8 research outputs found
Composite zeolite beta catalysts for catalytic hydrocracking of plastic waste to liquid fuels
Abstract The conversion of model waste plastic mixture into high-value liquid product was studied in the presence of hydrogen and composites of zeolite beta catalysts. For the sake of comparison, the conversion of actual waste plastic mixture and high-density polyethylene was also carried out. The composite zeolite beta catalysts were synthesized using a range of silica-to-alumina ratios, alkali concentrations, and hydrothermal treatment times. SEM, EDX, XRD, N2-BET, FTIR, and py-FTIR were used for the characterization of the catalysts. The catalytic experiments were conducted in a 500 ml stirred batch reactor at 20 bar initial cold H2 pressure and the temperature of the reaction was varied between 360 and 400 °C. The two composite catalysts, BC27 and BC48, prepared without alkali pretreatment were found to be the most suitable catalysts. With BC27 and BC48 at 400 °C, 93.0 wt% conversion was obtained with actual plastic mixture and the liquid yield exceeded 68.0 wt%. Experiments with the regenerated catalysts showed their performance comparable to the fresh catalysts
Dry Reforming of Methane with Mesoporous Ni/ZrO2 Catalyst
Dry reforming of methane has exhibited significant environmental benefits as it utilizes two major greenhouse gases (CO2 and CH4) to produce synthesis gas, a major building block for hydrocarbons. This process has gained industrial attention as catalyst deactivation due to coke deposition being a major hindrance. The present study focuses on the dry reforming of methane over Ni-supported mesoporous zirconia support. Ni metal was loaded over in-house synthesized mesoporous zirconia within the 0–15 wt% range using the wet impregnation method. The physicochemical properties of the synthesized catalysts were studied using various characterization techniques, namely, XRD, SEM, FTIR, TGA, and N2 adsorption-desorption techniques. The activity of all the catalysts was evaluated at 750°C and gas hourly space velocity (GHSV) of 72000 ml/h/gcat for 9 hours (540 min). The deactivation factor indicating a loss in conversion with time is reported for each catalyst. 10 wt% Ni/ZrO2 showed the highest feed conversion of about 68.8% for methane and 70.2% for carbon dioxide and the highest stability (15.1% deactivation factor and 21% weight loss) for dry reforming of methane to synthesis gas
Simulation Study to Investigate the Effects of Operational Conditions on Methylcyclohexane Dehydrogenation for Hydrogen Production
In the recent era, hydrogen has gained immense consideration as a clean-energy carrier. Its storage is, however, still the main hurdle in the implementation of a hydrogen-based clean economy. Liquid organic hydrogen carriers (LOHCs) are a potential option for hydrogen storage in ambient conditions, and can contribute to the clean-fuel concept in the future. In the present work, a parametric and simulation study was carried out for the storage and release of hydrogen for the methylcyclohexane toluene system. In particular, the methylcyclohexane dehydrogenation reaction is investigated over six potential catalysts for the temperature range of 300–450 °C and a pressure range of 1–3 bar to select the best catalyst under optimum operating conditions. Moreover, the effects of hydrogen addition in the feed mixture, and byproduct yield, are also studied as functions of operating conditions. The best catalyst selected for the process is 1 wt. % Pt/γ-Al2O3. The optimum operating conditions selected for the dehydrogenation process are 360 °C and 1.8 bar. Hydrogen addition in the feed reduces the percentage of methylcyclohexane conversion but is required to enhance the catalyst’s stability. Aspen HYSYS v. 9.0 (AspenTech, Lahore, Pakistan) has been used to carry out the simulation study
Experimental Study of Solubility of Water in Liquid Organic Hydrogen Carriers
Liquid
organic hydrogen carriers (LOHC) are one of the potential
candidates to assuage the problem of hydrogen storage. Prior to the
storage step, hydrogen produced from electrolysis can contain a significant
amount of water, which can lead to the formation of an undesired two-phase
system in the LOHC storage tanks. In this work, solubility of water
in potential liquid organic hydrogen carriers (toluene, dibenzyltoluene,
and <i>N</i>-ethylcarbazol) in their hydrogenated and dehydrogenated
forms as well as mixtures of these forms have been measured within
the temperature range of (293 to 343) K. The solubility of water in
LOHC materials is found to increase with temperature. This effect
has been correlated using the Tsonopoulos and Wilson equation. Furthermore,
various thermodynamic parameters such as Gibbs free energy, enthalpy,
and entropy of dissolution were estimated based on the solubility
data using the van’t Hoff equation
Measurement of Hydrogen Solubility in Potential Liquid Organic Hydrogen Carriers
Liquid organic hydrogen carriers (LOHC) are potential compounds that can facilitate chemical energy storage and hydrogen logistics using reversible hydrogenation. For the process development, the physical solubility of hydrogen in potential LOHCs is required. In this work, solubility of hydrogen in the potential LOHC systems toluene/methylcyclohexane, N-ethylcarbazole/perhydro-N-ethylcarbazole, and dibenzyltoluene/perhydrodibenzyltoluene was measured using the static isochoric saturation method. The data were measured at low pressures up to 10 bar within the temperature range of (293 to 373) K. Hydrogen solubility in hydrogenated forms of the LOHCs was found to be higher compared to the dehydrogenated forms. Solubility in all substances increased with increasing temperature within the whole temperature range under consideration. The temperature dependency of the Henry coefficient of hydrogen in the solvents was correlated using the Benson and Krause correlation
Experimental assessment of the degree of hydrogen loading for the dibenzyl toluene based LOHC system
Liquid Organic Hydrogen Carriers allow for storing hydrogen with high density at ambient conditions. In the LOHC hydrogen storage process, a significant number of different partially and fully hydrogenated species occur on the reaction pathway from the hydrogen-lean to the hydrogen-rich form of the LOHC system. In order to access the amount of hydrogen stored in the carrier system, ways of measuring the degree of hydrogenation are required. A number of physical properties can be correlated with the degree of hydrogenation. However, there are different mixtures of hydrogenated, partly hydrogenated and dehydrogenated derivatives which result in an identical degree of hydrogenation but different properties. In this contribution we report on attempts to correlate physico-chemical properties and spectroscopic data to the degree of hydrogenation of the dibenzyl toluene system by using density, viscosity, refractive index, UV–VIS and Raman spectroscopy measurements. The most reliable correlations were found for density or refractive index