Pepsin immobilized on inorganic supports for the continuous coagulation of skim milk.

The milk-clotting enzyme pepsin was immobilized onto beads of alumina, titania, glass, stainless steel, iron oxide, and Teflon for treating skim milk in a fluidized-bed reactor. Two covalent attachment procedures using silanized supports and glutaraldehyde and two adsorption procedures were evaluated. The three best catalysts were titania and glass, using the covalent attachment procedure, and alumina, using the adsorption procedure at pH 1.2. The pepsin adsorbed on alumina catalyst has commercial potential compared to the previously used glass catalyst. Attempts to increase the stability of pepsin adsorbed on alumina by cross-linking with glutaraldehyde were unsuccessful owing to the low pH necessary for optimum pepsin adsorption; Desorption of pepsin from alumina during reactor operation was determined. Regeneration of spent catalysts was only partially successful.     

Catalytic upgrading of oil fractions separated from food waste leachate

In this work, catalytic cracking of biomass waste oil fractions separated from food waste leachate was performed using microporous catalysts, such as HY, HZSM-5 and mesoporous Al-MCM-48. The experiments were carried out using pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) to allow the direct analysis of the pyrolytic products. Most acidic components, especially oleic acid, contained in the food waste oil fractions were converted to valuable products, such as oxygenates, hydrocarbons and aromatics. High yields of hydrocarbons within the gasoline-range were obtained when microporous catalysts were used; whereas, the use of Al-MCM-48, which exhibits relatively weak acidity, resulted in high yields of oxygenated and diesel-range hydrocarbons. The HZSM-5 catalyst produced a higher amount of valuable mono aromatics due to its strong acidity and shape selectivity. Especially, the addition of gallium (Ga) to HZSM-5 significantly increased the aromatics content.     

Pyrolysis of triglyceride materials for the production of renewable fuels and chemicals

Conversion of vegetable oils and animal fats composed predominantly of triglycerides using pyrolysis type reactions represents a promising option for the production of renewable fuels and chemicals. The purpose of this article was to collect and review literature on the thermo-chemical conversion of triglyceride based materials. The literature was divided and discussed as (1) direct thermal cracking and (2) combination of thermal and catalytic cracking. Typically, four main catalyst types are used including transition metal catalysts, molecular sieve type catalysts, activated alumina, and sodium carbonate. Reaction products are heavily dependant on the catalyst type and reaction conditions and can range from diesel like fractions to gasoline like fractions. Research in this area is not as advanced as bio-oil and bio-diesel research and there is opportunity for further study in the areas of reaction optimization, detailed characterization of products and properties, and scale-up.     

ZSM-5(38)/Al-MCM-41复合分子筛对纤维素催化热解的影响

以纤维素为原料,以自制的不同硅铝比ZSM-5(38)/Al-MCM-41微-介孔复合分子筛为催化剂,在固定床反应器上进行了催化热解实验。采用XRD表征分子筛,采用GC-MS分析生物油成分,考查了催化剂的改变对生物质热解产物及生物油成分的影响。实验结果表明：添加催化剂后,生物油产率降低,且其含水率也有所增加。与未添加催化剂相比,生物油中D L-2,3-丁二醇有明显提高。其中,ZSM-5(38)/Al-MCM-41(20) 最有利于苯酚、愈创木酚 (2-甲氧基-苯酚) 的生成。此外,这几种催化剂均有利于小分子化合物的生成,其中,ZSM-5(38) 有利于C4~C5化合物的生成,微-介孔复合分子筛则有利于C6~C8化合物的生成。     

Catalytic oxidation of alkenes by manganese(III) porphyrin-encapsulated Al, V, Si-mesoporous molecular sieves

