Artificial intelligence-based forecasting model for incinerator in sulfur recovery units to predict SO2 emissions.

Pollutant emissions from chemical plants are a major concern in the context of environmental safety. A reliable emission forecasting model can provide important information for optimizing the process and improving the environmental performance. In this work, forecasting models are developed for the prediction of SO2 emission from a Sulfur Recovery Unit (SRU). Since SRUs incorporate complex chemical reactions, first-principle models are not suitable to predict emission levels based on a given feed condition. Accordingly, artificial intelligence-based models such as standard machine learning (ML) algorithms, multi-layer perceptron (MLP), long short-term memory (LSTM), one-dimensional convolution (1D-CNN), and CNN-LSTM models were tested, and their performance was evaluated. The input features and hyperparameters of the models were optimized to achieve maximum performance. The performance was evaluated in terms of mean squared error (MSE) and mean absolute percentage Error (MAPE) for 1 h, 3 h and 5 h ahead of forecasting. The reported results show that the CNN-LSTM encoder-decoder model outperforms other tested models, with its superiority becoming more pronounced as the forecasting horizon increased from 1 h to 5 h. For the 5-h ahead forecasting, the proposed model showed a MAPE advantage of 17.23%, 4.41%, and 2.83%, respectively over the 1D-CNN, Deep LSTM, and single-layer LSTM models in the larger dataset.

Endometriosis Grade 4 in In Vitro Fertilisation and Its Management: A Case Report.

Endometriosis is a condition in which tissue that lines the uterus grows outside the uterus. Patients with endometriosis often experience pelvic pain with menstrual periods and sometimes also infertility. Sometimes it is mistaken for pelvic inflammatory disease or ovarian cysts. This condition is a contraindication for pregnancy. This is a case report of a 37-year-old female who came to in vitro fertilisation (IVF) with a history of infertility of 14 years and was diagnosed with Grade 4 endometriosis on diagnostic ultrasonography-guided hysterolaparoscopy. After many trials of intrauterine insemination she was advised to go for IVF, and that not by obtaining her own ovum. The donor's egg and male partner's sperm were used for the IVF. The fertilised zygote was then implanted in the patient's uterus.

An ICP-MS study on metal content in biodiesel and bioglycerol produced from heated and unheated canola oils.

This study addresses the challenges of biodiesel production costs and waste oil disposal by investigating the use of low-cost waste oil as a feedstock. The impact of heating temperature on biodiesel yield and trace metal levels is examined using response surface methodology (RSM). Optimal conditions for high biodiesel yields (95-98%) from canola oil are determined with a methanol/oil ratio of 12:1, 1 wt% catalyst, and 60-min reaction time. For crude bioglycerol, the optimal conditions involve a methanol/oil ratio of 4.25:1, 2.93 wt% catalyst, and 119.15-min reaction time. Elemental analysis reveals the presence of high-concentration metals like Cu and Zn and low-concentration ones such as Pb, As, Se, and Zr in both oil feedstocks and their respective biodiesel and bioglycerol products. The study demonstrates that thermal stress on canola oil significantly impacts biodiesel and bioglycerol yields and trace metal levels during the transesterification process. The findings contribute to enhancing cost-effectiveness and environmental sustainability in biodiesel production.

Synthesis of Mesoporous Carbon Adsorbents Using Biowaste Crude Glycerol as a Carbon Source via a Hard Template Method for Efficient CO2 Capture.

Biowaste utilization as a carbon source and its transformation into porous carbons have been of great interest to promote environmental remediation owing to biowaste's cost-effectiveness and useful physicochemical properties. In this work, crude glycerol (CG) residue from waste cooking oil transesterification was employed to fabricate mesoporous crude glycerol-based porous carbons (mCGPCs) using mesoporous silica (KIT-6) as a template. The obtained mCGPCs were characterized and compared to commercial activated carbon (AC) and CMK-8, a carbon material prepared using sucrose. The study aimed to evaluate the potential of mCGPC as a CO2 adsorbent and demonstrated its superior adsorption capacity compared to AC and comparable to CMK-8. The X-ray diffraction (XRD) and Raman results clearly depicted the structure of carbon nature with (002) and (100) planes and defect (D) and graphitic (G) bands, respectively. The specific surface area, pore volume, and pore diameter values confirmed the mesoporosity of mCGPC materials. The transmission electron microscopy (TEM) images also clearly revealed the porous nature with the ordered mesopore structure. The mCGPCs, CMK-8, and AC materials were used as CO2 adsorbents under optimized conditions. The mCGPC adsorption capacity (1.045 mmol/g) is superior to that of AC (0.689 mmol/g) and still comparable to that of CMK-8 (1.8 mmol/g). The thermodynamic analyses of the adsorption phenomena are also carried out. This work demonstrates the successful synthesis of a mesoporous carbon material using a biowaste (CG) and its application as a CO2 adsorbent.

