Role Of Hydroxyl Groups Research Articles

Optimizing biosurfactant structure: Experimental and theoretical investigation of the influence of hydroxyl groups on sour corrosion mitigation

Oil and natural gas remain crucial for meeting global energy demands, but their extraction and processing face significant challenges due to sour corrosion. This study explores the influence of hydroxyl groups on the performance of biosurfactants, specifically sorbitol oleate (SOCI) and pentaerythritol oleate (POCI), in sour environments. This study reveals that the presence of more hydroxyl groups in inhibitor molecules significantly enhances their effectiveness against sour corrosion. A weight loss study showed that the corrosion rates dropped to 0.033 mm/y for POCI and 0.005 mm/y for SOCI from an initial rate of 0.490 mm/y in the blank solution, indicating the superior inhibition efficiency of SOCI (98.9 %) compared to POCI (93.3 %) at 24 × 10−4 M. Electrochemical measurements corroborated these findings, demonstrating increased corrosion resistance and reduced current densities in the presence of both inhibitors, with SOCI exhibiting better performance. The inhibition mechanism involves a combination of physical and chemical adsorption. Density functional theory calculations indicated the role of hydroxyl groups in enhancing adsorption and corrosion inhibition efficiency, with SOCI exhibiting a smaller energy gap, lower hardness, and higher softness compared to POCI. MD simulations confirmed the stable adsorption of both inhibitors on the Fe (110) surface, with SOCI showing a more favorable orientation and stronger interaction due to its higher number of hydroxyl groups. This facilitates stronger adsorption on the CS surface and the formation of a more robust protective film. The combined experimental and computational findings highlight the importance of molecular structure, film-forming ability, and hydroxyl content for the design and development of next-generation hydroxyl-rich biosurfactants for mitigating sour corrosion in the oil and gas industry.

Role of hydroxyl groups in Zn-containing nanosized MFI zeolite for the photocatalytic oxidation of methane.

Effective conversion of methane to a mixture of more valuable hydrocarbons and hydrogen under mild conditions is a great scientific and practical challenge. Here, we synthesized Zn-containing nanosized MFI zeolite for direct oxidation of methane in the presence of H2O and air. The presence of the surface hydroxyl groups on nanosized MFI-type zeolite and their significant reduction in the Zn-containing nanosized MFI zeolite were confirmed with Infrared Fourier Transform (FTIR) spectroscopy. Incorporation of zinc atoms into the framework of nanosized MFI zeolite is revealed by Nuclear Magnetic Resonance, X-ray Diffraction a UV-Vis Spectroscopy. Unexpectedly, pure silica MFI zeolite exhibited the highest photocatalytic performance. Our finds demonstrated that large number of isolated silanol groups and silanol nests increase the formation of •OH, and enhance the productivity of oxygenate compounds and C2H6, while the Zn incorporated into the zeolite framework or attached to the silanol nests of the nanosized zeolites are less efficient. A mechanism of photocatalytic methane oxidation is proposed. These findings provide insights into developing active nanosized zeolite photocatalysts with extended amount of surface hydroxyl groups that can play a key role in photocatalytic methane conversion.

Restructuring Ni/Al2O3 by addition of Ga to shift product selectivity in CO2 hydrogenation: The role of hydroxyl groups

Ni/Al2O3 is an active catalysts for CO2 hydrogenation to both CH4 and CO. By doping with Ga, we succeeded in shifting the selectivity of these catalysts almost completely toward CO. In-situ IR spectroscopy studies showed that the catalyst activity is directly related to the concentration of surface hydroxyl groups that are responsible for the adsorption of CO2 and the formation of intermediate bicarbonates and formates on the catalyst surface. The addition of Ga improved the Ni dispersion which was concomitant with the formation of a Ni-Ga layer on the surface of alumina, thereby reducing the surface hydroxyl concentration. The reduced and weakened interaction between the intermediate products, i.e. bicarbonates and formates, and the catalyst surface, increased the CO selectivity from ∼40 % to 98 %.

