Multiple Active Centers Research Articles

High catalytic performance of an innovative Ni/magnesium slag catalyst for the syngas production and tar removal from biomass pyrolysis

The study aims to evaluate the catalytic potential of a Ni-based catalyst supported by magnesium slag (MS) for catalytic reforming of pyrolysis volatiles from pine sawdust. The catalysts were prepared by a wet impregnation method. The effects of different parameters (Ni loading content, calcination/catalytic bed temperature and steam to carbon (S/C) ratio) on the catalytic performance were investigated. In addition, tar cracking capability and coke deposition resistance of Ni/MS catalyst and Ni/γ-Al2O3 catalyst were explored under different calcination/catalytic bed temperatures. The catalysts were characterized by BET, XRD, SEM, TEM, TPO and Raman spectroscopy. The Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability. The best tar conversion (95.69%) and the highest hydrogen yield of 38.9 mmol/g biomass were obtained over Ni/MS catalyst under the conditions of Ni loading content = 3%, calcination/catalytic bed temperature = 800 °C, and S/C = 0.5. The interactions among Ni, Fe, Ca, and Mg formed multiple active centers (e.g., Ca2Fe2O5, (Ni, Mg) O solid solution and NiFe2O4) in the catalyst to show synergistic catalysis effects, thereby jointly improving catalyst activity and coke deposition resistance. Furthermore, both amorphous carbon and graphitic carbon were formed on the used catalysts and the D/G ratio (the relative intensity ratio between the D and G bands) was positively correlated with the catalytic activity.

Cooperative Catalysis by Multiple Active Centers of a Half-Titanocene Catalyst Integrated in Polymer Random Coils

To study cooperative catalysis in ethylene polymerization, a series of polynorbornene (PNB)-supported half-titanocene catalysts were synthesized by grafting a half-titanocene complex to monodispers...

Nanosheet-like Ni-based metasilicate towards the regulated catalytic activity in styrene oxidation via introducing heteroatom metal

Multiple catalytic active centers tactically generated on the 2-dimentional catalytic carrier could afford certain promoting function thanks to their existed special synergy. Herein, Ni-based nanosheet-like metasilicate catalytic materials were developed as heterogeneous catalysts towards styrene oxidation for the first time. Concurrently, the special heteroatom cobalt or magnesium-incorporated Ni-based nanosheet-like metasilicate were developed together via the proposed synthesis tactics. The resulted sheet-like nanomaterials were meticulously characterized and identified through valid techniques. The introduction of heteroatom metal elements of cobalt or magnesium incorporated in the Ni-based nanosheet-like metasilicate was proven to trigger the regulated catalytic effect including positive and negative aspects towards styrene oxidation, and their function was identified and understood based on the reaction exploration results, in which the present cobalt significantly give rise to the promotive catalytic conversion activity and selectivity towards styreneoxide(conversion 96.8%, selectivity 78.4%), while the magnesium oppositely induced the restraining catalytic capacity(conversion 72%, selectivity 51.3%) on the Ni-based metasilicate compared with pure one. The obtained heterogeneous Ni-based metasilicate retain durable catalytic activity during five recycling for styrene oxidation and inherit the regulated catalytic performance in the substrate expansion.

Development of aluminum and zirconium based xerogel for defluoridation of drinking water: Study of material properties, solution kinetics and thermodynamics

The present investigation reports the preparation and defluoridation efficiency of Al2O3/ZrO2 xerogel. The material was prepared by environment friendly sol-gel technique using respective metal salts as precursors. FTIR spectra indicated presence of bridged structure (Zr – O – Al) in the material and decrease in intensity of hydroxyl group vibration indicates substitution of surface hydroxyl groups by fluoride through formation of metal – fluoride bonding. The XRD of material showed amorphous characteristics of Al2O3/ZrO2. The morphological feature of the material indicate presence of micro-pore in the structure and the total specific surface area (m2 g−1) and average pore radius (nm) were calculated to be 3.68 and 1736.6, respectively. The molecular interaction/bonding between aluminum-zirconium contributed in enhancing the stability of the material, whereas, the kinetics of thermal degradation pattern is heterogeneous in characteristics. Al2O3/ZrO2 shows almost 98% fluoride removal efficiency where the material-anions equilibrium was reached within 20 min time interval. Fluoride adsorption characteristics was found to be pH dependent influenced by pore diffusion, where the presence of multiple active centers, i.e., Al and Zr in Al2O3/ZrO2 favors fluoride sorption in comparison to ZrO2 xerogel. Fluoride adsorption follows a pseudo-second order kinetic as well as intra-particle diffusion model with almost ≥ 0.99 accuracy. The thermodynamics of fluoride adsorption was found to be spontaneous and exothermic in nature. The adsorbent shows good regeneration efficiency up to 5th cycles of continuous operation with very little effect of co-anions that can be helpful for its sustainable commercial applications.

