Reactor Feed Research Articles

Polyacrylic acid-coated iron oxide magnetic nanoparticles: The polymer molecular weight influence

Magnetic nanoparticles (MNPs), in particular, magnetic iron oxide-based nanoparticles were found to be useful as catalysts and as devices for data storage, environmental remediation and several biomedical applications, due to their excellent properties, such as biocompatibility and high magnetic moment. Polyacrylic acid (PAA) is a weak polyelectrolyte that can be used to stabilize the MNPs. To the best of our knowledge, the influence of PAA molecular weight and PAA concentration over the magnetic and structural properties of iron oxide nanoparticles has not been previously reported. The aim of this paper is to describe the differences evidenced in the properties of different magnetic materials by using PAA for iron oxides stabilization by one-pot coprecipitation synthesis. Iron oxide-based magnetic nanoparticles stabilized by polyacrylic acid (PAA) polymers were efficiently prepared and exhaustively characterized. The influence on the employment of two different low PAA molecular weights, Mw 1800 g/mol and 5000 g/mol, in three different iron salts: PAA ratios was analyzed. In summary, the main results showed that: for a certain PAA reactor feed higher oligomer quantities are present in MNPs as higher is the involved molecular weight of the polymeric chain; when molecular weight raises the contribution of loops and tails also does it, allowing having higher polymer contents. For both PAA’s Mw employed as the adsorbed PAA increases particles hydrodynamic diameters decreases, and their distribution becomes narrower; the PAA adsorbs onto iron oxides by chemisorption (the most probable interaction is the bidentate bridging). For the studied cases z potential values depend much more on the PAA’s quantity adsorbed onto the iron oxides than on the PAA’s Mw. MNPs are superparamagnetic and choosing the right shape of particle distribution is not central for getting estimates of the magnetization saturation, the average particle diameter and its standard deviation, while better fits are found with Normal and Log-Normal particle size distributions.

Real-Time Raman Monitoring of Calcium Phosphate Precipitation in a Semi-Batch Stirred Crystallizer

Semi-batch precipitation of calcium monohydrogen phosphate dihydrate (CaHPO4·2H2O; also termed dicalcium phosphate dihydrate, DCPD) from a homogeneous reaction of KH2PO4 and CaCl2 was studied with inline Raman spectroscopy. In the reaction, hydroxyapatite (HAP, Ca5OH(PO4)3) formed first and transferred to DCPD throughout the entire precipitation process. Raman calibration models were created with a series of KH2PO4‒NaOH‒water solutions. The reliability of the calibration models was validated with offline measurement of phosphate concentration in the mother liquor. Real-time changes in HPO42– and H2PO4– concentration were monitored and predicted. Comprehensive kinetic information was obtained from liquid and solid analysis. It was found that the influence of the mixing rate on the precipitation was not significant, whereas the reactant feeding rate had a remarkable impact.

Feed rate noise modulates autocatalysis and shapes the oscillations of the Belousov–Zhabotinsky reaction in a continuous stirred tank reactor

Noise applied to a specific reactant feed rate directs the Belousov–Zhabotinsky reaction into specific pathways and results in noise-controlled oscillation shapes and features.

Adaptive optimal operation of a parallel robotic liquid handling station

Results are presented from the optimal operation of a fully automated robotic liquid handling station where parallel experiments are performed for calibrating a kinetic fermentation model. To increase the robustness against uncertainties and/or wrong assumptions about the parameter values, an iterative calibration and experiment design approach is adopted. Its implementation yields a stepwise reduction of parameter uncertainties together with an adaptive redesign of reactor feeding strategies whenever new measurement information is available. The case study considers the adaptive optimal design of 4 parallel fed-batch strategies implemented in 8 mini-bioreactors. Details are given on the size and complexity of the problem and the challenges related to calibration of over-parameterized models and scarce and non-informative measurement data. It is shown how methods for parameter identifiability analysis and numerical regularization can be used for monitoring the progress of the experimental campaigns in terms of generated information regarding parameters and selection of the best fitting parameter subset.

