Lian-Feng Chu

Preparation and synergetic catalytic effects of amino-functionalized MCM-41 catalysts

Four amine functionalized mesoporous catalysts were synthesized by grafting primary, dualistic and two secondary amines onto the channel walls of mesoporous silica, MCM-41. We examined the effects of organoamine loading amount on the acid-base synergism of the catalysts in the self-condensation reaction of n-butanal, a Knoevenagel condensation and a Henry reaction. We observed the balance of the amine and residual silanol amounts is crucial to the catalytic performances of the functionalized mesoporous catalysts. An optimum organoamine loading amount exists, which is dependent on the organoamine type. There is little difference in the optimum organoamine loading amount between different reactions. The secondary organoamine functionalized MCM-41 exhibits the best catalytic performance in the experimental range.

Hydrothermally prepared chromia-alumina (xCr/Al2O3) catalysts with hierarchical structure for propane dehydrogenation

Propane dehydrogenation was investigated over a series of chromia-alumina (xCr/Al2O3) catalysts containing 2.5–10 wt% chromium (Cr), synthesized via a hydrothermal synthesis method. The synthesized xCr/Al2O3 catalysts with hierarchical spindle-like morphology have high specific area and highly dispersed chromia on the surface of γ-Al2O3. Besides, the higher Cr6+/Cr3+ ratio is advantageous to obtain higher propane conversion and lower propylene selectivity. The synthesized 7.5Cr/Al2O3 catalyst exhibits the highest propane conversion of 62% accompanied by 89% propylene selectivity at 873 K. After regenerated by re-calcinating in air, the original activity of the spent catalyst is well recovered.

Synthesis of Tubular Faujasite X-Type Membranes with Mullite Supports and their Gas Permeances for N2/CO2 Mixtures

The present work reports the synthesis of tubular faujasite (FAU) X-type membranes with mullite supports for the permeation separation of N2/CO2. The external surfaces of mullite supports were modified and seeded with X-type zeolite crystals prior to film growth in synthesis solutions. We investigated the effects of synthesis conditions including the composition of synthesis solution and the process of hydrothermal treatment on the formation of FAU X-type membranes. We also characterized the membrane morphology and phases using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, we evaluated the permeation separation of N2/CO2 with the as-synthesized membranes. The results indicated that increasing aging time accelerated the crystal growth rate, but overlong aging time could cause the generation of P-type zeolite and thicker membrane layer. Prolonging crystallization time and raising temperature would increase the rate of crystal nucleation, but readily made trans-crystallization phenomena occur. The Na/Si ratio did not play a significant role in synthesizing FAU X-type membranes in the tested range. The as-synthesized zeolite membranes with higher ratio of Si/Al accompanied with the formation of P-type crystal and the particle size on the membrane surface obviously increased. The membrane with a smoother zeolite surface and a thinner top layer was obtained with increasing H2O content. For single-gas permeation, CO2 had a lower permeance than N2. For the gas mixtures of N2/CO2, the separation factor α of 7.89 was gained.