Recent Submissions

  • High-performance 7-channel monolith supported SSZ-13 membranes for high-pressure CO2/CH4 separations

    Li, Yanmei; Wang, Yulei; Guo, Mingyang; Liu, Bo; Zhou, Rongfei; Lai, Zhiping (Journal of Membrane Science, Elsevier BV, 2021-03-18) [Article]
    Continuous SSZ-13 zeolite membranes were reproducibly synthesized on the inner surface of 7-channel monolith supports for the first time. Packing density and mechanical strength were much greater than those using normal tubular and disc membranes. The membrane in the central channel of monolith was thinner than these of the side channels. The best monolith supported SSZ-13 membrane (with spacers) showed a CO2/CH4 selectivity of 72 and a CO2 permeance of 163 × 10-8 mol/(m2 s Pa) at pressure drop of 2.0 MPa and feed flow rate of 20 standard L/min for an equimolar CO2/CH4 mixture. Such separation performance was higher than most of zeolite membranes prepared on single-channel tubes or discs. The effects of temperature, pressure drop and fluid state on separation performance of the membranes were investigated. The extent of concentration polarization through monolith supported membrane was modelled by the concentration polarization index (CPI). Increasing feed flow rate and inserting spacers into the channels were effective ways to reduce the negative influence of concentration polarization. The latter way was more effective for our monolith supported membranes than the former because the dead volume was reduced greatly. Carbon dioxide permeance and CO2/CH4 selectivity increased by 24% and 85%, respectively, when the CPI increased from 0.79 (without spacer) to 0.89 (with spacer) at feed flow rate of 20 standard L/min.
  • Rapid soot inception via α-alkynyl substitution of polycyclic aromatic hydrocarbons

    Liu, Peng; Jin, Hanfeng; Chen, Bingjie; Yang, Jiuzhong; Li, Zepeng; Bennett, Anthony; Farooq, Aamir; Sarathy, Mani; Roberts, William L. (Fuel, Elsevier BV, 2021-03-17) [Article]
    Soot particles alter global climate and dominate the origin and evolution of carbonaceous interstellar material. Convincing experimental evidence has linked polycyclic aromatic hydrocarbons (PAH) to soot inception under low-temperature astrochemistry and high-temperature combustion conditions. However, significant gaps still remain in the knowledge of PAH and soot formation mechanisms. Here, we report theoretical and experimental evidence for a soot inception and growth pathway driven by peri-condensed aromatic hydrocarbons (PCAH) with an alkynyl substitution. Initially, free radicals attack the α-alkynyl substitution of PCAHs to form covalently bound compounds yielding resonantly stabilized radicals (RSRs), which promote further clustering through repeated addition reactions with negligible energy barriers. The proposed pathway is shown to be competitive at temperatures relevant to astrochemistry, engine exhaust manifold and flames because it does not require H-abstraction reactions, the requisite reaction precursors are in abundance, and the reaction rate is high. Such addition reactions of PCAHs with α-alkyne substituents create covalently bound clusters from moderate-size PAHs that may otherwise be too small to coagulate.
  • Stable Cr-MFI Catalysts for the Nonoxidative Dehydrogenation of Ethane: Catalytic Performance and Nature of the Active Sites

    De, Sudipta; Ould-Chikh, Samy; Aguilar, Antonio; Hazemann, Jean-Louis; Zitolo, Andrea; Ramirez, Adrian; Telalovic, Selvedin; Gascon, Jorge (ACS Catalysis, American Chemical Society (ACS), 2021-03-16) [Article]
    The nonoxidative catalytic dehydrogenation of ethane allows the production of ethylene at lower temperatures than those applied in steam crackers. This, however, requires stable catalysts that minimize coke production. Here, we report a single-component, promoter-free, low-loading, Cr-based catalyst exhibiting high activity, long-term stability, and improved regeneration properties for the direct dehydrogenation of ethane to ethylene. According to our detailed operando X-ray absorption spectroscopic analysis, the use of all-silica MFI zeolite as support promotes the stabilization of CrII(−O–Si≡)2 species with high coke resistance, even when the dehydrogenation is carried out under high ethane partial pressures (1.5 bar).
  • Rhodium Nanoparticle Size Effects on the CO2 Reforming of Methane and Propane

