Pyrolysis and catalytic pyrolysis as a recycling method of waste CDs originating from polycarbonate and HIPS

Pyrolysis appears to be a promising recycling process since it could convert the disposed polymers to hydrocarbon based fuels or various useful chemicals. In the current study, two model polymers found in WEEEs, namely polycarbonate (PC) and high impact polystyrene (HIPS) and their counterparts found in waste commercial Compact Discs (CDs) were pyrolysed in a bench scale reactor. Both, thermal pyrolysis and pyrolysis in the presence of two catalytic materials (basic MgO and acidic ZSM-5 zeolite) was performed for all four types of polymers. Results have shown significant recovery of the monomers and valuable chemicals (phenols in the case of PC and aromatic hydrocarbons in the case of HIPS), while catalysts seem to decrease the selectivity towards the monomers and enhance the selectivity towards other desirable compounds.     

Conversion of LDPE into transportation fuels by a two-stage process using Ni/Al-SBA-15 as catalyst

Ni/Al-SBA-15 catalysts with Si/Al atomic ratios within the 20–135 range were prepared by a post synthesis grafting procedure, having nickel contents between 6 and 11 %. The addition of Ni to the Al-SBA-15 support caused a decrease of the BET surface area and pore volume. Additionally, larger Ni particles were attained over the catalysts with higher Si/Al atomic ratios, indicating the existence of some interaction between aluminium species and nickel particles. Ni/Al-SBA-15 catalysts displayed remarkable properties for the preparation of diesel fuels in the hydroreforming of the oils obtained from the LDPE thermal cracking. On increasing the Si/Al atomic ratios of the Ni/Al-SBA-15 catalysts, higher share of light and heavy diesel were attained, the sum reaching a maximum (67.3 %) for Ni/Al-SBA-15(70). This was caused by the higher extent of oligomerization reactions on enhancing the Si/Al atomic ratio. Additionally, around 85–90 % of the starting olefins were successfully hydrogenated and the aromatic content was rather low (below 5 %), without almost any polyaromatic compound (<0.1 %).     

Transportation fuel production by combination of LDPE thermal cracking and catalytic hydroreforming

Fuel production from plastics is a promising way to reduce landfilling rates while obtaining valuable products. The usage of Ni-supported hierarchical Beta zeolite (h-Beta) for the hydroreforming of the oils coming from LDPE thermal cracking has proved to produce high selectivities to gasoline and diesel fuels (>80%). In the present work, the effect of the Ni loading on Ni/h-Beta is investigated in the hydroreforming of the oils form LDPE thermal cracking. h-Beta samples were impregnated with Ni nitrate, calcined and reduced in H₂ up to 550 °C to achieve different Ni contents: 1.5%, 4%, 7% and 10%. Larger and more easily reducible metal particles were obtained on Ni 7%/h-Beta and Ni 10%/h-Beta. Hydroreforming tests were carried out in autoclave reactor at 310 °C, under 20 bar H₂, for 45 min. Ni content progressively increased the amount of gases at the expenses of diesel fractions, while gasoline remained approximately constant about 52–54%. Maximum selectivity to automotive fuels (～81%) was obtained with Ni 7%/h-Beta. Ni loading also enhanced olefins saturation up to Ni 7%/h-Beta. High cetane indices (71–86) and octane numbers (89–91) were obtained over all the catalysts. Regarding the different studied Ni contents, Ni 7%/h-Beta constitutes a rather promising catalyst for obtaining high quality fuels from LDPE thermal cracking oils.     

