Ethanol reactor residence time

The enzyme / -ethylphenol methylene hydroxylase (EPMH), which is very similar to PCMH, can also be obtained from a special Pseudomonas putida strain. This enzyme catalyzes the oxidation of /7-alkyphenols with alkyl chains from C2 to Cg to the optically active / -hydroxybenzylic alcohols. This enzyme was used in the same way as PCMH for continuous electroenzymatic oxidation of / -ethylphenol in the electrochemical enzyme membrane reactor with l,w-bisferrocenyl-PEG 20,000 (MW 20,000) as high-molecular-weight water-soluble mediator according to Fig. 25. During a 5-day experiment using a 16-mM concentration of / -ethylphenol, we obtained a turnover of the starting material of more than 90% to yield the (/ )- -(4 -hydroxyphenyl)ethanol with 93% optical purity and 99% enantiomeric excess (glc at a -CD-phase) at a residence time of 3 h. The (5 )-enan-tiomer was obtained by electroenzymatic oxidation using PCMH as production enzyme. 

Within the electrochemical enzyme membrane reactor, the formation of / -hydroxy-benzaldehyde from / -cresol reached a space-time yield of 4.44 mmol/L h = 11.8g/ g L d using 60 U of the enzyme PCMH. At a residence time of 3 h, the turnover ofp-cresol was 90 to 95%. For the formation of (/ )- -(4-hydroxyphenyl)ethanol from -ethyl-phenol using the electrochemical enzyme membrane reactor, the space-time yield was... 

Rh-Ce catalyst exhibited a high ethanol conversion over 95% and high selectivity to H2 and CO in a very short residence time of <10ms under autothermal condition. Increasing steam/carbon ratio increased the H2 yield due to the participation of WGS reaction. The POE and WGS reactions were also performed in a two-stage reactor. 

Yeong et al. [100,101] used a microstructured film reactor for the hydrogenation of nitrobenzene to give aniline in ethanol at a temperature of 60 °C, a H2 partial pressure of 0.1-0.4 MPa, and residence times of 9-17 s. Palladium catalysts were deposited as films or particles on a microstructured plate. Confocal microscopy was used to measure the liquid film thickness, which increased from 67 to 92 pm as flow rates were increased from 0.5 to 1.0 cm3 min-1. The value of kha characteristic of this system was estimated to be 3-8 s 1 at an interfacial surface area (per reactor volume) of 9000-15000 m2 m 3. Conversion was found to be affected by both liquid flow rate and H2 partial pressure, and the reactor operated between the kinetic and mass transfer-controlled regimes. 

Utilizing a similar approach to that demonstrated for solid-supported catalysts, Urge et al. [83] recently demonstrated the enantioselective acylation of racemic alcohols in a continuous flow packed-bed reactor (Scheme 6.37). Employing Candida antarctica lipase B (CaLB) (146) (0.40 g) and pumping a solution of rac-phenyl-l-ethanol (101) (10 mg ml ) in hexane-THF-vinyl acetate (147) (2 1 1) at a flow rate of 100 pi min-1 (at 25 °C), the authors found that the reactor reached a steady state after 30 min of operation. Under the aforementioned conditions, the (R)-acetate 148 was obtained in 50% conversion and 99.2% ee and the residual (S)-alcohol 149 in 98.9% ee with a residence time of 8.2 min. Analogous results were obtained in batch, but a reaction time of 24 h was required in order to obtain 50% conversion of 101 to 148. 

Table 4 shows the calculated values of conversion, productivity, and yield for each residence time tested the productivity for the maximum conversion reached in the continuous SSF (97%) was 5.9 g/l/h, with yield of 81%, for a residence time of 11.1 h, calculated using the average values of the four determined TRS and ethanol concentrations for this residence time. In the discontinuous SSF reactor, for the same enzyme and yeast concentrations, the results were total conversion of TRS in glucose in 6 h and 99.8% of glucose/ethanol conversion in 9 h, with high concentrations of free glucose in the medium. 

