Development of a catalytic cracking process for converting waste plastics to petrochemicals

The catalytic degradation of polyolefin using H-gallosilicates was examined using a bench-scale reactor (0.8kg/h) with semicontinuous feeding and the following plastics: (1) low-density polyethylene (LDPE) pellets; (2) linear low-density polyethylene (L-LDPE) pellets; (3) high-density polyethylene (HDPE) pellets; (4) polypropylene (PP) pellets; (5) polyolefin obtained from pulverized industrial waste plastics. The yields of liquid compounds from these materials, which were aromatics in most cases, ranged from 55wt% to 68wt%. With an increase in the ratio of total reactant to catalyst, the liquid yield remained the same. Yields of benzene, toluene, and xylenes (BTXs) decreased rapidly to below 50wt% at a ratio of more than 30. Differences in this ratio for BTXs were always small and were independent of the material. Only about half of the gas product was propane with a fresh catalyst. When the experiments were repeated, propylene, isobutane, and isobutene were found to increase.     

Decomposition reactions of epoxy resin and polyetheretherketone resin in sub- and supercritical water

Epoxy resin and polyetheretherketone (PEEK) resin were decomposed into their monomers such as phenol, cresols, and their analogues by thermal treatment in sub- and supercritical water in a 10-ml tubing bomb reactor. The addition of basic compounds such as Na₂CO₃ was effective in promoting the decomposition reaction of the resins. In the reaction of epoxy resin, the yield of identified products reached 10% for the reaction at 703K over 1h. In the reaction of PEEK resin, the total yield of phenol and dibenzofuran reached 88% for the reaction at 703K over 3h. Chemical participation of water in the decomposition reaction was confirmed by the reaction of dinaphthylether.     

Pore structure and adsorption properties of activated carbon prepared from granular molded waste paper

We have previously manufactured activated carbon using waste paper board, which was prepared by adding 8% phenol resin adhesive to torn waste newspaper and hot-pressing. In this study, the pretreatment process of the raw material was simplified; the waste paper was extruded to form granules. The activated carbon was manufactured by the carbon dioxide activation method using the granules as the raw material. The properties of the activated carbon were evaluated based on the pore structure, the iodine adsorption number, and the adsorption of toluene vapor in a sealed chamber. The activated carbon, which was manufactured at an activation temperature of 1100°C and a treatment time of 60min, exhibited a specific surface area of 1241m²/g and an iodine adsorption number of 1120mg/g. These results were similar to those obtained for two commercially available activated carbons. The extent of toluene vapor adsorption by this activated carbon was similar to that observed for the two commercial activated carbons over a period of 130min.     

The contemporary Oceania zinc cycle: one-year stocks and flows

The material flow approach provides a framework from which to address resource management and estimate gross environmental impacts, both spatially and temporally. In this article, the major flows of zinc in Oceania over its entire life-cycle are examined; these include production (mining, milling, and refining), fabrication and manufacturing of semi- and finished products, use, and the waste management system. Comprehensive mass balances were applied to determine the zinc flows, including the quantities of zinc entering stocks in waste and in-use reservoirs. The Oceania cycle shows that substantial amounts of zinc (about 1120Gg/year) are mined on the continent. The total flow of zinc in finished products entering the use stage is about 8.6kg/(capita.year), substantially exceeding the zinc flow in discarded products. This difference, about 7.2kgZn/(capita.year) on average, is added to the in-use reservoir, largely for galvanizing applications in domestic construction and transportation. Less than 60% of all discarded zinc entering the waste management system is recycled. Much of the remaining discarded zinc is diluted into other waste streams, where recovery and recycling are probably not economically feasible.     

