Reaction engineering

An innovative enzymatic polycondensation of dicarboxylic acids and dialcohols in aqueous polymerization media using free and immobilized lipases was developed. Various parameters (type of lipases, temperature, pH, stirring type and rate, and monomer carbon chain length) of the polycondensation in an oil-in-water (o/w) miniemulsion (>80% in water) were evaluated. The best results for polycondensation were achieved with an equimolar monomer concentration (0.5 M) of octanedioic acid and 1,8-octanediol in the miniemulsion and water, both at initial pH 5.0 with immobilized Pseudozyma antarctica lipase B (PBLI). The synthesized poly(octamethylene suberate) (POS) in the miniemulsion is characterized by a molecular weight of 7800 g mol−1 and a conversion of 98% at 45 °C after 48 h of polycondensation in batch operation mode. A comparative study of polycondensation using different operation modes (batch and fed-batch), stirring type, and biocatalyst reutilization in the miniemulsion, wate...

Chemical looping combustion is an attractive method for CO 2 capture in power plants, while maintaining high energy efficiency. The cyclic nature of the process, however, places significant demands on the redox and mechanical characteristics of the oxygen carrier. In this work, NiO/NiAl 2 O 4 and (NiO) 1-y (MgO) y /Ni (1-x) Mg x Al 2 O 4 were synthesized by solution combustion and investigated in two forms: porous extruded and dense pressed pellets. The pressed oxygen carriers of both compositions exhibited excellent stability during thermogravimetric analysis at temperatures 800-1200 • C with cycling of oxidizing/reducing gases while, due to sintering effects, the extruded pellets showed deteriorating performance. The addition of magnesium to the structure decreased reduction of the spinel, thus stabilizing the support. Attrition tests revealed superior performance of the (NiO) 0.21 (MgO) 0.79 /Ni 0.62 Mg 0.38 Al 2 O 4 , exceeding that of commercially available sintered iron oxide reference.

Driven by the increasing demand for novel lipophilic antioxidants for emulsions and oil-based formulas, a non-commercial immobilized Rhizopus oryzae lipase's capacity to catalyze butanol, octanol, and dodecanol esterification with piperic acid was optimized using Response Surface Methodology. The optimized conversion yield (92.21 ± 4.53%) for the synthesis of butyryl piperate was obtained by using 300 IU of immobilized lipase, with piperic acid/butanol substrate molar ratio of 1/8 in 3.6 mL of dichloromethane. The reaction was conducted at 30°C at 50 rpm for 48 h. Moreover, the two other esters (octyl-and dodecyl-piperate), which were synthesized using the same optimal conditions, appeared stable. The kinetic studies that the lowest K M app. (30 mM) and the highest V max (0.055 ± 0.003 µmol/h) were obtained for octyl-piperate synthesis showing that the immobilized lipase's affinity leaned more to octanol compared to the other fatty alcohols. FTIR results of the obtained esters show the band emerging at 1712 cm-1 , 1723 cm-1 , and 1753 cm-1 corresponding to the presence of the ester group bands of Butyryl piperate, Octyl piperate, and Dodecyl piperate, respectively. The esterification was also confirmed by the determination of the three esters' molecular masses using ICP-MS. Finally, the antioxidant ability of these newly created esters was approved, showing that the octyl-piperate presents the highest antioxidant activity. The novel lipophilic antioxidant compounds obtained by a green process could be potential candidates, especially in food-, cosmetic-and pharmaceutical-based emulsion preservation.

Dehydration reaction of ethanol was investigated in a temperature range of 140-250 • C with three different heteropolyacid catalysts, namely tungstophosphoricacid (TPA), silicotungsticacid (STA) and molybdophosphoricacid (MPA). Very high ethylene yields over 0.75 obtained at 250 • C with TPA was highly promising. At temperatures lower than 180 • C the main product was diethyl-ether. Presence of water vapor was shown to cause some decrease of catalyst activity. Results showing that product selectivities did not change much with the space time in the reactor indicated two parallel routes for the production of ethylene and DEE. Among the three HPA catalysts, the activity trend was obtained as STA > TPA > MPA.

Our understanding of gas-liquid–liquid reaction systems is not well developed today despite their widespread use in the process industries. Research work is demanded or inspired in those fields where basic information is either lacking or poorly organized. The field of mixing and agitation in gas-liquid-liquid reaction system is a typical example. Methyl ethyl ketazine formation is a typical case of homogeneous catalyzed gas-liquid-liquid reaction. The parametric study of ketazine formation has been carried out in a semi batch reactor. Agitation effect on methyl ethyl ketazine formation has been studied. Two types of agitators are used - flat paddle stirrer and vaned disk stirrer. The studies show that agitation plays an important role on the reaction. Yield of ketazine improved with degree of agitation, categorizing the reaction as moderately fast. Vaned disk stirrer is found to be more effective compared to flat paddle stirrer. Rate of reaction increases up to 600 rpm indicating d...

Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis ...

