Adsorption Of Sulfur Compounds Research Articles

Supported Noble Metal Catalysts and Adsorbents with Soft Lewis Acid Functions.

Heterogeneous noble metal catalysts exhibit various functions. Although their redox functions have been extensively studied, we focused on their soft Lewis acid functions. Supported Au, Pt, and Pd catalysts electrophilically attack the π-electrons of soft bases such as alkynes, alkenes, and aromatic compounds to perform addition and substitution reactions. Hydroamination, intramolecular cyclization of alkynyl carboxylic acids, isomerization of allylic esters, vinyl exchange reactions, Wacker oxidation, and oxidative homocoupling of aromatics are introduced based on a discussion of the active species and reaction mechanisms. Furthermore, the adsorption of sulfur compounds, which are soft bases, onto the supported AuNPs is discussed. The adsorption and removal of 1,3-dimethyltrisulfane (DMTS), which is the compound responsible for the stale odor of "hine-ka" in alcoholic beverages, particularly Japanese sake, is described.

Desulphurization mechanism and engineering practice of carbide slag.

In order to give full play to the alkaline neutralization value of carbide slag and reduce the environmental hazards of carbide slag, it is of great practical significance to study the resource utilization of carbide slag. The adsorption of sulfur compounds on carbide slag was studied in the laboratory, and the process parameters of carbide slag desulfurization were explored and optimized. The specific surface area, pore distribution, and other physicochemical parameters were analyzed by XRD and SEM, which explained the changes of products and carbide slag before and after desulfurization. The test results show that carbide slag and limestone have almost the same desulfurization effect. The kinetics of carbide slag desulfurization process conforms to pseudo-first-order kinetics, and the sulfur content of calcium carbide slag reaches to 1000 mgSO2·g-1. A project demonstration was carried out in the gold smelting Tielu Plant of Zhenyuan Huashuo Precious Metals Development Co., Ltd., in Yunnan. The results of the 2-year demonstration project showed that the desulphurization efficiency of the four-stage series desulphurization tower exceeds 95%. The concentration of sulfur dioxide in the discharged flue gas is reduced to less than 20mg·m-3, which meets the requirements of ultra-low emission standard in China. Therefore, whether from theoretical research or engineering practice analysis, it is feasible to replace limestone with calcium carbide slag for flue gas desulfurization. The paper also discusses the problems existing in the demonstration project, and provides a new idea of "using waste to treat waste" in order to solve the problem of carbide slag disposal.

Desulphurization of Commercial Diesel Fuel using Activated Carbon-Based Metal Oxide Nanocomposites

This paper presents a slight on desulphurization process of the commercial diesel fuel using the carbon-based metal oxide nanocomposites such as graphene oxide, ZnO, rGO as a nano-adsorbent, activated carbon (PAC and AC) and charcoal Granular active carbon (GAC) to produce a fuel less than 10 ppm sulphur content. The synthesised of sorbents were achieved using incipient impregnation, microwaved-assisted and chemical exfoliation methods. The materials were characterized using Thermogrametric Analyzer (TGA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD), Brunauer, Emmett and Teller (BET) technics. The examination effect of operating conditions on the adsorption capacity with DBT and Sulphur compounds adsorption, the isotherms and the adsorption kinetic models were evaluated. The experimental data for PAC and AC were well suited to Freundlich isotherm and pseudo second-order kinetic models. The results shown that the sulphur feed concentration, the space velocity and the functional groups of the adsorbents had a considerable effect on the adsorption. In addition, it was observed that the temperature in the range of 30 to 600 o C had a significant effect on the adsorption of Sulphur compounds from diesel fuel using 20 wt% of sorbents. The rGO substrate which contained abundant oxygen functional groups promoted the dispersion metal oxide and increased the adsorption efficiency of sulphur compounds (H 2 S, SO 3 and SO 2 ) by providing oxygen ions weakly bound to the sulphur molecules. For the desulfurization process by adsorption, PAC and AC exhibited a better affinity for 85% removal of sulphur compared to the GAC and GO.

