Efficient conversion of monosaccharides into 5-hydroxymethylfurfural and levulinic acid in InCl3–H2O medium

The conversion of fructose into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) was investigated and catalyzed by indium trichloride (InCl₃) in water. 79% 5-HMF yield (15 min) and 45% LA yield (60 min) were obtained at 180 °C with 2.5 mol% InCl₃. Additionally, comparative studies of glucose/fructose mixture with different ratios as substrates were carried out to manifest the isomerization process between glucose and fructose during the conversion of monosaccharides into chemicals. It was shown that InCl₃ was not only active in the isomerization of glucose to fructose and the reverse direction, but also demonstrated an excellent activity in the dehydration and conversion of monosaccharides. InCl₃–H₂O system presented a remarkable catalytic effect on the dehydration and conversion of monosaccharides.     

微波协同氧化锆@碳纳米管强化果糖制5-羟甲基糠醛

糖类催化转化是生产生物质基燃料和高附加值化学品的重要途径,而微波能量的使用可使这一过程更具商业可行性。本文探究了微波辐射下微波响应型催化剂碳纳米管负载氧化锆［ZrO₂/MWCNTs(C)］催化的果糖高效分解制5-羟甲基糠醛（5-HMF）过程。首先,采用水热法制备了性能优异的氧化锆@碳纳米管催化剂,并对其进行表征;进一步考察了催化剂用量、果糖浓度、反应温度和反应时间对反应产物5-HMF收率的影响,并通过调节各组分在反应过程中的实际含量,探究微波强化的作用机理。研究结果表明在相对温和的条件下（120℃、常压）,微波辐射下的5-HMF收率（约74%）远高于常规加热条件下的5-HMF收率（约31%）;采用最佳ZrO₂60/CNTs用量（ZrO₂质量分数约为60%）,微波场中,140℃常压条件下反应10min,可以实现约98%的果糖转化率和92%的5-HMF收率。通过探究载体吸波性能与活性位点催化性能之间的耦合匹配关系,揭示了微波协同催化过程强化机理归因于具有强吸波性能碳质载体的选择性加热和活性位点ZrO₂之间的协同耦合作用。     

绿色溶剂γ-戊内酯中果糖催化转化为5-羟甲基糠醛

通过生物质衍生糖的酸催化转化制备生物质基平台化合物5-羟甲基糠醛受到关注。常用又有效的溶剂包括离子液体和二甲基亚砜等,但这些溶剂黏度高,易造成空气污染。以γ-戊内酯作为溶剂,研究果糖催化转化为5-羟甲基糠醛的绿色过程,系统研究酸催化剂种类、反应温度、催化剂用量、果糖初始浓度及底物种类等对5-羟甲基糠醛产率的影响。通过反应条件的优化,以HCl溶液为催化剂,在果糖初始质量浓度2%、反应温度100℃和反应时间30 min条件下,5-羟甲基糠醛产率为93.5%。5-羟甲基糠醛产率随果糖初始添加量的增加而呈下降趋势,但果糖初始质量浓度为10%时,5-羟甲基糠醛产率仍保持约90%,表明γ-戊内酯是一种将果糖催化转化为5-羟甲基糠醛的优良绿色溶剂。     

Microwave-assisted epoxidation of styrene with molecular O2 over sulfated Co–Y–ZrO2 solid catalyst

The microwave-assisted styrene epoxidation reaction with molecular O₂ as an oxidant was studied over a sulfated Co–Y-doped ZrO₂ solid catalyst. The microwave irradiation (400 W) resulted in similar styrene conversion and styrene oxide selectivity, in reduced time, as compared to conventional thermal heating. Higher power (800 W) of microwave irradiation decreased the styrene oxide selectivity as well as leading to the formation of styrene glycol. DMF was found to be the most suitable solvent for epoxidation of styrene with molecular O₂ under microwave irradiation and yielded maximum oxide selectivity (91%) at 120 °C. The microwave-assisted oxidation reaction resulted in time saving and is energy conserving method.     

