Caustic Treatment Research Articles

Experience in Processing Alternative Crude Oils to Replace Design Oil in the Refinery

A comprehensive investigation of a highly complex petroleum refinery (Nelson complexity index of 10.7) during the processing of 11 crude oils and an imported atmospheric residue replacing the design Urals crude oil was performed. Various laboratory oil tests were carried out to characterize both crude oils, and their fractions. The results of oil laboratory assays along with intercriteria and regression analyses were employed to find quantitative relations between crude oil mixture quality and refining unit performance. It was found that the acidity of petroleum cannot be judged by its total acid number, and acid crudes with lower than 0.5 mg KOH/g and low sulphur content required repeated caustic treatment enhancement and provoked increased corrosion rate and sodium contamination of the hydrocracking catalyst. Increased fouling in the H-Oil hydrocracker was observed during the transfer of design Urals crude oil to other petroleum crudes. The vacuum residues with higher sulphur, lower nitrogen contents, and a lower colloidal instability index provide a higher conversion rate and lower fouling rate in the H-Oil unit. The regression equations developed in this work allow quantitative assessment of the performance of crucial refining units like the H-Oil, fluid catalytic cracker, naphtha reformer, and gas oil hydrotreatment based on laboratory oil test results.

Multi-objective optimization of weight reduction process parameters of micropolyester woven fabrics using Taguchi gray relational analysis

The weight loss process variables of alkali-treated micropolyester woven fabrics were optimized and reported in this study. The gray relational analysis with the help of the Taguchi technique was efficiently used to optimize the key variables of this process. The caustic soda concentration, treatment temperature, and weight loss machine speed were considered the control or design parameters. The weight reduction percentage, air permeability, tensile strength, and thermal resistance of alkali-treated woven polyester fabrics were also considered as responses in this study. The experiments were implemented according to a 33 full factorial design. The levels of the control parameters which yield the maximum weight reduction, tensile strength, air permeability, and minimum thermal resistance of the treated polyester fabrics were found to be the sodium hydroxide concentration, and treatment temperature with the highest levels, and machine speed with the lowest level. This means that a 27% caustic soda concentration, treatment temperature of 125°C, and machine speed of 40 m/min exhibited the optimum properties of the treated micropolyester fabrics. It was also proved that the treatment temperature is the most influential factor affecting the micropolyester fabric’s properties. The confirmation test, which was carried out in this study, confirmed that the gray relational analysis improved the alkali-treated polyester fabric properties.

Spent caustic treatment by electrocoagulation process: effect of electrode shape and spacing

Spent caustic treatment by electrocoagulation process: effect of electrode shape and spacing

Optimization of the Caustic Treatment of Jet-Fuel to Reduce the Consumption of Caustic Soda in an Oil Refinery

Jet-Fuel desulfurization is one of the most important processes in the petroleum industries due to the high quality required for aviation fuels. In the pre-sent work, the desulfurization of Jet-Fuel with a content of sulfurous compounds was studied using a process assisted with sodium hydroxide. It was considered that the composition of the turbo fuel varies because different blends of crude oil are processed in the refinery under study. The effects of operating conditions, such as reaction time (15 to 30 min) and the amount of caustic soda (NaOH) in its solution (0.024 to 0.2 mol/L) were investigated. The objective functions (responses) were the NaOH consumption and the total cost of production while the acidity and the total sulfur content of Jet-A1 were considered as restrictions. The optimal conditions of the proposed model were obtained using the optimization with the fmincon function of the MATLAB software. These optimal conditions were found to vary according to the content of sulfur compounds present in the process feed. From the optimal points obtained, it was possible to determine the frequency of change of the NaOH solution that allows its maximum use.

