Adsorption Of Hydrogen Chloride Research Articles

Metal oxide modified MCM-41 on simultaneous removal of HF and HCl: Experimental and theoretical studies

To address the issue of harmful gases Hydrogen fluoride (HF) and hydrogen chloride (HCl) in metallurgical waste gas, this study utilized metal oxide modified molecular sieve (MCM-41) for their simultaneous removal. The adsorption and removal of HF and HCl are mainly influenced by alkaline sites and pore structure, with alkaline sites having a greater impact. MgO affects the alkaline site strength and pore structure, thereby facilitating the removal of HF and HCl. On the surface of the adsorbent, HF and HCl react to form MgF2 and MgCl2, which gradually reduces the adsorbent's performance. HF and HCl have a higher adsorption strength on the MgO surface, and the H…O interaction causes a more stable adsorption configuration. There is a competitive adsorption effect between HF and HCl, with HF having a preference for adsorbing on the MgO surface over HCl. The adsorption energies of HF and HCl are unlimited by adsorption effects. When the O atom in MgO is replaced by HF and HCl, Mg-F bonds, Mg-Cl bonds, and H-O bonds are formed, resulting in the formation of MgF2, MgCl2, and H2O. HF is easier to prioritize removal than HCl

Effect of SO2 on HCl removal over ethanol-hydrated CaO adsorbent: Mechanism of competitive adsorption and product layer shielding

The elimination of hydrogen chloride (HCl) is essential for wastewater sequestration and safe operation of equipment in coal-fired power plants. A new adsorbent of ethanol-hydrated CaO has been developed, which possesses a 100% HCl removal efficiency lasting 30 min in a fixed bed reactor being much superior to traditional dechlorinators. Nevertheless, SO2 in flue gas has instinctive and strong competition with HCl on the alkaline adsorbent that results in detrimental effects and makes the removal mechanisms confused and unclear. To solve this issue, a series of experiments were designed to evaluate how SO2 influences the performance of HCl adsorption over the adsorbent. Comprehensive characterizations and density functional theory (DFT) calculations further studied the mechanisms of the competition mechanism between SO2 and HCl. The results indicate that SO2 has a detrimental impact on HCl removal by consuming the active Ca site, diminishing the alkalinity and worsening the surface activity due to the product layer formation. DFT calculations reveal that the high adsorption energy of SO2 suppresses the active sites for HCl removal. The faded surface electrostatic potentials (ESP) around the sulfurized Ca active sites lead to apparent activity shielding on the absorbent surface. Besides, the frontier molecular orbital (FMO) theory unveils a narrow electronic transfer energy gap for SO2 adsorption. These findings contribute to elucidation of SO2 competition to HCl on the calcium-based adsorbent in coal-fired flue gas.

Imine Bond-Based Fluorescent Nanofilms toward High-Performance Detection and Efficient Removal of HCl and NH3.

A new kind of imine bond-based fluorescent nanofilm was developed as multifunctional materials for high-performance detection and efficient removal of hydrogen chloride (HCl) and ammonia (NH3). The flexible, uniform, and photochemically stable nanofilms as prepared showed fast (<1 and <0.5 s), sensitive (<150 ppb and <1.5 ppm), and selective response to HCl and NH3, respectively, and the removal efficiencies to HCl and NH3 are 187.5 and 37.5% (w/w), respectively. A reversible earthy-red to green fluorescence color change upon adsorption of NH3 or HCl enabled visualized monitoring of the two gases in the air. Mechanism studies revealed that the adsorption of HCl is a result of hydrogen bond formation between the analyte and the imine groups. Adsorption of NH3, however, is a result of chemical reaction with the pre-adsorbed HCl. The applicability of the detection and removal strategies as developed was further verified by conducting the tests on real-life or simulated scenarios.