Catalytic decomposition of hydrocarbon into hydrogen and carbon in a spouted-bed reactor as the second-stage reactor of a plastic recycling process

A two-stage process for the chemical recycling of plastics is proposed. In this process, which consists of two reactors, plastics are converted into hydrogen and carbon. In the first reactor, plastic chips are thermally decomposed into hydrocarbons. In the second reactor, the hydrocarbons formed in the first reactor are catalytically decomposed into carbon and hydrogen. In this study, in order to obtain basic data for the second reactor, propene was catalytically decomposed in a laboratory-scale spouted-bed reactor (600mm high, 21.6mm internal diameter, made of SUS304). The effect of the type of spouting medium used on the decomposition behavior of propene was investigated using four types of spouting medium (nickel-plated -alumina, palladium-plated -alumina, nickel-impregnated -alumina, and -alumina). The nickel-impregnated -alumina gave the best propene conversion and hydrogen yield.     

Thermal cracking of oils from waste plastics

Thermal cracking of decomposed waste plastic oil produces a good yield of olefins. The solvent extraction of such waste plastic oil seems to be efficient for increasing gas yields and recycling monomers. To assess the potential of monomer recovery from municipal waste plastics, the oils were cracked using a laboratory-scale quartz-tube reactor. The waste plastic oils were provided by two commercial plants of the Sapporo Plastic Recycle Co. and the Dohoh Recycle Center Co. in Japan. A model waste plastic oil made in a laboratory was also examined. Yields of ethene, propene, and other products were measured at different temperatures. Two-step pyrolysis reduces coking compared with the direct thermal degradation of plastics. The raffinates from waste plastic oils extracted by sulfolane were also cracked. The primary products were almost the same as those from nontreated oils. The maximum total gas yield was 78wt%–85wt% at 750°C, an increase of about 20wt% compared with that of nonextracted oil. Solvent extraction removes stable aromatic hydrocarbons such as styrene, which is more coked than cracked.     

The contemporary copper cycle of Asia

A regional stock and flow model for an industrial metal was developed based on the substance-flow framework. Using this model, the contemporary copper cycle of the Asian region was constructed by aggregating country-level production and import and export data for different stages of the copper cycle. The reliability and availability of data were assessed both qualitatively and quantitatively. Asia as a region is a net importer of copper. There is a significant build-up of copper in use at a rate of nearly 3TgCu/year. The per capita generation of copper waste (0.4kgCu/(capita-year)) and the rate of secondary recovery of copper are low compared with Europe and North America. Japan's rates of use, waste generation, and recycling of copper are all much larger than the continental average. A tremendous potential exists in the region to utilize the copper content of the in-use reservoir, and subsequently to enhance copper recycling rates in the future. A set of metrics for the copper cycle is suggested in order to address sustainability issues related to resource policy and the environmental management of copper.     

Solid State Reactions of Potato Starch with Urea and Biuret

Reaction of granular potato starch with urea and biuret resulted in the formation of products, which were soluble neither in cold nor boiling water. The net reaction was a monosubstitution of the hydrogen atom in one hydroxyl group in each D-glucose unit of starch with the either CO–NH₂ or CO–NH–CO–NH₂ moiety, respectively. Properties of the products, particularly these with urea, depended on the mode of reaction. Reactions were carried out in the microwave oven as well as with convection heating. The products retained the granular form of starch but a vast majority of granules were damaged. -Amylolysis of those materials revealed that their susceptibility to the enzyme increasing in the order: starch-amylolysis with simultaneous insolubility in water make these products suitable as ruminant fodder and, eventually, biodegradable material.     

Degradation of chlorinated dioxin in denitrifying activated sludge from leachate treatment plant of a landfill

The degradation rate of dioxins added to the activated sludge from a leachate treatment plant of a landfill under denitrification conditions was estimated using six bioreactors. Over 99% of the added dioxins (600ng) were degraded within 7 days. Furthermore, continuous cultivation was carried out for 1 month. The activated sludge degraded 600ng of dioxins (that is, all of the added dioxins) placed in each reactor every 7 days, and this activity was maintained for 35 days. Under aerobic conditions with this sludge, the dioxins were not degraded in 7 days, but 90% of the 600ng of dioxins was degraded in 35 days. The high level of activity observed in the present study may only occur under anaerobic conditions, especially under denitrifying conditions.     

