Homogeneous Acid Research Articles

Interfacial Hydrolysis of Acetals on Protonated TEMPO-oxidized Cellulose Nanofibers

2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCNs), which have a high-density of exposed carboxylic acid groups on their crystalline surfaces, effectively act as acid catalysts in acetal hydrolysis. Carboxy-free cellulose nanofibers, polymeric carboxylic acids, and homogeneous acetic acid do not show significant catalytic activity under the same reaction conditions. Mercerized TOCNs differing from the original TOCNs in a crystalline structure were also ineffective, which suggests that the unique nanoarchitectural features of TOCNs, such as regularly aligned carboxylic acid groups, large specific surface areas, and structural rigidity, must be major factors in the acceleration of acetal hydrolysis. Kinetic analysis suggested that substrates and/or acid catalyst species were concentrated on the TOCN crystalline surfaces, which significantly enhanced the catalytic activity.

Catalytic and non-catalytic hydrothermal processing of Scenedesmus obliquus biomass for bio-crude production – A sustainable energy perspective

In the present study, hydrothermal liquefaction (HTL) of wet Scenedesmus obliquus biomass into bio-crude was carried out. Initially, the biochemical composition of S. obliquus biomass was examined, and it indicated high protein (56.1%) followed by carbohydrate (22.3%) and lipid (11.5%) contents. The ultimate analysis unveiled the presence of high carbon (48.1%) and oxygen (36.1%) in the biomass. This study had shed light on the selection of ideal reaction conditions such as temperature (200, 250, 300 °C), pressure (100, 200, 300 bar), and residence time (30, 60 min) for producing maximum bio-crude with/without catalyst aid. In the absence of the catalyst, a bio-crude yield of 35.7% was obtained at 300 °C temperature, 200 bar pressure, and 60 min residence time. On an interesting note, bio-crude yield was increased from 35.7 to 45.1% by adding homogeneous acid catalyst CH3COOH at 300 °C reaction temperature, which was higher than the other acid catalysts HCOOH (40%), H2SO4 (38%), HCl (39%), H3BO3 (37%), and the base catalysts NaOH (38%), KOH (37%), Na2CO3 (40%), K2CO3 (36%), Ca(OH)2 (37%). Elemental analyses of bio-crudes indicated a higher heating value of 35–40 MJ/kg, carbon-74%, nitrogen-5.86%, hydrogen-10.9%, sulfur <0.5 and oxygen content of 8.85%, which is comparable with petro-crude. Using CH3COOH as a catalyst in HTL led to reducing the oxygen content and simultaneously increased the higher heating value of bio-crude. In addition, GC-MS characterization of bio-crude indicated the presence of mono-aromatics, nitrogen heterocycles, phenols, indole and fatty acids. Thus, based on the yield and characteristics, the bio-crude produced from S. obliquus biomass could be used in petroleum refinery for fuel production.

Cellulose Depolymerization over Heterogeneous Catalysts.

Cellulosic biomass is the largest source of renewable organic carbon on our planet. Cellulose accounts for 40-50 wt % of this lignocellulose, and it is a feedstock for industrially important chemicals and fuels. The first step in cellulose conversion involves its depolymerization to glucose or to its hydrogenated product sorbitol. The hydrolysis of cellulose to glucose by homogeneous mineral acids was the subject of research for almost a century. However, homogeneous acids have significant drawbacks and are neither economical nor environmentally friendly. In 2006, our group reported for the first time the ability of heterogeneous catalysts to depolymerize cellulose through hydrolytic hydrogenation to produce sorbitol. Later, we reported the hydrolysis of cellulose to glucose using carbon catalyst containing weakly acidic functional groups. Understanding the reaction between cellulose and heterogeneous catalyst is a challenge as the reaction occurs between a solid substrate and a solid catalyst. In this Account, we describe our efforts for the conversion of cellulose to sorbitol and glucose using heterogeneous catalysts. Sorbitol is produced by sequential hydrolysis and hydrogenation of cellulose in one pot. We reported sorbitol synthesis from cellulose in the presence of supported metal catalysts and H2 gas. The reducing environment of the reaction prevents byproduct formation, and harsh reaction conditions can be used to achieve sorbitol yield of up to 90%. Glucose is produced by acid catalyzed hydrolysis of cellulose, a more challenging reaction owing to the tendency of glucose to rapidly decompose in hot water. Sulfonated carbons were first reported as active catalysts for cellulose hydrolysis, but they were hydrothermally unstable under the reaction conditions. We found that carbon catalysts bearing weakly acidic functional groups such as hydroxyl and carboxylic acids are also active. Weakly acidic functional groups are hydrothermally stable, and a soluble sugar yield of 90% was achieved in a 20 min reaction. We clarified that the polycyclic aromatic surface of the carbon adsorbs cellulose molecules on its surface by CH-π and hydrophobic interactions driven by a positive change in entropy of the system. The adsorbed molecules are rapidly hydrolyzed by active sites containing vicinal functional groups that recognize the hydroxyl groups on cellulose to achieve a high frequency factor. This phenomenon is analogous to the hydrolysis of cellulose by enzymes that use CH-π and hydrophobic interactions along with weakly acidic carboxylic acid and carboxylate pair to catalyze the reaction. However, in comparison with enzymes, carbon catalyst is functional over a wide range of pH and temperatures. We also developed a continuous flow slurry process to demonstrate the feasibility for commercial application of carbon-catalyzed cellulose hydrolysis to glucose using inexpensive catalyst prepared by air oxidation. We believe that further efforts in this field should be directed toward eliminating roadblocks for the commercialization of cellulose conversion reactions.