Гидролиз целлюлозы с использованием газовоздушных смесей хлористого водорода

Abstract. Microcrystalline cellulose (MCC) is a common product used in pharmaceutical, food and other industries. MCC is obtained by liquid-phase hydrolysis of cotton or wood bleached pulp with diluted 0.5–10.0 % mineral acids at a temperature of 100–140 °C. This process requires significant consumption of acid, water, and heat energy. Production of MCC in general is very expensive, which determines its high cost and the need to find alternative methods of cellulose hydrolysis. It is proposed to hydrolyze cellulose with concentrated hydrochloric acid produced by absorption of hydrogen chloride. We studied the processes of hydrogen chloride adsorption by bleached wood pulp with 8–18 % humidity. It is shown that adsorption of hydrogen chloride is determined by pulp humidity and is 3–5 % of the dry pulp mass. The sorption of hydrogen chloride leads to the formation of hydrochloric acid with a concentration of 25–40 % in the raw material moisture, significant heating of the mass and rapid hydrolysis of the amorphous cellulose fraction. It has been found that the use of pure hydrogen chloride for saturation causes strong darkening and humification of pulp. We recommend the use of hydrogen chloride gas-air mixtures to saturate the pulp, which will significantly reduce the sorption temperature and eliminate the strong darkening of the pulp during hydrolysis. The adsorption of hydrogen chloride by cellulose proceeds at an extremely high rate and is accompanied by the formation of a clearly visible sorption front at a temperature of 45–60 °C. Hydrolysis occurs for 15–30 min at 40–60 °C until the amorphous cellulose fraction is completely decomposed. A very small amount of monosaccharides is formed (4 % of dry pulp). The yield of MCC is high, more than 95 %. These circumstances are probably related to the recrystallization of a part of the amorphous fragments of cellulose macromolecules, which is a characteristic of hydrolysis with concentrated acids. The product obtained by cellulose hydrolysis is identical to MCC according to the data of IR spectroscopy, X-ray diffraction and viscometry. The article shows the high efficiency of cellulose hydrolysis with hydrogen chloride gas-air mixtures compared to traditional methods of MCC production.

A molecular beam-surface apparatus for quantum state-resolved adsorption studies.

Understanding the microscopic mechanism of molecule-surface interaction is of great importance in the study of chemical dynamics. Yet, it remains challenging to experimentally acquire quantum state resolved results, particularly the results related to different degrees of freedom of the reactants. Here, we report the designand performance of a new apparatus for molecule-surface dynamics studies, which enable the measurement of quantum state-resolved adsorption. A continuous narrow-linewidth infrared laser source and molecular beam unit were developed and employed in this new apparatus to achieve independent control on different degrees of freedom (translation, vibration, and rotation) of the molecule. Preliminary results on hydrogen and hydrogen chloride adsorption on the Cu (111) surface were also presented.

Quantum chemical study on adsorption of hydrogen chloride on Zn-doped carbon materials

Abstract In previous studies of HCl adsorption on Zn-doped O 2 activated carbon (AC) at 100 and 300 °C, we revealed that Zn-doped carbon adsorbed far more HCl than undoped carbon. However, the effect of metals on the adsorption capability of AC and the mechanism of the adsorption stability of HCl have not yet been clarified. Herein, we used molecular orbital (RHF/6-31G ∗ ) calculations for three carbon active site models (Armchair, Zigzag, and Tip types) to investigate the effect of Zn doping on HCl adsorption via the estimation of the electronic states. The molecular models of the carbon materials with or without Zn doping showed that the presence of Zn increased the number of active sites available for the chemical adsorption of HCl molecules. Furthermore, Zn did not contribute to the adsorption stability of HCl in the Zigzag type model. Zn doping was found to change the electronic state of the active site of the carbon material in the direction in which HCl was readily adsorbed. This study lays the conceptual foundation for suppressing the formation of environmentally harmful volatile compounds from HCl generated in high-temperature processes via the modification of carbon materials to increase HCl adsorption.

Enhanced HCl removal from CO2-rich mixture gases by CuOx/Na2CO3 porous sorbent at low temperature: Kinetics and forecasting

