Carbon–carbon asymmetric aqueous capacitor by pseudocapacitive positive and stable negative electrodes

An asymmetric aqueous capacitor was constructed by employing zeolite-templated carbon (ZTC) as a pseudocapacitive positive electrode and KOH-activated carbon as a stable negative electrode. The asymmetric capacitor can be operated with the working voltage of 1.4 V, and exhibits an energy density that is comparable to those of conventional capacitors utilizing organic electrolytes, thanks to the large pseudocapacitance of ZTC. Despite relatively thick electrode (0.2 mm) configuration, the asymmetric capacitor could be well operated under a current density of 500 mA g −1.

Design of Activated Carbon/Activated Carbon Asymmetric Capacitors

Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors are optimized using the capacitance and the potential stability limits of the electrodes, with the reliability of the design largely depending on the accuracy and the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

Gas Storage Scale-up at Room Temperature on High Density Carbon Materials

In relation to the current interest on gas storage demand for environmental applications (e.g., gas transportation, and carbon dioxide capture) and for energy purposes (e.g., methane and hydrogen), high pressure adsorption (physisorption) on highly porous sorbents has become an attractive option. Considering that for high pressure adsorption, the sorbent requires both, high porosity and high density, the present paper investigates gas storage enhancement on selected carbon adsorbents, both on a gravimetric and on a volumetric basis. Results on carbon dioxide, methane, and hydrogen adsorption at room temperature (i.e., supercritical and subcritical gases) are reported. From the obtained results, the importance of both parameters (porosity and density) of the adsorbents is confirmed. Hence, the densest of the different carbon materials used is selected to study a scale-up gas storage system, with a 2.5 l cylinder tank containing 2.64 kg of adsorbent. The scale-up results are in agreement with the laboratory scale ones and highlight the importance of the adsorbent density for volumetric storage performances, reaching, at 20 bar and at RT, 376 g l-1, 104 g l-1, and 2.4 g l-1 for CO2, CH4,and H2, respectively.

Refinery Nonconventional Feedstocks: Influence of the Coprocessing of Vacuum Gas Oil and Low Density Polyethylene in Fluid Catalytic Cracking Unit on Full Range Gasoline Composition

Gasoline coming from refinery fluid catalytic cracking (FCC) unit is a major contributor to the total commercial grade gasoline pool. The contents of the FCC gasoline are primarily paraffins, naphthenes, olefins, aromatics, and undesirables such as sulfur and sulfur containing compounds in low quantities. The proportions of these components in the FCC gasoline invariable determine its quality as well as the performance of the associated downstream units. The increasing demand for cleaner and lighter fuels significantly influences the need not only for novel processing technologies but also for alternative refinery and petrochemical feedstocks. Current and future clean gasoline requirements include increased isoparaffins contents, reduced olefin contents, reduced aromatics, reduced benzene, and reduced sulfur contents. The present study is aimed at investigating the effect of processing an unconventional refinery feedstock, composed of blend of vacuum gas oil (VGO) and low density polyethylene (LDPE) on FCC full range gasoline yields and compositional spectrum including its paraffins, isoparaffins, olefins, napthenes, and aromatics contents distribution within a range of operating variables of temperature (500–700 °C) and catalyst-feed oil ratio (CFR 5–10) using spent equilibrium FCC Y-zeolite based catalyst in a FCC pilot plant operated at the University of Alicante’s Research Institute of Chemical Process Engineering (RICPE). The coprocessing of the oil-polymer blend led to the production of gasoline with very similar yields and compositions as those obtained from the base oil, albeit, in some cases, the contribution of the feed polymer content as well as the processing variables on the gasoline compositional spectrum were appreciated. Carbon content analysis showed a higher fraction of the C9–C12 compounds at all catalyst rates employed and for both feedstocks. The gasoline’s paraffinicity, olefinicity, and degrees of branching of the paraffins and olefins were also affected in various degrees by the scale of operating severity. In the majority of the cases, the gasoline aromatics tended toward the decrease as the reactor temperature was increased. While the paraffins and iso-paraffins gasoline contents were relatively stable at around 5 % wt, the olefin contents on the other hand generally increased with increase in the FCC reactor temperature.

Conversion of low density polyethylene into fuel through co-processing with vacuum gas oil in a fluid catalytic cracking riser reactor

In this work, mixtures of vacuum gas oil and low density polyethylene, a major component of common industrial and consumer household plastics, were pyrolytically co-processed in a fluid catalytic cracking (FCC) riser reactor as a viable alternative for the energy and petrochemical revalorisation of plastic wastes into valuable petrochemical feedstocks and fuel within an existing industrial technology. Using equilibrium FCC catalyst, the oil–polymer blends were catalytically cracked at different processing conditions of temperatures between 773 K and 973 K and catalyst feed ratios of 5:1, 7:1 and 10:1. The influence of each of these processing parameters on the cracking gas and liquid yield patterns were studied and presented. Further analysed and presented are the different compositional distributions of the obtained liquids and gaseous products. The analysis of the results obtained revealed that with very little modifications to existing process superstructure, yields and compositional distributions of products from the fluid catalytic cracking of the oil–polymer blend in many cases were very similar to those of the processed oil feedstock, bringing to manifest the viability of the feedstock co-processing without significant detriments to FCC product yields and quality.