Preparation of para-Aminophenol from Nitrobenzene through Bamberger Rearrangement Using a Mixture of Heterogeneous and Homogeneous Acid Catalysts

The direct preparation of para-aminophenol (PAP) from nitrobenzene (NB) through Bamberger rearrangement was studied in a biphasic medium using a mixture of NbOx/SiO2 and H2SO4 as an acid catalyst. After optimization of the reaction parameters, PAP was obtained with 85–88% selectivity that represents a 10% selectivity improvement compared to sulfuric acid alone. The optimized conditions were implemented in a scale-up reaction, and PAP was isolated in 84% yield (based on the recovered starting material) with 97% HPLC purity. Overall, this process requires less sulfuric acid than the traditional process, leading to a drastic reduction of the saline waste.

Mutual Valorization of 5-Hydroxymethylfurfural and Glycerol into Valuable Diol Monomers with Solid Acid Catalysts

Biomass platform molecules such as glycerol and 5-hydroxymethylfurfural have been valorized into diol monomers by acetalization reaction in the presence of tridirectional large pore zeolites (HY and Beta), a laminar zeolite (ITQ-2) and a mesoporous aluminosilicate (MCM-41), and a conventional homogeneous acid catalyst (p-toluenesulfonic acid). The influence of the solvent polarity, pore structure, hydrophobic character, and acidity of the catalyst on the activity and selectivity to 5-hydroxymethylfurfural (HMF) glyceryl acetals has been studied. Results showed that, while the homogeneous catalyst mainly promotes polymerization reactions, tridirectional zeolites are more active catalysts but less selective and deactivate more rapidly than mesoporous MCM-41 and delaminated two-dimensional zeolites. ITQ-2 and MCM-41 catalysts with smaller confinement effects, easy diffusion, and adequate surface polarity provide high yield (98%) and selectivity (100%) to the target compound. These catalysts are stable and al...

Aqueous Phase Synthesis of 5-Hydroxymethylfurfural from Glucose over Large Pore Mesoporous Zirconium Phosphates: Effect of Calcination Temperature.

For a solid acid-catalyzed dehydration of biomass-derived carbohydrates into useful furan derivatives, a suitable porous solid acid catalyst having an optimum acidic density and its strength is required to avoid cascade reactions in biomass conversion processes. A large-pore mesoporous zirconium phosphate (m-ZrP) was prepared hydrothermally using P123 as a template in water solvent, which resulted in a higher pore diameter (>9 nm) having wormhole-like pore structures with balanced Lewis (L) to Brönsted (B) acid sites. The effects of calcination temperature (500–800 °C) on the textural, acidic/basic, and structural properties of the m-ZrP with its catalytic performance for glucose dehydration to 5-hydroxymethylfurfural (HMF) were investigated in a pure water media as a green and sustainable alternative solvent. The larger number of L and B acid sites and basic sites with their appropriate strengths were clearly related with a better catalytic performance in terms of glucose conversion and HMF yield. The strong L acid and basic sites in the m-ZrP efficiently promoted the glucose isomerization to fructose, which dehydrated exclusively on the weak B acid sites resulting in a maximum conversion of glucose (83.8%) and HMF yield (46.6%). The adjusted acidic and basic sites with large mesopore sizes make the m-ZrP yield a higher reaction rate (2.78 mmol gcat–1 h–1) and turnover frequency (11.68/h) for conversion of glucose to HMF, which showed higher catalytic activity than those of a small-pore m-ZrP and other mesoporous heterogeneous and homogeneous acid catalysts.

