Production and characterization of the biofuels obtained by thermal cracking and thermal catalytic cracking of vegetable oils

The thermal cracking and the thermal catalytic cracking of soybean oil were evaluated for the production of biofuels as an alternative to fossil fuels. The catalyst proposed for the cracking reaction was bauxite, a high-acidity and low-cost catalyst. The chromatographic profile of the biofuels obtained by cracking showed hydrocarbon compounds such as alkanes, alkenes and aromatics, as well as some oxygenated compounds such as carboxylic acids, ketones and alcohols. The products generated by the thermal catalytic cracking process showed better results than the thermal cracking products because of the low quantity of acids present. The catalyst used was thus shown to act in the secondary cracking process, in which the fatty acids decompose and generate hydrocarbons.     

Thermal degradation kinetics study and thermal cracking of waste cooking oil for biofuel production

Thermal cracking of waste cooking oil (WCO) for production of liquid fuel has gained special interest due to the growing demand of renewable fuel, depleting fossil fuel reserves and environmental issues. In the present work, thermal cracking of WCO to produce liquid hydrocarbon fuels without any preprocessing has been studied. Moreover, non-isothermal kinetics of WCO using thermogravimetric analysis (TGA) has been studied under an inert atmosphere at various heating rates. According to TGA result, active thermal decomposition of WCO was found to be between 318 and 500 °C. Furthermore, the temperature at which the maximum mass loss rate attained was shifted to higher values as the heating rates increased from 10 to 50 °C min^?1 and the values were found to be approximately similar to that of R ₅₀. Besides, model-free iso-conversion kinetic methods such as Friedman (FM), Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) were used to determine the activation energies of WCO degradation. The average activation energy for the thermal degradation of WCO was found to be 243.7, 211.23 and 222 kJ mol^?1 for FM, KAS and FWO kinetic methods, respectively. Additionally, the cracking of WCO was studied in a semi-batch reactor under an inert atmosphere and the influences of cracking temperature, time and heating rates on product distribution were investigated. From the reaction, an optimum yield of 72 mass% was obtained at a temperature of 475 °C, time of 180 min and a heating rate of 10 °C min^?1. The physicochemical properties studied were in accordance with ASTM standards.     

Determination of sulphur in liquids obtained by thermal cracking of waste polymers and commercial fuels with different analytical methods

Low sulphur concentration in hydrocarbon products as fuels or lubricants is an important requirement for the high quality standards of refineries. A non-polarised energy dispersive X-ray fluorescence spectroscopy (EDXRFS) and sample combustion technique (ASTM D6428-99) was compared. A new application of energy dispersive X-ray spectrometry as analytical method for the determination of sulphur in fuels and fuel-like fractions was investigated. Low sulphur containing fuels and hydrocarbon mixtures obtained by thermal cracking of waste polymers were measured and the influence of C/H ratio on accuracy was studied. The concentration of sulphur in samples was measured with calibration graphs of different hydrocarbon matrices (commercial gasoline, diesel oil and white oil were used). Good correlation was observed between the different methods, but the correlation was depending on the characteristics of the matrices. Detection limits of 1.0 ppm, 1.1 ppm and 0.9 ppm were obtained for S in gasoline, diesel oil and white oil, respectively.     

Comparison of thermal degradation products from real municipal waste plastic and model mixed plastics

The thermal degradation of real municipal waste plastic (MWP) obtained from Sapporo, Japan and model mixed plastics was carried out at 430 °C in atmospheric pressure by batch operation. The chlorinated hydrocarbons found in PE/PP/PS/PVC [poly(ethylene)/poly(propylene)/poly(styrene)/poly(vinyl chloride)] degradation liquid products were also observed in PE/PP/PS/PVC/PET (poly(ethylene terephalate)) and MWP degradation liquid products. The presence of PET in MWP produced the additional chlorinated hydrocarbons, which are similar to the chlorinated hydrocarbons observed during the PE/PP/PS/PVC/PET degradation liquid products. In addition, the presence of PET facilitated the formation of more organic chlorine content in liquid products and drastic decrease in the formation of inorganic chlorine content.     

CO2 adsorption of bagasse waste feedstock using thermogravimetric analyses

Journal of Thermal Analysis and Calorimetry - Nowadays, global warming is mainly caused by increase in CO2 concentration in the environment; to mitigate this problem, an attractive strategy for...     

