Rabya Aslam

Bio: Rabya Aslam is an academic researcher from University of the Punjab. The author has contributed to research in topics: Methylcyclohexane & Hydrogen. The author has an hindex of 10, co-authored 22 publications receiving 255 citations. Previous affiliations of Rabya Aslam include University of Erlangen-Nuremberg.

Hydrogenation of the liquid organic hydrogen carrier compound dibenzyltoluene – reaction pathway determination by 1H NMR spectroscopy

Abstract: The catalytic hydrogenation of the LOHC compound dibenzyltoluene (H0-DBT) was investigated by 1H NMR spectroscopy in order to elucidate the reaction pathway of its charging process with hydrogen in the context of future hydrogen storage applications. Five different reaction pathways during H0-DBT hydrogenation were considered including middle-ring preference (middle-side-side, MSS), side-middle-side order of hydrogenation (SMS), side-ring preference (SSM), simultaneous hydrogenation of all three rings without intermediate formation and statistical hydrogenation without any ring preference. Detailed analysis of the 1H NMR spectra of the H0-DBT hydrogenation over time revealed that the reaction proceeds with a very high preference for the SSM order at temperatures between 120 °C and 200 °C and 50 bar in the presence of a Ru/Al2O3-catalyst. HPLC analysis supported this interpretation by confirming an accumulation of H12-DBT species prior to full hydrogenation to H18-DBT with middle ring hydrogenation as the final step.

Measurement of Hydrogen Solubility in Potential Liquid Organic Hydrogen Carriers

Abstract: 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.

Thermophysical Studies of Dibenzyltoluene and Its Partially and Fully Hydrogenated Derivatives

Abstract: Liquid organic hydrogen carriers (LOHC) are an interesting and promising option for the storage and transport of hydrogen with reasonable energy density via a reversible hydrogenation reaction. The...

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.

Liquid Organic Hydrogen Carriers (LOHCs): Toward a Hydrogen-free Hydrogen Economy

Abstract: ConspectusThe need to drastically reduce CO2 emissions will lead to the transformation of our current, carbon-based energy system to a more sustainable, renewable-based one. In this process, hydrogen will gain increasing importance as secondary energy vector. Energy storage requirements on the TWh scale (to bridge extended times of low wind and sun harvest) and global logistics of renewable energy equivalents will create additional driving forces toward a future hydrogen economy. However, the nature of hydrogen requires dedicated infrastructures, and this has prevented so far the introduction of elemental hydrogen into the energy sector to a large extent. Recent scientific and technological progress in handling hydrogen in chemically bound form as liquid organic hydrogen carrier (LOHC) supports the technological vision that a future hydrogen economy may work without handling large amounts of elemental hydrogen. LOHC systems are composed of pairs of hydrogen-lean and hydrogen-rich organic compounds that st...

Hydrogen Storage for Mobility: A Review

Abstract: Numerous reviews on hydrogen storage have previously been published. However, most of these reviews deal either exclusively with storage materials or the global hydrogen economy. This paper presents a review of hydrogen storage systems that are relevant for mobility applications. The ideal storage medium should allow high volumetric and gravimetric energy densities, quick uptake and release of fuel, operation at room temperatures and atmospheric pressure, safe use, and balanced cost-effectiveness. All current hydrogen storage technologies have significant drawbacks, including complex thermal management systems, boil-off, poor efficiency, expensive catalysts, stability issues, slow response rates, high operating pressures, low energy densities, and risks of violent and uncontrolled spontaneous reactions. While not perfect, the current leading industry standard of compressed hydrogen offers a functional solution and demonstrates a storage option for mobility compared to other technologies.

Liquid organic hydrogen carriers (LOHCs) – techno-economic analysis of LOHCs in a defined process chain

Abstract: Long-distance transport and long-term storage of hydrogen can be realized with Liquid Organic Hydrogen Carriers (LOHC) based on a two-step cycle: (1) loading of hydrogen (hydrogenation) into the LOHC molecule (i.e., hydrogen is covalently bound to the LOHC) and (2) unloading of hydrogen (dehydrogenation) after transport and storage. Since the (optimal) LOHC is liquid at ambient conditions and shows similar properties to crude oil based liquids (e.g. diesel, and gasoline), handling and storage is realized by well-known processes; thus stepwise adaptation of the existing crude oil based infrastructure is basically possible. Against this background, a defined process chain for intercontinental ship transport of hydrogen (5000 km) is simulated with various LOHCs. The respective results are evaluated and assessed related to their technological and economic performance. Additionally, they are compared to a pipeline-based provision chain based on compressed hydrogen (CGH2). Among others, the results show that methanol is the cheapest LOHC option for storage and transportation followed by dibenzyltoluene and toluene. For a storage time of 60 days they show economic advantages compared to compressed hydrogen (CGH2) under the defined assumptions; thus these LOHC options are especially advantageous for long-term storage/long distance transport applications. The energetic efficiency of the systems mainly depends on the source of the dehydrogenation heat. Two options, dehydrogenation driven by hydrogen burning vs. dehydrogenation driven by waste heat, have been evaluated in this study. Systems that run on waste heat perform much better in terms of efficiency. Overall, LOHCs can provide technologically efficient and economic promising storage and transport within a sustainable hydrogen economy.