Table 4 Ethanol concentration (Et), substrate conversion (Xs), ethanol productivity (Prd), and ethanol yield (%) for several residence time in the reactor (ff).

These effects were studied running two new continuous assays. In continuous run 2, the system was operated with a total volume of 314 ml (110, 104, and 100 ml, for reactors 1, 2, and 3, respectively), keeping constant the feed flow rate, 55 ml/h, with and without recycle in the first reactor. Only one recycle flow rate was tested, 67.2 ml/h. In continuous run 3, only the first reactor was operated, changing the feed and recycle flow rates. Table 5 shows operational conditions and respective average values of ethanol, TRS, and glucose concentrations obtained for related steady states, in the two new tests. Figure 4 shows ethanol production vs residence time for operational conditions operated without recycle, with superficial velocities up to 3.1 x 10 cm/s and above 3.7x lO" cm/s. 

The second step in the direct ethanol process is that of enzyme production. The Gulf process utilizes a mutant strain of Trichoderma reesei, grown continuously to produce a complete cellulase system. The residence time is 48 hours. Enzyme production begins on a spore plate with subsequent scale-up to the enzyme production vessel size to be used. Our pilot plant facility has 300-gal enzyme reactors. 

A glass MSR was used to perform the dehydration of ethanol. The microchan-nel of size 200 X 80 pm deep X 30 mm (in a Z shaped configuration) was produced by photohthographic etching [71]. A sulfated zirconia catalyst immobihzed over the surface of the top cover block. In addition, a NiCr wire was immobilized in the reactor cover as a heating device. At a reaction temperature of 155 °C and a flow rate of 3 plmin the main products were 68% ethylene, 16% ethane, and 15% methane. A further increase of the residence time resulted in a reaction progress beyond dehydration to almost complete cracking of the ethanol to methane. 

A 1.3 litre OBR was evaluated for an industrial batch saponification process where conversion to continuous processing in conventional tubular reactors was considered unfeasible, due to the long residence time required. The saponification reaction was the hydrolysis of a complex natural mixture of esters in an ethanol/water solvent. 

Extensive studies of CPO reactions were carrried out by Lanny Schmidt et al. [229] [443] using a millisecond fixed-bed reactor. It was possible to produce syngas over a rhodium monolitii at residence times of milliseconds [229]. Platinum was less active than rhodium. It was shown [242] that the reaetions take place in an oxidation zone as combined surface/gas-phase reactions followed by a steam reforming zone with equilibration of the steam reforming and shift reactions. It was also possible to convert liquid hydrocarbons [164], ethanol [434] and biomass [444] in the milliseeond reactor. 

Under flow conditions, the propane conversion was varied from 30 to 100% by changing the residence time in the reactor and the oxygen concentration. In all cases, methanol was the main liquid product (as in the gas-phase oxidation), which was formed with a selectivity of 12%. In addition, acetone and acetic acid were formed, and to a lesser extent ethanol, acetaldehyde, propionaldehyde and propionic acid, and carbon oxides. The total selectivity to oxygenates reached 15%, whereas the composition of the product was similar that observed in the static experiments. 

The gas-phase oxidation of n-butane in butane—air mixtures composed of 18 vol % C4H10, 3 vol % O2, 79 vol % N2 at pressures of 5,10, and 15 atm and temperatures of 325, 350, and 375 °C was studied in [251,252]. The residence time of the gas mixture in the reaction zone was varied from 2 to 12 s. The heated laboratory reactor was made of a massive stainless steel cylinder with a diameter of 100 mm and a wall thickness of 37.5 mm. The gases were fed into the reactor from a heated rapid-mixture-injection vessel. The quantitatively analysed liquid products were methanol, ethanol, formaldehyde, sum of higher aldehydes, and sum of acids, whereas acetone and ethers were determined qualitatively. 

---