Fuels obtained by thermal cracking of individual and mixed polymers

Utilization of oils/waxes obtained from thermal cracking of individual LDPE (low density polyethylene), HDPE (high density polyethylene), LLDPE (linear low density polyethylene), PP (polypropylene), or cracking of mixed polymers PP/LDPE (1: 1 mass ratio), HDPE/LDPE/PP (1: 1: 1 mass ratio), HDPE/LDPE/LLDPE/PP (1: 1: 1: 1 mass ratio) for the production of automotive gasolines and diesel fuels is overviewed. Thermal cracking was carried out in a batch reactor at 450°C in the presence of nitrogen. The principal process products, gaseous and liquid hydrocarbon fractions, are similar to the refinery cracking products. Liquid cracking products are unstable due to the olefins content and their chemical composition and their properties strongly depend on the feed composition. Naphtha and diesel fractions were hydrogenated over a Pd/C catalyst. Bromine numbers of hydrogenated fractions decreased to values from 0.02 g to 6.9 g of Br₂ per 100 g of the sample. Research octane numbers (RON) before the hydrogenation of naphtha fractions were in the range from 80.5 to 93.4. After the hydrogenation of naphtha fractions, RON decreased to values from 61.0 to 93.6. Diesel indexes (DI) for diesel fractions were in the range from 73.7 to 75.6. After the hydrogenation of diesel fractions, DI increased up to 104.9.     

催化裂解过程分子尺度的反应动力学模拟： 原料油分子尺度的模拟

以工业实测数据为基础,运用结构导向集总方法构造分子,对催化裂解原料油进行了分子尺度上的蒙特卡罗模拟.结果表明,Monte Carlo方法可以在分子尺度上实现对催化裂解原料很好的模拟.两种工况下原料的平均分子量、饱和烃、芳烃、胶质沥青、碳、氢、硫、氮含量等性质的计算值与实际值吻合,且由此产生的分子矩阵将为后续反应网络的建立打下基础.     

Kinetics of thermal cracking of light hydrocarbon mixture by pulsed microreactor

The kinetics of thermal cracking of a mixture of hydrocarbons (ethane, propane, isobutane and n-butane) was investigated in a packed-bed pulsed microreactor in the temperature range 600 – 725 °C. The reactor was made up of stainless steel (304) packed with quartz, and nitrogen was used as diluent. From experimental data it was found that all the saturated hydrocarbon, taken together as reactant in terms of total carbon, yielded first-order rates of disappearance to give products which were mainly methane, ethylene and propylene. The values of the Arrhenius factor and activation energy were found to be 4.779 × 10¹¹ s⁻¹ and 214.24 kJ/g mol, respectively. The kinetics of disappearance of individual hydrocarbons and formation of individual products were also investigated. Optimum temperature and residence time conditions for the formation of ethylene and propylene are reported. Surface effects of the packing were not detected when different sizes of packing were used.     

Catalytic stepwise pyrolysis of packaging plastic waste

In this paper the combination of catalytic and stepwise pyrolysis is explored. A mixture of polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET) and poly(vinyl chloride) (PVC), which resembles real municipal plastic waste, has been pyrolysed in a 3.5 dm³ semi-batch reactor at 440 °C for 30 min using a ZSM-5 zeolite as catalyst. A low temperature (300 °C) dechlorination step has been carried out both with and without catalyst. It has been proved that the application of such dechlorination step gives rise to a 75 wt% reduction of chlorine in the liquid fraction. However, such step has a negative influence on the catalyst, which loses some catalytic activity. The optimum procedure in terms of quality and chlorine content of the products is the combination of first a low temperature step without catalyst, and second the catalytic pyrolysis step.     

Effects of dissolution on plastic deformation and cracking of metals

The effects of surface dissolution on plastic deformation of metals, and the operating mechanisms, depend on many variables: stress; frequency of stress fluctuations; strain rate; temperature; metallographic constituents and their distribution; surface films; adsorbed species; surface energy; electrochemical potential and current; dissolution morphology; crack tip geometry; dislocation mobility; and the chemistry at the crack tip in the environment as well as in the metal. The manifestation of these variables in different relative proportions in different systems causes a variety of metal/environment interactions, the most extreme of which are stress-corrosion cracking and corrosion fatigue. During simultaneous action of stress and dissolution, stress-corrosion cracking occurs only with specific metal/environment combinations within critical electrochemical-potential ranges, whereas corrosion fatigue develops at dissolution rates greater than a critical value. In addition to these forms of degradation, the dissolution process may inject defects — such as vacancies, divacancies, or dislocations — into the metal lattice, with resulting alteration in dislocation behaviour and plastic-deformation characteristics. Dissolution may also influence the films that normally exist on metal surfaces and, consequently, the dislocation arrangements which depend on these films. This review is a systematic presentation and discussion of those critical — and sometimes controversial — experiments that elucidate the effects at an atomic level of surface dissolution on plastic deformation of metals.     

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%.     

Comparative study on thermal cracking of Athabasca bitumen

In this study, three commonly used isoconversional methods, namely: Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and the advanced non-linear integral method of Vyazovkin (NLN) were employed for the first time for calculating the activation energy for thermal cracking of Athabasca bitumen under inert conditions. Thermal cracking of Athabasca bitumen was carried out at nonisothermal conditions at different heating rates under nitrogen atmosphere using thermogravimetic analyzer (TG). One isothermal TG experiment was conducted for model prediction. Differences in the values of activation energy determined from the three methods selected have been demonstrated. These differences were mainly attributed to the approximations used for the temperature integral employed in the integral methods. Nonetheless, all the methods tested in this study provided satisfactory isothermal predictions. The study showed that, among the three methods tested, the NLN method provided more accurate results. This is because NLN is approximation free and uses small time segments for the temperature integral.     

