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Slip casting process for the manufacture of tubular alumina microfiltration membranes

100%

Falamaki C. , Beyhaghi M.

tom Vol. 27, No. 2

427--441

A thorough investigation of the slip casting process for the manufacture of tubular alumina microfiltration membranes is presented. For this means an initial powder of an average particle size of 2 žm and broad size distribution (up to 10 žm) for imparting initial large pores during the slip casting process was used. The dispersing ability of sodium carboxymethylcellulose (Na-CMC) and Tiron (C6H4O8S2Na2źH2O) for slips containing 40, 50 and 60 wt. % of alumina was studied. It was shown that Na-CMC is not able to act as a proper dispersant. The kinetics of the slip casting process and time dependences of cast twodimensional profile were investigated in function of slip concentration. The effect of sintering temperature on the pore microstructure of the final products was investigated. In all cases, the cross sections of the tubular membranes consisted of two regions: an inner thick section, consisting of relatively large pores, and a thin outer section, consisting of smaller pores. This phenomenon was attributed to Na-CMC migration during drying prior to sintering. The ratio of the thicknesses of the two sections depended on the slip concentration and sintering temperature. The average permeable pore size, based on dry nitrogen permeability experiments, was in the range of 0.13-0.24 žm. The controlled use of partial binder migration during cast drying for the production of graded microfilter membranes was addressed.

Methanol dehydration to dimethyl ether using modified clinoptilolite

80%

Royaee S. J. , Sohrabi M. , Falamaki C.

Materials Science Poland

2007

tom Vol. 25, No. 4

1149--1160

Clinoptilolite, a natural zeolite from the Semnan region in the West of Iran, has been converted to a catalyst for the methanol dehydration to dimethyl ether process. To produce such a catalyst and to create acidic sites on the latter, the ion-exchange process has been used. In addition, to investigate and optimize the effective factors of the catalyst synthesis process, a L9 Taguchi experimental design method has been implemented. The effects of four factors have been considered: the type of ion-exchange solution (2 levels); ion-exchange solution concentration; calcination temperature and calcination time (the last three factors have been studied in 3 levels). The yield of catalyst (conversion x selectivity) has been chosen as the response of the system. The catalytic behaviour of the produced samples was investigated using a fixed bed reactor (T = 350 oC, P = 1 atm and WHSV = 4.78 h-1 ). The results of the statistical design showed that the optimum conditions were: calcination time - 3 h, calcination temperature - 500 oC, ionexchange solution concentration - 2M, and ion-exchange solution - ammonium chloride. The optimum catalyst was tested using a fixed bed reactor at 330 oC, 1 atm and WHSV= 3.8 h-1 resulting in 98.1% conversion and 96.5% selectivity. In order to investigate the catalyst behaviour under industrial operating conditions, the catalyst was tested in a fixed bed reactor at 300 oC, 16 atm pressure, and WHSV = 52.5 h-1. The results were 67.02% conversion and 99.74% selectivity.