A scanning pulse reaction technique for transient analysis of the methanol-to-hydrocarbons reaction

A method of scanning pulse gas chromatography (SP-GC) suitable for time-resolved analysis of transient response of catalysts to reactant pulses is introduced. Applied to the methanol-to-hydrocarbons reaction over several zeolite-based catalysts (HZSM-5, Ca/ZSM-5 and Ga/ZSM-5), SP-GC provided quantitative information about the transient reactivity and selectivity during methanol conversion. The SP-GC analysis demonstrates substantial differences in the relative rates of hydrocarbon formation between catalysts that favor aromatic or olefin cycles of the dual cycle hydrocarbon pool mechanism. The influence of metal promoters on the main reaction pathways was highlighted with an emphasis on mechanistic aspects

Improving the performance of ASA in the DAC of 2,5-DMF and ethylene

A variety of methods are employed to synthesize amorphous silica-alumina (ASA) to resolve the role of Al speciation and surface area in the catalytic performance in the Diels-Alder cycloaddition reaction of 2,5-dimethylfuran and ethylene to p-xylene. ASA was prepared by homogeneous deposition-precipitation (HDP) of Al 3+ on ordered mesoporous silica, i.e., SBA-15 and OMS prepared under hydrothermal synthesis conditions using an imidazole-based template, and one-step flame spray pyrolysis (FSP). IR spectroscopy and 27Al MAS NMR showed that the resulting ASA represented a set of materials with distinct textural and acidic properties. ASA prepared by grafting Al to ordered mesoporous silica led to a much higher concentration of Brønsted acid sites (BAS). These samples performed much better in the DAC reaction, with p-xylene yields higher than those obtained with a HBeta zeolite benchmark. Materials with Al partially in the bulk of silica (OMS, FSP) and containing significant alumina domains are less acidic and exhibit much lower p-xylene yields. These findings point to the importance of Brønsted acidity for p-xylene formation. This study shows that careful design of the Al speciation can lead to amorphous silica-alumina with similar DAC performance to microporous zeolites.</p

Improving the performance of ASA in the DAC of 2,5-DMF and ethylene

A variety of methods are employed to synthesize amorphous silica-alumina (ASA) to resolve the role of Al speciation and surface area in the catalytic performance in the Diels-Alder cycloaddition reaction of 2,5-dimethylfuran and ethylene to p-xylene. ASA was prepared by homogeneous deposition-precipitation (HDP) of Al 3+ on ordered mesoporous silica, i.e., SBA-15 and OMS prepared under hydrothermal synthesis conditions using an imidazole-based template, and one-step flame spray pyrolysis (FSP). IR spectroscopy and 27Al MAS NMR showed that the resulting ASA represented a set of materials with distinct textural and acidic properties. ASA prepared by grafting Al to ordered mesoporous silica led to a much higher concentration of Brønsted acid sites (BAS). These samples performed much better in the DAC reaction, with p-xylene yields higher than those obtained with a HBeta zeolite benchmark. Materials with Al partially in the bulk of silica (OMS, FSP) and containing significant alumina domains are less acidic and exhibit much lower p-xylene yields. These findings point to the importance of Brønsted acidity for p-xylene formation. This study shows that careful design of the Al speciation can lead to amorphous silica-alumina with similar DAC performance to microporous zeolites.</p