Selective removal of hydrogen chloride (HCl) using porous active sorbents has been considered to be a feasible way to reduce the harm of chlorine in flue gas. In this work, the kinetics process of HCl capture from CO2-rich mixture gases by CuOx/Na2CO3 porous supported sorbent was studied systematically in a fixed-bed column at low temperature. The effects of flow rate, gas composition and operation temperature on HCl adsorption were intensively investigated. The results show that the HCl adsorption performance of sorbents decreased with the feed flow rate and CO2 content increasing, whereas the effect of HCl concentration was negligible. In addition, HCl adsorption capacity increased with the increase of temperature (100–150 °C), but decreased after 170 °C. In the first part of dynamic heterogeneous reaction, axial dispersion mass transfer of reactive gas molecules dominated the overall reaction rate. But for second part, the gas diffusion in product layers replaced as a rate-controlled step. The overall sorbents conversion calculated by random pore model (RPM) demonstrated fine agreement with the experimental data and the diffusion activation energy was 23.11 kJ/mol. Moreover, the semi-empirical equation of BDST model was applied to predict the breakthrough curves with a standard deviation less than 4%. The forecasting results of industrial large-scale reactor indicate that 500 tons sorbents can effectively remove HCl from the flue gas (400000 m3/h) produced by 2650 m3 blast furnace for as long as 13 days.

Thermal Processing of Chloride-Contaminated Plutonium Dioxide.

Over 80 heat treatment experiments have been made on samples of chloride-contaminated plutonium dioxide retrieved from two packages in storage at Sellafield. These packages dated from 1974 and 1980 and were produced in a batch process by conversion of plutonium oxalate in a furnace at around 550 °C. The storage package contained a poly(vinyl chloride) (PVC) bag between the screw top inner and outer metal cans. Degradation of the PVC has led to adsorption of hydrogen chloride together with other atmospheric gases onto the PuO2 surface. Analysis by caustic leaching and ion chromatography gave chloride contents of ∼2000 to >5000 ppm Cl (i.e., μgCl g–1 of the original sample). Although there are some subtle differences, in general, there is surprisingly good agreement in results from heat treatment experiments for all the samples from both cans. Mass loss on heating (LOH) plateaus at nearly 3 wt % above 700 °C, although samples that were long stored under an air atmosphere or preexposed to 95% relative humidity atmospheres, gave higher LOH up to ∼4 wt %. The majority of the mass loss is due to adsorbed water and other atmospheric gases rather than chloride. Heating volatilizes chloride only above ∼400 °C implying that simple physisorption of HCl is not the main cause of contamination. Interestingly, above 700 °C, >100% of the initial leachable chloride can be volatilized. Surface (leachable) chloride decreases quickly with heat treatment temperatures up to ∼600 °C but only slowly above this temperature. Storage in air atmosphere post-heat treatment apparently leads to a reequilibration as leachable chloride increases. The presence of a “nonleachable” form of chloride was thus inferred and subsequently confirmed in PuO2 samples (pre- and post-heat treatment) that were fully dissolved and analyzed for the total chloride inventory. Reheating samples in either air or argon at temperatures up to the first heat treatment temperature did not volatilize significant amounts of additional chloride. With regard to a thermal stabilization process, heat treatment in flowing air at 800 °C with cooling and packaging under dry argon appears optimal, particularly, if thinner powder beds can be maintained. From electron microscopy, heat treatment appeared to have the most effect on degrading the square platelet particles compared to those with the trapezoidal morphology.

Novel Isopropoxy Group-Functionalized UiO-66 with a High Hydrogen Chloride Adsorption Capacity

In this paper, a novel isopropoxy group-functionalized UiO-66 (UiO-66-IPO) was synthesized by a general strategy and then used as an adsorbent for the removal of hydrogen chloride from aqueous solutions. The as-synthesized product was characterized by X-ray powder diffraction, scanning electron microscopy, thermal gravimetric analysis, N2 adsorption and desorption isotherms, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The adsorbent showed a much higher adsorption capacity of 429.68 mg·g–1 under the initial condition of 1.4 mol·L–1 HCl concentration at 25 °C within a relatively short time (4 h). Adsorption kinetics, isotherms, thermodynamics, regeneration, and the mechanism of hydrogen chloride adsorption on the adsorbent were studied. The results showed that the hydrogen chloride adsorption process reached equilibrium quickly in 4 h, and the adsorption kinetics on UiO-66-IPO was well-described by the pseudo-second-order model. Meanwhile, the Henry isotherm ...