NiO-CuO/ZSM-5催化剂对催化裂化烟气的脱硫脱硝性能

采用浸渍法制备了不同NiO和CuO质量分数的NiO-CuO/ZSM-5催化剂,并以CH4为还原剂研究了NiO-CuO/ZSM-5催化剂对催化裂化烟气的脱硫脱硝活性。XRD分析结果表明,NiO质量分数为4%、CuO质量分数为6%的催化剂4%NiO-6%CuO/ZSM-5中的ZSM-5结构完好,CuO和NiO高度分散在ZSM-5骨架中,表明具有较好的催化活性。4%NiO-6%CuO/ZSM-5的脱硫脱硝起活温度均较低,无氧条件下最高NO转化率和SO2转化率分别为94.7%和95.9%,O2体积分数为1.0%时的NO转化率和SO2转化率分别为97.7%和89.0%。     

Characteristics of Suspended Solids and Micropollutants in First-Flush Highway Runoff

Suspended solids (SS) in the first-flush runoff on highway was monitored in six continuous events from October to December 2000 in Winterthur, Switzerland, and some characteristics of particle-bound micropollutants such as polycyclic aromatic hydrocarbons, phthalate esters, and heavy metals were investigated. Among the three micropollutants, concentration of polycyclic aromatic hydrocarbon showed similar behavior to SS. Phthalate esters showed almost no correlation, whereas heavy metals showed increase in its concentration with lowers SS concentration. Three different characteristics of the micropollutants in the first flush indicated that the first-flush phenomenon is complex, and they may not be simply stated when considering suspended solids as an index for the runoff.     

Reduction of tar using cheap catalysts during sewage sludge gasification

Solid-fuel conversion or gasification study of sewage sludge and energy recovery has become increasingly important because energy recovery and climate change are emerging issues. Various types of catalysts, such as dolomite, steel slag and calcium oxide, were tested for tar reduction during the sewage sludge gasification process. For the experiments on sewage sludge gasification reactions and tar reduction using the catalysts, a fixed bed of laboratory-scale experimental apparatus was set up. The reactor was made of quartz glass using an electric muffle furnace. The sewage sludge samples used had moisture contents less than 6%. The experimental conditions were as follows: sample weight was 20 g and reaction time was 10 min, gasification reaction temperature was from 600 to 800°C, and the equivalence ratio was 0.2. The quantity of catalysts was 2–6 g, and temperatures of catalyst layers were 500–700°C. As the reaction temperature increased up to 800°C, the yields of gaseous products and liquid products increased, whereas char and tar products decreased, showing effects on gas product compositions. These results were considered to be due to the increase of the water-gas reaction and Boudouard reaction. In the case of experiments with catalysts, dolomite (4 g), steel slag (6 g) and calcium oxide (6 g) were used. When the temperature of catalysts increased, the weight of the tar produced decreased with different cracking performances by different catalysts. Reforming reactions were considered to occur on the surface of dolomite, steel slag and calcium oxide, causing cracking of the hydrocarbon structure, which eventually showed reduced tar generation.     

Waste catalysts for waste polymer

Catalytic cracking of high-density polyethylene (HDPE) over fluid catalytic cracking (FCC) catalysts (1:6 ratio) was carried out using a laboratory fluidized bed reactor operating at 450 degrees C. Two fresh and two steam deactivated commercial FCC catalysts with different levels of rare earth oxide (REO) were compared as well as two used FCC catalysts (E-Cats) with different levels of metal poisoning. Also, inert microspheres (MS3) were used as a fluidizing agent to compare with thermal cracking process at BP pilot plant at Grangemouth, Scotland, which used sand as its fluidizing agent. The results of HDPE degradation in terms of yield of volatile hydrocarbon product are fresh FCC catalysts>steamed FCC catalysts approximately used FCC catalysts. The thermal cracking process using MS3 showed that at 450 degrees C, the product distribution gave 46 wt% wax, 14% hydrocarbon gases, 8% gasoline, 0.1% coke and 32% nonvolatile product. In general, the product yields from HDPE cracking showed that the level of metal contamination (nickel and vanadium) did not affect the product stream generated from polymer cracking. This study gives promising results as an alternative technique for the cracking and recycling of polymer waste.     