Cutinase has been shown to be a promising biocatalyst for applications in processes targeted for industrial scale. This work aims to further contribute for highlighting such role, by bestowing detailed insight on the application of cutinase for the synthesis of value added compounds in miniemulsion environments (oil-in-water). The synthesis of hexyl octanoate was used as model system, due to the relevance of this compound for industrial applications as flavor and fragrance agent. The nature, specificity and selectivity of the catalyst enable operation under mild reaction conditions, without undesirable side reactions, leading to a very pure product. A high conversion yield, about 86%, for an enzyme concentration of 5 mg ml -1 , was achieved. Hexyl octanoate synthesis and cutinase activity for different acid: alcohol molar ratio (R), under different pH environments, were evaluated. A maximum cutinase activity of 2.20 mol mg -1 min -1 was observed for R = 0.5, which was tentatively ascribed to the stabilizing effect of hexanol on the miniemulsion. It is thus considered that the accumulation of the hydrophobic hexyl octanoate inside the droplets stabilize the miniemulsion system.

Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis ...

An innovative enzymatic polycondensation of dicarboxylic acids and dialcohols in aqueous polymerization media using free and immobilized lipases was developed. Various parameters (type of lipases, temperature, pH, stirring type and rate, and monomer carbon chain length) of the polycondensation in an oil-in-water (o/w) miniemulsion (>80% in water) were evaluated. The best results for polycondensation were achieved with an equimolar monomer concentration (0.5 M) of octanedioic acid and 1,8-octanediol in the miniemulsion and water, both at initial pH 5.0 with immobilized Pseudozyma antarctica lipase B (PBLI). The synthesized poly(octamethylene suberate) (POS) in the miniemulsion is characterized by a molecular weight of 7800 g mol−1 and a conversion of 98% at 45 °C after 48 h of polycondensation in batch operation mode. A comparative study of polycondensation using different operation modes (batch and fed-batch), stirring type, and biocatalyst reutilization in the miniemulsion, wate...

Cutinase has been shown to be a promising biocatalyst for applications in processes targeted for industrial scale. This work aims to further contribute for highlighting such role, by bestowing detailed insight on the application of cutinase for the synthesis of value added compounds in miniemulsion environments (oil-in-water). The synthesis of hexyl octanoate was used as model system, due to the relevance of this compound for industrial applications as flavor and fragrance agent. The nature, specificity and selectivity of the catalyst enable operation under mild reaction conditions, without undesirable side reactions, leading to a very pure product. A high conversion yield, about 86%, for an enzyme concentration of 5 mg ml -1 , was achieved. Hexyl octanoate synthesis and cutinase activity for different acid: alcohol molar ratio (R), under different pH environments, were evaluated. A maximum cutinase activity of 2.20 mol mg -1 min -1 was observed for R = 0.5, which was tentatively ascribed to the stabilizing effect of hexanol on the miniemulsion. It is thus considered that the accumulation of the hydrophobic hexyl octanoate inside the droplets stabilize the miniemulsion system.

An adsorption process of water pollutants on a bed of activated carbon (AC) modified with metal oxide catalysts, was integrated in a single unit with periodic catalytic gas-phase regeneration at 240-290 OC. In the present contribution we report on the kinetics of the regeneration process: it exhibit an induction period and the rate passes through a maximum. Replotting the data scaled with respect to the maximal rate and the corresponding time shows that the curves overlap. In the process of regeneration the adsorbate moves from the carbon to the metal catalyst crystallites probably by surface diffusion. This process is modeled and compared with experimental observations. Solutions of suggested models with various kinetics are compared with experimental observation enabling to extract parameters like activation energies and rate constants.

Here, we report a new two-step enzymatic polymerization strategy for the synthesis of poly(octamethylene suberate) (POS) using an immobilized Pseudozyma antarctica lipase B (IMM-PBLI). The strategy overcomes the lack of enzymatic POS synthesis in solvent-free systems and increases the final polymer molecular weight. In the first step, the direct polycondensation of suberic acid and 1,8-octanediol was catalyzed by IMM-PBLI at 45 °C, leading to the production of prepolymers with molecular weights (MWs) of 2800, 3400, and 4900 g mol−1 after 8 h in miniemulsion, water, and an organic solvent (cyclohexane: tetrahydrofuran 5:1 v/v), respectively. In the second polymerization step, wet prepolymers were incubated at 60 or 80 °C, at atmospheric pressure, in the presence of IMM-PBLI, and without stirring. The final POS polymers showed a significant increase in MW to 5000, 5800, and 19,800 g mol−1 (previously synthesized in miniemulsion, water, or organic solvent, respectively). FTIR analysis ...

