Methanol steam reforming over Cu supported on SiO ₂ , amorphous SiO ₂ ‐Al ₂ O ₃ , and Al ₂ O ₃ catalysts: Influence

Abstract

SiO 2 -, Al 2 O 3 -, and SiO 2 -Al 2 O 3 -based catalysts containing different Si/Al ratios have been prepared to study the effect of the support nature on the methanol steam reforming process catalyst. Methanol steam reforming reaction was carried out using each of the catalysts in the temperature range of 150 C to 300 C, weight hourly space velocity (WHSV) of 1.8 h À1 , and atmospheric conditions in a quartz reactor. The properties of the synthesized catalysts were determined by the X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), H 2 -temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD) techniques. SiO 2 -Al 2 O 3 -based catalysts showed better performance (yield @300 C: 87.2%

Efficient cascade conversion of starch to gluconic acid by a chemoenzymatic system with co-immobilized Au nanoparticles and enzymes

“…28 The obvious saturated adsorption platform appeared in the hysteresis isotherms of Au–SiO 2 and GA&GOx@Au–SiO 2 , indicating their more uniform pore-size distribution than SiO 2 and SiO 2 -SH. 29 As summarized in Table S1,† the pore volume and pore size of SiO 2 , SiO 2 -SH, Au–SiO 2 , and GA&GOx@Au–SiO 2 decreased with the progress of catalyst immobilization. It was worth noting that the BET specific surface area of Au–SiO 2 was larger than that of SiO 2 -SH.…”

Enhancing Hydrogen Production in Methanol Steam Reforming Using PdZn-Based Catalysts: A Mini-review on CO Suppression

“…In the case of PdZn@ZnO, superior CO selectivity was assigned to a higher distribution of PdZn alloy particles on the ZnO shell and minimal alloy particles agglomeration, possibly due to stronger metal–support interactions. Furthermore, PdZn catalysts also demonstrated excellent performances with high CO 2 selectivity, thanks to high CO suppression, across a range of conversions when incorporated into perovskite structures (Figure d, e). , The effective CO suppression by these materials is attributed to unique properties such as presence of oxygen vacancies and tailored electronic properties. − …”

“…For example, endothermic reactions like methanol decomposition are activated by high temperatures, which necessitates optimal temperatures for CO suppression. Hourly space velocity influences the amount of feed on the catalyst surface, which directly affects the probability of secondary (CO-producing) reactions occurrence; pressure affects the probability of gas-to-gas reactions occurrence through which RWGS can be activated; and S/M ratio determines the stoichiometric balance between methanol and steam, which favors either methanol steam reforming or decomposition. , The supports, synthesis methods, promoters, and pretreatment affect alloy particles formation and distribution and, subsequently, catalyst’s ability to suppress CO formation; − see section . Properties such as catalyst pore size (which correlates to diffusion limitations), oxygen vacancies, acidity, or basicity, as well as their densities, have also been reported to be fairly impactful on CO formation/suppression. ,,− …”

“…Surprisingly, utilization of theoretically effective supports, e.g., acidic supports such as zeolites and acidic metal oxides, for CO suppression, e.g. through suppression of RWGS, has been largely unexplored for PdZn-based catalysts compared to Cu-based catalysts. − Nevertheless, available literature shows unique supports’ influence on CO selectivity over PdZn-based catalysts (see Table ), with variations being attributed to supports’ unique properties such as pore size, strength of interaction with PdZn, their ability to influence PdZn β alloy particles formation and distribution, etc., all of which effectively affect the formation or suppression of CO. The successful use of unconventional supports to date, such as ZnO shell, ZnAl 2 O 4 , and perovskites, perfectly demonstrates how hugely impactful novel supports can be, usually because of their enhanced properties such as surface area, capacity for interaction with PdZn, and oxygen vacancies. − …”

“…Acidity introduction can be performed via incorporation of acidic materials like acidic metallic oxides and acidic supports, e.g., zeolites as either primary or secondary supports. For instance, significant CO suppression has been reported over moderately acidic zeolites and silica–alumina supports for Cu- and precious metal-based catalysts. ,, The use of hierarchical or mesoporous acidic materials may be even more crucial for mitigation of diffusion limitations through which more CO suppression is reported. ,,− Lastly, the synthesis of catalysts with optimal fractions of PdZn (111) and PdZn (211) for PdZn/ZnO systems, aiming for ideal methanol steam reforming, is an equally promising alternative.…”