High Space-time Yield Research Articles

Highly stable In-SBA-15 catalyst for vapor phase Beckmann rearrangement reaction

The Indium doped SBA-15 material was prepared by sol-gel method and tested for vapor phase Beckman rearrangement reaction. Among three indium loading, In/Si ratio of 2/100 was found as an optimum composition in terms of caprolactam selectivity (100%) and cyclohexanone oxime conversion (100%). The catalysts were characterized by N2 adsorption, small-angle X-rays/neutron scattering (SAXS/SANS), XRD, FESEM, HRTEM, EDX, UV, FTIR and NH3-TPD techniques. In-situ SANS experiment was performed on the adsorption of CO2 to detect the micropores in the mesopore wall. All catalysts samples have highly ordered hexagonal structure with well dispersed indium in the silica matrix. The fine tuning of weak and strong acid sites were found in indium doped SBA-15 (In/Si = 2/100) catalyst. The same catalyst showed optimum catalytic performance, high space time yield 114.4 mol/h/gcat and high stability till 6 h of reaction without deactivation. The micro-kinetic analysis showed that there were no external and internal diffusion limitations in the SBA-15 catalyst. The reaction mechanism of Beckmann rearrangement over In-SBA-15 has been elucidated.

Studies on dissolution kinetics of dolime in electrothermal magnesium slag

The electrothermal process of magnesium metal production is a promising route, where large sized internally heated reactor is used for magnesium production resulting in less energy and labour intensive and high space-time yield process. However, the dissolution behavior of dolime in the electrothermal slag has been found critical for the process optimization. In this paper, the dissolution kinetics of the dolime in the slag was discussed. Quaternary slag (CaO-Al2O3-SiO2-MgO) was prepared having basicity CaO/SiO2 ≥ 1.8 and Al2O3/SiO2 ≥ 0.26 for dolime dissolution studies by static hot dip method. Prior to the experiments, FactSage calculations were carried out varying temperatures and slag compositions. In the kinetic studies, dolime particles 10–15 mm size was added in slag melted at 1450, 1500 and 1550°C and samples were taken at various time intervals. The chemical analysis of slag sample was carried out to investigate the dissolution kinetics to establish the rate expression. The activation energy for the process was calculated for different models used in study and was found to be in the range of 130–270 kJ/mol. SEM analysis was done for surface analysis of reacted particles. This study would be helpful in optimizing the dolime charging rate during pilot scale trials for electrothermal magnesium production at CSIR-NML, Jamshedpur.

Optimizing renewable oil hydrocracking conditions for aviation bio-kerosene production

In the present work we have performed a parameter study to maximize the yields of aviation bio-kerosene and renewable diesel range products obtained from the conversion of plant-oil triglycerides over Ni–W/SiO2–Al2O3, hydrocracking catalyst. Specific insights and changes in reaction mechanisms, with CO bond breaking favoured at increased pressures (>60bar) leading to depropanation/deoxygenation, as compared to CC bond breaking becoming favoured at reduced pressures (<60bar) leading to formation of lower range esters and short chain glycerides, are established for the first time using analytical techniques (GC, NMR and IR). The CC cleavage and low hydrogen partial pressures (<60bar) led to formation of unsaturated intermediates, which promoted cyclization, aromatization and coking reactions, which increased deactivation of catalyst. High space time yield with a maximum of 240ml/(h⋅Lcatalyst) for <C9 products and 350ml/(h⋅Lcatalyst) for C9–C14 products was observed at 420°C temperatures. Stable catalytic performance was observed until 450h of continuous operation with 25–30% yield of aviation bio-kerosene which meets all ASTM D 7566 standards.

Stable and efficient aromatic yield from methanol over alkali treated hierarchical Zn-containing HZSM-5 zeolites

Fast deactivation of catalyst is the main problem in methanol-to-aromatics (MTA) process. Herein, Zn-containing HZSM-5 zeolites with hierarchical pores (H-Zn/HZSM-5) were prepared by treating directly synthesized Zn/HZSM-5 with NaOH solution. The changes in crystallinity, acidity and textural properties of Zn/HZSM-5 before and after alkali treatment were characterized by X-ray diffraction, NH3-TPD, 27Al MAS-NMR, N2 physisorption, X-ray fluorescence and TEM techniques. MTA reaction under the operating conditions of T = 400 °C and WHSV = 2.5 h−1 showed that the aromatic yield was improved from 41.4% for HZSM-5 to 55.3%. Furthermore, H-Zn/HZSM-5 exhibited a high initial space time yield of 0.62 g gcat−1 h−1 and a long lifetime up to 120 h. These results could be ascribed to the hierarchical pores and the providential acidity, which enhanced the adsorption and diffusion of intermediates/products during the reaction.