Monocyclic aromatic hydrocarbons production from NaOH pretreatment metallized food plastic packaging waste through microwave pyrolysis coupled with ex-situ catalytic reforming

Metallized food plastic packaging waste (MFPPW), as found in packaging bags like potato chips and coffee, presents an intricate structural and compositional complexity, rendering its recycling considerably more challenging in comparison to pure plastic packaging. In this work, a process route to produce monocyclic aromatic hydrocarbons (MAHs) from caustic (NaOH) treatment MFPPW through microwave pyrolysis coupled with ex-situ catalytic reforming was proposed. NaOH pretreatment disrupted the chemical bonds between the plastic layers and aluminum layer, reducing the complexity of the subsequent pyrolysis reaction. The removal of the aluminum layer diminished its shielding effect on the microwave, and enhanced the efficient conversion of the microwave energy into heat energy, thus accelerating the pyrolysis of the remaining plastic. After pretreatment, the activation energy for the pyrolysis reaction decreased from 250.55 kJ/mol to 189.70 kJ/mol, and the MAHs content of the liquid oil increased. The highest MAHs content of 80.50% was achieved with an HZSM-5 (Si/Al = 50) zeolite catalyst, pyrolysis temperature of 550°C, and catalysis temperature of 550°C. The unique characteristics of the MFPPW demonstrate its suitability for MAHs production. MFPPW is predominantly composed of PP and PET polymers. PP, as a hydrogen-rich plastic, provides abundant hydrogen-rich free radicals to the PET and promotes hydrogen transfer reactions, thus facilitating the formation of MAHs. Following pretreatment, these two polymers come into closer contact, further enhancing their synergy. This study provides valuable insight into waste management and recovery for metallized food plastic packaging waste.

Investigation of spent caustic effluent treatment by electro-peroxone process; cost evaluation and kinetic studies

Spent caustic is an extremely polluted industrial wastewater with quite complex chemistry and various environmental negative impacts. Conventional wastewater treatment methods are not adequately efficient for the remediation of spent caustic. In the present work, for the first time, the treatment of spent caustic effluent was investigated by the Electro-Peroxone (EP) method as a subdivision of Advanced Oxidation Processes (AOPs). The Central Composite Design (CCD) was employed to optimize the operational parameters, including initial COD, applied current, pH, and ozone flow rate in the removal of COD. The statistical investigations showed an acceptable determination coefficient and a suitable second-order model. The predicted optimal circumstances were as the following: initial COD = 1076 mg. L-1, applied current = 0.79 A, pH = 7.9 and O3 flow rate = 1.68 L.min−1. At optimum points, the predicted and actual COD removal percentages were 96.3 and 95.0 %, respectively. The kinetic investigations showed that the removal of COD followed the first-order kinetic with the half-life and constant reaction rate at 18 min and 0.038 min−1, respectively. The specific energy consumption (SEC) value in the EP process was calculated at 33.96 kWh/Kg COD removal, showing that the combined EP process could be a cost-effective technique for the treatment of spent caustic effluent on an industrial scale.

Assessment of sulfate radical-based advanced oxidation and electrocoagulation processes for spent caustic treatment from olefin unit

Assessment of sulfate radical-based advanced oxidation and electrocoagulation processes for spent caustic treatment from olefin unit

