A novel structured bioreactor: Development of a monolithic stirrer reactor with immobilized lipase

Cordierite monoliths were functionalized with polyethylenimine (PEI) and with different types of carbon, consisting of carbonized sucrose, carbonized ployfurfurryl alcohol, or carbon nanofibers, in order to create adsorption sites for a lipase from Candida antarctica. The prepared supports were compared in terms of immobilization capacity, activity, and stability. The supports with a carbon nanofiber coating displayed the highest enzyme adsorption capacity. The biocatalysts were assayed in the acylation of 1-butanol with vinyl acetate in toluene, yielding butanyl acetate and acetaldehyde. For catalyst performance testing a novel reactor type was employed, the monolithic stirrer reactor, in which monolithic structures are applied as stirrer blades. No profound effect of stirrer rate on the reaction rate was observed, implicating the absence of external mass transfer limitations. For comparison, free enzyme and a commercial (particulate) immobilized lipase were also included in the study. Compared to the free enzyme, the immobilized lipase shows a significantly lower activity. Increased stability, easy catalyst separation and the possibility to reuse the enzyme in immobilized form can overcome this difference. The commercial immobilized lipase initially has a significantly higher activity than the monolithic biocatalysts, but deactivates relatively fast. For the monolithic biocatalysts, no deactivation was observed; the prepared catalysts were stable for several weeks.     

A novel particle/monolithic two-stage catalyst bed reactor and their catalytic performance for oxidative coupling of methane

A novel two-stage catalyst bed reactor was constructed comprising of the 5%Na₂WO₄-2%Mn/SiO₂ particle catalyst and the 5%Na₃PO₄-2%Mn/SiO₂/cordierite monolithic catalyst. The reaction performance of the oxidative coupling of methane (OCM) in the two-stage bed reactor system was evaluated. The effects of the bed height and operation mode, as well as the reaction parameters such as reaction temperature, CH₄/O₂ ratio and flowrate of feed gas on the catalytic performance were investigated. The results indicated that the two-stage bed reactor system exhibited a good performance for the OCM reaction when the feed gases were firstly passed through the particle catalyst bed and then to the monolithic catalyst bed. The CH₄ conversion of 32.6% and C₂ selectivity of 67.5% could be obtained with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm in the two-stage bed reactor. Both of the CH₄ conversion and C₂ selectivity have been increased by 4.8% and 2.5%, respectively, as compared with the 5%Na₂WO₄-2%Mn/SiO₂ particle catalyst in a single-bed reactor and by 7.7% and 16.1%, respectively, as compared with the 5%Na₃PO₄-2%Mn/SiO₂/cordierite monolithic catalyst in a single-bed reactor. The catalytic performance of the OCM in the two-stage bed reactor system has been remarkably improved. The TPR results indicate the high temperature reduction oxygen species in the monolithic catalyst might be favorable to the formation of C₂ products.     

Numerical simulation of fixed bed reactor for oxidative coupling of methane over monolithic catalyst

A three-dimensional geometric modelwas set up for the oxidative coupling of methane (OCM) fixed bed reactor loaded with Na₃PO₄-Mn/SiO₂/cordierite monolithic catalyst, and an improved Stansch kinetic model was established to calculate the OCMreactions using the computational fluid dynamicsmethod and Fluent software. The simulation conditions were completely the same with the experimental conditions that the volume velocity of the reactant is 80 ml·min^-1 under standard state, the CH₄/O₂ ratio is 3 and the temperature and pressure is 800 ℃ and 1 atm, respectively. The contour of the characteristic parameters in the catalyst bed was analyzed, such as the species mass fractions, temperature, the heat flux on side wall surface, pressure, fluid density and velocity. The results showed that the calculated valuesmatchedwell with the experimental values on the conversion of CH₄ and the selectivity of products (C₂H₆, C₂H₄, CO,CO₂ and H₂) in the reactor outlet with an error range of ±4%. The mass fractions of CH₄ and O₂ decreased from 0.600 and 0.400 at the catalyst bed inlet to 0.445 and 0.120 at the outlet, where the mass fractions of C₂H₆, C₂H₄, CO and CO₂ were 0.0245, 0.0460, 0.0537 and 0.116, respectively. Due to the existence of laminar boundary layer, the mass fraction contours of each species bent upwards in the vicinity of the boundary layer. The volume of OCM reaction was changing with the proceeding of reaction, and the total moles of products were greater than reactants. The flow field in the catalyst bed maintained constant temperature and pressure. The fluid density decreased gradually from 2.28 kg·m^-3 at the inlet of the catalyst bed to 2.18 kg·m^-3 at the outlet of the catalyst bed, while the average velocity magnitude increased from 0.108 m·s^-1 to 0.120 m·s^-1.     