Hydrogen chloride adsorption on large defective PAHs modeling soot surfaces and influence on water trapping: A DFT and AIMD study

DFT calculations both at 0 K in energy optimization procedure and at finite temperature in ab initio molecular dynamics (AIMD) calculations are used to characterize the adsorption of the hydrogen chloride molecule on a carbonaceous cluster in which a carbon vacancy has been created by removing one carbon atom. This aims at modeling the defective surface of the small graphitic basic structural units that constitute soot nanoparticles, as experimentally evidenced. The results show that HCl can be easily dissociated at the vacancy site of the surface, resulting in the formation of a chlorinated site at the carbonaceous surface, which could have different structures depending on the thermodynamics of the reactions. Then, the resulting chlorinated carbonaceous surfaces are used as model substrates to characterize the first stages of the adsorption of water molecules on chlorinated soot. It is thus shown that adsorbed chlorine atoms may act as an efficient nucleation center for water trapping at the surface of soot. These results represent a new step towards a better understanding of the soot behavior in industrial or domestic fire situations, as well as in marine atmospheric environment where oxidant and chlorinated species are ubiquitous.

Carbon with Surface‐Enriched Nitrogen and Sulfur Supported Au Catalysts for Acetylene Hydrochlorination

AbstractNitrogen‐doped carbons supported gold catalysts has attracted much attention in a broad range of applications. However, co‐existence of multiple nitrogen species which may have vastly different effect on the gold‐based catalysts, has limited the development of an ideal nitrogen‐doped carbon support. Herein, we have demonstrated that by addition of sulfur species, selective formation of pyrrolic nitrogen against pyridinic nitrogen can be achieved for pyrrolic nitrogen doped carbon support. The gold catalysts synthesized from the pyrrolic nitrogen doped carbon support produced using ionic liquid‐assisted synthetic strategy (Au/N, S‐AC‐700), exhibited excellent catalytic activity and stability for hydrochlorination of acetylene. The outstanding performance was attributed to the π electrons transferred from pyrrolic nitrogen to Au (III) center, which could increase the electron density of Au hence facilitate the adsorption of hydrogen chloride on the catalyst.

Alkoxy-Group-Functionalized UiO-66 as Highly Efficient Adsorbents for Hydrogen Chloride Removal from Aqueous Solution

A series of alkoxy group-functionalized UiO-66 were designed for hydrogen chloride adsorption from aqueous solution, which were characterized by various methods to verify the structures and study t...

A two-step method for the integrated removal of HCl, SO2 and NO at low temperature using viscose-based activated carbon fibers modified by nitric acid

Activated carbon fibers (ACFs) have been widely used as cost-effective integrated processes for the removal of nitrogen oxides, sulfur oxides and hydrogen chloride (HCl), while the competitive adsorption behaviors and the detailed interaction mechanisms have not been comprehensively investigated. In the current work, the adsorption capacities with one-step process and two-step method were compared, and the effects of HNO3 modification and ambient O2 concentration were simultaneously studied. Furthermore, the relative ratios of surface nitrogen groups, sulfur and chlorine compounds, as well as the soluble species on the ACFs surface, were respectively characterized by X-ray photoelectron spectroscopy and ion chromatography techniques. The results indicated that HCl, SO2 and NO were not able to be effectively removed with only one reactor due to the strong competitive adsorption behaviors, while the adsorption capacities of HCl, SO2 and NO were significantly improved by 30%, 280%, 230% in the two-stage reactors with HNO3 modification. Further investigation indicated interactions between HCl, SO2 and NO in the two-stage reactors are very complicated. The primary reactor can remove HCl and facilitate the catalytic removal of SO2/NO in the secondary reactor since HCl can severely inhibit the adsorptions of SO2 and NO, yet HCl adsorption can be suppressed by SO2. Simultaneously, nitro/nitroso groups derived of HNO3 treatment and NO oxidation can promote the chemisorption of HCl.