Cationic manganese-porphyrin, [meso-tetrakis(4-trimethylammoniophenyl)porphyrinato]manganese(III) pentachloride (MnTAPP), has been prepared and encapsulated into mesoporous molecular sieves Al-MCM-41 and V-MCM-41, containing different amounts of Al and V, respectively. The catalytic activities of these heterogeneous materials were tested in the liquid phase oxidation of cyclohexene and styrene in acetonitrile with iodosylbenzene (PhIO) as oxygen source. Both types of catalysts were active in the oxidation reaction. MnTAPP encapsulated in Al-MCM-41 produces allylic oxidation products alone and no epoxide with styrene was found. However, it produces both epoxide and allylic oxidation products with cyclohexene. At the same time, MnTAPP encapsulated in V-MCM-41 produces epoxide as major product and little allylic oxidation product with styrene, while both epoxide and allylic oxidation products were obtained with cyclohexene. It is suggested that the regioselective effect is due to relatively more acidic Al-MCM-41 than V-MCM-41 which could make the CC bond unreactive towards epoxidation and produces allylic oxidation product. With increasing Al or V content in the support, the porphyrin loading was found to increase, which in turn increases the catalytic activity of the heterogeneous systems. The heterogeneous catalysts were reused for three times. The selectivity of these heterogeneous catalysts does not change appreciably even after three times of reusing, but their catalytic activity decreases marginally. This may be attributed to catalyst leaching and/or decomposition of MnTAPP complex under the reaction conditions.     

Efficient production of biodiesel from high free fatty acid-containing waste oils using various carbohydrate-derived solid acid catalysts

In the present study, such carbohydrate-derived catalysts have been prepared from various carbohydrates such as d-glucose, sucrose, cellulose and starch. The catalytic and textural properties of the prepared catalysts have been investigated in detail and it was found that the starch-derived catalyst had the best catalytic performance. The carbohydrate-derived catalysts exhibited substantially higher catalytic activities for both esterification and transesterification compared to the two typical solid acid catalysts (sulphated zirconia and Niobic acid), and gave markedly enhanced yield of methyl esters in converting waste cooking oils containing 27.8wt% high free fatty acids (FFAs) to biodiesel. In addition, under the optimized reaction conditions, the starch-derived catalyst retained a remarkably high proportion (about 93%) of its original catalytic activity even after 50 cycles of successive re-use and thus displayed very excellent operational stability. Our results clearly indicate that the carbohydrate-derived catalysts, especially the starch-derived catalyst, are highly effective, recyclable, eco-friendly and promising solid acid catalysts that are highly suited to the production of biodiesel from waste oils containing high FFAs.     

Efficient conversion of d-glucose into d-sorbitol over MCM-41 supported Ru catalyst prepared by a formaldehyde reduction process

Ru/MCM-41 catalyst prepared by an impregnation–formaldehyde reduction method showed higher catalytic activity and sorbitol selectivity than other catalysts in the hydrogenation of glucose. SEM and XRD indicated the partial surface properties of Ru/MCM-41. Moreover, Ru dispersion and Ru surface area of Ru/MCM-41 were determined by pulse chemisorption, and the result further proved that Ru/MCM-41 had higher catalytic activity. A catalyst recycling experiment demonstrated that Ru/MCM-41 was a better catalyst and it could be reused three or four times. A speculated mechanism was proposed to illustrate the detailed process of d-glucose hydrogenation to produce sorbitol.     

Efficient conversion of d-glucose into d-sorbitol over MCM-41 supported Ru catalyst prepared by a formaldehyde reduction process

Ru/MCM-41 catalyst prepared by an impregnation-formaldehyde reduction method showed higher catalytic activity and sorbitol selectivity than other catalysts in the hydrogenation of glucose. SEM and XRD indicated the partial surface properties of Ru/MCM-41. Moreover, Ru dispersion and Ru surface area of Ru/MCM-41 were determined by pulse chemisorption, and the result further proved that Ru/MCM-41 had higher catalytic activity. A catalyst recycling experiment demonstrated that Ru/MCM-41 was a better catalyst and it could be reused three or four times. A speculated mechanism was proposed to illustrate the detailed process of d-glucose hydrogenation to produce sorbitol.     

