Thermo-catalytic Pyrolysis Research Articles

Thermocatalytic pyrolysis of CO molecules. Structure and sorption characteristics of the carbon nanomaterial

A carbon nanocondensate containing multiwalled carbon nanotubes has been produced by dissociation of CO molecules on an iron-nickel catalyst at temperatures of 400–500 °C. X-ray diffraction is used to show that this condensate contains two phases with different densities and degrees of ordering. Elevated synthesis temperatures lead to a higher density and smaller differences in the phases, which are related to increased freedom from defects in the carbon layers and a greater number of layers in the multiwalled carbon nanotubes. Studies of the sorption and subsequent desorption kinetics of hydrogen by the synthesized samples at temperatures of 7–120 K showed that when the temperature is lowered from 120 to 65 K, an increased sorption time for H2, which is typical of thermally activated diffusion, was observed in all the samples. At temperatures below 65 K the characteristic hydrogen sorption times depended weakly on temperature; this can be explained by a predominance of tunnel diffusion over thermally activated diffusion. At temperatures of 7–20 K, the temperature dependence of the characteristic times had features that appear to be related to the formation of a monolayer of H2 molecules on the inner surface of the nanotube cavities. The dependence of the hydrogen diffusion activation energy on the temperature at which the samples were synthesized correlates well with x-ray spectroscopy data: n rise in the activation energy is observed as the relative amount of the highly ordered carbon phase increases.

Stability and storage properties of hydrocarbons obtained by pilot scale pyrolysis of real waste HDPE-PVC in tubular reactor

In this work the mixtures of real waste high-density polyethylene, low-density polyethylene, polypropylene and polyvinyl-chloride (PVC) were pyrolyzed in a pilot scale horizontal tubular reactor using different synthetic zeolite catalysts. Raw material was fed into the reactor through an electrically heated screw feeder, and then decomposed in the reactor. Products were separated into gases, pyrolysis oil and heavy fraction by atmospheric distillation. The yields of gases and pyrolysis oils can be significantly increased by using catalysts, but the catalyst properties were key parameter. For instance, Ni/ZSM-5 catalyst can increase the hydrogen content in gases and isomerize the carbon framework of hydrocarbons. Pyrolysis oils contained C5-C35 hydrocarbons; however their properties were modified by catalysts. An accelerated aging test was performed to follow the long term behavior of products. Pyrolysis oils were treated at 80 °C for 7 d, and then the stability of pyrolysis oils was assessed by evaluating the density, solid deposition and acid number. Unsaturated hydrocarbons in pyrolysis oils can agglomerate during the aging. On the other hand the catalysts can improve their properties. Pyrolysis oils obtained by thermo-catalytic pyrolysis resulted with less corrosion than in case of without catalysts.

Preparation and application of metal loaded ZSM-5 and y-zeolite catalysts for thermo-catalytic pyrolysis of real end of life vehicle plastics waste

In this work synthetic zeolite catalysts were modified by metal loading and used for real end of life vehicle plastic waste pyrolysis. ZSM-5 and y-zeolite catalysts were loaded by Ce2+, Cu2+, Fe2+, Fe3+, H+, Mg2+, Ni2+, Sn2+ and Zn2+ and the catalytic effects of both parent and metal loaded catalysts were tested by thermogravimetric method. The catalysts morphology and other properties were followed by N2 adsorption/desorption isotherms, Fourier transformed infrared spectroscopy, Scanning Electron Microscopy and energy dispersive x-ray fluorescent spectroscopy. Significant difference in micropore, mesopore and macropore surface area, and average pore diameter was concluded. In general, the surface areas could be decreased by metal loading onto the catalyst surface. Parent y-zeolite had larger surface areas than that of parent ZSM-5 catalyst. Based on EDXRFS analysis, catalysts were loaded by 8–10% metals. Regarding grain size, in general y-zeolite based catalysts had smaller grains and the distribution was also narrower, than ZSM-5 based catalysts. The Si/Al ratio was 17.11–21.75 in case of ZSM-5 catalysts and 2.04–2.91 regarding y-zeolite catalyst. Based on first order kinetic approach, the reaction kinetic parameters were also calculated and evaluated. Waste end-of life vehicle (ELV) started to decompose at 426 °C (T5%) and finished at 525 °C (T95%). Catalysts can decrease the activation energies of decomposition. Same order of the activation energy decreasing of both ZSM-5 and y-zeolite based catalysts was found: Cu<Ce<Mg<Ni<Fe(III)<Fe(II)<Zn<Sn, however, y-zeolite based catalysts had advanced properties in activation energy decreasing than ZSM-5 based.