Inexpensive metal oxides nanoparticles doped Na2CO3 fibers for highly selective capturing trace HCl from HCl/CO2 mixture gas at low temperature

A novel inexpensive metal oxides doped sorbents had been investigated for selective capture of hydrogen chloride (HCl) from HCl/CO2 (1:25 v/v) mixture gas at 150 °C. In this work, metals oxides (Fe, Mn, Ce and Cu) grains supported on the Na2CO3 fibers were firstly prepared via ultrasonic atomization loading method, respectively. The results of HCl removal experiments showed that Cu dopant with optimal content synergistically facilitated HCl capture performance, continuously removing HCl from initial content of 1% to less than 1 ppm as long as 6.5 h. And the HCl capacity reached 3.15 mmol/g, corresponding to the conversion of active component Na2CO3 was up to 0.89. Meanwhile, the Cu doped sorbent exhibited a strongly selective adsorption of HCl under extreme lower volume ratio HCl/CO2 of 1:25. The enhancement of Na2CO3 reactive activity depended on the highly dispersed copper oxides nanoparticles on the surface of Na2CO3 fibers. CuO species in copper oxides reacted with HCl to form CuCl2, while the presence of amorphous phase connecting CuO nanoparticles and Na2CO3 strongly promoted the mass transfer in product layers. The intensification of these two aspects made copper doped adsorbent exhibited significant HCl removal performance. Moreover, during regeneration test, the sorbents could maintain fairly stable cyclic performance within three cycles.

Valorization of Waste-Derived Inorganic Sorbents for the Removal of HCl in Syngas

Syngas production via the pyro-gasification of waste biomass is a promising means of managing waste while producing renewable fuel. However, such waste may contain a significant level of impurities such as chlorine, which may result in hydrogen chloride (HCl) being formed in the syngas produced. The presence of HCl gas may increase the risk of corrosion and may be harmful to health and to the environment. Consequently, stricter limits on HCl concentration in syngas are being imposed by environmental regulations and syngas end-use specifications, which is driving the search and development of more efficient and cost-effective methods of eliminating HCl. One such method is dry adsorption using inorganic sorbents. In literature, the majority of sorbents studied are based on commercialised products, and thus, there lack studies on the use of waste-derived sorbents for treating HCl in syngas. Therefore, this paper presents an experimental study on the adsorption potential of the solid waste sorbent, CCW-S, which is compared to that of the commercial sorbent, Bicar. Various physico-chemical analyses were performed on the sorbents before and after the tests, including ICP, FTIR, XRD and TEM-EDX. The first set of adsorption tests were performed using a gas mixture of 500 ppm HCl in nitrogen (HCl/N2) at ambient conditions (25 °C, 1 atm). The results revealed that Bicar was the better performing sorbent with an average breakthrough time of 66 h and a HCl adsorption capacity of 27 wt%, whereas the performance of CCW-S was lower (7.8 h and 4 wt%). Furthermore, TEM-EDX images of CCW-S particles show the participation of the impurities—Al, Fe, and Mg—in HCl capture. When the second set of adsorption tests were conducted with a simulated HCl/syngas atmosphere, a significant decrease in sorbent performance was observed, which showcases inhibitory interactions occurring between syngas and the sorbents, in relation to HCl adsorption. The results of this preliminary investigation reveal a promising opportunity to valorize industrial residues as cheap and efficient sorbents for the removal of HCl in syngas. This will enable a wider market penetrating of waste-derived syngas, while meeting the quality requirements of increasingly strict environmental regulations and end-use devices.

Adsorptive hydrogen chloride and combined hydrogen chloride–hydrogen sulphide removal from biogas for solid oxide fuel cell application

In order to reduce the toxic effect on solid oxide fuel cells performance caused by biogas contaminated with hydrogen chloride and hydrogen sulphide, the purification of biogas is essential. Adsorptive gas purification is a highly auspicious technology to provide pollution-free biogas for solid oxide fuel cell-based power units. In this work the authors examined the influence of different parameters onto the adsorption capacity of three commercially available sorbents. Experimental runs in a laboratory glass downflow fixed-bed reactor were carried out to analyse the adsorption capacity of a potassium carbonate impregnated activated carbon and two sorbents based on a mixture of aluminium oxide and silicon dioxide. Hydrogen chloride removal was accomplished with the impregnated activated carbon and metal oxide-based sorbents. Hydrogen chloride adsorption capacity was analysed under space velocities 8000 and 16,000 h−1. In addition, the effect of a hydrogen chloride inlet concentration of 100 and 1000 ppmv was investigated. Furthermore, pellets in the size of 3–4 mm in diameter were crushed into a fraction between 500 and 1000 µm to investigate the influence of particle size on hydrogen chloride adsorption capacity. Additionally, the combined adsorption of hydrogen chloride and hydrogen sulphide was realized using the impregnated activated carbon. The experimental runs and the results obtained in this work provide useful data for designing an adsorption reactor to clean up biogas and optimizing the process.