In situ epoxidation of waste soybean cooking oil for synthesis of biolubricant basestock: A process parameter optimization and comparison with RSM, ANN, and GA

AbstractIn this work, the use of artificial neural networks (ANNs) as an alternative tool for modelling and predicting the optimum conversion of the unsaturated fatty acid to epoxide in comparison with the response surface methodology (RSM) was developed. In the present investigation, waste soybean cooking oil (WCO) as biolubricant basestock was prepared via structural modification of unsaturated fatty acids (in situ epoxidation). Optimization of the effect of process parameters on maximum oxirane oxygen content (OOC) was studied using RSM. Interaction among the process parameters, such as C=C bonds to H2O2 molar ratio, catalyst loading, and reaction time was examined by ANOVA. The main focus of this study was to establish optimum OOC conditions using sulphuric acid (H2SO4) as a homogeneous acid catalyst. Optimum OOC of epoxidized waste soybean cooking oil (EWCO) was found to be 4.69 mass% under the experimental conditions of 60 °C temperature, 6 h reaction time, 1.5 g of catalyst loading, and 1:2 molar ratio of C=C bonds to H2O2. The resultant epoxide product was confirmed with the help of Fourier transform infrared spectroscopy (FTIR) (at 844.82 cm−1) and nuclear magnetic resonance spectroscopy (NMR) (at δ 2.8 to δ 3.1 ppm) analysis. Significant physicochemical properties of the prepared lubricant basestock were evaluated at optimum conditions using standard methods. Further, ANN modelling and genetic algorithm (GA) optimization were carried out by using an identical dataset. The results of the study revealed that the chemically modified WCO derivatives also can act as a potential biolubricant basestock.

Oxidation pattern of curdlan with TEMPO-mediated system

In this study, the TEMPO-mediated (TEMPO/NaBr/NaClO) oxidation pattern of curdlan was investigated through comprehensively structural analysis of the corresponding oxidized products. During the structural analysis, infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography tandem multiple angle laser scattering (GPC-MALS) and ultra-high performance liquid chromatography tandem quadrupole time of flight mass spectrometry (UHPLC-Q/TOF-MS) were applied. As a result, the homogenous β1-3 polyglucuronic acids (MW, 49.8, 29.8 and 7.0 kDa) were obtained with proper amount of oxidant (5.36 mmol NaClO) at various temperatures (4, 25, 50 °C), respectively. Compared to the oxidation of 1–4 linked glucan (starch and cellulose) with TEMPO-mediated system at same reaction conditions, higher degree of specific oxidation and less degradation were observed in that of 1–3 linked curdlan. The glycosylation at position 3 could stabilize the sugar ring, which inactivates the non-specific oxidation related hydroxyl groups on the sugar ring. Thus, the TEMPO-mediated system has higher selectivity to oxidize the primary hydroxyl groups of 1–3 linked curdlan and form polyglucuronic acid than those observed in the oxidation of starch and cellulose. In addition, same as those observed in previous work about starch, higher the temperature was used in the oxidation with TEMPO system, higher the activity of oxidant (NaClO solution) was, more non-specific oxidation occurred, and more the degradation were observed.

Development of catalyst complexes for upgrading biomass into ester-based biolubricants for automotive applications: a review.

Biomass-derived oils are recognised as the most promising renewable resources for the production of ester-based biolubricants due to their biodegradable, non-toxic and metal adhering properties. Homogeneous acid catalysts have been conventionally used in catalytic esterification and transesterification for the synthesis of ester-based biolubricants. Although homogeneous acid catalysts encounter difficulty during phase separation, they exhibit superior selectivity and good stereochemistry and regiochemistry control in the reaction. Consequently, transition metal complex catalysts (also known as homogeneous organometallic catalysts) are proposed for biolubricant synthesis in order to achieve a higher selectivity and conversion. Herein, the potential of both homogeneous transition metal complexes and heterogeneous supported metal complexes towards the synthesis of biolubricants, particularly, in esterification and transesterification, as well as the upgrading process, including hydrogenation and in situ hydrogenation–esterification, is critically reviewed.