Interface self-assembly preparation of multi-element doped carbon nanobowls with high electrocatalysis activity for oxygen reduction reaction

Developing an efficient, stable and low cost oxygen reduction reaction electrocatalyst is desirable for fuel cells and metal-air batteries. Here, we have successfully prepared multi-element doped carbon nanobowls by simply mixing the porous carbon nanobowls and sulfur doped graphitic carbon nitride quantum dots in FeCl3 solution and subsequent high temperature treatment processes. Compared with the commercial Pt/C electrocatalyst, the multi-element doped carbon nanobowls display a comparable half-wave potential of 0.82 V, much larger limiting diffusion current density (0.4–0.8 V), better methanol-tolerance and higher long-term stability for the oxygen reduction reaction in alkaline media. The robust three-dimensional porous structure of carbon nanobowls and multiple active centers derived from Fe, N, S and O co-doping are responsible for the excellent performance. This work suggests that such multi-element doped carbon nanobowls can be a promising alternative for Pt-based catalysts in fuel cells.

Cobalt-cadmium bimetallic porphyrin coordination polymers for electrochemistry application

In this paper, we used tetra (4-carboxyphenyl) porphyrin (H2TCPP) and metal cadmium, cobalt as reactants to synthesize metal porphyrin coordination polymers that they had different metal ratio. They were expressed as Co1Cd3TCPP, Co1Cd1TCPP, Co3Cd1TCPP, respectively. The results were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and inductively coupled plasma atomic emission spectrometer (ICP). Herein, a series of metal porphyrin coordination polymers has multiple metal active centers and constructs electrochemistry sensors. In order to increase the conductivity, multi-walled carbon nanotubes (MWCNTs) can be used to modify the electrodes. The polymer/MWCNTs/GCE electrode was studied by cyclic voltammetry and chronoamperometry as sensor for sodium nitrite. The performance of Co1Cd1TCPP/MWCNTs/GCE electrode is best, the sensitivity for sodium nitrite is 350.95 mA M-1 cm-2 and the. The results indicate that metal porphyrin coordination polymers have excellent performance. It also enriches the application of metal porphyrin coordination polymer in electrochemistry sensor.

Specific Surface versus Electrochemically Active Area of the Carbon/Polypyrrole Capacitor: Correlation of Ion Dynamics Studied by an Electrochemical Quartz Crystal Microbalance with BET Surface.

Carbon/polypyrrole (PPy) composites are promising electrode materials for energy storage applications such as lightweight capacitors. Although these materials are composed of relatively inexpensive components, there is a gap of knowledge regarding the correlation between surface, porosity, ion exchange dynamics, and the interplay of the double layer capacitance and pseudocapacitance. In this work we evaluate the specific surface area analyzed by the BET method and the area accessible for ions using electrochemical quartz-crystal microbalance (EQCM) for SWCNT/PPy and carbon black Vulcan XC72-R/PPy composites. The study revealed that the polymer has significant influence on the pore size of the composites. Although the BET surface is low for the polypyrrole, the electrode mass change and thus the electrochemical area are large for the polymer-containing electrodes. This indicates that multiple redox active centers in the charged polymer chain are good ion scavengers. Also, for the composite electrodes, the effective charge storage occurs at the polypyrrole-carbon junctions, which are easy to design/multiply by a proper carbon-to-polymer weight ratio. The specific BET surface and electrochemically accessible surface area are both important parameters in calculation of the electrode capacitance. SWCNTs/PPy showed the highest capacitances normalized to the BET and electrochemical surface as compared to the polymer-carbon black. TEM imaging revealed very homogeneous distribution of the nanosized polymer particles onto the CNTs, which facilitates the synergistic effect of the double layer capacitance (CNTs) and pseudocapacitance (polymer). The trend in the electrode mass change in correlation with the capacitance suggest additional effects such as a solvent co-insertion into the polymer and the contribution of the charge associated with the redox activity of oxygen-containing functional groups on the carbon surface.