    Alabdullah, Mohammed; Ibrahim, Mahmoud; Dhawale, Dattatray Sadashiv; Bau, Jeremy A; Harale, Aadesh; Katikaneni, Sai; Gascon, Jorge (ChemCatChem, Wiley, 2021-03-10) [Article]
    The CO 2 (dry) reforming of hydrocarbons offers an opportunity to convert greenhouse gases into synthesis gas, which can further transform to various valued products. Here we explore the influence of Rh particle size and support on the reforming of propane and methane. To that end, Rh nanoparticles with controlled sizes varying from 1.6-8.0 nm were synthesized following a polyol reduction method and then dispersed on three different solids: CeZrO 2 , ZrO 2 , and CeO 2 . Catalytic turnover rates along with advanced characterization of fresh and spent catalysts reveal a linear correlation of turnover rates with Rh particle size for both methane and propane reforming. The nature and rate of coke deposition are highly dependent on the support used and its interaction with the metallic phase.
  • Highly Selective and Stable Production of Aromatics via High-Pressure Methanol Conversion

    Shoinkhorova, Tuiana; Cordero-Lanzac, Tomás; Ramirez, Adrian; Chung, Sang-ho; Dokania, Abhay; Ruiz-Martinez, Javier; Gascon, Jorge (ACS Catalysis, American Chemical Society (ACS), 2021-03-05) [Article]
    In the current petrochemical market, the global demand for aromatics, especially benzene, toluene, and xylenes (BTXs), has increased sharply. The methanol-to-aromatic conversion (MTA) over ZSM-5 is among the most promising routes to satisfy this ever-growing demand. In this work, we show that highpressure operation during MTA leads to a large increase in aromatic selectivity while enhancing stability on-stream. Stable operation along with a very high selectivity to aromatics (up to 50%, with 20% BTXs) can be achieved on a commercial high-silica ZSM-5 (SiO2/Al2O3 = 280) at 400 °C, 30 bar total pressure, and WHSV = 8 h−1. The high partial pressure of primary olefins and the promoted methanol-induced hydrogen-transfer pathway result in an exponential increase in aromatization, while the high partial pressure of steam generated via dehydration of methanol leads to in situ coke removal and, therefore, to a much slower deactivation of the zeolite
  • Defect Engineering in Metal-Organic Frameworks Towards Advanced Mixed Matrix Membranes for Efficient Propylene/Propane Separation

    Lee, Tae Hoon; Jung, Jae Gu; Kim, Yu Jin; Roh, Ji Soo; Yoon, Hee Wook; Ghanem, Bader; Kim, Hyo Won; Cho, Young Hoon; Pinnau, Ingo; Park, Ho Bum (Angewandte Chemie, Wiley, 2021-03-02) [Article]
    Highly permselective and durable membrane materials have been sought for energy-efficient C3H6/C3H8 separation. Mixed-matrix membranes (MMMs) comprising a polymer matrix and metal-organic frameworks (MOFs) are promising candidates for this application; however, rational matching of filler-matrix is challenging and their separation performances need to be further improved. Here, we propose a novel strategy of “defect engineering” in MOFs as an additional degree of freedom to design advanced MMMs. MMMs incorporated with defect-engineered MOFs exhibit exceptionally high C3H6 permeability and maintained C3H6/C3H8 selectivity, especially with enhanced stability under industrial mixed-gas conditions. The gas transport, sorption, and material characterizations reveal that the defect sites in MOFs provide the resulting MMMs with not only ultrafast diffusion pathways but also favorable C3H6 sorption by forming π-complexation with unsaturated open metal sites, confirmed by in-situ FT-IR studies. Most importantly, the concept is also valid for different polymer matrices and gas pairs, demonstrating its versatile potential in other fields.
  • Surrogate formulation and molecular characterization of sulfur species in vacuum residues using APPI and ESI FT-ICR mass spectrometry

