Yasser F Alwahedi

Khalifa University | KU · Department of Chemical Engineering

Metal–organic frameworks (MOFs) have emerged as promising candidates for CO2 adsorption due to their ultrahigh-specific surface area and highly tunable pore-surface properties. However, their large-scale application is hindered by processing issues associated with their microcrystalline powder nature, such as dustiness, pressure drop, and poor mass...

Global water scarcity is leading to increasingly tense competition across populations. In order to complement the largely fast‐depleting fresh water sources and mitigate the challenges generated by brine discharge from desalination, atmospheric water harvesting (AWH) has emerged to support long‐term water supply. This work presents a novel alginate...

Water is readily available nearly anywhere as vapor. Thus, atmospheric water harvesting (AWH) technologies are seen as a promising solution to support sustainable water production. This work reports a novel semi-interpenetrating network, which integrates poly(pyrrole) doped with a hygroscopic salt and 2D graphene-based nanosheets optimally assemble...

Freshwater resources are being heavily depleted and not replenished at the same high rate, thus, atmospheric water vapor harvesting has earned growing interest. Development of high-performing desiccant or adsorbent materials offering high sorption capacity and selectivity as well as regeneration capability in atmospheric conditions is crucial to ta...

Hydrogen sulfide (H2S) removal by adsorption from gas streams is crucial to prevent the environmental and industrial damage it causes. Among the nanostructures considered excellent candidates as sorbents, porous carbon has been studied extensively over the last years. In the present work we present a synthetic procedure for three high potential sor...

For compact electronic devices, high-pressure drops that characterize microchannel heat sinks (MCHS) is an issue that needs to be resolved to reduce the size of heat-removing systems. In this regard, supercritical carbon dioxide (sCO2) can be of great value due to its favorable thermophysical properties near the critical point. Thus, the potential...

The development of efficient zeolite-based adsorbents with high water uptake capacity is an essential requirement for water adsorption and moisture removal technologies. In the present study, zeolite-Y samples with interconnected hierarchical micro-mesoporous network were synthesized by employing a bifunctional cationic polymer (namely, polydiallyd...

Structural and morphological control of crystalline nanoparticles is crucial in the field of heterogeneous catalysis and the development of “reaction specific” catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired cry...

Optimizing catalysts for the hydrodesulfurization (HDS) is a crucial step toward conforming SO2 with the environmental requirements concerning emissions. Nickel phosphides have been SO2 reported as efficient catalysts in HDS reaction. However, how HDS reaction proceeds on nickel phosphides is not well understood. On this context, the present work f...

Metal substitution in aluminophosphates is known to induce unique structural and surface characteristics that can tune catalytic performance. Si, Co, Fe and Mg substituted AlPO4-5 (MeAPO-5) catalysts were hydrothermally prepared, characterized, and evaluated for ethanol - acetic acid esterification. Textural evaluation revealed that the Co and Si a...

The adsorption energy and electronic properties of sulfur dioxide (SO2) adsorbed on different low-Miller index cobalt phosphide (CoP) surfaces were examined using density functional theory (DFT). Different surface atomic terminations and initial molecular orientations were systematically investigated in detail to determine the most active and stabl...

Metal substitution in aluminophosphates is known to induce unique structural and surface characteristics that can tune catalytic performance. Si, Co, Fe and Mg substituted AlPO4-5 (MeAPO-5) catalysts were hydrothermally prepared, characterized, and evaluated for ethanol - acetic acid esterification. Textural evaluation revealed that the Co and Si a...

Structural and morphological control of crystalline nanoparticles is crucial in the field of heterogeneous catalysis and the development of “reaction specific” catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired cry...

Adjusting the synthetic route to control the shape, composition, and crystal structure of nanostructured topological insulators (TIs) is a challenge in the realization of TI systems with specific functionalities. Here, we report probing the multiphasic evolution of Bi2Te3 nanoplatelets primarily using microscopic, elemental, and crystallographic me...

Aluminophosphate, AlPO4-5, an AFI zeotype framework consisting of one-dimensional parallel micropores, and metal-substituted AlPO4-5 were prepared and studied for CO2 adsorption. Preparation of AlPO4-5 by using different activation methods (calcination and pyrolysis), incorporation of different metals/ions (Fe, Mg, Co, and Si) into the framework us...

In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ∼400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrosta...