Enzymatic production of key intermediate of gabapentin by recombinant amidase from Pantoea sp. with high ratio of substrate to biocatalyst

1-Cyanocyclohexaneacetic acid is the key intermediate of gabapentin. A novel bioprocess catalyzed by amidase was developed for efficient production of 1-cyanocyclohexaneacetic acid from 1-cyanocyclohexaneacetamide, which can be prepared with high efficiency by nitrile hydratase-catalyzed regioselective hydration of 1-cyanocyclohexaneacetonitrile. Kinetic analysis and molecular docking of three recombinant amidase demonstrated that amidase (Pa-Ami) from Pantoea sp. was the most robust biocatalyst for hydrolysis of 1-cyanocyclohexaneacetamide with the kcat/Km value of 208.2±16.2mM−1s−1. Some key parameters of the bioprocess, such as substrate loading, catalyst loading and product inhibition, were investigated. Enzymatic hydrolysis of 80g/L of 1-cyanocyclohexaneacetamide was completed within 20min using 1g/L wet whole cells of recombinant Escherichia coli BL21, leading to high ratio of substrate to catalyst (S/C-ratio, 80) and high space-time yield (5794.7gproductL−1d−1). These encouraging results indicated the great potential of Pa-Ami in practical production of gabapentin.

Hydrogenolysis of Glycerol to 1,3-propanediol under Low Hydrogen Pressure over WOx -Supported Single/Pseudo-Single Atom Pt Catalyst.

Single/pseudo-single atom Pt catalyst was prepared on mesoporous WOx . The large surface area and abundant oxygen vacancies of WOx improve the Pt dispersion and stabilize the Pt isolation. This newly prepared catalyst exhibited outstanding hydrogenolysis activity under 1 MPa H2 pressure with a very high space-time yield towards 1,3-propanediol (3.78 g gPt (-1) h(-1) ) in Pt-W catalysts. The highly isolated Pt structure is thought to contribute to the excellent H2 dissociation capacity over Pt/WOx . The high selectivity towards 1,3-propanediol is attributed to the heterolytic dissociation of H2 at the interface of Pt and WOx (providing specific Brønsted acid sites and the concerted dehydration-hydrogenation reaction) and the bond formation between glycerol and WOx , which favors/stabilizes the formation of a secondary carbocation intermediate as well as triggers the redox cycle of the W species (W(6+) ⇄W(5+) ).

Mass and heat transfer behavior of a rotating disc with parallel rectangular grooves

Rates of liquid-solid mass transfer at a rotating disc with parallel rectangular grooves were measured by the electrochemical technique. Variables studied were disc rotation speed, groove depth (e) and physical properties of the solution. Grooves were found to enhance the rate of mass transfer by a factor ranging from 1.23 to 2.24 depending on groove depth and disc rotation speed. The data were correlated by the dimensionless equation:Shr=0.928 Sc0.33Re0.54 (e/w)0.276Implication of the present study for the design and operation of equipments which use the rotating disc such as pump electrochemical reactor and high space time yield of multirotating disc electrochemical and catalytic reactors was highlighted. Also the importance of the present work for the design and operation of high efficiency membrane processes such as ultrafiltration and dialysis was noted.

Effect of Surface Roughness on the Rate of Mass Transfer at a Vertical Cylinder Under Swirl Flow in Relation to Electrochemical and Catalytic Reactor Design

In order to enhance the rate of production of catalytic and electrochemical annular reactors used to conduct diffusion controlled reactions the effect of surface roughness on the rate of mass transfer at the inner cylinder of the annulus was studied under swirl flow. The effect of the following parameters on the rate of mass transfer was studied by the electrochemical technique: solution velocity, degree of roughness, physical properties of the solution, height of the inner cylinder and effect of drag reducing polymers. Roughness was made by cutting longitudinal V grooves in the inner cylinder transverse to swirl flow. The mass transfer data at the rough cylinder were correlated by the dimensionless equation: Drag reducing polymers were found to decrease the rate of mass transfer by an amount ranging from 5 to 23%. Importance of the present results for the design and operation of high space-time yield electrochemical reactors and biochemical reactors employing immobilized enzymes was pointed out. Also, the importance of the present results in the design and operation of membrane processes employing annular apparatus with a corrugated membrane was highlighted. By virtue of the analogy between heat and mass transfer the present results can be used to design more efficient double tube heat exchangers.