Purification of Industrial Effluent by Gas Hydrate-based (HyPurif) Process

This study presents a sustainable HyPurif process for managing and recycling industrial water effluent, utilizing gas hydrate-based technology to purify complex effluent. This work purifies two effluents: one from a wastewater treatment plant (WWTP) and the other from a spent caustic treatment plant (SCTP). Various hydrate formers, including propane, HFC134a, and cyclopentane (6 mol %), were selected, as they typically form hydrates closer to ambient conditions. Hydrate formation experiments with effluent water were performed at 278.30 K using pure propane and HFC134a gas. Based on the kinetics of hydrate growth, the study was extended to a mixture (50:50%) of propane and HFC134a, operating at a pressure of 0.6 MPa. The mixture of propane and HFC134a has shown the desired result of forming the hydrate in the gas phase and having high separation efficiency. The results showed that the formation and dissociation of hydrates resulted in a separation efficiency of 80–95%. For instance, in the purified water, the biological oxygen demand (BOD) decreased from 2097 mg/L in the effluent sample to 220 mg/L in purified water (purification efficiency of 90.5%). The chemical oxygen demand (COD) decreased from 3100 mg/L in the effluent sample to 503 mg/L in purified water (purification efficiency of 84%). Total dissolved solids (TDS) were reduced from 89,632 mg/L in the effluent water to 14,698 mg/L in purified water (purification efficiency of 84%). Total suspended solids (TSS) were reduced from 35 mg/L in the effluent water to 3.5 mg/L in purified water (purification efficiency of 90%). However, the purification efficiency for free ammonia and residual chlorine was lower. The concentration of free ammonia decreased from 7 mg/L in the effluent sample to 1.89 mg/L in the purified water (purification efficiency of 73%), and residual chlorine reduced from 0.8 mg/L in the effluent sample to 0.2 mg/L in the purified water (purification efficiency of 75%). Water recovery of ≥40% was achievable per pass, which could be increased, but at the expense of purification efficiency. To the best of our knowledge, this is the first study on the purification of such complex wastewater containing organic and inorganic compounds, heavy metals, and various minerals using the HyPurif process.

Caustic and enzymatic effects on dissolving pulp and its performance as specialty fiber

Abstract The aim of this study was to investigate an effective approach for improving the dissolving pulp properties for making specialty fiber. The caustic and enzymatic treatment of the properties of dissolving pulp was conducted by analyzing the macromolecular structure and chemical composition. The results showed that the enzymatic treatment was more effective on influencing the macromolecular properties, while the caustic treatment had more influence on structural changing, mainly cellulose crystal structure and crystallinity. Meanwhile, to maintain a higher purity and higher brightness, caustic treatment would be beneficial in comparison with enzymatic treatment. The performance of caustic treated sample was evaluated in regarding to chemical composition and acetylation reaction performance, using commercial pulp as reference. The competitive feature of treated sample suggested its potential in future application.

Caustic oesophageal stricture treated by instrumental dilatation: A review of 6 years of practice at the pediatric university hospital charles de gaulle of Ouagadougou.

Oesophageal stricture is one of the most important and redoubtable complications following caustic ingestions in children. Instrumental dilatation is usually considered the first line of treatment. This study aims to evaluate the outcomes of caustic stenosis treatment when using Lerut dilatators. This is a descriptive retrospective study from May 2014 to April 2020. All children under 15 years hospitalised in our department for caustic oesophageal stricture and had a gastrostomy and oesophageal dilatation with insertion of an endless wire were included. A total of 83 patients were included. The sex ratio was 2.2. The mean age was 4 years. The mean time from caustic ingestion to presentation was 90 days. Oesophageal stricture was mostly caused by caustic soda (n = 41) and potash (n = 15). We performed in total 469 dilatations and had only three oesophageal perforations. After a mean follow-up of 17 months, we had 60.2% good results (n = 50) and 7.2% (n = 6) failures. The mortality rate was 13.2% (n = 11). The results of the dilations by Lerut dilatators give encouraging results in our department. It is easy to perform and its complications remain rare. Mortality could be reduced by adequate nutritional support.

Efficient Removal of Ammonia Nitrogen by an Electrochemical Process for Spent Caustic Wastewater Treatment

Spent caustic wastewater produced in a soda plant has a high concentration of ammonia nitrogen (NH4+-N). As excessive NH4+-N discharging into water bodies would cause eutrophication as well as destruction to the ecology balance, developing an efficient technology for NH4+-N removal from the spent caustic wastewater is imperative in the current society. In this study, an electrochemical process with graphene electrodes was designed for the NH4+-N removal in the spent caustic wastewater. The removal efficiency of the NH4+-N during the electrochemical process could reach 98.7% at 4 A in a short treatment time (within 120 s) with an acceptable energy consumption (6.1 kWh/m3-order). NO3− and NO2− were not detected during the electrochemical process. An insignificant amount of NH2Cl, NHCl2, and NCl3 produced in the treatment suggested that little of the NH4+-N reacted with chlorine, that is, chlorination played a negligible role in the NH4+-N removal. By electron equilibrium and nitrogen conversion analysis, we think that NH4+-N was primarily converted to NH2(ads) on the surface of a graphene electrode by one-electron transfer during the direct oxidation of the electrochemical process. Due to the high calcium ion (Ca2+) in the spent caustic wastewater, the electrode scale significantly increased to 1.4 g after treatment of 240 s at 4 A. By X-ray diffraction (XRD) analysis, the composition of the electrode scale is portlandite Ca(OH)2. Although the electrode scale was obvious during the electrochemical treatment, it could be alleviated by alternating the electrode polarity. As a result, the life and efficiency of the graphene electrode for NH4+-N removal could remain stable for a long time. These results suggest that the electrochemical process with a graphene electrode may provide a competitive technology for NH4+-N removal in spent caustic wastewater treatment.

