Reactor capillary-flow microreactor

Catalytic runs were carried out at atmospheric pressure in a quartz-made fixed-bed flow microreactor (10 mm i d.). All the stainless-steel equipment devices had been passivated by hot HNO3 treatment before the assembly. The catalyst was activated in situ (6 h at 773 K under COj-free air flow). 4-Methylpentan-2-ol was fed in with an N2 stream (partial pressure, Po.aicohoi = 19.3 kPa time factor, W/F = 0.54 gcat-h/gakohoi)- On-line capillary GC analysis conditions were Petrocol DH 50.2 column, oven temperature between 313 and 473 K, heating rate 5 K/min. Products identification was confirmed by GC-MS. For each catalyst a run in which several reactor temperatures were checked was carried out, in order to study the influence of the thermal history of the sample on its catalytic behaviour and to reach an appropriate conversion level (ca. 50%) at which the selectivities values of the different catalysts can be compared. Then, a new run with a fresh portion of the same sample was started at the desired temperature and carried out isothermally for 80 h. Further runs, where both the flow rate and the catalyst amount were considerably changed, while keeping the same W/F value, were also carried out no significant differences in conversion were observed, which rules out the occurrence of external diffusion limitations. 

Power input, a decisive parameter for benchmarking technical reactors, has been investigated using the experimental pressure drop and compared with conventional contactor as shown in Table 15.5. The comparison reveals that the liquid-liquid slug flow microreactor requires much less power than the alternatives to provide large interfacial area - as high as a = 5000 m m in a 0.5 mm capillary microreactor, which is way above the values in a mechanically agitated reactor (a 500 m m ). 

The reaction system consisted of a flow stainless steel microreactor operated at 5 MPa and 523-623 K. Hydrogen and carbon monoxide were supplied to the reactor through mass flow controllers (Brooks). Products were sampled through heated lines into an on-line gas chromatograph equipped with TCD and FID detectors, with a Porapak Q + R column for Ci products and a Tenax column for hydrocarbons (C,-C13) or alcohols (Cj-Cfi), respectively. Reaction products were identified with a gas chromatograph-mass spectrometer (Hewlett-Packard Model 5971), using a 60 m DB-1 capillary column (J W Scientific). 

The capillary plasma reactor consists of a Pyrex glass body and mounted electrodes which are not in direct contact with the gas flow in order to eliminate the influence of the cathode and anode region on CO2 decomposition. Analysis of downscaling effects on the plasma chemistry and discharge characteristics showed that the carbon dioxide conversion rate is mainly determined by electron impact dissociation and gas-phase reverse reactions in the capillary microreactor. The extremely high CO2 conversion rate was attributed to an increased current density rather than to surface reactions or an increased electric field. 

Alkylation of isobutane with 1-butene was carried out in a fixed bed down flow stainless steel tubular microreactor. The experiments were carried out in the gas phase at 1 atm total pressure, isobutane/l-butene molar ratio of 14 and 1-butene space velocity 1.0 h". Premixed isobutane and 1-butene (>99% purity, Matheson) was fed from a gas cylinder. A high paraffin to olefin ratio was choosen to reduce the chance of olefin dimerization. The catalysts (300 mg, 60-80 pm particle size) were activated in the reactor by calcining in air at 450°C for 4 hours. Air flow was then replaced by nitrogen and the catalyst temperature was lowered to the desired reaction temperature. The feed gas and the products were analyzed by a on-line gas chromatograph equipped with a CP-Sil PONA capillary column (length 50 m, film thickness 0.25 pm). 

The catalytic experiments were performed in a continuous flow tubular microreactor. The catalyst bed consisted of 0.8 cm of 0.3-0.5 mm pellets, prepared by compressing of the NH -T zeolite powder into flakes, crushing and sieving. The zeolite was activated in the reactor by deammoniation at 673 K. The vapors of the acids were diluted with helium. The reaction conditions are further specified in Table 1. The reaction products were analysed on-line with GC, using a capillary fused silica column, coated with CP Sil5 (Chrompack) and F.l.D. detector. CO2 and H2O were not analysed. 

Regular flow patterns are provided by the segmented flow in a single capillary or in multi-channel microreactors. Miniaturized packed-bed microreactors follow the paths of classical engineering by enabling tridde-bed or packed bubble column operation. M ost of the microstructured multiphase reactors are at the research stage. Due to the small reaction volumes th will find their appHcation mainly in small-scale production in the fine chemical and pharmaceutical industries. 

Sulfonations are a further important type of electrophilic substitution reaction. However, only very few examples can be found in the literature describing the use of microstructured reactors for the strongly exothermic liquid-phase sulfonation of aromatics (sulfonation of toluene wdth gaseous SO3 was described by Jaehnisch et al. [34]). Burns and Ramshaw [25, 35] claimed that their concept of performing liquid/liquid nitration reactions in a slug-flow capillary-microreactor can be also... 

Both reactor types R3 and R4 use the segmented flow (Taylor) principle. They are divided into two categories R3 has very small channels (<1 mm) and R4 are monolith reactors (honeycomb), well developed on the laboratory scale with at least one example of industrial application. Category R3 includes single-channel and multi-ple-channel reactors [10], etched in silicon [10] or glass [10,11], with wall-coated or immobilized catalysts in the case of gas-liquid-solid additions [12], and capillary microreactors for gas-liquid-liquid systems [13]. 

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