Effect of feed composition of co-pyrolysis of corncobs–polypropylene plastic on mass interaction between biomass particles and plastics

Polypropylene plastic (PP), which has higher hydrogen content compared to that in biomass, is potential to be used as a cheap hydrogen source for pyrolysis of biomass, such as corncobs, to remove part of oxygen content in the biomass pyrolysis oil. By charging these two materials, synergistic effects will appear that improve quality and quantity of bio-oil produced. The aim of the present work is to investigate possible mass interaction between biomass and plastic materials leading to the synergistic effects using slow co-pyrolysis. The experiment was performed in a displacement reactor. Feed composition was varied at 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, and 87.5% weight of PP. This phenomenon was observed through expansion-contraction of the reactor prior to large mass decomposition of the reactor feed. In experiment involving biomass-dominated feeds, i.e. PP contents < 50% (regime 1), there was reactor bed contraction due to slight biomass decomposition followed by no-displacement of reactor piston. During the contraction, it is estimated, there was low velocity ejection of biomass volatile matter, while during no-displacement stage, there was a phase change of plastic granules to plastic melt. In experiment with plastic-dominated feeds, i.e. PP ≥ 50% (regime 2), the reactor bed underwent contraction due to phase change of plastic granules which reduced the bed volume, followed by bed expansion due to the swelling of biomass particles estimated in the presence of hydrogen bonding in the phenolic environment in biomass material. The last stage of co-pyrolysis in regime 2 was the bed contraction and it is predicted that there was high velocity gas ejection through the small pores which intensified interaction of biomass-plastic radicals in hydrogen-rich environment favourable for exerting synergistic effect.

SYNTHESIS OF 1,5-DIPHENYL-3-ARYLVERDAZILS

The reaction between verdazyls and CH-acids was studied for checking common views on the stable radicals reactivity which is usually associated with the spin density values of the reaction centers and its alterations due to the influence of substituents. The synthesis of row l,5-diphenyl-3-arylverdazyls that contains the different types of substituents in the phenyl rings that are situated at C3 verdazyl radical atom was carried out for this purpose. This also includes the previously non-described 1,5-diphenyl-3-(4-hydroxyl)phenyl-, 1,5-diphenyl-3-(4-bromo)phenyl-, 1,5-diphenyl-3-(3- nitro)phenylverdazyls. In this case, the availability and nature of the substituents in the phenyl rings at C3 verdazyl radical atom may not be affected by the change in the spin density values on the N2 and N4 nitrogen atoms that are verdazyl radicals’ reaction centers. The synthesis of verzdazyls was carried out according to the conventional scheme, on the basis of arylhydrazones. It was observed that during azocoupling reacting of phenyldiazonium chloride with arylhydrazones in the synthesis of formazans the reaction proceeds with a higher yield when the solvent dimethylformamide-pyridine is being used. Transformation of formazans into verdazyl radicals was being carried out at room temperature with formaldehyde exposured to formazan in the presence of potassium hydrogen sulfate under the constant air going through the reactor feed. The availability of substituents in the phenyl ring at C3 formazan atom was increasing reaction time significantly in comparison with 1,3,5- trifenylformazan regardless of the substituent’s nature at C3 formazan atom. During the reaction between 1,5-diphenyl-3-arilverdazyls and CH-acids (acetylacetone and dimedone), it was discovered that the reaction rate depends on both the acidity of the CH-acid (dimedone reacts faster than acetylacetone) and the nature of the substituents situated in phenyl ring at C3 verdazyl atom. At the same time, the electron-donating substituents increase the rate of reaction between verdazyls and CH-acids while electron-donor substituents decrease it. Therefore, as it was formerly reported, when we deal with monochloroacetic acid, the rate of a reaction between verdazyl radicals and CH-acids is increasing in front of the electron-donor substituents and decreasing in front of electron-acceptor substituents. These regularities are not connected with the spin density values of the verdazyls’ reaction centers.Forcitation:Tsebulayeva Yu.V., Pryanichnikova M.K., Tanaseichuk B.S. Synthesis of 1,5-diphenyl-3-arylverdazils. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 23-29

Chromium isotope fractionation during Cr(VI) reduction in a methane-based hollow-fiber membrane biofilm reactor

Chromium (Cr) isotope fractionation analysis is a promising tool for monitoring Cr(VI) reduction in natural aqueous systems. In addition, large amounts of CH4 in natural aqueous sediments are oxidized to CO2 through methanotrophs, thereby mitigating emissions to the atmosphere. However, the investigations on the Cr(VI) reduction process with methanotrophs, and the associated Cr isotope fractionation patterns are scarce. In this study, we have shown that Cr(VI) reduction can occur in the presence of CH4 as the sole electron donor in a hollow-fiber membrane reactor (HfMBR) after direct bacteria enrichment from sediment samples. Products of the methane oxidation by the methanotrophs are used by microbes to reduce Cr(VI) as shown by the progressive increase in δ53Cr with time in the CH4 feed reactor. The isotope fractionation factor (ε) of −2.62 ± 0.20‰ was obtained from the application of the Rayleigh distillation model. The results of Cr isotope fractionation analysis also explained the decrease of Cr(VI) concentration in the N2 feed reactor, where the δ53Cr values remained steady in the first two weeks but significantly increased in the last two weeks, indicating that physical adsorption and subsequent Cr(VI) reduction occurred. This study extended the application of Cr isotope fractionation, showing the suitability of this method for clarifying different Cr(VI) removal processes.