    Abdul Jameel, Abdul Gani; Alquaity, Awad B.S.; Campuzano, Felipe; Emwas, Abdul-Hamid M.; Saxena, Saumitra; Sarathy, Mani; Roberts, William L. (Fuel, Elsevier BV, 2021-02-26) [Article]
    Vacuum residues (VR) are the bottom of the barrel products left after vacuum distillation of crude oils. VR are primarily used as feedstock for production of syn-gas and hydrogen via gasification; and heavy fuel oil (HFO) for use as fuel in power generation and shipping. However, VR contain relatively large amounts of sulfur (upto 8% by mass) and require the removal of varying amounts depending on the emission norms (eg. International Maritime Organization 2020 sulfur regulations). Understanding the fuel molecular structure and, in particular, the structure of sulfur species enables the adoption and optimization of suitable desulfurization strategies. In the present work, detailed molecular characterization of the sulfur species in VR was performed using positive ion atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) coupled to Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Ions possessing mass to charge (m/z) in the range of 100 to 1200 were detected using the ultra-high resolution instrument and were resolved into unique chemical formulas (CcHhSsNnOo). The assigned masses were then divided into molecular classes based on the presence of heteroatoms, and plots of carbon number versus double bond equivalency (DBE) were made for each molecular class. The molecular classes were further sub-divided based on the presence of sulfur families like sulfides (Su), thiophenes (Th), benzothiophenes (BT), dibenzothiophenes (DBT) and benzonaphthothiophene (BNT) and their derivatives. A single surrogate molecule that represents the average structure of the VR sample was then designed based on the average molecular parameters (AMP) obtained from APPI and ESI FT-ICR MS. Plausible core skeletal structures of VR were drawn from the average DBE value, and then a symmetrical, alkylated, polyaromatic sulfur heterocycles (PASH) molecule was formulated as the VR surrogate. A number of physical and thermo-chemical properties of the VR surrogate were then predicted using quantitative structure property relationships (QSPR). The VR surrogate proposed here will enable high-fidelity computational studies, including chemical kinetic modeling, property estimation, and emissions modeling.
  • The Importance of Thermal Treatment on Wet-Kneaded Silica–Magnesia Catalyst and Lebedev Ethanol-to-Butadiene Process

    Chung, Sang-Ho; Galilea, Adrian; Shoinkhorova, Tuiana; Mukhambetov, Ildar; Abou-Hamad, Edy; Telalovic, Selevedin; Gascon, Jorge; Ruiz-Martinez, Javier (Nanomaterials, MDPI AG, 2021-02-26) [Article]
    The Lebedev process, in which ethanol is catalytically converted into 1,3-butadiene, is an alternative process for the production of this commodity chemical. Silica–magnesia (SiO2–MgO) is a benchmark catalyst for the Lebedev process. Among the different preparation methods, the SiO2–MgO catalysts prepared by wet-kneading typically perform best owing to the surface magnesium silicates formed during wet-kneading. Although the thermal treatment is of pivotal importance as a last step in the catalyst preparation, the effect of the calcination temperature of the wet-kneaded SiO2–MgO on the Lebedev process has not been clarified yet. Here, we prepared and characterized in detail a series of wet-kneaded SiO2–MgO catalysts using varying calcination temperatures. We find that the thermal treatment largely influences the type of magnesium silicates, which have different catalytic properties. Our results suggest that the structurally ill-defined amorphous magnesium silicates and lizardite are responsible for the production of ethylene. Further, we argue that forsterite, which has been conventionally considered detrimental for the formation of ethylene, favors the formation of butadiene, especially when combined with stevensite.
  • One-step conversion of crude oil to light olefins using a multi-zone reactor

    Alabdullah, Mohammed A.; Rodriguez Gomez, Alberto; Shoinkhorova, Tuiana; Dikhtiarenko, Alla; Chowdhury, Abhishek Dutta; Hita, Idoia; Kulkarni, Shekhar Rajabhau; Vittenet, Jullian; Sarathy, Mani; Castaño, Pedro; Bendjeriou-Sedjerari, Anissa; Abou-Hamad, Edy; Zhang, Wen; Ali, Ola S.; Morales-Osorio, Isidoro; Xu, Wei; Gascon, Jorge (Nature Catalysis, Springer Science and Business Media LLC, 2021-02-25) [Article]
    With the demand for gasoline and diesel expected to decline in the near future, crude-to-chemicals technologies have the potential to become the most important processes in the petrochemical industry. This trend has triggered intense research to maximize the production of light olefins and aromatics at the expense of fuels, which calls for disruptive processes able to transform crude oil to chemicals in an efficient and environmentally friendly way. Here we propose a catalytic reactor concept consisting of a multi-zone fluidized bed that is able to perform several refining steps in a single reactor vessel. This configuration allows for in situ catalyst stripping and regeneration, while the incorporation of silicon carbide in the catalyst confers it with improved physical, mechanical and heat-transport properties. As a result, this reactor–catalyst combination has shown stable conversion of untreated Arabian Light crude into light olefins with yields per pass of over 30 wt% with a minimum production of dry gas.
  • Efficient alkane oxidation under combustion engine and atmospheric conditions

