UZM-8 Zeolite Synthesized from Solid Aluminosilicate Gel and Its Catalytic Performance

Instead of conventional aluminum isopropoxide and silica sources, commercially available solid aluminosilicate gel with SiO2/Al2O3 = 25 was selected to synthesize UZM-8 zeolite with diethyl-dimethylammonium hydroxide (DEDMAOH) as the structure-directing agent (SDA) in the Na+-free system. The structure-directing function and decomposition of DEDMAOH were analyzed. With the irregular stacking of MWW layers, UZM-8 zeolite with solid aluminosilicate gel as silica and aluminum sources possessed better stability during crystallization, better crystallinity, higher surface area, clearly separated Si-29 MAS NMR resonances, and more acid sites accessed by pyridine and 2,4,6-trimethyl-pyridine than conventional synthesized UZM-8 zeolite, which resulted in obvious improvement in ethylene conversion with little loss in ethylbenzene selectivity at higher temperatures

Green Production Technology of the Monomer of Nylon-6: Caprolactam

After two decades’ endeavor, the Research Institute of Petroleum Processing (RIPP) has successfully developed a green caprolactam (CPL) production technology. This technology is based on the integration of titanium silicate (TS)-1 zeolite with the slurry-bed reactor for the ammoximation of cyclohexanone, the integration of silicalite-1 zeolite with the moving-bed reactor for the gas-phase rearrangement of cyclohexanone oxime, and the integration of an amorphous nickel (Ni) catalyst with the magnetically stabilized bed reactor for the purification of caprolactam. The world’s first industrial plant based on this green CPL production technology has been built and possesses a capacity of 200 kt·a−1. Compared with existing technologies, the plant investment is pronouncedly reduced, and the nitrogen (N) atom utilization is drastically improved. The waste emission is reduced significantly; for example, no ammonium sulfate byproduct is produced. As a result, the price difference between CPL and benzene drops. In 2015, the capacity of the green CPL production technology reached 3 × 106 t·a−1, making China the world’s largest CPL producer, with a global market share exceeding 50%

Transformation from NaA to MCM-49 Zeolite and Its Catalytic Alkylation Performance

The transformation from NaA (LTA) to MCM-49 (MWW) zeolite was achieved in the synergism of hexamethyleneimine (HMI), NaOH, and SiO₂, in spite of no common composite build units between LTA (<i>lta</i>, <i>sod</i>, and <i>d4r</i>) and MWW (<i>mel</i> and <i>d6r</i>) structure. NaA (SiO₂/Al₂O₃ = 2.0) was employed as the parent zeolite. The samples prepared at different crystallization stages were characterized by XRD, SEM, ²⁹Si/²⁷Al/¹³C MAS NMR, and STEM-EDS to investigate the intermediates during the transformation from NaA to MCM-49. As shown in SEM and STEM-EDS images, MCM-49 was proposed to be transformed gradually from the exterior to the interior of NaA, which was clearly observed by the core (LTA, low SiO₂/Al₂O₃)–shell (MWW, high SiO₂/Al₂O₃) coexisting zeolites as intermediates. With high relative crystallinity and the uniform sizes of crystals, the final MCM-49 was featured by Si enrichment on the external surface, which was proved by the shell (SiO₂/Al₂O₃ = 45.4) wrapping around the core (SiO₂/Al₂O₃ = 22.0). For transformed H-MCM-49 zeolite, the uniform sizes of crystals and the increase of total acid sites contributed to better accessibility of active centers, which achieved simultaneous improvement in ethylene conversion and ethylbenzene selectivity in the liquid-phase alkylation of benzene with ethylene