Performance of geopolymer as adsorbent on desulphurization of heavy gas oil

AbstractGeopolymer is a porous aluminosilicate material and chemically similar to zeolites. As a low‐cost construction material, its suitability for adsorptive desulphurization (ADS) was studied using a petroleum feedstock. Geopolymer was produced by alkali activation of metakaolin and characterized by BET, NH3–TPD, SEM, FTIR, XRD, and XPS. The XRD and SEM studies evidenced the amorphous nature of geopolymer and the existence of macro‐ and mesopores. The XPS and NH3–TPD studies revealed the presence of surface Na and Al, and strong acid sites, respectively, in the prepared geopolymer. These sites interact with sulphur compounds of heavy gas oil through π‐π and acid–base interactions. The geopolymer showed a high sulphur adsorption capacity of 38.4 mg/g. The effects of adsorption parameters such as operating temperature, amount of adsorbent, and time for absorption on the adsorption capacity were examined using the Box–Behnken design statistical model. All three operating parameters significantly influenced the sulphur adsorption capacity of geopolymer. The adsorption of sulphur compounds on the geopolymer followed pseudo‐first‐order kinetics and did not affect its structural stability. Finally, the thermodynamic study revealed that adsorption of sulphur compounds on the geopolymer was spontaneous and exothermic.

Green Synthesis of Silver Nanoparticles from Cis-Bixin and Cis-Norbixin: Potential Application for Fuel Desulfurisation

Green methods have been actively pursued in recent years as an efficient, inexpensive and environmentally safe approach for nanoparticle formation over the conventional chemical methods. Nanoparticle mediated adsorptive desulfurisation has been considered as an alternative, ecofriendly approach for fuel desulfurisation. Fuel desulfurisation is indispensible due to the fact that the combustion of fuels containing sulfur compounds release sulfur oxide compounds into environment and engenders devastating consequences on the chemistry of atmosphere. The present investigation devoted to the possibility of green synthesis of silver nanoparticles (AgNPs) using cis-bixin and cis-norbixin carotenoids as reducing and stabilising agents and the possibility of synthesised nanoparticles for removal of sulfur compounds in fuel. Cis-bixin was extracted from the pericarp of the seeds of Achiote (Bixaorellana) tree and cis-norbixin was synthesised from cis-bixin. The synthesized AgNPs from both carotenoids were characterised using UV-Visible spectroscopic technique for Surface Plasmon Resonance and absorbance peaks were obtained at 391 nm for cis-bixin and 405 nm for cis-norbixin AgNPs. The effect of temperature, pH, ionic strength of AgNO3 solution, time and stability of the formed AgNPs under electrolytic conditions were studied using UV-Visible spectroscopy and results revealed that the room temperature was paragon for optimum synthesis and AgNPs were stable in slightly acidic, neutral and slightly basic pHs and in different concentrations of NaCl (upto 0.2 M for cis-bixin and upto 0.3 M for cisnorbixin AgNPs). Synthesised AgNPs were used to investigate the fuel desulfurisation potential by using commercial kerosene as testing fuel material. For the comparative purposes NaBH4 reduced AgNPs were used. The adsorption of sulfur compounds in oil medium onto surface of AgNPs in aqueous medium produce self-assembled sulfur compounds adsorbed AgNP layer (interfacial material) on the oil/aqueous interface. The potential of the synthesised AgNPs for desulfurisation of kerosene was confirmed by analysing the sulfur content in each kerosene sample and formed interfacial material through X-Ray Fluorescence (XRF) spectroscopy. The formed interfacial material was further characterised through FTIR spectroscopy. The XRF results revealed that the AgNPs synthesised from cis-norbixin has the highest capability to reduce considerable amount of sulfur in kerosene compared to the other synthesised AgNPs. This study reports the possibility of rapid green synthesis of AgNPs form cis-bixin and norbixin under room temperature and feasible pH conditions followed by the capability for desulfurisation of fuel. Keywords: Green synthesis, Silver nanoparticles, Cis-Bixin, Cis-Norbixin, Fuel desulfurisation

Assessment of Ag Nanoparticles Interaction over Low-Cost Mesoporous Silica in Deep Desulfurization of Diesel

