Conventional Thermal Calcination Research Articles

Preparation of Al-Containing ZSM-58 Zeolite Membranes Using Rapid Thermal Processing for CO2/CH4 Mixture Separation.

The synthesis of DDR-type zeolite membranes faces the problem of cracks that occur on the zeolite membrane due to differences in the thermal expansion coefficient between zeolite and the porous substrate during the detemplating process. In this study, Al-containing ZSM-58 zeolite membranes with DDR topology were prepared by rapid thermal processing (RTP), with the aim of developing a reproducible method for preparing DDR zeolite membrane without cracks. Moreover, we verified the influence of RTP before performing conventional thermal calcination (CTC) on ZSM-58 membranes with various silica-to-aluminum (Si/Al) molar ratios. Using the developed method, an Al-containing ZSM-58 membrane without cracks was obtained, along with complete template removal by RTP, and it had higher CO2/CH4 selectivity. An all-silica ZSM-58 membrane without cracks was obtained by only using the ozone detemplating method. ZSM-58 crystals and membranes with various Si/Al molar ratios were analyzed by using Fourier-transform infrared (FTIR) spectroscopy to confirm the effects of RTP treatment. Al-containing ZSM-58 zeolites had higher silanol concentrations than all-silica zeolites, confirming many silanol condensations by RTP. The condensation of silanol forms results in the formation of siloxane bonds and stronger resistance to thermal stress; therefore, RTP caused crack suppression in Al-containing ZSM-58 membranes. The results demonstrate that Al-containing ZSM-58 zeolite membranes with high CO2 permeance and CO2/CH4 selectivity and minimal cracking can be produced by using RTP.

Fast and low-temperature elimination of organic templates from SBA-15 using dielectric barrier discharge plasma

Organic templates P-123 of mesoporous SBA-15 can be effectively removed in a few minutes (4 min) by using the dielectric-barrier discharge (DBD) plasma technique at ambient pressure and low gas temperature (around 130 °C). The mesoporous SBA-15 was characterized by FT-IR, 29Si solid sate NMR, TEM, XRD, TGA and N2 adsorption/desorption isotherms. The as-made SBA-15 treated with DBD plasma exhibited a larger surface area of 790 m2 · g−1 with larger pores and microspore volume than samples prepared by using the conventional thermal calcination method (550 °C and 5 h, 660 m2 · g−1). In addition to less shrinkage of the silica framework, the DBD-prepared SBA-15 showed significantly increased weight loss of 8.3% about 200 °C as compared with that of conventional calcination (5.5%), which is attributed mainly to the dehydroxylation by condensation of silanol groups.

Plasma-Assisted Preparation of Highly Dispersed Cobalt Catalysts for Enhanced Fischer–Tropsch Synthesis Performance

Glow discharge plasma (GDP) was used for the preparation of Co/TiO2 Fischer–Tropsch synthesis (FTS) catalysts promoted by Pt. This technique was compared with conventional thermal calcination for decomposing cobalt precursor. In this study, Pt was added as a reduction promoter in order to improve the reducibility of Co/TiO2 catalysts because the strong interaction between Co and TiO2 is detrimental to the FTS performances. It was found that plasma treatment can effectively decompose the cobalt precursor at a low temperature in a short time (1–4 h). As compared to thermal calcination, the cobalt species prepared by GDP is highly dispersed on TiO2 support. CoPt/TiO2 catalyst with homogeneously and highly dispersed cobalt particles (∼1 nm) was achieved by prolonging plasma treatment from 1 to 4 h. This is difficult to accomplish via conventional calcination method on preparing this loading cobalt catalyst (12 wt %) without the use of extra chemicals and a complicated process. Furthermore, we found that a sho...

Comparison of solid state synthesis of zinc calcium phosphorous oxide (ZCAP) ceramics under conventional and microwave heating methods

In this study, a weight ratio of 50:30:20 of ZnO:CaO:P2O5 was calcined using microwave and conventional thermal treatment at 800 °C to synthesize zinc oxide calcium phosphorous oxide (ZCAP) ceramics. X-ray diffraction data indicated that microwave synthesized ZCAP ceramics was less crystalline than conventionally synthesized ZCAP. Micro-Raman spectroscopy and FTIR confirmed the presence of ZnO, phosphate and carbonate groups in both heat treatment methods. The reported TGA-DSC results demonstrated that carbonate amount was very less (approx. 0.1%) in microwave synthesized ZCAP while in comparison to carbonate amount was high (approx. 0.69%) in conventionally prepared ZCAP. FESEM image analysis showed that particle sizes were comparatively smaller for microwave synthesized ZCAP than conventionally synthesized ZCAP. Hence, microwave calcinations of ZnO, CaO and P2O5 is a promising method to synthesize ZCAP ceramics compared to conventional thermal calcination treatment.

