Thermal and catalytic degradation of pyrolytic oil from pyrolysis of municipal plastic wastes

Thermal and catalytic degradation of pyrolytic oil obtained from the commercial rotary kiln pyrolysis plant for municipal plastic waste was studied by using fluid catalytic cracking (FCC) catalyst in a bench scale reactor. The characteristics of raw pyrolytic oil and also thermal and catalytic degradation of pyrolytic oil using FCC catalyst (fresh and spent FCC catalyst) under rising temperature programming was examined. The experiments were conducted by temperature programming with 10 °C/min of heating rate up to 420 °C and then holding time of 5 h. During this programming, the sampling of product oil was conducted at a different degradation temperature and also different holding time. The raw pyrolytic oil showed a wide retention time distribution in GC analysis, from 5 of carbon number to about 25, and also different product characteristics with a comparison of those of commercial oils (gasoline, kerosene and diesel). In thermal degradation, the characteristics of product oils obtained were influenced by reaction temperature under temperature programming and holding time in the reactor at 420 °C. The addition of FCC catalyst in degradation process showed the improvement of liquid and gas yield, and also high fraction of heavy hydrocarbons in oil product due to more cracking of residue. Moreover, the characteristic of oil product in catalytic degradation using both spent and fresh FCC catalysts were similar, but a relatively good effect of spent FCC catalyst was observed.     

Research on Hazardous Waste Removal Management: Identification of the Hazardous Characteristics of Fluid Catalytic Cracking Spent Catalysts

Fluid catalytic cracking (FCC) spent catalysts are the most common catalysts produced by the petroleum refining industry in China. The National Hazardous Waste List (2016 edition) lists FCC spent catalysts as hazardous waste, but this listing is very controversial in the petroleum refining industry. This study collects samples of waste catalysts from seven domestic catalytic cracking units without antimony-based passivation agents and identifies their hazardous characteristics. FCC spent catalysts do not have the characteristics of flammability, corrosiveness, reactivity, or infectivity. Based on our analysis of the components and production process of the FCC spent catalysts, we focused on the hazardous characteristic of toxicity. Our results show that the leaching toxicity of the heavy metal pollutants nickel, copper, lead, and zinc in the FCC spent catalyst samples did not exceed the hazardous waste identification standards. Assuming that the standards for antimony and vanadium leachate are 100 times higher than that of the surface water and groundwater environmental quality standards, the leaching concentration of antimony and vanadium in the FCC spent catalyst of the G set of installations exceeds the standard, which may affect the environmental quality of surface water or groundwater. The quantities of toxic substances in all spent FCC catalysts, except those from G2, does not exceed the standard. The acute toxicity of FCC spent catalysts in all installations does not exceed the standard. Therefore, we exclude “waste catalysts from catalytic cracking units without antimony-based passivating agent passivation nickel agent” from the “National Hazardous Waste List.”     

Thermal degradation of polyethylene and polystyrene from the packaging industry over different catalysts into fuel-like feed stocks

Thermal degradation of waste polymers was carried out as a suitable technique for converting plastic polymers into liquid hydrocarbons, which could be used as feed stock materials. The catalytic degradation of waste plastics (polyethylene and polystyrene) was investigated in a batch reactor over different catalysts (FCC, ZSM-5 and clinoptillolite). The effects of catalysts and their average grain size on the properties of main degradation products (gases, gasoline, diesel oil) are discussed. The temperature range of 410-450 °C was used in the process. Both equilibrium FCC catalyst and natural clinoptilolite zeolite catalyst had good catalytic activity to produce light hydrocarbon liquids, and ZSM-5 catalyst produced the highest amount of gaseous products. Gases and liquids formed in cracking reactions were analyzed by gas chromatography. The liquid products consisted of a wide spectrum of hydrocarbons distributed within the C₅-C₂₈ carbon number range depending on the cracking parameters. The composition of hydrocarbons had linear non-branched structure in case of polyethylene, while from polystyrene more aromatics (ethyl-benzene, styrene, toluene, and benzene) were produced. The yields of volatile products increased with increasing degradation temperature. The olefin content of liquids was measured with an infrared technique and an olefin concentration of 50-60% was observed. The concentration of unsaturated compounds increased with decreasing temperature, and in the presence of catalysts. The activation energies were calculated on the basis of the composition of volatile products. The apparent activation energies were decreased by catalysts and catalyst caused both carbon-chain and double bond isomerisation.     