An innovative enzymatic polycondensation of dicarboxylic acids and dialcohols in aqueous polymerization media using free and immobilized lipases was developed. Various parameters (type of lipases, temperature, pH, stirring type and rate, and monomer carbon chain length) of the polycondensation in an oil-in-water (o/w) miniemulsion (>80% in water) were evaluated. The best results for polycondensation were achieved with an equimolar monomer concentration (0.5 M) of octanedioic acid and 1,8-octanediol in the miniemulsion and water, both at initial pH 5.0 with immobilized Pseudozyma antarctica lipase B (PBLI). The synthesized poly(octamethylene suberate) (POS) in the miniemulsion is characterized by a molecular weight of 7800 g mol−1 and a conversion of 98% at 45 °C after 48 h of polycondensation in batch operation mode. A comparative study of polycondensation using different operation modes (batch and fed-batch), stirring type, and biocatalyst reutilization in the miniemulsion, wate...

BACKGROUND: Oil-in-water miniemulsions have been suggested to display potential for application as a "green" system for enzymatic alkyl ester synthesis. Still, a realistic assessment of the feasibility of this approach for practical applications requires further insight, namely the relation between enzyme stability and reaction operational conditions. The objective of this work is within such scope. Accordingly, it extends previous research on esterification catalyzed by Fusarium solani pisi cutinase, by addressing medium-chain length substrates, and aims to contribute to the optimization of reaction conditions and towards the design of an efficient set-up. The esterification yield was significantly enhanced (e.g. 50% increase for octyl octanoate system) through the correction of the initial pH of the reaction medium to pH 6. Under such environment, conformational changes of the enzyme were negligible after 24 h, resulting in improved enzyme stability for all systems under study. Maximum esterification rate (3.59 mmolmin -1 ) and product yield (91%) were achieved for octyl decanoate synthesis. Fed-batch mode of operation allowed for the production of 1 M hexyl octanoate, while retaining enzyme activity over five days. Consecutive batch runs allowed for the cumulative production of 1.1 M hexyl octanoate after 4 cycles. Medium engineering allowed to use miniemulsion systems for the synthesis of medium-chain alkyl esters and to increase the final concentration of the intended product. Through a fed-batch mode the enzyme stability and reutilization was tuned allowing long-term utilization of the free enzyme which could not be achieved through a repeated batch system.

Plastic waste presents a persistent environmental challenge due to its non-biodegradable nature and global accumulation in ecosystems. Many plastics can take hundreds of years to decompose, resulting in their buildup in landfills, oceans, and ecosystems, which leads to harmful effects on wildlife and the environment. This includes the release of microplastics and toxic chemicals into the soil and water.
Chemical recycling offers a promising solution by breaking down plastics into their original chemical building blocks, enabling the production of high-quality products while reducing dependence on petroleum resources. This post delves into the history, technologies, economic and environmental benefits, and challenges of chemical recycling of plastic waste, with a focus on key processes like pyrolysis, gasification, and depolymerization.

The addition of static mixers within reactors leads to higher productivity of a process and an additional increase in mass and energy transfer. In this study, we developed millireactors with static mixers using stereolithography, an additive manufacturing technology. Computational fluid dynamics (CFD) simulations were conducted to study the flow, identify potential dead volumes, and optimize the design of the millireactors. We produced five millireactors with various static mixers and one tubular reactor without static mixers, which served as a reference. The Fenton reaction was performed as a model reaction to evaluate the performance of the millireactors. We observed that some of the reactors with static mixers had air plugs that created a significant dead volume but still exhibited higher conversions compared to the reference reactor. Our results demonstrate the potential of stereolithography for producing intricate millireactors with static mixers, which can enhance the productivity of chemical processes.

An innovative enzymatic polycondensation of dicarboxylic acids and dialcohols in aqueous polymerization media using free and immobilized lipases was developed. Various parameters (type of lipases, temperature, pH, stirring type and rate, and monomer carbon chain length) of the polycondensation in an oil-in-water (o/w) miniemulsion (>80% in water) were evaluated. The best results for polycondensation were achieved with an equimolar monomer concentration (0.5 M) of octanedioic acid and 1,8-octanediol in the miniemulsion and water, both at initial pH 5.0 with immobilized Pseudozyma antarctica lipase B (PBLI). The synthesized poly(octamethylene suberate) (POS) in the miniemulsion is characterized by a molecular weight of 7800 g mol-1 and a conversion of 98% at 45 • C after 48 h of polycondensation in batch operation mode. A comparative study of polycondensation using different operation modes (batch and fed-batch), stirring type, and biocatalyst reutilization in the miniemulsion, water, and an organic solvent (cyclohexane:tetrahydrofuran 5:1 v/v) was performed. Regarding the polymer molecular weight and conversion (%),batch operation mode was more appropriate for the synthesis of POS in the miniemulsion and water, and fed-batch operation mode showed better results for polycondensation in the organic solvent. The miniemulsion and water used as polymerization media showed promising potential for enzymatic polycondensation since they presented no enzyme inhibition for high monomer concentrations and excellent POS synthesis reproducibility. The PBLI biocatalyst presented high reutilization capability over seven cycles (conversion > 90%) and high stability equivalent to 72 h at 60 • C on polycondensation in the miniemulsion and water. The benefits of polycondensation in aqueous media using an o/w miniemulsion or water are the origin of the new concept strategy of the green process with a green product that constitutes the core of the new greener polymer-5B technology.