Chemical interactions between metal particles (Ag or Ni) dispersed in a low-cost MCM-41M produced from beach sand amorphous silica and sulfur compounds were evaluated in the deep adsorptive desulfurization process of real diesel fuel. N2 adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy coupled to energy-dispersive X-ray spectroscopy (STEM-EDX) were used for characterizing the adsorbents. HRTEM and XPS confirmed the high dispersion of Ag nanoparticles on the MCM-41 surface, and its chemical interaction with support and sulfur compounds by diverse mechanisms such as π-complexation and oxidation. Thermodynamic tests indicated that the adsorption of sulfur compounds over Ag(I)/MCM-41M is an endothermic process under the studied conditions. The magnitude of ΔH° (42.1 kJ/mol) indicates that chemisorptive mechanisms govern the sulfur removal. The best fit of kinetic and equilibrium data to pseudo-second order (R2 > 0.99) and Langmuir models (R2 > 0.98), respectively, along with the results for intraparticle diffusion and Boyd’s film-diffusion kinetic models, suggest that the chemisorptive interaction between organosulfur compounds and Ag nanosites controls sulfur adsorption, as seen in the XPS results. Its adsorption capacity (qm = 31.25 mgS/g) was 10 times higher than that obtained for pure MCM-41M and double the qm for the Ag(I)/MCM-41C adsorbent from commercial silica. Saturated adsorbents presented a satisfactory regeneration rate after a total of five sulfur adsorption cycles.

Novel application for palygorskite clay mineral: a kinetic and thermodynamic assessment of diesel fuel desulfurization

Palygorskite (Pal) is a low-cost clay mineral material and was investigated in this study as a novel material for adsorptive desulfurization of petroleum refining fractions from the Clara Camarao Potiguar Refinery (RPCC) in Brazil. This clay mineral was characterized by X-ray fluorescence, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetry, zeta potential ($$\zeta$$) and N2 adsorption/desorption isotherm analyses. Palygorskite textural properties (specific surface area 156 m2 g−1, total pore volume 0.36 cm3 g−1) and specific surface chemistry activity with several metals were crucial to efficient adsorption, proposing that an interaction between adsorbate/adsorbent involves π-complexation mainly with Fe species. This material was used in raw and thermally activated forms to evaluate the adsorption capacity. Several kinetic and equilibrium models were used to assess the experimental data. The results showed high correlation to the pseudo-second order kinetic model for both adsorbents (R2 > 0.99), suggesting a chemisorption process as the determining step. Isotherm data were used to evaluate the equilibrium experimental data. Maximum adsorption capacity calculated from the Langmuir isotherm (R2 > 0.97) was 6.25 mg g−1 for raw-Pal at 318 K. The adsorption thermodynamic assessment of S-compounds indicated an endothermic process, and there was consequently an increase in spontaneity at higher temperatures. The adsorbent raw-Pal displayed good potential in the adsorption of sulfur compounds in real diesel fuel. Palygorskite stands out for being an abundant clay mineral in nature, environmentally safe, and with high possibility of its applications in adsorption and catalysis processes.

An integrated process consisting of Mg(OH)2 –impregnated ceramic foam filters as adsorbent and Mg(OH)2 as scrubbing solution for intensified desulfurization of flue gas

Integration of individual unit operations is an efficient strategy for the process intensification. In current study, an integrated absorption/adsorption process is introduced for the flue gas desulfurization. The flue gas was originated from the combustion of a high-sulfur gasoil/naphtha fuel. The adsorbent was prepared by impregnating Al2O3/SiO2 ceramic foam filters with Mg(OH)2 via chemical vapor deposition. The setup included three sections of combustion chamber, water scrubbing vessel and absorption/adsorption reactor. In the latter section, beside adsorption of sulfur compounds on the ceramic adsorbent, Mg(OH)2 solution was being continuously refluxed and sprayed over the flue gas to intensify the desulfurization process. Total sulfur removal decreased by around 3% when Mg(OH)2 solution was substituted with pure water in the final reactor. Impact of important operating variables including temperature, pressure and, initial pH was investigated. Temperature and pressure were altered in the ranges of 30 to 70 °C and 2 to 6 bar, respectively. Results indicated the positive effects of temperature and pressure increase on the sulfur removal. The optimum pH of the reflux solution was around 8. The maximum desulfurization efficiency of the intensified process was 98%. Generally, the results confirmed the effectiveness of the absorption/adsorption integration for the desulfurization process intensification.

