Solar pyrolysis of waste rubber tires using photoactive catalysts.

The solar pyrolysis of waste tire rubber was investigated with the application of heterogeneous photocatalysts including TiO2, Pd/TiO2, Pt/TiO2, Pd-Pt/TiO2, and Bi2O3/SiO2/TiO2. Experiments were performed at temperatures ranging between 550 and 570 °C under solar irradiations of 950-1050 W/m2. The gas yield from non-catalytic solar pyrolysis was at 20% while the use of TiO2 catalyst increased the gas yield to 27%. Doping of TiO2 with noble metals and Bi2O3/SiO2 metal oxides enhanced further the cracking ability of the catalyst. Bi2O3/SiO2/TiO2 gave a 32% gas yield. The highest gas yields of 40% and 41% were achieved over Pd-Pt/TiO2 and Pd/TiO2 catalysts, respectively. Catalyst characterization by BET, SEM, EDX and XRD showed the role of metal doping in altering the morphology of TiO2, resulting in nanocrystallites, larger pore volume and higher surface area. Both, Pd and Bi influenced the photocatalytic properties of TiO2 improving cracking activity during pyrolysis of waste rubber.

Surface Chemistry of Electronic Cigarette Electrical Heating Coils: Effects of Metal Type on Propylene Glycol Thermal Decomposition.

INTRODUCTION: Carbonyls, a class of compounds strongly linked to pulmonary disease in smokers, are probably the most reported non-nicotine toxicants found aerosols. Reported emissions vary from negligible quantities to those far exceeding combustible cigarettes. Observations of high emissions are commonly attributed to "dry puffing", whereby the ECIG heating filament runs dry of liquid and reaches temperatures that induce thermal degradation of the ECIG vapor components at the filament's metal surface. Using a pyrolysis flow reactor, in this study we examined the potential role of surface chemistry in the formation of carbonyl compounds in ECIGs, and whether the different commercially available filament materials could potentially impact their toxicant emissions through catalysis. This information could inform nascent efforts to regulate the design of ECIGs for public health ends. METHODS: Nitrogen or air saturated with propylene glycol vapor was drawn through a temperature and residence time controlled tubular quartz pyrolysis flow reactor in which nichrome, Kanthal, or stainless steel ECIG heating filament wires were inserted. A control condition with no inserted wire was also included. Concentrations of carbonyl products at the reactor outlet were measured as a function of temperature, heating filament wire material, and carrier gas composition (N2 vs air). Carbonyls were sampled using DNPH cartridges and analyzed by HPLC. RESULTS: ECIG heating filament wires were found to have a strong catalytic effect. Carbonyl formation initiated at temperatures lower than 250°C in the presence of the metallic wires, compared to 460°C without them. Carbonyl formation was found to be a function of the material of construction, and whether the wire was new or aged. New nichrome wires were the least reactive, but when aged they exhibited the highest reactivity. Carbonyls were formed via dehydration or oxidation reactions of PG. CONCLUSIONS: Carbonyl formation chemistry is catalyzed by commonly used ECIG heating filament materials, at temperatures that are well below those expected during "dry puffing". The variability in the distribution and yield of carbonyl compounds across ECIG filament materials suggests that this heretofore unaccounted variable may partially explain the wide ranges reported in the literature to date. More importantly, it suggests that ECIG construction materials may be an important variable for regulations designed to protect public health.

Pyrolysis of waste tires: A modeling and parameter estimation study using Aspen Plus®.

This paper presents a simulation flowsheet model of a waste tire pyrolysis process with feed capacity of 150kg/h. A kinetic rate-based reaction model is formulated in a form implementable in the simulation package Aspen Plus, giving the flowsheet model the capability to predict more than 110 tire pyrolysis products as reported in experiments by Laresgoiti et al. (2004) and Williams (2013) for the oil and gas products respectively. The simulation model is successfully validated in two stages: firstly against experimental data from Olazar et al. (2008) by comparing the mass fractions for the oil products (gas, liquids (non-aromatics), aromatics, and tar) at temperatures of 425, 500, 550 and 610°C, and secondly against experimental results of main hydrocarbon products (C7 to C15) obtained by Laresgoiti et al. (2004) at temperatures of 400, 500, 600, and 700°C. The model was then used to analyze the effect of pyrolysis process temperature and showed that increased temperatures led to chain fractions from C10 and higher to decrease while smaller chains increased; this is attributed to the extensive cracking of the larger hydrocarbon chains at higher temperatures. The utility of the flowsheet model was highlighted through an energy analysis that targeted power efficiency of the process determined through production profiles of gasoline and diesel at various temperatures. This shows, through the summation of the net power gain from the plant for gasoline plus diesel that the maximum net power lies at the lower temperatures corresponding to minimum production of gasoline and maximum production of diesel. This simulation model can thus serve as a robust tool to respond to market conditions that dictate fuel demand and prices while at the same time identifying optimum process conditions (e.g. temperature) driven by process economics.