    Wang, Zhandong; Ehn, Mikael; Rissanen, Matti P.; Garmash, Olga; Quéléver, Lauriane; Xing, Lili; Monge Palacios, Manuel; Rantala, Pekka; Donahue, Neil M.; Berndt, Torsten; Sarathy, Mani (Communications Chemistry, Springer Science and Business Media LLC, 2021-02-18) [Article]
    AbstractOxidation chemistry controls both combustion processes and the atmospheric transformation of volatile emissions. In combustion engines, radical species undergo isomerization reactions that allow fast addition of O2. This chain reaction, termed autoxidation, is enabled by high engine temperatures, but has recently been also identified as an important source for highly oxygenated species in the atmosphere, forming organic aerosol. Conventional knowledge suggests that atmospheric autoxidation requires suitable structural features, like double bonds or oxygen-containing moieties, in the precursors. With neither of these functionalities, alkanes, the primary fuel type in combustion engines and an important class of urban trace gases, are thought to have minor susceptibility to extensive autoxidation. Here, utilizing state-of-the-art mass spectrometry, measuring both radicals and oxidation products, we show that alkanes undergo autoxidation much more efficiently than previously thought, both under atmospheric and combustion conditions. Even at high concentrations of NOX, which typically rapidly terminates autoxidation in urban areas, the studied C6–C10 alkanes produce considerable amounts of highly oxygenated products that can contribute to urban organic aerosol. The results of this inter-disciplinary effort provide crucial information on oxidation processes in both combustion engines and the atmosphere, with direct implications for engine efficiency and urban air quality.
  • The Role of Intermediate-Temperature Heat Release in Octane Sensitivity of Fuels with Matching Research Octane Number

    Singh, Eshan; Sarathy, Mani (Energy & Fuels, American Chemical Society (ACS), 2021-02-16) [Article]
    Improving the efficiency of internal combustion engines is important for reducing global greenhouse gas emissions; the efficiency of spark ignition (SI) engines is limited by the knock phenomenon. As opposed to naturally aspirated engines, turbocharged engines operate at beyond research octane number (RON) conditions, and fuel octane sensitivity (OS = RON – motor octane number (MON)) becomes important under such conditions. Previous work by this group [ Energy Fuels 2017, 31, 1945−1960, DOI: 10.1021/acs.energyfuels.6b02659] elucidated the chemical kinetic origins of OS; this study is extended to provide a qualitative, as well as quantitative, definition of OS, based on fundamental ignition markers. A varying amount of toluene is blended with various primary reference fuels to match the ignition delay of the targeted research octane number fuels, allowing a range of octane sensitivities for each research octane number. This study establishes a correlation between OS and heat release rates at low, intermediate, and high temperatures. The significance and chemical origins of intermediate-temperature heat release in defining the OS of toluene blended in a mixture of iso-octane and n-heptane is also clarified. For the toluene–iso-octane–n-heptane mixtures considered here, low-temperature reactivity was not found to be a key marker of OS. The results also show areas of improved efficiency in beyond RON operating conditions, where high-sensitivity fuels could be beneficial.
  • Composition-performance Relationships in Catalysts Formulation for the Direct Conversion of Crude Oil to Chemicals

