Microflow reactor

The activity tests of the catalyst were carried out in a microflow reactor set-up in which all the high temperature parts are constructed of hastelloy-C and monel. The reactor effluent was analyzed by an on-line gas chromatograph with an Ultimetal Q column (75 m x 0.53 mm), a flame ionization detector, and a thermal conductivity detector. The composition of the feed to the reactor can be varied, besides the temperature, pressure, and space velocity. The influence of the recycle components CHCIF2 and methane was tested by adding these components to the feed. In total five stability experiments of over 1600 hours were performed. In each... 

In the cation flow method an organic cation is generated continuously by low temperature electrolysis using an electrochemical microflow reactor. The cation thus generated is immediately allowed to react with a carbon nucleophile in the flow system. This method, in principle, enables the manipulation of highly reactive organic cations. 

Scheme 11 The aminocarbonylation reaction performed in a microflow reactor [33] toluene, base...

Schmidt, K., Ehricht, R., Ellinger,T., McCaskill, J. S., A microflow reactor with components for mixing, separation and detection for biochemical experi-... 

Table 11 Summary of the reaction products generated via the deprotonation of styrene oxide 83 in a microflow reactor (RT = 24 s, —78 °C)...

As Scheme 59 illustrates, the reaction involves the hydrogen-lithium exchange of phenyl isonicotinamide 202, in the presence of H-BuLi 74/LiBr 203, followed by a reaction with ethyl-4-oxocyclohexanecarboxylate 204 to afford the target spiro lactone 201 as a mixture of cis/trans isomers. In the presence of any residual dilithiated intermediate 205, the spiro lactone 201 can undergo a second reaction to afford the by-product 206. Conducting the reaction in a microflow reactor, comprising of static mixers and... 

Kitamori and coworkers reported the use of a Ti02-modified microchannel chip reactor (TMC, Pyrex glass chip, having branched channels 770 pm wide and 3.5 pm deep) for photocatalytic redox-combined synthesis of L-pipecolinic acid from L-lysine (Scheme 4.31) [45], Although both batch and microflow systems gave comparable yield and enantiomeric excess of the product, the conversion rate was significantly higher for the microflow reactor than for the batch system. 

Table I lists the categories of laboratory reactors used for catalyst testing and catalytic process studies, viz., in the order of decreasing size pilot-plant, bench-scale and microflow reactors. Table II compares the feed requirements of some representative examples of these three classes for a typical case of oil hydroprocessing. The large effect of scale is evident whereas the pilot plant consumes monthly amounts of liquid and gas that require supply on a periodic basis by tank car and tube trailers, the microflow needs can be covered by a small drum or can and a few gas bottles. The size of the test reactor does not only have consequences for the logistics of supply, storage and disposal of feeds and products, but can also dictate the scale of preparation of special feedstocks and catalysts.

Fig. 2. Measured axial dispersion in a microflow reactor with flowing gas as a function of superficial velocity.

Table III. Measured Axial Dispersion in a Microflow Reactor with Gas Flow through an Undiluted Bed...

Figure 13B shows the calculated temperature differences for the same cases as considered before, but with catalyst beds diluted with silicon carbide to one third of the original catalyst concentration. It can be seen that the temperature differences are appreciably smaller than in the undiluted case (note the differences in temperature scale between Figures 13A and 13B). The dilution with good thermally conducting material is particularly effective at the low velocities in short beds because the convective contribution to the effective heat conductivity is then relatively small. It can be inferred that in microflow reactors (D = 1 cm L = 10 cm) and in bench-scale reactors (D = 2 cm L = 1 m) with diluted beds radial temperature differences are less than 1-2 °C for the considered cases, which is quite acceptable. 

Fig. 14A and B. Examples of measured temperature profiles along the central axis of microflow reactors used in catalyst testing for a vapor phase (A) and a trickle-flow process (B). 

Processes with Reactants in the Gas Phase. As discussed in the preceding parts, for such processes there is hardly a problem in catalyst testing on a scale as small as that of microreactors, even with undiluted beds of catalyst of actual size. Hence, in this case testing on a larger scale than microflow reactors will seldom be neccessary. 

The latter conclusion is supported by the data of Table VI, which demonstrate that testing in a bench-scale and microflow reactor gives almost identical results for light naphtha isomerization over undiluted catalyst of actual size. The absence of a noticable effect of bed length and gas velocity is in line with the assumption that in this case extraparticle mass transfer effects are relatively unimportant, as discussed earlier. 

Table VI. Comparison of Test Results on Light Naphtha Isomerization in Bench-scale and Microflow Reactors...

Table VII. Reproducibility of Catalyst Testing in Microflow Reactors for Isomerization of Light Naphtha...

Figure 20 presents some results of comparative tests on hydrodesulfurization of a heavy gasoil in a bench-scale and a microflow reactor over two catalysts, both diluted with small particles of silicon carbide. It can be inferred that results are the same irrespective of the reactor scale, the same difference in relative performance of the two catalysts being observed in both reactor types. 

Quantitative information on the reproducibility of tests with diluted catalyst beds in microflow reactors was obtained from a series of tests with a standard catalyst and feedstock carried out in the context of monitoring catalyst quality in commercial catalyst production. From the data listed in Table IX it can be inferred that a good reproducibility can be obtained provided due attention is given to experimental details of the testing procedure such as reactor filling, start up and control of reaction conditions. 

Fig. 20. Comparison of bench-scale and microflow reactors for hydrodesulfurization of a heavy gasoil over diluted catalyst beds.

Diluent in microflow test Silicon carbide, d = 0.05 mm. Feed Middle East heavy gasoil, 1.64 %w S.Operating conditions WHSV, WABT, hydrogen/oil ratio, partial pressures of hydrogen and hydrogen sulfide same in commercial and microflow reactor. 

Microflow reactors as shown in Figures 21 and 22 are now capable of generating most of the catalytic performance data for fixed-bed processes applied in the hydrocarbon process industry, a task that some 25 years ago had to be reserved for large pilot plants with catalyst volumes of 10 L or more which required tank farms and gas holders and even on-site production of hydrogen to enable their operation. 

Fig. 21. Picture of microflow reactors for testing catalysts for gas-phase processes, build in the eighties. The reactor units are equipped with on-line GLC analyzers.

Catalytic Activity Measurement. The reaction was carried out in a stainless steel microflow reactor. In each run, 2 g catalyst was placed in the reactor and heated to 520 °C under a nitrogen stream. The nitrogen stream was replaced by a light naphtha vapor fed by a micro plunger pump. The reaction was carried out at 520 °C, under various pressures and WHS Vs without any hydrogen addition. The products were analyzed periodically by gas chromatography. The properties of the light naphtha are shown in Table I. 

The reactions were carried out in a microflow reactor at 270 C, under the partial pressure of the reactant of 0.1 kg/cm G (nitrogen balance). 

Thiophene HDS was performed at 673 K in a microflow reactor with on-line gas chromatography (GC) analysis. The catalyst samples (200 mg) were pre-sulfided in situ using conditions described in the preparation section. The reaction mixture consisting of 4.0 mol% thiophene in H2 was fed through the reactor and was analyzed every 35 min (flow rate 50 ml min , 673 K, 1 bar). First order rate constants for thiophene conversion to hydrocarbons (Khds) and the consecutive hydrogenation of butene (knyo) were calculated as described elsewhere [8]. 

---