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites.

The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH4VO3 to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, 51V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)2(HO)V=O and (SiO)3V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HYdeSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)3V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C.

Assessment of the Potential of Using Nanofiltration Polymeric and Ceramic Membranes to Treat Refinery Spent Caustic Effluents.

Spent caustic effluents are very challenging due to their very hazardous nature in terms of toxicity as well as their extreme pH (approximately 12–14). Spent caustic has presented a challenge for wastewater treatment in refineries, due to its composition rich in mercaptans, sulfides and other aromatic compounds. To address such problems, membrane filtration was studied using real effluents from Sines Refinery, in Portugal. The present study attempts to assess the potential for spent caustic treatment with nanofiltration (NF) polymeric and ceramic membranes, assessing membrane life expectancy. For that, membrane aging studies in static mode were performed with the polymeric membrane before attempting NF treatment (dynamic studies). A ceramic membrane was also tested for the first time with this type of effluents, though only in dynamic mode. Although the polymeric membrane performance was very good and in accordance with previous studies, its lifespan was very reduced after 6 weeks of contact with spent caustic, compromising its use in an industrial unit. Contrarily to expectations, the ceramic membrane tested was not chemically more resistant than the polymeric one upon direct contact with spent caustic (loss of retention capacity in less than 1 h in contact with the spent caustic). The results obtained suggest that a pH of 13.9 is very aggressive, even for ceramic membranes.

Influence of Hollander beater refining on xylan extraction from hardwood paper pulp by cold caustic extraction and xylanase treatment

Cellulose fibers’ complex and compact structure hinders the quantitative extraction of residual hemicelluloses from the fiber wall. In this study, hardwood kraft paper pulp was subjected to refining with a Hollander beater at different refining loads (3, 4.5, and 5.5 kg) in order to assess the impact of refining load on xylan removal by cold caustic extraction. The refined pulp showed high water retention values and specific surface area, which increased accessibility and a correspondingly high degree of xylan removal. Coupling refining and cold caustic extraction (100 g/L soda) achieved over 50% more xylan removal than the unrefined pulp (3% against 7%, respectively). Furthermore, an improvement in xylan removal (79%) was achieved by implementing a one-pot simultaneous refining and cold caustic extraction treatment at half the time required for the sequential treatment and low soda concentration (60 g/L). Finally, the benefit of beating was also observed for xylanase treatment. Overall, the combined extractions made it possible to remove 85% of xylan from a conventional hardwood paper pulp giving rise to a high purity cellulose pulp with unimodal and narrow molecular mass distribution.

Performance of Liquid Eversa on Fatty Acid Ethyl Esters Production by Simultaneous Esterification/Transesterification of Low-to-High Acidity Feedstocks

