Solid HCl Research Articles

Insights into the effect of operating parameters and hydrodynamics on hydrolysis reaction in Copper–Chlorine thermochemical water splitting cycle for hydrogen production: Modelling and experimental validation

Copper–Chlorine (Cu–Cl) thermochemical cycle is being explored as one of the promising technologies for large scale production of clean hydrogen from water using nuclear or renewable energy. In this method, water splitting is achieved through a series of reactions in a loop producing only hydrogen and oxygen with complete recycle of all the intermediate copper and chlorine compounds. The first step of the cycle is the hydrolysis reaction wherein steam reacts with solid CuCl2 to form solid Cu2OCl2 (copper oxychloride) and HCl gas. The products enter the subsequent steps of the cycle and are recycled back to complete the loop. Multiple side reactions in the hydrolysis step result in reduced yield and loss of chemicals from the cycle. Efficient reactor design and optimal operating conditions of hydrolysis reactor is imperative towards achieving sustained closed loop operation and reducing the energy demand of Cu–Cl cycle. This paper presents a mathematical model for the simulation of hydrolysis reaction in a bubbling fluidized bed reactor. The one-dimensional model is developed based on modified two-phase theory of fluidization and is coupled with kinetics of multiple side reactions to investigate the effect of operating parameters and hydrodynamics on the conversion and yield of Cu2OCl2. The model results are validated with experimental data in 50 mm and 100 mm semi-batch fluidized bed reactors. The developed model clearly brings out the effect of different process parameters for process optimization and scale-up of the hydrolysis reactor for efficient integration in the cycle.

Improvement of Bio-Oil and Nitrogen Recovery from Microalgae Using Two-Stage Hydrothermal Liquefaction with Solid Carbon and HCl Acid Catalysis.

Bio-oil production from microalgae by using hydrothermal liquefaction (HTL) has been conducted extensively in the last decade. In this work, we conducted two-stage HTL of a microalga (Fistulifera solaris, JPCC DA0580) in the presence of 5.0 g/L carbon solid acid or a 0.02–0.50 M HCl catalyst to increase bio-oil yield and nitrogen recovery into the aqueous phase (AP). The first stage (HTL 1), to hydrolyze proteins, carbohydrates, and lipids and elute nitrogen components into the AP, was conducted at 100–250 °C for 30–120 min. The second stage (HTL 2), to produce the bio-oil, was conducted at 280–320 °C for 0–30 min. The best conditions to obtain a high bio-oil yield and NH4+ recovery in the AP were 200 °C and 30 min of residence time for HTL 1 and 320 °C and 0 min residence time for HTL 2. We found that 0.50 M HCl decreased the bio-oil yield while greatly increasing NH4+ in the AP and decreasing the nitrogen content in the bio-oil. This was probably due to the catalytic effect of HCl promoting hydrolysis of protein and deamination of amino acids during HTL 1. The fractions of water-soluble products were greatly increased by performing HTL 2 in neutral conditions while this maintained low nitrogen content in the bio-oil. From GC–MS analyses of the bio-oil, it was observed that, by using 0.50 M HCl, peak intensities of all the GC peaks decreased and MS spectra of amines decreased. The carbon solid acid had an insignificant influence on bio-oil and NH4+ yields.

HCl modification and pervaporation performance of BTESE membrane for the dehydration of acetic acid/water mixture