Activated Carbon Supported Mo-Ti-N Binary Transition Metal Nitride as Catalyst for Acetylene Hydrochlorination

Recently, many scientists have focused on the development of green industrial technology. However, the process of synthesizing vinyl chloride faces the problem of Hg pollution. Via a novel approach, we used two elements Mo and Ti to prepare an inexpensive and green binary transition metal nitride (BTMN) as the active ingredient in a catalyst with nano-sized particles and an excellent degree of activation, which was supported on activated carbon. When the Mo/Ti mole ratio was 3:1, the conversion of acetylene reached 89% and the selectivity exceeded 98.5%. The doping of Ti in Mo-based catalysts reduced the capacity of adsorption for acetylene and also increased the adsorption of hydrogen chloride. Most importantly, the performance of the BTMN excelled those of the individual transition metal nitrides, due to the synergistic activity between Mo and Ti. This will expand the new epoch of the employment of transition metal nitrides as catalysts in the hydrochlorination of acetylene reaction.

Alternative solvent to aqua regia to activate Au/AC catalysts for the hydrochlorination of acetylene

In this paper, we demonstrate that the less toxic, relatively safe, and recyclable organic aqua regia (OAR) can be employed as a greener alternative solvent to conventional aqua regia to activate Au/AC catalysts for the hydrochlorination of acetylene. We show that Au-based catalysts prepared with HAuCl4 as precursor can be prepared initially in water (Au(H2O)/AC). Although catalysts prepared from aqueous HAuCl4 showed poor activity, it can be significantly enhanced by catalyst activation in OAR (Au(H2O)/AC(OAR)). In contrast to the catalyst activation procedure using aqua regia (Au(aq)/AC), we demonstrate that the new activation procedure leads to both improved activity and stability of the resulting Au(H2O)/AC(OAR) catalyst. Further analyses of X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) show that the variations of Au particle size and chemical state caused by OAR treatment promote Au oxidation and high dispersion. In addition, temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) indicated that the presence of residual sulfur and nitrogen species may help stabilize the cationic Au3+ species and generate a catalyst less prone to deactivation by increasing the reduction temperature of the Au3+ species and enhancing the adsorption of hydrogen chloride over the Au(H2O)/AC(OAR) catalyst. These results suggest that OAR can be substituted for conventional solvents to activate Au/AC catalysts for the hydrochlorination of acetylene.

The Preparation of Cu-g-C3N4/AC Catalyst for Acetylene Hydrochlorination

A novel catalyst based on g-C3N4/activated carbon was prepared by adding CuCl2. The catalytic performance of the as-prepared catalyst was investigated in the acetylene hydrochlorination reaction. X-ray photoelectron spectroscopy, temperature programmed desorption, low temperature N2 adsorption/desorption (Brunauer–Emmett–Teller), and thermal gravity analysis showed that Cu-g-C3N4/AC significantly enhanced the catalytic performance of the original catalyst by increasing the relative pyrrolic N content. Cu-g-C3N4/AC also affected the adsorption of hydrogen chloride and acetylene, as well as inhibited the coke deposition during acetylene hydrochlorination.

Interfacial and bulk properties of vapor-liquid equilibria in the system toluene + hydrogen chloride + carbon dioxide by molecular simulation and density gradient theory + PC-SAFT

Interfacial and bulk properties of vapor-liquid equilibria (VLE) in systems containing toluene, hydrogen chloride (HCl), and carbon dioxide (CO2) are studied by molecular dynamics simulations and density gradient theory + PC-SAFT. The pure components, the three binary mixtures, and the ternary mixture are studied systematically. A new PC-SAFT model of HCl is developed and mixture models are adjusted to binary VLE data. The focus of the studies is on the temperatures 333 and 353 K for which both HCl and CO2 are supercritical. The simulation results are compared to experimental data, where such data are available. VLE bulk properties are well described. For the interfacial tension, only pure component data are available, which are well predicted. For the mixtures, data on the interfacial tension are predicted. A strong adsorption of both HCl and CO2 at the vapor-liquid interface is found from both methods.