Methane steam reforming in a membrane reactor using high-permeable and low-selective Pd-Ru membrane

We performed a methane steam reforming (MSR) reaction through a membrane reactor packed with commercial Ni/Al2O3 catalyst and a tubular Pd-Ru membrane deposited on a YSZ modified porous stainless steel support under mild operating conditions: 773 K and a pressure difference range of 100-250 kPa. We prepared the Pd-Ru membrane with thickness of similar to 6 mu m on a tubular stainless steel support (diameter 12.7mm, length 25 cm) using electroless plating, which was observed for the membrane performance using hydrogen and nitrogen. Gas permeation test carried out at 773 K and 31.4 kPa of pressure difference between retentate and permeate sides showed that the hydrogen permeation rate and nitrogen leakage were similar to 0.1050mol s(-1) m(-2) and similar to 0.0018 mol s(-1) m(-2), respectively. The MSR reaction was under the following conditions: temperature 773 K, pressure 100-250 kPa, gas hourly space velocity (GHSV) 837 h(-1), and steam-to-carbon feed ratio (S/C) 3. The MSR reaction result showed that methane conversion was increased with increasing pressure difference and reached similar to 77.5% at 250 kPa. In this condition, the composition of carbon monoxide was similar to 2%, meaning that no two series of water gas shift reactors were needed in our membrane reactor system. Longterm stability test carried out for similar to 100 h showed that methane conversion and the hydrogen yield remained constant

Removal of Hazardous Hydrogen Fluoride (HF) from Water Through Homogeneous Nanostructured CaO-SiO2 Sorbents: Optimization of Binder

In this study, we prepared a homogeneous dispersion of CaO-SiO2 sorbent with advanced nanostructures as an efficient solid-reducing agent for the elimination of hazardous chemicals. The hydrophobic properties of SiO2 ceramic particles are of interest for reducing the limitations and enhancing the chemical properties of highly hygroscopic materials. Nano-sized SiO2 is introduced and composited with CaO through a facile synthetic route. The structural and microstructural characteristics and elemental compositional analyses confirm the uniform distribution of the CaO-SiO2 nanocomposite. The as-prepared nanocomposites have particle sizes in the range of similar to 20-100 nm. Optimization of the composition reveals that the 60 wt% CaO-SiO2 can be considered as an efficient solid-reducing agent for the hydrogen fluoride (HF) removal process. In order to identify the catalytic effect and binder ratio, the specific surface area and HF removal performance was investigated and compared to CaO-SiO2 nanostructures with individual CaO catalyst. The higher amount of HF concentration was absorbed by CaO-SiO2 catalyst than the CaO only. In the first 2.5-h reaction, the outlet HF concentration is rapidly increased to 380 ppm by using CaO catalyst as a HF sorbent. However, the outlet HF concentration is sluggishly increased up to 180 ppm, when nanostructured CaO-SiO2 catalyst used as a sorbent in RE-RCS. It has been found that the addition of hydrophobic properties of SiO2 has prevented the reaction between water/moisture and CaO in CaO-SiO2 catalyst system, which is a major reason for enhancement in HF removal process. Furthermore, the CaF2 byproduct can be effectively used in the ceramic industry and building material applications

Conceptual feasibility studies of a CO (X) -free hydrogen production from ammonia decomposition in a membrane reactor for PEM fuel cells

CO (X) -free hydrogen production from ammonia decomposition in a membrane reactor (MR) for PEM fuel cells was studied using a commercial chemical process simulator, Aspen HYSYSA (R). With process simulation models validated by previously reported kinetics and experimental data, the effect of key operating parameters such as H-2 permeance, He sweep gas flow, and operating temperature was investigated to compare the performance of an MR and a conventional packed-bed reactor (PBR). Higher ammonia conversions and H-2 yields were obtained in an MR than ones in a PBR. It was also found that He sweep gas flow was favorable for X (NH3) enhancement in an MR with a critical value (5 kmol h(-1)), above which no further effect was observed. A higher H-2 permeance led to an increased H-2 yield and H-2 yield enhancement in an MR with the reverse effect of operating temperature on the enhancement. In addition, lower operating temperature resulted in higher X (NH3) enhancement and H-2 yield enhancement as well as NG cost savings in a MR compared to a conventional PBR