Membrane pervaporation has gained much attraction for high level purity of acetic acid from water because of energy saving and ecofriendly operation compared with distillation and extraction. However, fabricating membranes with high stability, selectivity and permeation flux for dehydration of acetic acid by pervaporation is highly demanded. In this work, hybrid silica membranes were fabricated using bis(triethoxysilyl) ethane (BTESE) as a precursor through sol gel route. Further modification was done as solid post HCl treatment for the synthesized BTESE membrane aiming to improve separation performance of the BTESE membranes for dehydration of acetic acid. The effect of HCl exposure time (30, 100, and 150 min) to the synthesized BTESE membranes was investigated to get optimum treatment conditions with lower separation tradeoff. In our investigation HCl treatment for about 100 min was found suitable in order to maintain permeation flux with higher selectivity. For the pervaporation performance to dehydrate acetic acid/water (90/10 wt%) at 80 °C, the synthesized BTESE membrane showed total flux of 2.47 kg m−2 h−1 with separation factor about 350 but HCl treated (100 min) BTESE membrane showed almost double separation factor up to 780 with somehow reduced flux (2.07 kg m−2 h−1). Both the membranes (synthesized and HCl treated BTESE) showed good stability within the investigated time of 150 h at 80 °C.

Close-spaced vapor transport reactor for III-V growth using HCl as the transport agent

Low-cost methods of III-V deposition are an important component of making high-efficiency III-V solar cells cost-competitive for terrestrial applications. Here, we report the design and testing of a close-spaced vapor transport system for the growth of epitaxial GaAs films using solid precursors and HCl as the transport agent. Previous work on a related system demonstrated growth of high-quality GaAs using H2O as the transport agent, but the use of H2O generates oxide-related defects and limits material compatibility. The new design also enables independent handling of source and substrate material. The effect of process conditions on growth rate, surface morphology, and substrate-orientation-dependent growth is discussed. We demonstrate successful doping of Si and Zn with average transport efficiencies of approximately 30% and 20%, respectively, based on secondary-ion-mass-spectrometry data. Room-temperature hall mobilities approached those achieved for GaAs grown by metal-organic vapor phase epitaxy and water-based close-spaced vapor transport, 2210–3400 cm2 V−1 s−1 for n-GaAs and 70–110 cm2 V−1 s−1 for p-GaAs depending on dopant concentration. Initial results on doping and cross-contamination suggest this system should be capable of homoepitaxial growth of p-n junctions.

The Effect of Secondary Refining on the Removal of Phosphorus from Metallurgical-Grade Silicon by Acid Leaching

The effects of structural composition, particle size, leaching time, temperature, and liquid–solid ratio on the removal of phosphorus from metallurgical-grade silicon (MG-Si) by acid leaching were investigated. Two specimens with different phase constitutions were studied: crude metallurgical-grade silicon (C-MG-Si), which is reduced from electric arc furnace, with a high content of Al and Ca, and a secondary refined metallurgical-grade silicon (S-MG-Si) obtained after secondary refining in ladle. Using scanning electron microscopy-energy dispersive spectroscopy, the phosphorus-containing phase was only detected in the C-MG-Si grain boundaries. The Si2Al2Ca phase, which was soluble in HCl, showed an affinity for phosphorus, with up to 0.53 wt pct dissolved in this phase. The optimum conditions for acid leaching were grain size, 75-106 μm; leaching time, 6 hours; leaching temperature, 338 K (65 °C); liquid–solid ratio, 6:1; and HCl concentration, 4.0 mol L−1. Using these conditions, the mass fractions of P in C-MG-Si and S-MG-Si were reduced from 105 × 10−6 and 76 × 10−6 to 48 × 10−6 and 61 × 10−6, respectively, with removal efficiencies of 54.3 and 19.7 pct, respectively. Besides, the investigation suggested that adding HF was beneficial for the removal of most impurities. After 6 hours of leaching MG-Si with a mixture composed of 4.0 mol L−1 HCl and 3.0 mol L−1 HF, the purity of C-MG-Si and S-MG-Si were increased from 97.55 and 99.31 pct to 99.91 and 99.87 pct, respectively, with extraction efficiencies of 96.14 and 81.59 pct, respectively. The etching results reveal that the HCl-HF mixture was an effective lixiviant for dissolving impurity inclusions in both C-MG-Si and S-MG-Si.

