Aqueous Caustic Solution Research Articles

Bivalent copper oligopyrocatecholate as a novel heterogeneous catalyst for the oxidative degradation of mercaptan in caustic solution: Synthesis, characterization, and kinetic study

A novel catalyst based on bivalent copper oligopyrocatecholate was first successfully synthesized and dispersed in a polymer matrix for oxidative degradation of mercaptan in aqueous caustic solution. X-ray diffraction analysis has demonstrated that the synthesized catalyst was a crystalline phase with a minimum amorphous component. Mechanism analysis and kinetic experiments were conducted to investigate the kinetic mechanism of the reaction of isopropyl mercaptan oxidation catalyzed by copper oligopyrocatecholate dispersed in a polymer matrix. The influences of temperature, initial concentrations of reactants, and catalytic surface area on the reaction rate were studied to obtain the rate expression of intrinsic kinetics. The research results showed that the subsequent electron-transfer step was the rate-limiting step of the reaction. Additionally, the mercaptan oxidation rate in caustic solution was inversely proportional to the first power of the alkali concentration. The apparent activation energy was approximately 27.71 ± 1.12 kJ/mol. Importantly, this rate law for mercaptan oxidation can be used to design industrial reactors for the light oil sweetening process.

Adsorptive conversion of nitrogen dioxide from etching vent gases over activated carbon

ABSTRACTSome metal etching operations emit limited flow rates of waste gases with reddish-brown NO2 fume, which may cause visual and acidic-odor complaints, as well as negative health effects. In this study, tests were performed by passing caustic-treated waste gases vented from Al-etching operations through columns packed either with virgin or regenerated granular activated carbon (GAC) to test their adsorptive conversion performance of NO2 in the gases. The gases contained 5–55 ppm NO2 and acetic and nitric acids of below 3 ppm. Exhausted carbon was regenerated by scrubbing it with caustic solution and water, and dried for further adsorption tests. Results indicate that with an (empty bed residence time (EBRT) of 0.15 sec for the gas through the GAC-packed space, around 60% of the influent NO2 of 54 ppm could be removed, and 47% of the removed NO2 was converted by and desorbed from the carbon as NO. GAC used in the present study could be regenerated at least twice to restore its capacity for NO2 adsorption. Within EBRTs of 0.076–0.18 sec, the adsorptive conversion capacity was linearly varied with EBRT. In practice, with an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)−1 with an influent NO2 of 40 ppm can be used as a basis for system design.Implications: Some metal etching operations emit waste gases with reddish-brown (yellow when diluted) NO2 fume which may cause visual and acidic-odor complaints, as well as negative health effects. This study provides a simple process for the adsorptive conversion of NO2 in caustic-treated waste gases vented from metal-etching operations through a GAC column. With an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)−1 with an influent NO2 of 40 ppm can be used as a basis for system design. Saturated GAC can be regenerated at least twice by simply scrubbing it with aqueous caustic solution.

Effect of silica fiber on the mechanical and chemical behavior of alumina-based ceramic core material

In order to improve the chemical leachability, the alumina-based ceramic core material with the silica fiber was injected and sintered at 1100 °C/4 h, 1200 °C/4 h, 1300 °C/4 h and 1400 °C/4 h, respectively. The micrographs of ceramic core materials at sintered and leached state were characterized by scanning electron microscopy (SEM). The phase composition of ceramic core material after sintering and the leaching product after leaching were detected by X-ray diffraction (XRD). The porosity, room temperature bend strength, creep property at elevated temperature and the leaching rate in aqueous caustic solution were studied. The experimental results show that the ceramic core material with silica fiber obtain a fair balance between mechanical and chemical properties at sintering of 1300 °C/4 h. Specifically, the leach rate of ceramic core material with silica fiber is increased apparently. High leaching surface and weak adhesive strength between agglomerated alumina particles are the reasons that responsible for the ceramic core material with silica fiber be leaching fast than that of the ceramic core material without fiber.

Synthesis and Characterisation of the Lithium, Sodium and Potassium Americium(β) Complexes of Hexaoxoperiodate: MI2[Am(OH)2H2IO6].xH2O

Novel complexes of trivalent Americium with hexaoxoperiodate have been prepared for the first time from an aqueous caustic solution. Chemical analysis indicated that the composition of the complexes is MI2[Am(OH)2H2IO6]. xH2O (MI= alkali metal: x = 4, MI= Na, K; X = 11, MI= Li) and all the complexes have been characterised by X-ray powder diffraction, UV-Visible, IR, and Raman spectroscopic studies, and by thermal analysis.

