Alkaline cupric oxide and nitrobenzene oxidation of alcell® lignin

A solvolysis lignin has been oxidatively degraded using nitrobenzene and cupric oxide (CuO) as catalysts. The effects of reaction conditions on lignin conversion to identifiable low molecular weight liquid products were quantified. Optimal yields of vanillin and syringaldehyde of 2.2 wt % and 5.9 wt % respectively were obtained using nitrobenzene at 180°C and 2h, whereas both were less than 1 wt % when CuO was used at 225°C and 1h, indicative of the milder oxidative power of CuO for this lignin. The higher total aldehyde yield from solvolysis lignin (8.2 wt %) than kraft lignin (5.1 wt %) when using nitrobenzene indicates it might be a better candidate for producing chemicals via oxidation.     

Comparative studies of oil compositions produced from sawdust,rice husk,lignin and cellulose by hydrothermal treatment

The objective of this study is to investigate the distribution of products, i.e. liquid, gas and solid from wood (sawdust) and non-wood biomass (rice husk), and major biomass components, i.e. lignin, cellulose produced by hydrothermal treatment (280 °C for 15 min) and analysis of liquid hydrocarbons (oils) for the differences in the hydrocarbon composition with respect to feed material. Cellulose showed the highest conversion among the four samples investigated in the present study. Sawdust and rice husk has almost similar conversions. Liquid products were recovered with various solvents (ether, acetone, and ethyl acetate) and analyzed by GC–MS. The oil (ether extract) from the hydrothermal treatment of cellulose consisted of furan derivatives whereas lignin-derived oil contained phenolic compounds. The compositions of oils (ether extract) from sawdust and rice husk contained both phenolic compounds and furans, however phenolic compounds were dominant. Rice husk derived oil consists of more benzenediols than sawdust derived oil. The volatility distribution of oxygenated hydrocarbons were carried out by C-NP gram and it showed that the majority of oxygenated hydrocarbons from sawdust, rice husk and lignin were distributed at n-C₁₁, whereas they were distributed at n-C₈ and n-C₁₀ in cellulose-derived oil. The gaseous products were carbon dioxide, carbon monoxide, methane in sawdust, rice husk, lignin and cellulose. In addition to this, ethylene, ethane and propane were observed for sawdust, rice husk and lignin. The major gas product was carbon dioxide for all samples.     

Ni-P/HZSM-5催化木质素降解制备酚类化学品

采用Ni-P复合改性HZSM-5催化剂催化木质素降解制备高附加值的单酚类化学品,探讨了催化剂种类、金属负载量、反应温度、反应时间以及溶剂种类对木质素催化降解制备酚类化合物的影响。同时采用X射线衍射仪（XRD）、比表面积和孔径分析仪（BET）、化学吸附仪（NH₃-TPD）、热重分析仪（TG）以及气相色谱质谱联用仪（GC/MS）对催化剂以及液相产物进行分析表征,同时探讨其催化失活以及再生机制。结果表明：Ni、P高度分散在HZSM-5催化剂的表面,Ni的添加有效地弱化了C－C键,致使β-O-4和α-O-4发生断裂,有效地提高了木质素加氢解聚的活性,减少了焦炭的生成,但催化剂的再生水热稳定性较差,重复使用性较低。当采用甲醇为供氢试剂,在反应温度为220℃,氢气压力为2MPa,反应时间为8h,催化剂负载量为10%,NaOH为共催化剂时,其木质素的转化率为98.6%,酚类化合物的含量达到74.97%。产物以苯酚、愈创木酚和紫丁香酚为主,低温促进了紫丁香酚的产生。     

Ni/Al2O3 catalysts and their activity in dehydrogenation of methylcyclohexane for hydrogen production

