Limin Ren

Designed copper–amine complex as an efficient template for one-pot synthesis of Cu-SSZ-13 zeolite with excellent activity for selective catalytic reduction of NOx by NH3

Low-cost copper-amine complex was rationally designed to be a novel template for one-pot synthesis of Cu-SSZ-13 zeolites. Proper confirmation and appropriate size make this complex fit well with CHA cages as an efficient template. The products exhibit superior catalytic performance on NH(3)-SCR reaction.

Seed-directed synthesis of zeolites with enhanced performance in the absence of organic templates

We demonstrate here a seed-directed synthesis (SDS) of Beta, Levyne, and Heulandite zeolites in the absence of organotemplates, where the seeds drive crystallization of the zeolites. Compared with conventional Beta synthesized in the presence of organic templates, Beta-SDS exhibits large textural parameters, stable Al species, and unprecedentedly high density of active sites, resulting in superior catalytic activity and selectivity for valuable products in catalysis.

Excellent Performance of One-Pot Synthesized Cu-SSZ-13 Catalyst for the Selective Catalytic Reduction of NOx with NH3

Cu-SSZ-13 samples prepared by a novel one-pot synthesis method achieved excellent NH3-SCR performance and high N2 selectivity from 150 to 550 °C after ion exchange treatments. The selected Cu3.8-SSZ-13 catalyst was highly resistant to large space velocity (800 000 h(-1)) and also maintained high NOx conversion in the presence of CO2, H2O, and C3H6 in the simulated diesel exhaust. Isolated Cu(2+) ions located in three different sites were responsible for its excellent NH3-SCR activity. Primary results suggest that the one-pot synthesized Cu-SSZ-13 catalyst is a promising candidate as an NH3-SCR catalyst for the NOx abatement from diesel vehicles.

Self‐Pillared, Single‐Unit‐Cell Sn‐MFI Zeolite Nanosheets and Their Use for Glucose and Lactose Isomerization

Single-unit-cell Sn-MFI, with the detectable Sn uniformly distributed and exclusively located at framework sites, is reported for the first time. The direct, single-step, synthesis is based on repetitive branching caused by rotational intergrowths of single-unit-cell lamellae. The self-pillared, meso- and microporous zeolite is an active and selective catalyst for sugar isomerization. High yields for the conversion of glucose into fructose and lactose to lactulose are demonstrated.

High-temperature synthesis of stable and ordered mesoporous polymer monoliths with low dielectric constants

Highly ordered body cubic (Im-3m) mesoporous phenol-formaldehyde resins (OMR) monoliths were successfully synthesized at high temperatures (200–260 °C) by the assembly of copolymer surfactant (F127) with preformed resol. The preformed resol was obtained from heating a mixture of phenol and formaldehyde at 70 °C. These ordered mesoporous resins synthesized at relatively high temperatures (OMR-200 and OMR-260) show extraordinary thermal and mechanical stabilities, compared with mesoporous polymers synthesized at low temperature (OMR-100 and FDU-15). OMR-200 and OMR-260 samples were characterized with NMR spectroscopy and numerous other techniques. Characterization results suggest that OMR-200 and OMR-260 have much higher cross-linking degree than OMR-100, which might be responsible for the high thermal and mechanical stabilities of OMR-200 and OMR-260 samples. Furthermore, the dielectric constant tests of samples show that OMR-200 and OMR-260 are better than conventional resins, which are reasonably attributed to the presence of porosity in the samples. The unique features of OMR-200 and OMR-260 with superior thermal and mechanical stabilities as well as low-k values might be potentially important for their applications such as heat insulator.

Discovery of optimal zeolites for challenging separations and chemical transformations using predictive materials modeling

Zeolites play numerous important roles in modern petroleum refineries and have the potential to advance the production of fuels and chemical feedstocks from renewable resources. The performance of a zeolite as separation medium and catalyst depends on its framework structure. To date, 213 framework types have been synthesized and >330,000 thermodynamically accessible zeolite structures have been predicted. Hence, identification of optimal zeolites for a given application from the large pool of candidate structures is attractive for accelerating the pace of materials discovery. Here we identify, through a large-scale, multi-step computational screening process, promising zeolite structures for two energy-related applications: the purification of ethanol from fermentation broths and the hydroisomerization of alkanes with 18-30 carbon atoms encountered in petroleum refining. These results demonstrate that predictive modelling and data-driven science can now be applied to solve some of the most challenging separation problems involving highly non-ideal mixtures and highly articulated compounds.

UV-Raman and NMR spectroscopic studies on the crystallization of zeolite A and a new synthetic route.