PdOx/Silicalite-1 Catalyst Prepared by Room Temperature Ozone Treatment: Preparation Chemistry and Catalytic Performance for Methane Combustion

The potential of ozone (O3) for preparation of supported metal catalyst remained unexplored. In this work, a two-step preparation method comprising ion-exchange and room temperature ozone treatment was developed to prepare a zeolite (silicalite-1) supported palladium catalyst. The fundamental preparation chemistry was examined by diffuse reflectance UV–Vis spectroscopy, IR and Raman spectroscopy, X-ray powder diffraction (XRD), and scanning transmission electron microscopy (STEM). While conventional thermal calcination produced PdOx particles mostly on the external surface of silicalite-1 crystals, ozone treatment produced PdOx clusters mostly within the zeolite crystals. Compared with thermal calcination, room temperature ozone treatment can significantly suppress the migration of palladium species outward to the external surface of the zeolite crystals. PdOx/silicalite-1 catalyst prepared with this method exhibited good catalytic activity and stability for catalytic methane combustion. The methane combustion started at about 250 °C; the T 50 and T 90 (the temperatures at which methane conversion reaches 50 and 90% respectively) were 345 and 403 °C, respectively. The conversion decreased slightly from 100 to 96.1% after 24 h of reaction at 500 °C. Deactivation is due to some growth of PdO crystallite revealed by Raman spectroscopy and still could not be detected by XRD.

Atmospheric pressure plasma assisted calcination of composite submicron fibers

The plasma assisted calcination of composite organic/inorganic submicron fibers for the preparation of inorganic fibers in submicron scale was studied. Aluminium butoxide/polyvinylpyrrolidone fibers prepared by electrospinning were treated using low-temperature plasma generated by special type of dielectric barrier discharge, so called diffuse coplanar surface barrier discharge (DCSBD) at atmospheric pressure in ambient air, synthetic air, oxygen and nitrogen. Effect of plasma treatment on base polymer removal was investigated by using Attenuated total reflectance – Fourier transform infrared (ATR-FTIR) spectroscopy. Influence of working gas on the base polymer reduction was studied by energy-dispersive X-ray spectroscopy (EDX) and CHNS elemental analysis. Changes in fibers morphology were observed by scanning electron microscopy (SEM). High efficiency of organic template removal without any degradation of fibers was observed after plasma treatment in ambient air. Due to the low-temperature approach and short exposure time, the plasma assisted calcination is a promising alternative to the conventional thermal calcination.

Preparation and application of aluminum‐doped zinc oxide powders via precipitation and plasma processing method

ABSTRACTAluminum‐doped zinc oxide (AZO) conductive powders were successfully obtained through an attractive method based on the pyrolysis of coprecipitated precursors in arc plasma processing. The as‐prepared powders were characterized by the x‐ray diffraction (XRD), transmission electron microscopy (TEM), and UV‐vis spectrum. The results reveal that Al atoms are doped into ZnO lattice successfully and all the samples are polycrystalline with a hexagonal wurtzite structure. Moreover, the particle size of aluminum doped zinc oxide prepared from the plasma pyrolysis was smaller than conventional thermal calcination. Afterward, the synthesized powders were reinforced into polypropylene (PP) matrix and the dispersion of the AZO filler in the PP matrix was observed by SEM. In addition, the effect of AZO concentrations on the electrical and mechanical properties of PP composites was investigated via resistance measurement, tensile and impact tests, respectively. The results show that the electrical and mechanical properties depend on the concentration and dispersion of AZO nanoparticles in the matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41990.