Activated alumina as an energy source for peptide bond formation: Consequences for mineral-mediated prebiotic processes

Summary. The catalytic properties of various forms of alumina were tested for alanine dimerization reaction. The catalytic efficiency of alumina depends on the structure, as well as on acid/base properties of the catalyst. The highest yields of Ala₂ were achieved on activated alumina with surface of neutral pH (about 3% conversion after 2 weeks). Thermal analysis of Ala + alumina reaction systems shows that the thermal behavior of amino acid changes substantially in contact with the activated surface of the alumina catalyst. The reaction of Ala is detected as being strongly endothermic by differential thermal analysis of pure amino acid (above 250°C). The alanine endothermic reaction is shifted substantially to lower values (below 200°C) and hardly detectable if activated alumina is present. The reaction mechanism of amino acid activation on alumina surface and its significance for mineral-catalyzed prebiotic peptide bond formation are discussed. Received June 6, 2000 Accepted July 27, 2000     

Solvent screening methodology for in situ ABE extractive fermentation

Solvent screening for in situ liquid extraction of products from acetone-butanol-ethanol (ABE) fermentation was carried out, taking into account biological parameters (biocompatibility, bioavailability, and product yield) and extraction performance (partition coefficient and selectivity) determined in real fermentation broth. On the basis of different solvent characteristics obtained from literature, 16 compounds from different chemical families were selected and experimentally evaluated for their extraction capabilities in a real ABE fermentation broth system. From these compounds, nine potential solvents were also tested for their biocompatibility towards Clostridium acetobutylicum. Moreover, bioavailability and differences in substrate consumption and total n-butanol production with respect to solvent-free fermentations were quantified for each biocompatible solvent. Product yield was enhanced in the presence of organic solvents having higher affinity for butanol and butyric acid. Applying this methodology, it was found that the Guerbet alcohol 2-butyl-1-octanol presented the best extracting characteristics (the highest partition coefficient (6.76) and the third highest selectivity (644)), the highest butanol yield (27.4 %), and maintained biocompatibility with C. acetobutylicum.     

2-β-Benzothiazolyl-6-iminopyridylmetal dichlorides and the catalytic behavior towards ethylene oligomerization and polymerization

A series of 2-(2-benzothiazolyl)-6-(1-(arylimino)ethyl)pyridines and their metal (Fe or Co) complexes were prepared. All organic compounds were fully characterized by NMR, FT-IR spectra and elemental analysis, and all metal complexes were identified by FT-IR spectroscopic and elemental analysis. The molecular structures of representative metal complexes were confirmed by single-crystal X-ray diffraction and displayed the distorted trigonal bipyramid geometry. Upon activation with modified methylaluminoxane (MMAO), the iron pro-catalysts showed good catalytic activities up to the range of 10⁷ g mol⁻¹(Fe) h⁻¹ in ethylene reactivity with the high selectivity for the vinyl-type products of both oligomers and polyethylene waxes; whereas the cobalt pro-catalysts showed moderate activities towards ethylene oligomerization. The correlations between metal complexes and their catalytic activities and products were investigated in detail under various reaction parameters and discussed.     

Catalytic Pyrolysis of Raw and Thermally Treated Cellulose Using Different Acidic Zeolites

Fast pyrolysis of biomass using zeolite catalyst has shown to be effective in improving aromatic production. This study focuses on aromatic production through catalytic pyrolysis of major biomass constituent i.e., cellulose. Furthermore, cellulose was torrefied to understand torrefaction’s effect on pyrolysis products. The influence of SiO₂/Al₂O₃ ratios of zeolite (ZSM-5) catalyst on aromatic production during pyrolysis of raw and torrefied cellulose was investigated. Results showed that the catalyst acidity played a pivotal role in eliminating anhydro sugars and other oxygenated compounds while producing more aromatics. The maximum aromatic yield (~25 wt%) was obtained when ZSM-5 with the highest acidity (SiO₂/Al₂O₃?=?30) was used, while the lowest yield (7.99 wt%) was obtained when the least acidic catalyst was used (SiO₂/Al₂O₃?=?280) for raw cellulose pyrolysis. Torrefaction process showed to have positive effect on the aromatic production from pyrolysis. There were no aromatics produced from pyrolysis of raw cellulose in the absence of catalyst, whereas significant amount of aromatic compounds were produced from both catalytic and noncatalytic pyrolyses of torrefied cellulose. The aromatic hydrocarbons produced from catalytic pyrolysis of torrefied cellulose were 5 % more than those produced from raw cellulose at the highest temperature and catalyst acidity (SiO₂/Al₂O₃?=?30).     