Novel regenerated cellulosic material prepared by an environmentally-friendly process

Novel regenerated cellulosic materials have been developed using an environmentally-friendly, facile process without releasing any toxic materials. Untreated, cellulose diacetate fibers were immersed in the aqueous caustic solution. The degummed and dried diacetate fibers were heated at a rate of 2 °C/min from 30 to 98 °C, then treated for 30 min at the same temperature and cooled at a rate of 2 °C/min to 30 °C, followed by the drainage of the liquid. The heat treated fibers were held under tension to prevent shrinkage during the thermal treatment. The materials possess excellent physical and dyeing properties, are pleasant to touch, and can be used in a variety of industrial fields. The microstructure of these materials is found to have a composite crystalline structure consisting of cellulose II and cellulose IV, exhibiting a lamellar morphology with an increased amorphous fraction, as compared to conventional rayon fibers, which is the main reason for their better elongation and solvent sorption ability.

Fully biodegradable natural fiber composites from renewable resources: All-plant fiber composites

Wood flour can be converted into thermoplastics through proper benzylation treatment, which introduces large benzyl group onto cellulose and partially deteriorates the ordered structure of the crystalline regions. By changing a series of parameters, like reaction temperature, concentration of aqueous caustic solution, species of phase transfer catalyst, etc., the extent of benzyl substitution is regulated within a wide range so that a balanced thermal formability and mechanical performance of the modified wood flour is obtained. By using the properly plasticized China fir sawdust as the matrix, both discontinuous and continuous sisal fibers are compounded to produce composites from renewable resources, respectively. These all-plant fiber composites are characterized by moderate mechanical properties and full biodegradability, and might act as alternative to petro-based materials in terms of structural applications.

Manufacture and use of chloroprene monomer

There are only six manufacturers of chloroprene (CD) located outside of the former Communist Bloc countries. Five of these manufacture chloroprene from butadiene via a two step process consisting of chlorination and subsequent dehydrochlorination. The sixth dimerizes acetylene and then hydrochlorinates the dimer to produce CD. Both the acetylene and butadiene-based manufacturing processes are conducted within sealed systems. Therefore, the only potential exposure during manufacture is sampling for product quality, strainer/filter changing and accidental leaks or spills. All six manufacturers produce CD only for the production of polymer. Manufacturers convert CD into polychloroprene polymer (PCP) via emulsion polymerization. A solution of CD and other ingredients is mixed with an aqueous caustic solution to produce an emulsion. Free radicals initiate polymerization and free radical scavengers are added to stop the reaction at the desired conversion. After unreacted monomer is removed, PCP can be sold as a latex (colloid) or isolated and dried to produce solid product. The PCP manufacturing process is also designed to be a closed system. However, the extreme reactivity of CD and the inherent stickiness of PCP polymer, makes it necessary to ‘open’ the process to remove polymer. This results in potential for operator exposure, in addition to the items mentioned for CD manufacture. With the use of appropriate engineering controls, work practices and personal protective equipment for activities with exposure potential, actual workplace exposures are controlled below the occupational exposure limits (2–10 ppm). The solid PCP products, which comprise ≈92% of the total amount of polymer manufactured, contain <1 ppm CD. Most PCP latexes contain <0.1% residual CD. So, the potential for CD industrial exposure is limited to CD and PCP manufacture.

Kinetics of saponification of hydrogenated castor oil by lithium hydroxide

ized within a few seconds at 373-413 K. In our investigation of the kinetics of the inter- action of HCO fatty acid glycerides with an aqueous caustic solution (chemically pure grade), we performed experiments at temperatures of 373, 383, 383, 403, and 413 K. HCO concentrations of 0.047, 0.093, and 0.141M in the reaction mixture were selected on the basis of normal practice in the production of soap/oil concentrates. The sapon- ification was performed in a mixture of MS-20 and 1-50A oils (7:3 by weight). In each ex- periment, an aqueous solution of lithium hydroxide (10.45%) was introduced into the reaction mixture in an amount 10% over the stoichiometric requirement for complete saponification of the HCO. In the course of saponification, samples were taken at identical intervals of time and analyzed by potentiometric titration. The experimental data were approximated on the basis of an area method (5), with a 3.5% error, by the exponential relationship