Previous results on different catalysts revealed that methylcyclohexane underwent selective dehydrogenation to form toluene and hydrogen. This reaction system is a useful prototype model for similar systems in the chemical process and petroleum refining industries, such as hydrotreating for aromatics reduction, desulfurization, denitrogenation, reforming for aromatics reduction, dehydrocyclization, and fuel processing of liquid hydrocarbons in the generation of hydrogen feed for fuel cells. Dehydrogenation of methylcyclohexane to toluene is a method for hydrogen storage in the form of liquid organic hydrides. The efficiency of the dehydrogenation reactions and the quantity of products depend on the catalyst used. In the case of the dehydrogenation of methylcyclohexane to toluene, a metallic function, usually platinum is required as the catalyst. Although, there were some different catalysts used by former researchers, there was almost no investigation about the use of the nickel catalysts for this reaction. From the economical point of view, more efficient catalysts and reaction engineering methods should be developed for these reactions.In this work dehydrogenation of methylcyclohexane was performed in a fixed-bed catalytic reactor in the temperature range of 653–713 K on prepared Ni/Al₂O₃ catalysts having 5, 10, 15 and 20 wt.% Ni content. The inlet flowrates of methylcyclohexane and hydrogen to the reactor were changed by keeping one of them constant in order to investigate their effects on this reaction.     

Coal Pyrolysis in a Laboratory‐Scale Two‐Stage Reactor: Catalytic Upgrading of Pyrolytic Vapors

In situ upgrading of coal pyrolysis vapors over Ce/Zr/Ni and Ce/Zr/Ni/Zn catalysts was studied in a two‐stage reactor. The catalytic effects of Ce/Zr/Ni and Ce/Zr/Ni/Zn on the pyrolysis products were examined, revealing that CO₂, CO, and H₂ were dramatically increased and pyrolytic water was decreased when using these catalysts. The tar collected in the cooling traps showed a slight increase after catalysis. Compared to the no‐catalyst condition, heterocyclic compounds and multicyclic aromatic hydrocarbons in the tar were significantly reduced, and benzene derivatives and aliphatics were increased. The molar ratio of H/C in tar was analyzed to further evaluate the tar quality. Possible reaction routes are proposed.     

Catalytic decomposition of benzyl phenyl ether to aromatics over cesium-exchanged heteropolyacid catalyst

Cesium-exchanged Cs _x H_3.0−x PW₁₂O₄₀ (X=2.0–3.0) heteropolyacid catalysts were prepared and applied to the decomposition of benzyl phenyl ether to aromatics. Benzyl phenyl ether was chosen as a lignin model compound for representing α-O-4 bond in lignin. Phenol, benzene, and toluene were mainly produced by the decomposition of benzyl phenyl ether. Conversion of benzyl phenyl ether and total yield for main products (phenol, benzene, and toluene) were closely related to the surface acidity of Cs _x H_3.0−x PW₁₂O₄₀ (X=2.0–3.0) heteropolyacid catalyst. Conversion of benzyl phenyl ether and total yield for main products increased with increasing surface acidity of the catalyst. Among the catalysts tested, Cs_2.5H_0.5PW₁₂O₄₀ with the largest surface acidity showed the highest conversion of benzyl phenyl ether and total yield for main products.     

Vapour Phase Hydrogenation of Cinnamaldehyde over Ni/γ-Al2O3 Catalysts: Interesting Reaction Network

The vapour phase hydrogenation of cinnamaldehyde over Ni loading γ-Al₂O₃ catalysts was performed at 1 atm and 300 °C in a fixed-bed reactor. The major product was hydrocinnamaldehyde. Unexpected products of styrene and ethylbenzene due to new reaction pathway of hydrodeformylation were observed. The results indicated that Ni metal was the active centers and the catalytic activity was parallel to the Ni surface area. The stability of TOF values implied that the cinnamaldehyde hydrogenation over Ni/γ-Al₂O₃ catalysts was a structure insensitive reaction.     