Enzymatic preparation of d-phenyllactic acid at high space-time yield with a novel phenylpyruvate reductase identified from Lactobacillus sp. CGMCC 9967

An NADH-dependent phenylpyruvate reductase (LaPPR) was identified through screening the shotgun library of Lactobacillus sp. CGMCC 9967. It belongs to d-3-phosphoglycerate dehydrogenase (PGDH) subfamily of 2-hydroxy acid dehydrogenase superfamily. LaPPR was stable at pH 6.5 and 30°C, with a half-life of 152h. LaPPR has a substrate preference towards aromatic to aliphatic keto acids, and various keto acids could be reduced into d-hydroxy acids with excellent enantioselectivity (>99%). By construction the coexpression system with glucose dehydrogenase, as much as 100gL−1 phenylpyruvic acid was asymmetrically reduced into d-phenyllactic acid with 91.3% isolation yield and 243gL−1d−1 productivity. The results suggest that LaPPR is a promising biocatalyst for the efficient synthesis of optically pure d-phenyllactic acid.

Chemoenzymatic synthesis of (R)- and (S)-propranolol using an engineered epoxide hydrolase with a high turnover number

Simultaneous synthesis of the R- and S-enantiomers of biologically active propranolol, a typical β-blocker, was achieved in high optical purity via an epoxide hydrolase-catalyzed resolution of racemic α-naphthyl glycidyl ether (rac-1). A preparative resolution of 100g/L rac-1 was accomplished with high enantioselectivity (E=92) using a variant of Bacillus megaterium epoxide hydrolase (BmEHF128T). A biphasic system (isopropyl ether/isooctane/aqueous) was used, in which the product 3-(1⿲-naphthyloxy)-propane-1,2-diol (2) precipitated instantly, facilitating its separation and increasing the enantiopurity of (R)-2 (>99.5% ee). This enzymatic resolution had a total turnover number of 70,000, affording enantiopure epoxide (S)-1 (>99% ee) and 1,2-diol (R)-2 (>99% ee) in 45.3% and 42.4% yields, respectively. (R)-2 and (S)-1 were subsequently converted to (R)- and (S)-propranolol (3) (>99% ee) in overall yields of 31.4% and 44.8%. To the best of our knowledge, this is the best case for enzymatic resolution of rac-1 using an epoxide hydrolase, giving high space-time yields [136gL⿿1days⿿1 for (S)-1 and 139gL⿿1days⿿1 for (R)-2] under mild reaction conditions. It provides a new and eco-friendly route that complements other methods using organometallic catalysts.

Continuous microreactor synthesis of ZIF-8 with high space–time-yield and tunable particle size

The continuous synthesis of the metal–organic framework ZIF-8 is described, employing microreaction technology which provides highly controlled mass and heat transport conditions. Using a T-type micromixer connected with a residence time capillary, crystalline ZIF-8 with excellent product characteristics and remarkable reproducibility is produced within seconds. The product is obtained at production rates of up to 640g/day which corresponds to a theoretical space–time yield of 210,000kg/m3*day. The modular process setup allows easy scale-up into the several kilogram range. Additionally, by modifying the reaction and process conditions it is possible to intentionally tailor both, the microscopic (crystal form and size) and macroscopic morphology of the product.

Optimised room temperature, water-based synthesis of CPO-27-M metal-organic frameworks with high space-time yields.

The exceptional porosity of Metal-Organic Frameworks (MOFs) could be harnessed for countless practical applications. However, one of the challenges currently precluding the industrial exploitation of these materials is a lack of green methods for their synthesis. Since green synthetic methods obviate the use of organic solvents, they are expected to reduce the production costs, safety hazards and environmental impact typically associated with MOF fabrication. Herein we describe the stepwise optimisation of reaction parameters (pH, reagent concentrations and reaction time) for the room temperature, water-based synthesis of several members of the CPO-27/MOF-74-M series of MOFs, including ones made from Mg(II), Ni(II), Co(II) and Zn(II) ions. Using this method, we built MOFs with excellent BET surface areas and unprecedented Space-Time Yields (STYs). Employing this approach, we have synthesised CPO-27-M MOFs with record BET surface areas, including 1279 m2 g-1 (CPO-27-Zn), 1351 m2 g-1 (CPO-27-Ni), 1572 m2 g-1 (CPO-27-Co), and 1603 m2 g-1 (CPO-27-Mg). We anticipate that our method could be applied to produce CPO-27-Ni, -Mg, -Co and -Zn with STYs of 44 Kg m-3 day-1, 191 Kg m-3 day-1, 1462 Kg m-3 day-1 and a record 18720 Kg m-3 day-1, respectively.

