Effective conversion of cellobiose and glucose to sorbitol using non-noble bimetallic NiCo/HZSM-5 catalyst

The tandem hydrolysis and hydrogenation of saccharides into sorbitol is an especially attractive reaction in the conversion of biomass. Here, an economical and efficient bimetallic catalyst for the transformation of glucose and cellobiose into sorbitol is reported. Non-precious metal based catalysts such as NiCo, Ni, and Co, were prepared via modified impregnation method, and NiCo/HZSM-5 showed superior performance for the synthesis of sorbitol (86.9% from cellobiose, 98.6% from D-glucose). Various characterizations, such as Brunner-Emmet-Teler (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), confirmed that NiCo alloy formed and highly dispersed in NiCo/HZSM-5 catalyst. The high performance of fabricated catalyst would be attributed to the formation of nickel-cobalt alloy over HZSM-5 zeolite surface. High temperature and H₂ pressure were favorable for the tandem hydrolysis and hydrogenation reaction. Besides, the reaction pathway was also proposed based on the kinetics study. Cellobitol was detected as the intermediate in the reaction mixture. Furthermore, in the catalytic stability study, it was found that active metal species of NiCo/HZSM-5 were stable. The deactivation of catalyst would be due to the covering of acidic sites over NiCo/HZSM-5.     

Catalytic cracking of polyethylene over nanocrystalline HZSM-5: Catalyst deactivation and regeneration study

In this work, catalytic cracking of low density polyethylene (LDPE) over nanocrystalline HZSM-5 zeolite in a batch reactor at 340 °C was carried out with the aim of study both the catalyst resistance to deactivation and the catalyst regeneration process. For looking into the catalyst deactivation, consecutive polyethylene cracking experiments were carried out. Subsequently, the same reactions has been also performed but by regenerating the zeolite after each experiment by promoting coke combustion at 550 °C under air flow. Zeolites used were two samples of nanocrystalline HZSM-5 with very different textural properties (sample A, with most of its surface corresponding to zeolitic micropores and sample B with a considerable amount of external surface, mesopores and super-micropores) in order to study the effect of their textural properties in the deactivation and regeneration experiments. Although conversion and activity values reached over both samples are quite high taking into account the mild conditions used, sample B shows a very much higher initial activity than A due to its improved textural properties. In both samples two different deactivation mechanisms occur: a reversible deactivation by coke deposition removable by the regeneration procedure, and an irreversible or permanent deactivation by other factors. Deactivation of sample B occurs faster due to the higher amount of coke deposited on this material. However, the improved textural properties of this catalyst supposes an advantage for the regeneration process, since coke deposited either on the external surface or on the super-micropores and mesopores, makes easier the regeneration procedure.     

Catalytic cracking of polyethylene waste in horizontal tube reactor

In this study catalytic and thermal cracking of polyethylene waste were investigated in continued tube reactor system. HZSM-5 and equilibrium FCC type catalysts were tested. Both the resistance to deactivation and the regeneration process of the catalyst were studied. Reaction temperature of 545 °C and residence time of 20 min were used during the cracking treatment. The reaction products were analyzed and the textural properties of catalysts were also determined. It was found that after the first reaction run the FCC catalyst lost 75% of its cracking activity, in case of HZSM-5 the rate of deactivation was higher. The cracking activity of catalyst could be improved by regeneration process with only 2-3% compared to the coked catalyst. The isomerisation effect of the catalysts was also observed. The effect of coked FCC catalyst could be improved by the regeneration process with 50% in case of HZSM-5 it was only 25%.     

