Hydration Of Acrylonitrile Research Articles

Nitrile hydratase‐mediated conversion of acrylonitrile by Rhodococcus rhodochrous (RS‐6)

AbstractBACKGROUNDAcrylamide is an important monomer for the synthesis of polyacrylamide, which has wide applications in industries. This molecule can be produced by the hydration of acrylonitrile, catalyzed by the enzyme nitrile hydratase (NHase) secreted by microorganisms. Herein, synthesis of acrylamide was carried out by soil isolate Rhodococcus rhodochrous (RS‐6) contains NHase. The critical parameters affecting the bioconversion process such as pH, temperature, substrate concentration, resting cell concentration and acrylamide concentration were optimized by changing one parameter at a time.RESULTSThe optimum conditions for acrylonitrile conversion to acrylamide were observed at pH 7.0, temperature 15 °C, substrate concentration 1250 mmol L–1 and 1.4 mg dcw mL–1 concentration of resting cells. Under these improved conditions the entire bioconversion of acrylonitrile to acrylamide was observed within 75 min of incubation. The NHase of resting cells of R. rhodochrous (RS‐6) showed tolerance to acrylonitrile (7% w/v) and acrylamide up to 30%. Laboratory‐scale production by fed‐batch method resulted in an accumulation of 574 g L−1 acrylamide in 9 h.CONCLUSIONThe NHase‐containing resting cells of R. rhodochrous (RS‐6) catalyzed the maximum conversion of acrylonitrile to acrylamide under optimized conditions. © 2020 Society of Chemical Industry

ОЧИЩЕННЯ АКРИЛАМІДУ ВІД ІНГІБІТОРІВ ПОЛІМЕРИЗАЦІЇ ДЛЯ ВИГОТОВЛЕННЯ ВИСОКОЯКІСНИХ ФЛОКУЛЯНТІВ НА ОСНОВІ ПОЛІАКРИЛАМІДУ

Polyacrylamide and its copolymers are widely used as flocculating agents for the separation of industrial suspensions. The formation of high molecular weight polymers depends on the content of various impurities present in the monomer. The article presents the scientific and practical information on the production of acrylamide by sulfuric acid method of hydration of nitrile acrylic acid in the form of an aqueous solution of different concentrations and a more modern heterogeneously catalytic method of hydration of acrylonitrile using as catalysts with variable valence. Ways to get different impurities in the stages of production of acrylamide with the purpose of applying appropriate methods for its purification. Laboratory studies of the purification of an aqueous solution of acrylamide from iron ions were carried out as an element of inhibition of the premature polymerization process.

Effects of interface adsorption of Rhodococcus ruber TH3 cells on the biocatalytic hydration of acrylonitrile to acrylamide.

In this work, the drastic change in the reaction rate throughout the acrylonitrile bio-hydration reaction, which was catalyzed by Rhodococcus ruber TH3 free cells in a two-liquid-phase system, was studied by changing the initial mass fraction of acrylonitrile and acrylamide. We found that the reaction rate was sensitively affected by the contact area between the acrylonitrile droplets and cells. With the acrylonitrile mass fraction of 3wt%, the cell solution of 800 U/mL could make the superficial area of acrylonitrile droplets saturated. The sustained increase of the acrylamide concentration in the reaction process could reduce the reaction rate, and 25wt% was the obvious inflection point. The interface adsorption of cells was visually observed with the method of fluorescence microscopy, and the uptake mechanism of substrate by direct contact was illustrated to play a main role by comparing the reaction rate of the heterogeneous system and that of the homogeneous system.

AkzoNobel will boost its production of colloidal silica in Sweden

The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 (PtNHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a PtNHase:sol–gel biomaterial. The PtNHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of >90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the PtNHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native PtNHase. These data indicate that PtNHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions.

