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Fast pyrolysis is a prominent and versatile process that involves thermal decomposition of biomass feedstocks to produce high volumes of liquid bio-oil, which may eventually be ...upgraded via deoxygenation pathways (hydrodeoxygenation, decarboxylation, or decarbonylation) into high energy content green fuels like gasoline, diesel and jet fuel. The quality of the bio-oil, its thermal stability, heating value, and the efficiency of the total conversion process can be improved by deoxygenation over properly designed catalysts. Despite the success of the available catalysts to significantly improve bio-oil quality by producing useful aromatic hydrocarbons, phenolics, or alkanes, there are still opportunities for further improvements of the catalytic performance with regards to their activity, product selectivity and resistivity against deactivation. The present work provides a comprehensive analysis of the recent developments of sulfur-free monometallic and bimetallic transition metal and noble metal supported catalysts for selective deoxygenation of vegetable oils and fatty acids model compounds for biofuel production. The attention focuses on the design of active sites on these catalysts as well as the acidic nature of the integrated supports for selectively manipulating mechanistic pathways. Moreover, this review emphasizes on the role of doping in stabilizing metal oxides to tune metal-support interaction (MSI) and electron donation properties, all strategies combined for the enhancement of biofuel production. The novelty of this review lies on bridging theoretical and experimental investigations aiming at describing and interpreting deoxygenation pathways of vegetable oils and related model compounds. Current challenges and perspective are also provided.
Selective altering of surface wettability in microfluidic channels provides a suitable platform for a large range of processes, such as the phase separation of multiphase systems, synthesis of ...reaction controlled, nanoliter sized droplet reactors, and catalyst impregnation. Herein we study the feasibility to tune the wettability of a flexible cyclic olefin copolymer (COC). Two methods were considered for enhancing the surface hydrophilicity. The first is argon/oxygen plasma treatment, where the effect of treatment duration on water contact angle and COC surface morphology and chemistry were investigated, and the second is coating COC with GO dispersions of different concentrations. For enhancing the hydrophobicity of GO-coated COC surfaces, three reduction methods were considered: chemical reduction by Hydroiodic acid (HI), thermal reduction, and photo reduction by exposure of GO-coated COC to UV light. The results show that as the GO concentration and plasma treatment duration increased, a significant decrease in contact angle was observed, which confirmed the ability to enhance the wettability of the COC surface. The increase in hydrophilicity during plasma treatment was associated with the increase in surface roughness on the treated surfaces, while the increase during GO coating was associated with introducing oxygen-containing groups on the GO-coated COC surfaces. The results also show that the different reduction methods considered can increase the contact angle and improve the hydrophobicity of a GO-coated COC surface. It was found that the significant improvement in hydrophobicity was related to the reduction of oxygen-containing groups on the GO-coated COC modified surface.
The effects of synthesis conditions on the FAU/EMT content and the size of nanocrystals, formed from inorganic aluminosilicate sols, were investigated. High-resolution transmission electron ...microscopy imaging and comparison of experimental X-ray diffraction patterns with simulations demonstrated that all materials made starting from synthesis mixtures in the composition range (1.8–33) SiO2:1 Al2O3:(2.7–33) Na2O:(41–1000) H2O contain FAU/EMT intergrowths. Compositions with low water content increase the FAU fraction up to 0.8 but the crystal size exceeds 100 nm. Extension of the higher FAU purity to nanocrystals was achieved only by first mixing the sol at high water content compositions that favor nanocrystal formation and thenafter a certain timelowering by freeze-drying the water to levels favoring the formation of FAU. Cryogenic transmission electron microscopy and small-angle X-ray scattering from representative optically clear and colloidally stable precursor sols (aged and crystallized at ambient temperature) reveal the formation of amorphous aggregates before the detection of crystals, in agreement with earlier findings and an existing model for the aggregative growth of the zeolite MFI. The presence of these amorphous aggregates coincides with the aforementioned state of sol that preserves the original trajectory toward nanocrystals after the pronounced reduction of water content by freeze-drying. If water reduction by freeze-drying is applied earlier (before the detection of amorphous aggregates), the sol follows the low water content trajectory toward larger crystals. Despite this memory effect, the sol at this stage is still agnostic toward FAU or EMT formation, the relative content of which is dominantly determined by the final water content. These findings demonstrate that it is possible to combine the effects of pre- and post-nucleation sol composition to steer crystal size and crystal structure, respectively. They confirm precursor nanoparticle evolution, while they emphasize the importance of solution phase composition at both pre- and post-nucleation stages of aggregative crystal growth.
