G.T.P. Mabande

Hydrothermal transformation of a layered sodium silicate, kanemite, into zeolite Beta (BEA)

Hydrothermal transformation of a layered sodium silicate, kanemite, in the presence of tetraethylammonium hy- droxide (TEAOH, 30%), into a commercially important zeolite Beta (BEA) has been investigated. During the hy- drothermal transformation of kanemite, zeolite Na-P1 was formed as an intermediate product and subsequently transformed into highly crystalline and phase-pure zeolite Beta as indicated by different physico-chemical characteri- sation techniques. The influence of various parameters such as SiO2/Al2O3 ratio, temperature, and TEAOH/SiO2 ratio were examined. For comparisons, hydrothermal transformation of other layered silicates such as Na-magadiite and Na- ilerite were also studied under similar reaction conditions. The catalytic activity of a zeolite Beta sample obtained by the hydrothermal transformation of kanemite was also demonstrated in the cracking of n-hexane at atmospheric pressure in a fixed bed reactor.

Solid state transformation of TEAOH-intercalated kanemite into zeolite beta (BEA)

The work reported herein involves the synthesis of zeolite beta by solid state transformation of TEAOH-intercalated kanemite, at 140 °C, under autogenous pressure. A series of TEAOH-intercalated kanemite samples were prepared by intercalation of kanemite with TEAOH at room temperature followed by centrifugation and drying at 35 °C for 24 h. The XRD, TG-DTA and chemical analyses of the TEAOH-intercalated kanemite samples revealed that either the TEAOH molecules were intercalated into the interlayer spaces or strongly adsorbed onto the outer surfaces of kanemite. Zeolite beta samples in high yields (71–97%) were obtained by solid state transformation of TEAOH-intercalated kanemite samples having moderate amounts of TEAOH (TEAOH/SiO2 = 0.11–0.23). The XRD measurements showed that the zeolite beta samples obtained from the present method were phase-pure and highly crystalline. SEM studies revealed that the zeolite beta samples were composed of agglomerated crystallites. For the zeolite beta samples, surface areas of as high as 586 m2 g−1 were observed by the BET method. In addition, the zeolite beta sample (SiO2/Al2O3 = 12) obtained from TEAOH-intercalated kanemite was found to be active for the cracking of n-hexane and its performance was comparable to a standard zeolite beta sample (SiO2/Al2O3 = 20).

Hydrothermal transformation of porous glass beads into porous glass beads containing zeolite beta (BEA)

Abstract Hydrothermal transformation of porous glass beads into porous glass beads containing zeolite Beta (BEA) is achieved, at 160 °C, using tetraethylammonium hydroxide (TEAOH) as the templating agent. The products were characterised by various techniques. The XRD results indicate that the transformation of porous glass beads into phase-pure zeolite Beta occurs within the SiO 2 /Al 2 O 3 ratios of 50–100. The Light microscopic images indicate that the shape of the starting porous glass beads is preserved during the hydrothermal treatment. SEM reveals that the outer surface of the porous glass beads is completely covered by zeolite Beta crystals. N 2 adsorption isotherm reveals the microporous nature of the zeolite Beta sample obtained from porous glass beads.

Defect-free zeolite membranes of the type BEA for organic vapour separation and membrane reactor applications

Abstract In this work defect free BEA type zeolite membranes with varying Si/Al ratio (18 to 33) were prepared on stainless-steel supports using a “multiple in -situ crystallization” technique. The quality of the membranes was evaluated using p-/o-xylene isomer separation, and 1,2,4-/1,3,5-trimethyl benzene isomer separation. A maximum p-xylene permeance of 1.5 × 10 −7 mol s −1 m −2 pa −1 and p-/o-xylene separation factor of 3.3 was obtained while in the trimethyl benzene separation experiments permeances were lower but the separation factor was comparatively higher (~ 4.8).

Structured SiSiC-zeolite ceramic composites for catalytic applications via a support self-transformation technique

The overall 3-step process for the manufacturing of SiSiC-zeolite structured cellular composites was studied. The process consists of a 2-step procedure for the ceramic monolith fabrication, followed by the functionalisation of the support surface with zeolite coating (3 rd step). SiSiC ceramic monoliths were prepared by reactive Liquid Silicon Infiltration (LSI) of carbon preforms from corrugated cardboard monoliths. The zeolite coating process consisted of a hydrothermal treatment of the SiSiC carrier in an alkaline solution containing the template and the Al-source, while the Si was provided from the ceramic substrate. MFI-type (ZSM-5) zeolite crystals were directly grown on the ceramic supports via a partial Si dissolution (from the SiSiC matrix) and zeolite crystallisation (support self-transformation). Cellular SiSiC-zeolite monoliths possess bimodal (micro-/macro-) porosity and high mechanical, chemical and thermal stabilities.

Intercalation of [Pt(NH3)4]2+ ions into the layered sodium silicate, Na-magadiite

Abstract Intercalation of [Pt(NH3)4]2+ ions into the layered silicate, Na-magadiite, has been studied as a method to prepare Pt nanopartic les supported on silica. TEM images of the [Pt(NH3)4]2+-magadiite sample calcined at 600°C indicate that the Pt nanoparticles (2–3 nm) are highly dispersed into the silica matrix.