Liquid Eversa was evaluated in hydrolysis of acylglycerols from soybean oil deodorizer distillate (SODD), as well as simultaneous esterification/transesterification of SODD with low-to-high free fatty acids (FFAs) content using ethanol as acyl acceptor. Hydrolysis of SODD at mild temperature (37 °C) and without pH control (water:SODD mass ratio of 4:1) increased its FFAs content from 17.2 wt.% to 72.5 wt.% after 48 h reaction. A cold saponification of SODD allowed a saponification phase (SODD-SP) to be recovered with 93 wt.% saponification index and 2.25 wt.% FFAs content, which was used to find the experimental conditions for simultaneous esterification/transesterification reactions by experimental design. Temperature of 35 °C, enzyme concentration of 8.36 wt.%, and molar ratio of 3.64:1 (ethanol:SODD-SP) were found as the best conditions for fatty acid ethyl esters (FAEEs) production from SODD-SP (86.56 wt.% ester yield after 23 h reaction). Under the same reaction conditions, crude SODD (17.2 wt.% FFAs) and hydrolyzed SODD (72.5 wt.% FFAs) yielded products containing around 80 wt.% FAEEs. Caustic treatment could increase the ester content to around 90 wt.% and reduce the FFAs content to less than 1 wt.%. Our results show the good performance of liquid Eversa in aqueous (hydrolysis reactions) and organic (esterification/transesterification reactions) media.

Study of kerosene caustic wash process for jet fuel production

Caustic wash is one of many industrial processes that are used to produce jet fuel. In this study, an analysis of the key parameters of the kerosene caustic wash process was conducted to improve the total performance of the treatment process. The investigated parameters are caustic concentration (from 0.03 to 3.0 wt%), caustic volume (from 110% of theoretical to 250%), number of treatment stages (one and two stages), wash water type (demineralized water and alkaline soft water), and wash water volume (10% and 30% of kerosene feed volume). Results revealed that the reaction between sodium hydroxide and naphthenic acids is a diffusion-controlled chemical reaction. The diluted caustic solutions (0.5 wt%) are better than the concentrated ones (3 wt%). Higher excess caustic volume has a slight effect on kerosene acidity. Performing the caustic treatment process in one stage is sufficient, and the two-stage process has no effect on acidity. Washing caustic-treated kerosene with demineralized water (pH=7) has a slight adverse effect on kerosene acidity. Increasing the demineralized water volume results in a slight increase in the acidity of the treated kerosene. Wash water should be slightly alkaline (pH 7.5–8) to prevent the reverse reaction of sodium naphthenates back into naphthenic acid. Increasing wash water volume (more than 10 vol% of kerosene feed) has no noticeable effect on the water content of treated kerosene.

The effect of caustic soda treatment to recover rare earth elements from secondary feedstocks with low concentrations

Caustic soda (NaOH) treatment has enhanced rare earth element (REE) extraction from monazite. This study examined the effectiveness of caustic soda for RE-phosphates with lower concentrations for extraction from coal overburden, an alternative feedstock derived from mining waste. Pourbaix (Eh-pH) diagrams were constructed for La, Ce, Nd, Eu, and Y-PO4-H2O systems to understand the thermodynamics of NaOH-facilitated acid leaching for low-concentration RE-phosphates and oxides and to elucidate the difference in recoveries among individual REEs. The Eh-pH diagrams indicated that low crystallinity is beneficial for extraction. Nd was thermodynamically most favorable for the extraction process among the five elements examined, and Y was the least promising. Experiments were conducted using three Pennsylvania coal overburden samples to validate the effect of caustic soda on rare earth leaching. The experimental results showed that for NaOH (6 M), a leaching time of 2 h at 125 °C was sufficient to obtain twice the recovery values compared to those without the NaOH treatment. After implementing the caustic soda treatment, a high total REE recovery (>60%), especially for Nd and Pr, could be achieved with diluted HCl and more environmentally friendlier citric acid. The results were similar for both coarse and fine particles. This novel approach is likely to improve the feasibility of REE extraction from coal-associated feedstock in a more environmentally benign manner.