In situ MRI of the structure and function of multiphase catalytic reactors

NMR imaging (MRI) was used to study the distribution of the liquid phase in an operating trickle bed reactor using hydrogenation of -methylstyrene or n-octene-1 as representative examples. In a single pellet reactor, the existence of oscillating regimes under unchanged external conditions was shown. The experiments with packed beds have demonstrated the non-uniform distribution of the liquid phase over the bed, the presence of partially liquid-filled or completely dry catalyst particles in the operating reactor, and the existence of liquid phase transport between liquid-filled and dry catalyst particles. Detection of spatially resolved NMR spectra was used to characterize chemical conversion variations within the operating reactor. Preliminary MRI results for an operating monolithic reactor were obtained. It was found that MRI can be used to directly image solid materials using NMR signal detection of nuclei other than ¹H. In particular, imaging of alumina using ²⁷Al NMR signal appears highly promising for the development of novel MRI applications in chemical engineering and catalysis, including spatially resolved NMR thermometry.     

Application of a carbon membrane reactor for dehydrogenation reactions

This research tests a membrane reactor, equipped with a molecular-sieve carbon membrane, using isobutane dehydrogenation on a chromia alumina catalyst as a model reaction. Most pores of the carbon membrane employed are 6- in size and previous independent transport studies show that the permeability ratio of hydrogen to isobutene is larger than 100. These features make the membrane an excellent highly selective low-cost candidate for application in a membrane reactor. The novelty of this study is in the proposed application at relatively high temperatures (450°C and 500°C); only a few studies have tested carbon membrane reactors.Two types of operation modes were studied, using either nitrogen as a sweeping gas in counter current flow or using vacuum as a driving force for membrane transport. As expected, higher conversions were achieved with decreasing feed flow rate. The conversion achieved in the counter-current flow operation method was higher than in all other modes achieving a maximum of 85% at 500°C. While this result is much higher than in the corresponding PFR, the obtained improvement is a result of nitrogen transport and dilution. The conversions obtained in the vacuum mode show modest gains above the ones received in the PFR (40% vs. 30% at 500°C). These results were compared with simulations that used the experimentally determined transport parameters.     

A porous structured reactor for hydrogenation reactions

A novel combination of catalyst carrier and reactor design was developed for intensified production of vitamin intermediates. The so called Design Porous Structured Reactor (DPSR) is a laser sintered porous 3D-structure that can be tailored to the desired reaction properties such as fluid conditions or heat removal and can also act simultaneously as catalyst support.The selective hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) under solvent-free conditions was chosen as the reaction to evaluate the potential of DPSRs in comparison to conventional batch reactors. DPSR experiments were performed at varying temperatures and liquid flow rates.DPSRs exceeded batch performance in terms of selectivity, yield and turnover frequency in the analyzed process parameter range. However, DPSRs showed some mass transfer effects. Selectivities and yields increased with higher liquid flow rate due to reduced system pressures and sharper residence time distributions.Overall mass transfer coefficients for DPSRs were determined based on an isothermal non-ideal plug flow model applying heterogeneous Langmuir–Hinshelwood kinetics to account for the chemical conversion. The model showed sufficient accuracy to describe the occurring mass transfer processes.DPSRs were found to be viable alternative for batch reactors, demonstrating the potential for process intensification with an inherent potential for further improvement.     

加氢反应器损伤及检验技术探讨

介绍了锻焊结构热壁加氢反应器在制造和高温、高压、临氢工况运行过程中在21／4 Cr-IMo锻钢基层和奥氏体不锈钢堆焊层容易发生的开裂及材质脆化等损伤问题,探讨了裂纹等缺陷探伤和材质脆化监控技术。     

Natural gas conversion to liquid fuels in a zone reactor

A process for conversion of natural gas to liquid fuels is described. The process can be conducted in a “zone reactor” in which oxygen or air is first contacted with solid metal bromide, producing bromine and metal oxide. The bromine passes into a second zone, in which it reacts with natural gas, producing alkyl bromides and hydrogen bromide. The products of the second zone pass into a third zone, in which they react with metal oxide, producing metal bromide and liquid product. At the end of the cycle the oxygen feed and product streams are switched and the flow reversed. The advantages of the process including safety and capital cost reduction are presented and results discussed.     