Different types of amine-functionalized MOF structures were analyzed in this work using molecular simulations in order to determine their potential for post-combustion carbon dioxide capture and ...separation. Six amine models -of different chain lengths and degree of substitution- grafted to the unsaturated metal sites of the M
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(dobdc) MOF and its expanded version, M
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(dobpdc) were evaluated, in terms of adsorption isotherms, selectivity, cyclic working capacity and regenerability. Good agreement between simulation results and available experimental data was obtained. Moreover, results show two potential structures with high cyclic working capacities if used for Temperature Swing Adsorption processes: mmen/Mg/DOBPDC and mda-Zn/DOBPDC. Among them, the -mmen functionalized structure has higher CO
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uptake and better cyclability (regenerability) for the flue gas mixtures and conditions studied. Furthermore, it is shown that more amine functional groups grafted on the MOFs and/or full functionalization of the metal centers do not lead to better CO
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separation capabilities due to steric hindrances. In addition, multiple alkyl groups bonded to the amino group yield a shift in the step-like adsorption isotherms in the larger pore structures, at a given temperature. Our calculations shed light on how functionalization can enhance gas adsorption
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the cooperative chemi-physisorption mechanism of these materials, and how the materials can be tuned for desired adsorption characteristics.
Zeolite-based molecular sieves are applied in industrial dehydration units for their high water uptake capacities and extremely low equilibrium pressure of water vapor. During their operational life, ...they tend to lose their water vapor adsorption capacity slowly. To optimize the usage of molecular sieves in dryer units, it is vital to understand the mechanism(s) leading to deactivation. In this work, the capacity loss was studied by exposing LTA- and FAU-type zeolites to methanol and heptane vapors under relatively harsh conditions using repetitive adsorption/regeneration cycles. A simple microflow unit was designed and used for the deactivation experiments. The water vapor adsorption capacity of the resulting samples was measured using a gravimetric analyzer. In addition, they were characterized by classic XRD, 13C NMR, and TGA techniques. The crystallinity of fresh and spent zeolite XRD patterns was not drastically affected even after exposure to the contaminants. It was found that methanol easily gave rise to a severe loss of water vapor adsorption capacity, much more so than heptane. Water vapor uptake in the methanol exposed samples is ∼50% lower than that for the fresh zeolites. This is attributed to nonvolatile, residual hydrocarbons.
Substantial research has been performed on Building Information Modeling (BIM) in various topics, for instance, the use and benefit of BIM in design, construction, sustainable environment building, ...and Facility assets over the past several years. Although there are various studies on these topics, Building Information Modeling (BIM) awareness through facilities management is still relatively poor. The researcher's interest is increased in BIM study is based heavily upon the perception that it can facilitate the exchange and reuse of information during various project phases. This property and others can be used in the Iraqi Construction industry to motivate the government to eliminate the change resistance to use innovations in the Iraqi construction industry. Even though many scholars and practitioners agree on the potential application and benefits of BIM in construction/ Facilities Management FM, it is yet unknown why BIM is used and what criteria facilitate BIM achievement in O&M. As long as the actual usage and acceptance of BIM in the Operation and Maintenance phase is still a central issue in practice, therefor depending on the extensive well ground literature review a conceptual acceptance model is proposed in this paper by applying the technology acceptance theories such as Technology Acceptance Model (TAM) and Task Technology Fit (TTF) to explore how the extent of facilities management staff going to accept and adopt the new international technology (BIM).
