Mohamad Zailani Abu Bakar

Effect of fixed carbon molecular sieve (CMS) loading and various di-ethanolamine (DEA) concentrations on the performance of a mixed matrix membrane for CO2/CH4 separation

Polyethersulfone (PES) as a polymer along with carbon molecular sieves (CMS) as an inorganic filler and di-ethanolamine (DEA) as the third component were used to fabricate amine mixed matrix membranes (A3Ms). The CMS and the developed membranes were characterized by variable pressure field emission scanning electron microscopy (VPFESEM) and thermal gravimetric analysis (TGA). FESEM micrographs showed that with the addition of DEA, uniform distribution of CMS particles in the PES matrix was achieved with good polymer-filler contact. The combined effect of DEA concentration (5–15 wt%), feed pressure (2–10 bar) and CMS loading on the CO2/CH4 transport properties of the PES–CMS–DEA membranes were studied. The results revealed that the PES–CMS–DEA (15 wt% DEA) membrane showed a CO2 permeance of 123.49 GPU at 2 bar, which is more than a threefold increment with respect to the native PES membrane. The corresponding CO2/CH4 ideal selectivity was increased from 5.40 for PES to 51.39 for PES–CMS–DEA (15 wt% DEA). The CO2 permeance of the PES–CMS–DEA (A3Ms) membranes was higher than PES membranes over the operating pressure range.

The effect of transmembrane pressure and feed flow rate on transgalactosylation of lactose in an enzymatic membrane reactor

Lactose hydrolysis and transgalactosylation catalyzed by β-galactosidase are important for the production of galacto-oligosaccharides (GOS). These reactions were performed in an enzymatic membrane reactor (EMR) with β-galactosidase immobilized on the inner lumen of the membrane. The effects of hydrodynamic parameters of transmembrane pressure (TMP) and nominal feed flow rate on the reaction were investigated. The rate of GOS formation increased as TMP was increased from 0.2 bar to 0.5 bar and then decreased as the TMP was further increased to 0.8 bar. In contrast to that of GOS, the formation rate of monosaccharides significantly decreased at high nominal feed flow rates. The separation factor between GOS and monosaccharides increased at high TMP, but the overall permeation flux decreased because of the high membrane resistant coefficient of membranes with immobilized β-galactosidase. Moreover, the specific productivity of trisaccharides was higher, whereas that of tetrasaccharides was lower in the EMR than that in batch reactor systems.

The effect of mass transfer on reaction rates during immobilized β-galactosidase-catalyzed conversion of lactose in hollow fiber membrane

Abstract The mass transfer of substrates through a bio-catalytic membrane layer is a key issue in determining the performance of β-galactosidase-catalyzed conversion of lactose in a hollow fiber membrane reactor (HFMR) system. An investigation on the effect of solutes mass transfer through a bio-catalytic membrane layer was carried out using the coupled mass transfer-reaction model. Product formation was reduced at a trans-membrane pressure (TMP) of higher than 0.5 bar. Meanwhile, the concentration polarization modulus of solutes rapidly increased with higher TMP and this result suggests the formation of gel layer, which reduced bio-catalysis rate at higher applied TMP. The concentration profile of solutes or substrates on the bio-catalytic membrane surface, which determines the rate of reaction was reduced due to mass transfer limitation. This investigation highlights that the formation of substrate-β-gal complex in an immobilized system is influenced by the mass transfer behavior of its substrate.

EFFECTS OF FEED CONCENTRATION AND WATER VAPOR ON CATALYTIC COMBUSTION OF ETHYL ACETATE AND BENZENE IN AIR OVER CR-ZSM-5 CATALYST

Catalytic combustion of ethyl acetate (EAc) and benzene (Bz) over chromium exchanged ZSM-5 (Si/Al=240) is reported. An 11 mm i.d. fixed-bed catalytic reactor, operated at temperatures between 100 oC and 500 oC, and under excess oxygen condition, was used for the catalytic activity measurement. Apparent order of reaction and apparent activation energy were determined by operating the reactor differentially at a gas hourly space velocity (GHSV) of 78,900 h-1 and feed concentrations between 3,500 ppm to 17,700 ppm and 3,700 to 12,400 ppm for ethyl acetate and benzene, respectively. Ethyl acetate was more reactive than benzene due to highly reactive carbonyl group in the molecule. The combustion process satisfactorily fitted pseudo first-order kinetics with respect to organic concentration and a zero-order dependence on the oxygen concentration. The presence of water vapor (9,000 ppm) in the feed stream was found to weaken the reactivity of these organics which could also be demonstrated with increases in the activation energy from 23.1 kJ/mole to 37.6 kJ/mole for ethyl acetate and from 27.6 kJ/mole to 46.1 kJ/mole for benzene. Water vapor was found to play a positive role in the formation of carbon dioxide yield in ethyl acetate combustion. Deactivation of catalyst by water appeared to be only temporary and the activity reverted back to its original value once the source of water vapor was removed.