This work aims at elucidating the most active modes of copper incorporation towards H2S adsorption. Various synthesis methodologies were followed, notably, incorporation via isomorphic substitution, liquid ion exchange (LIE), vapor phase ion exchange (VIE), and nanoparticles inclusion during hydrothermal synthesis, for the introduction of copper in...

In this work, we present a facile methodology for catalysts synthesis which allows for achieving active component loadings up to 82 w.t.% while controlling the size (2 nm–20 nm), morphology and phase. The active component nanoparticles are synthesized to the desired size, shape and morphology in an organic environment and then are transferred to an...

Metal oxides exhibit highest adsorption capacities towards H2S but are challenged by lack of regenerability due to sulfide layer formation during adsorption, sulfate phase formation during regeneration, sintering, spalling, and sublimation. Protection strategies such as supporting the metal oxide may mitigate such problems but comes at the expense...

In the present study, a facile and one step approach has been developed for the synthesis of hierarchical porous zeolite-Y using bifunctional cationic polymer, polydiallyldimethyl ammonium chloride (PDDA) as a mesopore directing template. The effects of various synthesis parameters such as hydrothermal reaction temperature, time, amount of PDDA and...

Detecting the metallic Dirac electronic states on the surface of Topological Insulators (TIs) is critical for the study of important surface quantum properties (SQPs), such as Majorana zero modes, where simultaneous probing of the bulk and edge electron states is required. However, there is a particular shortage of experimental methods, showing at...

Objective This study aims at high-fidelity modeling and mechanistic optimization of gas dehydration and NGL (Natural Gas Liquids) systems of a commercial natural gas plant based in Abu Dhabi, UAE. Scope of the work includes development of models, validation of models with plant data, optimization analysis and real-time validation at the plant site....

Isomorphic substitution of zeolite and zeotype materials can affect significantly their application performance. The work presented herein assesses the impact of cobalt and silicon substitution at low and high H2O/Al2O3 of the reaction mixture by a combination of experimental and density functional theory (DFT) calculations. The presence of cobalt...

Detection of the metallic Dirac electronic states on the surface of Topological Insulators (TIs) is a tribune for a small number of experimental techniques the most prominent of which is Angle Resolved Photoemission Spectroscopy. However, there is no experimental method showing at atomic scale resolution how the Dirac electrons extend inside TI sys...

Zeolite-Y is one of the preferred micro-sized zeolite commonly used as a catalyst and for adsorption and separation. The size and shape of zeolite crystals have great influence on their properties therefore the synthesis of nano-size zeolite-Y has received much attention with straightforward methodology. In the present study, nano-sized zeolite-Y c...

This paper aims at modeling and optimizing a Middle East-based commercial natural gas liquid (NGL) recovery and fractionation plant, using a predictive process simulator. NGL units are known to be highly energy-intensive as steam-based heating and refrigeration-based cryogenic cooling are critical requirements for their operation. Indeed, these uni...

This paper explains the process work flow steps starting from the proof of concept of a new research technology up to the field demonstration considering a live example. We discuss the stages that are employed in ADNOC R&TD technology management process in assessing proposals, supervising projects progress, steering projects towards technology matu...

Zeolites (crystalline aluminosilicate) having 3D channel network are widely used by the chemical industry. Faujasite Y in particular is one of preferred micro-sized zeolite to be utilized as acid catalyst for catalytic cracking process. Considering the important applications of zeolite-Y, current research is directed to modify its surface propertie...

Zeolites are crystalline aluminosilicate possessing a 3D network structure and widely used for various applications such catalysis, adsorption and separation. However, zeolite with only microporosity exhibits diffusion limitation pertaining to transport of large molecules into the inner zeolite framework. One approach to enhance catalytic performan...

While bottom‐up syntheses of ordered nanostructured materials at colloidal length scales have been successful at producing close‐packed materials, it is more challenging to synthesize non‐close‐packed (ncp) structures. Here, a metal oxide nanostructure with ncp hollow sphere arrays was synthesized by combining a polymeric colloidal crystal template...

While bottom‐up syntheses of ordered nanostructured materials at colloidal length scales have been successful at producing close‐packed materials, it is more challenging to synthesize non‐close‐packed (ncp) structures. Here, a metal oxide nanostructure with ncp hollow sphere arrays was synthesized by combining a polymeric colloidal crystal template...