Evaluation of Anthelmintic Efficacy of Ivermectin, Levamisole HCl and Albendazole Administered through Different Routes against Naturally Occuring Gastrointestinal Nematodiasis in Black Bengal Goat Inducing Hematological Parameters and Live Weight Indices

This study aimed to evaluate the efficacy of ivermectin, levamisole HCl and albendazole against gastrointestinal nematodes in naturally infected goats of government goat development farm, Sylhet, Bangladesh. The study included 52 black Bengal breed of which 30 were naturally infected and randomly selected 20 on the basis of their weight and egg count. Twenty black Bengal goats of 12-13 month old irrespective of sex infested with gastrointestinal nematodes were selected for this experiment and randomly divided into four equal groups (group A, B, C and D) where each group consisted of 5 goats and goats of group D were kept as control group. One injectable ivermectin (200?gkg-1 body weight, S/C) preparations (Techno Drugs Ltd. Bangladesh) and two solid levamisole HCl, albendazole (7.5 mgkg-1 body weight, orally) preparations (The ACME Laboratories Ltd. and Square Pharmaceuticals Ltd. Bangladesh) were used for positive control of gastrointestinal nematodes as group A, B and C. Goats of group D was kept as control without giving any treatment. Before trials (day 0), total egg count, blood samples and initial body weight were recorded. During the study period the fecal and blood samples were collected directly from rectum and examined on 7th, 14th, 21st and 28th day using McMaster fecal egg counting method. Body weight was recorded on day 28 following the treatments. The results of the comparative efficacies of different anthelmintic of ivermectin was 86.75%, followed by levamisole HCl 85.07% and albendazole 92.81%. McMaster fecal egg counting method discloses the percentage of Haemonchus spp. (15.38%), with Trichostrongylus spp, Strongyloides spp., and Cooperia spp. also present. After treatment with ivermectin, levamisole HCl and albendazole, Total Erythrocyte Count (TEC), Hemoglobin (Hb) content and Packed Cell Volume (PCV) were increased significantly (p<0.01 and p>0.05) in goats but Erythrocyte Sedimentation Rate (ESR) and Total Leukocyte Count (TLC) were decreased significantly (p<0.05 and p>0.01) in all treated goat and body weight was increased significantly (p<0.01) on day 28.International Journal of Natural Sciences (2015), 5(1) 26-34

Chlorine leaching of Au from copper anode slimes using the response surface method in an agitated reactor

The response surface methodology (RSM) was employed to study the interactions among different factors (i.e. temperature, liquid to solid ratio, HCl concentration and chlorine gas flowrate) involved in the leaching of Au from copper anode slimes. The interactions such as liquid to solid ratio, chlorine gas flowrate×temperature and HCl concentration×temperature were found to be statistically significant. Under the optimum operational conditions of Cl2 = 1·99 L min−1, 10 000/T = 28·7 K−1, L/S = 12·57 L kg−1, HCl = 2·74 mol L−1 in a semi-pilot 3-L agitated reactor, the maximum recovery achieved for Au was around 93% using the second polynomial equation. This led to a selectivity factor (i.e. the ratio of ‘Au reaction fraction’ to the sum of ‘Se and Cu reaction fractions’) of 86. Process optimisation was carried out based on the maximum selectivity factor achieved. This resulted in the following optimum conditions: Cl2 = 1·26 L min−1, 10 000/T = 30·83 K−1, L/S = 5 L kg−1 and HCl = 2·66 mol L−1, with a separation factor of 112.

Moisture requirements to reduce interfacial sub-oxides and lower hydrogen pre-bake temperatures for RPCVD Si epitaxy

In silicon epitaxy technology, residual O/H2O contamination requires thermal reduction using hydrogen pre-bakes to achieve atomically clean Si surfaces. This H2 pre-bake leads to unwanted increase of thermal budget. The higher the level of interfacial O, the longer the pre-bake period and the higher the temperature have to be for removal of these contaminants. Moisture contamination from the pre-epi chamber etch (immediately before the wafer is loaded), with it's use of high flows of HCl, is identified as a major contributor to the area density of the interfacial O. Stringent control of moisture impurity in the HCl is required to reduce thermal budget. Ultra low temperature technology to desiccate HCl is used to achieve single digit ppb moisture resulting in lower temperature hydrogen pre-bakes than achieved with standard solid media-type HCl purification.