Home range and habitat use of juvenile green turtles (Chelonia mydas) in the northern Gulf of Mexico

For imperiled marine turtles, use of satellite telemetry has proven to be an effective method in determining long distance movements. However, the large size of the tag, relatively high cost and low spatial resolution of this method make it more difficult to examine fine-scale movements of individuals, particularly at foraging grounds where animals are frequently submerged. Acoustic telemetry offers a more suitable method of assessing fine-scale movement patterns with a smaller tag that provides more precise locations. We used acoustic telemetry to define home ranges and describe habitat use of juvenile green turtles at a temperate foraging ground in the northern Gulf of Mexico. We outfitted eight juvenile green turtles with acoustic transmitters and tracked them from 14 to 138 days from September 2012 to February 2013 in St. Joseph Bay, Northwest Florida. Mean home range size was relatively small compared to other studies. For four turtles, we observed a moderate inverse relationship between water temperature and water depth which is consistent with the idea that turtles moved to deeper waters when temperatures cooled. On average distance to the channel from turtle locations were different by bottom cover type. These turtles appear to forage in shallow-water seagrass beds that border deep channels. When water temperatures dropped in winter, some of the tracked turtles moved to a deep-water channel on the western side of the study site. Turtles whose foraging sites were farther from the deep-water channel exhibited greater displacement than those with sites that were closer to the channel. Green turtles in St. Joseph Bay have relatively small home ranges and many contain multiple activity centers. The frequent use of channels by turtles suggests bathymetry plays a major role in habitat selection of juvenile green turtles, particularly as temperatures drop in winter. The quality and density of seagrass habitat in St. Joseph Bay and its proximity to deep channels appears to provide ideal conditions for juvenile greens. The results of this study help define characteristics of foraging habitat utilized by juvenile greens in the northern Gulf of Mexico that managers can use in creating protected areas such as aquatic preserves.

Depression and Psychosocial Risk Factors among Community-Dwelling Older Adults in Singapore.

Depression is the most common mental and emotional disorder that emerges in the late stages of life. It is closely associated with poor health, disability, mortality, and suicide. The study examines the risk factors of depression in late life, especially the psychosocial factors, among a sample comprising 162 community-dwelling Singaporean adults aged 65 years and above. An interview-based structured survey was conducted in multiple senior activity centers located in different parts of Singapore. Results from the hierarchical regression analysis show that 32.9% of the variance in geriatric depression can be explained by the three psychosocial factors, among which loneliness, perceived social support, and the emotional regulation component of resilience are significantly associated with depression in older adults. Large-scale studies should be conducted to confirm the findings of the present study, and to further examine the predictive effects of these psychosocial factors on depression among older adults.

Multinuclear group 4 catalysis: olefin polymerization pathways modified by strong metal-metal cooperative effects.