THE ALTERATION OF COMPOSITION OF FATTY ACIDS AND INSULIN-BINDING ACTIVITY OF CELLS IN CONDITIONS OF OXIDATIVE STRESS UNDER EXPERIMENTAL DIABETES MELLITUS

The parallel study of effect of experimental diabetes mellitus on the level of lipids and composition of fatty acids in blood and homogenates of liver and insulin-binding activity of cells in conditions of oxidative stress demonstrated that in rats already at early period of development of diabetes, alongside with hyperlipoproteinemia, hypertriglyceridemia and hypercholesterolemia significant alterations are marked in structure of fatty acids and homogenates of liver. These alterations are accompanied by peroxide oxidation of lipids and decreasing of activity of enzymes-antioxidants and also by decreasing of insulin-binding activity of cells. Under experimental diabetes mellitus, a significant increasing of level of saturated fatty acids, especially palmitic fatty acid results in decreasing of levels of mono-unsaturated fatty acids (at the expense of oleic fatty acid) that significantly differs corresponding specter in patients with diabetes. The increasing of concentration of eicosapentaenoic and docosahexaenoic acids is accompanied by decreasing of total content of fatty acid Omega-3 at the expense of alfa-linoleic fatty acid. At that, the level of fatty acid Omega-6 reliably decreases both in erythrocytes and homogenates of liver. The results of study also testify that already at early stages of development of diabetes mellitus alterations in pool of fatty acids of erythrocytes and homogenates of liver are similar (with slight differences) and in all analyzed tissues disorder of metabolism of fatty acids has an anti-sclerotic direction.

Synthesis of cenosphere supported heterogeneous catalyst and its performance in esterification reaction

ABSTRACT A heterogeneous catalyst has been developed from cenosphere, a byproduct generated in thermal power plant. The performance of catalyst was investigated in the esterification of propionic acid and ethanol. The catalyst was characterized by FTIR, X-ray diffraction, field emission scanning electron microscope, and Brunauer–Emmett–Teller surface area and surface acidity analysis. The response surface methodology (RSM) with the Box–Behnken design was employed to design the experiments as well as to optimize the various process parameters such as catalyst loading, alcohol/acid molar ratio, and reaction temperature. The characterization revealed that the cenosphere supported catalyst possessed increased amounts of silica content, surface hydroxyl groups, surface area as well as surface acidity as compared with that of pristine cenosphere. The catalyst showed an excellent activity in the esterification reaction with a maximum conversion up to 91%. The RSM model well fitted the experimental data and predicted optimal conditions which were validated experimentally with a good agreement. The recyclability study showed a significant catalytic stability up to three reaction cycles. This study reveals that the cenosphere supported catalyst can be used as a potential catalyst in the esterification reaction may replace the conventional homogeneous acid catalyst.

Greening the esterification between isosorbide and acetic acid

This contribution deals with the investigation of greener conditions for the preparation of 2,5-diacetyl-isosorbide from the bio-based substances isosorbide and acetic acid. The influence of solvent, catalyst and reactant ratio on the course of the isosorbide conversion and selectivity to 2,5-diacetyl-isosorbide as well as to the intermediate 2-acetyl-isosorbide is examined. It was found that the conventionally used solvent toluene can be substituted by the greener solvent n-propyl acetate. Additionally, the homogeneous acid catalyst p-toluene sulfonic acid can be replaced by the heterogeneous catalyst Amberlyst-15, resulting in an easier isolation of the desired 2,5-diacetyl-isosorbide, this being an important precursor for the vasodilatory drug isosorbide-5-nitrate.

Scalable and simultaneous generation of homogeneous acid Co(III) and base Co(I) electrocatalysts using a divided electrolyzer

A scalable and simultaneous synthesis of Co(III) (Co2(SO4)3) and Co(I) ([Co(I)(CN)5]4−) electrocatalysts using a divided electrolyzer is reported for the first time. The overpotential gain of oxygen evolution reaction (OER) by high concentration of an acid and hydrogen evolution reaction (HER) by high concentration of a base was utilized for this new state-of-the art electro-syntheses. Difference in generation rate between acid electrocatalyst Co(III) and base electrocatalyst Co(I) was minimized by controlling the flow of H3O+ ions from anode to cathode. Also, variation in the nature of cathode materials was found to influence the formation rate of both acid Co(III) and base Co(I) electrocatalysts. We have shown that by selecting a suitable combination of electrode pair and controlling the presence of H3O+ ions it becomes possible to synthesize 3.5mM of Co(III) and 2.5mM of Co(I) simultaneously in both compartments of a divided electrolytic cell. This achievement on the hitherto unreported development in electrocatalyst synthesis strategy is the first of its kind in divided electrolytic cells.