BACKGROUND: Oil-in-water miniemulsions have been suggested to display potential for application as a 'green' system for enzymatic alkyl ester synthesis. Still, a realistic assessment of the feasibility of this approach for practical applications requires further insight, namely the relation between enzyme stability and reaction operational conditions. The objective of this work is within such scope. Accordingly, it extends previous research on esterification catalyzed by Fusarium solani pisi cutinase, by addressing medium-chain length substrates, and aims to contribute to the optimization of reaction conditions and towards the design of an efficient setup. RESULTS: The esterification yield was significantly enhanced (e.g. 50% increase for octyl octanoate system) through the correction of the initial pH of the reaction medium to pH 6. Under such environment, conformational changes of the enzyme were negligible after 24 h, resulting in improved enzyme stability for all systems under study. Maximum esterification rate (3.59 mmol min-1) and product yield (91%) were achieved for octyl decanoate synthesis. Fed-batch mode of operation allowed for the production of 1 mol L-1 hexyl octanoate, while retaining enzyme activity over 5 days. Consecutive batch runs allowed for the cumulative production of 1.1 mol L-1 hexyl octanoate after four cycles. CONCLUSIONS: Medium engineering enabled the use of miniemulsion systems for the synthesis of medium-chain alkyl esters and increase in the final concentration of the intended product. Through a fed-batch mode the enzyme stability and reutilization were tuned allowing long-term utilization of the free enzyme which could not be achieved through a repeated batch system.

The present work aims to achieve additional insight on a mechanism describing the fundamental steps involved in the esterification reactions catalyzed by cutinase. The synthesis of ethyl caproate has been used as a model system to obtain a suitable kinetic model to estimate the activation energies involved in the various steps of the reaction pathway. Kinetic measurements have been made for the enzymatic esterification of caproic acid with ethyl alcohol catalyzed by recombinant Fusarium solani pisi cutinase expressed in Saccharomyces cerevisiae SU50. Different temperature conditions, from 25 to 50 • C, were tested for two different alcohol/acid molar ratios (R = 1 and R = 2). The third ordered Ping Pong Bi Bi mechanism with alcohol inhibition was shown to be able to describe the experimental results. The model shows that the productivity decreases as the reaction temperature increases.

Cutinase has been shown to be a promising biocatalyst for applications in processes targeted for industrial scale. This work aims to further contribute for highlighting such role, by bestowing detailed insight on the application of cutinase for the synthesis of value added compounds in miniemulsion environments (oil-in-water). The synthesis of hexyl octanoate was used as model system, due to the relevance of this compound for industrial applications as flavor and fragrance agent. The nature, specificity and selectivity of the catalyst enable operation under mild reaction conditions, without undesirable side reactions, leading to a very pure product. A high conversion yield, about 86%, for an enzyme concentration of 5 mg ml-1 , was achieved. Hexyl octanoate synthesis and cutinase activity for different acid: alcohol molar ratio (R), under different pH environments, were evaluated. A maximum cutinase activity of 2.20 mol mg-1 min-1 was observed for R = 0.5, which was tentatively ascribed to the stabilizing effect of hexanol on the miniemulsion. It is thus considered that the accumulation of the hydrophobic hexyl octanoate inside the droplets stabilize the miniemulsion system.

The effectiveness of Fusarium solani pisi cutinase-mediated synthesis of short-chain alkyl esters in organic solvent (iso-octane) media was evaluated. A five-level, fourvariable Central Composite Rotatable Design was employed. The parameters, chain length of alcohols and acids, alcohol and acid concentration, and the response (esterification yield and initial rate) were evaluated. The cutinase displayed an esterification yield above 95% for the C4-C6 acid and alcohol chain length with an optimal substrate concentration between 100 and 180 mM. Although an increase in acid and alcohol chain length resulted in a decrease of initial rate of reaction, the yield remained high (94% for the synthesis of butyl octanoate). PRACTICAL APPLICATIONS Short chain alkyl esters are very important flavoring compounds, appreciated for the fruity aroma they provide. Esterification is frequently encountered in the organic process industry in view of the diverse applications of esters in a variety of industries such as intermediates, pharmaceuticals, fine chemicals, fragrance and flavor chemicals, plasticizers, solvents and food. They are employed in fruit-flavored products (i.e., beverages, candies, jellies and jams), baked goods, wines and dairy products (i.e., cultured butter, sour cream, yogurt and cheese). Compounded flavor and fragrances are thus complex blends designed to impart either an attractive taste and aroma to processed foods and beverages, or a pleasing scent to consumer products such as perfumes, toiletries and household cleaners.