Reductive hydrothermal treatment of sewage sludge

The United States and the European Union each generate around 6900 million dry tons of sewage sludge annually. This is disposed of by land application, landfilling, incineration and other approaches. Reductive hydrothermal (HT) treatment refers here to simple aqueous systems heated and pressurized above 300 degrees C/100bar under anoxic and/or reducing conditions. The purpose of this study was to examine the HT treatment of municipal sewage sludge and infectious fecal microbial cultures with respect to waste volume reduction, biological sterilization, and the generation of usable hydrocarbon product mixtures. These endpoints from HT treatment also were compared to those from pyrolysis. HT at 400 degrees C/150bar transformed sewage sludge solids into complex gas phase (4%) and liquid (6%) hydrocarbon mixtures (approximately 11% combined yield), along with similar amounts (5%) of solid residues. HT products in the aqueous phase (e.g., alcohols) were present but not analysed. Viable mixed fecal cultures (10(9) colony forming units/mL) were completely sterilized by HT treatment, and a hydrocarbon mixture also was generated from the cells, but it was markedly different from that resulting from HT of the sludge. The hydrocarbon assemblage generated from the sludge included n-hydrocarbons (C(9)-C(20)) and alkyl substituted benzenes, phenols, and related compound series of higher mass (e.g., indanes, naphthalenes). Light aromatic parent compounds were significantly less abundant than their substituted C(1)-C(5) alkyl series and there was a paucity of N-, O- and S-heterocycles and polycyclic systems with more than three fused rings. This was different from the products of pyrolysis which were dominated by a relatively simple mixture of linear and branched hydrocarbons and their oxidized homologues (e.g., aldehydes).     

Ethanol washing of PAH-contaminated soil and Fenton oxidation of washing solution

As a means to remediate soil contaminated by polycyclic aromatic hydrocarbons, we investigated a combined process involving ethanol washing followed by a Fenton oxidation reaction. Artificial loamy soil was contaminated with various representative polycyclic aromatic hydrocarbons (i.e., fluorene, anthracene, pyrene, benzo(b)fluoranthene, or benzo(a)pyrene) at concentrations ten times higher than regulatory soil standards of The Netherlands or Canada, and then washed four times in ethanol, which reduced the concentration of polycyclic aromatic hydrocarbon contamination to below the regulatory standard. Fenton oxidation of ethanol solutions containing anthracene, benzo(a)pyrene, pyrene, acenaphthylene, acenaphthene, benz(a)anthracene, benzo(j)fluoranthene, or indeno(1,2,3-cd)pyrene showed a removal efficiency of 73.3%–99.0%; by contrast, solutions containing naphthalene, fluorene, fluoranthene, phenanthrene, or benzo(b)fluoranthene showed a removal efficiency of 9.6%–27.6%. Since each of the nonremediated polycyclic aromatic hydrocarbons, excluding benzo(b)fluoranthene, are easily biodegradable, these results indicate that the proposed treatment can be successfully applied to polycyclic aromatic hydrocarbon-contaminated soil that does not contain high concentrations of benzo(b)fluoranthene. The main reaction products resulting from Fenton oxidation of ethanol solutions containing anthracene or benz(a)anthracene were anthraquinon or benz(a)anthracene-7,12-dione, respectively; while 1,8-naphthalic anhydride was produced by solutions of acenaphthylene and acenaphthene, and 9-fluorenone by a fluorene solution. Received: June 9, 1998 / Accepted: March 24, 1999     

Chemical Oxidation Performance in High Temperature,Saline Groundwater Impacted With Hydrocarbons