Application of powdered ceramics support to the production of l-tryptophan by resting Escherichia coli K-12 cells

Escherichia coli K-12 cells having tryptophanase activity could be readily adsorbed to the surface of commercial ceramic powders such as γ-alumina, silica, titania, zirconia or glass, when they were suspended in a neutral or alkaline buffer solution in the presence of poly(methacryl-oxyethyl trimethyl ammonium chloride) (PMAAC), a cationic flocculant. Tryptophanase activity of the cells treated with PMAAC was somewhat less than that of the untreated cells, however, the activity of the cells adsorbed to titania, zirconia or glass powder after five recyclings was appreciably more stable than that of the intact cells.     

Influence of Alumina Binder Content on Catalytic Performance of Ni/HZSM-5 for Hydrodeoxygenation of Cyclohexanone

The influence of the amount of alumina binders on the catalytic performance of Ni/HZSM-5 for hydrodeoxygenation of cyclohexanone was investigated in a fixed-bed reactor. N₂ sorption, X-ray diffraction, H₂-chemisorption and temperature-programmed desorption of ammonia were used to characterize the catalysts. It can be observed that the Ni/HZSM-5 catalyst bound with 30 wt.% alumina binder exhibited the best catalytic performance. The high catalytic performance may be due to relatively good Ni metal dispersion, moderate mesoporosity, and proper acidity of the catalyst.     

Comparison of Catalytic Characteristics of Biomass Derivates with Different Structures Over ZSM-5

The conversion of three major biomass derivates was conducted in a quartz tubular fixed bed reactor over a ZSM-5 catalyst. As the model compounds of polyols, saturated furans and unsaturated furans, ethylene glycol (EG), tetrahydrofuran (THF) and furan were pyrolyzed to find out the influence of chemical structure on the catalytic characteristics. The effect of pyrolysis temperature (400?～?650 °C), weight hourly space velocity (2.9?～?15.5 h^?1) and partial pressure (2.12?～?20.49 Torr) on the feed conversion, product yield and selectivity were investigated. The hydrogen to carbon effective ratio (H/C_eff) was referred to, to analyze the capacity of biomass derivates being converted to chemicals (olefins and aromatics). The results showed that the existence of rings and C=C had great effect on the catalytic characteristics. The conversion of furan was much lower (mainly less than 60 %) than that of EG and TH,F which were close to 100 %. It was also found that the chemical yield of THF was slightly more than that of EG, which can be attributed to its relative higher H/C_eff of 1.5. Furan produced the highest coke yield, which was more than 15 %, whereas that of EG and THF was only around 5 %. The serious coking of furan led to the lowest chemical yield, which was less than 35 %. This study paves a way for the mechanism study on catalytic characteristics of biomass-derived feedstocks over zeolite catalysts.     

Esterification of Levulinic Acid Using ZrO<Subscript>2</Subscript>-Supported Phosphotungstic Acid Catalyst for Ethyl Levulinate Production