The main objective of this work was studying and testing the nature and influence of reaction media (organic solvent vs. miniemulsion system) on the synthesis of alkyl esters catalyzed by Fusarium solani pisi cutinase. Ester synthesis and cutinase selectivity for different chain length of acids and alcohols (ethyl and hexyl) were evaluated. In iso-octane, after 1 h of reaction, cutinase exhibits rates of esterification between 0.24 μmol × mg-1 × min-1 for ethyl oleate and 1.15 μmol × mg-1 × min-1 for ethyl butyrate, while in a miniemulsion system the rates were from 0.05 for ethyl heptanoate to 0.76 μmol × mg-1 × min-1 for ethyl decanoate. The reaction rate for the synthesis of hexyl esters in a miniemulsion system was from 0.19 for hexyl heptanoate to 1.07 μmol × mg-1 × min-1 for hexyl decanoate. High conversion yields of 95% at equilibrium after 8 h of reaction in iso-octane for pentanoic acid (C 5) with ethanol at equimolar concentration (0.1 M) was achieved. Additionally, this work showed that a significant and unexpected shift in cutinase selectivity occurred towards longer chain length carboxylic acids (C 8-C 10) in miniemulsion system as compared to organic solvent (iso-octane) and previous studies in reverse micellar systems. The possibility of working with higher concentration of substrates, without inhibitory effect on the enzyme, was another advantage of the miniemulsion system.

Zeolite physical and chemical characteristics and their impact on diffusion application of diffusional transport phenomena to catalysis diffusion in zeolites - theoretical considerations measurement of molecular transport in zeolites principles of shape selectivity examples of the interplay of diffusion and reaction in shape selective reactions impact of shape selective zeolites in industrial applications.

Wastewater treatment and reuse are essential for addressing water shortages and promoting sustainable water security and
sanitation development, particularly in rural areas. This paper aims to compare the performance of various oxidation processes,
including UV/photo-Fenton, solar photo-Fenton, solar photocatalysis using TiO2,
and UV/TiO2, for treating rural
wastewater using response surface methodology (RSM). The effects of several factors on the photocatalytic treatment performance
in terms of reducing organic pollutants and disinfecting wastewater were evaluated using Plackett–Burman and
Box–Behnken experimental designs. The outcomes indicate that pH is a crucial factor for enhancing photocatalytic treatment
efficiency. By optimizing the photocatalytic treatment conditions, the Fenton process achieved the highest removal efficiencies
for different pollutants. Specifically, at a pH of 3, a concentration of 1.678 mg/L of the reagent Fe2+
was sufficient to reduce
COD, TOC, and turbidity by 44.88, 55, and 97.21%, respectively, within just 1 h. Interestingly, the optimized conditions
led to significant removal of ammonium (69.74%). Bacteriological analyses further demonstrated reductions in total germs
and E. coli and the absence of streptococci. The effect of phytotoxicity on lettuce seed growth was evaluated in terms of the
germination index (GI). The treated wastewater showed no phytotoxic effects and achieved a GI above 99%. The findings
highlight the effectiveness of the Fenton process as a viable treatment alternative for enhancing effluent quality and increasing
the potential for the agricultural reuse of effluent as fertilizer.

Optimization of the homogeneous rhodium-catalyzed methanol carbonylation reactor to reduce CO2 emissions is studied in this line of research. In this paper, the steady-state homogeneous rhodium-catalyzed methanol carbonylation reactor is simulated using Aspen HysysV.9 software, by comparing the simulation results with industrial information, a mean relative error (excluding methanol) of 4.8% was obtained, which indicates the high accuracy of the simulation. The central composite design (CCD) and genetic algorithm (GA) with the aid of a simplified process simulation were used to estimate the effect of individual variables (liquid level, the temperature of the catalyst-rich recycle stream, the mole ratio of CO to methanol (MeOH) in the feed, and flow rate of dilute acid stream) and their mutual interactions to reduce CO2 emissions. It is obtained that the liquid level percentage of 46%, the catalyst-rich recycle stream temperature of 120 °C, CO: MeOH molar ratio equal to 1.13:1, and the dilute acid flow rate of 513.14 kmol/hr lead to CO2 reduction by 34%.

A mathematical model for the enzymatic kinetics of the synthesis of (R)-(+)-3,4-dihydroxyphenyllactic acid (DHPL) was developed. The synthesis was catalyzed by D-lactate dehydrogenase from Lactobacillus leishmannii. Since this enzyme requires NADH as a coenzyme, formate dehydrogenase system was used for NADH regeneration. Kinetic constants of both enzymes were estimated independently from initial reaction rate experiments. The developed mathematical model was verified by the batch reactor experiment (volumetric productivity in this experiment was 4.76 g dm -3 d -1 ). Optimization of initial reaction conditions for DHPL synthesis was performed using the genetic algorithm (GA). The genetic algorithm as a flexible optimization tool had been used to obtain the experimental conditions where maximal volumetric productivity could be achieved. The optimal initial conditions were found in the investigated parameter area: c 3,4-dihydroxyphenylpyruvic acid = 4.69 mmol dm -3 , c NAD+ = 4.95 mmol dm -3 , c formate = 36.85 mmol dm -3 , g D-lactate dehydrogenase = 3 mg cm -3 , g formate dehydrogenase = 2.94 mg cm -3 and the reaction time 8.5 min. At these conditions volumetric productivity of 93.06 g dm -3 d -1 can be achieved.