Effect of gas evolution on mixing and conversion in a flow-through electrochemical reactor

Flow-through electrolytic reactors (FTER) emplaced below the subsurface may be used to control the migration of groundwater contamination away from source zones. During prior studies with FTERs, water electrolysis and associated gas generation have occurred concurrently with contaminant degradation. Gas evolution-induced mixing within the electrode assembly has the potential to impact system performance. A mathematical model of the system was developed to capture the impact of mixing on transport processes in the system. Corresponding transient and steady-state tracer experiments using ferricyanide as a model contaminant were conducted to quantify mixing-dependent parameters and verify modeling results. Over a range of relevant groundwater flowrates, Peclet numbers were between 0.1 and 10, indicating that mixing was a important process under low-flow conditions. Comparison of experiments and model calculations demonstrated that incorporating gas evolution into the model was necessary for accurate performance prediction. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Effect of washcoat modification with metal oxides on the activity of a monolithic Pd-based catalyst for methane combustion

The deposition of Ni, Co, Ce or Fe oxides onto the washcoat surface in the 0.5%Pd/Al₂O₃ catalyst enhances conversion of CH₄. Catalytic activity of the Pd-catalysts containing cobalt oxide depends on the incorporated amount of cobalt oxide and the method of incorporation. The highest activities were those of the 0.5%Pd/0.3%Co/Al₂O₃ and 1%Pd/0.3%Co/Al₂O₃ catalysts (cobalt oxide deposited onto the surface of Al₂O₃) and the 0.5%Pd/5%Co₃O₄–Al₂O₃ catalyst (mixed washcoat). Total SSA, Pd dispersion and Pd crystallite size in the x%Pd/y%Co/Al₂O₃ catalysts depend on the incorporated amount of PdO and cobalt oxide. Pd dispersion in the 1%Pd/Al₂O₃ catalyst increases from 4% to 20% upon deposition of 14 wt.% Co₃O₄ (by mass Al₂O₃) onto the Al₂O₃ surface (1%Pd/0.3%Co/Al₂O₃). This increase in Pd dispersion influence the increase in the activity of the 1%Pd/Al₂O₃ catalyst. On the surface of the 0.5%Pd/5%Co₃O₄–Al₂O₃ catalyst Pd occurs mainly in the form of PdO and displays considerable mobility under conditions of temperature variations—cyclically undergoing reduction and oxidation. At 500 °C, in vacuo, the reduction was irreversible and parallelled by the agglomeration of metallic Pd crystallites. At room temperature, cobalt occurred on the catalyst surface in the form of Co⁺² ions (CoAl₂O₄) and was reduced to Co⁰ at 500 °C (in vacuo). Up to 500 °C, the reduction of Co was reversible.     

Trickle bed reactor diluted with fine particles and coiled tubular flow-type reactor for kinetic measurements without external effects

Gas and liquid velocities in laboratory scale trickle bed reactors are one or two orders of magnitude lower than those in commercial reactors. Then, the kinetic data may include the external effects. This shortcoming of laboratory scale trickle bed reactor can be resolved by diluting the catalyst bed with fine inert particles. The catalyst bed dilution increases dynamic liquid holdup, pressure drop, gas–liquid mass transfer coefficient. Hydrogenation of 2-phenylpropene on Pd/Al₂O₃ was performed with the trickle bed reactor diluted with fine inert particles and the coiled tubular flow-type reactor to compare the kinetics with that of the basket type batch reactor. The trickle bed reactor diluted with fine inert particles is suitable to obtain the reaction rate without external effects even if the liquid velocity is low. The coiled tubular flow-type reactor should be used at high gas velocities.     

Investigation of a rotating disc reactor for acetone stripping and asymmetric transfer hydrogenation: Modelling and experiments

Asymmetric transfer hydrogenation of acetophenone with isopropanol as hydrogen donor in the presence of a homogeneous catalyst was investigated in a rotating disc reactor. Initially, acetone stripping from binary mixtures acetone-isopropanol with nitrogen as inert gas was studied, since its removal is a key issue in improving reaction performance. The reactor consisted of a stainless steel disc mounted on a horizontal shaft, accommodated in a cylindrical shell. The disc was partially immersed in the liquid phase. Its rotation generated a thin liquid film on its upper part, which could be brought in contact with a gas phase used for stripping. A mathematical model was formulated to simulate the reactor and showed good agreement with experimental data for acetone stripping. It was observed that the efficiency of acetone removal from the liquid phase increased with the gas flowrate per initial liquid volume ratio. The effect of disk rotation was found to be small when the stripping gas was introduced in the liquid bulk. The reactor model agreed well with experimental data of the asymmetric transfer hydrogenation. An advantage of the rotating disk reactor is that the hydrodynamics of the phases can be decoupled and the gas flowrate can be increased without constraints in the liquid phase, unlike conventional agitated reactors that are limited by flooding. Simulations using high stripping gas flowrate per initial liquid volume, unachievable in stirred reactors, showed significant reduction of the residence time required to achieve >99% conversion.     