Polyolefins are produced today catalytically on a vast scale, and the manufactured polymers find use in everything from artificial limbs and food/medical packaging to automotive and electrical components and lubricants. Although polyolefin monomers are typically cheap (e.g., ethylene, propylene, α-olefins), the resulting polymer properties can be dramatically tuned by the particular polymerization catalyst employed, and reflect a rich interplay of macromolecular chemistry, materials science, and physics. For example, linear low-density polyethylene (LLDPE), produced by copolymerization of ethylene with linear α-olefin comonomers such as 1-butene, 1-hexene, or 1-octene, has small but significant levels of short alkyl branches (C2, C4, C6) along the polyethylene backbone, and is an important technology material due to outstanding rheological and mechanical properties. In 2013, the total world polyolefin production was approximately 211 million metric tons, of which about 11% was LLDPE. Historically, polyolefins were produced using ill-defined but highly active heterogeneous catalysts composed of supported groups 4 or 6 species (usually halides) activated by aluminum alkyls. In 1963, Karl Ziegler and Giulio Natta received the Nobel Prize for these discoveries. Beginning in the late 1980s, a new generation of group 4 molecule-based homogeneous olefin polymerization catalysts emerged from discoveries by Walter Kaminsky, a team led by James Stevens at The Dow Chemical Company, this Laboratory at Northwestern University, and a host of talented groups in Germany, Italy, Japan, the United Kingdom, and the United States. These new "single-site" catalysts and their activating cocatalysts were far better defined and more rationally tunable in terms of structure, mechanism, thermodynamics, and catalyst activity and selectivity than ever before possible. An explosion of research advances led to new catalysts, cocatalysts, deeper mechanistic understanding of both the homogeneous and heterogeneous systems, macromolecules with dramatically altered properties, and large-scale industrial processes. It is noteworthy that many metalloenzymes employ multiple active centers operating in close synergistic proximity to achieve high activity and selectivity. Such enzymes were the inspiration for the research discussed in this Account, focused on the properties of multimetallic olefin polymerization catalysts. Here we discuss how modifications in organic ligand architecture, metal···metal proximity, and cocatalyst can dramatically modify polyolefin molecular weight, branch structure, and selectively for olefinic comonomer enchainment. We first discuss bimetallic catalysts with identical group 4 metal centers and then heterobimetallic systems with either group 4 or groups 4 + 6 catalytic centers. We compare and contrast the polymerization properties of the bimetallic catalysts with their monometallic analogues, highlighting marked cooperative enchainment effects and unusual polymeric products possible via the proximate catalytic centers. Such multinuclear olefin polymerization catalysts exhibit the following distinctive features: (1) unprecedented levels of polyolefin branching; (2) enhanced enchainment selectivity for linear and encumbered α-olefin comonomers; (3) enhanced polyolefin tacticity and molecular weight; (4) unusual 1,2-insertion regiochemistry for styrenic monomers; (5) modified chain transfer kinetics, such as M-polymer β-hydride transfer to the metal or incoming monomer; (6) LLDPE synthesis with a single binuclear catalyst and ethylene.

Location-Dominant Housing Markets: Evidence from Beijing

This paper analyzes price tradeoffs between residential quality and location factors in the Beijing housing market. Unlike most housing markets, location factors completely dominate housing prices in this market. The main reason for this appears to be the physical size of central Beijing, where travel times between different urban activity centers are comparable to typical suburban-urban commuting times in large Western cities. To highlight these location-dominance effects, we present a comparative analysis of housing prices in central Beijing with those of the relatively smaller monocentric city of Qingdao in Eastern China. The main results of this regression analysis are to show that location accessibility factors are far more dominant in Beijing, and conversely that residential quality factors are more important in Qingdao. To further illuminate these differences, we develop a simple two-city model in which the “Big” city has multiple activity centers with travel costs comparable to typical commuting costs in the “Small” city. Here it is shown that the resulting bid-price relations between these cities are quite consistent with our empirical findings.

De Novo Design of an Artificial Bis[4Fe-4S] Binding Protein

In nature, protein subunits containing multiple iron-sulfur clusters often mediate the delivery of reducing equivalents from metabolic pathways to the active site of redox proteins. The de novo design of redox active proteins should include the engineering of a conduit for the delivery of electrons to and from the active site, in which multiple redox active centers are arranged in a controlled manner. Here, we describe a designed three-helix protein, DSD-bis[4Fe-4S], that coordinates two iron-sulfur clusters within its hydrophobic core. The design exploits the pseudo two-fold symmetry of the protein scaffold, DSD, which is a homodimeric three-helix bundle. Starting from the sequence of the parent peptide, we mutated eight leucine residues per dimer in the hydrophobic core to cysteine to provide the first coordination sphere for cubane-type iron-sulfur clusters. Incorporation of two clusters per dimer is readily achieved by in situ reconstitution and imparts increased stability to thermal denaturation compared to that of the apo form of the peptide as assessed by circular dichroism-monitored thermal denaturation. The presence of [4Fe-4S] clusters in intact proteins is confirmed by UV-vis spectroscopy, gel filtration, analytical ultracentrifugation, and electron paramagnetic resonance spectroscopy. Pulsed electron-electron double-resonance experiments have detected a magnetic dipole interaction between the two clusters ~0.7 MHz, which is consistent with the expected intercluster distance of 29-34 Å. Taken together, our data demonstrate the successful design of an artificial multi-iron-sulfur cluster protein with evidence of cluster-cluster interaction. The design principles implemented here can be extended to the design of multicluster molecular wires.