A series of laboratory microcosm experiments and a field pilot test were performed to evaluate the potential for in situ chemical oxidation (ISCO) of aromatic hydrocarbons and methyl tertiary butyl ether (MTBE), a common oxygenate additive in gasoline, in saline, high temperature (more than 30 °C) groundwater. Groundwater samples from a site in Saudi Arabia were amended in the laboratory portion of the study with the chemical oxidants, sodium persulfate (Na₂S₂O₈) and sodium percarbonate (Na₂(CO₃)₂), to evaluate the changes in select hydrocarbon and MTBE concentrations with time. Almost complete degradation of the aromatic hydrocarbons, naphthalene and trimethylbenzenes (TMBs), was found in the groundwater sample amended with persulfate, whereas the percarbonate‐amended sample showed little to no degradation of the target hydrocarbon compounds in the laboratory. Isotopic analyses of the persulfate‐amended samples suggested that C‐isotope fractionation for xylenes occurred after approximately 30 percent reduction in concentration with a decline of about 1 percent in the δ¹³C values of xylenes. Based on the laboratory results, pilot‐scale testing at the Saudi Arabian field site was carried out to evaluate the effectiveness of chemical oxidation using nonactivated persulfate on a high temperature, saline petroleum hydrocarbon plume. Approximately 1,750 kg of Na₂S₂O₈ was delivered to the subsurface using a series of injection wells over three injection events. Results obtained from the pilot test indicated that all the target compounds decreased with removal percentages varying between 86 percent for naphthalene and more than 99 percent for the MTBE and TMBs. The benzene, toluene, ethylbenzene, and xylene compounds decreased to 98 percent on average. Examination of the microbial population upgradient and downgradient of the ISCO reactive zone suggested that a bacteria population was present following the ISCO injections with sulfate‐reducing bacteria (SRB) being the dominant bacteria present. Measurements of inorganic parameters during injection and postinjection indicated that the pH of the groundwater remained neutral following injections, whereas the oxidation–reduction potential remained anaerobic throughout the injection zone with time. Nitrate concentrations decreased within the injection zone, suggesting that the nitrate may have been consumed by denitrification reactions, whereas sulfate concentrations increased as expected within the reactive zone, suggesting that the persulfate produced sulfate. Overall, the injection of the oxidant persulfate was shown to be an effective approach to treat dissolved aromatic and associated hydrocarbons within the groundwater. In addition, the generation of sulfate as a byproduct was an added benefit, as the sulfate could be utilized by SRBs present within the subsurface to further biodegrade any remaining hydrocarbons. ©2015 Wiley Periodicals, Inc.     

Decomposition of mixed plastics consisting of polypropylene and polyethylene terephthalate into oils over titania/silica catalysts

The catalytic decomposition of mixed plastics consisting of polypropylene (PP) and polyethylene terephthalate (PET) has been investigated over titania/silica catalysts at 698 K. The yield of oil produced was about 70%, and the large amounts of C₁₈₊ hydrocarbons this contained was from the aromatics in PET. Gas was also produced, including C₃–C₅ hydrocarbons. The carbon-number fractions in the oil was influenced by the PET/(PP + PET) ratios and the catalyst weight. The titania/silica catalysts could be used repeatedly, and after they had been fouled, could be regenerated. From the Fourier Transform Infrared (FT–IR) spectroscopic data of adsorbed pyridine on the catalyst surface, most of the acid sites of the titania/silica catalysts were found to be Lewis sites where the hydride abstracted from PP pyrolysates react with PET pyrolysates to form oil and gas. Received: July 19, 2000 / Accepted: October 20, 2000     

Deactivation and regeneration of ZSM-5 zeolite in catalytic pyrolysis of plastic wastes

In this work, a study of the regeneration and reuse of ZSM-5 zeolite in the pyrolysis of a plastic mixture has been carried out in a semi-batch reactor at 440 °C. The results have been compared with those obtained with fresh-catalyst and in non-catalytic experiments with the same conditions. The use of fresh catalyst produces a significant change in both the pyrolysis yields and the properties of the liquids and gases obtained. Gases more rich in C3-C4 and H₂ are produced, as well as lower quantities of aromatic liquids if compared with those obtained in thermal decomposition. The authors have proved that after one pyrolysis experiment the zeolite loses quite a lot of its activity, which is reflected in both the yields and the products quality; however, this deactivation was found to be reversible since after regeneration heating at 550 °C in oxygen atmosphere, this catalyst recovered its initial activity, generating similar products and in equivalent proportions as those obtained with fresh catalyst.     