Pyrolysis of lignin in coal-tar pitch

The pyrolysis of hydrolytic lignin in coal-tar pitch over a temperature range of 320–380°C was studied in a batch reactor at atmospheric pressure. As a result of reactions with pitch, lignin underwent dissolution and destruction with the formation of compounds that remained in the reactor or were released from the reactor as liquid and gaseous products. The liquid products of the pyrolysis of lignin consist of organic and aqueous phases. The organic products of the pyrolysis of lignin in pitch predominantly contain guaiacol and its derivatives. The chemical interaction of coal-tar pitch with lignin leads to changes in the characteristics of pitch, an increase in the softening point, an increase in the concentrations of compounds insoluble in toluene and quinoline, and an increased yield of the coke residue.     

Thermal and catalytic upgrading of a biomass‐derived oil in a dual reaction system

The thermal and catalytic upgrsding of bio‐oil to liquid fuels was studied at atmospheric pressure in a dual reactor system over HZSM‐5, silica‐alumina and a mixed catalyst containing HZSM‐5 and silica‐alumina. This bio‐oil was produced by the rapid thermal processing of the maple wood. In this work, the intent was to improve the catalyst life. Therefore, the first reactor containing no catalyst facilitated thermal cracking of blo‐oil whereas the second reactor containing the desired catalyst upgraded the thermally cracked products. The effects of process variables such as reaction temperature (350°C to 410°C), space velocity (1.8 to 7.2 h^?1) and catalyst type on the amounts and quality of organic liquid product (OLP) were investigated, In the case of HZSM‐5 catalyst, the yield of OLP was maximum at 27.2 wt% whereas the selectivity for aromatic hydrocarbons was maximum at 83 wt%. The selectivities towards aromatics and aliphatic hydrocarbons were highest for mixed and silica‐alumina catalysts, respectively. In all catalyst cases, maximum OLP was produced at an optimum reaction temperature of 370°C in both reactors, and at higher space velocity. The gaseous product consisted of CO and CO₂, and C₁‐C₆ hydrocarbons, which amounted to about 20 to 30 wt% of bio‐oil. The catalysts were deactivated due to coking and were regenerated to achieve their original activity.     

Lignin to liquids over sulfided catalysts

Direct lignin conversion into valuable chemicals (phenols and hydrocarbons) was explored in a semi-continuous tubular reactor in the presence of a heterogeneous hydrotreating catalyst at 320-380 °C and hydrogen pressure 4-7 MPa. The catalyst to lignin mass ratio was varied in the range 0.25-1. The hydrolysis lignin was fully converted under the experimental conditions to yield gaseous, liquid and solid products. The amount of the undesired solid products decreased with the increasing severity of reaction conditions. The liquid products consisted mainly of aromatics and naphthenes in the organic phase and phenols in the aqueous phase. The proximity of the catalyst active sites and of the primary reaction intermediates originating from thermal depolymerization of lignin was shown to be crucial for product distribution.     

Catalytic conversion of concentrated miscanthus in water for ethylene glycol production

Miscanthus, a promising energy crop, was used for ethylene glycol (EG) production through one‐pot catalytic conversion. With a binary catalyst composed of commercial tungstic acid and Raney Ni, the miscanthus with 1 % concentration was transformed into EG with a yield of 35.5%. However, the yield dropped to 13.6% as the miscanthus concentration was increased to 10 %. The underlying reason for the yield decrease was disclosed through analysis of the liquid products, investigation of pretreatments, and characterization of the catalysts. It was found that the protectors on the surface of miscanthus and the lignin component underwent decomposition under reaction conditions, resulting in the formation of some organic acids and unsaturated compounds that preferentially poisoned the Raney Ni catalyst and consequently decreased the EG yield. When the inhibitors were effectively removed by base solvent pretreatment, the EG yield was successfully improved to 39.0% even under 10% concentration of feedstock. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2254–2262, 2014     

Selective catalytic Knoevenagel condensation by Ni–SiO2 supported heterogeneous catalysts: An environmentally benign approach

Selective catalytic Knoevenagel condensation is achieved with catalytic amounts of Ni impregnated on SiO₂ or TiO₂ supports. In this liquid phase reaction, quantitative yields were obtained under mild reaction conditions. Ni–SiO₂, Ni–TiO₂ catalysts showed efficiency of 100% conversion and 100% selectivity. With smaller quantities of 10% Ni–SiO₂ took less duration for the completion of reaction than TiO₂ catalysts in this environmentally benign process.     

