{"id":1848,"date":"2017-04-05T17:37:57","date_gmt":"2017-04-05T20:37:57","guid":{"rendered":"https:\/\/www.nachodelatorre.com.ar\/mosconi\/?p=1848"},"modified":"2017-04-05T17:37:57","modified_gmt":"2017-04-05T20:37:57","slug":"produciendo-combustibles-renovables-a-partir-de-madera","status":"publish","type":"post","link":"https:\/\/www.fie.undef.edu.ar\/ceptm\/?p=1848","title":{"rendered":"Produciendo combustibles renovables a partir de madera"},"content":{"rendered":"

El hidrodeoxigenaci\u00f3n (HDO) de aceites obtenidos por pir\u00f3lisis es una tecnolog\u00eda para producir combustible di\u00e9sel, gasolina, combustibles de aviaci\u00f3n (JP) a partir de madera. En este trabajo, se han analizado los productos y se describen las reacciones qu\u00edmicas que se producen durante el proceso de HDO de biomasa lignocelul\u00f3sica.<\/p>\n

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The hydrodeoxygenation (HDO) of bio-oil derived from white oak wood using non-sulfided catalysts was studied in a two zone continuous flow trickle bed reactor system. The major organic components of the pyrolysis oil were pyrolytic lignin (large phenolic polymers), xylose, levoglucosan, organic acids (primarily acetic acid), and hydroxyacetaldehyde. The first zone was a low temperature zone (130\u2009\u00b0C) that contained a Ru\/C catalyst. In this zone, carbonyl groups were hydrogenated, producing propylene glycol (from hydroxyacetone), ethylene glycol (from hydroxyacetaldehyde), and sorbitol (from levoglucosan). A more severe hydrotreatment was performed in a second zone containing a bifunctional Pt\/ZrP catalyst at a temperature between 300 and 400\u2009\u00b0C. In the two-stage HDO, an organic phase was produced that consisted of a distribution of hydrocarbons that were primarily cyclic alkanes (naphthenes) ranging from C7<\/sub> to C24<\/sub>. The organic phase carbon yield decreased with increasing reaction temperature in the second zone. Catalyst deactivation and reactor plugging by coking occurred under all reaction conditions after 55\u201372\u2005h time on stream (TOS). After \u224855\u2005h TOS, more than 25\u2009% of the carbon in the original bio-oil was accumulated as coke, with increasing amounts for higher temperatures in the second zone. Hydrotreatment gave rise to >C5<\/sub> hydrocarbon (gasoline and distillate-range fuel) overall yields between \u224830 and 47\u2005carbon\u2009% for all experiments compared to the 79.5\u2009% theoretical yield calculated for the bio-oil feedstock. Coke formation and undesired cracking to C1<\/sub>\u2013C4<\/sub> hydrocarbon gases were the main causes of lower fuel carbon yields.<\/p>\n<\/div>\n<\/section>\n

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Introduction<\/h2>\n

As non-renewable petroleum resources have been deemed a major cause of global climate change, attention has shifted towards renewable and sustainable sources of liquid transportation fuels. Lignocellulosic biomass has received significant attention as a feedstock to make renewable transportation fuels because it is both cheap and abundant. Several approaches are currently being studied to produce renewable transportation fuels from lignocellulosic biomass, including fast pyrolysis, gasification, and biochemical approaches.[1-4<\/a>] The pyrolysis route for biomass conversion has several technical and economic advantages over gasification and biological approaches, including:<\/p>\n

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  1. Lower total capital investment and operating costs for liquid fuel production.[4<\/a>]<\/li>\n
  2. The ability to easily process mixed feedstocks including agricultural wastes, grasses, and woody biomass.[1, 2, 5<\/a>]<\/li>\n
  3. Shorter residence time and simpler feedstock pretreatment (drying and grinding) compared to biological approaches.[2, 6<\/a>]<\/li>\n<\/ol>\n