Non-steady state approaches have evolved and matured in kinetic research during the last decades. Sophisticated methods enable to get into fine details of chemical processes and their mechanism. At the same time, thermodynamics developed from the classical equilibrium theory to theories not limited by equilibrium, space or time homogeneity. Usually, kinetics and thermodynamics are treated separately as two different, though complementary approaches for description of chemically reacting systems. Within the framework of rational thermodynamics an interesting approach to chemical kinetics was developed. It was proved that the reaction rate is a function of concentration and temperature, which can be approximated by polynomial and this is further simplified using equilibrium criteria. Using this approach, non-traditional rate equations can be derived with new insights on the relations between mechanism, i.e. set of elementary steps, and kinetics. This contribution presents illustrative examples of this approach and discusses its consequences for mechanistic and kinetic interpretation of kinetic experiments and their design. Main points of the rational thermodynamics method include: (a) although it starts with independent reactions, resulting rate equations may also contain other reactions, relevant for the kinetic description; (b) kinetic equilibrium criteria are fulfilled with more general equation than usual Guldberg-Waage with no need for "kinetic" equilibrium constant; (c) reaction mechanism for given set of species is directly proposed.

Grafting reactions between end-functional polymers at polymer interfaces E.J. KRAMER, B.J. KIM, K. KATSOV, G.H. FREDRICKSON, UCSB, H. KANG, K. CHAR, Seoul National University -Reactions to produce graft copolymers at polymer interfaces during extruder mixing are important for controlling dispersed phase size by retarding droplet coalescence and reducing interfacial tension while providing interface reinforcement. We investigate such reactions at various temperatures in a model bilayer film system consisting of amine endfunctional deuterated polystyrene (dPS-NH 2 ) in PS and anhydride end-functional poly(2-vinylpyridine) (P2VP-anh) in P2VP as a function of molecular weight M and initial volume fraction ϕ 0 of the end functional chains. After various times of reaction the interfacial excess z* of block copolymer formed at the interface is determined by detecting the 2 H -ion using dynamic SIMS depth profiling. At low ϕ 0 (∼ 0.01) of dPS-NH 2 and P2VP-anh, such that the normalized interface excess z*/R g < 1 and the blocks are unstretched, the forward reaction rate constant k + decreases as M -0.68 in rough agreement with theoretical predictions (k + ∼ M -0.55 ) for this regime. The rate constant is thermally activated with an activation enthalpy 165 kJ/mol that is independent of M.

The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HCl, NOx, and SO 2 concentrations, ash constituents, and temperature. This report summarizes Year 2 results for the experimental and modeling tasks. Experiments in the mercury reactor are underway and interesting results suggested that a more comprehensive look at catalyzed surface reactions was needed. Therefore, much of the work has focused on the heterogeneous reactions. In addition, various chemical kinetic models have been explored in an attempt to explain some discrepancies between this modeling effort and others.

The objective of this project is to understand the importance of and the contribution of gas-phase and solid-phase coal constituents in the mercury oxidation reactions. The project involves both experimental and modeling efforts. The team is comprised of the University of Utah, Reaction Engineering International, and the University of Connecticut. The objective is to determine the experimental parameters of importance in the homogeneous and heterogeneous oxidation reactions; validate models; and, improve existing models. Parameters to be studied include HC1, NOx, and SO2 concentrations, ash constituents, and temperature. This report summarizes Year 3 results for the experimental and modeling tasks. Experiments have been completed on the effects of chlorine. However, the experiments with sulfur dioxide and NO, in the presence of water, suggest that the wet-chemistry analysis system, namely the impingers, is possibly giving erroneous results. Future work will investigate this M e r and determine the role of reactions in the impingers on the oxidation results. The solid-phase experiments have not been completed and it is anticipated that only preliminary work will be accomplished during this study.

A chemical reaction engineering model has been constructed to describe the extraction and recovery of bromine from a once-through seawater flow. The process uses a closed-loop circulation flow of air. This strips out free bromine from pre-chlorinated seawater in a packed column. Bromine liberated into the gas reacts with injected sulfur dioxide around a circulation loop to form liquid droplets containing product hydrobromic acid captured by mist elimination. Excesses of chlorine and sulfur dioxide compete for bromine and can reduce the recovery efficiency. Pseudo-homogeneous gas-phase kinetics accounts for simultaneous absorption and gas-liquid reaction of liberated bromine, excess chlorine, and injected sulfur dioxide. Re-circulating sulfur dioxide subsequently absorbs and reacts simultaneously with bromine and chlorine stripping. Parameter values are deduced for typical bromine recovery of 70%. The model can be used for optimizing the excesses of chlorine and sulfur dioxide.

