不同加热温度下电加热不燃烧卷烟烟气释放特性研究

[目的]研究加热温度对电加热不燃烧卷烟烟气释放特性的影响。[方法]采用气相色谱仪、质谱仪及电加热不燃烧卷烟模拟装置系统等,对电加热不燃烧卷烟在不同加热温度下的烟气成分以及烟气中粒相物、甘油/丙二醇、烟碱等释放特性进行分析。[结果]200～470℃时,随着加热温度升高,电加热不燃烧卷烟烟气成分增加,有害成分的释放量增加; 260～320℃时,随着加热温度升高,烟气中甘油/丙二醇含量明显增加; 350～470℃时,随着加热温度升高,烟气中粒相物含量明显增加;低于260℃时,烟碱迁移率随温度升高而增加;当温度高于260℃时,烟碱迁移率增加速度减小。[结论]该研究为电加热不燃烧卷烟的开发提供依据。

Urchin-like CoCu Bimetallic Nanocomposites for Catalytic Hydrogenolysis of Glycerol to Propanediols

Bimetallic CoCu nanocomposites were synthesized in polyol by using Ru as heterogeneous nucleation agent and stearic acid as surfactant, and their catalytic properties were investi- gated by hydrogenolysis of glycerol to propanediols. It was found that the surfactant could induce Co nanocrystals to form nanowires as structure-directing agent, while it＇s ineffective for Cu because only spherical Cu particles were produced under the same condition. When Co2＋ and Cu2＋ coexist in polyol, Cu2＋ is firstly reduced and forms the spherical particles, and then the Cu particles afford surface for the subsequential reduction of Co2＋ and growth of Co nanocrystals to form the nanorods, obtaining the urchin-like CoCu nanocomposites. The catalytic performance in selective hydrogenolysis of glycerol to propanediols proposed that the CoCu urchin-like nanocomposites was superior to the Co nanowires possibly due to that the synergistic effect between Co and Cu component promoted conversion of glyc- erol and obtained the higher propanediol yields based on the specific surface areas of the catalysts.

Alcohol-treated SiO_2 as the support of Ir-Re/SiO_2 catalysts for glycerol hydrogenolysis

The surface of SiO2 support was pretreated by C1-C4 normal alcohols before the impregnation of iridium and rhenium precursors.These catalysts were applied in high concentration glycerol aqueous solution hydrogenolysis.The catalysts prepared from the pretreated supports exhibited high catalytic activity because of the formation of more active sites from a high dispersion of iridium oxide and rhenium oxide.The catalysts with the support pretreated by 1-propanol showed the highest glycerol conversion of 59.5%.The supports and catalysts were characterized by FT-IR,nitrogen adsorption,TPR,XRD,TEM,H2-chemisorption and NH3-TPD.

Pt/Nb‐WO_x for the chemoselective hydrogenolysis of glycerol to 1,3‐propanediol: Nb dopant pacifying the over‐reduction of WO_x supports

Selective hydrogenolysis of glycerol to 1,3‐propanediol（1,3‐PD） is an important yet challenging method for the transformation of biomass into value‐added chemicals due to steric hindrance and unfavorable thermodynamics. In previous studies, chemoselective performances were found de‐manding and sensitive to H2 pressure. In this regard, we manipulate the chemical/physical charac‐teristics of the catalyst supports via doping Nb into WOx and prepared 1D needle‐, 2D flake‐, and 3D sphere‐stack mesoporous structured Nb‐WOx with increased surface acid sites. Moreover, Nb dop‐ing can successfully inhibit the over‐reduction of active W species during glycerol hydrogenolysis and substantially broaden the optimal H2 pressure from 1 to 5 MPa. When Nb doping is 2%, sup‐ported Pt catalysts showed promising performance for the selective hydrogenolysis of glycerol to 1,3‐PD over an unprecedentedly wide H2 pressure range, which will guarantee better catalyst sta‐bility in the long run, as well as expand their applications to other hydrogen‐related reactions.

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.

Effect of promoters on the selective hydrogenolysis of glycerol over Pt/W-containing catalysts

Diverse promoters,including noble metals（such as Ru,Ir and Rh） and transition metal oxides（such as Re,La,Fe,Zr,Sn and Ce oxides） were introduced into Pt/WOx and Pt/WOx/Al2O3 catalysts to investigate the ability of these promoters to modify activity and selectivity during glycerol hydrogenolysis to 1,3-propanediol.Among these,La exhibited the greatest promotional effect;the introduction of 0.1% La to the Pt/WOx improved activity,selectivity and stability,although the significant increase in selectivity came at the cost of a slight activity loss in the case of the Pt/WOx/Al2O3 catalyst.Transmission electron microscopy,high angle annular dark field scanning tunneling electron microscopy and NH3-temperature programmed desorption all demonstrated that the introduction of La generates a greater quantity of acidic sites on the catalyst surface,and that the majority of the La species are associated with Pt particles.Most of the other additives resulted in only minimal improvements or even detrimental effects with regard to both activity and selectivity,although some appear to improve the stability of the catalyst.