Ethylene is an important feedstock for the production of many key-valued compounds, especially polymers. About 60% of the total ethylene produced is utilized for the production of polyethylene, while ...ethylene is normally produced by steam cracking of naphtha along with traces of ethane, which is undesirable. Considering the energy-intensive nature of the current technology to obtain ultrapure ethylene, the development of novel materials for separating ethylene from ethane by adsorption is of great significance, yet it remains challenging owing to the close molecular sizes and physical properties of the two compounds. Both ethylene- and ethane-selective adsorbents are reviewed in this work. Yet, as the industrial feed is rich in ethylene with traces of ethane, in order to obtain polymer grade ethylene, multiple adsorption–desorption cycles are required, which is yet again energy-demanding. Thus, ethane-selective adsorbents are energetically favorable; hence, in this Review, we pay particular focus on ethane-selective adsorbents. The rationale behind reverse-selective adsorbents is critically reviewed and discussed. Most of the ethane-selective adsorbents have been reported to exhibit low selectivity compared to ethylene-selective ones, as reverse-selectivity is mostly based on weak van der Waals interactions. In addition, we focused on various reported mechanisms behind the adsorptive separation of ethane/ethylene mixtures, as well as modifications and surface functionalization techniques reported for different types of adsorbents investigated for this separation.
In an ever-growing attempt to reduce the excessive anthropogenic CO2 emissions, several CO2 capture technologies have been developed in recent years. Adsorption using solid carbonaceous materials is ...one of the many promising examples of these technologies. Carbon-based materials, notably activated carbons, are considered very attractive adsorbents for this purpose given their exceptional thermal stability and excellent adsorption capacities. More importantly, the ability to obtain activated carbons from agricultural wastes and other biomass that are readily available makes them good candidates for several industrial applications ranging from wastewater treatment to CO2 adsorption, among others. Activated carbons from biomass can be prepared using various techniques, resulting in a range of textual properties. They can also be functionalized by adding nitrogen-based groups to their structure that facilitates faster and more efficient CO2 capture. This review provides a detailed overview of the recent work reported in this field, highlighting the different preparation methods and their differences and effects on the textual properties such as pore size, surface area, and adsorption performance in terms of the CO2 adsorption capacity and isosteric heats. The prospect of activated carbon functionalization and its effect on CO2 capture performance is also included. Finally, the review covers some of the pilot-plant scale processes in which these materials have been tested. Some identified gaps in the field have been highlighted, leading to the perspectives for future work.
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•A review on activated carbon from biomass-based sources for CO2 capture.•An overview of the synthesis process through physical and chemical activation, and their effect on adsorbent properties.•Recent development with respect to activation methods and the effect on CO2 adsorption capacity.•Amine functionalization of activated carbon and its effect on CO2 adsorption.•Pilot plant testing and challenges of commercialization.
This study presents a simple approach to modify the wettability of polydimethylsiloxane (PDMS) using graphene oxide (GO). The proposed method involves a series of steps including O
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plasma ...treatment, APTES functionalization, GO deposition, and substrate washing and drying. The presence of a GO film on the PDMS surface was confirmed by SEM, AFM, FTIR, and GO reduction using HI acid. The GO film significantly improved the water wettability of the PDMS substrates, as evidenced by a drop in water contact angle from 112° to 40°. Over the course of time, the contact angle increases to reach a value of almost 70° after 4 days before finally settling at a steady value of 82° after 9 days. Once this value was reached, no further changes were observed in the contact angle. Even with the increase in the contact angle, the proposed method shows an enhancement in the hydrophilicity of the PDMS of almost 35°. This treatment improved also the wettability of the PDMS under an oil medium where a dispensed water droplet attaches on the GO-coated PDMS surface. The versatility of this method lies in its ability to tune the wettability of PDMS, making it suitable for a diverse range of applications. For instance, it can be used to create flexible hydrophilic membranes for efficient oil/water separation or to fabricate hydrophilic microfluidic chips for biological purposes. Overall, this study offers a simple and effective approach for altering the surface properties of PDMS, expanding its potential for a wide range of applications.
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