A kinetic study of the biological catalytic hydration of acrylonitrile to acrylamide

In this study, the kinetic characteristics of the bio-hydration of acrylonitrile by free cell catalysts were studied. Due to the aggregation phenomenon, free cell catalysts showed different characteristic when compared with free enzyme catalysts. The Michaelis constants were obtained through the homogeneous reaction. Both the values of Vm and Km increased with the increase in enzymatic activity, ranging from 100 to 500U/mL, and the variation trend of Km was not consistent with the rule of enzyme-catalyzed reaction. To reduce the external diffusion resistance of acrylonitrile to free cells, a membrane dispersion micro-reactor was used, and the conversion rates of acrylonitrile in the membrane dispersion micro-reactor under all of the experimental conditions reached approximately 90% of the max conversion rates. The reinforcement of the apparent reaction rate by the micro-reactor may have benefitted from the significant increase in the specific surface area of the acrylonitrile droplets and the adsorption of the free cell catalysts on the undissolved droplets.

Sapropel-based supports as novel macroporous carbon-mineral adsorbents for enzymatic active substances

The novel macroporous carbon-mineral Sapropel supports were obtained from lacustrine sapropel silts of freshwater lakes by annealing of semi-coke in the inert atmosphere. The specific surface area of these supports varied from 10 to 100 m2/g, the total pore volume from 0.3 cm3/g till 1.6 cm3/g; macropores of diameters more than 2 μm were predominating. The Sapropel supports were studied for the adsorption/adhesion ofenzymatic active substances, such as whole bacterial cells, and invertase-active fully destroyed baker’s yeast cells (autolysates), and purified enzyme nitrilase. The heterogeneous biocatalysts with required enzymatic activity were prepared and their properties were studied in the corresponding bioconversion processes. The invertase-active biocatalysts exhibited high activity, 120–135 U/g, and stability; the half-times of theirinactivation (t½) were more than 1000 h in the continuous process of sucrose hydrolysis at 50 °C. The nitrilase-active biocatalysts for “green” chemistry of nitriles possessed high activity, 350–500 U/g, and the t½ were estimated to be more than 100 h in the periodic process of hydration of acrylonitrile to acrylic acid at 22 °C.

Sapropel-based supports as novel macroporous carbon-mineral adsorbents for enzymatic active substances

The novel macroporous carbon-mineral Sapropel supports were obtained from lacustrine sapropel silts of freshwater lakes by annealing of semi-coke in the inert atmosphere. The specific surface area of these supports varied from 10 to 100 m2/g, the total pore volume from 0.3 cm3/g till 1.6 cm3/g; macropores of diameters more than 2 µm were predominating. The Sapropel supports were studied for the adsorption/adhesion of enzymatic active substances, such as whole bacterial cells, and invertase-active fully destroyed baker's yeast cells (autolysates), and purified enzyme nitrilase. The heterogeneous biocatalysts with required enzymatic activity were prepared and their properties were studied in the corresponding bioconversion processes. The invertase-active biocatalysts exhibited high activity, 120–135 U/g, and stability; the half-times of their inactivation (t½) were more than 1000 h in the continuous process of sucrose hydrolysis at 50°C. The nitrilase-active biocatalysts for “green” chemistry of nitriles possessed high activity, 350–500 U/g, and the t½ were estimated to be more than 100 h in the periodic process of hydration of acrylonitrile to acrylic acid at 22°C.

Multiple reuses of Rhodococcus ruber TH3 free cells to produce acrylamide in a membrane dispersion microreactor

In this work, multiple reuses of Rhodococcus ruber TH3 free cells for the hydration of acrylonitrile to produce acrylamide in a membrane dispersion microreactor were carried out. Through using a centrifuge, the reactions reached 39.9, 39.5, 38.6 and 38.0wt% of the final acrylamide product concentration respectively within 35min in a four cycle reuse of free cells. In contrast, using a stirring tank, free cells could only be used once with the same addition speed of acrylonitrile with a microreactor. Through observing the dissolution behavior of acrylonitrile microdroplets in a free cell solution using a coaxial microfluidic device and microscope, it was found that the acrylonitrile microdroplets with a diameter of 75μm were rarely observed within a length of 2cm channel within 10s, which illustrated that the microreactor can intensify the reaction rate to reduce the inhibition of acrylonitrile and acrylamide.

Visual study of mass transfer characterization in the process of biological catalytic hydration of acrylonitrile using pendant drop method

In this work, a pendant drop method was utilized to observe visually the mass transfer process of an acrylonitrile droplet during bio-hydration.