Efficient synthesis of a statin precursor in high space-time yield by a new aldehyde-tolerant aldolase identified from Lactobacillus brevis

A novel 2-deoxyribose-5-phosphate aldolase (LbDERA) was identified from Lactobacillus brevis, with high activity, excellent thermostability and high tolerance against aldehyde substrates.

Revisiting Cytochrome P450‐Mediated Oxyfunctionalization of Linear and Cyclic Alkanes

AbstractCytochrome P450 monooxygenases (CYPs) of the CYP153 family catalyse terminal hydroxylation of n‐alkanes. Alkane hydroxylating mutants of self‐sufficient CYP102A1 have also been described. We evaluated two CYP153s (a three‐component system and a fused self‐sufficient CYP), wild‐type CYP102A1 and nine CYP102A1 mutants, for the conversion of three cycloalkanes (C6, C7 and C8) and three n‐alkanes (C6, C8 and C10) using whole cells (WCs) and crude cell‐free extracts (CFEs). The aim was to identify substrate–enzyme combinations that give high product titres and space‐time yields (STYs). Comparisons were made using total turnover numbers (TTNs) and turnover frequencies (TOFs) to normalize for CYP expression. Reactions were carried out using high enzyme and substrate concentrations compatible with high STYs. Under these conditions CYP102A1 and the double R47L,Y51F mutant, although not regioselective, performed better on all substrates in terms of product titres over 8 h, and thus STYs and TTNs, than heavily mutated variants that have been reported to give very high TOFs. CYP153A6, with its ferredoxin (Fdx) and ferredoxin reductase (FdR), emerged as the superior catalyst for conversion of n‐alkanes. In addition to its excellent regioselectivity it also gave the highest final product titres and STYs in WC conversions of hexane and octane. Interaction with FdR and Fdx initially limited performance in CFEs, but with additional FdR and Fdx gave 1‐octanol titres of 50 mmol⋅LBRM−1 and TTNs exceeding 12,000 over 18 h, rivalling results reported with self‐sufficient CYPs. Selecting biocatalysts for application requires caution, since experimental conditions such as amount of substrate added and solubility as well as cofactor dependence and regeneration can have a profound effect on catalyst performance, while stability and efficiency with regard to cofactor usage (coupling efficiency) are at least as important as TOFs when high product titres and STYs are the target.magnified image

Biocatalytic Production of Catechols Using a High Pressure Tube-in-Tube Segmented Flow Microreactor

This study reports the synthesis of 3-phenylcatechol at the preparative scale using a continuous segmented flow tube-in-tube reactor (TiTR). 2-Hydroxybiphenyl 3-monooxygenase (HbpA) was applied as a biocatalyst for the hydroxylation reaction, which is dependent on the substrate 2-hydroxybiphenyl, NADH, and oxygen. While the regeneration of the cofactor NADH was guaranteed by formate dehydrogenase (FDH), oxygen was supplied via the membrane surface from the outside of the reactor system. The oxygen transfer rate through the membrane of the TiTR was determined to be 24 μmol O2 min–1 mL–1 emphasizing the potential of the TiTR as promising technology for realizing gas-dependent enzymatic reactions. Residence time and total turnover number have been identified as key limiting parameters. It was possible to scale-up this system by extending the TiTR by additional residence time units. This allowed synthesis of 1 g of 3-phenylcatechol at a high space time yield of 14.5 g L–1 h–1.

Double substituted variant of Bacillus amyloliquefaciens esterase with enhanced enantioselectivity and high activity towards 1-(3',4'-methylenedioxyphenyl)ethyl acetate.

Bacillus amyloliquefaciens esterase (BAE) was applied to produce (R)-1-(3',4'-methylenedioxyphenyl)ethanol, a chiral drug intermediate. In this study, we improved the enantioselectivity of BAE by protein engineering instead of process engineering as used in our previous work. Saturation mutagenesis was carried out on eight positions of BAE based on structure modeling and substrate docking. A double substituted variant V10 (K358D/A396C) showed an excellent enantioselectivity without decreasing the activity. The functions of these two mutations (K358D and A396C) were investigated, revealing a synergic effect on the BAE enantioselectivity. Using the variant V10, enantiopure (R)-1-(3',4'-methylenedioxyphenyl)ethanol could be readily prepared in >97% ee, affording a high space-time yield (123gL(-1) day(-1)) and a high ratio of substrate/catalyst (40gg(-1)) in 1-L reaction.