Dehydration of Glucose to 5-Hydroxymethylfurfural Using Combined Catalysts in Ionic Liquid by Microwave Heating

The dehydration of glucose into 5-hydroxymethylfurfural (HMF) was catalyzed by NKC-9 (a macroporous sulfonated polystyrene ion-exchange resin) combined with metal oxides (TiO₂, ZrO₂, Al₂O₃ calcined at different temperatures). In the combined catalytic system, Al₂O₃ calcined at 550°C exhibited excellent catalytic activity, when the dosage of NKC-9 was kept constant. Four parameters (catalyst dosage, reaction temperature, reaction time, and initial glucose amount) were optimized by employing response surface methodology (RSM), with HMF yield as the response parameter. The maximum HMF yield of 62.09% was obtained at catalyst 0.07 g, temperature 140°C, time 20 min, and glucose 0.01 g. The catalytic activity of the binary catalyst (NKC-9 and Al₂O₃) for the conversion of glucose into HMF did not show significant decrease after five-times uses at 140°C for 20 min.     

Preparation of TiO2-pillared montmorillonite as photocatalyst Part I. Microwave calcination, characterisation, and adsorption of a textile azo dye

Two photocatalysts based on TiO₂-pillared intercalated montmorillonite have been prepared by microwave for 10 min at 700 W or by furnace heating at 673 K. Montmorillonite pillaring with TiO₂ increased the basal spacing to 14.7 Å (conventional heating) and 17.6 Å (microwave heating). XRD patterns of both materials showed the presence of 100% anatase with a slightly higher rate of crystallinity obtained through microwave calcination than by conventional heating at 673 K. The BET specific surface area of the microwave prepared photocatalyst (151 m² g^− 1) was 3 fold higher than those of the Degussa TiO₂ P25. At pH = 5.8, the maximum adsorption capacity of Solophenyl red 3BL (a textile azo dye) on the TiO₂-pillared montmorillonite calcined by microwave was 185 mg g^− 1, whereas it was 1.4 and 3 fold lower on the TiO₂-pillared montmorillonite calcined at 673 K, and on the Degussa TiO₂ P25 respectively. The influence of pH on the adsorption of the dye depended on the pH_ZPC of the pillared montmorillonites.     

Microwave-assisted base-free oxidation of glucose on gold nanoparticle catalysts

Base-free oxidation of glucose to gluconic acid with supported gold catalysts was studied using microwave heating. High conversion and selectivity were obtained in a remarkably shortened reaction time; in 10 min gluconic acid was obtained with up to 76% yields with 0.09 mol% Au/Al₂O₃ and hydrogen peroxide as oxidant. Very high turn-over frequencies over 10,000 h^− 1 were measured for the microwave assisted oxidation. Moreover, the catalyst activity remained constant in four consecutive runs, even though minor particle growth was observed.     

碱性离子液体催化单糖脱水制5-羟甲基糠醛

离子液体作为一种新型的环境友好溶剂和液体酸碱催化剂用于单糖脱水制备5-羟甲基糠醛日益成为研究热点,受到广泛重视。以典型的OH-为阴离子的碱性离子液体为催化剂,研究了其对果糖/葡萄糖转化为5-羟甲基糠醛反应的影响。结果表明,在二甲基亚砜中,160℃反应6 h,果糖转化率达90.4%,5-羟甲基糠醛收率为83.3%,5-羟甲基糠醛选择性为92.1%。这一新的碱性离子液体催化单糖脱水的体系,取代了传统酸性催化剂的使用,具有高效、环保、经济的特点,为5-HMF规模化生产奠定了基础。     

Dielectric,mechanical and thermal properties of ZrO2–TiO2 materials obtained by microwave sintering at low temperature