Landfill mining and waste characterization: a strategy for remediation of contaminated areas

This article describes landfill-mining tests, including excavation, screening, and fraction characterization, carried out in the Msalycke and Gladsax landfills for municipal solid waste (MSW) in Sweden. The excavated waste in these two sites was 17–22 and 23–25 years old, respectively. The main part of Msalycke was unaffected by degradation, and during excavations no substantial amount of biogas was detected. After screening, three size fractions were obtained: <18mm, 18–50mm, and >50mm. Soil amendment and anaerobic digestion with energy extraction are suggested for the first and second fraction, respectively. Incineration with energy recovery is possible with the third fraction after any coarse (inert) material is removed, and construction/demolition waste can easily be recycled provided that it is not contaminated by hazardous material. Excavated waste taken from different depths was also analysed and compared in relation to composition, calorific value, and leachate constituents.     

A carbon-13 method for evaluating degradation of starch-based polymers

A new method for evaluating biodegradability of starch-based and certain other polymer blends uses the pre- and postexposure stable carbon isotope composition of material coupled with weight loss data to determine which components have degraded. The naturally occurring stable isotope of carbon.¹³C, is enriched in corn starch (¹³C, approx. –11) compared to petroleum-derived synthetic polymers (¹³C, approx. –32). Results on starch-synthetic polymer blends indicate that the ¹³C signatures of these blends are near-linear mixtures of their component ¹³C. Values of a ¹³C for starch-synthetic polymer blends exposed to biologically active laboratory soil and artificial seawater conditions are depleted in¹³C compared to unexposed samples, suggesting loss of the starch component. Combined with weight loss data for the exposed samples, the ¹³C values are statistically consistent with models requiring loss of the soluble component glycerin, followed by loss of starch, then petrochemical polymer, or simultaneous loss of starch and petrochemical polymer. Replicate ¹³C analyses of starch-synthetic polymer blends increase the statistical power of this relatively inexpensive, accessible technique to discriminate between degrading components.     

What substances or objects should be recycled? The recycling legislative experience in Taiwan

The legislative framework of waste management in Taiwan has never been efficient, mainly due to unclear definitions and regulations. In 2002, this system was split into two parts by enacting a new law, the Resource Recycling and Re-use Act (RRRA). However, it then became more complicated and recycling effectiveness was impeded. The causes were mainly the unclear definitions, conflicts about the scope, and issues between the RRRA and the Waste Disposal Act (WDA). This article examines the recycling legislation experience in Taiwan, and proposes two modifications for resolving these problems. The first proposal is merging these two acts into one. The second proposed modification maintains a two-system structure but introduces a new subject, discards, into the law. The subject of discards is further categorized as recyclable resources or waste, which correspond to recycling operations and disposal operations, respectively. The new structures, interfaces, prerequisites, properties, and comparisons are also explained.     

Controlling the Behaviors of Biodegradable/Bioabsorbable Polymers with Cyclodextrins

The cyclic six, seven, and eight-membered oligosaccharides -, -, and -cyclodextrins (CDs) can serve as hosts for a variety of polymer guests to form crystalline inclusion compounds (ICs), wherein the guest polymers are included in the continuous narrow channels (0.5–1.0 nm in diameter) formed by the host CD stacks. Polymers included as guests in CD-ICs are highly extended and segregated from neighboring chains by the walls of the host CD bracelets. As a consequence, when polymer-CD-ICs are treated with solvents for CDs that are non-solvents for the included polymers or with amylase enzymes, the CDs are removed and the guest polymers are coalesced into bulk samples whose structures, morphologies, and even chain conformations are different from those achieved by consolidation from their randomly coiling, entangled solutions and melts. Often these CD-IC coalesced and consequently reorganized polymer samples exhibit properties that are distinct from their normally processed bulk samples. Here we describe the CD-IC processing of several biodegradable/bioabsorbable homopolymers, copolymers, and blends made from poly (L-lactic acid), poly (-caprolactone), and poly (-hydroxybutyrate)s, with special emphasis placed on their improved and controllable properties. For example, the phase segregation and consequent crystallinities of their normally incompatible homopolymer blends and their block copolymers may be controlled and thus improved. In addition, co-inclusion of small molecule guests, such as drugs or anti-bacterials, in their common CD-ICs, and subsequent coalescence, yields well-mixed blends of these biodegradable/bioabsorbable polymers and the small molecule co-guests, which may lead, for example, to the improved delivery of drugs.     

