Understanding the catalytic performance and deactivation behaviour of second-promoter doped Pt/WO_(χ)/γ-Al_(2)O_(3) catalysts in the glycerol hydrogenolysis for selective and cleaner production of 1,3-propanediol

The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the catalyst deactivation via sintering,metal leaching,and coking can predominantly occur in the aqueous phase reaction.In this work,the effect of reaction temperature,pressure and second promoter(Cu,Fe,Rh,Mn,Re,Ru,Ir,Sn,B,and P)on catalytic performance and deactivation behaviour of Pt/WOx/-Al2O3 was investigated.When doped with Rh,Mn,Re,Ru,Ir,B,and P,the second promoter boosts catalytic activity by promoting great dispersion of Pt on support and increasing Pt surface area.The increased Bronsted acid sites lead to selective synthesis of 1,3-PDO than 1,2-propanediol(1,2-PDO).The characterization studies of fresh and spent catalysts reveal that the main cause of catalyst deactivation is the Pt sintering,as interpreted based on XRD,CO chemisorption,and TEM analyses.The Pt sintering is affected depending on the second promoter that can either or reduce the interaction between Pt,WO_(χ)/γ and Al_(2)O_(3).As an electron acceptor of Pt in Pt/WO_(χ)/γ-Al_(2)O_(3),Re and Mn as second promoters resulted in increased Pt^(2+) on the catalytic surface,which strengthens the contact between Pt andγ-Al_(2)O_(3) and WO_(χ),resulting in a decrease in Pt sintering.The metal leaching and coking are not affected by the presence of second promoter.The catalyst modified with a second promoter possesses improved catalytic activity and 1,3-PDO production,however the stability continues to remain a challenge.The present work unrav-elled the determining parameters of catalytic activity and deactivation,thus providing a promising pro-tocol toward effective catalysts for glycerol hydrogenolysis.

Highly active Cu/SiO_2 catalysts for hydrogenation of diethyl malonate to 1,3-propanediol

Cu/SiO2 catalysts prepared by the ammonia evaporation method were applied to hydrogenation of diethyl malonate to 1,3‐propanediol. The calcination temperature played an important role in the structural evolution and catalytic performance of the Cu/SiO2 catalysts, which were systematically characterized by N2 adsorption‐desorption, inductively coupled plasma‐atomic emission spectros‐copy, N2O chemisorption, X‐ray diffraction, Fourier transform infrared spectroscopy, H2 tempera‐ture‐programmed reduction, transmission electron microscopy, and X‐ray photoelectron spectros‐copy. When the Cu/SiO2 catalyst was calcined at 723 K, 90.7%conversion of diethyl malonate and 32.3%selectivity of 1,3‐propanediol were achieved. Compared with Cu/SiO2 catalysts calcined at other temperatures, the enhanced catalytic performance of the Cu/SiO2 catalyst calcined at 723 K can be attributed to better dispersion of copper species, larger cupreous surface area and greater amount of copper phyllosilicate, which results in a higher ratio of Cu＋/Cu0. The synergetic effect of Cu0 and Cu＋is suggested to be responsible for the optimum activity.

Synergistic effects of bimetallic Cu-Fe/SiO_2 nanocatalysts in selective hydrogenation of diethyl malonate to 1,3-propanediol

Cu-x-Fe-y/SiO2 catalysts were prepared using urea-assisted sol-gel method. The structure and physicochemical properties of the catalysts were characterized using N-2 adsorption-desorption, transmission electron microscopy, H-2-temperature-programmed reduction, powder X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with monometallic Cu or Fe catalysts, the bimetallic Cu-x-Fe-y/SiO2 catalysts exhibited enhanced catalytic performance for the selective hydrogenation of diethyl malonate to 1,3-propanediol. The bimetallic catalyst with an optimal Cu/Fe atomic ratio of 2 exhibited the highest activity, which yielded 96.3% conversion to diethyl malonate and 93.3% selectivity to 1,3-propanediol under the optimal reaction conditions. Characterization results revealed that interactions between Cu and Fe contributed to the improvement of diethyl malonate conversion and selectivity to 1,3-propanediol. The X-ray photoelectron spectroscopy results revealed that the addition of appropriate amount of Fe species enhanced the reduction of Cu2+ species, thereby increasing the Cu-0 species on the surface of bimetallic catalyst. It led to a better chemisorption capacity of hydrogen and further promoted of the activation of hydrogen molecule. The ethyl acetate temperature-programmed desorption results indicated that the FeOx species provided the additional adsorption sites for substrate molecules, and they activated the C=O bond. The improved catalytic performance of bimetallic Cu-x-Fe-y/SiO2 catalyst was mainly attributed to the synergistic effect between Cu-0 and FeOx species. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Optimization of fermentation conditions for 1,3-propanediol production by marine Klebsiella pneumonia HSL4 using response surface methodology