The sinterability of 3Y-TZP/TiO₂ materials using micrometre-sized ZrO₂ and nanometre-sized TiO₂ (16 wt%) by one-step fast microwave sintering at low temperature (1200–1300 °C) was investigated. Firstly, in situ detailed analysis of the dielectric properties of the material with temperature was carried out in order to measure the capacity of the material to transform microwave energy into heat. Another related parameter associated to microwave sintering is the penetration depth of the microwave radiation into the material, which showed great homogeneity from 400 °C. Secondly, the effect of sintering conditions on microstructure, density, hardness and coefficient of thermal expansion was evaluated. The X-ray diffraction study and microstructural characterization demonstrate that it is possible to obtain fully dense pieces (>99%) by microwave sintering, a condition yielding to a coarse-grained (~1–2 μm), quite hard (~13.7 GPa) 3Y-TZP/TiO₂ material. However, the most important feature is the significant reduction of the thermal expansion coefficient (8·10⁻⁶ K⁻¹) as compared to that of 3Y-TZP. In addition, the results from conventional sintering at 1400–1500 °C with 2 and 6 h of dwell time are examined and compared. The materials obtained at 1500 °C showed high density with grain size and hardness similar to those obtained by microwave but with a dramatic difference in the power consumption of the sintering cycle, since the materials obtained by microwave used a maximum absorbed power of 120 W and a heating cycle of only 40 min.     

Study on drying kinetics of calcium oxide doped zirconia by microwave-assisted drying

Ca–ZrO₂ is an essential structural and functional material, which is commonly used in refractories, electronic ceramics, and functional ceramics. The properties of Ca–ZrO₂ materials are depending on the quality of Ca–ZrO₂ powders. The main factors affecting the quality of powder are sintering temperature and the drying effect. This paper applied modern microwave drying technology to dry Ca–ZrO₂ powder. The impact of initial mass, microwave heating power, and initial moisture content on the drying of Ca–ZrO₂ were explored. The results showed that the average drying rate increased with the rise of initial mass, microwave heating power, and initial moisture content. Wang and Singh, Page, and Quadratic Model were applied to fit Ca–ZrO₂ with an initial moisture content of 5.6%, mass of 30 g, and microwave output power of 400 W. The results displayed that the Page model had a better fitting effect. It was also applicable to other different initial moisture content, original mass, and microwave heating power. The diffusion coefficient calculated by Fick's second law displayed that with the increase of initial mass, initial moisture content, and microwave heating power of Ca–ZrO₂, the effective diffusion coefficient increased first and then declined. When the Ca–ZrO₂ of microwave heating power was 640 W, mass was 30 g, and the moisture content was 5.65%, the effective diffusion coefficients of zirconia were 1.42533 × 10^?13, 2.91806 × 10^?13, 5.652.2471 × 10^?13 m²/s, respectively. To determine the activation energy of microwave dried zirconia, using the relationship between microwave power and activation energy, the activation energy of microwave dried zirconia was calculated to be ?23.39 g/W. This paper aims to rich experimental data for the industrial application of microwaves to strengthen dried zirconia and propose a theoretical basis.     

The excellent performance of amorphous Cr2O3, SnO2, SrO and graphene oxide–ferric oxide in glucose conversion into 5-HMF

Amorphous Cr₂O₃, SnO₂ and SrO presented an excellent performance in the conversion of glucose to 5-hydroxymethylfurfural (5-HMF), and 5-HMF yields achieved 84%, 81% and 99%, however, the calcined metal oxides almost completely lost the catalytic activities. Although Fe₂O₃ exhibited very poor catalytic activity, the graphene oxide–Fe₂O₃ (GO–Fe₂O₃) displayed a better performance in catalytic glucose conversion to 5-HMF (86% yield) in 1-ethyl-3-methylimidazolium bromide ([EMIM]Br). The plausible mechanisms of glucose conversion to 5-HMF over amorphous Cr₂O₃, SnO₂, SrO and GO–Fe₂O₃ were proposed.     