Investigation of the Aerobic Biodegradability of Several Types of Cyclodextrins in a Laboratory-Controlled Composting Test

The biodegradation of several types of cyclodextrins (CDs) under laboratory-controlled composting conditions was investigated. CDs are used in a broad range of applications in food, pharmaceutical, medical, chemical, and textile industries because of their specific chemical characteristics related to their hydrophobic interior and hydrophilic exterior. The three naturally occurring cyclodextrins -CD, -CD, and -CD proved to be completely and readily biodegradable. Chemical modification of these basic compounds can have a major impact on the biodegradation rate and final biodegradation percentage. Fully acetylated -CD and -CD were found to be nonbiodegradable during 45 days of composting. Reducing the degree of acetylation had a positive effect on the biodegradation. Complete biodegradation was obtained for partially acetylated -CD with a degree of substitution (DS) of 7. The methylation (DS = 13) of -CD resulted in an undegradable compound during the 47 days composting, while (2-hydroxy)propyl--CD reached a plateau in biodegradation at a percentage of 20%. The incorporation of the antimicrobial agents imazalil and allyl-isothiocyanate into -CD had no negative impact on biodegradation, which makes these antimicrobial agents/CD complexes suitable for incorporation into biodegradable active packaging.     

Biodegradability: An assessment of commercial polymers according to the Canadian method for anaerobic conditions

The degradation of several biodegradable polymers was measured as a result of exposure to an anaerobic medium. The polymers investigated included materials based upon polylactic acid, polylactone, and poly(hydroxy butyrate/valerate) as well as those incorporating starch-based materials. The degradation was monitored by methane and carbon dioxide evolution. In addition, the physical and chemical changes were noted as a result of exposure. These measurements included changes in mass, dimension, and molecular weight. FTIR, UV-vis, proton, and¹³C NMR spectra were also recorded prior to and after exposure. The results clearly indicated that several biological and chemical degradation processes were occurring with the biodegradable polymers studied.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.Issued as NRCC No. 37549.     

The degradation of gel-spun poly(β-hydroxybutyrate) “wool”

The apparent biodegradability and biocompatibility of the microbially produced polyester, poly(-hydroxybutyrate) (PHB), has been the focus of much research by a number of authors with regard to its potential for use in packaging and medical implantation devices. PHB has recently been produced by gel-spinning into a novel form, with one possible application being as a wound scaffolding device, designed to support and protect a wound against further damage while promoting healing by encouraging cellular growth on and within the device from the wound surface. This new nonwoven form combines a large volume with a low mass, has an appearance similar to that of cotton wool, and has been called wool because of this similarity. The hydrolytic degradation of this wool was investigated in an accelerated model of pH 10.6 and temperature 70°C. It was determined that the PHB wool gradually collapsed during degradation. The surface area-to-volume ratio was concluded to be a primary influencing factor. Degradation was characterized by a reduction in the glass transition temperatures and melting points and a fusion enthalpy peak of maximum crystallinity, (88%), which coincided with the point of matrix collapse.     

