Channel process

Carbon Black. This is the principal reinforcing filler used in mbber. Carbon black is made by three processes the furnace process, the thermal process, and the channel process. Over 97% of black is made by the furnace process (see Carbon, carbon black). 

The oil-fiimace process, based on the partial combustion of Hquid aromatic residual hydrocarbons, was first introduced in the United States at the end of World War II. It rapidly displaced the then dominant channel (impingement) and gas-furnace processes because it gave improved yields and better product quahties. It was also independent of the geographical source of raw materials, a limitation on the channel process and other processes dependent on natural gas, making possible the worldwide location of manufacturing closer to the tire customers. Environmentally it favored elimination of particulate air pollution and was more versatile than all other competing processes. 

As examples of micro-channel process intensification and the respective equipment, in particular gas/liquid micro reactors and their application to toluene and various other fluorinations and also to carbon dioxide absorption can be mentioned [5]. Generally, reactions may be amenable to process intensification, when performed via high-temperature, high-pressure, and high-concentration routes and also when using aggressive reactants [5]. 

The increase in mass transfer by micro-channel processing is frequently cited in... 

Keeping in mind the controversial discussion on new physics in micro reactors [198], we certainly have to be at least as careful when introducing or claiming essentially novel chemical processes. A thorough scientific consideration is required for an exact definition and differentiation here that is beyond the scope of this book. So far, no deep-rooted scientific work has been published analyzing the origin of the novelty of chemistry under micro-channel processing conditions. 

The very promising results for ethylene oxide synthesis by micro-channel processing given above shll await industrial implementation. Selechvity needs to be further improved above 80%, as the costs for ethylene contribute 80% to the overall process costs ]4]. In addihon to the costs argument, the usual requirements for transfer from laboratory to industrial scale will face the micro reactor reliability, proper process control and much more. 

Later, much more detailed predictions of safe operation in micro reactors in the explosive regime with the example of the hydrogen/oxygen reaction could be given [9,82,117,118], It was predicted that micro-channel processing under given conditions can be considered as intrinsically safe. 

Similar aggressive reaction conditions characterize the hydrolysis of acid chlorides, in particular when using short-chain alkyl-substituted acid chlorides such as propionic acid chloride. This fast reaction serves well as a model reaction for micro channel processing, especially for IR monitoring owing to the strong changes in the carbonyl peak absorption by reaction [21]. 

OS 20] ]R 5] ]P 13] (adapted) Using more complex peptides such as N-f-Boc-L-lysine is also feasible by micro-channel processing [5]. Batch, 9% micro reactor, quantitative in 20 min. 

OS 29] [similar to R 12, details in [91[[ [P 21] On varying the residence time by changing the flow rate from 0.1-1 pi min for micro-channel processing at 50 °C, the yields decrease from 83 to 17%. No figures of residence times are given in [91]. 

The main driver was to develop a laboratory-scale micro-channel process and transfer it to the pilot-scale, aiming at industrial fine-chemical production [48, 108]. This included fast mixing, efficient heat transfer in context with a fast exothermic reaction, prevention offouling and scale-/numbering-up considerations. By this means, an industrial semi-batch process was transferred to continuous processing. 

Photocyanations rely on photoinduced electron transfer [29]. This was demonstrated by monitoring cyanation yields as a function of the droplet size for oil-in-water emulsions. Hence increase in interfacial area is one driver for micro-channel processing. Typically, fluid systems with large specific interfacial areas tend to be difficult to separate and solutions for more facile separation are desired. 

The above-mentioned research targets generally address the good mass and heat transfer properties achieved by micro channel processing, in particular referring to fast mixing and good heat transfer. 

OS 57] [R 6] [P 3 9/The conversion of the micro channel processing amounted typically to about 50-75%, depending on the nature of the cycloadduct and the residence time chosen [18],... 

OS 57] [R 6] [P 40] One of the first examples of parallel multi-reaction was performed in a Caliper chip [18], By 2 x 2 combinations of two aldehydes and two 1,3-diketones, four cycloadducts were generated simultaneously in one run on one chip (Figure 4.71). The conversions were comparable to those for the single runs, with one exception. Also, cross-contamination was observed. It ranged from a few percents to about 50%. It should be pointed out that despite these initial drawbacks the demonstration of multi-reaction feasibility is a further valuable step in micro channel processing. 

Pentene oxidation over TS-1 catalyst is a fast reaction and hence fulfils a basic requirement for being suited to micro-channel processing [30]. Thus, it can serve as a model reaction to demonstrate the benefits of micro chemical engineering, particularly for zeolite-catalyzed reactions. Apart from this, epoxidations are an important class of organic reactions, also of industrial importance. 

OS 63] [R 27] ]P 46] A 43% conversion was achieved by micro-channel processing, while both batch experiments and expectation from intrinsic kinetics indicated conversions close to 90% [117] 80% was achieved by micro-channel processing with an additional micro mixer (see the Section Setting micro mixing prior to reaction, below). 

One investigation referred to using a Crignard reaction for industrial purposes [134]. It served as model reaction meeting the relevant criteria highly exothermic, temperature sensitive, fast and difficult to handle in a stirred vessel. The reaction chosen had a reaction enthalpy of 300 kj mol and occurred in a time frame of about 10 s, as did most of the side reactions did. The avoidance of side reactions, i.e. an increase in selectivity, was the main motivation for the development of a micro-channel process. 

OS 68] [R 19] [P 50/The experiments on micro-channel processing followed a statistical design [134]. The dependence of the yield on temperature and on the ratio... 

Improved control over heat and mass transfer as well as residence time by micro-channel processing often allows one to increase the reaction temperature of cryogenic processes without losing selectivity. It often leads to improved selectivity. 

Reducing the processing time is a driver for micro channel processing of aldol reactions [15]. Using reactive reactants such silyl enol ethers, this can be accomplished. 

For methyl 4-formylbenzoate, the yield decreased from 70% (2 1) to 59% (1 1) [13]. For batch processing, the yield decreased from 60% (2 1) to 48% (1 1), i.e. the reductions were similar. In both cases, micro channel processing was superior. 

P 69] No details on the solvent used and concentrations are given in [127], as the process most likely is proprietary (Figure 4.96). Probably the process is solvent-free as obviously one of the reactants has also the function of dissolving the other. The temperature for micro-channel processing was set to 0 °C. The residence time between the pre-reactor and micro mixer was 1 s and between the micro mixer and quench 5 s, totalling 6 s. 

GL 1] [R 1] [R 3] [P la-d] For micro-channel processing, an analysis of the content of fluorine actually consumed as a function of the fluorine-to-toluene ratio was made [38]. The curves for two micro reactors and one laboratory bubble column do not show the same trend a decrease of converted fluorine with increasing ratio results for the falling-film micro reactor, whereas the micro and laboratory bubble columns show increasing performance. The two micro reactors use about 50-75% of all fluorine offered, whereas the laboratory tool has an efficiency of only 15%. 

GL 1[ [R 1[ [R 3[ [P la-dj On increasing the temperature for micro-channel processing, conversion for the direct fluorination rises, as expected [38]. For the falling film micro reactor, conversion is increased from 15 to 30% on going from -40 to -15 °C. The selectivity varies widely between 30 and 50% without a clear tendency for this temperature range. The origin of this fluctuation is not understood. 

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