The industrially important organic compound 1,3-propanediol （1,3-PDO） is mainly used as a building block for the production of various polymers. In the present study, response surface methodology protocol was followed to determine and optimize fermentation conditions for the maximum production of 1,3-PDO using marine-derived Klebsiella pneumoniae HSL4. Four nutritional supplements together with three independent culture conditions were optimized as follows： 29.3 g/L glycerol, 8.0 g/L K2HPO4, 7.6 g/L （NH4）2SO4, 3.0 g/L KH2PO4, pH 7.1, cultivation at 35℃ for 12 h. Under the optimal conditions, a maximum 1,3-PDO concentration of 14.5 g/L, a productivity of 1.21 g/（L＇h） and a conversion of glycerol of 0.49 g/g were obtained. In comparison with the control conditions, fermentation under the optimized conditions achieved an increase of 38.8% in 1,3-PDO concentration, 39.0% in productivity and 25.7% in glycerol conversion in flask. This enhancement trend was further confirmed when the fermentation was conducted in a 5-L fermentor. The optimized fermentation conditions could be an important basis for developing low- cost, large-scale methods for industrial production of 1,3-PDO in the future.

微生物转化甘油生产1,3-丙二醇的研究进展

甘油是油裂解和生物柴油生产过程中的主要副产物,生物柴油市场的蓬勃发展将会造成甘油价格的下降。这些甘油-水混合物不用再次处理就可以直接用于微生物发酵。在众多甘油的利用当中,附加值最高的应该是1,3-丙二醇(PDO),利用甘油在厌氧条件下发酵生产PDO与传统工艺相比产物浓度从70～80g/L提高到了100g/L,而且如果用固定化细胞发酵,产率可以从2g/(L·h)提高到30g/(L·h)。综述了微生物转化甘油为1,3-丙二醇的研究进展。

Isolation and characterization of a Klebsiella pneumoniae strain from mangrove sediment for efficient biosynthesis of 1,3-propanediol

1,3-Propanediol （PDO） is an important bulk industrial material. It can be produced by microbial fermentation. In this study, the microbial flora of mangrove sediment was screened to identify strains with high production of PDO by fermentation of glycerol. The PDO productivities of the isolated strains were tested, and the strain with highest PDO productivity was characterized using the API20E and 16-s rRNA sequence analysis. The physiological and phylogenetic analysis indicated that the strain was closed related to K. pneumoniae species and was named as K. pneumoniae HSL4. The structure of the dha cluster which was responsible for the biosynthesis of PDO was analyzed. It is observed that K. pneumoniae HSL4 was tolerant to salt and partly tolerant to acetate and lactate, which will favor industrial applications. Fed-batch fermentation experiments revealed K. pneumoniae HSL4 exhibited an excellent ability to produce PDO with high concentration （80.08 g L^-1）, productivity （2.22 g L^-1h^-1） and conversion （0.435 g g^-1 or 0.53 mol mol^-1）. The metabolic flux profile illuminated that glycerol was consumed rapidly and PDO was accumulated quickly to a high level during the exponential growth phase. This study provided important information for further fermentation and metabolic engineering of PDO production by K. pneumoniae HSL4.

Interfacial synergism of hollow mesoporous Pt/WO_(x)/SiO_(2)-TiO_(2)catalysts enable highly selective hydrogenolysis of glycerol to 1,3-propanediol