The Role Played by Acetyl Group Distribution Patterns in Substituted Starch Toward Enzymatic De-acetylation and Chain Fragmentation

The nature and distribution of the acetylated groups were evaluated by ¹³C-NMR and ¹H-NMR. The starch substrate with a DS of 1.5 comprises only two patterns: -(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose. The starch with a DS of 3.0 also comprises two patterns: 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose and 2,3,6-tri-O-acetyl--(14)-d-glucopyranose; whereas starch (DS = 1.9) contains 4 patterns: 2,3,6-tri-O-acetyl--(14)-d-glucopyranose, 2,3,4,6-tetra-O-acetyl--(14)-d-glucopyranose terminal, 2,6-di-O-acetyl--(14)-d-glucopyranose, and 3,6-di-O-acetyl--(14)-d-glucopyranose. Using esterase from Viscozyme, it has been possible to hydrolyze up to 7% of the DS 3.0 starch. An -amylase (Fungamyl 800) was then added to these acetylesterases. With a 2.4 FAU/mL fraction of -amylase and 2.4 U/mL from the Viscozyme's acetylesterase, 28% of the acetylated end groups were hydrolyzed for the starch substrates with DS 3.0. Moreover, a synergic action between -amylase and acetylesterase was noticed, allowing fragmentation of 32% for DS 1.5, 30% for DS 1.9, and 11% for DS 3.0.     

Synthesis and environmental degradation of polyesters based on poly (ε-caprolactone)

Poly (-caprolactone) (PCL), poly (-valerolactone) (PVL), poly (-caprolactone-co--valerolactone) [P(CL-co-VL)], and poly (-caprolactone-co-ethylene oxide-co--caprolactone) (PCL-PEO-PCL) were synthesized by ring-opening and diol-initiated polymerization of -caprolactone and -valerolactone. The degradation of the samples by chemical hydrolysis and in a soil burial test was evaluated. It was found that PCL, PVL, and P(CL-co-VL) degrade mainly enzymatically. The rate of degradation depends on their molecular weight, chemical structure, composition, and morphology. PCL-PEO-PCL block copolymers exhibit a repelling effect to the microorganisms in the soil, which depends on the molecular weight and relative amount of PEO block in the copolymer.     

Effects of Lime and Ash Treatments on DOC Fractions and Low Molecular Weight Organic Acids in Soil Solutions of Acidified Podzolic Soils

Dissolved organic carbon (DOC) fractions and different low molecular weight organic acids (LMWOAs) were determined in soil solutions from two lime or ash treated Norway spruce sites in the south of Sweden. At Hasslöv, 3.45 t ha^-1 or 8.75 t ha^-1 dolomite were applied 15 years before sampling. Horröd was treated with 4.28 t ha^-1 ash and 3.25 t ha^-1 dolomite and sampled four years later. Propionate (7–268 M) and malonate (2–34 M) were the LMWOAsfound in the highest concentrations at Hasslöv. Two other LMWOAs dominated at Horröd, namely citrate (18–64 M)and fumarate (5–31 M). The differences in concentration of most of the determined LMWOAs at Hasslöv were significantly increased due to treatment. The LMWOAs comprised between 1.1–6.3% of the DOC at Hasslöv and 4.5–17.6% at Horröd. At Hasslöv normally 3–10% of the total acidity (TA) was due to LMWOAs and the average specific buffer capacity was 74 ± 22 mmol mol^-1C.The total DOC concentration in the mor layer solution was 16 mM for the dolomite treated plots compared to 10 mM at the untreated plot. A major part of the increase in DOC at the treated plots apparently had a hydrophobic character and was of high molecular weight corresponding to 3–10 kDa. The concentration of DOC < 1 kDa in the control and treated plots was similar.     

Methane generation from corncobs treated with xylanolytic consortia

Consortia were developed for the treatment of corncobs for use as a feedstock in a biogas fermentor. The treatment of corncobs with xylanolytic consortia enhanced the production of methane and biogas. All five consortia developed produced the maximum biogas and methane at a 6% loading rate and 20 days hydraulic retention time (HRT). The maximum biogas yield of 0.59m³/kg volatile solids (VS) with a methane content of 62% was produced with the KK-10 consortium. This was apparently due to a maximum hemicellulose degradation of 88%.