Removing sulfide from spent caustic petrochemical wastewater with electro-Fenton treatment

Spent caustic is a particularly harmful wastewater from petrochemical industries. It has a complex mixture of components, causing problems and difficulties for conventional treatment processes. In this study, electro-Fenton treatment was investigated as an advanced oxidation process (AOP) for the removal of sulfide from synthetic spent caustic. The effects of contributing factors such as pH, electrode distance, voltage, hydrogen peroxide (H2O2) concentration and time on sulfide removal were experimentally scrutinized. It was shown that under the optimum conditions, sulfide removal reached 97% and that the most influential factors were reaction duration and peroxide concentration. Interestingly, when adequate reaction times (above 30 min) were provided, changes in electrode distance and voltage were shown to be inconsequential. A pH of 5 and peroxide dosage above 0.5 mL/L were most effective. In order to illustrate the interaction of the independent variables on sulfide removal, statistical modeling was also carried out followed by optimization and prediction analysis. Highlights The electro-Fenton process was used for spent caustic treatment. Effects of pH, electrode distance, voltage, H2O2 concentration and time were studied. Importantly, at t > 30 min, electrode distance and voltage became insignificant. At 4.5–6.5 pH and 0.45–0.65 mL/L H2O2, optimum results are obtained. Under optimum condition 97% removal of sulfide was achieved.

Extraction and application of cellulose microfibers from Washingtonia palm as a reinforcement of starch film

This work aims to optimize the industrial extraction conditions of cellulose microfibers (CMFs) from Washingtonia palm fiber for application in starch bio-composite films. The CMF extraction was a mixed process that combines caustic soda treatment with hydrogen peroxide bleaching in a stirred thermostatic bath. To study the yield, whiteness index and α-cellulose content, three variables were selected; NaOH and H2O2 concentrations and treatment time. The optimum was determined using a Response Surface Methodology (RSM) approach for samples treated for 70 min with 5.21% NaOH and 5.54% H2O2. The optimized CMF was used to produce Starch/CMF bio-composite films with higher mechanical and barrier performance, which increased by 300% and 31%, respectively. Moreover, its moisture absorption and water solubility decreased by about 24% and 26%, respectively after adding 20 wt% CMF. In fact, morphological results showed that the higher CMF in the Starch/CMF20 leads to the heterogeneous CMF distribution and agglomerates resulting in weakened starch films. As a result, the extracted CMF can be a competitive nanofabrication filler.

Highly Efficient Semi-Continuous Extraction and In-Line Purification of High β-O-4 Butanosolv Lignin.

Innovative biomass fractionation is of major importance for economically competitive biorefineries. Lignin is currently severely underutilized due to the use of high severity fractionation methodologies that yield complex condensed lignin that limits high-value applicability. Mild lignin fractionation conditions can lead to lignin with a more regular C-O bonded structure that has increased potential for higher value applications. Nevertheless, such extraction methodologies typically suffer from inadequate lignin extraction efficiencies and yield. (Semi)-continuous flow extractions are a promising method to achieve improved extraction efficiency of such C-O linked lignin. Here we show that optimized organosolv extraction in a flow-through setup resulted in 93–96% delignification of 40 g walnut shells (40 wt% lignin content) by applying mild organosolv extraction conditions with a 2 g/min flowrate of a 9:1 n-butanol/water mixture with 0.18 M H2SO4 at 120°C in 2.5 h. 85 wt% of the lignin (corrected for alcohol incorporation, moisture content and carbohydrate impurities) was isolated as a powder with a high retention of the β-aryl ether (β-O-4) content of 63 linking motifs per 100 C9 units. Close examination of the isolated lignin showed that the main carbohydrate contamination in the recovered lignin was butyl-xyloside and other butoxylate carbohydrates. The work-up and purification procedure were investigated and improved by the implementation of a caustic soda treatment step and phase separation with a continuous integrated mixer/separator (CINC). This led to a combined 75 wt% yield of the lignin in 3 separate fractions with 3% carbohydrate impurities and a very high β-O-4 content of 67 linking motifs per 100 C9 units. Analysis of all the mass flows showed that 98% of the carbohydrate content was removed with the inline purification step, which is a significant improvement to the 88% carbohydrate removal for the traditional lignin precipitation work-up procedure. Overall we show a convenient method for inline extraction and purification to obtain high β-O-4 butanosolv lignin in excellent yields.