HCl Adsorption and Ionization on Amorphous and Crystalline H2O Films below 50 K

Molecular beams were used to grow amorphous and crystalline H(2)O films and to dose HCl upon their surface. The adsorption state of HCl on the ice films was probed with infrared spectroscopy. A Zundel continuum is clearly observed for exposures up to the saturation HCl coverage on ice upon which features centered near 2530, 2120, 1760, and 1220 cm(-1) are superimposed. The band centered near 2530 cm(-1) is observed only when the HCl adlayer is in direct contact with amorphous solid water or crystalline ice films at temperatures as low as 20 K. The spectral signature of solid HCl (amorphous or crystalline) was identified only after saturation of the adsorption sites in the first layer or when HCl was deposited onto a rare gas spacer layer between the HCl and ice film. These observations strongly support conclusions from recent electron spectroscopy work that reported ionic dissociation of the first layer HCl adsorbed onto the ice surface is spontaneous.

High-pressure phase transitions of solid HF, HCl, and HBr: Anab initioevolutionary study

Using ab initio evolutionary methodology for structure predictions, we investigated the high-pressure phase diagram for solid-state HF, HCl, and HBr at zero temperature. The ambient-pressure chain-type $Cmc{2}_{1}$ structure and sequent high-pressure symmetric hydrogen-bonded $Cmcm$ structure were successfully reproduced by structural simulations with the only known information of chemical compositions. We have also presented insight into the underlying mechanism of hydrogen-bond symmetrization at the $Cmc{2}_{1}\ensuremath{\rightarrow}Cmcm$ transformation, by analysis of electron localization functions, potential wells, and zone-center phonons with pressure. At higher pressures, it was predicted that HF transforms from the $Cmcm$ phase to another chain-type $Pnma$ structure at $\ensuremath{\sim}143\text{ }\text{GPa}$ while the post-$Cmcm$ phase of HCl and HBr adopts an intriguing triclinic $P\overline{1}$ structure at above 108 GPa and 59 GPa, respectively, which consists of nearly planar squares resembling the ambient phase of HI. The newly predicted high-pressure phases of these halides all contain symmetric hydrogen bonds and satisfy lattice dynamical stability. As for the earlier proposed dissociation of HBr, we found that this can only occur at rather high pressures (above 120 GPa) with the formation of monatomic Br and solid ${\text{H}}_{2}$.

Investigations into extracting gold from gold-containing magnesium fraction by chlorination

The prospects of chloride sublimation in the technology of mineral raw materials are due to the high chemical activity of chlorine, which provides the completeness and complexity of extracting valuable components from the starting raw material. This process is especially important for persistent difficult-to-concentrate materials which are complex and not very efficiently processed by other methods. The necessity of carrying out oxidizing annealing of the Au-containing magnetic fraction is established and its production parameters are determined. By the results of our analysis, a chlorinating agent is selected for the chloride sublimation of gold. It is revealed that the rate of interaction between gold and gaseous chlorine is sufficiently higher than with the use of solid chlorides or HCl. The dependences of gold extraction on the temperature and duration of the process during chloride sublimation are presented.

FASTDXL: A Generalized Screen to Trap Disulfide-Stabilized Complexes for Use in Structural Studies

Structural studies of macromolecular complexes have produced extraordinary insights into a wide variety of biological processes. Unfortunately, as structural biologists pursue larger and more challenging assemblies, weakly stable and/or nonspecific interactions can become significant roadblocks to structure determination. We have developed a rapid and effective pool-based screen, termed FASTDXL (focused array screening technique for disulfide X-linking), to produce and identify disulfide-stabilized protein-nucleic acid assemblies. A significant strength of FASTDXL is that it can take advantage of prior structural knowledge about molecular interactions, but does not necessarily rely upon it. A detailed application of the approach to the difficult problem of trapping a bacterial primase-ssDNA complex is described, validating the method as a route toward obtaining diffracting crystals suitable for structure determination.