Thermo-catalytic two-step pyrolysis of real waste plastics from end of life vehicle

This work focuses to the thermo-catalytic pyrolysis of real plastic waste from End of Life Vehicle. Two-step batch reactor fitted with electric heating was used for pyrolysis. Zeolite catalysts (ZSM-5, β-zeolite and y-zeolite) was used in the first reactor at 425°C and 485°C, while the product yield and composition were further modified by the using of structured Ni/Mo–Al2O3 catalyst in the 2nd reactor at 380°C. No water/steam was feed into the 2nd reactor. Gas-chromatography, high-pressure liquid chromatography, size exclusion chromatography and Fourier transformed infrared spectroscopy were used for identification of pyrolysis products, while the catalyst morphology was investigated by scanning electron microscopy. Catalysts in the 1st reactor had a significant effect to the product yields and decreased the time required for pyrolysis. ZSM-5 and y-zeolite catalysts had high activity in carbon frame isomerization. β-zeolite catalyst could crack the polymer main chain with high efficiency; however, its deactivation was the fastest. Structured Ni/Mo-Al2O3 in the 2nd reactor affected the gas/pyrolysis oil ratio, increased the hydrogen yield in gases, monoaromatic yield in pyrolysis oil and owing to the coke formation, its surface was fully covered by coke depositions after the pyrolysis. The hydrocarbon compositions of pyrolysis oils were favourable for further separation and refinery application.

Recycling of elv waste plastics by one-stage and a two-stage thermo-catalytic pyrolysis

Due to the significant increasing in motorization, the long term sustainable utilization of End-of-Life Vehicles (ELV) wastes is in the focus of the waste management. In the European Union annually 8-9 Mt of ELV waste should be utilized. ELV contains mainly metals but its 15 - 20 % is plastics or rubber. According to the 2000/53/EC directive, from 1 January 2015, 95 % of the waste from vehicles have to be utilized; 85 % of the wastes by mechanical recycling and 10 % of the wastes by chemical recycling. The chemical recycling results valuable products from ELV plastic wastes, such as fuels, oil and hydrocarbon gases, which can be utilized as a feedstock for energy generation, for petrochemical processes or even in oil refinery. Mixture of real ELV waste plastic was pyrolyzed in a one-stage and a two-stage reactor in the presence of zeolite catalysts at 425 °C in the first reactor. Different modified ZSM-5 catalysts were synthesized by wet impregnation and tested in the first reactor: H/ZSM-5, Fe(III)/ZSM-5, Ni/ZSM-5 and Cu/ZSM-5. In case of two- stage pyrolysis, Ni/Mo-Al2O3 was used in the second reactor. Due to avoid the formation of harmful by- products, the pyrolysis was taken under inert nitrogen atmosphere. The composition of gases was analysed by GC. Higher yield of gaseous products was measured using catalyst in the second reactor; furthermore the hydrogen yield was also higher. Pyrolysis oil was measured by GC, HPLC or even FTIR. Regarding pyrolysis oils, they contain non-branched, branched aliphatic hydrocarbons and aromatics compounds; and significant isomerization was concluded over catalysts.