Kinetics of thermal cracking of a hydrocarbon mixture by an empty pulsed microreactor

The kinetics of thermal cracking of a mixture of hydrocarbons (ethane, propane, isobutane and n-butane) was investigated in an empty pulsed microreactor in the temperature range 600 – 710 °C. The results were compared with those obtained in earlier work with a quartz packed pulsed microreactor. While the kinetic parameters agreed well, better yields of ethylene and propylene were found with the empty pulsed microreactor     

Solid waste decontamination by thermal desorption and catalytic oxidation methods

Combined thermal desorption and catalytic oxidation for soil decontamination was studied at the pilot plant scale. Gasoline, xylene, and 2-methylnaphthalene were used as model contaminants in the concentrations from 2 g to 10 g per kg of soil. To guarantee the flow of the exhaust gas from the thermal desorption unit into the catalytic oxidation unit, a Venturi pump was used. Based on the laboratory scale catalytic tests, the commercial catalyst EnviCat® VOC-1544 was employed in the catalytic oxidation. Residual concentrations of hydrocarbons in soil after the thermal desorption were below the detection limits of the applied analytical method (GC-MS). Although the contaminant concentrations at the inlet of the catalytic reactor significantly varied during the experiments, the efficiency of catalytic oxidation was higher than 90 % in all cases.     

Modeling of catalytic coke formation in thermal cracking reactors

At the start-up period, the most important mechanism in the coke production with a clean reactor surface is the catalytic mechanism. The study of this mechanism can be very useful for the better comprehension of the coke production process. In this paper, a model was designed for such a production through the utilization of a catalytic mechanism and a kinetic model, capable of interpreting the catalytic coke production on the reactor surface. For the determination of the model reliability, the experimental data related to the naphtha feed, existing in literature, were used. In addition, the constant parameters of the model, the velocity and the activation energy constants, associated to the kinetic model, were calculated. The results of the developed model were in satisfactory agreement with the experimental data. Eventually, the catalytic coke amount in comparison with the total coke production on the reactor surface and its significance were under investigation.     

Watergas from plastic waste and its possible uses

Coal gasification technology should also be applicable to plastic waste. The resulting product is watergas or in general terms syngas which is used as a feedstock for several large chemical products. Based on theoretical considerations the study evaluates the costs related to syngas production from plastic waste and subsequent conversion to chemical raw products. Net waste disposal costs of 275 – 690 DM/ton are calculated depending upon the end product(s).     

Experimental study and kinetic modeling of kerosene thermal cracking

Thermal cracking of kerosene for producing ethylene and propylene has been studied in an experimental setup. A set of experiments were designed using Response Surface Design (Box Behnken) method. In these experiments, the coil outlet temperature (COT), residence time and steam ratio varied from 795 °C, 0.13 s and 0.6 to 838 °C, 0.27 s and 1.0, respectively. Obtained maximum ethylene and propylene yield in these experiments were 32 and 16.9 wt.%, respectively. In next step of studies, we tried to develop an applicable kinetic model to predict yield distribution of products of the kerosene thermal cracking. Therefore, a reaction mechanism is generated on the basis of major reactions classes in the pyrolysis and feed compounds using some simplification assumptions in the model. This semi-mechanistic kinetic model contains 172 reactions, 22 molecular and 29 radical species. A sensitivity analysis was done on kinetic model and controlling reactions identified. An objective function was defined and used to tune the model with experimental data. Finally, the calculated model results were compared with the experimental data. Scatter diagrams showed good agreement between model and experimental data.     

Advances and approaches for chemical recycling of plastic waste

The global production and consumption of plastics has increased at an alarming rate over the last few decades. The accumulation of pervasive and persistent waste plastic has concomitantly increased in landfills and the environment. The societal, ecological, and economic problems of plastic waste/pollution demand immediate and decisive action. In 2015, only 9% of plastic waste was successfully recycled in the United States. The major current recycling processes focus on the mechanical recycling of plastic waste; however, even this process is limited by the sorting/pretreatment of plastic waste and degradation of plastics during the process. An alternative to mechanical processes is chemical recycling of plastic waste. Efficient chemical recycling would allow for the production of feedstocks for various uses including fuels and chemical feedstocks to replace petrochemicals. This review focuses on the most recent advances for the chemical recycling of three major polymers found in plastic waste: PET, PE, and PP. Commercial processes for recycling hydrolysable polymers like polyesters or polyamides, polyolefins, or mixed waste streams are also discussed.