Process design for gas condensate desulfurization and synthesis of nano-13X zeolite adsorbent: equilibrium and dynamic studies

This paper summarizes the results of a study of adsorption of sulfur compounds from a high-sulfur feed on improved spherical-shaped nano-AgX zeolite. For this purpose, the nano-AgX zeolite was initially synthesized and improved with silver compounds such as silver nitrate, and then it was utilized in the adsorption process. In order to investigate the equilibrium and dynamics of the adsorption process, adsorptive desulfurization of real feed (i.e., sour gas condensate from the South Pars gas field) was carried out in batch and continuous processes under several operating conditions; a temperature-dependent Langmuir isotherm model was used to fit the equilibrium data. The value of monolayer adsorption capacity (qm) and adsorption enthalpy left( {Delta H} right) were calculated to be 1.044 mmol/g and 16.8 kJ/mol, respectively. Furthermore, a detailed theoretical model was employed in order to model the breakthrough experiments. The results revealed that an increase in the feed flow rate and 1/T values will cause linear and exponential increase in the total mass transfer coefficient (k_{text{s}}). Isotherm and dynamic breakthrough models were found to be in agreement with the experimental data.

Mathematical Modeling of Fixed Bed Adsorption: Influence of Main Parameters on Breakthrough Curve

Dynamic modeling and simulation of fixed bed adsorption process was carried out by explaining the behavior of breakthrough curve parameter. Adsorption of sulfur compound, present in road fuel, has posed a great challenge. A model of fixed bed adsorption of benzothiophene from fuel was formulated with non-ideal plug flow behavior and considered velocity variation along a column. The model was solved using the Method of Line (MOL) numerical solution - a technique for solving PDEs - in which all but one dimension is discretized; as a result, the set of ODEs can be solved by highly accurate methods and low computational cost. The effects of various factors, such as flow rate (4-10 cc/min), inlet concentration (125-500 ppm), and bed height (10-40 cm), on adsorption performance, were investigated. Specific characteristics, typical of breakthrough curve, were analyzed in terms of degree of bed utilization, break point time, film mass transfer coefficient, and height of adsorption zone. High bed column, high flow rate, and high inlet concentration happened to be better conditions, in term of used overall bed capacity percent for adsorption system.

Adsorption of sulfur compounds from natural gas by different adsorbents and desorption using supercritical CO2

Natural gas is extensively used in industries as well as in other sectors as an energy resource and, sometimes, it needs to undergo processes for the removal of sulfur compounds, impurities present in its composition, which can cause damages to pipes and catalysts, making it necessary to develop and/or improve deep desulfurization methods In this work, granular activated carbon was modified through two methods, oxidation using nitric acid, and impregnation using a ferric chloride solution. The resulting adsorbents were evaluated for their capacity of adsorbing seven sulfur compounds present in the synthetic natural gas sample, through their breakthrough curves. Afterward, the adsorbents desorption was performed by using supercritical carbon dioxide under the conditions of 333.15K at 100bar, 150bar and 200bar. The results indicate an average increase of 46.4% for the samples of impregnated activated carbon and 25.1% for the oxidized ones, when compared to the virgin activated carbon. Nonetheless, the supercritical conditions studied in the desorption stage were efficient only for the unmodified activated carbon samples, reaching a maximum regeneration percentage of approximately 96%, while the impregnated and oxidized ones reached only 57.4% and 72.9%, respectively. The adsorption capacities of both modified adsorbents after the regeneration were inferior to those capacities obtained in the first adsorption, then two hypotheses were investigated: (1) destruction of the newly created sites after regeneration; and (2) incomplete desorption in the studied supercritical conditions. Through other experiments it was proved that, after the regeneration, there was no destruction of the newly created sites; therefore, further studies on the operating conditions are required in order for the modified adsorbents to achieve high regeneration capacities.