Insights into the role of hydroxyl group on carboxyl-modified MWCNTs in accelerating atenolol removal by Fe(III)/H2O2 system

The effects of multi-walled carbon nanotubes (MWCNTs) on the removal of contaminants mediated by Fenton reactions and how the functional groups on MWCNTs cooperate to modulate the cycling of Fe(III)/Fe(II) remain unclear. Here, we showed that MWCNTs significantly enhanced the removal of atenolol (ATL) in Fenton-like system by facilitating the generation of ·OH and O2·–, in which ·OH directly attacked ATL, while O2·– promoted the cycling of Fe(III)/Fe(II). Moreover, we found that in addition to –COOH, –OH on MWCNTs played an important role in ATL removal, that is, Fe(III) was likely to interact with –OH by H-bond and O–H···π interactions, which significantly reduced the reduction potential of Fe(III)/Fe(II), thus promoting the removal of ATL. Our findings revealed the role of –OH and –COOH on MWCNTs in promoting the removal of ATL in Fe(III)/H2O2 system, which is helpful to rationally design the CNTs-based materials applied for wastewater treatment.

Shaping Magnetite by Hydroxyl Group Numbers of Small Molecules.

Despite numerous reports on magnetite formation with the assistance of various additives, the role of hydroxyl group (-OH) numbers in small polyol molecules has not yet been understood well. We selected small molecules containing different -OH numbers, such as ethanol, ethylene glycol, propanetriol, butanetetrol, pentitol, hexanehexol, and cyclohexanehexol, as additives in coprecipitation. By increasing the -OH number in these small polyol molecules, the formation of crystallization was slowed, and the size and shape of magnetite were regulated as well possibly due to the changed complexation strength and the stability of the precursor. The increase in temperature and the Fe2+/Fe3+ ratio can reduce the complexation strength. The nucleation and growth of magnetite proceed possibly through the aggregation of polyol-stabilized amorphous complexes and two-line ferrihydrite with low crystallinity based on the -OH numbers, suggesting a nonclassical pathway. The as-prepared magnetite showed a r2/r1 ratio after in vitro MRI measurement as follows: Fe3O4@He-6OH rod < Fe3O4@Pr-3OH sheet < Fe3O4@Pe-5OH cube. The Fe3O4@He-6OH rod and Fe3O4@Pr-3OH sheet displayed T1-T2 dual modal contrast ability, while the Fe3O4@Pe-5OH cube can be T2-dominated. This research provides a simple but an essential approach for designing MRI contrast agents.

Role of Hydroxyl Groups in the Photophysics, Photostability, and (Opto)electronic Properties of the Fungi-Derived Pigment Xylindein

Organic semiconductors have attracted increasing attention due to their low cost, solution processability, and tunable properties. Of special interest are molecules with enhanced environmental stab...

Adsorptive removal of diclofenac sodium from aqueous solution by magnetic COF: Role of hydroxyl group on COF

Covalent organic frameworks (COFs) with great application potential in environmental remediation exist as the form of powder, which are difficult to separate and recycle. Two magnetic COFs with good recyclability were prepared through simple impregnation-precipitation method in this study. The prepared magnetic COFs were used for the adsorptive removal of diclofenac sodium (DCF). The introduction of hydroxyl group on magnetic COF (OH-MCOF) could greatly enhance its adsorption amount for DCF, and OH-MCOF was selected to study the effect of adsorption time, initial concentrations, solution pH and ionic strength on its adsorption for DCF, as well as its regeneration and reuse performance were investigated. In this study, the OH-MCOF had a high adsorption capacity for DCF of 203.4 mg/g based on the Langmuir model fitting, and exhibited quickly adsorption for DCF within 30 min. The adsorption efficiency was better than that of most reported adsorbents. Furthermore, the role of hydroxyl group on magnetic COF was highlighted through density functional theory (DFT) and electrostatic potential (ESP) calculation. After 5 cycles of regeneration, the OH-MCOF still maintained the same adsorption amount for DCF, showing good reusability and stability. This study reveals OH-MCOF with high removal and reusability in the further application of environmental remediation.