VACUUM ULTRAVIOLET ABSORPTION SPECTRA OF SOLID HYDROGEN HALIDES

Absorption spectra of solid HCl, HBr and HI films deposited on LiF single crystals cooled at 103–104 K and those annealed have been obtained in the 4–11.5 eV region. The first peaks found around the absorption edges correspond to the first bands (dissociative) in isolated molecules, so that they are regarded as Frenkel exciton peaks. The spectral feature of as-deposited films changed after annealing irreversibly, which suggests the structural transition from an amorphous phase to a crystalline phase in HCl and HBr. In HI, it was revealed that the first band in the gaseous phase consists of three components. The broad structures found above the first peaks do not resemble the structures of the isolated molecules in the same energy region which consist of many lines. The band structures of solid hydrogen halides seem to resemble those of sodium halide crystals and solid rare gases.

Evaluation of depth profiling using laser resonant desorption as a method to measure diffusion coefficients in ice.

Diffusion of gases in ice is involved in cloud, snow, and ice core chemistry, but few data exist on the relevant diffusion coefficients. A novel method to measure diffusion coefficients in ice has recently been proposed by Livingston et al. (Anal. Chem., 2000, 72, 5590-5599). It is based on depth profiling of doped ice crystals epitaxially grown on Ru(001) by laser resonant desorption (LRD). Using this method, Livingston et al. obtained a value of the diffusion coefficient of the HCl hydrate in ice at 190 K of about 5 x 10(-11) cm2/s. We argue here that this value is many orders of magnitude higher than what could be expected from literature values, which are not reported in sufficient detail by Livingston et al. We investigate the possibilities that their high value could be due to (1) diffusion in defects in the ice, which would be present in very high concentrations because of the ice growth method; and (2) the fact that diffusion of high concentrations of HCl in ice at 190 K forms an amorphous HCl:H2O solid mixture, where HCl diffusion is fast. We present new infrared spectroscopic data on solid HCl:H2O mixtures that confirm that such mixtures can indeed be formed in an amorphous state at 190 K. Our proposed interpretation is that by depositing large amounts of HCl on epitaxially grown ice, Livingston et al. created a superficial amorphous binary mixture and that fast diffusion of HCl in the ice, possibly accelerated by a high defect density, produced an amorphous HCl:H2O mixture. We conclude that the processes studied by Livingston et al. are different from those involved in the atmospheric and cryospheric sciences, and that their data, obtained by depth profiling using LRD, probably cannot be applied to those fields.

Photochemical and chemical oxidation of mexiletine and tocainide. Structure elucidation of the major products.

Mexiletine (mex) and tocainide (toc) are antiarrhythmic drugs of closely related structure. Several degradation products are formed by interaction with both light and oxidizing agents in the case of mex, and only by oxidants with toc. On the basis of the identified structures, the decomposition reactions can be classified into two types (Scheme 1). Type I is an oxidative cyclization reaction producing the oxazepine derivative 1 from mex and the diazepine derivative 3 from toc. In reaction type II side chain oxidized products (2 or 4 and 5) are formed. While tocainide.HCl has proved to be photostable, in solid mexiletine HCl the oxazepine derivative was observed after several days' exposure to direct sunlight. The pharmacopoeias (Ph.Eur.3, USP 23), however, do not prescribe light-protection for mex.HCl.

Raman study of phase transition and hydrogen bond symmetrization in solid DCl at high pressure

Phase transitions in solid DCl have been investigated by Raman spectral measurement up to 70 GPa at 298 K. The I-III phase transition accompanied by orientational ordering of the molecules took place at $19.0\ifmmode\pm\else\textpm\fi{}0.5\mathrm{GPa},$ exactly the same pressure as observed for solid HCl. A further transition with hydrogen bond symmetrization (III-IV transition) was observed at about $56\ifmmode\pm\else\textpm\fi{}2\mathrm{GPa}$ higher by 5 GPa than the symmetrization pressure of HCl previously determined. The bond symmetrization is realized when the midpoint barrier separating two potential minima along the hydrogen-bonding axis is depressed and smeared out quantum mechanically. The observed isotope effects on the symmetrization pressure are hence interpreted in terms of proton (deuteron) tunneling transfer in the hydrogen bonding potential, which gradually is deformed toward a single minimum shape with increasing pressures.