Adsorption of Sulfur Compounds from Diesel with Ion-Impregnated Activated Carbons

The adsorption of benzothiophene sulfone (BTO) and dibenzothiophene sulfone (DBTO) from model diesel fuel were evaluated using granular activated carbon (GAC) and modified activated carbon. Modified activated carbon was impregnated with metal ions, Cu2+, Fe3+, and Ni2+, and the effect on its adsorption characteristics was determined. Adsorption performance was investigated using batch process at room temperature and agitation speed of 120 rpm. Results indicated a significant increase in the adsorption capacity compared to that of the unmodified GAC. Increasing adsorption capacity followed the order Cu2+/AC 0.90. Adsorption process seemed to proceed in a two-step process. First, a very fast rate for the first few minutes, then a markedly reduced rate until equilibrium is reached. All the adsorbents use...

Optimization of dispersed carbon nanoparticles synthesis for rapid desulfurization of liquid fuel

Stringent regulations and environmental concerns make the production of clean fuels with low sulfur content compulsory for the petroleum refining industry. Because of ease of operation without high energy consumption, the adsorption of sulfur compounds seems the most promising process. Central composite design was used to optimize parameters influencing the synthesis of dispersed carbon nanoparticles (CNPs), a new class of sorbents, in order to obtain an excellent adsorbent for desulfurization of liquid fuel. The optimized dispersed CNPs, which are immiscible in liquid fuel, can effectively adsorb different benzothiophenic compounds. Equilibrium adsorption was achieved within 2 min for benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene with removal efficiency values of 75 %, 83 %, and 52 %, respectively. The rate of desulfurization by the prepared CNPs in the present work is seven times higher than the previously reported CNPs. Optimized CNPs were characterized by different techniques. Finally, the effect of the mass of CNPs on the removal efficiency was studied as well.

Performance evaluation of LPG desulfurization by adsorption for hydrogen production

The adsorption of sulfur compounds, in commercially available LPG, has been studied using different adsorbents, namely Zeolite, ZnO and house made date pits activated carbon (DP-AC). It was found that the three adsorbents are capable of effectively removing sulfur compounds at different feed sulfur concentrations. The effects of height to diameter aspect ratio of the adsorption column, flow rate of LPG and input sulfur concentrations have been studied. A first order kinetics model has been used to describe the adsorption, and the kinetics constant was found to increase by increasing the flow rate of LPG and decrease by increasing the amount of adsorbent used. The developed model described the system fairly well, and can be used in designing and scaling-up of fixed-bed adsorption columns.

The Effect of Synthetic Zeolite on the Adsorption of Sulfur Compounds and Ammonia, and their Desorption Properties by Microwave Heating

The Effect of Synthetic Zeolite on the Adsorption of Sulfur Compounds and Ammonia, and their Desorption Properties by Microwave Heating

Removal of sulfur compounds from petroleum refinery wastewater through adsorption on modified activated carbon

The adsorption of sulfur compounds from petroleum refinery wastewater on a chemically modified activated carbon (MAC) was investigated. The modification technique (nitric acid, hydrogen peroxide and thermal modification) enhanced the removal capacity of carbon and therefore decreases cost-effective removal of sulfide from refinery wastewater. Adsorption equilibrium and kinetics data were determined for sulfur removal from real refinery wastewater. The data were evaluated according to several adsorption isotherm and kinetics models. The Freundlich isotherm fitted well with the equilibrium data of sulfur on different adsorbents, whereas the kinetics data were best fitted by the pseudo-second-order model. Insights of sulfide removal mechanisms indicated that the sorption was controlled through the intraparticle diffusion mechanism with a significant contribution of film diffusion. The MAC adsorbent was found to have an effective removal capacity of approximately 2.5 times that of non-modified carbon. Using different MAC, sulfides were eliminated with a removal capacity of 52 mg g(-1). Therefore, MAC can be utilized as an effective and less expensive adsorbent for the reduction of sulfur in refinery wastewater.