Investigating the Support Effect for Catalytic Elimination of Methyl Mercaptan: Role of Hydroxyl Groups over Cr-based Catalysts

The support effect for HZSM-5 and Al2O3-supported chromium (Cr) catalysts on the catalytic decomposition of methyl mercaptan (CH3SH) is investigated. Characterization results reveal that the distribution, reducibility, oxidation states and coordination environment of chromium species mightily depend on the nature of support. Al2O3 support is covered by surface hydroxyl groups, thus conducing to the formation of monochromatic Cr(VI) species with tetrahedral coordination, which remarkably increases the reducibility and dispersion of chromium species. In contrast, plenty of inactive α-Cr2O3 particles are formed on the surface of Cr/HZSM-5 catalyst due to the lack of adequate hydroxyl sites. Furthermore, a positive correlation is established between the content of active Cr(VI) species and the number of surface hydroxyl groups over Cr/Al2O3 catalysts. Reactivity data suggest that the addition of chromium species can observably enhance the conversion of CH3SH for both two supports. More importantly, 5% Cr/Al2O3 catalyst features the superior catalytic performance at 400 °C (100% conversion). The promoting effect can be attributed to the high-content hydroxyl groups on Al2O3, which are proven to stabilize monochromatic Cr(VI) species. This result also provides evidence for the active sites of CH3SH decomposition reaction.

Periodic DFT study of water adsorption on m-WO3(001), m-WO3(100), h-WO3(001) and h-WO3(100). Role of hydroxyl groups on the stability of polar hexagonal surfaces

Water adsorption on the (001) and (100) surfaces of monoclinic and hexagonal WO3 was studied using a periodic DFT approach. The results showed that dissociation of water on these surfaces is less energetically favourable than molecular adsorption and such phenomenon is a consequence of surface deformations induced by OH groups. Water interacted stronger with the five-fold tungsten atoms of the hexagonal surfaces than with those atoms of the monoclinic surfaces. Nevertheless, adsorption energies are almost the same between both hexagonal and monoclinic surfaces when all available active surface sites were occupied by water molecules, that is, at the maximum water coverage. On monoclinic surfaces, water adsorption gradually became less stable as the coverage increased, but the opposite behaviour was observed with dissociative adsorption. On the (001) surfaces of the hexagonal structures, both molecular and dissociative adsorption became less stable as water coverage increased. On the other hand, on the (100) surface, dissociation was only observed at the maximum coverage. All surfaces remain hydrated at low temperatures; whereas at higher temperatures the most stable structures are the clean surfaces. Lastly, the formation of a monolayer of OH groups on hexagonal surfaces helps to avoid distortion, which provides an explanation of why hexagonal surfaces are observed experimentally despite of being intrinsically unstable.

Chemical Composition and Evaluation of Antioxidant, Antimicrobial and Cytotoxic Activities of Moroccan Cladanthus mixtus Essential Oil and Extracts

The methanolic and deodorized aqueous extracts of the Moroccan Cladanthus mixtus collected from Bouznika were studied for its antioxidant, antimicrobial and cytotoxic activities. The essential oil was isolated by hydrodistillation and analyzed using GC/FID and GC/MS. The major component found was 2-methyl-2, trans-butenyl methacrylate (34 %). The essential oil showed good antioxidant activity for DPPH (IC50 =0.342±0.002 mg/mL) and a strong antimicrobial activity against all the tested microorganisms. Although, the deodorized aqueous extract had a high amount of phenols (38.2±0.4 mg GAE/g), it has shown no inhibiting effect against the growth of tested bacterial strains. The methanolic extract of C. mixtus which was characterized with higher flavonoid content (3.2 ±0.01 mg QE/g) was analyzed by the HPLC and showed the presence of gallic, vanillic, caffeic and syringic acids and catechin. For the methanolic extract, higher antioxidant activity was recorded than the deodorized aqueous extract using DPPH test (IC50 = 1.933 ± 0.048 mg/mL) and ABTS test (IC50 = 2.030 ± 0.006 mg/mL). The essential oil showed good cytotoxic activity with an IC50 = 85.27 μg/mL greater than that of the methanol extract (IC50 = 125.5 μg/mL). The apigenin (42 , 5, 7,-trihydroxyflavone), a natural compound, isolated for the first time from C. mixtus, showed a great cytotoxic activity (IC50 = 17.9 μg/mL). The 7, 4'-dipropargyl ether, a semi synthetic derivative of apigenin obtained by alkylation reaction of apigenin, showed a lower cytotoxic activity (IC50 = 88 μg/mL) than apigenin. This present study also elucidated the role of hydroxyl groups at positions C7 and C4’on the cytotoxic activity.