Parametric study of copper electrowinning using a pulsed-bed electrode reactor

BACKGROUND The pulsed bed electrode (PBE) has been used successfully for copper electrodeposition from highly concentrated acidic electrolytes. Advantages of this electrode include high space-time yield (Y) and simple operation and maintenance. In this work, the effects of operational conditions were investigated in an attempt to achieve current efficiencies (CE) higher than 76.7%, which was the maximum value obtained in a previous study. RESULTS The results showed that use of a high current density and low acid concentration provided the best operational conditions for maximizing CE and Y, and minimizing the energy consumption (EC). Nonetheless, the highest current density was limited to 3000 A cm-2 and the lowest acid concentration was limited to 110 g L-1, due to limitations such as metal dissolution, dendrite growth, and short circuiting. The highest CE achieved was 77.7%, using 2838 A m-2. According to a statistical model, the maximum CE value that could be achieved is 82.4%, with application of 3000 A cm-2. This suggests that further improvement of CE would lead to values of EC lower than those found in electrowinning plants. CONCLUSIONS Electrowinning using a pulsed-bed electrode is an excellent method for copper production, but additional improvements are required to increase CE. © 2014 Society of Chemical Industry

Efficient catalytic oxidation of HCl to recycle Cl2 over the CuO–CeO2 composite oxide supported on Y type zeolite

Abstract The CuO–CeO2 composite oxides supported on Y-zeolite were prepared by means of wet-impregnation method. The derived catalysts exhibited excellent activities and high stabilities for gas-phase HCl catalytic oxidation to Cl2. 90% conversion of HCl can be accomplished at a reaction temperature as low as 390 °C. Comparing with the results reported in literature, the CuO(12)–CeO2(13)/Y catalyst developed in the current study showed exceptionally high space time yield for Cl2 (62.7 mmol gcat−1 h−1 at 410 °C). A correlation between the characterization results and the activities of CuO–CeO2/Y suggested that higher content of well dispersed CuO species and intensive CuO–CeO2 association (the formed CuxCe1−xO2−y and surface oxygen spillover) are critical to determine high activity.

Enantioselective, continuous (R)- and (S)-2-butanol synthesis: Achieving high space-time yields with recombinant E. coli cells in a micro-aqueous, solvent-free reaction system

The stereoselective production of (R)- or (S)-2-butanol is highly challenging. A potent synthesis strategy is the biocatalytic asymmetric reduction of 2-butanone applying alcohol dehydrogenases. However, due to a time-dependent racemisation process, high stereoselectivity is only obtained at incomplete conversion after short reaction times. Here, we present a solution to this problem: by using a continuous process, high biocatalytic selectivity can be achieved while racemisation is suppressed successfully.Furthermore, high conversion was achieved by applying recombinant, lyophilised E. coli cells hosting Lactobacillus brevis alcohol dehydrogenase in a micro-aqueous solvent-free continuous reaction system. The optimisation of residence time (τ) and 2-butanone concentration boosted both conversion (>99%) and enantiomeric excess (ee) of (R)-2-butanol (>96%). When a residence time of only τ=3.1 min was applied, productivity was extraordinary with a space-time yield of 2278±29g/(L×d), thus exceeding the highest values reported to date by a factor of more than eight. The use of E. coli cells overexpressing an ADH of complementary stereoselectivity yielded a synthesis strategy for (S)-2-butanol with an excellent ee (>98%). Although conversion was only moderate (up to 46%), excellent space-time yields of up to 461g/(L×d) were achieved. The investigated concept represents a synthesis strategy that can also be applied to other biocatalytic processes where racemisation poses a challenge.

Versatile, high quality and scalable continuous flow production of metal-organic frameworks.

Further deployment of Metal-Organic Frameworks in applied settings requires their ready preparation at scale. Expansion of typical batch processes can lead to unsuccessful or low quality synthesis for some systems. Here we report how continuous flow chemistry can be adapted as a versatile route to a range of MOFs, by emulating conditions of lab-scale batch synthesis. This delivers ready synthesis of three different MOFs, with surface areas that closely match theoretical maxima, with production rates of 60 g/h at extremely high space-time yields.