Thermo-catalytic pyrolysis of biomass and plastic mixtures using HZSM-5

The catalytic effect of HZSM-5 zeolite was studied on the thermal decomposition of model waste mixtures of plastics (composed of PE, PP, and PET) and biomass (composed of newspaper, cardboard, and pine sawdust). The influence of temperature and catalyst ratio as well as the hindering effect of cellulose and lignin on the catalytic decomposition of plastic waste were studied applying analytical pyrolysis at low and high heating rate by thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), respectively. The products of laboratory scale batch pyrolysis and thermo-catalytic pyrolysis were analyzed in details and compared. HZSM-5 catalyst reduced the thermal stability of plastic waste, but the catalytic effect was blocked when 50% cellulose or 10% lignin were mixed in the plastic waste. Principal component analysis (PCA) has been applied to reveal correlations between the composition of pyrolysis products, pyrolysis temperature and proportion of the applied catalyst. It was established that the hindering effect of biomass could be compensated by applying higher catalyst ratio. In a batch reactor, the use of HZSM-5 catalyst led to a significant increase in the yields of volatiles (both gases and pyrolysis oil); moreover aromatization or isomerization effects have been observed. Aromatic compounds were produced to a reduced extent by thermo-catalytic pyrolysis of biomass-containing plastic waste compared to that of plastic waste indicating that the cellulose and lignin components of the waste lower the HZSM-5 catalyst activity.

An experimental study on thermo-catalytic pyrolysis of plastic waste using a continuous pyrolyser

A bench scale, two-stage, thermo-catalytic reactor equipped with a continuous feeding system was used to pyrolyse pure and waste plastics. Experiments using five zeolitic and clay-based catalysts of different forms (pellet and powders) and different plastic feedstocks – virgin HDPE, HDPE w1aste and mixed plastic waste (MPW) were compared to the control experiments – pyrolysis without catalyst. Results indicated that the two pelletized catalysts were the most promising for the conditions employed. Of these two, one with higher acidity and surface area was highly selective for the gasoline fraction (C5–C11) giving 80% from the total medium distillate conversion using virgin HDPE as feedstock. It also produced the least amount of olefins (17% for virgin HDPE, 4% for HDPE waste and 2% for MPW) and coke (<1% for virgin HDPE, 3% for HDPE waste and 5% for MPW), and the highest aromatics content (22% for virgin HDPE from un-distilled medium distillate, 5% for HDPE and 13% for MPW both from distilled medium distillate). The second pelletized catalyst exhibited high selectivity for the diesel fraction (C12–C25) giving 63% from the total medium distillate conversion using virgin HDPE as feedstock. The amount of coke deposited on the catalyst surface depended mainly on the mesopore volume, with less coke deposited as the mesopore volume increased. The variation in catalyst selectivity with acidity strength due to Lewis sites on the catalyst surface controls selectivity towards carbon chain length.

Thermo-catalytic pyrolysis of waste high-density polyethylene: Effect of γ-ray irradiation on degradation

ABSTRACTIn this work, the synergistic effect of the γ-ray irradiation and catalyst on the pyrolysis of High-Density Polyethylene (HDPE) waste was investigated in a batch reactor. Two catalysts, Zeolite Socony Mobil–5 (ZSM-5) and Ferric oxide, were used, and their loading was optimized. The results revealed that the degradation temperature significantly reduced with increasing dosage of irradiation. The complete pyrolysis of HDPE waste occurs at a temperature of 400°C and reaction time of 240 min (4 h), while in a case of irradiation-induced pyrolysis, there is higher yield and decrease in the residence time of pyrolysis. Irradiation with a higher dosage (2,000 kGy) increases the rate of thermo-catalytic pyrolysis for HDPE waste and gives maximum conversion.

Experimental Investigation on Thermocatalytic Pyrolysis of HDPE Plastic Waste and the Effects of Its Liquid Yield over the Performance, Emission, and Combustion Characteristics of CI Engine

An experimental investigation was carried out to study two process parameters of thermocatalytic pyrolysis of high density polyethylene (HDPE) plastic waste, and the liquid yield of pyrolysis (plastic oil) was analyzed over its working characteristics in a direct injection compression ignition (DICI) engine. A series of pyrolysis experiments with four different heating rates (5, 10, 15, and 20 °C/min) were performed in identical environments with the objective of analyzing the heating rate and residence time on end products. It was found that the liquid yield was maximum at the heating rate of 10 °C/min and the residence time decreases with an increase in the heating rate due to variation of reaction kinetics at different heating rates. The characterization of the plastic oil revealed that the major constituents belong to alkene, alkane, and alcohol functional groups; totally 90 six fuel range hydrocarbons were present ranging from C5 to C28, and the other thermophysical properties were comparable with th...