A Laboratory Study Of Caustic Flooding For Two Alberta Crude Oils

Abstract This experimental study was concerned with the recovery of the Wainright (408 mPa.s) and Horsefly (18 mPa.s) crude oils, using aqueous caustic solutions. The oil recoveries were compared with those by a waterflood. Effect of injection rate and loss of caustic to the porous medium were also examined. It was found that oil recovery was higher than that by a waterflood for the lower caustic concentrations (0.01% and 0.1% by weight), approaching a maximum of 75% of in-place oil, but not for the higher concentration (2%). Recovery was sensitive to injection rate. In the case of the Horsefly crude oil, the caustic floods were only marginally more efficient than a waterflood. In all cases, loss of the caustic to the rock and fluids was significant. Reasons for the recovery trends observed, and the prevailing flow mechanisms are discussed. Introduction Chemical flooding methods for enhanced oil recovery (EOR) have a long history, but in the last decade they have received an inordinate amount of attention from researchers and operators alike. Chemical floods have not made an impact as economical EOR methods, but they hold promise for the future. Caustic flooding is one such method, which has been tested and developed for conventional as well as heavy oil recovery. This research addresses the use of aqueous caustic solutions for the recovery of the Wainwright (a moderately viscous oil) and Horsefly (a light oil) crude oils. Apart from oil recovery, the effect of velocity was of particular interest. Selected Previous Laboratory Studies The use of chemical additives in flood water was proposed by Atkinson(l). The benefits of alkaline flood water additives were known even before this as shown by the works of Nutting(2), Uren and Fahmy(3), and Bekstrom and Van Tuyl(4). Johnson(5) performed a thorough review of the status of caustic flooding methods and classified the proposed mechanisms into the following four types. (I) emulsification and entrainment, (2) wettability reversal (oil-wet to water-wet), (3) wettability reversal (water-wet to oil-wer), and (4) emulsification and entrapment. De Zabala el al.(6) cite eight mechanisms for the alkaline flood process. The emulsification and entrainment mechanism was first proposed by Subkow(7) in relation to the recovery of bitumen. He stated that the formation of an emulsion was the essential first step in the recovery process, followed by the entrainment or this emulsion in the flowing alkali with the mixture subsequently produced. Reisberg and Doscher(8) studied the effect of pH on the oil-water interface using a Ventura, California, crude oil. They concluded that for the same interfacial tension to oil, a caustic solution will displace the oil, while an acid solution would not. They attributed this to the stability of the rigid films at the interface confirming the earlier work of Nutting(2). They concluded that caustic flooding was impractical because of adsorption on, and interaction with, the rock. Chan(9), working with Wainright crude oil, concluded emulsification of the oil to be vital for increased oil recovery. This conclusion was based on the insignificant recovery increase in tests where emulsification did not occur.

Effect of deprotonation of ion-radical pairs on yield of radicals

In the example of ion-radical pairs (IRPs) formed in electron-transfer quenching of triplet states of the dyes methylene blue and eosin (electron acceptors) by phthalohydrazides (electron donors) in aqueous caustic solutions, it has been found that phthalohydrazide radicals are deprotonated directly in the IRP during their lifetime by the external base (OH−), and a study has been made of this reaction. The yields of radicals from the deprotonated IRPs are 2–3.8 times those from the original IRPs; this difference is related to an increase in AG of IRP recombination as a result of deprotonation. In the region of high concentrations of OH−, experimentally determined dependences of the yield of radicals on [OH−] deviate from the relationships calculated with an exponential model of IRP destruction; this deviation is explained by a nonstationary nature of the diffusion of OH− to the IRP immediately after the IRP is formed.

Electrochemical behaviour of aluminium in aqueous caustic solutions

The electrochemical behaviour of pure aluminium in aqueous KOH solutions has been examined by steady state and non-steady state techniques (impedance, potential pulse, potential scan). A surface free from oxide and hydroxide could not be established at any potential. The fall in the aluminium dissolution rate and the rise in the hydrogen evolution rate with decreasing electrode potential both arise from the thinning and hydration of the oxide layer. Decrease in alkalinity causes the film to thicken and to hydrate. In the non-steady state the relatively slow changes in the oxide film lead to non-uniformity of composition and a consequent temporary surface roughening.

Focused ion beam microlithography using an etch-stop process in gallium-doped silicon

We have found that silicon, when implanted with doses of gallium in excess of 1013 ions/cm2, experiences little or no etching in aqueous caustic solutions. By exploiting a finely focused 40–50 keV gallium ion beam (0.05–0.1 μm diameter) in our scanning ion microscope, we have shown that it is possible to fabricate structures with submicrometer (0.1 μm) features. The silicon behaves as a negative resist with a sensitivity of about 1 μC/cm2. This etch-stop process is largely insensitive to crystallographic orientation, except for the highly insoluble (111) plane in which damage-promoted etching occurs.

