilized to synthesize polyethyleneimine (PEI) functionalized ordered mesoporous materials. The as-obtained MCM-41-PEI from sFCCc exhibits an acceptable equilibrium CO2 capacity (qe) of 2.7 mmol/g in simulated flue gases (10 % CO2/N2) at 65 °C, which is higher than one prepared with commercial silicon source. Moreover, the adsorbent displays excellent cyclic stability during 50 TSA cycles in the dry simulated flue gases, where the capacity decreases only by 4.9 %. Additionally, the breakthrough capacity (qb) is significantly improved from 0.6 mmol/g to 1.6 mmol/g under humid conditions (35 °C, 10 % CO2/N2). Interestingly, we discover that the optimal adsorption temperature of MCM-41-PEI with different PEI loadings shifted due to the distinct PEI distribution behavior within the pores. The Avrami model provides a reliable interpretation for the CO2 adsorption behavior of MCM-41-PEI at various test conditions. The synthetic strategy here provides a new route in the treatment of excessive sFCCc resources to achieve valuable adsorbents, which can be applied to dilute source CO2 capture processes.

Effect of spent fluid catalytic cracking (FCC) catalyst on syngas production from pyrolysis and CO2-assisted gasification of waste tires

With growing demands for improved energy recovery from waste tires, incorporating waste catalysts from different sectors can provide synergistic solution. This paper investigates the effect of using spent fluid catalytic cracking (FCC) catalyst on evolutionary behavior and yield of syngas (CO, H2, and light hydrocarbons), and char and energy yields during pyrolysis and CO2-assisted gasification of waste tires at 900 °C in a fixed-bed semi-batch reactor. The effect of catalyst position (in-situ and quasi-in-situ catalytic modes) and temperature was also examined during catalytic CO2-assited gasification for energy and chemicals production. The results reveal that the presence of spent FCC catalyst resulted in higher syngas and energy yields. The CO2-assisted gasification provided CO-rich syngas with higher yields than pyrolysis. The quasi-in-situ gasification provided increased syngas and energy yields by 24% and 23% respectively, as compared to in-situ catalytic gasification, which revealed that quasi-in-situ catalytic gasification to be more efficient and effective for increased syngas yields. Increasing temperature to 950 °C increased the yields syngas and energy owing to improved reforming and cracking reactions. This viability of utilizing spent FCC catalyst offers improved waste management economics for FCC plants while simultaneously improving the energy recovery from waste tires.

Possible use of spent FCC catalyst for upgrading of wax from the pyrolysis of plastics to liquid fuel

The cracking of heavy wax derived from mixed plastics (high-density polyethylene, low-density polyethylene, and polypropylene) to chemical and fuel purposes was explored using spent fluid catalytic cracking catalyst (spent FCC). The wax cracking was performed by a fixed-bed pyrolysis reactor with a slow heating rate. All catalysts, when compared to other catalysts (HY zeolite and MCM-41), could enhance liquid oil and gas production. While the spent FCC catalyst produced the highest liquid oil with least amount of coke production. The influence of spent FCC catalyst ratio on product distribution revealed that a catalyst-wax ratio of up to 1:1 resulted in a higher liquid oil yield than a low ratio. Additionally, the increase of cracking temperature promoted more oil production; however, at high temperature (above 400 °C) the evaporation of wax became more significant, and consequently a high portion of produced wax was obtained. Therefore, under suitable conditions, the spent FCC catalyst demonstrated the possibility of upgrading the heavy wax into liquid fuels and chemicals. In addition, this study also compared the products obtained from two processing routes using the spent FCC catalyst. The first route involved the pyrolysis of plastics into wax and then cracking the wax into liquid fuel, while the second route involved a one-step process that directly converted plastics into liquid fuel. The spent FCC catalyst promoted the production of diesel-range hydrocarbons and suppressed the aromatic production for the wax cracking. By contrast, the spent FCC catalyst significantly enhanced aromatic production during the cracking of mixed plastics.

Effect of process mode on product yields and selectivity in the catalytic co-pyrolysis of peanut shells and polypropylene using spent fluid catalytic cracking (FCC) catalyst

In this study, mixtures of peanut shells (B) and polypropylene (PP) were co-pyrolyzed in two configurations using spent fluid-catalytic-cracking (sFCC) catalyst. The feed ratio was varied to investigate changes in yields and selectivity. The ex-situ configuration generated a higher-quality liquid, less char and more gas yields (1.3 times on an average) than the in-situ mode. Both the operation modes produced similar aromatic compounds; however, the ex-situ bio-oil had a higher monoaromatic fraction. The ex-situ configuration showed more polycyclic aromatic hydrocarbons at higher B and PP loadings, with a maximum yield of ∼44%C at B: PP ratio of 1:2. The ex-situ mode cracked polypropylene more efficiently to short-chain olefins (<C10). The dominant fractions were C9 and C12 in the in-situ and C9 in the ex-situ mode. Co-pyrolysis improved the net hydrogen content of bio-oil. PP showed better aromatics selectivity than low density polyethylene (LDPE) due to the differences in their branched-chains.

