Heterogeneous Pd catalysts were developed by immobilizing Pd nanoparticles (Pd NPs) onto plant polyphenol (bayberry tannin, BT) decorated γ-Al 2 O 3 . The abundant hydroxyls of plant polyphenols were capable of stabilizing the Pd NPs. Transmission electron microscopy observation confirmed that the Pd NPs with the diameter of 3.75 ± 0.5 nm were highly dispersed in the catalyst. The as-prepared Al 2 O 3 –BT–Pd catalysts were found to be highly active in mild hydrodechlorination (HDC) of 2,4-dichlorophenols (DCPs) using formic acid as a hydrogen source. The 2,4-DCPs were completely dechlorinated in 4 h at 30°C and under atmospheric pressure. During the catalytic HDC, the stabilizing capability of BT successfully prevented the leakage and aggregation of Pd NPs, thus ensuring a high cycling stability with stable and high catalytic activity. The Al 2 O 3 –BT–Pd catalysts were recycled six times, without obvious loss of activity. In the sixth cycle, the catalytic HDC yield still reached 98.29% under the same reaction conditions, superior to the control catalysts, including γ-Al 2 O 3 supported Pd NPs (Al 2 O 3 –Pd) and powdered activated carbon supported Pd NPs (AC–Pd). Furthermore, the Al 2 O 3 –BT–Pd also showed high activity in the mild catalytic HDC of 2,4,6-trichlorophenols and chlorobenzene derivatives. Our results demonstrated efficient catalysts to address the environmental issue of chlorophenol pollution.

Cowhide collagen fibers were used as biotemplates to prepare a series of fibrous SO42-/ZrO2-NiO solid acid catalysts. The as-prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N(2 )adsorption/desorption isotherms and the temperature-programmed decomposition (TPD), respectively. The characterization suggested that the SO42-/ZrO2-NiO catalysts have well-defined fibrous morphology which maintains the fibrous structure of cowhide collagen fibers. TPD of ammonia indicated that the catalyst had both medium strong acidic sites and strong acidic sites. The esterification of acetic acid with n-butanol was utilized as model reaction to evaluate the catalytic performance of the catalysts. The catalyst has exhibited high catalytic activity and good reusability.

催化氧化苯甲醇是制备苯甲醛的一种简便高效的方法.以天然高分子黑荆树单宁（BWT）为两亲性稳定剂,制备水溶性钯纳米胶体催化剂,用于苯甲醇的氧化反应.采用透射电镜（TEM）、傅里叶变换红外光谱（FT-IR）等表征手段表征所制备催化剂的形貌,探讨制备条件对催化剂形貌的影响.TEM测试表明,单宁的用量对胶体中钯纳米粒子的粒径具有显著的影响,随着BWT用量从2 mg增加到60 mg,Pd粒子的粒径呈现减小趋势.FT-IR测试表明,BWT通过其结构中大量的酚羟基对Pd纳米粒子进行稳定和分散.系统考察单宁用量、反应温度、反应时间等因素对Pd纳米胶体在苯甲醇氧化反应中活性的影响,结果表明:当BWT用量为15 mg时制备的BWT15 mg-Pd胶体催化剂在50℃,空气气氛下8 h催化苯甲醇的转化率高达98.58%; BWT用量对催化剂重复使用性能也有显著的影响,BWT15 mg-Pd可以重复使用5次转化率仍然在90%以上,明显优于BWT5 mg-Pd和BWT60 mg-Pd.