A concept of the safety boundary diagram, elaborated in our previous studies for liquid-liquid heterogeneous reactions, has been developed here for liquid-phase homogeneous semibatch reactors. With the use of this boundary diagram, inherently safe-operating conditions can be easily determined without costly and time-consuming kinetic studies. A rapid procedure to estimate the dosing time and the cooling temperature appropriate for inherently safe operation of the reactor has been elaborated and proposed.

Detailed investigations have been carried out to check the ability of multilayer neural networks to model the simultaneous mass transfer and chemical reaction in the liquid}liquid reacting system. In this approach the intrinsic reaction kinetics and di!usive mass transfer are represented by a black-box and only the input}output signals are analysed. The data for training of the net have been taken from the experiments performed in a RC1 Mettler Toledo reaction calorimeter. The hydrolysis of propionic anhydrite catalysed with sulphuric acid has been chosen as a testing reaction. The hybrid, "rst-principle}neural-network model has been de"ned to describe batch and semibatch stirred tank reactors operating at di!erent conditions. Good accuracy and #exibility of the proposed approach have been obtained for a properly de"ned experimental programme supplying data for learning.

New aspects of neural modelling of chemical reactors have been investigated in this study. An universal method to create a family of neural models, useful for the reactor and reacting system of any type, has been elaborated and presented. Based on this method a detailed analysis of the neural models has been performed. The proposed methods of modelling as well as a comparative analysis of the obtained results have been illustrated with the data obtained for a complex, catalytic hydrogenation of 2,4-dinitrotoluene performed at non-steady state conditions in a multiphase stirred tank reactor. The methods of choosing the input Á/output signals, the net architecture, the learning method, the number and quality of learning data have been proposed and their influence on the accuracy of obtained predictions have extensively been discussed. A comparison of two types of neural models: a global neural model and a hybrid neural model to a conventional reactor modelling has been performed. General conclusions and useful criteria have been formulated.

A detailed analysis is presented for determining the reactant flux into a composite material containing randomly-located, reactive spherical centers. The governing equations are configurationally averaged assuming the spheres are distributed according to a hard-sphere potential. The resulting infinite hierarchy of coupled equations is truncated using physical considerations of screening and diluteness of the particulate phase. A general asymptotic solution is obtained valid to order c for all bounded and semiinfinite domains. The solution reproduces the mean-field result and includes the previously-neglected effects of sphere-boundary interactions. These interactions dominate the effect of two-sphere interactions which affect the solution at order c 3/Z In c. Explicit consideration is given to the case in which the domain is spherical or semi-infinite and a solution obtained for each. The solutions obtained generally predict an cnhanccd reactant flux relative to the mean-field result. The solution is illustrated by application iv the problem of coal ash vaporization.

This paper analyzes the steady-state behavior of two typical processes to produce poly(propylene): the single-reactor bulk polymerization process and the slurry polymerization process in a train of continuous stirred tank reactors. The investigation is performed using a commercial process simulator-SIMULPOL 3.0 1 , and aims at elucidating the general behavior of both processes when subject to perturbations of the input operation variables. Attention is given to the effect of the perturbations upon the polymer properties and to identification of process bottlenecks. Regarding the bulk polymerization process,

This paper analyzes the steady-state behavior of two typical processes to produce poly(propylene): the single-reactor bulk polymerization process and the slurry polymerization process in a train of continuous stirred tank reactors. The investigation is performed using a commercial process simulator-SIMULPOL 3.0 1 , and aims at elucidating the general behavior of both processes when subject to perturbations of the input operation variables. Attention is given to the effect of the perturbations upon the polymer properties and to identification of process bottlenecks. Regarding the bulk polymerization process,

The calcination reaction of two limestones and a dolomite with different porous structures was studied by thermogravimetric analysis. The effects of calcination temperature (1048-1173 K), particle size (0.4-2.0 mm), CO 2 concentration (0-80 %) and total pressure (0.1-1.5 MPa) were investigated. SEM analysis indicated the existence of two different particle calcination models depending on the sorbent type: a shrinking core model with a sharp limit between the uncalcined and calcined parts of the particle and a grain model with changing calcination conversion at the particle radial position. The appropriate reaction model was used to determine the calcination kinetic parameters of each sorbent. Chemical reaction and mass transport in the particle porous system were the main limiting factors of the calcination reaction at the experimental conditions. A Langmuir-Hinshelwood type kinetic model using the Freundlich isotherm was proposed to account the effect of the CO 2 during sorbent calcination. This allowed us to predict the calcination conversion of very different sorbents in a broad range of CO 2 partial pressures. Total pressure also inhibited the sorbent calcination. This fact was accounted by an additional decrease in the molecular diffusion coefficient with increasing total pressure with respect to the indicated by the Fuller's equation.