Role of hydroxyl group in cerium hydroxycinnamate on corrosion inhibition of mild steel in 0.6 M NaCl solution

The corrosion inhibition mechanism of cerium hydroxycinnamate compounds has been studied and compared as an effective corrosion inhibitor for steel in an aqueous 0.6 M NaCl solution. Surface analysis results showed that the surface of steel coupons exposed to solutions containing cerium hydroxycinnamate compounds has less signs of corrosion attack due to a formation of the protective film, while the surface of mild steel coupons exposed to 0.6 M chloride solution without inhibitor additions was severely corroded due to pitting. Electrochemical results performed a good inhibition performance and information of the formed protective deposit that hinders the electrochemical corrosion reactions with a dominance of anodic inhibition mechanism. The results also indicated that the addition of cerium hydroxycinnamate compounds to 0.6 M NaCl solution could mitigate electrochemical corrosion reactions, reduce protective and double layer CPE magnitudes, and improve protective and charge transfer resistances. Furthermore, cerium 2-hydroxycinnamate showed better efficient corrosion inhibitor in comparison with cerium 4-hydroxycinnamate for steel in aqueous media containing 0.6 M chloride ion.

Role of hydroxyl groups in the B-ring of flavonoids in stabilization of the Hoogsteen paired third strand of Poly(U).Poly(A)*Poly(U) triplex

We have reported the interaction of two flavonoids namely quercetin (Q) and morin (M) with double stranded poly(A).poly(U) (herein after A.U) and triple stranded poly(U).poly(A)*poly(U) (herein after U.A*U, dot represents the Watson–Crick and asterisk represents Hoogsteen base pairing respectively) in this article. It has been observed that relative positions of hydroxyl groups on the B-ring of the flavonoids affect the stabilization of RNA. The double strand as well as the triple strand of RNA-polymers become more stabilized in presence of Q, however both the duplex and triplex remain unaffected in presence of M. The presence of catechol moiety on the B-ring of Q is supposed to be responsible for the stabilization. Moreover, after exploiting a series of biophysical experiments, it has been found that, triple helical RNA becomes more stabilized over its parent duplex in presence of Q. Fluorescence quenching, viscosity measurement and helix melting results establish the fact that Q binds with both forms of RNA through the mode of intercalation while M does not bind at all to either forms of RNA.

Insight into the role of hydroxyl groups on the ZnCr catalyst for isobutanol synthesis from syngas

A series of ZnO, ZnCr catalysts were prepared by a sol-gel method and ammonia solution was used to adjust the pH of the sol solution. The catalysts were characterized by XRD, in-situ FR-IR, NH3-TPD, in-situ XPS, HRTEM. The results show that lower calcination temperature is helpful to reduce the crystal size and crystallinity of ZnCr nanocrystal, as well as forming a certain amount of structure defects and hydroxyl groups. The hydroxyl groups could be consumed by CO under the interaction between ZnO and ZnCr spinel, resulting in more exposed oxygen vacancies. We find the proper calcination temperature and Zn/Cr molar ratio for the ZnCr catalysts preparation are 400°C and 1.0, respectively. The Zn1Cr1–400∼2.0 catalyst prepared with the pH value of 2 shows more hydroxyl groups and small particle size, exhibiting the best catalytic performance both on the CO conversion (20.9%) and isobutanol selectivity (24.2wt%).