Ni-Mg复合催化剂催化裂解CH_4制氢动力学研究

基于定温热重实验,建立了甲烷催化裂解反应动力学模型和催化剂表面积炭失活动力学模型。其中,甲烷催化裂解动力学模型将初始产氢速率视为催化剂未积炭条件下的动力学基础数据;催化剂表面积炭失活动力学则基于甲烷催化裂解速率的降低。实验使用Ni-Mg复合催化剂,分别在535、585、635℃,甲烷分压10~4、2×10~4、3×10~4Pa条件下展开甲烷催化裂解动力学特性研究。结果表明,甲烷催化裂解的反应级数为0.5,活化能为82 k J/mol;Ni-Mg复合催化剂反应失活级数为0.5,催化剂失活活化能为118 k J/mol。实验条件下均制得了多壁碳纳米管。     

Chemical catalysed recycling of polypropylene over a spent FCC catalyst and various commercial cracking catalysts using TGA

Thermogravimetric analysis (TGA) has been used as a tool to characterise the activity, regenerability and deactivation behaviour of spent FCC commercial catalyst (FCC-s1) in the degradation of polypropylene. The FCC-s1 catalysts and amorphous silica–alumina (SAHA) significantly reduced the activation energy as compared with thermal process, and zeolites (ZSM-5 and HUSY) further reduced the activation energy. However, silicalite catalysts gave very minimal effect on PP degradation at a temperature similar to that of thermal cracking. Analysis of the TGA results allowed a relationship between catalyst activity and coke content to be derived. The activity of FCC-s1 catalysts was found to fall exponentially with coke content, and it could be recover most its initial value. The results represent an interesting alternative to have significant impact on the economics of a catalytic polymer degradation process employing post-use FCC commercial catalysts of zero market value.     

Determination of kinetic parameters and analytical pyrolysis of tobacco waste and sorghum bagasse

The thermal decomposition of tobacco waste and sorghum bagasse was investigated by non-isothermal thermogravimetric analyses, applying slow heating rates and well-defined conditions. The purpose of evaluating the decomposition was to estimate the kinetic parameters of the analyzed materials. Activation energies and Arrhenius exponential factors were inferred by different estimation methods: the classical methods of Ozawa and Starink and the independent parallel reactions model. The analytical pyrolysis was performed in a micro-pyrolyzer coupled to a gas chromatographer/mass spectrometer. Values of activation energy obtained with single step reaction models by the Ozawa method were: 103.94 kJ/mol for tobacco waste and 120.01 kJ/mol for sorghum bagasse, and by the Starink method - 135.95 kJ/mol for tobacco waste and 148.91 kJ/mol for sorghum bagasse. The independent parallel reaction model presented energy activation values of 39.7-272.0 kJ/mol for tobacco waste and 35.7-220.0 kJ/mol for sorghum bagasse. In analytical slow and fast pyrolysis of tobacco residue and sorghum bagasse, holocellulose and lignin-derived compounds were identified, as well as hydrocarbons and aromatic hydrocarbons. The kinetic behavior of the materials are presented and discussed. Our findings may be helpful in evaluating other types of lignocellulosic biomass.     

Catalytic gasification of Pakistani Lakhra and Thar lignite chars in steam gasification

采用热重法在常压与700℃~900℃条件下的水蒸气气化过程,对两种巴基斯坦Lakhra和Thar褐煤半焦进行了单一和混合催化剂(即3%钙和5%钠-黑液单一催化剂及一种3%钙和5%钠-黑液混合催化剂)对碳转化率、气化反应速率常数及活化能、有害污染含硫气体相对量的催化效应研究.两者Lakhra和Thar褐煤半焦经直接气化就可获得高的碳转化率,但采用纸浆黑液催化剂可使气化速率变得很快.含灰高的Thar褐煤半焦在纸浆黑液催化气化过程更易生成一些复杂的硅酸盐,从而导致比含灰低的Lakhra褐煤半焦出现一个更低的转化率.在水蒸气气化过程由半焦和纸浆黑液自身所产生的SO2 和 H2S含硫气体可为存在于纸浆黑液中的Ca盐所捕获而完成脱硫过程,但这一过程在低于900℃时更有效.缩芯模型 (SCM)可较好地用来关联转化率与时间的关系并给出不同温度下的反应速率常数k.基于阿累尼乌斯方程预测了反应活化能Ea 和指前因子A.在纸浆黑液和钙混合催化及纸浆黑液催化剂时,Lakhra褐煤半焦的Ea分别为44.7kJ/mol和 59.6kJ/mol明显小于Thar褐煤半焦的Ea=114.6kJ/mol 和 Ea=100.8kJ/mol,同样也小于无催化剂纯半焦气化时Lakhra褐煤半焦的Ea=161.2kJ/mol和Thar半焦的Ea=124.8kJ/mol.     