N-doped carbon synthesized from N-containing polymers as metal-free catalysts for the oxygen reduction under alkaline conditions

Nitrogen-doped carbon materials were synthesized and used as metal-free electrocatalysts for the oxygen reduction reaction (ORR) under alkaline conditions. The synthesis was achieved by thermal treatment of nitrogen-containing polymers diluted in different carbon materials. Polypyrrole, polyaniline and polyacrylonitrile were used as N precursors. Carbon black and two types of commercial carbon nanotubes were used as carbon matrices. The obtained N contents were in the range of 1–1.8wt.%. Different N species including pyridinic, pyrrolic and quaternary N were quantitatively determined by X-ray photoelectron spectroscopy. The ORR activities were evaluated in 0.1M KOH. Rotating disc electrode studies revealed the presence of multiple active centers in all the samples. The sample obtained using polypyrrole and small diameter nanotubes (ca. 15nm) had the highest onset potential at −0.07V vs. Ag/AgCl/3M KCl, which also showed a significantly higher electrochemical stability than the sample from carbon black and polypyrrole. The ORR activity was not correlated to the total nitrogen amount, but to the amount of pyridinic and quaternary N species. For the onset potential and the (Npyridinic+Nquaternary)/Ntotal ratio a quasi-linear relation was found, which points to the substantial role of pyridinic- and quaternary-N species in ORR catalysis.

The activity-based aggregate production planning with capacity expansion in manufacturing systems

This paper builds a mixed integer linear programming (MILP) model to mathematically characterize the problem of aggregate production planning (APP) with capacity expansion in a manufacturing system including multiple activity centers. We use the heuristic based on capacity shifting with linear relaxation to solve the model. Two linear relaxations, i.e., a complete linear relaxation ( CLR) on all the integer variables and a partial linear relaxation ( PLR) on part of the integer variables are investigated and compared in computational experiments. The computational results show that the heuristic based on the capacity shifting with CLR is very fast but yields low-quality solution whereas the capacity shifting with PLR provides high-quality solutions but at the cost of considerable computational time. As a result, we develop a hybrid heuristic combining beam search with capacity shifting, which is capable of producing a high-quality solution within reasonable computational time. The computational experiment on large-scale problems suggests that when solving a practical activity-based APP model with capacity expansion at the industrial level, the capacity shifting with CLR is preferable, and the beam search heuristic could be subsequently utilized as an alternative if the relaxation gap is larger than the acceptable deviation.

Ultrabroad NIR luminescence and energy transfer in Bi and Er/Bi co-doped germanate glasses

The effects of temperature, pump power and excitation wavelength on near-infrared photoluminescence from Bi-doped multi-component germanate glasses are presented. Compared to conventional silica/silicate matrices, the examined material exhibits superior resistance to thermal quenching and less pronounced excited state absorption for pumping at 808 nm. It is shown that by selecting the optimal excitation wavelength, photoemission can be initiated from multiple active centers in parallel, resulting in an emission bandwidth (full width at half maximum) of more than 370 nm. Er3+/Bi co-doping is presented as an effective means to significantly enhance emission intensity around 1.5 μm by suppressing the typical Er3+-related red-to-green upconversion. Besides its relevance for Bi-doped materials, this also indicates a new route towards improving the performance of Er-based optical devices. The mechanism of Er3+→Bi energy transfer is examined in detail. Adjusting the molar ratio between both species provides an effective tool for tuning the emission scheme and further increasing emission bandwidth.

Simultaneous Tailoring of Phase Evolution and Dopant Distribution in the Glassy Phase for Controllable Luminescence

Construction of an active composite with multicolor visible and broadband near-infrared luminescence is of great technological importance for various applications, including three-dimensional (3D) display, broadband telecommunication, and tunable lasers. The major challenge is the effective management of energy transfer between different dopants in composite. Here we present an in situ strategy for controlling energy transfer between multiple active centers via simultaneous tailoring of the evolution of phases and the distribution of dopants in the glassy phase. We show that the orderly precipitation of Ga(2)O(3) and LaF(3) nanocrystals and the selective incorporation of Ni(2+) and Er(3+) into them can be achieved. The obtained composite shows unique multicolor visible and broadband near-infrared emission. Possible mechanisms for the selective doping phenomenon are proposed, based on thorough structural and optical characterizations and crystal-field calculation results. Moreover, the strategy can be successfully extended to accomplish space-selective control of multicolor luminescence by employing the modulated stimulation field. The results suggest that the strategy could be applied to fabricate a multifunctional light source with a broad range of important host/activator combinations and to construct various types of three-dimensional active microstructures.