Hydration of acrylonitrile to produce acrylamide using biocatalyst in a membrane dispersion microreactor

In this work, a membrane dispersion microreactor was utilized for the hydration of acrylonitrile to produce acrylamide. Through observation using a microscopy, it was found that the acrylonitrile was dispersed into the continuous phase (the aqueous phase contains nitrile hydratase (NHase)) as droplets with a diameter ranged from 25 to 35μm, hence the mass transfer specific surface area was significantly increased, and the concentration of acrylamide reached 52.5wt% within 50min. By contrast, in stirred tanks, the concentration of acrylamide only got 39.5wt% within 245min. Moreover, only a few amounts of acrylonitrile were accumulated in this microreactor system. Through optimizing the flow rate, the concentration of acrylamide reached 45.8wt% within 35min, the short reaction time greatly weakened the inhibition of acrylonitrile and acrylamide on the enzyme activity, which is suitable for prolonging the life of free cell.

Acrylamide production using encapsulated nitrile hydratase from Pseudonocardia thermophila in a sol–gel matrix

Abstract The cobalt-type nitrile hydratase from Pseudonocardia thermophila JCM 3095 ( Pt NHase) was successfully encapsulated in tetramethyl orthosilicate sol–gel matrices to produce a Pt NHase:sol–gel biomaterial. The Pt NHase:sol–gel biomaterial catalyzed the conversion of 600 mM acrylonitrile to acrylamide in 60 min at 35 °C with a yields of >90%. Treatment of the biomaterial with proteases confirmed that the catalytic activity is due to the encapsulated enzyme and not surface bound NHase. The biomaterial retained 50% of its activity after being used for a total of 13 consecutive reactions for the conversion of acrylonitrile to acrylamide. The thermostability and long-term storage of the Pt NHase:sol–gel are substantially improved compared to the soluble NHase. Additionally, the biomaterial is significantly more stable at high concentrations of methanol (50% and 70%, v/v) as a co-solvent for the hydration of acrylonitrile than native Pt NHase. These data indicate that Pt NHase:sol–gel biomaterials can be used to develop new synthetic avenues involving nitriles as starting materials given that the conversion of the nitrile moiety to the corresponding amide occurs under mild temperature and pH conditions.

Unraveling the Reaction Mechanism on Nitrile Hydration Catalyzed by [Pd(OH2)4]2+: Insights from Theory

Density functional theory methodologies combined with continuum and discrete-continuum descriptions of solvent effects were used to investigate the [Pd(OH2)4](2+)-catalyzed acrylonitrile hydration to yield acrylamide. According to our results, the intramolecular hydroxide attack mechanism and the external addition mechanism of a water molecule with rate-determining Gibbs energy barriers in water solution of 27.6 and 28.3 kcal/mol, respectively, are the most favored. The experimental kinetic constants of the hydration started by hydroxide, k(OH), and water, k(H2O), attacks for the cis-[Pd(en)(OH2)2](2+)-catalyzed dichloroacetonitrile hydration rendered Gibbs energy barriers whose energy difference, 0.7 kcal/mol, is the same as that obtained in the present study. Our investigation reveals the nonexistence of the internal attack of a water ligand for Pd-catalyzed nitrile hydration. At the low pHs used experimentally, the equilibrium between [Pd(OH2)3(nitrile)](2+) and [Pd(OH2)2(OH)(nitrile)](+) is completely displaced to [Pd(OH2)3(nitrile)](2+). Experimental studies in these conditions stated that water acts as a nucleophile, but they could not distinguish whether it was a water ligand, an external water molecule, or a combination of both possibilities. Our theoretical explorations clearly indicate that the external water mechanism becomes the only operative one at low pHs. On the basis of this mechanistic proposal it is also possible to ascribe an (1)H NMR signal experimentally detected to the presence of a unidentate iminol intermediate and to explain the influence of nitrile concentration reported experimentally for nitriles other than acrylonitrile in the presence of aqua-Pd(II) complexes. Therefore, our theoretical point of view on the mechanism of nitrile hydration catalyzed by aqua-Pd(II) complexes can shed light on these relevant processes at a molecular level as well as afford valuable information that can help in designing new catalysts in milder and more efficient conditions.