HZSM-5在线提质生物油及催化剂失活机理分析

对不同使用时间的HZSM-5分子筛在线催化提质制取的生物油进行理化特性和成分分析,从生物油品质角度对HZSM-5的催化性能进行评价;并采用TG、BET、XRD、SEM和TEM等方法对失活的HZSM-5催化剂进行表征分析,探讨了HZSM-5催化提质生物油的失活机理,并进行再生研究。研究表明,HZSM-5分子筛可转化生物油中的酸类、醛类和酮类等"非期望"有机物,生成较多"期望"有机物,如酚类和芳烃类物质,降低生物油的氧含量及酸性,提高生物油的热值;HZSM-5使用80 min后,生物油品质明显变差,催化剂活性明显降低;失活催化剂上沉积的焦炭主要呈纤维状,同时,还存在少量石墨状焦炭,焦炭总量达14.12%,且使用过程中催化剂的比表面积和孔容均下降,晶粒的团聚现象加剧,结晶度下降;在催化提质过程中,在孔道内生成的石墨状焦炭及在表面形成的纤维状焦炭大量覆盖活性位点,使得催化剂失活。经550℃再生后,催化剂可恢复催化性能。     

The catalytic activity of copper/nickel supported on mesoporous aluminum catalyst towards cyclohexene epoxidation in continuous reactor

The intent of the study is to attain a high selectivity rate and stable interaction between metals in any heterogeneous catalyst. Cyclohexene is extremely valuable in industrial domains such as the synthesis of perfumes and nylons, and the mesoporous alumina was upstretched with a various ratio of bimetal copper (10%) and nickel (5%, 10%, 15%, and 20%) under wet impregnation procedures by the mesoporous aluminum catalyst. This impregnation of a metal and catalyst was used to assess the highest conversion and selectivity of cyclohexene to cyclohexanol. This catalytic nature was validated by analyzing the crystal structure and size using the X-ray diffraction technique. The functional group is identified using FT-IR (Fourier Transform Infrared Spectroscopy), while the surface area is assessed using BET (Brunauer-Emmet-Teller). HR-TEM (transmission electron microscopy) is used to validate the morphology of catalysts and their surface layers; HR-SEM (Scanning Electron Microscopy) is used to highlight and assess microparticles; and NH₃TPD (Temperature-Programmed Desorption) is used to measure the overall acidity of the catalyst. The catalytic performance was proved by the yield achieved by varying parameters such as temperature, pressure, WHSV⁻¹, reaction time, and solvents, which yielded over 98.5% in both cyclohexene conversion and selectivity. In the conversion of the product, H₂O₂ performs as an oxidant, and acetonitrile serves as a solvent at constant mild conditions of 90 °C and 20 bar pressure. Furthermore, even after seven successive runs with the Al₂O₃/Cu (10%)-Ni (15%) mixture, remarkable reusability was attained despite a minor decline in cyclohexanol selectivity. The effective impregnation of copper and nickel into supported mesoporous Al₂O₃ produced a long-lasting, stable hybrid nanostructure with excellent stability and no metal leaching. The current synthesis protocol's advantages and qualities include its efficiency, cost-effectiveness, ecological sustainability, and comfort of synthesis with readily available components.     

Methane dehydro-aromatization over Mo/HZSM-5 catalysts in the absence of oxygen: Effect of steam-treatment on catalyst stability

The effect of steam-treatment to HZSM-5 zeolite and Mo/HZSM-5 with a steaming time range of 0.5-1 h on the catalytic performance of methane dehydro-aromatization (MDA) over Mo/HZSM-5 catalyst prepared with impregnation has been studied in detail in combination with the characterization of 1H MAS NMR technique. Both the deactivation rate constant (kd) and the Brnsted acid sites per unit cell were calculated to quantitatively evaluate the stability of Mo/HZSM-5 catalysts treated with steam at 813 K before and after impregnation of molybdenum species, and the corresponding variation of their Brnsted acid sites. The results reveal that a V-shape relationship between kd and the number of B1 acid sites per unit cell is presented on Mo/HZSM-5 catalyst under the tested steam-treatment and reaction conditions.     