The selective hydrogenolysis of glycerol exhibits great prospects,while the catalysts with high selectivity and activity are still missing and need to be created urgently.Herein,we report the synthesis of hollow mesoporous Pt/WO_(x)/SiO_(2)-TiO_(2)nanosphere catalysts with bi-functional interfaces synergistically for high efficiency conversion of glycerol to 1,3-propanediol.The hollow mesoporous Pt/WO_(x)/SiO_(2)-TiO_(2)catalysts show a typical brick-concrete liked framework with a high surface area(179.3 m^(2)·g^(-1)),large mesopore size(10.6 nm),uniform particle size(~400 nm),and ultrathin shell thickness(~75 nm).The brick anatase nanocrystals and concrete amorphous SiO_(2)networks can selectively rivet Pt nanoparticles and WO_(x)nanocluster species,respectively,thus constructing two interfaces for effective adsorption,rapidly catalytic dehydration and hydrogenation processes.The hollow mesoporous Pt/WO_(x)/SiO_(2)-TiO_(2)catalysts deliver a high selectivity of 53.8%for 1,3-propanediol(1,3-PDO)at a very high glycerol conversion of 85.0%.As a result,a favorable 1,3-PDO yield of 45.7%can be obtained with excellent stability,which is among the best performances of previously reported catalysts.This work paves a new way to synthesize catalysts with high selectivity,high activity and high stability.

Highly efficient fermentation of glycerol and 1,3-propanediol using a novel starch as feedstock

As a potential cost-effective feedstock for highly efficient fermentation of glycerol and its downstream product 1,3-propanediol(1,3-PD),duckweed starch was characterized and used for glycerol fermentation,for the first time,in this study.Genes involved in glycerol biosynthesis(gpd1 and gpp2)were overexpressed in Escherichia coli,and genes involved in glycerol catabolism(glpK and gldA)were disrupted,which led to significantly decreased residual sugar levels and dramatically increased glycerol production.The maximum glycerol concentration in fed-batch fermentation reached 102.72 g L^(-1) at 28 h,and the glycerol productivity was 3.67 g L^(-1) h^(-1),which,to our knowledge,is the highest productivity thus far reported.Subsequently,glycerol broth was fermented into 1,3-PD by Klebsiella pneumoniae.The concentration,conversion rate and productivity of 1,3-PD reached 35.54 g L^(-1),40.28%and 0.89 g L^(-1) h^(-1),respectively,without optimization.In summary,the duckweed starch-to-glycerol-to-1,3-PD process is feasible and shows potential for improving glycerol industry competitiveness.

Understanding the deactivation behavior of Pt/WO3/Al2O3 catalyst in the glycerol hydrogenolysis reaction

The selective hydrogenolysis of glycerol to 1,3-propanediol is a highly important reaction for both improving the profitability of biodiesel and valorization of biomass.While intensive research efforts have been devoted to enhancing the catalytic activity and selectivity,little is focused on the stability although the latter is of paramount importance to practical applications.In this work,we investigated the stability of Pt/WO3/Al2O3 and observed a continuous deactivation trend during a 700 h time-on-stream run.Neither the leaching of active W nor the coking was responsible for the deactivation.Instead,XRD,HAADF-STEM and CO chemisorption results clearly showed the occurrence of significant aggregation of Pt particles,which caused a remarkable decrease of Pt-WOx interfacial sites.As a consequence,strong Br?nsted acid sites which were in situ formed by H2 dissociation at the Pt-WOx interfacial sites were reduced,leading to the deactivation of the catalyst.

Stannous-acetylacetonate:A new catalyst for poly(trimethylene terephthalate) synthesis

Stannous-acetylacetonate was prepared efficiently and characterized by ^1H NMR and FT-IR. Its catalytic activity for poly（trimethylene terephthalate） （PTT） synthesis was investigated. By this catalyst, the degree of esterification of pure terephthalic acid was up to 91.7% after reaction at 260 ℃ for 2 h, while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polymerized at 260 ℃, 60 Pa for 2 h was 0.8816 dL/g and 17 mol/t,respectively. Stannous-acetylacetonate was more active and promising than tetrabutyl titanate and stannous octoate for PTT synthesis.

Tetra(acetylacetonato) tin(Ⅳ) as new catalyst for polytrimethylene terephthalate synthesis

Chelate tetra(acetylacetonato) tin(Ⅳ) was prepared and used as catalyst for polytrimethylene terephthalate synthesis.It exhibited higher catalytic activity than tetrabutyl titanate,butyltinhydroxide oxide and dibutyltin oxide.Decrease in reaction time, content of terminal carboxyl group,color intensity and increase in intrinsic viscosity were observed.The unique molecular structure can be considered as factor remarkably improving the catalytic activity of tetra(acetylacetonato) tin(Ⅳ).