    Alabdullah, Mohammed A.; Shoinkhorova, Tuiana; Rodriguez-Gomez, Alberto; Dikhtiarenko, Alla; Vittenet, Jullian; Ali, Ola S.; Morales-Osorio, Isidoro; Xu, Wei; Gascon, Jorge (ChemCatChem, Wiley, 2021-02-04) [Article]
    Maximizing the production of petrochemicals from crude oil atthe expense of fuels is among the most important targets forrefiners. In this conversion, catalyst composition and formula-tion play a key role. Here we present a thorough study of theeffect of formulated FCC catalyst composition on the one-stepcracking of Arabian light crude oil. Our results demonstrate thatover a 35 wt.% yield to light olefins can be achieved on spray-dried catalysts containing 1 : 1 mixtures of ZSM-5 and FAUzeolites (alongside binder and clay). Coke deposition andcatalyst deactivation can be correlated to the nature andcontent of each zeolite component.
  • Exfoliation of surfactant swollen layered MWW zeolites into two-dimensional zeolite nanosheets using telechelic liquid polybutadiene

    Sabnis, Sanket; Tanna, Vijesh A.; Gulbinski, Jason; Zhu, Jiaxin; Nonnenmann, Stephen S.; Sheng, Guan; Lai, Zhiping; Winter, H. Henning; Fan, Wei (Microporous and Mesoporous Materials, Elsevier BV, 2021-02) [Article]
    Two-dimensional (2D) zeolites have the potential to enhance mass transport by reducing diffusion lengths and thus find applications in catalysis and separation. High aspect ratio 2D zeolite nanosheets are required for fabrication of thin, high-flux zeolite membranes. Preparation of 2D zeolite nanosheets can be achieved by exfoliation of layered zeolite precursors, which usually requires multiple steps including swelling with cationic surfactants, exfoliation by applying a mechanical force such as shearing or sonication, purification and removal of the surfactants. The exfoliation of surfactant swollen layered zeolite precursors has been studied using molten polystyrene and telechelic liquid polybutadiene, but still requires extensive shearing force. Recently, a novel one-step exfoliation method has been developed for non-swollen MWW zeolite precursors using tetrabutylammonium hydroxide (TBAOH) solution. In this work, we study the exfoliation of surfactant swollen MWW layered precursors (with and without aluminum) in commercially available liquid hydroxyl-terminated polybutadiene (HTPB) with the aim to provide fundamental understanding of the interaction between the liquid polybutadiene and the surfactant swollen layered zeolite precursors. It was found that surfactant swollen ITQ-1, (ITQ-1(S)), a pure silica layered precursor with MWW framework after being swollen with a cationic surfactant, can be exfoliated in liquid HTPB at room temperature without applying any additional shearing force. The aluminum containing surfactant swollen MWW precursors can be also exfoliated in HTPB at room temperature, but require additional shearing forces. The exfoliation process was monitored using rheology experiments and studied by tuning the composition of the zeolite precursors. The interaction between the layered zeolite precursor and the hydroxyl group of the liquid polybutadiene allows the polymer to intercalate the precursor and exfoliate it into nanosheets. The presence of framework aluminum and the nature of the organic structure directing agents (OSDAs) are key parameters affecting the exfoliation process. Framework Al is unfavorable for the exfoliation possibly due to the surface charges introduced by the aluminum. Bulky OSDA, trimethyladamantammonium (TMAda+), in the interlayer spacing may facilitate the exfoliation.
  • Predicting Entropy and Heat Capacity of Hydrocarbons using Machine Learning

    Aldosari, Mohammed; Yalamanchi, Kiran K.; Gao, Xin; Sarathy, Mani (Energy and AI, Elsevier BV, 2021-02) [Article]
    Chemical substances are essential in all aspects of human life, and understanding their properties is essential for developing chemical systems. The properties of chemical species can be accurately obtained by experiments or ab initio computational calculations; however, these are time-consuming and costly. In this work, machine learning models (ML) for estimating entropy, S, and constant pressure heat capacity, Cp, at 298.15 K, are developed for alkanes, alkenes, and alkynes. The training data for entropy and heat capacity are collected from the literature. Molecular descriptors generated using alvaDesc software are used as input features for the ML models. Support vector regression (SVR), v-support vector regression (v-SVR), and random forest regression (RFR) algorithms were trained with K-fold cross-validation on two levels. The first level assessed the models' performance, and the second level generated the final models. Between the three ML models chosen, SVR shows better performance on the test dataset. The SVR model was then compared against traditional Benson's group additivity to illustrate the advantages of using the ML model. Finally, a sensitivity analysis is performed to find the most critical descriptors in the property estimations.
  • Probing the Chemical Kinetics of Minimalist Functional Group Gasoline Surrogates

