Increasing <i>para</i>-Xylene Selectivity in Making Aromatics from Methanol with a Surface-Modified Zn/P/ZSM‑5 Catalyst

We report a ZSM-5 based catalyst with surface modification of SiO₂ to increase the selectivity of <i>para</i>-xylene (PX) in xylene (X) in the methanol-to-aromatics process. The effect of acid strength and acid amount in HZSM-5, Zn/P/ZSM-5, and Zn/P/Si/ZSM-5 on the catalytic performance, including methanol conversion, aromatic yield, and PX selectivity, were studied. The total acid strength and acid amount of the catalyst were crucial for high methanol conversion (around 100%) and high yield of aromatics (>60%), whereas weak external acid sites present in a small amount played an important role in increasing the PX selectivity (in the X isomers) from the usual 23–24% to 89.6%. The results validated the use of a catalyst having a core with strong acid sites in a large amount and an external shell with weak acid sites in a small amount. The contribution of the external surface reaction, including alkylation, isomerization, and dealkylation, to the PX selectivity was evaluated by using PX or <i>ortho</i>-X separately as feedstock. A Zn/P/Si/ZSM-5 catalyst worked well in continuous reaction/catalyst-regeneration cycles, and it also converted recycled toluene into PX by an alkylation route

CK20 mRNA expression in serum as a biomarker for colorectal cancer diagnosis: A meta-analysis

The aim of this study was to evaluate the diagnostic value of serumCK20 mRNA as a biomarker for colorectal cancer diagnosis by meta-analysis

Highly Electroconductive Mesoporous Graphene Nanofibers and Their Capacitance Performance at 4 V

We report the fabrication of one-dimensional highly electroconductive mesoporous graphene nanofibers (GNFs) by a chemical vapor deposition method using MgCO₃·3H₂O fibers as the template. The growth of such a unique structure underwent the first <i>in situ</i> decomposition of MgCO₃·3H₂O fibers to porous MgO fibers, followed by the deposition of carbon on the MgO surface, the removal of MgO by acidic washing, and the final self-assembly of wet graphene from single to double layer in drying process. GNFs exhibited good structural stability, high surface area, mesopores in large amount, and electrical conductivity 3 times that of carbon nanotube aggregates. It, used as an electrode in a 4 V supercapacitor, exhibited high energy density in a wide range of high power density and excellent cycling stability. The short diffusion distance for ions of ionic liquids electrolyte to the surface of GNFs yielded high surface utilization efficiency and a capacitance up to 15 μF/cm², higher than single-walled carbon nanotubes