Catalytic hydrothermal treatment of pine wood biomass: effect of RbOH and CsOH on product distribution

Low‐temperature hydrothermal treatment of pine wood biomass was performed in the presence of RbOH and CsOH catalysts (280 °C for 15 min). The effect of the catalysts on the distribution of products and the volatility distribution of oxygenated hydrocarbons was studied in detail. Oxygenated hydrocarbons were extracted from the liquid and solid portions and analysed individually by gas chromatography/mass spectrometry. Catalytic (RbOH and CsOH) hydrothermal treatment of wood biomass produced mainly phenolic compounds and benzenediol derivatives. The use of RbOH and CsOH catalysts hindered the formation of char and favoured the formation of oil products, as observed previously for various other base catalysts. The volatility distribution of hydrocarbons (ether extract) was characterised by carbon‐normal paraffin (C‐NP) gram and it was found that the oxygenated hydrocarbons from all runs, including thermal, were distributed in the boiling point region of n‐C₆ to n‐C₁₇. Copyright © 2005 Society of Chemical Industry     

The Formation of Monomeric Products from Lignin by the Action of Ammonium Sulfide

Acetoguaiacone and propioguaiacone were found to be the dominant lignin monomeric products (molar ratio 1.3 to 1) from the spent liquor of hemlock pulped with ammonium sulfide/methanol/water. The combined amounts of the ketones were as high as 3.5% based on wood. This is higher than reported monomer quantities from any other pulping process.

The model compounds, guaiacyl glycerol β-(2-methoxyphenyl) ether and coniferyl alcohol, also produced aceto- and propioguaiacone, upon ammonium sulfide treatment at 180°C. The molar conversion to these two ketones was more than 50% in both cases. It was, therefore, concluded that uncondensed β-0-4 lignol structures were the primary lignin precursors of the ketones, and coniferyl alcohol was an intermediate in this conversion.

Studies using coniferyl alcohol and wood meal were also conducted at 140°C. An alpha carbonyl intermediate was found which primarily formed propioguaiacone.     

Catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds over Pd/XCs2.5H0.5PW12O40/OMC (ordered mesoporous carbon) (X = 10–30 wt.%) catalysts

A series of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC (ordered mesoporous carbon) (X = 10, 15, 20, 25, and 30 wt.%) catalysts with different Cs_2.5H_0.5PW₁₂O₄₀ contents (X, wt%) were prepared by a sequential incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monomeric cyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. Acidity of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC catalysts served as an important factor determining the catalytic performance in the reaction. Conversion of 2,3-dihydrobenzofuran and total yield for main products (2-ethylphenol and ethylcyclohexane) increased with increasing acidity of Pd/XCs_2.5H_0.5PW₁₂O₄₀/OMC catalysts.     

Investigation of rapid conversion of switchgrass in subcritical water

The reaction characteristics of switchgrass conversion in subcritical water were investigated using a batch reactor under conditions of rapid rising to 250–350 °C and pressure of 20 MPa, with reaction times varying from 1–300 s. The effects of temperature and reaction time on product distribution and yields of chemical products were investigated. High conversion of switchgrass (90 wt.% on dry biomass basis) can be obtained in less than 60 s under a relative lower reaction temperature of 350 °C, compared with that in a switchgrass flash pyrolysis process where switchgrass conversion achieves only 58.9–78.8 wt.% in temperature range of 450–550 °C. The yield of water solubles (WS) can reach 37 wt.% after reaction for 1 s at 250 °C. The increases in temperature and reaction time lead to increases of the biomass conversion and the yield of gas, while WS yield decreases by secondary decomposition reactions. Many lignin-derived compounds were identified by GC-MS analysis and could well be recovered in methanol solubles (MS). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis of methanol insolubles (MI) indicated that the lignocellulosic matrix could be significantly decomposed, and no char formation was observed, while many lignin structures were left in the MI products. These results provide important information for recovering value-added chemicals from energy crops and biomass waste.     