Identification of Enzymatic Cleavage Products of β-Carotene-Rich Extracts of Kale and Biofortified Maize.

Provitamin A carotenoids in plant foods provide more than 80% of vitamin A intake for people in developing countries. Therefore, the conversion efficiency of β-carotene to vitamin A is important, as it determines the effectiveness of plant foods as sources of vitamin A in humans. The objective of this study was to determine the effect of plant food antioxidants such as α-tocopherol, γ-tocopherol, α-tocotrienol, γ-tocotrienol and total γ-oryzanol on the cleavage of β-carotene in vitro. Rat intestinal mucosa post mitochondrial fractions were incubated with β-carotene-rich extracts of kale and biofortified maize for an hour at 37°C. Rat intestinal mucosa post mitochondrial fractions were also incubated with β-carotene in the presence of either α-tocopherol, γ-tocopherol, α-tocotrienol, γ-tocotrienol or γ-oryzanol for 60 min at 37°C. The β-carotene cleavage products were extracted and analyzed by an HPLC equipped with a C18 column at 340nm and 450nm. When β-carotene alone was incubated without intestinal mucosa homogenate (control), no cleavage products were detected. When β-carotene alone was incubated with intestinal mucosa homogenate, β-apo-13-carotenone, β-apo-14-carotenal, retinal, retinol and retinoic acid were formed. However, incubation of β-carotene with either α-tocopherol, γ-tocopherol or α-tocotrienol resulted in a 10 fold inhibition of β-apo-14-carotenal and β-apo-13-carotenone formation. Antioxidant rich biofortified maize extract incubated with postmitochondrial fraction produced less β-apo-13-carotenone compared to the kale extract. These results suggest that antioxidants inhibit the cleavage of β-carotene and the formation of excentric cleavage products (β-apo-13-carotenone, β-apo-14-carotenal).

Green Synthesis of Double Long‐Chain Diglycerol Diacetal and Its Application as Lubricating Base Oil

AbstractDehydration acetalization of diglycerol with lauraldehyde in the presence of homogeneous acid catalysts using water as solvent has been studied. The prepared double long‐chain diglycerol diacetal was identified as a mixture of six regioisomers by GC and GC‐MS. p‐Dodecylbenzenesulfonic acid exhibited excellent activity for this acetalization reaction. The reaction parameters with p‐dodecylbenzenesulfonic acid catalyst were subsequently optimized in terms of the yield and isomer distribution of diglycerol diacetal. Under the optimum operating conditions, the yield of diglycerol diacetal reached 93.9%, and the selectivity in terms of the distribution of the six regioisomers was found to be in proportions of 24:36:18:11:3:8. Furthermore, the tribological performance of diglycerol diacetal has been evaluated as a potential lubricant base oil by means of an Optimol SRV‐V oscillating reciprocating friction and wear tester. The tribological test results revealed that diglycerol diacetal displayed superior lubrication properties compared to the commonly used poly‐alpha‐olefin (PAO 8).

Astragaloside IV Improves Bleomycin-Induced Pulmonary Fibrosis in Rats by Attenuating Extracellular Matrix Deposition.

Pulmonary fibrosis is a devastating lung disorder with mysterious pathogenesis and limited treatment options. It is well-recognized that the uncontrolled proliferation of lung fibroblasts and differentiation of fibroblasts into myofibroblasts excessively produce extracellular matrix (ECM) proteins which contribute to the fibrosis change of the lungs. Thus, blocking ECM accumulation would delay fibrosis progression. In this study, we observed the effects of astragaloside IV (ASV) (10 mg/kg/d) on ECM proteins in bleomycin (BLM, 5 mg/kg)-treated rats. Our results showed that ASV not only ameliorated BLM-induced body weight loss, lung coefficient increase, histological changes and collagen secretion, but also reduced the levels of type III collagen (Col-III) in lung homogenate, laminin (LN) and hyaluronic acid (HA) in serum, as well as hydroxyproline (HYP) in lung tissue. Besides, ASV significantly down-regulated the levels of high-mobility group box1 (HMGB1) in serum and lung tissue, and inhibited the up-regulated expression of α-SMA (marker of myofibroblasts) in the lungs. Taken together, these findings indicate that ASV attenuates BLM-induced ECM deposition, supporting its use as a promising candidate to treat lung fibrosis.