A Reaction Kinetics Study on Benzene Oxidation in the Claus Process by Sulfur Monoxide.

The Claus process is used in natural gas processing plants to treat H2S-rich acid gas to recover sulfur, but the process suffers from catalytic deactivation when aromatic contaminants such as benzene, toluene, ethylbenzene, and xylene isomers (collectively called as BTEX) are present in the acid gas feed. To safeguard the catalytic reactors, it is desired to oxidize aromatic contaminants in the furnace that are present upstream of the catalytic reactors in the process by oxidants present in it. This work develops a reaction mechanism and evaluates the reaction kinetics for the oxidation of phenyl radical by SO using CBS-QBS for reaction energetics and RRKM and transition state theory for reaction kinetics. The mechanism explores the possible products that are formed from the barrierless addition of SO on phenyl through the O atom as well as through the S atom. The exothermicity of the addition reaction is higher when the addition of SO on the aromatic structure takes place through the S atom. The major products formed from phenyl oxidation by SO are cyclopentadienyl, cyclopentadienethiol and thiopyran radicals. A remarkable similarity between the pathways for phenyl radical oxidation by O2 and its oxidation by SO at high temperatures is observed. The proposed reactions and their rate constants are used to conduct reactor simulations to determine the important reactions that contribute to the formation of major products during phenyl-SO reactions and the temperatures suitable for benzene oxidation by SO under process conditions similar to the Claus furnace.

Carbon dioxide adsorbents from flame-made diesel soot nanoparticles.

Carbon dioxide (CO2) is the top contributor to global warming. On the other, soot particles formed during fuel combustion and released into the atmosphere are harmful and also contribute to global warming. It would therefore be highly advantageous to capture soot and make use of it as a feedstock to synthesize carbon-based materials for applications such as carbon dioxide adsorption. In this work, flame-made diesel soot nanoparticles were used to produce a variety of activated carbons by combined oxidative treatment with hydrogen peroxide (H2O2) and potassium hydroxide (KOH), and their performance towards CO2 adsorption was evaluated. The effect of the chemical activation of soot with H2O2 for different reaction times and with KOH on the physicochemical properties of the activated carbons was investigated and compared to fresh soot. Interestingly, hollow aggregates of carbonaceous nanoparticles of a high interplanar distance, reduced polycyclic aromatic hydrocarbons (PAH) size, shorter PAH stacks, mesoporous structure, and a high content of oxygen functionalities along with other structural defects in PAHs were obtained in the synthesized activated carbons. Among the various analysis techniques employed, Raman spectroscopy indicated that the ID/IG ratio in soot decreased after simultaneous chemical treatment, though it did not indicate any enhancement in the graphitic character since the carbonyl and carboxylic containing PAHs and monovacancies (which cause defects in PAHs) also contribute to the increase in the intensity of the graphitic band. The activated carbons possessed promising CO2 adsorption capacities, adsorption kinetics and CO2/N2 selectivity. For example, one of the activated carbons, following H2O2 treatment for 9 h and a subsequent KOH activation, exhibited a CO2 adsorption capacity of 1.78 mmol/g at 1 bar and 25 °C, representing an increase of 161 % in capacity as compared to fresh soot. Hollow aggregates of carbonaceous nanoparticles consisting of shorter PAHs with a larger number of defects led to enhanced CO2 adsorption rate and CO2/N2 selectivity on activated carbons.

Super porous TiO2 photocatalyst: Tailoring the agglomerate porosity into robust structural mesoporosity with enhanced surface area for efficient remediation of azo dye polluted waste water.