Catalyst preparation and deactivation issues for nitrobenzene hydrogenation in a microstructured falling film reactor

Hydrogenation of nitrobenzene to aniline in ethanol was performed continuously in a microstructured falling film reactor at 60 °C, 1–4 bar hydrogen pressure and residence time 9–17 s. Palladium catalyst was deposited as films or particles via sputtering, UV-decomposition of palladium acetate, incipient wetness or impregnation. Deactivation was observed and was particularly pronounced for the sputtered and UV-decomposed catalysts. Catalysts prepared through incipient wetness or impregnation were more stable and activity could be recovered by oxidation at 130 °C. The main causes of deactivation were determined to be deposition of organic compounds and palladium loss.     

Membrane‐dispersion reactor in homogeneous liquid process

For homogeneous liquid processes, mixing at molecular scale may influence selectivity, yield and quality of final products. In a membrane‐dispersion reactor, microporous membranes are employed as dispersion media for controlled feeding of one solution into another one to intensify micromixing. The reactor has been widely used in the preparation of nanoparticles, preparation of nanocapsules and liposomes, synthesis of polymers, parallel and consecutive reactions to improve nanoparticles quality, molecular weight distribution of polymer, or selectivity of complex reactions. This paper reviewed the progress of the membrane‐dispersion reactor in homogeneous liquid processing including features, applications, advantages and limits. © 2012 Society of Chemical Industry .     

Tailor-structured skeletal Pt catalysts employed in a monolithic electropromoted reactor

The performance of a monolithic electropromoted reactor was investigated under high gas flow rates, for the oxidation of ethylene utilizing thin (40 nm) tailor-structured highly porous skeletal Pt catalyst-electrodes coated on Y₂O₃-stabilized-ZrO₂ (YSZ). Electrochemical enhancement was observed at gas flow rates as high as 25 L min⁻¹ and mean gas residence times as low as 0.15 s. This is a promising step for the practical utilization of the electrochemical promotion of catalysis. An interesting feature of the skeletal Pt catalyst-electrodes is the appearance of a sharp rate maximum upon anodic current interruption which appears to be related to their dendritic structure and enhanced capacity for promoter storage.     

Mathematical modeling of the partial hydrogenation of vegetable oil in a monolithic stirrer reactor

Experimental and theoretical studies on the partial hydrogenation of vegetable oil in a monolithic stirrer reactor are reported. A complete mathematical model of the reactor was developed, including hydrogenation and isomerization kinetics, catalyst deactivation, external gas–liquid and liquid–solid as well as internal mass transfer. The experimental studies were carried out in a Pd/Al₂O₃/Al monolithic stirrer reactor, at a wide range of temperatures (353–373 K), pressures (414–552 kPa), and catalyst loadings (0.00084–0.00527 kg_Pd,exp m^?3). Based on this model, simulated data can be used to evaluate the catalyst (Pd/Al₂O₃/Al) and the hydrogenation process in consecutive catalytic tests under different operating conditions. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3524–3533, 2014     

Periodically operated trickle-bed reactor for EAQs hydrogenation: Experiments and modeling

The influence of periodic operation on a consecutive reaction, the hydrogenation of 2-ethylanthraquinones (EAQs) over Pd/Al₂O₃, on a laboratory-scale trickle-bed reactor (TBR) was studied. The effects of operating parameters including cycle period, split, pressure, temperature, and time-average flow rate on the performance were experimentally examined in comparison with the steady-state operation. The results showed that under the interested operating conditions the conversion and the selectivity improved by 3-21% and 1-12%, respectively. A dynamic model consisting of a set of partial differential equations (PDEs) was developed to simulate the periodic operation of TBR for EAQs hydrogenation. The PDEs were converted into a set of ordinary differential equations (ODEs) using the method of lines (MOL) and then numerically solved by the semi-implicit Runge-Kutta method. The developed model was verified by simulating the effect of cycle period and split on the conversion and the selectivity enhancement and compared with the experimental results. It was found that the model was reliable and satisfactory when the cycle period was less than 200 s.     

Recent development of supported monometallic gold as heterogeneous catalyst for selective liquid phase hydrogenation reactions

The great potential of gold catalysts for chemical conversions in both industrial and environmental concerns has attracted increasing interest in many fields of research. Gold nanoparticles supported b...     

负载金作为非均相催化剂催化选择性液相加氢反应的研究进展(英文)

The great potential of gold catalysts for chemical conversions in both industrial and environmental concerns has attracted increasing interest in many fields of research. Gold nanoparticles supported by metal oxides with high surface area have been recognized as highly efficient and effective green heterogeneous catalyst even at room temperature under normal reaction conditions, in gas and liquid phase reactions. In the present review, we dis-cuss the recent development of heterogeneous, supported monometal ic gold catalysts for organic transforma-tions emphasizing mainly liquid phase hydrogenation reactions. Discussions on the catalytic synthesis procedures and the promoting effect of other noble metals are omitted since they are already worked out. Appli-cations of heterogeneous, supported monometal ic catalysts for chemoselective hydrogenations in liquid phase are studied including potential articles during the period 2000–2013.