Optimization of the whole plant instead of important individual units is essential for maximizing savings and operational efficiency. Often, there are conflicting objectives for optimizing industrial processes. Many previous studies on multi-objective optimization involved a few critical units (and not complete plants) using models and simulation programs specifically developed for the respective application. Developing rigorous models and a separate code for simulating a complete plant, for the sake of multi-objective optimization is difficult and time consuming. There is potential to make this task easier by employing available process simulators such as Aspen Plus and Hysys. But these simulators do not currently have multi-objective optimization tools. Hence, an interface has been developed between Non-dominated Sorted Genetic Algorithm (NSGA-II) and Hysys. Plant-wide optimization using this interface involves three main steps: (a) development and testing of Hysys model for steady simulation of the process under study; (b) sensitivity analysis and selection of objectives, decision variables and constraints; and (c) optimization of the process for multiple objectives using NSGA-II. This paper describes optimization of a styrene unit/plant for multiple objectives using the interface and compares the obtained results with those obtained using an independently developed simulation program.

Multi-objective optimization of the operation and design of a styrene manufacturing process has been studied with the elitist nondominated sorting genetic algorithm (NSGA-II). In the first part, the study focused on bi-objective optimization and comparative analysis of three different styrene reactor designs-the single-bed, the steam-injected and the double-bed reactors. The objectives were to simultaneously maximize styrene flow rate and styrene selectivity. In the second part, on the other hand, a tri-objective optimization study was performed involving the entire manufacturing process consisting of the reactor, heat-exchangers and separation units. Only the double-bed reactor was considered in this study for maximizing the styrene flow rate and selectivity and minimizing the total heat duty required by the manufacturing process. Results are presented and discussed in detail.

This paper reports, for solutions of 0.001 M uranyl sulfate and 0.005 M oxalic acid, a 10-degree temperature coefficient, up to 85°C (using a base temperature of 25°) of 1.02±0.01 at 254 m/x. Measurements in more dilute solutions show a decrease to approximately unity at 0.00025 M uranyl sulfate—0.00125 M oxalic acid, with indication that it may become less than unity on further dilution. Quantum yields measured (using uranyl oxalate as standard), by students under a National Science Foundation &quot;pilot&quot; undergraduate participation project, on actinometers at 254 rn.fi, were for (1) malachite green leucocyanide, 0.9; (2) monochloroacetic acid, 0.3; and (3) potassium ferrioxalate, 1.24 moles per einstein. EXPERIMENTAL

The conventional kinetic analysis of an overall reaction (OR) is limited to a single sequential pathway of molecular steps at a time, based either on the general quasi-steady state (QSS) approach of Bodenstein, or on the much simpler but limited Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach based on assuming a single rate-determining step (RDS), the remaining being quasi-equilibrated (QE). We recently described a new algebraic methodology for deriving the QSS rate expression for a reaction sequence, which allowed interpretation of the final result in an Ohm's law form, i.e., OR rate =OR motive force/OR resistance of an equivalent electric circuit, where the consecutive mechanistic steps represent resistors in series. Here, we propose a similar Ohm's law form of QSS rate for a reaction system involving parallel pathways, whose equivalent electrical circuit derives directly from the reaction route (RR) Graph of its mechanism, as proposed earlier by us. The results are exact for a reaction network with mechanistic steps linear in intermediates concentrations, while they are approximate, albeit accurate, for non-linear step kinetics. We further show how the LHHW methodology, combined with the concept of intermediate reaction might be utilized to obtain the step resistances involved. For illustration, we utilize the relatively simple examples of: (1) the gas-phase hydrogen-bromine non-catalytic reaction (non-linear kinetics), and (2) zeolite catalyzed N 2 O decomposition reaction (linear kinetics). However, the approach is useful for more complex non-catalytic, catalytic and enzymatic reactions networks as well.

An alternate method, which we call as the R dot approach, to obtain the quasi steady state (QSS) rate expression for linear kinetics mechanisms (both sequential reaction mechanism and mechanisms with parallel pathways) had been recently proposed. This method requires the use of intermediate reaction routes (IRR's) to solve for the unknown intermediate species concentrations. In mechanisms where there are many choices of IRR's, it was not clear which one must be chosen so as to obtain the correct rate expression matching with the QSS rate expression. In this work, it is shown that the correct choice is the one which will make the rate limiting step (RLS) reversibility equal to the overall reversibility. This also provides a condition to check the applicability of the R dot method to a particular linear kinetics mechanism. For a mechanism with non linear kinetics, the R dot method may sometimes provide unsatisfactory approximations even if the applicability conditions are satisfied. These are illustrated through four mechanism examples.

In this paper, the experimental study has been carried out on CSTR in the presence of process faults which can occur due to sudden and unexpected change in certain process parameters. A neural network (NN) is an essential tool used in the fault diagnosis for the chemical processes, in particular. As the artificial neural networks (ANN) represent the nets of basis functions, these offer better empirical models, taking into account the complex nature of the non-linear processes. The faults like the change in flow rate and the change in agitator speed have been injected into the system simultaneously. Due to these faults, a difference in the output of CSTR, i.e. titration endpoint has been analysed. Moreover, while varying the speed of agitators, it has been observed that fault becomes prominent at high speed of each of the agitators. The experimental results have been simulated on the NN, after which the nature and magnitude of faults have been visualized.