UV-Raman and NMR spectroscopy, combined with other techniques, have been used to characterize crystallization of zeolite A. In situ UV-Raman spectroscopy shows that the starting gel for crystallization of zeolite A contains a lot of four-ring (4R) building units and the appearance of six-ring (6R) building blocks is the signal for crystal formation. (29)Si NMR spectroscopy results suggest that the starting gel is double four-ring (D4R) rich and during crystallization of zeolite A both α and β cages appear. (27)Al NMR spectroscopy results indicate the absence of Al (2Si) species in the starting gel, suggesting the absence of single 4R building units in the starting gel. Furthermore, composition analysis of both solid and liquid samples shows that the solid rather than liquid phase predominates for the crystallization of zeolite A. Therefore, it is proposed that the crystallization of zeolite A mainly occurs in the solid phase by self-assembly or rearrangement starting from the zeolite building units mainly consisting of D4R. The essential role of D4R is directly confirmed by successful conversion from a solution of D4R to zeolite A in the presence of NaCl, and the importance of solid phase is reasonably demonstrated by the successful synthesis of zeolite A from a dry aluminosilicate gel. By considering that the solid phase has a major contribution to crystallization, a novel route was designed to synthesizing zeolite A from the raw materials water glass (Na(2)SiO(3) in aqueous solution) and NaAlO(2), without additional water and NaOH; this route not only simplifies synthetic procedures, but reduces water consumption.

Design and Synthesis of a Catalytically Active Cu-SSZ-13 Zeolite from a Copper-Amine Complex Template

The modern synthesis of zeolites typically uses organic structure-directing agents. Therefore, the developing of new templates is part of zeolite research. The design and synthesis of Cu-SSZ-13 using a novel template of a low-cost copper amine complex (Cu2+ coordinated with tetraethylenepentamine) were reported, where the copper amine complex is both a template for synthesizing the SSZ-13 structure and a source of copper species in the zeolite. The calculated size of the complex (0.728 nm x 0.922 nm) matches well with the CHA cages (0.73 nm x 1.2 nm), which are the building units of the SSZ-13 zeolite. Various techniques were used to investigate the chemical and physical properties of the synthesized zeolite. The results showed that the sample has the SSZ-13 zeolite structure, high crystallinity, adjustable Si/Al ratios, and controllable copper loading. Catalytic tests using the selective catalytic reduction of NOx with NH3 showed that the Cu-SSZ-13 was a superior catalyst, and it can be important for the abatement of environmentally harmful NOx.

Stable Bulky Particles Formed by TS‐1 Zeolite Nanocrystals in the Presence of H2O2

Bulky particles of TS‐1 zeolite (larger than 20 μm) are successfully collected by simple filtration after crystallization of TS‐1 zeolite in the presence of H2O2. Bulky TS‐1 (B‐TS‐1) has good stability under both ultrasonic conditions and in recycling of the catalyst. Nitrogen isotherms show that B‐TS‐1 has a larger mesopore volume (0.55 cm3 g−1) than conventional TS‐1 nanocrystals (N‐TS‐1; less than 300 nm) obtained from high‐speed centrifugation (0.28 cm3 g−1). In catalytic hydroxylation of phenol with H2O2, both fresh (25 %) and recycled B‐TS‐1 (24 %) show similar high activities to N‐TS‐1 (28 %). B‐TS‐1 was further characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, UV/Vis spectroscopy, and other techniques. The results suggest that bulky particles of B‐TS‐1 were formed by strong interactions of the nanocrystals with each other in the synthesis of TS‐1 zeolite. Such unique structural features might be responsible for the high stability of the bulky particles, large mesopore volume, and high catalytic activities in phenol hydroxylation, as well as the collection of B‐TS‐1 from a simple filtration route.

Organotemplate-free and seed-directed synthesis of ZSM-34 zeolite with good performance in methanol-to-olefins

The methanol-to-olefins (MTO) reaction over zeolites is of great importance due to the shortage of crude oil, and we demonstrate here a fast, organotemplate-free, and seed-directed synthesis of ZSM-34 zeolite, designated as ZSM-34-S, having very high selectivity for propylene. When the temperature is at 140–180 °C, ZSM-34-S zeolite could be crystallized for 2–6 h in the presence of ZSM-34 crystals as seeds. For industry, a fast and organotemplate-free synthesis, a typically green route, means significant savings in energy and costs. Characterizations using XRD, SEM, 27Al and 29Si MAS NMR, and N2 sorption techniques show that the ZSM-34-S crystals grow from the seeds of ZSM-34 crystals in an amorphous aluminosilicate. Catalytic tests of the MTO reaction show that HZSM-34-S has a very high selectivity for propylene (55.2%), which is even higher than that (47.0%) of SAPO-34 under the same conditions. Moreover, the hydrothermal treatment of HZSM-34-S significantly improves the catalyst life for MTO due to decreasing acidic concentration and increasing anti-deactivation. The combination of a “green” synthesis and the good catalytic performance of ZSM-34-S would be potentially important for the highly effective conversion of methanol, which can be easily obtained from coal, natural gas, or biomass at a large scale.