Preparation of Pt/Ce–Zr–Y mixed oxide/anodized aluminium oxide catalysts for hydrogen passive autocatalytic recombination

The use of a Pt-based catalyst was evaluated for autocatalytic hydrogen recombination. The Pt was supported on a mixture of Ce-, Zr- and Y-oxides (CZY) to yield nanosized Pt particles. The Pt/CZY/AAO catalyst was then prepared by the spray-deposition of the Pt/CZY intermediate onto an anodized aluminium oxide (AAO) layer on a metallic aluminum core. The Pt/CZY/AAO catalyst (3 × 1 cm) was evaluated for hydrogen combustion (1–8 vol% hydrogen in the air) in a recombiner section testing station. The thermal distribution throughout the catalyst surface was investigated using an infrared camera. The maximum temperature gradient (ΔT) for the examined hydrogen concentrations did not exceed 36 °C. The Pt/CZY/AAO catalyst was also evaluated for prolonged hydrogen combustion duration to assess its durability. An average combustion temperature of 239.0 ± 10.0 °C was maintained for 53 days of catalytic hydrogen combustion, suggesting that there was limited, or no, catalyst deactivation. Finally, a Pt/CZY/AAO catalytic plate (14.0 × 4.5 cm) was prepared to investigate the thermal distribution. An average surface temperature of 212.5 °C and a maximum ΔT of 5.4 °C was obtained throughout the catalyst surface at a 3 vol% hydrogen concentration.     

Carbon nanotube filter for heavy metal ion adsorption

This study investigated carbon nanotube filtration technology using catalyst particles supported on silicalite-1–biomorphic carbon materials (BCMs). Aqueous solutions of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) were used to test the efficiency of heavy metal ions removal. Carbon nanotubes (CNTs) were synthesized and grown on BCMs by the chemical vapor deposition method catalyzed with the catalyst (Co, Fe, and Ni). The synthesized CNTs with Co– and Fe– nanoparticles were typically multi-walled carbon nanotubes, and they showed good crystallinity (I_D/I_G = 1.05) and yield of (11.10 and 8.86) %. The removal efficiency of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) ions using Co-catalyzed CNT filter was 97.57%, 98.01%, 97.89%, 97.42%, and 99.99%, respectively.     

Dealumination–aging pattern of REUSY zeolites contained in fluid cracking catalysts

The evolution of the properties of a REUSY zeolite contained in a fluid cracking catalyst was investigated under laboratory steam deactivation procedures and in age fractions of the corresponding equilibrium catalyst (Ecat). The aging pattern, defined by the evolution of the zeolite surface area (ZSA) related to the decrease of the unit cell size (UCS), was similar between lab-steamed zeolites and Ecat fractions. A sharp drop in ZSA occurred at ca. 2.430 nm UCS. A study done by FT-IR spectroscopy suggested that zeolite dealumination initially took place more extensively on the sodalite cages and double six-member rings (D6R) of the structure and that the final collapse of the zeolite framework occurred through destruction of the 12-member rings (12M). This can be explained by a crystal fracture and break down process and disassembling of the sodalite cages in the faujasite structure. NH₃ microcalorimetry showed that strong acid sites in faujasites are destroyed by steam aging, but this effect does not lead to a reduction in the cracking activity of the Ecat form. The microactivity test (MAT) showed that the specific activity declined sharply at 2.430 nm UCS. Differences in product selectivity were related to the extent of damage of the zeolite, extra-framework alumina and mesoporosity. While further aging canceled the effect attributed to extra-framework alumina differences attributed to mesoporosity increased.     

NaY晶化母液制备硅铝胶的技术探讨

在导向剂法合成Y型分子筛的工艺下，晶化母液中SiO₂的含量为50～55g/l,Na₂O含量为20～25g/l，相当于模数为1.65～2.58的稀水玻璃，将晶化母液分离处理后，在晶化母液中加入一定量的硫酸铝溶液使硅沉淀,经过滤和水洗后即可制备出合格的硅铝胶，以便进行重新利用。     

Separating n-alkane mixtures by exploiting differences in the adsorption capacity within cages of CHA, AFX and ERI zeolites

The saturation capacity of n-alkanes in CHA, AFX and ERI zeolites, that consist of cages separated by windows, decreases with increasing carbon number. The major aim of the present communication is to demonstrate the possibility of separating n-alkane mixtures relying on differences in saturation capacities. To investigate this possibility, Configurational-Bias Monte Carlo simulations for adsorption of C3–nC6, nC4–nC6, and nC5–nC6 mixtures in CHA, AFX and ERI were carried out for equimolar bulk fluid phase. These mixture simulations show that for operation at fluid phase fugacities below about 1 MPa, the adsorbed phase in equilibrium with the bulk vapor phase is predominantly the alkane with the longer chain length, i.e. nC6. However, for operation at pressures in excess of 1 MPa, the adsorbed phase in equilibrium with the bulk liquid phase is richer in the component with the smaller chain length. In some cases, the nC6 is practically excluded from the zeolite.     

Synthesis and characterization of zeolite NaY from rice husk silica

Rice husk silica (RHS) in amorphous phase with 98% purity was prepared from a waste rice husk from rice milling by leaching with hydrochloric acid and calcination. The RHS was used effectively as a silica source for the synthesis of zeolite Y in sodium form (NaY). The zeolite in pure phase was obtained from a two-step synthetic route in which the starting gels were mixed, aged for 24 h at room temperature and crystallized for 24 h at 90 °C. The diameter of single crystal particles from a scanning electron microscope was approximately 1.0 μm, whereas the average particle diameter from laser diffraction particle size analyzer was approximately 10 μm because of the agglomeration of small crystals. Longer crystallization time in this route resulted in a mixed phase containing NaY and zeolite P in sodium form (NaP). In addition, a one-step synthetic route (no aging) was studied and the product was also a mixed phase zeolite.     

中间馏分油型加氢裂化催化剂用沸石的研究

通过水热处理法制备了3个不同脱铝深度的改性Y沸石，再经浸渍法制成中间馏分油型加氢裂化催化剂，在200mL小型加氢裂化装置上进行了催化性能评价。试验结果表明，除了沸石的酸性外，其孔结构和比表面积对催化剂的活性、中间馏分油选择性和液体收率都有很大的影响，为最大幅度提高催化剂的中间馏分油选择性并保持较好活性，要求沸石具有较低的酸量、较高的比表面积和较多的二次孔及适量的L酸量。     

Direct synthesis of copper faujasite

Copper containing faujasite has been successfully prepared for the first time using a direct synthesis method. Faujasite type zeolite can be prepared in the presence of copper species by tuning the synthesis conditions. Ammonium hydroxide was used to form a copper complex that was later mixed with the reacting gel. Sodium is required to obtain copper faujasite. The complete elimination of sodium ions from the starting gel produces amorphous material. Crystallization took place at 358 K for 11 days. Crystallization temperature of 373 K produces ANA type zeolite as an impurity. Increasing by two times the amount of copper complex added to the reacting gel increases the crystallization time of Cu-FAU from 11 to 20 days (the crystallization rate decreases). The copper containing faujasite obtained was characterized by XRD, FESEM, EDX, EPR, FT-IR, TPR, and BET. According to the XRD pattern only FAU type zeolite was obtained. According to TPR experiments, the reduction temperature for Cu²⁺ ions present in Cu-FAU prepared by direct synthesis was 70 K more than for Cu-FAU prepared by ion-exchange. This difference can be due to the different location of the copper ions in the supercages or in the sodalite cages of the faujasite.