Roles of Hydroxyl Groups During Side‐Chain Alkylation of Toluene with Methanol over Zeolite Na‐Y: A Density Functional Theory Study

AbstractThe side‐chain alkylation of toluene with methanol over alkali‐cation‐containing zeolite Y is an important reaction for industrial production of styrene, but the exact mechanism of this reaction is still unclear. The most accepted opinion is that the Lewis acid–base sites in zeolite Y activate the transformation from methanol to formaldehyde, the side‐chain alkylation of toluene with formaldehyde, and the formation of 2‐phenylethanol and styrene afterwards. In this study, we investigate the roles of various types of hydroxyl groups that could possibly exist in zeolite Na‐Y during this reaction, including the Brönsted acid sites and the terminal Al—OH and Si—OH groups, respectively. Through density functional theory (DFT) calculations, we find that the Brönsted acid sites in Na‐Y may catalyze the ring alkylation of toluene and be responsible for the formation of xylene, a side product discovered in experiments. More importantly, we find, for the first time, a new reaction pathway from 2‐phenylethanol to styrene over various types of hydroxyl groups in Na‐Y, which is kinetically more favorable than the conventional pathway. According to our calculation results, the most possible mechanism for this styrene production process may involve reactions over both the Lewis acid–base sites and the hydroxyl groups in Na‐Y.

Role of Hydroxyl Group in Cerium Hydroxycinnamate Compounds in Enhancing the Corrosion Resistance of Mild Steel in Chloride Ion Media

The role of hydroxyl group in cerium hydroxycinnamate compounds has been studied as an effective corrosion inhibitor for mild steel in 0.6 M chloride solution. The results show that the surfaces of mild steel coupons exposed to solutions containing inhibitors had no signs of corrosion attack due to protective film formation, whereas the surface of mild steel coupons exposed to non-inhibitor containing solutions was severely corroded. Cerium hydroxycinnamate compounds showed as a better inhibitor for AS1020 steel at higher concentration. The addition of Cerium hydroxycinnamate compounds form protective film layer and improves the protective film and charge transfer resistance which plays an importance role in corrosion properties. A high inhibition performance is attributed to the forming protective inhibiting deposits that slow down the electrochemical corrosion reactions. The results also indicated that the position of hydroxyl group in cerium hydroxycinnamate significantly effect to the inhibition performance of mild steel in chloride ion media.

Hydroconversion of C18 fatty acids using PtNi/Al2O3: Insight in the role of hydroxyl groups in Al2O3

The catalytic hydroconversion of C18 fatty acids over PtNi/Al2O3 catalysts was investigated to explore the role of hydroxyls in Al2O3 on the catalytic activity. The amount of hydroxyls in acidic Al2O3 was 2.5 times that in neutral Al2O3 but with the same acidity. High content of hydroxyl in Al2O3 increased the NiPt-Al2O3 interaction and differed the Pt valence distribution. The NiPt/acidic Al2O3 catalyst showed 56% DCO2 while the Ni-Pt/neutral Al2O3 catalyst showed 58% DCO products due to the different NiPt-Al2O3 interaction. The high amount of Pt4+ species in NiPt alloy contributed to the high selectivity of DCO2 reaction.

The role of hydroxyl groups in interchain interactions in cellulose Iα and Iβ

AbstractComplex networks of hydrogen bonds within the cellulose Iα and Iβ contribute greatly to cellulose's anisotropic physical properties such as material stiffness. The interchain hydrogen bonding interactions through hydroxyl groups are isolated in each of the three lattice planes of the adjacent chains within the unit cell of two allomorphs of natural cellulose. In our density function theory study with dispersion corrected Perdew–Burke–Ernzerhof (PBE‐D2) functional, these hydroxyl groups participate in strong hydrogen bonding interactions (−24.8 and −24.8 kcal/mol for cellulose Iα and Iβ, respectively) in the side‐to‐side lattice plane. Unexpectedly, the hydroxyl groups also participate significantly in hydrogen bonding interactions (−11.0 and −12.4 kcal/mol for cellulose Iα and Iβ, respectively) in one of the diagonal lattice planes in both cellulose Iα and Iβ. Both PM7 and PBE‐D2 method predict that the overall interaction is asymmetric and stronger in the right diagonal lattice plane. While hydrogen bonding interactions are strongest in side‐to‐side lattice plane as expected, the role of hydrogen bonding interactions for keeping the sheet together is more significant than previously thought.