A zirconium modified Co/SiO2 Fischer-Tropsch catalyst prepared by dielectric-barrier discharge plasma

Co/SiO2 and zirconium promoted Co/Zr/SiO2 catalysts were prepared using dielectric-barrier discharge (DBD) plasma instead of the conventional thermal calcination method. Fischer-Tropsch Synthesis (FTS) performances of the catalyst were evaluated in a fixed bed reactor. The results indicated that the catalyst treated by DBD plasma shows the higher FTS activity and yield of heavy hydrocarbons as compared with that treated by the conventional thermal calcination method. Increase in CO conversion was unnoticeable on the Co/SiO2 catalyst, but significant on the Co/Zr/SiO2 catalyst, both prepared by DBD plasma. On the other hand, heavy hydrocarbon selectivity and chain growth probability (α value) were enhanced on all the catalysts prepared by the DBD plasma. In order to study the effect of the DBD plasma treatment on the FTS performance, the catalysts were characterized by N2-physisorption, H2-temperature programed reduction (H2-TPR), H2-temperature-programmed desorption (H2-TPD) and oxygen titration, transmission electron microscope (TEM) and X-ray diffraction (XRD). It was proved that, compared with the traditional calcination method, DBD plasma not only could shorten the precursor decomposition time, but also could achieve better cobalt dispersion, smaller Co3O4 cluster size and more uniform cobalt distribution. However, cobalt reducibility was hindered to some extent in the Co/SiO2 catalyst prepared by DBD plasma, while the zirconium additive prevented significantly the decrease in cobalt reducibility and increased cobalt dispersion as well as the FTS performance.

Performance of Cobalt-Based Fischer-Tropsch Synthesis Catalysts Using Dielectric-Barrier Discharge Plasma as an Alternative to Thermal Calcination

Co-based catalysts were prepared by using dielectric-barrier discharge (DBD) plasma as an alternative method to conventional thermal calcination. The characterization results of N2-physisorption, temperature programmed reduction (TPR), transmission electron microscope (TEM), and X-ray diffraction (XRD) indicated that the catalysts prepared by DBD plasma had a higher specific surface area, lower reduction temperature, smaller particle size and higher cobalt dispersion as compared to calcined catalysts. The DBD plasma method can prevent the sintering and aggregation of active particles on the support due to the decreased treatment time (0.5 h) at lower temperature compared to the longer thermal calcination at higher temperature (at 500° C for 5 h). As a result, the catalytic performance of the Fischer-Tropsch synthesis on DBD plasma treated Co/SiO2 catalyst showed an enhanced activity, C5+ selectivity and catalytic stability as compared to the conventional thermal calcined Co/SiO2 catalyst.

Template Removal from ZSM-5 Zeolite Using Dielectric-Barrier Discharge Plasma

A dielectric-barrier discharge (DBD) plasma technique has been successfully applied for template removal from ZSM-5 zeolite. The rate for template removal using DBD is about eight times higher than that using the conventional thermal calcination. During the template removal using DBD, the highest temperature of the sample is about 125 °C. As such, the thermal effect on the sample during the DBD template removal is not significant. This made the structure changes of ZSM-5 zeolite during the template removal less dramatic than that using thermal calcination. The dielectric-barrier discharge (DBD) plasma, initiated at ambient condition, has been successfully applied for removing template from ZSM-5 zeolite. The rate for the template removal using DBD is about eight times higher than that using the conventional thermal calcination.

Functionalized mesoporous silica films for gas sensing applications

Mesoporous silica films prepared by sol gel process and argon plasma calcination have been used to form hybrids for gas sensing applications by entrapping sensitive materials in the porous network. Plasma calcination, a low temperature process, is employed to gel the sol instead of conventional thermal calcination. Polymers and surfactants are used as templates for generating the mesoporous structure upon removal by the plasma calcination. TEM, EDX and FT-IR are used to characterize the obtained films. To demonstrate the gas sensing property of the functionalized silica films, 10 MHz Quartz Crystal Microbalance (QCM) coated with β-cyclodextrin (β-CD) functionalized silica film is tested as a sensor for benzene vapor detection. The higher surface area of the mesoporous silica films could accommodate more receptor molecules (β-CD molecules) and subsequently more target analytes that enhance the QCM response. The sensitivity of the QCM is enhanced by depositing plasma calcined mesoporous sensing films on the electrodes.

Mesoporous silica thin films prepared by argon plasma treatment of sol–gel-derived precursor

Argon plasma is used to generate the mesoporous silica thin films from sol–gel-derived precursor. Poly(ethylene glycol) (PEG, MW = 400) is employed as the template, i.e., the pore-directing agent as well as the binder. The influence of the plasma parameters (plasma power and processing time) on the mesoscopic properties of silica films are investigated by scanning electron microscopy (SEM), FT-IR, low-angle X-ray scattering (SAXS), and nitrogen adsorption isotherm. It is concluded that the plasma treatment is a promising way to remove organic templates and generate mesoporous thin films. Compared to the conventional thermal calcination methods, the plasma treatment provides a promising low-temperature, low-cost and time-saving preparation process.