Catalytic hydrolysis reactor

Catalytic hydrolysis reactor—Hydrolyzes the syngas COS to CO2 and HjS, and HCN to NHj and CO for ensuring that enviromnental emission limits are met in the syngas. 

Figure 6.25(a) shows a novel process for the continuous production of fuels from waste plastics. The proposed process consists primarily of three reactors. A mixture of waste plastics is fed into a pyrolytic reactor with heat-medium-particles stirred by a helical impeller (Figure 6.25(b)), where melted plastics are hydrothermally decomposed with steam and the random scission of C-C bonds. The produced mixture of a heavy oil containing wax and sublimate material is carried by steam stream to the next reactor, which is filled with an FeOOH catalyst (i.e. a catalytic hydrolysis reactor). The gaseous... 

Table 6.9 Product yield at the outlet of the catalytic hydrolysis reactor and the catalytic cracking reactor in the pilot-scale plant...

This step is necessary due to MDEA s inability to absorb COS that was formed in the gasifier. In a conventional hydrolysis process, water-saturated syngas is passed through a fixed-bed catalytic hydrolysis reactor where 85%-95% of the COS is converted to H2S (COS at l 10ppm). Once COS is converted to H2S, it is readily absorbed by the MDEA process. 

Catalytic membrane reactors are not yet commercial. In fact, this is not surprising. When catalysis is coupled with separation in one vessel, compared to separate pieces of equipment, degrees of freedom are lost. The MECR is in that respect more promising for the short term. Examples are the dehydrogenation of alkanes in order to shift the equilibrium and the methane steam reforming for hydrogen production (29,30). An enzyme-based example is the hydrolysis of fats described in the following. 

In the field of organic synthesis, it was reported that the catalytic hydrolysis of umbelliferone esters (7-acetoxycoumarin) to 7-hydroxycoumarinby porcine pancreatic lipase covalently immobilized on microchannel reactors almost completed within 1 min, to be compared with 4 min in a normal batch reaction [86]. The same group demonstrated an improvement in the yield of trypsinmicrochannel reactor with a lower enzyme concentration but a 20-fold higher reaction rate than in a batch reactor [87]. 

Cyanopyridines are usually manufactured from the corresponding picoline by catalytic, vapor-phase ammoxidation (eq. 7) in a fixed- or fluid-bed reactor (28). 3-Cyanopyridine (25) is the most important nitrile, as it undergoes partial or complete hydrolysis under basic conditions to give niacinamide... 

Enzymes are biocatalysts constructed of a folded chain of amino acids. They may be used under mild conditions for specific and selective reactions. While many enzymes have been found to be catalytically active in both aqueous and organic solutions, it was not until quite recently that enzymes were used to catalyze reactions in carbon dioxide when Randolph et al. (1985) performed the enzyme-catalyzed hydrolysis of disodium p-nitrophenol using alkaline phosphatase and Hammond et al. (1985) used polyphenol oxidase to catalyze the oxidation of p-cresol and p-chlorophenol. Since that time, more than 80 papers have been published concerning reactions in this medium. Enzymes can be 10-15 times more active in carbon dioxide than in organic solvents (Mori and Okahata, 1998). Reactions include hydrolysis, esterification, transesterification, and oxidation. Reactor configurations for these reactions were batch, semibatch, and continuous. 

One process that may offer benefits of acid catalysis without the drawbacks of H2S04 is the use of carbonic acid. The pH of carbonic acid is determined by the partial pressure of C02 in contact with water, and thus it can be neutralized by releasing the reactor pressure. Carbonic acid is relatively mild and hence does not offer the same hydrolytic capability of H2S04. However, van Walsum (25) has demonstrated that at temperatures on the order of 200°C, carbonic acid does exhibit a catalytic effect on the hydrolysis of xylan. Van Walsum (25) observed an enhanced release of xylose and low-degree-of-polymerization xylan oligomers compared to pretreatment... 

Activation of solid catalysts under well-specified conditions is a key step for obtaining the desired catalytic performance. It is particularly the case with zeolites, which are hygroscopic solids and for which the efficiency can be significantly reduced by the presence of water (e.g. change in the characteristics of the protonic acid sites, loss of reactant by hydrolysis). Polar organic molecules (even present in low amounts in the atmosphere of the chemical laboratories) can also be rapidly and strongly adsorbed over zeolites causing a decrease of their catalytic efficiency. Pretreatment of the zeolite in the reactor is preferable. This in situ pretreatment is easier to carry out in fixed bed than in batch reactors. 

Adsorption experiments The method developed for the analysis of carbonaceous compounds formed and trapped within the zeolite micropores during catalytic reactions1581 can be adapted for determining the occupancy of micropores by reactant, solvent and product molecules. However, this method cannot be used with compounds sensitive to hydrolysis, such as AA, because of the step of dissolution of the zeolite in a hydrofluoric acid solution necessary for the complete recovery of the organic molecules located within the zeolite micropores.[58] This method was used to determine the composition of the organic compounds retained within the micropores of three different zeolites [H-BEA (zeolite Beta), H-FAU (zeolite Y), and H-MFI (zeolite ZSM-5)] after contact in a stirred batch reactor at 393 K for 4 min of a solution containing 20 mmol of 2-methoxynaphthalene (2-MN), 4 mmol of l-acetyl-2-methoxynaphthalene (1-AMN) and 1 ml of solvent (sulfolane or nitrobenzene) with 500 mg of activated zeolite.[59 61] From the comparison of... 

Materials with acidic sites have to replace strong acids in the hydrolysis of MTBE and other fuel oxygenates, as using acids would cause strongly acidic effluents and corrosion. Catalytic materials used in MTBE remediation need to have the following properties insolubility in water and therefore easy separation of the catalyst from the treated water, chemical stabiUty, and feasibility for regeneration. Possible appHcations of these materials include PRBs as well as packed-bed reactors in pump-and-treat procedures. 

The heart of the Beavon process is a catalytic reactor which converts essentially all of the sulfur in the tail gas to hydrogen sulfide either by hydrogenation or hydrolysis. Hydrolysis reactions are typified by Reactions 2 and 3 ... 

The two previous examples dealt with gas phase catalytic reactions studied in a TS-PFR. Temperature scanning, however, is not limited to this type of reaction or reactor. It is a broadly applicable technique of experimentation, applicable to a variety of chemical reactions, in a variety of reactor types. It is rare, however, to find a reaction that can conveniently be carried out in a variety of reactors. One such reaction is the hydrolysis of acetic anhydride, a liquid phase reaction with particularly simple kinetics. This reaction can therefore be used to examine the consistency of data obtained from various reactors, as well as to provide an illustration of the application of the TSR technique to a homogeneous reaction in the liquid phase. 

A Fluidised Bed Reactor (FBR) was used for the study of the hydrolysis of aroma precursors of Muscat wine of Lunel (pH 3.8, 15 % alcohol). In this reactor the flow of substrate keeps the immobilized enzyme particles in a fluidised state. This continuous reactor is used in a recycle mode where the product stream is mixed with the incoming substrate stream. The use of the FBR permits to obtain a high catalytic surface area. For efficient operation, the particles should be of nearly uniform size, otherwise a non... 

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