Thermo-Catalytic Pyrolysis of Waste Plastics from End of Life Vehicle

Pyrolysis of waste plastics is widely used recycling method. Owing to the end-of-life vehicles regulations, 95% of passenger cars and vehicles must reused/recovered after the dismantling. Pyrolysis of waste polyethylene and polypropylene obtained from end-of-life vehicles was investigated in a continuously stirred batch reactor using 500 and 600°C temperatures. To ensure the pyrolysis reactions the tested catalysts (5% of ZSM-5, HZSM-5, Ni-ZSM-5 and Fe-ZSM-5) were added directly to the mixtures of raw materials. Products of pyrolysis were separated into gases, pyrolysis oil and heavy oil, which was further analyzed by gas-chromatography, Fourier transformed infrared spectroscopy and other standardized methods. Based on the results it was concluded, that the catalysts significantly increase the yields of volatile products, and modify their composition. Especially the alkane/alkene ratio, the methane concentration and the concentration of branched hydrocarbon could be affected by the applied catalysts. Ni-ZSM-5 catalyst had the highest activity in methane production, while HZSM-5 catalyst proved effective in isomerization reactions. Using H-ZSM-5, Ni-ZSM-5, and Fe-ZSM-5 catalyst notably decreased average molecular weight of pyrolysis oils and significantly higher aromatic content was observed.

Thermo-catalytic pyrolysis of waste polyethylene bottles in a packed bed reactor with different bed materials and catalysts

Plastic waste is an increasing economic and environmental problem as such there is a great need to process this waste and reduce its environmental impact. In this work, the pyrolysis of high density polyethylene (HDPE) waste products was investigated using both thermal and catalytic cracking techniques. The experimental work was carried out using packed bed reactor operating under an inert atmosphere at 450°C. Different reactor bed materials, including sand, cement and white clay were used to enhance the thermal cracking of HDPE. In addition, the catalytic effect of sodium hydroxide, HUSY and HBeta zeolite catalysts on the degradation of HDPE waste was also investigated. The reactor beds were found to significantly alter the yield as well as the product composition. Products such as paraffins (⩽C44), olefins (⩽C22), aromatics (⩽C14) and alcohols (C16 and C17) were obtained at varying rates. The highest yield of liquid (82%) was obtained over a cement powder bed with a paraffin yield of 58%. The yield of paraffins and olefins followed separate paths, for paraffins it was found to increase in the order or Cement>White clay>Silica Sand, whereas for the olefins it was in the reverse order Silica Sand>White clay>Cement. The results obtained in this work exhibited a higher P/O ratio than expected, where the amount of generated paraffins was greater than 60% in most cases. Less olefin was generated as a consequence. This indicates that the product generated is more suited to be used as a fuel rather than as a chemical feedstock. The carbon chain length was narrowed to C10–C28 when the zeolitic catalysts were employed, as well as a significant yield of aromatics was obtained mainly naphthalene and d-limonene as an indication that the products obtained are fuel-like products.

Thermo-catalytic pyrolysis of polystyrene in the presence of zinc bulk catalysts

Zinc bulk catalysts (Zn, ZnO and ZnCl2) were used for the thermo-catalytic pyrolysis of EPSW and were found with high activity and selectivity of products. Thermo-catalytic pyrolysis was carried out using an efficient Pyrex batch reactor. Zn metal catalyst was found as the best catalyst amongst the zinc bulk catalysts for the cost effective pyrolysis of EPSW (expanded polystyrene waste). The yield of liquid products at 450°C, 120min heating time and 1:0.2 feed to catalyst ratio was 96.73±0.12wt.% with 2.47wt.% toluene, 1.16wt.% ethylbenzene, 47.96wt.% styrene monomer and 1.90wt.% α-methylstyrene. The components of liquid products were separated by fractional distillation and found with further thermal pyrolysis in addition to cyclization and recombination reactions. During the fractional distillation, much product variations were observed. High molecular weight aromatic hydrocarbons decreased with the associated increase of low molecular weight aromatic hydrocarbons, particularly toluene and ethylbenzene.