Cobalt imine–pyridine–carbonyl complex functionalized metal–organic frameworks as catalysts for alkene epoxidation

Aerobic epoxidation of alkene is a green and economical route to produce epoxides. For such reaction, transition metal complexes exhibit favorable catalytic activity. In this work, NH₂-MIL-101, a stable metal–organic framework (MOF) material with large surface area and high pore volume, was functionalized with pyridine-2,6-dicarbaldehyde and Co(NO₃)₂, to realize the immobilization of Co(II) via imine–pyridine–carbonyl (N,N,O) tridentate ligands bonding to MOF skeleton. The modified materials were applied as heterogeneous catalysts for the aerobic epoxidation of cyclohexene at ambient temperature, and multiple factors were studied to explore their influences on catalytic effects. Under the optimal reaction conditions, satisfactory substrate conversion and epoxide selectivity were reached. In addition, this catalytic system is suitable for a variety of alkene substrates. Furthermore, recycle experiments and infrared spectroscopy characterization illustrated that the coordination surroundings of Co are altering smoothly during the reaction process, thus having an impact on the performance of catalyst.

     

The Modifiable Character of a Novel Ru-Fe-B/ZrO2 Catalyst for Benzene Selective Hydrogenation to Cyclohexene

A novel Ru‐Fe‐B/ZrO₂ catalyst for the selective hydrogenation of benzene to cyclohexene was prepared by the chemical reduction method. A yield of cyclohexene of 57.3% was achieved at benzene conversion of 80.6% on this catalyst. The activity and yield of cyclohexene were higher than those studied previously. The structural characterizations of the catalyst were performed by TEM‐SAED, XRD, and N₂‐physisorption. Moreover, cyclohexene selectivities on this catalyst increased and the activities decreased with the increase of the ZnO dosages, however, the activities increased and cyclohexene selectivities decreased with the increase of the H₂SO₄ dosages. Different feeding manners of H₂SO₄ or ZnO exerted definitely influence on the performances of this catalyst, but the degrees of influence were different due to the character of chemisorptions. Furthermore, the activity and cyclohexene selectivity on the catalysts could be reversibly modified by adding H₂SO₄ or ZnO into reaction slurry, which provides an easy method to recover the activity and selectivity of Ru‐Fe‐B/ZrO₂ catalysts during the process of producing cyclohexene. And the modifiable mechanisms involved were speculated.     

在Ni/HZSM-5催化剂上低温水蒸汽重整生物油制氢

We investigated high catalytic activity of Ni/HZSM-5 catalysts synthesized by the impregna-tion method, which was successfully applied for low-temperature steam reforming of bio-oil. The influences of the catalyst composition, reforming temperature and the molar ratio of steam to carbon fed on the stream reforming process of bio-oil over the Ni/HZSM-5 catalysts were investigated in the reforming reactor. The promoting effects of current passing through the catalyst on the bio-oil reforming were also studied using the electrochemical catalytic re-forming approach. By comparing Ni/HZSM-5 with commonly used Ni/Al₂O₃ catalysts, the Ni₂₀/ZSM catalyst with Ni-loading content of about 20% on the HZSM-5 support showed the highest catalytic activity. Even at 450 oC, the hydrogen yield of about 90% with a near complete conversion of bio-oil was obtained using the Ni₂₀/ZSM catalyst. It was found that the performance of the bio-oil reforming was remarkably enhanced by the HZSM-5 supporter and the current through the catalyst. The features of the Ni/HZSM-5 catalysts were also investigated via X-ray diffraction, inductively coupled plasma and atomic emission spectroscopy, hydrogen temperature-programmed reduction, and Brunauer-Emmett-Teller methods.     

CATALYTIC HYDROGEN TRANSFER OVER MAGNESIA, XVII. a HYDROCARBONS AS HYDROGEN DONORS

Donor activity of cyclohexene and a series of n-alkanes in catalytic hydrogen transfer to various organic groups over magnesia as a catalyst has been determined. Styrene, phenylacetylene, benzaldehyde and acetophenone were not reduced by cyclohexene in the temperature range 523-673 K. Cyclohexene oxide was reduced to cyclohexanol (38%) and nitrobenzene to aniline (56%) by cyclohexene under adopted conditions (673 K). The highest yield of aniline (57%) from nitrobenzene was reached at 673 K in the presence of n-decane from a series of C6 - C16 n-alkanes used as hydrogen     