In natural gas processing plants, acid gas enrichment (AGE) units play a vital role in increasing H2S purity in the acid gas feed of sulfur recovery units (SRUs). Moreover, AGE units also produce a CO2-rich gas stream that is often vented to atmosphere. If CO2 purity is sufficiently high, this stream can be used as an injection gas for enhanced oil...

Herein, we report the synthesis of hierarchical AlPO4-5 and SAPO-5 molecular sieves that exhibit varying degrees of mesoporous interconnectivity by controlling the amount of triethylamine (TEA) (used as the structure directing agent) and the Si-to-Al ratio (Si/Al); the gel mixture had a composition of (1 − y) Al2O3:y SiO2:1.3 P2O5:x TEA:200 H2O. Th...

Single and few-layers MoS 2 were uniformly grown on the surface of chemically reduced graphene oxide (r-GO), via a facile liquid phase approach. The method is based on a simple functionalization of r-GO with oleyl amine which seems to affect significantly the MoS 2 way of growth. Scanning-transmission-electron microscopy (STEM) analysis revealed th...

Single and few-layers MoS 2 were uniformly grown on the surface of chemically reduced graphene oxide (r-GO), via a facile liquid phase approach. The method is based on a simple functionalization of r-GO with oleyl amine which seems to affect significantly the MoS 2 way of growth. Scanning-transmission-electron microscopy (STEM) analysis revealed th...

The remarkable electronic properties of colossal magnetoresistive manganites are widely believed to be caused by the competition between a ferromagnetic metallic state and an antiferromagnetic insulating state with complex spin, charge, and orbital ordering. However, the physics underlying their magnetotransport properties is still not clear, espec...

In this paper we use the example of a commercial NGL Plant in Abu Dhabi to explain the practical benefits of Advanced Model-based Optimization. We will describe and show how the key first step in such a study is validation: ensuring that model predictions of key results are matching the actual plant behavior. We will describe how the model is then...

Natural gas liquids (NGLs) are the main contributor to the profitability of natural gas processing plants. During the recent period of relatively low natural gas prices, NGLs spot prices have experienced a slower drop remaining relatively steady. Therefore, switching the operation of existing facilities towards a higher NGL production can lead to a...

In this work we present a physio-economic model supported by lab scale experiments assessing the economic viability of minichannel based carbon capture units. The Net Present Value of capital and operating Costs (NPVC) ensued throughout the plant life is selected as the benchmarking parameter. An optimization problem is formulated and solved with t...

The absorption of CO2 using amine solution can be significantly enhanced in microreactors that offer high surface area to volume ratio. In this work, chemical absorption of 10v% CO2 mixed with N2 into 20w% diethanolamine in water was investigated in microchannels with a circular cross-section. Absorption efficiency, mass transfer coefficient and CO...

Common approaches in designing natural gas dryers are based on empirical algebraic correlations and design heuristics. Such approaches fail to capture the process physics and are generally not optimal. In this work a new method for the design of natural gas dryers is presented. The method formulates a mixed integer nonlinear programming (MINLP) pro...

Current regulations of SOx emissions require Sulfur Recovery Units (SRUs) to achieve recoveries in excess of 99.9%. Capital cost of existing commercial Claus Tail gas clean up technologies capable of achieving that benchmark can amount to 45% of the total capital cost of the SRU. Adsorption based processes hold significant potential for achieving t...

A nanosized HY zeolite was synthesized and studied by means of 1H and 27Al NMR during thermal dehydration in the temperature range 20 – 600oC. The nanozeolite is comprised of a mixture of well crystalized ultrathin platelets and octahedral nanocrystals, dressed with penta-coordinated extra-framework Al(V). 1H NMR spin-lattice (T1) and spin-spin (T2...

Spatially well-distributed copper-zinc oxides supported on mesoporous silica (SBA-15 and commercial silica gel) showed high adsorption capacity for hydrogen sulfide (as high as 80 mgS/g(sorbent)) and stability during cyclic adsorption-regeneration process.

Go with the Flow Effective absorption or filtration can be achieved by having a material with multiple levels of porosity, so that the main flow can occur in the larger channels, while smaller passageways can be used to sequester a secondary material. It can be difficult to make these materials because the pores need to be different sizes, but stil...

The need for cements with good workability for oil well drilling purposes makes a systematic study necessary in order to investigate different cement-admixture combinations. In the present study the superplasticising effect induced by third-generation polycarboxylates was benchmarked against conventional melamine-based superplasticisers on oil well...