Comparison of real waste (MSW and MPW) pyrolysis in batch reactor over different catalysts. Part II: Contaminants, char and pyrolysis oil properties

Pyrolysis of real wastes (MPW and MSW) has been investigated at 500°C, 550°C and 600°C using Y-zeolite, β-zeolite, equilibrium FCC, MoO3, Ni-Mo-catalyst, HZSM-5 and Al(OH)3 as catalysts. The viscosity of pyrolysis oils could be decreased by the using of catalysts, especially by β-zeolite and MoO3. Both carbon frame and double bound isomerization was found in case of thermo-catalytic pyrolysis. Char morphology and texture analysis showed more coke deposits on the catalyst surface using MSW raw material. Pyrolysis oils had K, S, P Cl, Ca, Zn, Fe, Cr, Br and Sb as contaminants; and the concentrations of K, S, P, Cl and Br could be decreased by the using of catalysts.

Olefin Rich Fractions for Polymer Additive Synthesis Obtained from Waste Materials (RDF and MPW)

This paper focused on the thermal and thermo-catalytic pyrolysis of refuse derived fuels (RDF) and municipal plastic wastes (MPW) in a batch reactor at 450¡C. Two commercialized zeolite catalysts were used in order to enhance the quality of the feedstocks petrochemical productions (e.g. olefin rich pyrolytic oils). Analyses of products were carried out using GC, FTIR, EDXRFS and SEC. It was discovered that the presence of catalysts in the processes have a considerable effect not only on the quantity of product yields but also to the product compositions. X-ray analysis had demonstrated significant contaminant levels in each product obtained from only RDF pyrolysis. Characterization of pyrolytic oils indicated the existence of hydrocarbons between C5 and C29, with different structures (isomers). New routes for the utilization of products obtained by waste plastic pyrolysis have been investigated. α-olefin-succinic-anhydride intermediate based additives have been developed and tested in polymer blends.

Hydrocarbon Fractions Obtained from Recycling of Waste Materials

Pyrolysis of contaminated waste plastics was carried out in a laboratory scale batch reactor at 450 °C under nitrogen atmosphere. Raw materials were original high density polyethylene (HDPE) and waste motor oil flasks from industrial sector. Volatile products were passed through a fixed catalyst bed with temperature of 350 °C. In the experiments Y-zeolite, β-zeolite, HZSM-5, Co/Mo and Ni/Mo catalysts were used. Three product fractions were obtained: gas, liquid and heavy oil. Catalysts had mainly effect on the gas and liquid yields, the amount of the residue did not show significant differences in the case of the same raw material. By pyrolysis of contaminated raw material higher volatile product yield could be observed compared to pyrolysis of the original raw material. Catalysts increased gas yields and had influence on the composition of products. Most significant effect could be observed in the case of Y-zeolite and β-zeolite catalysts. Contaminant level of liquid products could be decreased in case of thermo-catalytic pyrolysis, which is a key property for further application of the pyrolysis products.

Two stages catalytic pyrolysis of refuse derived fuel: Production of biofuel via syncrude

Thermo-catalytic pyrolysis of refuse derived fuels with different catalysts had been conducted in a two stages process due to its important potential value as fuel. The first stage was a pure thermal pyrolysis in a horizontal tubular reactor with feed rate of 0.5kg hourly. The second stage was a semi-batch process in the presence of catalysts. Results showed that the tested catalysts significantly have affected the quantity of products. E.g. gas yield could be increased with 350% related to the catalyst free case using ZSM-5, while that of pyrolytic oil was 115% over Y-zeolite. Gases consisted of mainly CO and CO(2) obtained from the tubular reactor, while dominantly hydrocarbons from the second stage. Ni-Mo-catalyst and Co-Mo-catalyst had shown activity in pyrolytic oil upgrading via in-situ hydrogenation-dehydrogenation reactions. Sulphur, nitrogen and chlorine level in pyrolytic oils could be significantly declined by using of catalysts.