Pyrolysis of waste tyres: A review

Approximately 1.5 billion tyres are produced each year which will eventually enter the waste stream representing a major potential waste and environmental problem. However, there is growing interest in pyrolysis as a technology to treat tyres to produce valuable oil, char and gas products. The most common reactors used are fixed-bed (batch), screw kiln, rotary kiln, vacuum and fluidised-bed. The key influence on the product yield, and gas and oil composition, is the type of reactor used which in turn determines the temperature and heating rate. Tyre pyrolysis oil is chemically very complex containing aliphatic, aromatic, hetero-atom and polar fractions. The fuel characteristics of the tyre oil shows that it is similar to a gas oil or light fuel oil and has been successfully combusted in test furnaces and engines. The main gases produced from the pyrolysis of waste tyres are H₂, C₁–C₄ hydrocarbons, CO₂, CO and H₂S. Upgrading tyre pyrolysis products to high value products has concentrated on char upgrading to higher quality carbon black and to activated carbon. The use of catalysts to upgrade the oil to a aromatic-rich chemical feedstock or the production of hydrogen from waste tyres has also been reported. Examples of commercial and semi-commercial scale tyre pyrolysis systems show that small scale batch reactors and continuous rotary kiln reactors have been developed to commercial scale.     

Pyrolysis of aseptic packages (tetrapak) in a laboratory screw type reactor and secondary thermal/catalytic tar decomposition

Pyrolysis of aseptic packages (tetrapak cartons) in a laboratory apparatus using a flow screw type reactor and a secondary catalytic reactor for tar cracking was studied. The pyrolysis experiments were realized at temperatures ranging from 650 °C to 850 °C aimed at maximizing of the amount of the gas product and reducing its tar content. Distribution of tetrapak into the product yields at different conditions was obtained. The presence of H₂, CO, CH₄, CO₂ and light hydrocarbons, HCx, in the gas product was observed. The Aluminum foil was easily separated from the solid product. The rest part of char was characterized by proximate and elemental analysis and calorimetric measurements. The total organic carbon in the tar product was estimated by elemental analysis of tars. Two types of catalysts (dolomite and red clay marked AFRC) were used for catalytic thermal tar decomposition. Three series of experiments (without catalyst in a secondary cracking reactor, with dolomite and with AFRC) at temperatures of 650, 700, 750, 800 and 850 °C were carried out. Both types of catalysts have significantly affected the content of tars and other components in pyrolytic gases. The effect of catalyst on the tetrapack distribution into the product yield on the composition of gas and on the total organic carbon in the tar product is presented in this work.     

废聚苯乙烯泡沫塑料的催化裂解

为了对废聚苯乙烯泡沫塑料（WPS）资源化利用,通过对WPS进行催化裂解的方法,研究了催化剂种类和裂解温度对裂解时间、裂解油产率、苯乙烯回收率以及裂解油纯度的影响。研究结果表明,催化剂种类和裂解温度对裂解反应有着重要影响。裂解温度升高,裂解油产率提高,裂解时间缩短,但苯乙烯选择性下降;低于380 ℃时,氧化钙的裂解油产率和裂解时间优于氧化铝和氯化铝,但苯乙烯的选择性劣于氧化铝和氯化铝;高于400 ℃时,氯化铝、氧化铝和氧化钙的催化活性接近。在实验条件下,WPS催化裂解的最佳催化剂为氯化铝,380 ℃下的裂解时间为25 min,裂解油产率为85.48%,裂解油中苯乙烯含量为80.66%（w）,且副产物较少。     

Individual and simultaneous degradation of brominated high impact polystyrene and brominated acrylonitrile-butadiene-styrene and removal of heteroelements (Br,N, and O) from degradation oil by multiphase catalytic systems

Brominated high-impact polystyrene (HIPS-Br), which contained decabromodiphenyl ether flame retardant, and brominated acrylonitrile butadiene styrene (ABS-Br), which contained bromine-containing epoxy-type flame retardant, were degraded at 450°C individually and in a 1/1 mixture by a thermal and catalytic procedure using folded sheet mesoporous (FSM) and ZSM-5 zeolite in liquid phase contact mode. The two polymers produced similar degradation oils but at a higher yield for HIPS-Br. However, the composition and distribution of Br-, N-, and O-containing compounds depended on the type of flame retardant in HIPS-Br and ABS-Br. Multiphase catalytic systems consisting of FSM in liquid phase contact mode and various CaH-, FeO-, CoMo-, and NiMo-based catalysts, or combinations of these catalysts, in vapor phase contact mode were used to decrease the amount of heteroatoms (Br, N, and O) in the degradation oils. Each system gave particular results in terms of mass balance and concentrations of heteroatoms. A FSM (liquid phase contact)/CaHC (vapor phase contact) combination was the best catalytic system to remove Br-, N-, and O-containing compounds from degradation oils.     

