Yonghua Zhou

A highly active and stable Pd-TiO2/CDC-SiC catalyst for hydrogenation of 4-carboxybenzaldehyde

Carbon has been widely used as a catalyst support and adsorbent in industry. However, it suffers from poor stability due to its limited mechanical strength, particularly under high pressures and temperatures. We report here a carbide derived carbon (CDC) layer on a porous SiC surface, which has the properties of high mechanical strength and is easy to shape. The CDC exhibits an amorphous structure and contains mainly mesopores with a BET surface area of 125 m2 g−1. The CDC–SiC composite yields a comparable performance to coconut activated carbon (AC) as a catalyst support in the probe reaction hydrogenation of 4-carboxybenzaldehyde. The further introduction of TiO2 nanoparticles enhances the activity and stability significantly because of the improved dispersion of Pd particles on CDC–SiC. The activity is 4 times higher than the Pd/AC catalyst. Pd–TiO2/CDC–SiC shows great promise as an alternative to the current AC supported Pd catalyst for the crude terephthalic acid hydropurification industry.

Selectivity modulation in the consecutive hydrogenation of benzaldehyde via functionalization of carbon nanotubes

Hydrogenation of benzaldehyde is a typical consecutive reaction, since the intermediate benzyl alcohol is apt to be further hydrogenated. Here we demonstrate that the selectivity of benzyl alcohol can be tuned via functionalization of carbon nanotubes (CNTs), which are used as the support of Pd. With the original CNTs, the selectivity of benzyl alcohol is 88% at a 100% conversion of benzaldehyde. With introduction of oxygen-containing groups onto CNTs, it drops to 27%. In contrast, doping CNTs with N atoms, the selectivity reaches 96% under the same reaction conditions. The kinetic study shows that hydrogenation of benzyl alcohol is significantly suppressed, which can be attributed to weakened adsorption of benzyl alcohol. This is most likely related to the modified electronic structure of Pd species via interaction with functionalized CNTs, as shown by XPS characterization.

G-C3N4-coated activated carbon-supported Pd catalysts for 4-CBA hydrogenation: effect of nitrogen species

We report here a g-C3N4-coated activated carbon as the support for Pd catalysts and investigate the effect of nitrogen species in g-C3N4 on the dispersity and stability of Pd.

A highly stable and active Pd catalyst on monolithic cordierite with graphene coating assisted by PDDA

A Pd catalyst on monolithic cordierite with graphene coating was prepared with assistance from poly(diallyldimethylammonium chloride) (PDDA). The obtained catalyst exhibits both high stability and activity in the liquid hydrogenation reaction of styrene due to the improved interaction between the graphene coating and cordierite and enhanced dispersion of Pd particles.

Pd confined in grass-like graphene layers on monolithic cordierite as the catalyst for hydrogenation of 4-carboxybenzaldehyde

Pd nanoparticles were confined in grass-like graphene layers on monolithic cordierite by using nh2-ion liquid c(7)h(14)cln(3)functionalized graphene sheets. these were used as the catalyst for the hydrogenation of 4-carboxybenzaldehyde. the catalyst exhibited high stability compared to pd/activated carbon catalyst due to the inhibition of pd leaching and aggregation. (c) 2015, dalian institute of chemical physics, chinese academy of sciences. published by elsevier b.v. all rights reserved.

Supported TiO2–Pd bifunctional catalysts for the one-pot synthesis of methyl isobutyl ketone from acetone: modulation of the acid and base property of loaded TiO2 by support

In this work, we prepared a series of supported TiO2–Pd bifunctional catalysts for one-pot synthesis of methyl isobutyl ketone (MIBK) from acetone. The effects of supports including SiO2 with different pore structure, Al2O3 calcined at varied temperature, and F-modification on the catalytic performance were investigated. The results showed that microporous SiO2 was not beneficial to the dispersion of TiO2 inspite its high specific surface area. The calcination of Al2O3 had little effect on the acid and base property of TiO2 loaded thereon. F-modification of support was proved to be an effective way to modulate the acid and base property of TiO2 loaded thereon. As for the catalytic performance, TiO2 loaded on the F-modified mesoporous SiO2 showed the performance 60.9% MIBK yield, with acetone conversion of 77.2% and MIBK selectivity of 78.9%, higher than those ever reported. The excellent performance could be attributed to the enhanced electronic transfer between TiO2 and SiO2 after F modification which greatly affected the acid and base property of loaded TiO2. Taking the advantages of facile synthesis and high performance, the as-reported TiO2/SiO2(B-F)&Pd/Cor catalyst could be a promising alternative for one-pot synthesis of MIBK from acetone.

Phosphor-doped hexagonal boron nitride nanosheets as effective acid–base bifunctional catalysts for one-pot deacetalization–Knoevenagel cascade reactions

One-pot cascade reactions over metal-free heterogeneous bifunctional catalysts have been attracting increased attention in green chemistry owing to the advantage of process intensification, as well as the elimination of wastes and metal contamination. In this paper, phosphor-doped hexagonal boron nitride nanosheets (BNP) can act as excellent metal-free acid–base bifunctional catalysts for one-pot deacetalization–Knoevenagel cascade reactions. XRD, FT-IR, XPS, and solid NMR characterizations indicate that phosphor was doped into the framework of h-BN mainly at the corner (N2PO) and bayer (N3P–OH) sites. The CO2-TPD and NH3-TPD characterizations showed that the BNP sample with optimal phosphor-doping amounts simultaneously possessed the highest amount of acid and base sites. When correlated with the catalytic performance, it can be concluded that mainly N3P–OH acts as the Bronsted acid sites and –BNH2 and N2PO as the Lewis and Bronsted base sites, respectively. In addition, the good recycling stability and immobilization feasibility on a monolith support confirm its potential in practical applications.