Catalytic cracking of polyethylene waste in horizontal tube reactor

In this study catalytic and thermal cracking of polyethylene waste were investigated in continued tube reactor system. HZSM-5 and equilibrium FCC type catalysts were tested. Both the resistance to deactivation and the regeneration process of the catalyst were studied. Reaction temperature of 545 °C and residence time of 20 min were used during the cracking treatment. The reaction products were analyzed and the textural properties of catalysts were also determined. It was found that after the first reaction run the FCC catalyst lost 75% of its cracking activity, in case of HZSM-5 the rate of deactivation was higher. The cracking activity of catalyst could be improved by regeneration process with only 2-3% compared to the coked catalyst. The isomerisation effect of the catalysts was also observed. The effect of coked FCC catalyst could be improved by the regeneration process with 50% in case of HZSM-5 it was only 25%.     

不同活性炭负载的镍基催化剂上废塑料裂解制碳纳米管性能

以椰壳炭、竹炭和木炭三种活性炭为载体,采用浸渍法制备炭负载金属镍的催化剂,考察其在废塑料裂解制备碳纳米管过程中的催化反应性能;采用X射线衍射、扫描电镜、透射电镜、拉曼光谱仪、同步热分析仪、比表面积分析仪等手段分析了催化剂和产物碳纳米管的形貌和结构。结果表明,椰壳活性炭为载体制备的镍基催化剂上碳纳米管产量最高、石墨化程度最好。以椰壳活性炭为载体制备的镍基催化剂为例,研究了反应温度和镍负载量对其催化性能的影响。     

Production of valuable hydrocarbons by catalytic degradation of a mixture of post-consumer plastic waste in a fluidized-bed reactor

A mixture of post-consumer plastic waste (PE/PP/PS/PVC) was pyrolyzed over various catalysts using a fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic and mechanistic schemes for the observed products associated with chemical reactions and catalyst deactivation has been developed. The model gives a good representation of experimental results. It is also an improvement on the currently available empirical “lumping” techniques which are usually severely restricted in terms of product definitions. Additionally, this model represents the benefits of product selectivity for the chemical composition in relation to the effect of structurally different catalyst types, and the performance of the reaction temperature used as well as the particle size of the catalyst selected.     

Temperature-programmed oxidation of equilibrium fluid catalytic cracking catalysts

Characterization of coke on equilibrium, fluid catalytic cracking (FCC) catalysts contaminated with metals was investigated using temperature-programmed oxidation (TPO). TPO spectra of spent equilibrium catalysts from cracking of sour imported heavy gas oil (SIHGO) were deconvoluted into four peaks (Peak K, L, M and N). The four peaks were assigned to different types of coke on the catalyst. Peak L in the TPO spectrum was assigned to the 'contaminant' coke in the vicinity of metals. The amount of contaminant coke (Peak L) correlates with metal-contaminant concentration. The size of Peak L which is related to amount of contaminant coke decreased significantly for the spent highly contaminated catalyst pretreated with hydrogen and methane prior to cracking reactions as compared to the non-pretreated catalysts. Since both hydrogen and methane pretreatment can reduce oxidation state of the vanadium that present at high concentrations on the equilibrium catalysts the decrease in the amount of contaminant-coke represented by Peak L was explained by the reduction of the oxidation state of vanadium. Less contaminant coke was produced after the equilibrium catalysts were pretreated using hydrogen and methane gases since reduced vanadium has lower dehydrogenation activity compared to oxidized vanadium. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chemical Upcycling of Waste Plastics to High Value-Added Products via Pyrolysis: Current Trends,Future Perspectives,and Techno-Feasibility Analysis