Ethyl levulinate (EL) is a versatile bio-based chemical with various applications such as fragrance and flavoring agents and also fuel blending component. EL can be produced through catalytic esterification of levulinic acid (LA) with ethanol. Herein, a series of zirconia (ZrO₂)-supported phosphotungstic acid (HPW) (HPW/Zr) catalyst, 15-HPW/Zr, 20-HPW/Zr, and 25-HPW/Zr, were prepared, characterized, and tested for EL production. The physicochemical properties of catalysts were characterized using Fourier-transformed infrared (FTIR) spectroscopy, x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), N₂ physisorption, and ammonia temperature-programmed desorption (NH₃-TPD). The effect of reaction parameters: reaction time, temperature, catalyst loading, and molar ratio of LA to ethanol was inspected on LA conversion and EL yield. The catalyst with high surface area and high acidity seemed suitable for EL production. Among the catalysts tested, 20-HPW/Zr exhibited the highest EL yield of 97.3% at the following conditions: 150 °C, 3 h, 1.0 g of 20-HPW/Zr and 1:17 M ratio of LA to ethanol. The 20-HPW/Zr could be reused for at least four times with insignificant decrease in the EL yield. This study demonstrates the potential of ZrO₂-supported HPW for bio-based alkyl levulinate production at mild process conditions.     

Selective hydrogenolysis of raw glycerol to 1,2-propanediol over Cu–ZnO catalysts in fixed-bed reactor

The catalytic properties of Cu–ZnO catalysts for glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) were tested in a fixed-bed reactor at 250 °C and 2.0 MPa H₂. The relation between composition, surface properties, and catalytic performance of glycerol hydrogenation of Cu–ZnO catalysts was studied using nitrogen adsorption (BET methods), XRD, H₂ temperature-programmed reduction, and N₂O chemisorptions. It was found that there was a close link between the surface CuO amount of Cu–ZnO catalyst and the reactivity for glycerol hydrogenation. The Cu–ZnO catalyst (Cu/Zn = 1.86) which had the highest surface Cu amount showed the best catalytic activity for glycerol hydrogenolysis. Furthermore, Cu–ZnO catalyst presented good stability and remarkable catalytic activity for glycerol hydrogenolysis to 1,2-PDO using raw glycerol derived from the fat saponification as feedstock.     

Investigation of hydrocarbon fractions form waste plastic recycling by FTIR, GC, EDXRFS and SEC techniques

Waste high-density polyethylene was converted into different hydrocarbon fractions by thermal and thermo-catalytic batch cracking. For the catalytic degradation of waste plastics three different catalysts (equilibrium FCC, HZSM-5 and clinoptilolite) were used. Catalysts differ basically in their costs and activity due to the differences of micro- and macroporous surface areas and furthermore the Si/Al ratio and acidities are also different. Mild pyrolysis was used at 430 °C and the reaction time was 45 min in each case. The composition of products was defined by gas chromatography, Fourier transform infrared spectroscopy, size exclusion chromatography, energy-dispersive X-ray fluorescence spectroscopy and other standardized methods. The effects of catalysts on the properties of degradation products were investigated. Both FCC and clinoptilolite catalysts had considerably catalytic activity to produce light hydrocarbon liquids, while HZSM-5 catalyst produced the highest amount of gaseous products. In case of liquids, carbon numbers were distributed within the C₅–C₂₃ range depending on the cracking parameters. Decomposition of the carbon chain could be followed by GC and both by FTIR and SEC techniques in case of volatile fractions and residues. Catalysts increased yields of valuable volatile fractions and moreover catalysts caused both carbon chain isomerization and switching of the position of double bonds.     

Three-component Castagnoli-Cushman reaction with ammonium acetate delivers 2-unsubstituted isoquinol-1-ones as potent inhibitors of poly(ADP-ribose) polymerase (PARP)

An earlier described three-component variant of the Castagnoli-Cushman reaction employing homophthalic anhydrides, carbonyl compound and ammonium acetate was applied towards the preparation of 1-oxo-3,4-dihydroisoquinoline-4-carboxamides with variable substituent in position 3. These compounds displayed inhibitory activity towards poly(ADP-ribose) polymerase (PARP), a clinically validated cancer target. The most potent compound (PARP1/2 IC₅₀ = 22/4.0 nM) displayed the highest selectivity towards PARP2 in the series (selectivity index = 5.5), more advantageous ADME prameters compared to the clinically used PARP inhibitor Olaparib.