Anionic surfactants: lauric products

Lauryl sulfate and lauryl ether sulfate obtained by the sulfation of lauryl alcohol and lauryl alcohol ethoxylate are representative of anionic surfactants and are used as a formable detergent or an emulsifier. For the sulfation of lauryl alcohol and lauryl alcohol ethoxylate, SO₃ gas, it was found that the quality of products was significantly influenced by the reaction conditions. In order to obtain good quality products we developed a new technology by using a new type of reactor called a “climbing film reactor,” in which SO₃ gas and liquid raw material flow ascendingly.     

Studying the thermal conversion of acetone lignin in supercritical butanol in the presence of NiCuMo/SiO<Subscript>2</Subscript> catalysts

Existing and emerging technologies for the chemical processing of wood are mainly aimed at transforming its cellulose component into target products. In these processes, lignin is produced on a large scale as a waste product, but there are no advanced ways of processing it. This work investigates the effect NiCuМо/SiO₂ catalysts have on the thermal transformation of acetone lignin in supercritical butanol at temperatures of 280, 300, and 350°C. The resulting liquid products are studied via gas–liquid chromatography mass spectrometry, and 13С NMR spectroscopy. It is found that butanol undergoes almost no thermochemical conversions at temperatures below 300°C. Catalysts raise its level of conversion to 36–40 wt %. Under the effect of NiCuМо/SiO₂ catalysts, the yield of hexane-soluble products of acetone lignin thermal conversion at 300°C increases by a factor of 2.4, while the yield of solid residue falls by approximately a factor of 3.3. Catalysts reduce the relative content of methoxyphenols in hexane-soluble products: the content of syringol in particular falls by a factor of 14. According to ¹³С NMR spectroscopy, the catalytic transformation of acetone lignin to liquid acetone-soluble products is accompanied by the breaking of β–О–4 chemical bonds between the structural fragments of lignin and a reduction in the content of methoxyl groups, primarily in the syringyl structural units of the resulting products.     

Oxidation of Methyl tert-Butyl Ether (MTBE) and Ethyl tert-Butyl Ether (ETBE) by Ozone and Combined Ozone/Hydrogen Peroxide

The aim of this work was to study the reaction of ozone and combined ozone/hydrogen peroxide on oxygenated additives such as methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) in dilute aqueous solution using controlled experimental conditions. Experiments conducted in a semi-continuous reactor with MTBE and ETBE in combination (initial concentration: 2 mmol/L of each) showed that ETBE was better eliminated than MTBE with both ozone and combined O₃/H₂O₂. Batch experiments led to the determination of the ratio of the kinetic constants for the reaction of OH°-radical with MTBE and ETBE [k_OH°/ETBE/k_OH°/MTBE = 1.7). Tert-butyl formate and tert-butyl acetate were identified as the ozonation byproducts of MTBE and ETBE, respectively, while tert-butyl alcohol was found to be produced during the ozonation of both compounds.     

Partial oxidation of butane to syngas using nano-structure Ni/zeolite catalysts

In this study, performance of nano-structure Ni over different zeolite supports in partial oxidation of butane was investigated. First, partial oxidation process was performed without catalyst to evaluation of optimal conditions. For in situ reduction of catalysts, H₂ produced from homogenous reaction was used. Catalytic partial oxidation was carried out using nano-structure nickel catalysts supported by ZSM5, mordenite and Y. Each catalyst was synthesized through reverse microemulsion method. The catalysts were characterized by BET surface area, XRD, SEM and TGA. Highest butane conversion (≈89%) observed in the presence of Ni/Y catalyst. Also Ni/Y shows the highest overall selectivity to CO and H₂ as the most desired partial oxidation products. Results from TGA showed that the minimum quantity of formatted coke was related to Ni/Y, which confirmed the stability of butane conversion versus time for this catalyst.