Engineering ofRhodococcuscell catalysts for tolerance improvement by sigma factor mutation and active plasmid partition

Tolerance to various stresses is a key phenotype for cell catalysts, which are used widely in bioproduction of diverse valuable chemicals. Using the Rhodococcus ruber TH strain, which exhibits high nitrile hydratase activity, as the target cell catalyst for acrylamide production, we established a method to improve cell tolerance by stably introducing global transcription perturbation. The σ(70) gene (sigA) of R. ruber was cloned and randomly mutated. An R. ruber TH3/pNV-sigA(M) library containing additional sigA mutants was constructed and used for survival selection. The TH3/M4N1-59 mutant was selected by acrylonitrile/acrylamide double stress and exhibited a 160 % extension of the half-life of nitrile hydratase upon exposure to 40 % acrylamide. A redesigned parDE(M) gene was introduced to Rhodococcus to accomplish stable inheritance of plasmids. A two-batch acrylonitrile hydration reaction was performed using the engineered cells as a catalyst. Compared to TH3, the acrylamide productivity of TH3/M4N1-59DE(M) catalysis increased by 27.8 and 37.5 % in the first and second bioreaction batches, respectively. These data suggest a novel method for increasing the bioconversion productivity of target chemicals through sigA mutation of the cell catalyst.

A Highly Efficient Cu/Al(OH)3 Catalyst for the Hydration of Acrylonitrile to Acrylamide

Abstract A highly efficient, easily filterable Cu/Al(OH)3 catalyst for the hydration of acrylonitrile to acrylamide has been synthesized by reducing a particle-size-controlled malachite phase-free Cu/Al hydrotalcite. The stability of the Cu/Al(OH)3 catalyst under aqueous reaction conditions was further improved by treatment with H3PO4.

A study of the catalytic properties of the nitrile hydratase immobilized on aluminum oxides and carbon-containing adsorbents

The nitrile hydratase isolated from Rhodococcus ruber strain gt1, displaying a high nitrile hydratase activity, was immobilized on unmodified aluminum oxides and carbon-containing adsorbents, including the carbon carrier Sibunit. The activity and operational stability of the immobilized nitrile hydratase were studied in the reaction of acrylonitrile transformation into acrylamide. It was demonstrated that an increase in the carbon content in the carrier led to an increase in the amount of adsorbed enzyme and, concurrently, to a decrease in its activity. The nitrile hydratase immobilized on Sibunit and carbon-containing aluminum alpha-oxide having a "crust" structure displayed the highest operational stability in acrylonitrile hydration. It was shown that the thermostability of adsorbed nitrile hydratase increased by one order of magnitude.

Preparation and characterization of supports with a synthesized layer of catalytic filamentous carbon: IV. Synthesis of carbon nanofibers on a Co/Al2O3 catalyst

A comparative study of the synthesis of carbon layers, including catalytic filamentous carbon, on the surface of various alumina modifications was made. The synthesis was performed by the pyrolysis of alkanes (a propane-butane mixture) on Co/Al2O3 supported catalysts. The texture characteristics (specific surface area and pore structure) of the starting supports and adsorbents with a synthesized carbon layer were studied. The surface morphology of Co/Al2O3 catalysts and the synthesized carbon deposits was studied by scanning electron microscopy. It was found that carbon nanofibers were formed only on the catalysts prepared by the homogeneous precipitation of Co compounds onto the surface of macroporous α-Al2O3, whereas carbon deposits on mesoporous aluminum oxides did not exhibit a pronounced fibrous structure. The applicability of C/Co/Al2O3 carbon-containing adsorbents to the immobilization of the nitrile hydratase enzyme and the preparation of a biocatalyst for acrylonitrile hydration to acrylamide was considered.

Identification of nitrile hydratase-producing Rhodococcus ruber TH and characterization of an amiE-negative mutant

Microbial transformation of acrylonitrile to acrylamide by nitrile hydratase is of great interest to green chemistry. During the transformation, acrylic acid is generally accumulated as a by-product through biocatalysis of amidase. A novel strain with high nitrile hydratase activity was isolated from soil and identified as Rhodococcus ruber TH by morphology and 16S rRNA gene analysis. An amidase-negative recombinant, R. ruber TH3 was constructed. Its nitrile hydratase activity was 25% higher than that of the wild type, reaching 490 ± 29.2 U/mg dry cell weight, while the amidase activity was 60% lower. After 6 h hydration of acrylonitrile using free cells as biocatalysts at 18 °C, acrylamide production by TH3 was 23% higher and the production of the by-product, acrylic acid, was 87% lower than that of the wild type. This result demonstrates that the strain TH3 could be valuable for industrial applications.