The low surface area of TiO2 (50 m2g-1 - Degussa P25) due to randomly oriented, agglomerated nanostructures and charge carrier recombination tendency, has till date been its major limitation for photocatalytic remediation of polluted wastewater. This study presents an innovative process to design super porous TiO2 nanostructures with high effective surface area (238 m2g-1), robust, structurally ordered mesoporosity via a simple sol-gel assisted reflux method. Detailed material characterization studies suggest that the higher degree of intermolecular ligation in novel templates such as butanetetracarboxylic or tricarballylic acid modified titanium hydroxide gels resulted in retainment of the porous structure during the urea assisted combustion synthesis. The induction of robust structural porosity is accompanied by a reduction in pore size distribution, an increase in pore volume leading to significantly higher total surface area of the synthesized TiO2. Detailed investigation of dye adsorption kinetics and photocatalytic degradation kinetics, complemented by kinetic modeling analysis confirmed that the super porous TiO2 with robust mesoporous structure outperforms the rest of synthesized TiO2 catalyst (having only agglomerate porosity) in terms of its superior adsorption capacity, faster diffusion kinetics and photocatalytic activity for degradation of Amaranth dye. Thus, the super porous TiO2 shows promising potential for application in sustainable photocatalytic technology for remediation of wastewater contaminated with azo dyes.

On the role of resonantly stabilized radicals in polycyclic aromatic hydrocarbon (PAH) formation: pyrene and fluoranthene formation from benzyl-indenyl addition.

Resonantly stabilized radicals, such as propargyl, cyclopentadienyl, benzyl, and indenyl, play a vital role in the formation and growth of polycyclic aromatic hydrocarbons (PAHs) that are soot precursors in engines and flames. Pyrene is considered to be an important PAH, as it is thought to nucleate soot particles, but its formation pathways are not well known. This paper presents a reaction mechanism for the formation of four-ring aromatics, pyrene and fluoranthene, through the combination of benzyl and indenyl radicals. The intermediate species and transition structures involved in the elementary reactions of the mechanism were studied using density functional theory, and the reaction kinetics were evaluated using transition state theory. The barrierless addition of benzyl and indenyl to form the adduct, 1-benzyl-1H-indene, was found to be exothermic with a reaction energy of 204.2 kJ mol-1. The decomposition of this adduct through H-abstraction and H2-loss was studied to determine the possible products. The rate-of-production analysis was conducted to determine the most favourable reactions for pyrene and fluoranthene formation. The premixed laminar flames of toluene, ethylbenzene, and benzene were simulated using a well-validated hydrocarbon fuel mechanism with detailed PAH chemistry after adding the proposed reactions to it. The computed and experimentally observed species profiles were compared to determine the effect of the new reactions for pyrene and fluoranthene formation on their concentration profiles. The role of benzyl and indenyl combination in PAH formation and growth is highlighted.

Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study.

The role of resonantly stabilized radicals such as propargyl, cyclopentadienyl and benzyl in the formation of aromatic hydrocarbons such as benzene and naphthalene in the high temperature environments has been long known. In this work, the possibility of benzyl recombination to form three-ring aromatics, phenanthrene and anthracene, is explored. A reaction mechanism for it is developed, where reaction energetics are calculated using density functional theory (B3LYP functional with 6-311++G(d,p) basis set) and CBS-QB3, while temperature-dependent reaction kinetics are evaluated using transition state theory. The mechanism begins with barrierless formation of bibenzyl from two benzyl radicals with the release of 283.2 kJ mol(-1) of reaction energy. The further reactions involve H-abstraction by a H atom, H-desorption, H-migration, and ring closure to gain aromaticity. Through mechanism and rate of production analyses, the important reactions leading to phenanthrene and anthracene formation are determined. Phenanthrene is found to be the major product at high temperatures. Premixed laminar flame simulations are carried out by including the proposed reactions for phenanthrene formation from benzyl radicals and compared to experimentally observed species profiles to understand their effects on species concentrations.

Reaction Mechanism for m-Xylene Oxidation in the Claus Process by Sulfur Dioxide.