不同硅铝比两亲性HZSM-5沸石的制备和表征

 采用三甲基氯硅烷并通过控制水的添加量对硅铝比分别为25, 42和101的HZSM-5沸石进行外表面修饰,制得三种两亲性沸石样品. 水的添加量对沸石催化剂的两亲性有显著影响. 红外光谱和低温氮吸附等测试结果表明,两亲性沸石样品具有与各自母体沸石相似的酸性及略小的比表面积. 在环己烯水合及乙酸异戊酯水解的相界面反应中,两亲性沸石分布于水-油两相界面,并表现出明显高于各自母体沸石的催化活性. 硅铝比为42的两亲性HZSM-5样品表现出最佳的相界面催化性能. 相对于环己烯水合反应,两亲性HZSM-5沸石更适用于乙酸异戊酯水解的相界面催化反应.     

Metal oxide-modified ZnO/SiO <Subscript>2</Subscript> catalysts for cyclo-dehydrogenation of ethylenediamine with propyleneglycol to 2-methylpyrazine

Metal oxide-modified ZnO /SiO2 catalysts were studied for the cyclo-dehydrogenation of ethylenediamine with propyleneglycol to 2-methylpyrazine at 633 K. The ZnO/SiO₂ catalyst showed fairly good ethylenediamine conversion and quantitative propyleneglycol conversion with about 60 mol% of 2-methylpyrazine selectivity, which is due to the existence of large amount of unconverted intermediate, 2-methylpiperazine. Metal oxide (CuO, NiO, Co₃O₄)-modified ZnO/SiO₂ catalysts were prepared to facilitate the dehydrogenation of 2-methylpiperazine to 2-methylpyrazine. About 82 mol% of 2-methylpyrazine selectivity was achieved on CuO and Co₃O₄ modified ZnO/SiO₂ catalysts, with significant increases of pyrazine selectivity. The catalytic properties of the metal oxidemodified ZnO/SiO₂ catalysts, pretreated with hydrogen gas as in the cyclo-dehydrogenation, were compared using the well-known probe reaction, the dehydrogenation/ dehydration of cyclohexanol to cyclohexanone or phenol/cyclohexene. The selectivities of pyrazine in the cyclo-dehydrogenation on the metal oxide-modified ZnO/SiO₂ catalysts were correlated with the phenol selectivities of the probe reaction. It is proposed that the metallic site of catalyst is responsible for the formation of pyrazine from ethylenediamine dimerization. The improved 2-methylpyrazine yield on CuO/ZnO/SiO₂ catalyst was explained by the proper adjustment of catalytic properties, which could be differentiated by the phenol selectivity in the cyclohexanol probe reaction. Thus, the large enhancement of 2-methylpiperazine dehydrogenation to 2-methylpyrazine and the suppression of excess pyrazine formation are supposed to occur on the metallic Cu formed in situ during the reaction during the cyclo-dehydrogenation of ethylenediamine with propyleneglycol.     

Catalytic pyrolysis of HDPE in continuous mode over zeolite catalysts in a conical spouted bed reactor

A study has been carried out using HZSM-5, HY and Hβ zeolite-based catalysts in the pyrolysis of high density polyethylene (HDPE) continuously fed into a conical spouted bed reactor (CSBR) at 500 °C and atmospheric pressure, with the aim being to assess the yields and composition of the main products (both light olefins and automotive fuel hydrocarbons). Product streams have been grouped into seven lumps: light olefins (C₂–C₄) and light alkanes (<C₄) in the gas fraction, the liquid fraction consisting of three lumps (non-aromatic C₅–C₁₁ compounds, single-ring aromatics and C₁₁₊ hydrocarbons), wax and coke. The results are compared with those already obtained in thermal pyrolysis in a CSBR and with those obtained in the literature using catalysts in bubbling fluidized beds. HZSM-5 zeolite-based catalyst is very selective to light olefins, ≈58 wt% once equilibrated; whereas high yields of non-aromatic C₅–C₁₁ products (around 45 wt%) are obtained with Hβ and HY zeolite-based catalysts. Wax yield increases as reactions proceed, especially with HY and Hβ zeolite-based catalysts, due to catalyst deactivation by coke formation. Product distribution with the different catalysts and their evolution throughout continuous operation by feeding HDPE is explained according to the different properties of the zeolites used.     