Analyzing the Catalytic Mechanism of the Fe-Type Nitrile Hydratase from Comamonas testosteroni Ni1

In order to gain insight into the catalytic mechanism of Fe-type nitrile hydratases (NHase), the pH and temperature dependence of the kinetic parameters k cat, K m, and k cat/ K m along with the solvent isotope effect were examined for the Fe-type NHase from Comamonas testosteroni Ni1 ( CtNHase). CtNHase was found to exhibit a bell-shaped curve for plots of relative activity vs pH over pH values 4-10 for the hydration of acrylonitrile and was found to display maximal activity at pH approximately 7.2. Fits of these data provided a p K ES1 value of 6.1 +/- 0.1, a p K ES2 value of 9.1 +/- 0.2 ( k' cat = 10.1 +/- 0.3 s (-1)), a p K E1 value of 6.2 +/- 0.1, and a p K E2 value of 9.2 +/- 0.1 ( k' cat/ K' m of 2.0 +/- 0.2 s (-1) mM (-1)). Proton inventory studies indicate that two protons are transferred in the rate-limiting step of the reaction at pH 7.2. Since CtNHase is stable to 25 degrees C, an Arrhenius plot was constructed by plotting ln( k cat) vs 1/ T, providing an E a of 33.3 +/- 1.5 kJ/mol. Delta H degrees of ionization values were also determined, thus helping to identify the ionizing groups exhibiting the p K ES1 and p K ES2 values. Based on Delta H degrees ion data, p K ES1 is assigned to betaTyr68 while p K ES2 is assigned to betaArg52, betaArg157, or alphaSer116 (NHases are alpha 2beta 2 heterotetramers). Given the strong similarities in the kinetic data obtained for both Co- and Fe-type NHase enzymes, both types of NHase enzymes likely hydrate nitriles in a similar fashion.

Synthesis of manganese oxide octahedral molecular sieves containing cobalt, nickel, or magnesium, and the catalytic properties for hydration of acrylonitrile

Abstract An octahedral molecular sieve known as OMS-1 has todorokite structure composed of magnesium and manganese oxides, which was named as Mg-todorokite here. Octahedral molecular sieves containing cobalt (Co-todorokite) or nickel (Ni-todorokite) without magnesium were prepared by a sequential method under optimum conditions and compared with the Mg-todorokite by powder XRD, ICP, FESEM, and catalytic reactions. The compositions of Co-todorokite, Ni-todorokite, and Mg-todorokite are Co0.37MnO2.3(H2O)2.1, Ni0.24MnO2.0(H2O)2.1, and Mg0.22MnO2.0(H2O)2.2, respectively. The Co-todorokite and Ni-todorokite are comparable in crystallinity with the highly crystalline Mg-todorokite. The catalytic properties were examined for the hydration of acrylonitrile. The apparent activation energies depend on the foreign metals. The order is Co-todorokite

Synthesis, Structure, and Reactivity of Iron-Sulfur Species in Zeolites

Previous studies have shown that a variety of iron-oxo species, including nanoclusters and dimers, can be formed within the pore structure of ZSM-5 and other porous materials. We report that these species can readily be sulfided by exposure to hydrogen sulfide at 623 K when formed in ZSM-5, mordenite, and MCM-41. The iron-sulfur entities produced have been characterized by XPS and EXAFS spectroscopy. Iron is in the oxidation state +2 and the nearest neighbor iron-sulfur interatomic distance is ∼2.25 A, which is close to that in iron(II) sulfide. Sulfidation appears to be at least 90% complete. In ZSM-5 the same iron-sulfur species, which contains isolated iron atoms or very small clusters, is formed irrespective of whether the iron was introduced by aqueous exchange or chemical vapor deposition. The sulfided ZSM-5 material is found to be weakly active for the hydration of acrylonitrile to acrylamide in tetrahydrofuran solution at 338 K, with the best materials achieving about 0.5 turnovers per iron species per day.