In the Claus process, the presence of aromatic contaminants such benzene, toluene, and xylenes (BTX), in the H2S feed stream has a detrimental effect on catalytic reactors, where BTX form soot particles and clog and deactivate the catalysts. Among BTX, xylenes are proven to be most damaging contaminant for catalysts. BTX oxidation in the Claus furnace, before they enter catalyst beds, provides a solution to this problem. A reaction kinetics study on m-xylene oxidation by SO2, an oxidant present in Claus furnace, is presented. The density functional theory is used to study the formation of m-xylene radicals (3-methylbenzyl, 2,6-dimethylphenyl, 2,4-dimethylphenyl, and 3,5-dimethylphenyl) through H-abstraction and their oxidation by SO2. The mechanism begins with SO2 addition on the radicals through an O-atom rather than the S-atom with the release of 180.0-183.1 kJ/mol of reaction energies. This exothermic reaction involves energy barriers in the range 3.9-5.2 kJ/mol for several m-xylene radicals. Thereafter, O-S bond scission takes place to release SO, and the O-atom remaining on aromatics leads to CO formation. Among four m-xylene radicals, the resonantly stabilized 3-methylbenzyl exhibited the lowest SO2 addition and SO elimination rates. The reaction rate constants are provided to facilitate Claus process simulations to find conditions suitable for BTX oxidation.

PAH growth initiated by propargyl addition: mechanism development and computational kinetics.

Polycyclic aromatic hydrocarbon (PAH) growth is known to be the principal pathway to soot formation during fuel combustion, as such, a physical understanding of the PAH growth mechanism is needed to effectively assess, predict, and control soot formation in flames. Although the hydrogen abstraction C2H2 addition (HACA) mechanism is believed to be the main contributor to PAH growth, it has been shown to under-predict some of the experimental data on PAHs and soot concentrations in flames. This article presents a submechanism of PAH growth that is initiated by propargyl (C3H3) addition onto naphthalene (A2) and the naphthyl radical. C3H3 has been chosen since it is known to be a precursor of benzene in combustion and has appreciable concentrations in flames. This mechanism has been developed up to the formation of pyrene (A4), and the temperature-dependent kinetics of each elementary reaction has been determined using density functional theory (DFT) computations at the B3LYP/6-311++G(d,p) level of theory and transition state theory (TST). H-abstraction, H-addition, H-migration, ß-scission, and intramolecular addition reactions have been taken into account. The energy barriers of the two main pathways (H-abstraction and H-addition) were found to be relatively small if not negative, whereas the energy barriers of the other pathways were in the range of (6-89 kcal·mol(-1)). The rates reported in this study may be extrapolated to larger PAH molecules that have a zigzag site similar to that in naphthalene, and the mechanism presented herein may be used as a complement to the HACA mechanism to improve prediction of PAH and soot formation.

Affinity purification of viral protein having heterogeneous quaternary structure: modeling the impact of soluble aggregates on chromatographic performance.

Prokaryote-expressed polyomavirus structural protein VP1 with an N-terminal glutathione-S-transferase tag (GST-VP1) self-assembles into pentamer structures that further organize into soluble aggregates of variable size (3.4 x 10(2)-1.8 x 10(4)kDa) [D.I. Lipin, L.H.L. Lua, A.P.J. Middelberg, J. Chromatogr. A 1190 (2008) 204]. The adsorption mechanism for the full range of GST-VP1 soluble aggregates was described assuming a dual-component model [T.Y. Gu, G.J. Tsai, G.T. Tsao, AICHE J. 37 (1991) 1333], with components differentiated by size, and hence pore accessibility, rather than by protein identity. GST-VP1 protein was separated into two component groups: aggregates small enough to access resin pores (LMW: 3.4 x 10(2)-1.4 x 10(3)kDa) and aggregates excluded from the resin pores (HMW: 9.0 x 10(2)-1.8 x 10(4)kDa). LMW aggregates bound to resin at a higher saturation concentration (29.7 g L(-1)) than HMW aggregates (13.3 g L(-1)), while the rate of adsorption of HMW aggregates was an order of magnitude higher than for LMW aggregates. The model was used to predict both batch and packed bed adsorption of GST-VP1 protein in solutions with known concentrations of HMW and LMW aggregates to Glutathione Sepharose HP resin. Asymmetrical flow field flow fractionation with UV absorbance was utilized in conjunction with adsorption experimentation to show that binding of HMW aggregates to the resin was strong enough to withstand model-predicted displacement by LMW aggregates. High pore concentrations of LMW aggregates were also found to significantly inhibit the diffusion rate of further protein in the resin pores. Additional downstream processing experimentation showed that enzymatic cleavage of LMW aggregates to remove GST tags yields more un-aggregated VP1 pentamers than enzymatic cleavage of HMW aggregates. This model can be used to enhance the chromatographic capture of GST-VP1, and suggests an approach for modeling chromatographic purification of proteins that have a range of quaternary structures, including soluble aggregates.