Chemical upcycling of waste plastics into high-value-added products is one of the most effective, cost-efficient, and environmentally beneficial solutions. Many studies have been published over the past few years on the topic of recycling plastics into usable materials through a process called catalytic pyrolysis. There is a significant research gap that must be bridged in order to use catalytic pyrolysis of waste plastics to produce high-value products. This review focuses on the enhanced catalytic pyrolysis of waste plastics to produce jet fuel, diesel oil, lubricants, aromatic compounds, syngas, and other gases. Moreover, the reaction mechanism, a brief and critical comparison of different catalytic pyrolysis studies, as well as the techno-feasibility analysis of waste plastic pyrolysis and the proposed catalytic plastic pyrolysis setup for commercialization is also covered.     

Characterization of vacuum gas oil-low density polyethylene blends by thermogravimetric analysis

The study of the catalytic pyrolysis of mixtures of fuel and polymers is interesting in order to explore the possibility of using commercial fluid catalytic cracking (FCC) units or similar processes for recycling plastic wastes. In this work, different samples of vacuum gas oil (VGO), polyethylene (PE) and vacuum gas oil-polyethylene blends (VGO-PE) have been studied by thermogravimetric analysis. Vacuum gas oil-polyethylene blends with 1, 2.5, 5, 7.5 and 10% w/w of PE were prepared by continuously stirring for 120 min, at 60 rpm at 120 °C, and afterwards, the effect of different catalysts (HZSM-5, HUSY, HBeta zeolites, FCC catalysts and Al-MCM-41) on the decomposition of these mixtures was studied. Moreover, the deposition of coke over each catalyst was studied by thermogravimetric analysis in an oxidant atmosphere. The catalytic pyrolysis behaviour of the VGO-PE mixtures indicates a two-step process, the degradation of the VGO and the PE fraction being almost independent. The degradation or evaporation of the VGO fraction is only slightly affected by the presence of the catalyst, whereas the PE fraction showed similar behaviour as that already described in the literature for the pure polymer. The results show that the HBeta zeolite is the most active catalyst for the decomposition of the mixtures, and that the ZSM-5 zeolite is the catalyst with the lowest amount of coke formation. These results are in very good agreement with the structural characteristics of the different catalysts studied, i.e., with their pore size and acidity.     

三种工业废料对石油焦CO2气化动力学的影响

以造纸黑液、煤渣、污泥为催化剂,用加压热天平考察了石油焦与CO2催化与非催化气化动力学特性。结果表明,非催化气化时,反应速率随着转化率的增大先增大后减小,呈单峰曲线;催化气化时,反应速率随着转化率的增大而减小,不存在峰值。给出的正态分布函数模型很好地描述了石油焦CO2的非催化与催化气化动力学。计算得到石油焦与CO2非催化气化的活化能为197.7 kJ/mol。三种催化剂活性的差异与其所含金属元素的质量分数密切相关,其中富含Na元素的造纸黑液活性最好,反应速率是非催化气化的6倍。     

程序升温连续流动反应器技术及其应用

在运用连续流动反应(CFR)技术(尾气技术)的基础上提出了1种可筛选催化剂并能进行非均相催化动力学研究的实验原理和方法--程序升温连续流动反应器(TPCFR)技术。在用此法筛选过的Cu-Ni催化剂上对甲醇分解反应和甲醇水蒸汽重整反应进行了系统研究,证明这种方法合理、可信。利用1条TPCFR曲线可求出各个动力学参数。     

柳树河油页岩微波干燥及其对热解特性的影响

在对家用微波炉改造基础上搭建了微波干燥实验台,研究了柳树河油页岩微波干燥特性及对热解特性的影响。结果表明,微波干燥所需的时间为传统干燥所需时间的20%;微波干燥速率要明显大于传统干燥速率;Page模型适用于描写柳树河油页岩微波干燥过程。微波干燥的油页岩同热风干燥后及原样油页岩的热解活化能随转化率的变化曲线基本一致,整体呈先上升后下降的趋势,在转化率为0.7时达到最大值;热解活化能在80~200 kJ/mol变动;微波干燥油页岩热解反应有机质分解段的活化能增加。     

