Preparation of high silica microporous zeolite SSZ-13 using solid waste silica fume as silica source

Tuning product selectivity in the MTO reaction over Zn-modified SSZ-13 catalysts

In this work, Zn-modified SSZ-13 catalysts with different spatial distributions of zinc species were prepared by ion exchange (IE), wet impregnation (WI) and in situ synthesis (IS) methods employed for the methanol-to-olefin (MTO) reaction.

Synthesis of zeolite SSZ-13 from coal gangue via ultrasonic pretreatment combined with hydrothermal growth method

SSZ-13 zeolite has been widely used in catalysis and adsorption because of good hydrothermal stability and pore structure. However, long crystallization time is the main challenge limiting its industry application. As increased emissions and ineffective treatment, coal gangue not only occupies land, but also pollutes the waterbody and farmland. Using coal gangue as raw material to synthetize zeolite has been considered as an environmentally friendly and effective alternative to solve the issues of accumulation and pollution, which also improves the added value of coal gangue. The ultrasonic assistance has been proven to be one of the potential pretreatment methods to promote the dissolution of crystalline silicon aluminum and reduce the crystallization time of molecular sieve. In this work, SSZ-13 was synthesized by coal gangue via ultrasonic pretreatment combined with hydrothermal growth method. The ultrasonic frequency and power were 20 kHz and 120 W, respectively. The synthesized samples were characterized by XRD, SEM, EDS, BET. The results showed that the crystallization time was shorten to 18 h, which was about 12 h lower than the same conditions of conventional chemicals synthesis. Furthermore, the specific surface area of the synthesized sample was more than 620 m²/g, which also indicated over 95% NO_x conversion across a broad range from 180 to 400 °C and over 94% NO_x conversion at 200-400 °C after hydrothermal treatment 6 h. This study provides a reference for the environmentally friendly utilization of coal gangue and the low-cost rapid synthesis and application of SSZ-13.

Defect-Rich Nickel Nanoparticles Supported on SiC Derived from Silica Fume with Enhanced Catalytic Performance for CO Methanation

With the increased demands of environmental protection, recycling/utilization of industrial byproducts has attracted much attention from both industry and academic communities. In this work, silicon carbide (SiC) was successfully synthesized from industrial waste silica fume (SF) during metallic silicon production. Following this, Ni nanoparticles with many defects were supported on the as-obtained SiC by conventional impregnation method. The results showed that defect-rich Ni nanoparticles were dispersed onto the surface of SiC. The as-obtained Ni/SF-SiC exhibited an enhanced metal-support interaction between Ni and SiC. Furthermore, the density functional theory (DFT) calculations showed that the H2 and CO adsorption energy on Ni vacancy (VNi) sites of Ni/SF-SiC were 1.84 and 4.88 eV, respectively. Finally, the Ni/SF-SiC performed high catalytic activity with CO conversion of 99.1% and CH4 selectivity of 85.7% at 350 °C, 0.1 MPa and a gas hourly space velocity (GHSV) of 18,000 mL·g−1·h−1. Moreover, Ni/SF-SiC processed good catalytic stability in the 50 h continuous reaction.