High-pressure Brillouin study of solid HBr at pressures up to 7 GPa

High-pressure Brillouin scattering measurements have been carried out in orientationally disordered (OD) phases I and I′ of solid HBr, which yielded the first determination of acoustic velocities for all directions, the refractive index, the polarizability, the density, adiabatic elastic constants (C11, C12, and C44), bulk modulus, and the elastic anisotropy as a function of pressure up to 7 GPa and at room temperature. The I→I′ phase transition in solid HBr was confirmed on the discontinuous pressure dependence at P=2.3 GPa for average errors of the least-squares fit by the analysis of in situ Brillouin spectroscopy. These elastic properties of solid HBr are compared with recent results in the OD phase I of solid HCl. We suggest that the form of the potential energy function for intermolecular forces in solid HBr is similar to that in HCl.

Hydrogen-bond symmetrization and molecular dissociation in hydrogen halids

Hydrogen chloride is a simple diatomic molecule forming a planar zig-zag chain of molecules connected by hydrogen bonds in the solid phase. Raman spectra were measured for solid HCl to 60 GPa at room temperature. The molecular stretching frequency falls toward zero at about 51 GPa, where the molecular vibrational peaks disappear and the lattice peaks remain. The spectral changes are very similar to those observed for HBr at about 42 GPa and interpreted as hydrogen bond symmetrization. Molecular dissociation into diatomic halogen molecules, which has been observed for HBr, does not occur in HCl.

Iron doped GaInP for selective regrowth around GaAs mesas

The feasibility of growing Ga 0.51In 0.49P:Fe on planar and non-planar GaAs substrates by hydride vapour phase epitaxy is demonstrated. Fe doping has been achieved by the reaction between Fe solid source and HCl gas in an ambient containing nitrogen and hydrogen of ratio 9:1. Various Fe concentrations in Ga 0.51In 0.49P:Fe were obtained by changing the temperature of the Fe source, while maintaining all the other parameters constant. This relation in the form of an Arrhenius plot is compared to the case of InP:Fe. The slope of the Arrhenius plots for both the cases is 1.44 eV and is attributed to the activation energy of a step involved in the generation of FeCl 2. The resistivity of Ga 0.51In 0.49P:Fe is of the order of 1 × 10 10 Ω ·cm. A successful selective regrowth of Ga 0.51In 0.49P:Fe around the [110] and [110] directional GaAs mesas is also demonstrated.

Thermodynamic analysis of the W–F–Si–H and W–F–Si–H–Cl systems

Chemical vapor deposition of WSi2 was studied through thermodynamic equilibrium calculations for the W–F–Si–H and W–F–Si–H–Cl systems. The calculations were made with a computer program that minimizes the Gibbs free energy by Langrangian multiplier techniques. The parameter range for these system analyses were: temperature 473 to 1073 K, pressure from 50 to 500 mTorr, and Si/W ratios of 3 to 1000. 21 gas phase species and eight solid species were included in the calculations for the W–F–Si–H system and 39 gas phase species and 15 solid species were considered for the W–F–Si–H–Cl system. At the equilibrium condition, H2, SiF4, and SiF2H2 are the most prominent gaseous species for the W–F–Si–H system while WSi2 and Si are formed in the solid phase. For the W–F–Si–H–Cl system, WSi2 and Si are formed in the solid phase, while H2, SiCl4, HCl, SiF4 and SiHCl3 are the most prominent gas phase species. The SiCl2 intermediate plays a key role in the surface activated reaction for this system.