Laser-Induced Optical Property Changes Inside Bi-Doped Glass

We report an unusual phenomenon of optical properties changes in Bi-doped glass under irradiation with a femtosecond laser. Not only broadband absorption in the visible but also infrared luminescence variations have been observed after irradiation. This behavior is related to the process of laser initiating local chemical reactions involving multiple active centers of Bi. This phenomenon provides a convenient method for 3-D selective fabrication by ultrashort laser pulses, and applications in ultrahigh density optical memory and micro photonics.

Space-selective control of luminescence inside the Bi-doped mesoporous silica glass by a femtosecond laser

A novel method for space-selective fabrication of an active multifunctional light source is presented here. The ultra-short laser pulse is employed to induce multiple active centers of bismuth in an interesting “tolerant” host—mesoporous silica glass—which is used to stabilize these localized unusual emission centers. The Bi2+ and multiple Bi+ centers acquired show tunable and ultra-broadband luminescence covering the region from red to near-infrared.

Ethylene Polymerization over Homogeneous and Supported Catalysts Based on Bis(imino)pyridine Co(II) Complex: Data on the Number of Active Centers and Propagation Rate Constant

The number of active centers (CP) and propagation rate constant (kP) for ethylene polymerization with homogeneous catalyst LCoCl2 + MAO and supported catalyst LCoCl2/SiO2 + Al(i-Bu)3, where L is 2,6-(2,6-(Me)2C6H3N = CMe)2C5H3N, have been determined using the method of polymerization quenching by radioactive carbon monoxide (14CO). The unstable rate profile of the reaction was attributed to a decrease in the number of active centers from 0.23 to 0.14 mol · mol−1(Co) corresponding to an increase in the reaction time from 5 to 15 min, whereas the kP value remained constant, amounting to 3.5 × 103 L · mol−1 · s at 35 °C. A narrow molecular weight distribution of the obtained polyethylene (PE) samples ( = 1.9) testifies that the homogeneous catalyst LCoCl2 + MAO can be regarded as a single-site system. The activity of the supported catalyst was stable and noticeably lower than that of the homogeneous catalyst due to the low concentration of the active centers (0.02–0.03 mol · mol−1(Co)). PE with a broad molecular weight distribution ( = 36) and noticeably higher molecular weight is formed in the presence of the supported catalysts. The activity of the supported catalyst increases sharply at polymerization in the presence of hydrogen. The data obtained on the CP and kP values allow suggesting the formation of the “dormant” centers at polymerization without hydrogen and regeneration of the active centers in the presence of hydrogen. The average kP values for the supported catalyst containing multiple active centers were determined to be 5.9 × 103 and 10.5 × 103 L · mol−1 · s, respectively, at 35 and 50 °C.

Reactivity of polyester aliphatic amine surfactants as corrosion inhibitors for carbon steel in formation water (deep well water)

Effect of different concentrations, 40–200 ppm, of various polyester aliphatic amine surfactants on inhibition of the corrosion of carbon steel in the formation water (deep well water) was investigated. These surfactants exhibit different levels of inhibition particularly at high concentration (200 ppm). Inhibition efficiencies in the range 86–96% were determined by weight loss method. Comparable results were obtained from electrochemical measurements using Tafel extrapolation and polarisation resistance methods. It was shown that all the investigated surfactants act primarily as anodic inhibitors; however, they also affect the rate and mechanism of the cathodic reaction. These compounds function via adsorption on reactive sites on the corroding surface reducing the corrosion rate of the metal. It was revealed that the adsorption of these surfactants obey Langmuir adsorption isotherm. The inhibition effectiveness increases with the length of the aliphatic hydrocarbon chain, being a maximum in the presence of surfactant IV (∼96% efficiency). The corrosion inhibition feature of this compound is attributed to the presence of a long hydrocarbon chain that ensures large surface coverage as well as the presence of multiple active centers for adsorption. Scanning electron microscopy, SEM, has been applied to identify the surface morphology of carbon steel alloy in the absence and presence of the inhibitor molecules.