程序升温表面炭气化反应动力学研究

本文用程序升温表面反应(TPSR)方法,研究了甲烷裂解沉积在不同催化剂上的炭与水蒸汽反应的动力学。结果表明,炭与水蒸汽反应属一级反应,活化能在212.0—256.7KJ/mol之间。该法简便、迅速。所获得的动力学参数对研究在不同催化剂上的炭与水蒸汽反应性能差异具有实际意义。     

Fast pyrolysis of waste pepper stem over waste FCC catalyst

Fast pyrolysis of waste pepper stem was investigated using waste FCC catalyst and HY zeolite with a SiO₂/Al₂O₃ ratio of 5.1. The pyrolysis oil obtained from the pyrolysis at 500 °C was analyzed using GC/MS. Oxygenates were converted, in particular when the catalyst dose was high, to furans and aromatics. The contents of low-molecular-mass phenolics and aromatics increased with increasing quantity of acid sites deployed. On the other hand, the content of high-molecular-mass phenolics was increased by catalysis with the biomass:catalyst ratio of 1:1, whereas it was decreased by catalysis with the biomass:catalyst ratio of 1:10. This was explained by the pathway of lignin-to-aromatics conversion: lignin → high-molecular-mass phenolics → low-molecular-mass phenolics → aromatics. Activated waste FCC catalyst showed a little weaker catalytic activity for the conversion of low-molecular-mass phenolics to aromatics than HY, leading to a higher phenolics content and a lower aromatics content. The results of this study indicate that the catalytic pyrolysis of lignin-rich biomass over waste FCC catalyst can be a promising way of recycling waste FCC catalyst for the production of high-value-added chemicals, such as furans, phenolics and aromatics.     

The application of Py-GC/MS for the catalytic upgrading of oil separated from summer food waste leachate

The catalytic cracking of oil fractions separated from summer food waste leachate was investigated over BEA zeolite and Al-SBA-15 catalysts. In this study, a mixture of food waste oil fractions and catalyst was directly introduced to pyrolysis gas chromatography/mass spectrometry (Py-GC/MS), with the resulting vapor phase products being simultaneously analyzed. Various acid compounds, including oleic acid, produced by the non-catalytic pyrolysis of food waste leachate were reformed into valuable compounds, such as oxygenates, hydrocarbons, and aromatics. The BEA zeolite catalyst showed higher selectivity for hydrocarbon compounds, especially aromatics, within the gasoline range due to its superior cracking ability originating from its highly acidic sites. Conversely, the cracking performance of the Al-SBA-15 catalyst, possessing mild acidic sites, was lower than that of the BEA zeolite. Increasing the amount of Al-SBA-15 catalyst enhanced the cracking activity and resulted in higher selectivity for hydrocarbons.     

Bibliometric analysis and an overview of the application of the non-precious materials for pyrolysis reaction of plastic waste

Huge plastic consumption and depletion of fossil fuels are at the top of the world's environmental and energy challenges. The scientific community has tackled these issues through different approaches. Catalytic pyrolysis of plastic wastes to valuable products has been proved as a sustainable route which fits with the circular economy aspects. The design of catalytic materials is the central factor for performing the catalytic conversion of plastic wastes. This review aims to conduct a Bibliometric analysis of the pyrolysis of plastic wastes and non-precious-based catalysts by mapping research studies over the last fifty years. The analysis was developed via VOSviewer and RStudio tools. It showed the historical progress regarding plastic waste pyrolysis to produce valuable products and chemicals worldwide. The research shows that the top five countries with the highest citations and publications in this field were Spain, China, England, the USA and India. The Journal of Analytical and Applied Pyrolysis had the most comprehensive coverage of plastic waste. The relationship between the catalyst and the mechanism of plastic waste can influence the production yield and selectivity. The research gap and underrepresented research topics were identified, and previous research studies on developing non-precious-based catalysts that were most relevant to the current topic were reviewed and discussed. The challenges and perspectives on catalyst preparation and development for material complexity were critically discussed. Challenges of previous studies and directions for future research were provided. This report might guide the reader to take a general look at plastic waste valorization by pyrolysis and easily understand the main challenges.