Reactivity of hydrolysed coals in liquefaction

A hvA bituminous, a subbituminous and a lignite coal have been hydrolysed by 20–30% aqueous caustic solution at 100–300 °C and total pressure from ambient to 8.3 MPa (1200 psi). Reactivity of these pretreated coals toward liquefaction has been examined. The conversion to benzene-soluble material (BS) and oil increases, and the preasphaltene and char residue decreases after pretreatment. Improvement in the conversion to the BS fraction is only marginal for the pretreated bituminous coal, but substantial for the low-rank coals. For the subbituminous coal, the liquefaction reactivity (conversion to BS) increases with the severity of hydrolysis pretreatment. Analyses of chemical compositions, 1H n.m.r. nuclei distributions and hydroxyl concentrations of the acid-insoluble hydrolysis coal extracts indicate that both O and S are enriched in the extracts with half of the oxygen atoms being in hydroxyl forms. The hydroxyl concentrations of the extracts (acid-insoluble) are ≈2 to 3 times higher than their parent coals. Coal activation by this alkali pretreatment is explained by the hydrolytic attacks on ether C–O linkages, and the removal of some constituents rich in oxygen functional groups which are responsible for poor liquefaction behaviour.

Determination of thiosulfate sulfur in oxidized sour caustic wastes

do not have any odor and can be oxidized to harmless sulfates in biological treatment. Of presentlyavailab le methods for the quantitative determination of thiosulfates, some are complex and require the use of toxic reagents, the others are nonselective and require preremoval or masking of a number of interfering anions (iodometric methods [2] are an example of the latter type). Potentiometric methods are based on the use of toxic mercury salts as solution titrants [3,.4] and require premasking of the sulfite ion by formalin. Indirect methods of analysis for thiosulfate content [5, 6] ultimately come down to iodometry and are not free of its disadvantages. We have developed a method for the quantitative determination of thiosulfate sulfur in aqueous caustic solutions by titration with a 0.I N AgNO3 solution at pH 5-8 in a pH-340 potentiometer with silver chloride and silver sulfide electrodes. In the titration, a relatively insoluble precipitate of the sulfur salt with the anion is formed. The completeness of silver thiosulfate precipitation depends on the pH of the medium (Table i). At pH 5-8, maximum precipitation of the silver thiosulfate is achieved, and precipitation of silver hydroxide is completely avoided. Deviations of the pH from this range lower the accuracy of determination, Thus, the thiosulfate content should he determined in a neutral or slightly acidic medium. In an alkaline medium, silver nitrate hydrolyzes to precipitate silver hydroxide, so that the results obtained in the analyses will be higher than the true values. In order to avoid this, the titration with AgNOs solution in an alkaline medium is carried out with ammonia present in the titrant composition or in the support electrolyte for the titration. However, in determining the content of thiosulfate sulfur, the presence of ammonia cannot be tolerated, since it dissolves the silver thiosulfate precipitate that is formed in the titration and hence makes it impossible to perform the analysis. The required pH level is achieved by neutralizing the alkaline medium with acetic acid; the pH is determined by means of indicator paper or a pH meter. This creates a buffer medium in the solution, preventing any significant changes in pH during the course of the analysis. The analysis requires 10-15 min. The end of the precipitation of silver thiosulfate is ac

Interrelation of Crude Oil and Rock Properties With the Recovery of Oil by Caustic Waterflooding

