•Dual templates synthesis of intergrowth AEI/CHA and pure AEI zeolites.•Template composition affects the size and acidity of the final crystal.•Longer crystallization time converts metastable AEI phase into stable CHA phase.•The extending of crystallization time is against the formation of light olefins.A series of SAPO molecular sieves were hydrothermally synthesized by employing mixture template of diethylamine (DEA) and N, N′-diisopropylethylamine (DIEA). The influences of template composition and crystallization time were investigated systematically. The results revealed that the crystalline products switched from SAPO-34/5 to SAPO-18/34 and finally to SAPO-18, the crystal size and acidity decreased with the increasing of DIEA ratio in the mixed template. Furthermore, crystallization time was also found to play a significant role in the particulate properties of the zeolites, the metastable AEI phase converted into more stable CHA phase, the Si content and acidity increased with the prolonged crystallization time. Dimethyl ether (DME) to olefins (DTO) reactions showed that the extending of the crystallization time was against the formation of light olefins, but favorable for the formation of light alkanes, due to the increase in CHA/AEI ratio, particle size and acidity may increase the probability of unfavorable hydrogenation of the target light olefins.

In order to investigate the effect of phase composition in the silicoaluminophosphate (SAPO) zeolites on their catalytic performance for the dimethyl ether (DME) to olefin (DTO) reaction, four well crystalline SAPO zeolites with different SAPO-18/34 ratios were synthesized hydrothermally by using a mixed template of diethylamine (DEA) and N,N′-diisopropylethylamine (DIEA). The effects of the composition of the mixed template on the physicochemical properties of the zeolites were investigated by XRD, SEM, TEM, XRF, FT-IR and NH3-TPD techniques. The results revealed that the phase composition, morphology, particle size, chemical composition and surface acidity of the zeolites were greatly affected by the template composition. Catalytic tests showed that both SAPO-18 and SAPO-34 presented relatively faster coking rates compared with that of SAPO-18/34 intergrowth zeolites, and pure SAPO-18 with the smallest crystallite size and weakest acidity exhibited the highest amount of coke deposition. The DME conversion and product distribution were similar over all catalysts, but the selectivities of light olefins showed a strong correlation to the cage size. That is, the catalysts with a higher content of slightly wider AEI cages favor the formation of propylene and butylene, and catalysts with a higher content of relatively narrower CHA cages benefit the formation of ethylene.

SAPO-18 molecular sieve is an important catalyst for dimethylether-to-olefins (DTO) reaction. Although the conventional synthesized SAPO-18 using N,N′-diisopropylethylamine (DIEA) alone exhibits nanoparticles and better catalytic performance due to the weaker diffusion resistance, its high cost of preparation and difficult separation of the powder limit the industrial process of this type of molecular sieve. Therefore, reducing the cost and increasing the particle size appropriately become the key issues for its practical application. In this study, SAPO-18 catalysts were synthesized hydrothermally using mixture of triethylamine (TEA) and a small amount of DIEA as templates. The results revealed that fairly pure SAPO-18 molecular sieve with particle size of approximately 1.0 μm could be synthesized under the initial gel composition as: xDIEA:(1.4−x)TEA: 1.0 Al2O3: 0.9 P2O5:0.6SiO2:50H2O, where x varies from 0.2 to 0.6. Furthermore, the catalytic performance for DTO reaction over the novel synthesized SAPO-18 catalysts showed higher selectivities to light olefins and much lower coke deposition than the conventional synthesized SAPO-18 using DIEA alone.

Bi2MoO6–RGO composite nanoplates with good uniformity and highly oriented growth of the active lattice were successfully synthesized by a simple hydrothermal process with the assistance of graphene oxide. Reduced graphene oxide was observed to be formed on the surface of the Bi2MoO6 nanoplates after the hydrothermal treatment. A remarkable enhancement in the visible-light-driven (VLD) photocatalytic destruction of bacteria was observed over the Bi2MoO6–RGO composite when compared to pure Bi2MoO6.

This paper reports the preparation and photocatalytic performance of Bismuth vanadate (BiVO4) by a facile and inexpensive approach. An amorphous BiVO4 was first prepared by a co-precipitation process from aqueous solutions of Bi(NO3)3 and NH4VO3 using ammonia. Followed by heating treatment at various temperatures, the amorphous phase converted to crystalline BiVO4 with a structure between monoclinic and tetragonal scheelite. The crystallization of BiVO4 occurred at about 523 K, while the nanocrystalline BiVO4 were formed with a heat-treatment of lower than 673 K. However, when the heat-treatment was carried out at 773 K, the accumulation of nanocrystals to bulk particles was observed. The photocatalytic performances of the materials were investigated by O2 evolution under visible-light, and MB decomposition under solar simulator. The results demonstrated that the crystalline structure is still the vital factor for the activities of both reactions. However, the crystallinity of BiVO4 gives a major influence on the activity of O2 evolution, whereas the surface area, plays an important role for photocatalytic MB decomposition.BiVO4 was prepared by a co-precipitation process using aqueous ammonia solution, followed by heating treatment at various temperatures. The crystalline structure and crystallization process, and their influences on photocatalytic O2 evolution and organic pollutants degradation were investigated. It demonstrated that the crystalline structure is still the vital factor for the activities of both reactions. However, the crystallinity of BiVO4 gives a major influence on the activity of O2 evolution, whereas the surface area, plays an important role for photocatalytic MB decomposition.