Optimization of Bioethanol In Silico Production Process in a Fed-Batch Bioreactor Using Non-Linear Model Predictive Control and Evolutionary Computation Techniques

Due to growing worldwide energy demand, the search for diversification of the energy matrix stands out as an important research topic. Bioethanol represents a notable alternative of renewable and environmental-friendly energy sources extracted from biomass, the bioenergy. Thus, the assurance of optimal growth conditions in the fermenter through operational variables manipulation is cardinal for the maximization of the ethanol production process yield. The current work focuses in the determination of optimal control scheme for the fermenter feed rate and batch end-time, evaluating different parametrization profiles, and comparing evolutionary computation techniques, the genetic algorithm (GA) and differential evolution (DE), using a dynamic real-time optimization (DRTO) approach for the in silico ethanol production optimization. The DRTO was able to optimize the reactor feed rate considering disturbances in the process input. Open-loop tests results obtained for the algorithms were superior to several works presented in the literature. The results indicate that the interaction between the intervals of DRTO cycles and parametrization profile is more significant for the GA, both in terms of ethanol productivity and batch time. In general lines, the present work presents a methodology for control and optimization studies applicable to other bioenergy generation systems.

Assessment of the platinum deposition behaviour on stainless steel surfaces in a boiling water reactor plant

ABSTRACTWith the aim of mitigating stress corrosion cracking (SCC) in reactor internals and recirculation pipes, the boiling water reactor plant Leibstadt (KKL) changed in 2008 from normal water chemistry to hydrogen water chemistry in combination with online noble metal chemical addition (OLNC). For this purpose, a Na2Pt(OH)6 solution is injected into the reactor feed water, where platinum (Pt) particles are formed and deposited on water-wetted surfaces. If a stoichiometric excess of hydrogen and a uniform surface coverage with extremely fine Pt particles exist simultaneously at critical locations, a low electrochemical corrosion potential, and therefore a low SCC susceptibility can be expected. To study the Pt deposition behaviour and to assess the effectiveness of the OLNC technology under real plant conditions, stainless steel coupon specimens were exposed to the reactor water for different durations at two locations in KKL. The specimens were then analysed at PSI for their Pt surface loading. In addition, a replica technique and transmission electron microscopy were used to determine the Pt particle size and distribution on the active specimens. The investigations indicated that the pre- and post-OLNC exposure times play an important role for the Pt deposition and retention on specimens and that a remobilisation of Pt in the plant takes place. Unfortunately, most of the released Pt does not redeposit on other steel surfaces in the reactor system. The flow velocity of the Pt containing reactor water across the specimens also has an impact on the Pt surface loading. The average Pt particle size is in the expected range, but the distribution of the Pt particles on plant specimens seems to be rather erratic.

Comparative study of activated sludge with different individual nitrogen sources at a low temperature: Effluent dissolved organic nitrogen compositions, metagenomic and microbial community

The objective of this study was to explore nitrogen removal, especially effluent dissolved organic nitrogen (DON) composition, relative genes and microbial community structures with four individual nitrogen sources at 5°C. Results show that effluent DON did not have dependent relationship with the TN removal rate (urea>ammonia chloride>L-Alanine>D-Alanine). With the same influent TN, the highest effluent DON was formed with urea; the lowest DON was fed with ammonia chloride. The main DON composition was the product of cell metabolism excluding urea, rather than the original substrate. Glutamic acid synthesizing process was of great importance to DON accumulation at 5°C. The nitrogen source type was important to the diversity and heterogeneity of the nitrogen removal genes. Bacterial population structure using redundancy analysis (RDA) showed Simplicispira occupied a higher abundance remarkably in the reactors feeding with urea, and Dyadobacter occupied higher feeding with l-Alanine.

Flow of Tunable Elastic Microcapsules through Constrictions

We design and fabricate elastically tunable monodisperse microcapsules using microfluidics and cross-linkable polydimethylsiloxane (PDMS). The overall stiffness of the microcapsules is governed by both the thickness and cross-link ratio of the polymer shell. Flowing suspensions of microcapsules through constricted spaces leads to transient blockage of fluid flow, thus altering the flow behavior. The ability to tune microcapsule mechanical properties enables the design of elastic microcapsules that can be tailored for desired flow behavior in a broad range of applications such as oil recovery, reactor feeding, red blood cell flow and chemical targeted delivery.