Developing amphiphilic colloid catalysts is essentially important for realizing environmentally benign biphasic catalysis under atmospheric conditions. Herein, a linear structured plant polyphenol was employed as an amphiphilic stabilizer for preparing a series of amphiphilic Pd nanoparticles (PdNPs) colloids. For the as-prepared PdNPs colloids, the phenolic hydroxyls of plant polyphenols were responsible for the stabilization of PdNPs, whereas the rigid aromatic scaffold of plant polyphenols effectively suppressed the PdNPs from aggregation by providing a high steric effect. Thanks to the coexistence of hydrophilic phenolic hydroxyls and hydrophobic aromatic rings, the plant polyphenols induced tunable amphiphilic properties into the PdNPs, allowing an easier wetting of PdNPs with the substrate molecules. By tuning the content of plant polyphenols in the colloid, the particle size (3.17-4.73 nm) and the dispersity of the PdNPs were facilely controlled. When applied for atmospheric oxidation of insoluble alcohols in water by air, the amphiphilic PdNPs preferentially absorbed the alcohol substrates to create a relatively high-substrate-concentration microenvironment, which improved the mass transfer in the biphasic catalysis, allowing the proceeding of low-temperature (50 °C) atmospheric oxidation of diverse alcohols with high catalytic conversion, including aliphatic alcohols, cyclic aliphatic alcohols, and aromatic alcohols. Furthermore, the amphiphilic PdNPs colloid also exhibited excellent reusability with a conversion yield high up to 97.96% in the fifth cycle. In contrast, the control catalysts of poly(vinylpyrrolidone)- and poly(ethylene glycol)-stabilized PdNPs were completely inactivated in the fifth cycle. As a consequence, our findings provided a new route for developing an environmentally benign aqueous colloid catalyst that is both highly active and recyclable for mild biphasic oxidation reaction systems.

A novel biosorbent was facilely prepared by immobilizing bayberry tannin (BT, a typical natural polyphenols) onto chitosan microfiber (CM). The as-prepared CM-BT adsorbent featured to a well-defined microfibrous morphology and highly distributed adsorption sites, which was highly efficient and selective for the adsorptive removal of Cr3+ from aqueous solutions. Based on batch experiments, the adsorption of Cr3+ on CM-BT was pH-dependent, and the optimized adsorption pH was determined to be 5.5. The adsorption capacity of CM-BT to Cr3+ was high up to 20.90 mg/g. The co-existing cations, such as Mg2+, Ca2+, Fe3+ and Cu2+, exhibited no significant influences on the adsorption of Cr3+ on CM-BT. The adsorption kinetics were well fitted by the pseudo-second-order rate model (R-2 > 0.99) while the adsorption isotherms were well described by the Langmuir model (R-2 > 0.98). Importantly, CM-BT was effective for the continues treatment of low concentration Cr3+ (2.0 mg/L) contaminated wastewater. Before reached the breakthrough point (5% of the initial Cr3+ concentration, 0.1 mg/L), the treated volume was as high as 894 bed volume, manifesting the great potential of CM-BT in practical treatment of Cr3+ contaminated wastewater. (C) 2017 Elsevier B.V. All rights reserved.

Noble metal nanoparticles are promising candidates to replace conventional bulk counterparts owing to their high activity and selectivity. To enable catalyst recovery, noble metal nanoparticles are often supported onto solid matrices to prepare heterogeneous catalyst. Although recycle of noble metal nanoparticles is realized by heterogenization, a loss of activity is usually encountered. In the present investigation, Pt nanoparticles with tunable particle size (1.85–2.80 nm) were facilely prepared by using polyphenols as amphiphilic stabilizers. The as-prepared Pt nanoparticles colloid solution could be used as highly active catalyst in aqueous–organic biphasic catalysis. The phenolic hydroxyls of polyphenols could constrain Pt nanoparticles in aqueous phase, and simultaneously, the aromatic scaffold of polyphenols ensured effective interactions between substrates and Pt nanoparticles. As a consequence, the obtained polyphenols-stabilized Pt nanoparticles exhibited high activity and cycling stability in biphasic hydrogenation of a series of unsaturated compounds. Compared with conventional heterogeneous Pt-C and Pt-Al2O3 catalysts, polyphenols-stabilized Pt nanoparticles showed obvious advantage both in activity and cycling stability.