Molecular dynamics study on the role of hydroxyl groups in heat conduction in liquid alcohols

On the basis of non-equilibrium molecular dynamics (NEMD) simulation for alcohols from ethanol to tetracosanol, the present study analyzes the molecular-level energy transfer in associated liquids for the first time. Direct evaluation of the energy transfer by each interatomic interaction reveals a counterintuitive result that in liquid alcohols the Coulomb interaction does not transfer heat more than the van der Waals interaction even for short chain species like ethanol. In addition, by comparing the NEMD analysis on alcohols with those of alkanes, we discuss a molecular mechanism by which alcohol has a higher thermal conductivity than alkane in view of molecular heat transfer. It is shown that hydroxyl OH, not only provides heat paths for the Coulomb interaction, but also increases the number of heat paths for the vdW and the intramolecular interactions. Consequently, the part of the heat transfer by the vdW interaction is replaced with more efficient transfers by the Coulomb and intramolecular interactions, and therefore a higher thermal conductivity occurs. The insights obtained from the present study update the view of microscopic heat transfer in associated liquid towards the molecular theory of thermal conductivity of liquids, which is currently immature in comparison with those of gases and solids.

LINE-1 gene hypomethylation and p16 gene hypermethylation in HepG2 cells induced by low-dose and long-term triclosan exposure: The role of hydroxyl group

Triclosan (TCS), a frequently used antimicrobial agent in pharmaceuticals and personal care products, exerts liver tumor promoter activities in mice. Previous work showed high-dose TCS (1.25–10μM) induced global DNA hypomethylation in HepG2 cells. However, whether or how tumor suppressor gene methylation changed in HepG2 cells after low-dose and long-term TCS exposure is still unknown. We investigate here the effects and mechanisms of DNA methylation of global DNA(GDM), repetitive genes, and liver tumor suppressor gene (p16) after exposing HepG2 cells to low-dose TCS (0.625–5nM)for two weeks using HPLC–MS/MS, Methylight, Q-MSP, Pyrosequencing, and Massarray methods. We found that low-dose TCS exposure decreased repetitive elements LINE-1 methylation levels, but not global DNA methylation, through down-regulating DNMT1 (DNA methyltransferase 1) and MeCP2 (methylated DNA binding domain) expression, and up-regulating 8-hydroxy-2-deoxyguanosine (8-OHdG) levels. Interestingly, low-dose TCS elevated p16 gene methylation and inhibited p16 expression, which were not observed in high-dose (10μM) group. Meanwhile, methyl-triclosan could not induce these two types of DNA methylation changes, suggesting the involvement of hydroxyl in TCS-mediated DNA methylation changes. Collectively, our results suggested low concentrations of TCS adversely affected HepG2 cells through DNA methylation dysregulation, and hydroxyl group in TCS played an important role in the effects. This study provided a better understanding on hepatotoxicity of TCS at environmentally relevant concentrations through epigenetic pathway.

Role of Hydroxyl Groups in the Preferential Oxidation of CO over Copper Oxide–Cerium Oxide Catalysts

Model CuO/Ce0.8X0.2Oδ catalysts (with X = Ce, Zr, La, Pr, or Nd) have been prepared in order to obtain CuO/ceria materials with different chemical features and have been characterized by X-ray diffraction, Raman spectroscopy, N2 adsorption, and H2 temperature-programmed reduction. CO-PROX experiments have been performed in a fixed-bed reactor and in an operando DRIFTS cell coupled to a mass spectrometer. The CO oxidation rate over CuO/ceria catalysts correlates with the formation of the Cu+–CO carbonyl above a critical temperature (90 °C for the experimental conditions in this study) because copper–carbonyl formation is the rate-limiting step. Above this temperature, CO oxidation capacity depends on the redox properties of the catalyst. However, decomposition of adsorbed intermediates is the slowest step below this threshold temperature. The hydroxyl groups on the catalyst surface play a key role in determining the nature of the carbon-based intermediates formed upon CO chemisorption and oxidation. Hydroxyls favor the formation of bicarbonates with respect to carbonates, and catalysts forming more bicarbonates produce faster CO oxidation rates than those which favor carbonates.