Synthesis of bio-additives: Acetylation of glycerol over zirconia-based solid acid catalysts

Acetylation of glycerol with acetic acid was investigated over ZrO₂, TiO₂–ZrO₂, WO_x/TiO₂–ZrO₂ and MoO_x/TiO₂–ZrO₂ solid acid catalysts to synthesize monoacetin, diacetin and triacetin having interesting applications as bio-additives for petroleum fuels. The prepared catalysts were characterized by means of XRD, BET surface area, ammonia-TPD and FT-Raman techniques. The effect of various parameters such as reaction temperature, molar ratio of acetic acid to glycerol, catalyst wt.% and time-on-stream were studied to optimize the reaction conditions. Among various catalysts investigated, the MoO_x/TiO₂–ZrO₂ combination exhibited highest conversion (~ 100%) with best product selectivity, and a high time-on-stream stability.     

Selective conversion of dihydroxyacetone–ethanol mixture into ethyl lactate over amphoteric ZrO2–TiO2 catalyst

The conversion of dihydroxyacetone in ethanol solution into ethyl lactate over several acidic and amphoteric oxides at 100–160 °C was studied. The formation of ethyl lactate with 80–90% selectivity was observed on amphoteric ZrO₂–TiO₂ oxide whereas hemiacetal and acetal of pyruval were the main products obtained over the acidic ZrO₂–SiO₂ catalyst and Amberlyst 15. Amphoteric ZrO₂–3TiO₂ oxide provides 89% yield of ethyl lactate at 140 °C and 1.0 MPa under the feed rate of 4 mmol C₃H₆O₃/g_cat/h.     

Utilization of carbon dioxide as soft oxidant for oxydehydrogenation of ethylbenzene to styrene over V2O5–CeO2/TiO2–ZrO2 catalyst

Vanadium oxide and cerium oxide doped titania–zirconia mixed oxides were explored for oxidative dehydrogenation of ethylbenzene to styrene utilizing carbon dioxide as a soft oxidant. The investigated TiO₂–ZrO₂ mixed oxide support with high specific surface area (207 m² g⁻¹) was synthesized by a coprecipitation method. Over the calcined support (550 °C), a monolayer equivalent (15 wt.%) of V₂O₅, CeO₂ or a combination of both were deposited by using wet-impregnation or co-impregnation methods to make the V₂O₅/TiO₂–ZrO₂, CeO₂/TiO₂–ZrO₂ and V₂O₅–CeO₂/TiO₂–ZrO₂ combination catalysts, respectively. These catalysts were characterized using X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature preprogrammed reduction (TPR), CO₂ temperature preprogrammed desorption (TPD) and BET surface area methods. All characterization studies revealed that the deposited promoter oxides are in a highly dispersed form over the support, and the combined acid–base and redox properties of the catalysts play a major role in this reaction. The V₂O₅–CeO₂/TiO₂–ZrO₂ catalyst exhibited a better conversion and product selectivity than other combinations. In particular, the addition of CeO₂ to V₂O₅/TiO₂–ZrO₂ prevented catalyst deactivation and helped to maintain a high and stable catalytic activity.     

Hydrothermal conversion of glucose in multiscale batch processes. Analysis of the gas,liquid and solid residues

Hydrothermal conversion is an interesting process to transform (very) humid biomass into high energy vectors or valuable products in the liquid or solid state. In the supercritical domain, water becomes a solvent for organics as well as a reactant, and thus the cellulosic content is effectively hydrolyzed into glucose, largely considered as its model molecule.The kinetics of glucose decomposition during the heating step in the batch reactor were investigated through the analysis of glucose concentration. Glucose reacts totally before reaching the supercritical point of water. Among the operating parameters that influence supercritical water gasification, this paper presents only the effect of reaction temperature through gas composition, liquid carbon content and structure of the solid. Glucose gasification in a batch process (5 wt% glucose, 0.5 wt% catalyst, 600 °C, 25 MPa, 60 min) produced 1.5 mol of hydrogen per mol of glucose. The gas has energetic properties (H₂, CH₄, C₂H₆) while the liquid contains substances that could be used as platform molecules (5-HMF). The solid phase is composed of carbon (almost pure) in two distinct phases: spherical nanoparticles and an amorphous phase.     