    Ilieş, Bogdan Dragoş; Khandavilli, Muralikrishna; Li, Yang; Kukkadapu, Goutham; Wagnon, Scott W.; Abdul Jameel, Abdul Gani; Sarathy, Mani (Energy & Fuels, American Chemical Society (ACS), 2021-01-31) [Article]
    Surrogate mixtures are routinely used for understanding gasoline fuel combustion in engine simulations. The general trend in surrogate formulation has been to increase the number of fuel components in a mixture to better emulate real fuel properties. Recently, a new surrogate design strategy based on functional group analysis of real gasolines was proposed using a minimal number of species [minimalist functional group (MFG)—approach]. MFG surrogates (having just one or two components) could experimentally capture the ignition delay time (IDT), threshold sooting index, and smoke point of different gasoline fuels with hundreds of components. However, other combustion characteristics were not explored, and kinetic modeling of MFG surrogates was not reported. These aspects are addressed in this paper, where the combustion behavior of MFG surrogates for various gasolines was assessed by simulating IDT, jet-stirred reactor oxidation, and premixed laminar flame speeds using chemical kinetic modeling. MFG simulations were compared with experimental data of the real gasolines as well as with the more complex multicomponent (five to nine species) surrogates. This study reveals that binary MFG surrogate mixtures are capable of accurately simulating the combustion behavior of more complex gasoline fuels with hundreds of components.
  • Electrospun Adsorptive Nanofibrous Membranes from Ion Exchange Polymers to Snare Textile Dyes from Wastewater

    Cseri, Levente; Topuz, Fuat; Abdulhamid, Mahmoud; Alammar, Abdulaziz; Budd, Peter M.; Szekely, Gyorgy (Advanced Materials Technologies, Wiley, 2021-01-27) [Article]
    Increasing discharges of industrial wastewater, along with ever-stricter regulations for the protection of natural water sources, have amplified the demand for highly efficient water treatment technologies. Here, electrospun nanofibrous polyimides enhanced with ion exchange properties are proposed as adsorptive membranes for the treatment of dye-loaded textile wastewater. With the careful selection of monomers, carboxyl-functionalized porous polyimides are synthesized in a single step and then further decorated with strong cation and anion exchange side groups. Nuclear magnetic resonance spectroscopy and thermal gravimetric analysis are used to investigate the alkylation degree and total exchange capacity of the polymers. The electrospinning conditions are optimized to produce highly flexible membrane mats with a uniform nanofibrous structure. A series of dye sorption experiments on the nanofibrous membranes reveals the adsorption kinetics and the effects of the polyimide backbone, the charged side groups, and the hydrophilicity. A recycling study is conducted to confirm the stability of the adsorbent membranes. The results suggest that nanofibrous polyimide membranes enhanced with ion exchange properties are promising candidates for the treatment of dye-laden wastewater. Owing to their facile syntheses and unique properties, these membranes show promising potential in environmental applications.
  • Integrating pore interconnectivity and adaptability in a single crystal hierarchical zeolite for liquid alkylation

    Liu, Baoyu; Huang, Jiajin; Liao, Zhantu; Zhu, Chongzhi; Chen, Qiaoli; Sheng, Guan; Zhu, Yihan; Huang, Yi; Dong, Jinxiang (AIChE Journal, Wiley, 2021-01-20) [Article]
    Zeolite belongs to one of the most important families of solid acid catalysts in chemical industries. It is, however, severely constrained by the diffusion limitation for bulky molecules, a lack of multifunctionality for sequential reactions and pore adaptability toward specific adsorbates due to its small micropore size and simple aluminosilicate framework. Introducing mesopores into a zeolite toward realizing hierarchical zeolites is a prevailing strategy but one that usually suffers from compromised crystallinity as well as insufficient interconnectivity and openness of the mesopores. Herein, a novel acid-redox co-functionalized single-crystalline zeolite with highly open and interconnected mesopores is designed and fabricated. As a proof-of-concept study, we integrate solid acid and Fe-oxy redox sites into a hierarchical MEL zeolite with well-characterized microporosity and mesoporosity. This zeolite exhibits superior activity and stability toward alkylation between mesitylene with benzyl alcohol, arising from greatly facilitated intra-crystal molecular diffusion, mitigated metal leaching and optimized adsorbate-pore wall interactions.
  • Effect of carbon dioxide environment on the thermal behavior of sugarcane pyrolysis oil

