In this work, a novel glow discharge plasma treatment of Pd/HZSM-5 catalyst, followed by calcination thermally, has been conducted. Such prepared catalyst presents a higher catalytic activity and an enhanced stability over the catalyst prepared without plasma treatment. The methane conversion over the plasma treated catalyst is close to 100% at 450℃, but it is only ca. 50% at the same temperature over the catalyst without plasma treatment. The XPS, H2 chemisorption and XRD characterizations confirm an enhanced dispersion has been achieved with the plasma reduction (during treatment) followed by oxidation (during calcination). Upon FT-IR analyses, the plasma treatment, followed by calcination thermally, also leads to enhanced Brönsted and Lewis acidities. The amount of Brönsted acid sites of the plasma treated Pd/HZSM-5 catalyst is 1.13 times larger than that of the catalyst without plasma treatment, while the amount of Lewis acid sites of the plasma treated Pd/HZSM-5 catalyst is 1.21 times higher. The enhanced acidities are definitely helpful to increase the dispersion of PdO over the support and improve the interaction between PdO and HZSM-5 support, which leads to a remarkable improvement in the catalyst stability.

We reported in this work a simple, effective, and efficient hydrogen production from plasma methanol decomposition using DC and AC corona discharges at ambient condition. The highest hydrogen production rate was achieved with AC corona discharges. The power consumption was normally less than 0.02 Wh/Ncm3 H2. A major advantage of methanol decomposition using corona discharge is that only a very small discharge space is enough for sufficiently high decomposition.

A density functional theory (DFT) study has been conducted to investigate the structural and electronic properties of PdO/HZSM-5 and thereby the relationship between PdO and the acid sites of HZSM-5. Different cluster models of PdO/HZSM-5 based on experimental and theoretical works are presented. The study shows that the local structure of PdO supported on HZSM-5 is very similar to the four-coordinated square planar structure of bulk PdO. This is consistent with the reported EXAFS analysis in the literature. The average distances between the Pd and the four coordinated oxygen atoms obtained by DFT calculations with different cluster models are close to the reported experimental results. The analysis of the Mulliken population and the electron density difference of the cluster models shows that there exists a charge transfer from the four coordinated oxygen atoms to the Pd. The components of the frontier molecular orbital of these cluster models come mainly from the Pd and the four coordinated oxygen atoms. The DFT study confirms that the acid sites in HZSM-5 keep the PdO well dispersed due to the bond interaction between the acidic proton atom and the oxygen atom of PdO. In addition, after the formation of PdOH+, the acidity of HZSM-5 complex remains high or in some instances increases.

Novel amorphous Ni-B catalysts supported on alumina have been developed for the production of hydrogen peroxide from carbon monoxide, water and oxygen. The experimental investigation confirmed that the promoter/Ni ratio and the preparation conditions have a significant effect on the activity and lifetime of the catalyst. Among all the catalysts tested, the Ni-La-B/γ- Al2O3 catalyst with a 1:15 atomic ratio of La/Ni, dried at 120℃, shows the best activity and lifetime for the production of hydrogen peroxide. The deactivation of the alumina-supported Ni-B amorphous catalyst was also studied. According to the characterizations of the fresh and used catalysts by SEM, XRD and XPS, no sintering of the active component and crystallization of the amorphous species were observed. However, it is water poisoning that leads to the deactivation of the catalyst. The catalyst characterization demonstrated that the active component had changed (i.e., amorphous NiO to amorphous Ni(OH)2) and then salt was formed in the reaction conditions. Water promoted the deactivation because the surface transformation of the active Ni species was accelerated by forming Ni(OH)2 in the presence of water. The formed Ni(OH)2 would partially change to Ni3(PO4)2.