Chemical fixation of CO2 with highly efficient ZnCl2/[BMIm]Br catalyst system

The chemical fixation of CO₂ with mono-substituted terminal epoxides or cyclohexene oxide to form cyclic carbonates under the ZnCl₂/[BMIm]Br catalyst system without using additional organic solvents was achieved in excellent selectivity (>98%) and TOF (5410 h⁻¹) and the catalyst could be used six times almost without losing its catalytic activity and selectivity. Besides, the pure cis-cyclic carbonate of cyclohexene oxide was obtained in this catalyst system.     

Deactivation and regeneration of the B2O3/TiO2-ZrO2 catalyst in the vapor phase Beckmann rearrangement of cyclohexanone oxime

The deactivation and regeneration of B₂O₃/TiO₂-ZrO₂ catalyst for the vapor phase Beckmann rearrangement of cyclohexanone oxime to -caprolactam were studied. The fresh, deactivated and regenerated catalysts were characterized by using adsorption of nitrogen, X-ray diffraction (XRD), thermogravimetry (TG) and NH₃-temperature-programmed desorption (NH₃-TPD) techniques. The crystal structure and pore size distribution of the catalyst were retained after reaction, but the number of acid sites decreased significantly. There was a relationship between the amount of coke deposited on the catalyst and the decline in catalytic activity. These results suggest that the coke deposition on the surface of catalyst is mainly responsible for the catalyst deactivation. The catalytic activity can be recovered completely after calcining the deactivated catalyst in air flow at 600 °C for 8 h.     

康熙《皇城宫殿衙署图》解读(下)*

以尿素为沉淀剂,采用负压沉积沉淀法将Au负载于不同载体,分别制备了Au/HZSM-5、 Au/SiO_2及Au/Al_2O_3催化剂.采用X射线粉末衍射、透射电镜、 NH_3-程序升温脱附、红外羟基和原位吸附吡啶红外羟基等技术对催化剂进行了表征,探究了Au对不同载体的作用,并用脉冲微反装置评价了催化剂对正丁烷脱氢反应的性能.结果表明,相较于其他载金催化剂, Au/HZSM-5酸性较强, Au与HZSM-5相互作用后会形成Si-O(H)-Au基团,该活性相对正丁烷脱氢起到一定的促进作用.     

Highly shape-selective Zn-P/HZSM-5 zeolite catalyst for methanol conversion to light aromatics

A highly shape-selective and relatively long-lifetime HZSM-5-based catalyst (Zn-2P/HZSM-5) was prepared by chemical modification with both ZnSiF₆·6H₂O and H₃PO₄ solution. The phosphoric acid modification could effectively modulate the Brønsted acid strength of the HZSM-5 catalyst, which promotes the oligomerization, alkylation, cyclization, and hydrogen transfer reactions. The introduction of Zn-Lewis acid sites significantly improved the dehydroaromatization of higher olefins. All of these were very beneficial for the generation of BTX (i.e. benzene, toluene, and xylene) hydrocarbons in aromatization of methanol. The coke amount and the average rate of coke formation decreased over the Zn-2P/HZSM-5 catalysts, which may largely be ascribed to its lower strong acid sites and lower outer surface acidity. The catalytic performance of methanol aromatization showed that the Zn-2P/HZSM-5 catalyst exhibited the highest BTX selectivity of about 46.76% and the longest catalytic lifetime of about 498 h at T = 400 °C, P = 0.1 MPa, and weight hourly space velocity = 0.7 h⁻¹.     