Selective hydrogenolysis of glycerol to 1,3-propanediol over Pt-W based catalysts

The selective hydrogenolysis of glycerol to 1,3-propanediol(1,3-PDO)is an attractive reaction due to the high demand for valorization of huge excess amounts of glycerol supply as well as the important application of 1,3-PDO in polyester industry.Nevertheless,the formation of 1,3-PDO is thermodynamically less favorable than 1,2-PDO,which necessitates the development of efficient catalysts to manipulate the reaction kinetics towards the 1,3-PDO formation.Among others,Pt-W based catalysts have shown promising activities and selectivities of 1,3-PDO although the reaction mechanism is not well addressed at the molecular level.In this short review,we have compared the performances of different Pt-W based catalysts and discussed the key factors influencing the activity and selectivity.Three possible reaction mechanisms have been discussed in terms of the synergy between Pt and WO_x and the origin of acid sites.Finally,the long-term stability of the Pt-W catalysts has been discussed.We hope this review will provide useful information for the development of more efficient catalysts for this important reaction.

Understanding the promotional effect of Au on Pt/WO_3 in hydrogenolysis of glycerol to 1,3-propanediol

Pt/Au/WO_3 bimetallic catalysts were prepared by impregnation of Pt onto preformed Au/WO_3,obtained by a hexadecyl trmethyl ammonium bromide（CTAB）-assisted one-pot synthesis method.The resulting Pt/Au/WO_3 catalysts exhibited remarkable synergistic effects for selective hydrogenolysis of glycerol to 1,3-propanediol. The characterization results showed that doping of Au promoted the reduction of both Pt and W at low temperatures and uniform dispersion of Pt on the WO_3 support. Furthermore, more low-valence Pt species were produced on the WO_3 surface after introduction of Au. These changes in electronic properties resulted in enhancement of both glycerol conversion and selectivity for 1,3-propanediol.

Optimizing Control of Bio-dissimilation Process of Glycerol to 1,3-Propanedlol

An iterative optimization strategy is proposed and applied to the steady state optimizing control of the bio-dissimilation process of glycerol to 1,3-propanediol in the presence of model-plant mismatch and input constraints. The scheme is based on the Augmented Integrated System Optimization and Parameter Estimation （AI- SOPE） technique, but a linearization of some performance function in the modified model-based optimization problem of AISOPE is introduced to overcome the difficulty of determining an appropriate penalty parameter. When carrying out the iterative optimization, the penalty coefficient is set to a larger value at the current iteration than at the previous iteration, which can promote the evolution rate of the iterative optimization. Simulation studies illustrate the potential ofthe approach presented for the optimizing control of the bioTdissimilation process of glycerol to 1,3-propanediol. The effects of measurement noise, measured and unmeasured disturbances on the proposed algorithm are also investigated.

Kinetics of Hydrogenolysis of Glycerol to Propylene Glycol over Cu-ZnO-Al2O3 Catalysts

A series of Cu-ZnO-Al2O3 catalysts with various metal compositions of Cu/Zn/Al were prepared by the co-precipitation method,and screened for glycerol hydrogenolysis to propylene glycol.The catalyst with a Cu/Zn/Al molar ratio of 1:1:0.5 exhibited the best performance for glycerol hydrogenolysis,and thus selected for kinetic investigation.Under elimination of external and internal diffusion limitation,kinetic experiments were performed in an isothermal fixed-bed reactor at a hydrogen pressure range of 3.0-5.0 MPa and a temperature range of 493-513 K. Based on a dehydration-hydrogenation two-step hydrogenolysis mechanism,a two-site Langmuir-Hinshelwood kinetic model taking into account competitive adsorption of glycerol,acetol and propylene glycol was proposed and successfully fitted to the experimental data.The average relative errors between observed and predicted outlet concentrations of glycerol and propylene glycol were 6.3%and 7.6%,respectively.The kinetic and adsorption parameters were estimated by using the fourth-order Runge-Kutta method together with the Rosenbrock algorithm.The activation energies for dehydration and hydrogenation reactions were 86.56 and 57.80 kJ·mol-1,respectively.