A water gas shift (WGS) membrane reactor (MR) has been constructed using a MFI-type zeolite disk membrane packed with a cerium-doped ferrite catalyst. The WGS reaction was performed at high temperatures of 400−550 °C, and the effect of reaction pressure on the MR performance was investigated in a range from 2 to 6 atm with the permeate side swept by nitrogen at atmospheric pressure. Increasing temperature and pressure enhance both the reaction rate and the rate of H 2 membrane permeation that in turn significantly enhances the CO conversion. The equilibrium limit of CO conversion can be surpassed in the MR at high pressure and/or high temperature. It has been demonstrated in this study that membranes with moderate H 2 selectivity can be effective for enhancing CO conversion at high operation temperature and pressure with the cost of low H 2 concentration in the permeate stream. The timely removal of H 2 from the catalyst bed dramatically reduced the undesirable methane production because H 2 is a reactant for methanation reactions in the WGS system. Both the zeolite membrane and the Fe/Ce catalyst also exhibited good resistances to high concentration of H 2 S in WGS reactions.
Tissue engineering and regenerative medicine follow a multidisciplinary attitude to the expansion and application of new materials for the treatment of different tissue defects. Typically, proper tissue regeneration is accomplished through concurrent biocompatibility and positive cellular activity. This can be resulted by the smart selection of platforms among bewildering arrays of structural possibilities with various porosity properties (ie, pore size, pore connectivity, etc). Among diverse porous structures, zeolite is known as a microporous tectosilicate that can potentially provide a biological microenvironment in tissue engineering applications. In addition, zeolite has been particularly appeared promising in wound dressing and bone‐ and tooth‐oriented scaffolds. The wide range of composition and hierarchical pore structure renders the zeolitic materials a unique character, particularly, for tissue engineering purposes. Despite such unique features, research on zeolitic platforms for tissue engineering has not been classically presented. In this review, we overview, classify, and categorize zeolitic platforms employed in biological and tissue engineering applications.
Modified MFI-type zeolite membranes were investigated
as high-temperature water-gas shift (WGS) membrane reactors (MRs)
in combination with a nanocrystalline Fe/Ce WGS catalyst. The effects
of the MR operating conditions and the membrane separation performance
on the CO conversion (χCO) were studied experimentally
and by calculations using a simple one-dimensional plug-flow reactor
(PFR) model. The experimental results showed that, at high temperatures
(e.g., >500 °C), the zeolite MR with moderate H2 selectivity (e.g., αH2/CO2
∼ 31, and αH2/CO ∼ 25)
and permeance (P
m,H2
∼
0.9 × 10–7 mol s–1 m–2 Pa–1) was capable of overcoming
the limit of equilibrium CO conversion and χCO of
the MR could be further enhanced by increasing the reaction pressure
while keeping the permeate pressure unchanged. At high temperatures
and high reaction pressures, CO is rapidly consumed by a fast reaction
that minimizes the membrane permeation of unreacted CO; meanwhile,
the efficiency of H2 removal is improved as a result of
the increased H2 partial pressure difference across the
membrane. The model calculations have indicated that the current membrane
has the potential to achieve high CO conversion of χCO > 99% under practically meaningful operating conditions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.