Study on synergistic pyrolysis and kinetics of mixed plastics based on spent fluid-catalytic-cracking catalyst

At present, disposable plastic products such as plastic packaging are very common in our daily life. These products are extremely easy to cause serious damage to the soil and marine environment due to their short design and service life, difficulties in degradation, or long degradation cycles. Thermochemical method (pyrolysis or catalytic pyrolysis) is an efficient and environmentally friendly way to treat plastic waste. In order to further reduce the energy consumption of plastic pyrolysis and improve the recycling rate of spent fluid catalytic cracking (FCC) catalysts, we adopt the "waste-to-waste" approach to apply the spent FCC catalysts as catalysts in the catalytic pyrolysis of plastics, exploring the pyrolysis characteristics, kinetic parameters, and synergistic effects between different typical plastics (polypropylene, low-density polyethylene, polystyrene). The experimental results show that the spent FCC catalysts used in the catalytic pyrolysis of plastics are beneficial to reduce the overall pyrolysis temperature and activation energy, in which the maximum weight loss temperature decreases by about 12℃ and the activation energy decreases by about 13%. The activity of spent FCC catalysts is improved after modification by microwave and ultrasonic, which further improve the catalytic efficiency and reduce the energy consumption of pyrolysis. The co-pyrolysis of mixed plastics is dominated by positive synergistic effect, which is conducive to improving the thermal degradation rate and shortening the pyrolysis time. This study provides relevant theoretical support for the resource application of spent FCC catalysts and "waste-to-waste" treatment of plastic waste.

Study on kinetics of spent FCC catalyst applied to the living waste plastics

AbstractThe thermochemical method is one of the most potential ways to treat waste plastics. In order to reduce the energy consumption of pyrolysis, this study selected spent fluid catalytic cracking (FCC) catalyst as a catalyst for pyrolysis of waste plastics to explore the pyrolysis process of mixed waste plastics (polypropylene (PP)/polyethylene (PE)/polystyrene (PS)). The kinetic calculations show that there was a positive synergistic effect in the co‐pyrolysis of mixed plastics, which was beneficial to the reduction of activation energy. However, the participation of spent FCC catalysts can further reduce the pyrolysis temperature and activation energy of plastics, and increase the thermal degradation rate. Compared with non‐catalytic pyrolysis, the pyrolysis temperature corresponding to the maximum weight loss rate during catalytic pyrolysis was about 12 K earlier, the maximum degradation rate was about 41% higher, and the average activation energy decreased by about 22 kJ/mol. In order to further improve the catalytic efficiency of spent FCC catalysts, the spent FCC catalysts were modified by ball milling or ultrasonic method and then used for plastic pyrolysis. It was found that the modification effect of ball milling method was better than that of the ultrasonic method. Through thermodynamic analysis, it was found that the endothermic reaction occurred in the process of plastic pyrolysis and could not proceed spontaneously. The formed pyrolysis products reduced the disorder of a microscopic system. Combined with the experimental results of this paper, it can provide theoretical support for the catalytic pyrolysis of spent FCC catalysts for mixed waste plastics.

Synthesis of biofuel via catalytic fast pyrolysis of wood-plastic composite over low-cost catalysts

Thermogravimetric (TG) and pyrolyzer-gas chromatography/mass spectrometry (Py-GC/MS) analyses were performed to know the feasibility of low cost catalysts, γ-Al2O3, spent fluid catalytic cracking (FCC) catalyst, natural zeolite, to the pyrolysis of wood-plastic composite (WPC). Notably, the respective decomposition temperature of polyethylene and polypropylene in WPC was lowered with the use of low-cost catalysts during the catalytic fast pyrolysis (CFP). Furthermore, the lowest activation energy (Ea) of the CFP, obtained by the Ozawa method, was with the use of natural zeolite (127.5 kJ/mol), followed by the ones with the use of spent FCC catalyst (133.3 kJ/mol) and γ-Al2O3 (145.0 kJ/mol), respectively. In addition, the CFP over natural zeolite was less effective in terms of decreasing the production of low-quality hydrocarbons, paraffins and olefins having a wide carbon number distribution, and oxygenates compared to that over spent FCC catalyst and γ-Al2O3, respectively, due to the small pore size of natural zeolite. However, the largest amount of value-added aromatic hydrocarbons was produced in the CFP over natural zeolite among all the catalysts due to the high and strong acidity of natural zeolite.