Effect of Decalin Solvent on the Thermal Degradation of HDPE

The thermal cracking of HDPE in presence of different amounts of decalin was studied and compared with the reaction carried out in the absence of solvent. The decalin favours the mass and heat transfer during the reaction. In addition, it modifies the thermal degradation mechanism, which facilitates the formation of specific products. The use of decalin substantially increases the C₅–C₃₂ yield in comparison with the solventless reaction. In all cases, linear hydrocarbons such as n-paraffins, α-olefins and α,ω-dienes were detected. Increasing the decalin/plastic ratio led to enhanced α-olefin and n-paraffins yields, but the increase was more significant in the case of α-olefins, which are valuable compounds useful as raw chemicals. A reaction mechanism was proposed to explain the results obtained in presence of decalin. In these reactions, intramolecular radical transfer, secondary radical β-scission and hydrogen transfer from both decalin to intermediate radicals and from the polymer chain to regenerate the decalin play a significant role in determining the plastic conversion and the relative amounts of each product.     

Aromatization of waste polyolefin pyrolysate over H-ZSM-5 zeolite-supported gallium oxide catalysts

H-ZSM-5 zeolite-supported gallium oxides were studied as aromatization catalysts for polyolefin pyrolysate. The catalysts were prepared by a conventional physical mixing method with a gallium content of 1.0 and 4.5 wt% and were reduced in flowing hydrogen at 585°C. To test their activity, a polyolefin sample was pyrolyzed and passed over a heated catalyst layer; the product was analyzed by gas chromatography/mass spectrometry. A continuous-flow fixed-bed reactor was used for aromatization of a model gas of polyolefin pyrolysate. For chlorine-free sources at 450°C, the catalyst with only 1.0 wt% gallium exhibited activity comparable to a gallium silicate catalyst. For chlorine-contaminated sources, the catalyst with 4.5 wt% gallium sustained catalytic activity for long periods. From the activity test results, it was found that zeolite-supported gallium catalysts prepared by the physical mixing method are suitable for converting polyolefin into aromatic hydrocarbons.     

Ce-Fe/ZSM-5催化剂NH3选择性催化还原NO性能研究

通过浸渍法将Ce和Fe负载在ZSM-5载体上,制备了1.40%Fe/ZSM-5（数字为金属组分的质量分数,下同）、0.25%Ce/ZSM-5、0.25%Ce-1.40%Fe/ZSM-5和0.50%Ce-1.40%Fe/ZSM-5催化剂。对催化剂进行了表征并研究了其NH₃选择性催化还原（NH₃-SCR）NO的性能。实验结果表明,双金属改性的0.25%Ce-1.40%Fe/ZSM-5催化剂的活性温度窗口范围最广,在350~450 ℃范围内NO转化率超过98%。Ce和Fe以无定型氧化物的形态良好分散在ZSM-5载体表面,没有改变ZSM-5分子筛的微孔结构。0.25%Ce-1.40%Fe/ZSM-5催化剂的有效还原峰面积更大,孤立Fe³⁺和Ce⁴⁺物种含量更多,氧化还原性能显著,催化剂表面具有丰富的中等强度酸性位且酸量较大,有利于 NH₃-SCR 反应的进行。     

芳香烃清洁硝化催化剂

综述了国内外有关芳香烃硝化过程中替代硫酸的催化剂的研究进展;介绍了沸石类催化剂、粘土类催化剂、离子交换树脂催化剂、固载化液体酸催化剂、金属氧化物及金属盐催化剂、杂多酸催化剂以及固体超强酸催化剂的合成及催化效率与优缺点.