双核烷基咪唑过氧磷钨酸盐相转移催化剂合成及催化烯烃环氧化性能

合成并表征了一类双核长链烷基咪唑阳离子修饰的过氧磷钨杂多酸盐催化剂[Dnmin]1.5PW4O24,考察了催化剂在过氧化氢为氧源的烯烃环氧化反应中的催化活性.研究表明,这类催化剂在反应过程中表现出相转移催化现象,并具有较高的催化活性和选择性.其中,双核十二烷基咪唑杂多酸盐催化剂[D12min]1.5PW4O24的活性最佳,其环己烯转化率和环氧环己烷选择性分别达到97.7%和96.3%.催化剂在经过简单离心分离后可重复使用,重复使用4次后环己烯转化率和环氧环己烷选择性仍可分别达到72.4%和97.2%.催化剂[D12min]1.5PW4O24在其它几种烯烃的环氧化反应中均表现出相转移催化特性,且具有较高的催化活性.     

A novel sublimable organic salt: Synthesis,characterization, thermal behavior,and catalytic activity for the synthesis of arylidene,heteroarylidene, and alkylidene malonates

A novel sublimable organic salt was synthesized, and its chemical structure was characterized by FTIR, 1D NMR, 2D NMR, and elemental analysis. In addition, the thermal phase transitions and thermal stability of new organic salt were investigated. The DSC and TGA results showed that the organic salt could convert into constituent molecules at?<?145 °C before decomposition temperature (T_dec.?~?200 °C) under atmospheric pressure without forming the liquid phase. Then, it was recondensed to regenerate the initial organic salt in the cool part of the vial. Therefore, it can be a promising organic salt towards the regeneration of spent catalyst from synthesis processes when the reaction mixture contains poorly volatile components and includes its use in gas-phase procedures. Also, the catalytic efficiency of new organic salt was investigated in the Knoevenagel condensation reaction. A variety of substituted arylidene and alkylidene malonates were isolated in 78–95% yield within six hours.? Under the optimized reaction conditions, the current catalytic procedure exhibited superiority compared to the mixed piperazine/acetic acid, piperidine/acetic acid, and piperidinium acetate. There were no significant changes in the new organic salt chemical structure and catalytic activity even after the 5th run. This work revealed the importance of the existence of simultaneous hydrogen bond acceptor/donor groups in our environmentally friendly catalyst to promote the Knoevenagel condensation reaction without the use of metal-containing catalysts.

     

Hydrogen Production by Catalytic Reforming of Liquid Hydrocarbons

In this review, we are reporting the catalytic reforming of liquid hydrocarbon fuels carried out in our research group, covering the catalytic reforming of iso-octane and toluene as surrogate of gasoline, gasoline fuel processor system and steam reforming of n-hexadecane and decahydronaphthalene, main constituents of diesel. The commercial ICI reforming catalyst is prone to be poisoned by sulfur contained in iso-octane. We investigated various supported transition metal formulations and developed Ni/Fe/MgO/Al₂O₃ (KIST-5) catalyst with prolonged catalytic stability (>760 h), higher activity and sulfur tolerance ability over commercial ICI and HT catalysts for ATR reaction of iso-octane. We found that the concentration of CO can be reduced to <1,800 ppm by the gasoline fuel processor system charged with KIST-5 reforming catalyst, commercial HTS catalyst and KIST Pt–Ni/CeO₂ LTS catalyst. The addition of Rh metal to spc-Ni/MgAl catalyst as promoter was found to be very effective in inhibiting the deactivation of spc-Ni/MgAl catalyst by sintering of reduced Ni metal at high temperature during steam reforming of n-hexadecane. A 0.3 wt% Rh loading on spc-Ni/MgAl catalyst was optimized to have the best performance for steam reforming of n-hexadecane among the prepared catalysts. The addition of Rh to spc-Ni/MgAl catalyst also restricted the deactivation of the catalyst due to carbon formation at high reaction temperature. In view point of prolonged stability and higher activity, these developed reforming catalysts have a good scope in the reforming process of gasoline and diesel for hydrogen station and fuel processor system applications.