Effect of 24 GHz microwave heating on creep deformation of yttria partially stabilised zirconia ceramics with titania and tin oxide additives

The effect of quasi-millimetre-wave (24 GHz microwave) heating on creep deformation was investigated on partially-stabilised zirconia through tensile testing at temperatures from 1100 to 1350 °C over stresses from 3 to 10 MPa. The specimens were fabricated by sintering the 3 mol% of yttria stabilised ZrO₂ (3YSZ) powder dispersed with SiO₂, SiO₂/SnO₂ or SiO₂/TiO₂ at 1600 °C. In tensile test using the quasi-millimetre wave heating, strain rates of SiO₂ dispersed 3YSZ were similar to that with a conventional furnace heating. The 3YSZ sample containing the TiO₂ addition exhibited a different strain rate when heated by millimeter-wave irradiation as against conventional furnace heating, it is proposed that this difference can be explained due to TiO₂ having a high-dielectric constant resulting in a non-thermal effect when subjected to quasi-millimeter wavelength radiation.     

Steam Reforming of Glycerin Using Ni-based Catalysts Loaded on CaO–ZrO2 Solid Solution

Abstract  

Steam reforming of glycerin on Ni-loaded catalyst was performed using a ZrO₂-based support material. The addition of CaO to ZrO₂ improved the catalyst performance, and NiO/CaO–ZrO₂ afforded glycerin conversion of 88.9% with an H₂ yield of 75.3% at 600 °C. Carbon formation decreased from 4.2 to 2.0% with CaO-added catalyst. Solid solution was formed with the addition of CaO to ZrO₂, and it exhibited basic characteristics. Further reduction of carbon formation during the reforming reaction was achieved by using a quaternary complex oxide catalyst NiO–CeO₂/CaO–ZrO₂, where glycerin conversion of 96.1% and a H₂ yield of 83.7% were achieved with carbon formation of 0.7% at 600 °C.     

芬顿试剂催化糖类制备5-羟甲基糠醛

研究了在水-正丁醇双相体系中,芬顿试剂催化转化淀粉、葡萄糖和果糖为5-羟甲基糠醛（5-HMF）的反应。考察了多种影响因素,包括反应温度、反应时间、水和正丁醇比例、芬顿试剂（Fe²⁺和H₂O₂）比例,淀粉、葡萄糖和果糖为底物的5-HMF最高收率分别达到46.5%、47.4%和61.7%。探讨了芬顿试剂催化糖类制备5-HMF的作用机理,即芬顿试剂可以降解淀粉为葡萄糖,催化葡萄糖异构化为果糖,催化果糖生成5-HMF。     

High selective production of 5-hydroymethylfurfural from fructose by a solid heteropolyacid catalyst

A clean, facile, economical, and environmental friendly method for converting fructose into 5-hydroymethylfurfural (HMF) has been developed, in the presence of a solid heteropolyacid Cs_2.5H_0.5PW₁₂O₄₀ catalyst in a biphasic system. A 5-HMF yield of 74.0% and a higher selectivity of 94.7% were obtained in 60 min at 388 K. More importance is that this catalyst is tolerant to high concentration feedstocks (50 wt.% fructose) and it can be recycled.     

Fabrication and characterization of porous ZrO2 with a high volume fraction of fine closed pores

A novel technique for the fabrication of porous ZrO₂ with a high volume fraction of fine closed pores was investigated. A partially stabilized ZrO₂ (3 mol% Y₂O₃; Y-PSZ) body, with a 97–99% relative density and containing a small amount of impurities, exhibited a large volume expansion related to the formation of closed pores after heating at 1700 °C for 10 min in N₂. These closed pores seemed to mainly form due to the vaporization of hydroxyl apatite: Ca₁₀(OH)₂(PO₄)₆ as an impurity and superplasticity of the ZrO₂ during heating. Porous ZrO₂ with approximately 24.6% closed pores (total porosity: 26.7%) was successfully fabricated by the addition of 1 mass% SiO₂, 1 mass% TiO₂, and 1 mass% hydroxyl apatite. The closed pore size and morphology of the resultant porous ZrO₂ bodies were investigated, and the formation mechanism of the closed pores was examined on the basis of chemical thermodynamics.