Dae-Hyun Shin

Investigation of catalytic degradation of high-density polyethylene by hydrocarbon group type analysis

Catalytic degradation of waste high-density polyethylene (HDPE) to hydrocarbons by ZSM-5, zeolite-Y, mordenite and amorphous silica–alumina were carried out in a batch reactor to investigate the cracking efficiency of catalysts by analyzing the oily products including paraffins, olefins, naphthenes and aromatics with gas chromatography/mass spectrometry (GC/MS). Catalytic degradation of HDPE with zeolite-Y, mordenite and amorphous silica–alumina yielded 71–82 wt.% oil fraction, which mostly consisted of C6–C12 hydrocarbons, whereas ZSM-5 yielded much lower 35% oil fraction, which mostly consisted of C6–C12 hydrocarbons. Both all zeolites and silica–alumina increased olefin content in oil products, and ZSM-5 and zeolite-Y particularly enhanced the formation of aromatics and branched hydrocarbons. ZSM-5 among zeolites showed the greatest catalytic activity on cracking waste HDPE to light hydrocarbons, whereas mordenite produced the greatest amount of coke. Amorphous silica–alumina also showed a great activity on cracking HDPE to lighter olefins in high yield, but no activity on aromatic formation.

Catalytic Degradation of Waste Polyolefinic Polymers using Spent FCC Catalyst with Various Experimental Variables

Liquid-phase catalytic degradation of waste polyolefinic polymers (HDPE, LDPE, PP) over spent fluid catalytic cracking (FCC) catalyst was carried out at atmospheric pressure with a stirred semi-batch operation. The effect of experimental variables, such as catalyst amount, reaction temperature, plastic types and weight ratio of mixed plastic on the yield and accumulative amount distribution of liquid product for catalytic degradation was investigated. The initial rate of catalytic degradation of waste HDPE was linearly increased with catalyst amount (4-12 wt%), while that was exponentially increased with reaction temperature (350-430 ‡C). Spent FCC catalyst in the liquid-phase catalytic degradation of polymer was not deactivated fast. The product distribution from catalytic degradation using spent FCC catalyst strongly depended on the plastic type. The catalytic degradation of mixed plastic (HDPE: LDPE: PP: PS=3: 2: 3: 1) showed lower degradation temperature by about 20 ‡C than that of pure HDPE.

Thermal and Catalytic Degradation of Waste High-density Polyethylene (HDPE) Using Spent FCC Catalyst

Thermal and catalytic degradation using spent fluid catalytic cracking (FCC) catalyst of waste high-density polyethylene (HDPE) at 430 °C into fuel oil were carried out with a stirred semi-batch operation. The product yield and the recovery amount, molecular weight distribution and paraffin, olefin, naphthene and aromatic (PONA) distribution of liquid product by catalytic degradation using spent FCC catalyst were compared with those by thermal degradation. The catalytic degradation had lower degradation temperature, faster liquid product rate and more olefin products as well as shorter molecular weight distributions of gasoline range in the liquid product than thermal degradation. These results confirmed that the catalytic degradation using spent FCC catalyst could be a better alternative method to solve a major environmental problem of waste plastics.

Effect of support for alcohol-hydrocarbon synthesis from syngas in Cu-based catalyst

Effects of a Cu-based catalyst on the catalytic performance in alcohol-hydrocarbon synthesis from syngas have been investigated, using various supports. Under the different porosities of three supports (zinc oxide, activation carbon, and titanium dioxide), whereas Cu/ZnO produces one liquid phase of major mixed alcohols, Cu/AC and Cu/TiO2 create two phases, alcohol (∼75%) and hydrocarbon (∼25%). X-ray diffraction shows that CuO impregnated on supports undergoes a complete reduction of metallic copper Cu0, which is the real active phase in the catalytic process. The Cu/TiO2 catalyst showed the highest ethanol composition in a mixed alcohol phase under GHSV 18,000 h−1, 30 bar, and 300 °C.

A comparative study of liquid product on non-catalytic and catalytic degradation of waste plastics using spent FCC catalyst

Non-catalytic and catalytic degradation of waste plastics (high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS)) using spent fluid catalytic cracking (FCC) catalyst into liquid product were comparatively studied with a stirred semi-batch reactor at 400 ‡C, under nitrogen stream. Liquid product characteristics were described by cumulative distribution as a function of lapse time of reaction, paraffin, olefin, naphthene and aromatic (PONA) composition, and also carbon number distribution on plastic type of reactant. For degradation of waste PE with relatively high degradation temperature, the effect of adding spent FCC catalyst greatly appeared on cumulative distribution of liquid product with a reaction lapse time, whereas those for waste PP and PS with low degradation temperature showed a similar trend in both non-catalytic and catalytic degradation at 400 ‡C. In PONA and carbon number distribution of liquid product, the characteristics of waste PS that was mainly degraded by end chain scission mechanism were not much altered in presence of spent FCC catalyst. However, waste polyolefinic polymer that was degraded by a random chain scission mechanism significantly differed on PONA and carbon number distribution of liquid product with or without spent FCC catalyst. The addition of spent FCC catalyst in degradation of polyolefinic polymer, which economically has a benefit in utilization of waste catalyst, significantly improved the light olefin product by its high cracking ability and also the aromatic product by cyclization of olefin as shape selectivity in micropore of catalyst.

Economic feasibility of ethanol production from biomass and waste resources via catalytic reaction

An economic evaluation of ethanol (EtOH) production from a thermo-chemical process derived from biomass/waste feedstocks was conducted. The influence of feed amounts, catalytic conversions, and EtOH selling prices was examined as these are the major variables for the economic evaluation of biomass/wastes conversion to EtOH. Among the three feedstock systems of biomass, high-moisture municipal solid waste (MSW), and plastic waste, the plastic waste has far better economic feasibility, with a payback period of 2–5 years at maximum CO conversion (40%) from syngas to ethanol, due to its higher heating value in comparison with biomass and high-moisture MSW. The heating value of the feedstock is a key factor in determining the overall economic efficiency in a thermo-chemical EtOH production system. Furthermore, enhancement of the CO conversion (related to catalytic activity) from syngas to EtOH using a low cost catalyst is necessary to retain economic efficiency because the CO conversion and cost consideration of catalyst are crucial factors to reduce the payback period.

Thermal degradation of nitrogen-containing polymers, acrylonitrile-butadiene-styrene and styrene-acrylonitrile

Thermal degradation of nitrogen (N)-containing recycled plastics (styrene-acrylonitrile (SAN), acrylonitrilebutadiene-styrene (ABS)) was carried out in a stirred-batch reactor at 300–400 ‡C under nitrogen stream. The degradation oil began to be generated over 300 ‡C. Recycled SAN plastic was converted to oil with 91.3 wt% yield at 380 ‡C, while only 70.9 wt% of recycled ABS plastics was converted to oil at the same temperature and both oils contained about the same 3.7 wt% nitrogen as an elemental basis. Rate of oil formation from the thermal degradation of SAN was much higher than that of ABS, but showed a similar degradation pattern in terms of chemical composition. In oil products, aromatic contents obtained at 360 ‡C were 70 wt% for SAN and 79 wt% for ABS, respectively, and decreased to 59 wt% and 57 wt% at 380 ‡C with increasing degradation temperature. Dominant product of both degradation oils was styrene, and the following was ethylbenzene for ABS, but none in case of SAN. Both oils contained the N-containing plastic additives that give rise to a confusion for the identification of authentic N-containing degradation products.