    Ordonez-Loza, Javier; Valdes, Carlos; Chejne, Farid; Perez, Manuel Garcia; Zhang, Wen; Emwas, Abdul-Hamid M.; Sarathy, Mani (Journal of Analytical and Applied Pyrolysis, Elsevier BV, 2021-01-18) [Article]
    The integration of new CO2 capture and storage technologies in energy generation processes has led to the development and research in oxy-fuel combustion. In this technology, the carbon footprint is reduced if the fuel comes from a renewable source such as bio-oil (pyrolysis oil derived from biomass). This is a subject of growing interest. In this manuscript, we show bio-oil characterization using advanced techniques to elucidate the presence of oxygenated groups and aromatic compounds. We report that the presence of CO2 present in oxy-fuel environments modifies the thermal behavior of pyrolysis oils derived from sugarcane. At temperatures between 400°C and 700°C under CO2 atmosphere, there is evidence of reactions induced by the presence of CO2 modifying the behavior of carbonization reactions as crosslinking, aromatization, and condensation. The presence of CO2 likely induced a pH reduction. The chemical composition of char samples obtained at 400 °C and 700 °C were analyzed using FTIR and Thermal Analysis. These analyzes, allowed to elucidate the role of CO2 in carbonization. It was found that the cleavage of functional groups corresponding to the oligomers of lignin present in the bio-oil is strongly influenced by the presence of CO2. The presented results show that in CO2 atmospheres several new functional groups were observed in the char after carbonization processes. The phenomena observed were explained by the interactions of carbon dioxide with the oxygenated compounds in the solid phase formation at temperatures close to 400 °C.
  • Laminar Burning Velocities of Formic Acid and Formic Acid/Hydrogen Flames: An Experimental and Modeling Study

    Osipova, K.N.; Sarathy, Mani; Korobeinichev, Oleg P.; Shmakov, A.G. (Energy & Fuels, American Chemical Society (ACS), 2021-01-05) [Article]
    Laminar flame speed of formic acid and formic acid/hydrogen (4/1) flames was studied both experimentally and numerically. Experiments with flames of pure formic acid were performed at temperatures of 373 and 423 K, while for formic acid/hydrogen flames the temperature value was 368 K. All of the experiments were performed under atmospheric pressure and at an equivalence ratio ranging from 0.5 to 1.5. To measure the laminar flame speed, the heat flux balance technique was applied. Three detailed chemical-kinetic mechanisms were tested on experimental data. Experiments showed that addition of 20% of hydrogen increases the laminar burning velocity of formic acid, for example, at around 1.5 for stoichiometric flames. The comparison of experimental and numerical data showed that all models tend to overestimate laminar burning velocities of studied flames, especially in the case of rich flames. The obtained results indicate that further improvement of existing chemical-kinetic models of formic acid oxidation is highly required.
  • Hole-Type Spacers for More Stable Shale Gas-Produced Water Treatment by Forward Osmosis

    Alqattan, Jawad; Kim, Youngjin; Kerdi, Sarah; Qamar, Adnan; Ghaffour, NorEddine (Membranes, MDPI AG, 2021-01-03) [Article]
    An appropriate spacer design helps in minimizing membrane fouling which remains the major obstacle in forward osmosis (FO) systems. In the present study, the performance of a hole-type spacer (having holes at the filament intersections) was evaluated in a FO system and compared to a standard spacer design (without holes). The hole-type spacer exhibited slightly higher water flux and reverse solute flux (RSF) when Milli-Q water was used as feed solution and varied sodium chloride concentrations as draw solution. During shale gas produced water treatment, a severe flux decline was observed for both spacer designs due to the formation of barium sulfate scaling. SEM imaging revealed that the high shear force induced by the creation of holes led to the formation of scales on the entire membrane surface, causing a slightly higher flux decline than the standard spacer. Simultaneously, the presence of holes aided to mitigate the accumulation of foulants on spacer surface, resulting in no increase in pressure drop. Furthermore, a full cleaning efficiency was achieved by hole-type spacer attributed to the micro-jets effect induced by the holes, which aided to destroy the foulants and then sweep them away from the membrane surface.

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