Abstract This paper describes a series of laboratory caustic (NaOH) waterfloods and related measurements using crude oils from 19 oil reservoirs. These were light (mostly,&amp;gt;30 degrees API) crudes mainly from South Louisiana and Texas, although crude oils from other areas also were tested. The waterfloods held core material (Berea sandstone), connate water (2-percent-NaCl brine) and other conditions (temperature, flow rate, aging time before flood) constant, and determined increased production due to NaOH injection for each crude oil. Relative permeability end-points before and after flooding were used to estimate initial and final wettabilities and, together with crude-oil acid numbers and interfacial tensions against NaOH solution, to infer the probable mechanism by which increased recovery was obtained. A series of laboratory NaOH depletion measurements by static and dynamic methods in core material from several oil-producing formations and in Berea sandstone is also described. Results are compared with those from similar measurements using pure clays and other minerals and with X-ray diffraction analysis of the core material. The following are observations from these tests.Crude oils with acid numbers greater than about 0.1 to a 0.2 mg KOH per gm of oil or interfacial tension against 0.1 percent NaOH less than about 0.5 dyne/cm gave significant caustic-waterflood increased production. There was no further correlation of increased production at higher acid numbers or lower interfacial tensions nor was there a correlation with the apparent initial rock wettability.Regardless of initial wettability or increased production, the cores are indicated to be water-wet production, the cores are indicated to be water-wet following NaOH waterflooding to a high water-oil ratio (WOR).Caustic consumption by reservoir rock is predictable from the formation mineral composition predictable from the formation mineral composition as determined by X-ray methods. Exceptions are noted where clay content is high and where trace amounts of gypsum are present. Introduction Crude oils containing naturally occurring organic acids will react with aqueous caustic solution to produce surface-active materials. These surfactants, produce surface-active materials. These surfactants, when generated during a caustic waterflood, can improve oil recovery over that of a normal waterflood by a number of mechanisms related to changes occurring at the oil-water and liquid-solid interfaces: interfacial-tension lowering, wettability change, changes in interface rheology, etc. The extent to which any of these mechanisms will be operative and the recovery improvement obtainable depends on, among other things, the amount and type of acids present, the initial formation wettability, the reservoir-rock pore geometry, and the extent to which it consumes caustic. The available literature describing mechanisms proposed for caustic-waterflooding improved recovery, proposed for caustic-waterflooding improved recovery, the conditions required for applicability, and the results of various laboratory and field studies have been surveyed most recently by Johnson. Some common currents of thought or implication in this literature and some common areas of uncertainty related to the effects of crude oil and reservoir rock properties on recovery mechanisms are listed below. properties on recovery mechanisms are listed below.The presence of acids in crude oil at some minimum level is an obvious necessary condition for improved recovery. Where emulsification is involved, minimum acid numbers ranging from 0.5 to 1.5 mg KOH per gm of oil have been suggested. No minimum has been stated for other recovery mechanisms. One might not expect such minimum requirements to be absolute since the quality of surfactants generated from these acids can vary widely among crude oils.Improved recovery by wettability alteration generally has been discussed in terms of a reversal from oil-wet to water-wet or vice versa. It has been implied that wettability reversal is required since capillary forces trapping oil are eliminated as the neutral wettability condition is traversed. SPEJ P. 263

Natural Conditions for Caustic Cracking of a Mild Steel

Abstract Stressed and unstressed specimens of a mild steel (0.25% C, 1.0% Mn) were studied in aqueous caustic solutions ranging in concentration from 0.5 to 60% NaOH. Natural corrosion potentials w...

Optical Studies of Electrolyte Films on Gas Electrodes

The geometry of stable electrolyte films has been established on nickel and silver surfaces partially immersed in aqueous caustic solutions. Such films, which are very sensitive to factors affecting interfacial energies and may be useful for their determination, appear to be important for the mass transfer in certain gas diffusion electrodes.

Engineering aspects of the oxidation of mercaptans in caustic solutions: Reaction kinetics and design of reactor

A method extensively employed in the petroleum industry to remove mercaptans from hydrocarbons is extraction with an aqueous caustic solution. The mercaptans thus removed can be separated from the caustic by various methods. In one of these the caustic solution is brought into contact with air in a stirred reactor, the mercaptans being oxidized to disulphides. This heterogeneous gas-liquid reaction is governed both by factors connected with the transfer of oxygen from the gas to the liquid phase and by factors associated with the actual chemical reaction. The overall reaction rate can be controlled by the physical transfer rate and (or) the rate of the chemical reaction. Under conditions in which the latter (expressed in rate of mercaptan consumption) was determinative experiments have been carried out with a view to studying the reaction kinetics. At high mercaptan concentrations the chemical reaction rate was found to be independent of the mercaptan concentration and to vary almost proportionally with the oxygen concentration, whereas at low mercaptan concentrations the reverse was obtained. Formulae can be derived for the overall reaction rate for the different cases occurring in the mercaptan oxidation. On the basis of these formulae guiding principles can be set forth for the most suitable method of mercaptan oxidation. If the oxidation is effected in a stirred reactor, a correlation which is already known from the literature can be employed for the physical rate of oxygen transfer. Thus it has been found possible to determine the optimum reactor volume at minimum stirrer energy.

Impurities in vegetable oil refining soapstock

SummaryThe nature of the impurities in vegetable oil foots renders them resistant to treatment by acids as in normal acidulation. Strong caustic was found to attack the gums and make them at least partially soluble in a 5 to 10% aqueous caustic solution. At this concentration a soap phase of 45–60% TFA could be centrifugally separated, and the majority of the impurities or their degraded products were discharged in the lye. The ratio of Oxidized Acids and Insoluble Impurities to the TFA was much lower in the soap than in the raw soapstock; the Oxidized Acids/Black Acids ratio could generally be reduced to 5% or less. This reduction in impurities was found to improve laboratory still yields markedly without the necessity of Twitchell‐ or pressure‐ splitting the black acids from treated stocks. Distillate yields of 86–89% were obtained from treated stocks, compared to 69–70% from untreated stocks.