PROX reaction of CO in H2/H2O/CO2 Water–Gas Shift (WGS) feedstocks over Cu–Mn/Al2O3 and Cu–Ni/Al2O3 catalysts for fuel cell applications

Abstract Catalytic conversion performance of the γ-Al2O3-supported Cu-, Mn- and Ni-based materials for the selective preferential oxidation of CO was investigated. The influence of CO2 and H2O in the reactor feed gas on activity and selectivity was lastly investigated for copper bimetallic catalysts containing manganese and nickel. Cu/Al2O3 proved to be optimal among the monometallic examined. It was observed that even in the absence of H2, CO was effectively converted. Upon H2 presence, a fraction of oxygen is utilized for the latter, which results in the decrease of CO turnover. Cu–Mn/Al2O3 surpassed other single and mixed metal oxide catalysts which could be due to a combination of surface desorption capacity and redox properties. The oxygen storage capacities (OSC) were in the order of Cu–Mn/Al2O3 > Cu–Ni/Al2O3 > Cu/Al2O3 > Mn/Al2O3 > Ni/Al2O3, in an agreement with reactivity. The efficiency at low process temperatures was enhanced by adding H2O vapors, nonetheless, decreased at high-end range due to the reverse water–gas shift (RWGS). Also, the rate of CO conversion was high utilizing Cu–Mn/Al2O3; furthermore, even upon applying H2O and CO2. CO2 notably affected CO conversion, and ultimately, decreased the activity, which, conversely, remained stable upon time-on-stream.

Structurally tuning microwave absorption of core/shell structured CNT/polyaniline catalysts for energy efficient saccharide-HMF conversion

Microwave absorption and catalytic activity have been synergistically integrated into a core/shell structured CNT/polyaniline (PANI) hybrid catalyst that enables localized heating on the catalyst surface and uplifts energy efficiency in the dehydration reaction of saccharides to 5-hydroxymethylfurfural (HMF). Results reveal that the integration of CNT and polyaniline significantly improves the overall saccharide conversion and HMF yield. The PANI shell thickness and morphology are controlled by both reactant feeding ratio and polymerization reaction rate. A thinner and rougher PANI shell is favourable to enhance the overall microwave absorption, improve heat transfer efficiency to catalyst surface and thus reaction efficiency. The highest energy efficiency of 7.6mmolkJ−1L−1 is reached in 10min with CNT/PANI catalyst (30wt% CNTs) and 19W input power. Moreover, the packing of polyaniline shell on CNT core facilitates its separation from reaction mixture and effectively prevents catalyst loss. These catalysts show excellent recyclability that the catalyst activity can be completely recovered by a simple re-doping process in 1.0M sulfuric acid. This work opens up a new window in microwave responsive catalyst design that enhances energy efficiency in saccharide-HMF conversion reactions and promotes the economic feasibility of such reactions in practice.

Integrated Carbon Capture and Conversion To Produce Syngas: Novel Process Design, Intensification, and Optimization

An integrated, modular, and multifunctional process is conceptually designed, simulated, and optimized for direct utilization of CO2 from dilute flue gas to produce high-quality syngas, a precursor for many value-added chemicals and liquid transportation fuels. The process is intensified to simultaneously capture and convert CO2 using methane, natural gas, or excess fuel gas from the same plant, or using nearby unconventional methane from biogas or landfill gas. It is an integrated adsorption-purge-reaction system where CO2 is first adsorbed and then desorbed using methane-rich feed leading to a mixture suitable for dry-reforming. The merging of concentration-based CO2 desorption with the reactor feed premixing step eliminates the need for pressure or temperature swings and significantly reduces the energy penalty and cost of CO2 capture and utilization. The process is simulated at different conditions using a high-fidelity process model to elucidate the effects of key decision variables as well as the tr...