Synthesis of polyol esters by p-toluenesulfonic acid catalyst as synthetic lubricant oils

Esterification and transesterification reactions usually carry out in hydrocarbon solvents, such as toluene. Homogeneous acid catalysts such as, sulfuric acid, methane sulfonic acid, and p-toluene sulfonic acid are the most conventional catalysts for this purpose. Application of these catalysts causes some difficulties such as corrosion, and environment probleA most effective and less energy demanding method of producing fatty esters, polyol esters , by esterifying fatty acids, with a pentaerythritol and trimethylolpropan alcohols in the presence of an acid Catalyst at elevated temperature wherein an azeotroping agent , particularly toluene, is used to facilitate continuous removal of water by distillation, formed as a by-product during the esterification reaction.The esterification reaction is completed within 5 hours, pentaerythritol and trimethylolpropan esters was produced .ms

Selective esterification of glycerol with acetic acid or lauric acid over rod-like carbon-based sulfonic acid functionalized ionic liquids

A series of rod-like nitrogen-containing carbon-based sulfonic acid functionalized ionic liquids, [PrSO3HN][SO3CF3]/C, with tunable Brønsted acid site densities are fabricated by quaternary ammonization of hydrothermally prepared nitrogen-containing carbon nanorods with 1,3-propanesultone followed by anion exchange with trifluoromethanesulonic acid. The materials are successfully applied in the selective esterification of glycerol with acetic acid or lauric acid to the value-added glycerol esters including triacetain, glycerol monolaurate and glycerol dilaurate. The excellent esterification activity of the [PrSO3HN][SO3CF3]/C nanorods strongly depends on their Brønsted acid nature; additionally, the morphological characteristics, surface hydrophilicity and flexible polycyclic aromatic carbon structure influence the catalytic activity to some extent. The [PrSO3HN][SO3CF3]/C-2 nanorod with high density of super strong Brønsted acid sites and perfect rod-like nanostructure exhibits the highest esterification activity, and its activity outperforms Amberlyst-15, propylsulfonic acid functionalized SBA-15, the [PrSO3HN][SO3CF3] group functionalized carbonaceous framework obtained by high temperature (600°C) calcination as well as homogeneous p-toluenesulfonic acid. Moreover, the catalyst can be reused three times without significant activity loss, attributing to the chemical interactions between the [PrSO3HN][SO3CF3] groups and the carbon framework.

Selective Dehydration of Mannitol to Isomannide over Hβ Zeolite

Isomannide is a potential feedstock for the production of super engineering plastics. A prospective route to obtain isomannide is dehydration of mannitol derived from lignocellulosic biomass, but homogeneous acid catalysts reported in the literature produce a large amount of 2,5-sorbitan as a byproduct in the dehydration reaction. In this work, we initially studied the mechanism of proton-induced dehydration of mannitol by density functional theory calculations, which suggested that local steric hindrance around acid sites designed at the angstrom level can tune the selectivity toward isomannide formation. Based on this prediction, we found that the precisely defined microporous confinement offered by Hβ provides improved selectivity and high catalytic activity for the production of isomannide, where 1,4-dehydration is favored by 20 kJ mol–1 of activation energy. The optimization of the Si/Al ratio of Hβ to balance the acid amount and hydrophobicity improved the catalytic activity and achieved 63% yield o...

Upgrading of fast pyrolysis condensates via esterification with higher alcohols

The utilization of fast pyrolysis condensates is hindered by unwanted properties like corrosivity, high viscosity and tendency to polymerization. These characteristics result from the high content of organic acids and multiple functional groups and C-C double bonds. As an alternative to severe hydroprocessing, the addition of alcohol and subsequent esterification of acids and acetalization of aldehydes is investigated. Pyrolysis condensates are mixed with butanol and an acidic catalyst is added. This mixture is heated and kept under reflux in a dean-stark-apparatus to continuously boil off the water. As reference homogeneous liquid acids are used and compared to solid acid catalysts like ZnO or zeolites. The advantage of the heterogeneous, solid catalysts is the possibility to remove the solids after reaction and use them again for another batch in contrast to the homogeneous acids, which remain in the solution and need to be neutralized at the end. The most promising catalyst candidates are then used in experiments with varying process parameters. All products are analyzed for total acid number, water mass fraction, dynamic viscosity and higher heating value. The total acid number can be reduced by 90 % (from 110 to below 10 mg g−1), the water mass fraction by 90 % (from 25 % to below 2 %), the viscosity by 70 % (from 18 to 5 mm2 s−1) and the higher heating value can be increased by 45 % (from 16.6 to 31 MJ kg−1). These improvements should allow the utilization of upgraded pyrolysis liquids in standard boilers and as fuel in CHP plants.