Metal-impregnated carbon applied as adsorbent for removal of sulphur compounds using fixed-bed column technology

Metal-impregnated carbons (Cu–AC; Ag–AC and Pd–AC) were studied as adsorbents for the desulphurization of liquid fuels. A real gasoline was examined for sulphur compounds. Textural characteristics of adsorbents were determined by nitrogen adsorption/desorption isotherms at 77 K. The adsorption isotherms were obtained by frontal analysis in a single fixed bed at 30°C and 45°C. Breakthrough curves were simulated according to a mathematical model that assumed axially dispersed flow and mass transfer described by a linear driving force approximation and nonlinear adsorption equilibrium reached instantaneously on the external surface of the adsorbents particles. The model was solved numerically by orthogonal collocation in finite elements, using the commercial solver gPROMS. The proposed model matched experimental data reasonably well. Resistance to mass transfer was significant and thought to be due to intraparticle diffusion kinetics. The results confirmed the efficiency of the use of activated carbon (AC) in the adsorption of sulphur compounds, especially when its surface is modified with metals. Comparing adsorption capacities of sulphur compounds from real gasoline, AC–Pd material appeared more selective than other materials, even presenting a behaviour of rapid saturation explained by the presence of other components competing for adsorption sites, reducing their effectiveness in removing sulphur compounds. Both pristine AC and Pd–AC showed good regenerability. The regenerated Pd–AC sorbent can recover about 85% of the desulphurization capacity.

Adsorption behaviors of thiophene, benzene, and cyclohexene on FAU zeolites: Comparison of CeY obtained by liquid-, and solid-state ion exchange

Cerium containing Y zeolites were prepared by liquid- (L-CeY) and solid- (S-CeY) state ion exchange from NaY and HY, respectively. The structural and textural properties were characterized by XRD and N2 adsorption, and acidity properties were characterized by NH3 temperature-programmed desorption (NH3-TPD) and in situ FTIR spectrum of chemisorbed pyridine (in situ Py-FTIR). Furthermore, the single component adsorption and multi-component competitive adsorption behavior of thiophene, benzene and cyclohexene on those zeolites have also been studied by using vapor adsorption isotherms, solution adsorption breakthrough curves, thermogravimetry and derivative thermogravimetry (TG/DTG), frequency response (FR) and in situ FTIR techniques. The results indicate that the primary adsorption mode of benzene is simply micropore filling process, but the nature of effect of aromatics on selective adsorption of thiophene is competitive adsorption. The strong chemical adsorptions and protonization reactions of thiophene and cyclohexene occur upon the Brönsted acid sites of the HY and L-CeY zeolites, and the preferable acid catalytic protonization reactions of olefins hinder the further adsorption of sulfur compounds.

Production of ultra-low-sulfur gasoline: An equilibrium and kinetic analysis on adsorption of sulfur compounds over Ni/MMS sorbents

High performance nickel-based micro-mesoporous silica (Ni/MMS) sorbent was prepared by incipient wetness impregnation with ultrasonic aid (IWI-u) for adsorptive desulfurization (ADS) of commercial gasoline and simulated fuels. The sorbents were characterized with BET, XRD, TPR, SEM, HRTEM and TG/DTG. These results show that 20wt%Ni/MMS (IWI-u) can still retain the framework of MMS and nickel particles were homogeneously distributed in the MMS channels without any aggregation, which improved significantly the ADS performance of the sorbents. The studies on the ADS kinetics indicate that the adsorption behavior of thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT) over 20wt%Ni/MMS (IWI-u) can be described appropriately by pseudo second-order kinetic model. The intraparticle diffusion model verified that the steric hindrance and intraparticle diffusion were the rate controlling step of the adsorption process of DBT molecules. Langmuir model can be used to describe the adsorption isotherms for T, BT and DBT due to low coverage. The regeneration sorbent maintains the sulfur removal efficiency of 85.9% for 6 cycles.

Regeneration of Sulfur Deactivated Ni-Based Biomass Syngas Cleaning Catalysts

Nickel-based catalysts have been widely tested for reforming undesired tar and methane from hot biomass-derived syngas. However, nickel catalysts readily deactivate through the adsorption of sulfur compounds in the syngas. We report a new regeneration process that can effectively regenerate sulfur-poisoned Ni reforming catalysts. This process consists of four sequential treatments: (1) controlled oxidation at 750 °C in 1% O2, (2) decomposition at 900 °C in inert gas, (3) reduction at 900 °C in 2% H2, and (4) reaction at 900 °C under reforming condition. This 4-step regeneration process might have advantages over the conventional steam regeneration process.