High Purity Hydrogen with Sorption-Enhanced Steam Methane Reforming in a Gas–Solid Trickle Bed Reactor

A sorption enhanced-steam methane reforming (SE-SMR) process was investigated in a countercurrent gas–solid trickle flow reactor packed with regularly stacked catalyst. The stacked catalyst was made of corrugated Pt/Ni/Al2O3 plates in the form of static mixers. Experiments were carried out in a temperature range of 550–600 °C, total pressure of 4.0 bar, and water to methane ratio of 4.0 in the reactor feed. Within the investigated conditions, experimental results offered a solid proof of concept for new continuous SE-SMR operation for production of hydrogen where sorbent can be regenerated separately from the catalyst. Experimental data were reasonably well described by a plug flow model for both the gas and solid phases. The mathematical model was further used to optimize the continuous SE-SMR operation: it could be demonstrated that the level of the hydrogen purity in the reactor exit stream could be controlled by a multistage reactor consisting of alternating catalytic active and stainless-steel inert ...

Optimization of the control loops of the variable frequency induction motor drive of the flame reactor feed screw

In the paper the optimization of the control loops of the variable frequency induction motor drive for the feed screw of a flame reactor has been carried out to obtain required dynamic characteristics of the electric drive for known parameters of the plant. Simulation studies of basic control loops

Simultaneous synthesis of non-isothermal water networks integrated with process streams

This paper is an extension of our previous study [1] and addresses simultaneous synthesis of non-isothermal water networks heat-integrated with hot and cold process streams. Hence, the scope of heat integration is expanded by enabling heat integration of process streams such as waste gas streams and reactor feed and effluent streams simultaneously with the water network's hot and cold streams. A recently proposed superstructure [2] for the synthesis of non-isothermal water networks is extended in order to enable additional heat integration options with process streams. The model and solution strategy are modified in order to enable achieving the solution of the problem within the reasonable computational time. Pseudo heat exchanger cost was introduced in order to find heat exchange matches. They are used as constraints within the mixed-integer nonlinear programming (MINLP) model that simultaneously addresses the synthesis problem. The objective function of the proposed model accounts for operating costs, including fresh water, utilities and treatment operating cost, and investment costs of heat exchangers and treatment units. The results indicate that by solving a unified network, rather than stand-alone non-isothermal water network and separate process heat exchange network, additional savings in utilities consumption and total annualised cost can be achieved.

Optimization and control of a reactive distillation process for the synthesis of dimethyl carbonate

Abstract Dimethyl carbonate is an environmentally benign and biodegradable chemical. Based on integration of reactive distillation and pressure-swing distillation technologies, a novel process for synthesis of dimethyl carbonate through transesterification with propylene carbonate and methanol has been developed by Huang et al. In this work, the optimization of this process was performed by minimizing the total TAC. The results show that the optimal design flowsheet can save energy consumption by 18.6% with the propylene carbonate conversion of 99.9%. Then, an effective plant-wide control structure for the process was developed. Dynamic simulation results demonstrate that the temperature/flow rate cascade control plus with simple temperature control can keep not only product purity but also the conversion of the reactant at their desired values in the face of the disturbance in reactant feed flow rate and feed composition.

Autothermal oxidative coupling of methane with ambient feed temperature

We report the exploitation of thermal effects and bifurcation (ignition and extinction) behavior to enable steady-state operation of an Oxidative Coupling of Methane (OCM) reactor with ambient feed and furnace temperature. Using a simplified kinetic and reactor model and results from bifurcation theory, we explain the experimentally observed ignition-extinction behavior for catalysts of different activity and reactor tubes of varying diameter when the furnace temperature or the space time are varied. We apply the theory to analyze the impact of reactor tube diameter and heat loss on the feasible region of autothermal operation and present experimental evidence for the existence of isolated high temperature/conversion branches. The results indicate that when catalyst activity is high enough, it is possible to operate an OCM reactor autothermally using the reactor feed (at ambient temperature or lower) as coolant, which enables the maximum practical single-pass methane conversion.

Dynamics and Control of Reactive Distillation Columns with Double Reactive Sections: Feed-Splitting Influences

Reactive distillation columns with double reactive sections (RDCs-DRS) at the top and bottom are especially favorable for the separations of reacting mixtures featuring the most unfavorable ranking of relative volatilities. In this article, their dynamics and control are studied in great detail, with special attention given to the influences of feed splitting on process dynamics and controllability. Because of the totally refluxed and totally reboiled operation mode plus an intermediate-product withdrawal, the RDC-DRS is generally characterized by severe under-dampness between the intermediate-product compositions and the reboiler heat duty (i.e., the regulation path) and by severe asymmetry between the intermediate-product compositions and the heaviest reactant feed flow rate (i.e., the disturbance path), consequently posing a great challenge to tight product quality control. With feed splitting of the lightest and heaviest reactants in the RDC-DRS (RDC-DRSFS), the simultaneous suppression of the under-d...