    Several studies discussing the production,[7, 8<\/a>] properties,[9<\/a>] applications,[10<\/a>] and HDO[11-15<\/a>] of pyrolysis oil and the techno-economic analysis of the pyrolysis process[3, 4, 16<\/a>] have been performed. Much of this prior work centers on the improvement of bio-oil (pyrolysis oil) properties in relation to traditional petroleum feedstocks. Bio-oils typically contain \u224850\u2005wt\u2009% carbon, \u22487\u2005wt\u2009% hydrogen, and \u224843\u2005wt\u2009% oxygen.[17<\/a>] The high oxygen and water contents results in bio-oil having a lower energy density (15\u201319\u2005MJ\u2009kg\u22121<\/sup>) compared to petroleum oil (40\u2005MJ\u2009kg\u22121<\/sup>). Additionally, the bio-oil is unstable, phase separates with time, and is not miscible with petroleum-derived fuels. Due to these limitations, pyrolysis oil cannot be directly used as a liquid transportation fuel in conventional engines and must be upgraded into fungible fuels.<\/p>\n

    Several approaches have been utilized to upgrade bio-oil into liquid fuels. Vispute and Huber separated the bio-oil into two fractions: a water-soluble and a water-insoluble fraction mainly consisting of pyrolytic lignin.[18<\/a>] The aqueous fraction made up 50\u2009% of the total C present in bio-oil, with the remaining carbon in the lignin phase. The low-temperature hydrogenation of the aqueous fraction of bio-oil using Ru\/C as catalyst yielded polyols (propylene glycol, ethylene glycol) and sorbitol.[18<\/a>] The hydrotreatment of lignin in the presence of precious-metal catalysts produces naphthenes.[19, 20<\/a>] Bio-oils can also be converted into renewable aromatics or olefins by combining hydrotreating with a zeolite catalyst.[21<\/a>]<\/p>\n

    The entire bio-oil has also been converted into liquid fuels by hydrotreatment or hydrocracking.[12, 14, 22, 23<\/a>] The hydrotreatment of bio-oil has been carried out in a fixed-bed reactor at high temperature (310\u2013375\u2009\u00b0C) using Pd\/C as catalyst to produce ketones, acids, esters, phenols, and alkylated phenols. These products were subsequently hydrocracked in the presence of a conventional hydrotreating catalyst at 400\u2009\u00b0C and 2000\u2005psi (1\u2005psi=6.89\u2005kPa).[23<\/a>] Elliott et\u2005al. observed that the rate of deactivation of the hydrotreatment catalyst depended on feed flowrate and reaction temperature.[12<\/a>] Catalyst deactivation during the hydrotreatment reaction is a serious issue as it leads to deactivation of the active catalyst phase.[21<\/a>] The phenolic compounds, or pyrolytic lignin, adsorb strongly on acidic sites on alumina forming phenate species that were proposed to be precursors for coking.[13<\/a>] Ab\u2005initio studies revealed that phenolic groups preferentially form keto groups in the aqueous phase.[24<\/a>] Formation of network polymers derived from these keto groups is thought to be a main mechanism for coking.[25<\/a>] Pyrolytic lignin even forms coke on the catalyst surface at temperatures as low as 25\u2009\u00b0C.[20<\/a>]<\/p>\n

    Few studies are available in the literature that explore the fundamental chemistry occurring or in which a detailed analysis of the reaction products obtained in this process was performed. One of the objectives of this paper is to study the HDO of a well-characterized bio-oil and analyze the full range of products formed during the two-step catalytic HDO process. By fully characterizing the products after low and high temperature treatments, the fundamental reaction chemistry involved can be delineated. We also analyze the fuel-grade yields from the dual-stage HDO process studied in this work and compare it to other reported yields in academia and industry. This paper thus provides insight into how improved catalysts could be designed for conversion of bio-oil and which biofuel yields can be realistically achieved through the successful implementation of these catalysts<\/p>\n<\/section>\n

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    Results and Discussion<\/h2>\n
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    Characterization of pyrolysis oil<\/h3>\n

    The composition of pyrolysis oil as characterized by Karl\u2013Fisher, GC, HPLC, and elemental analysis is presented in Table\u20051<\/a>. An elemental analysis showed that bio-oil contained 43.5\u2009% C, 7.1\u2009% H, and 49.4\u2009% O. Karl\u2013Fisher analysis showed that the pyrolysis oil contained 21.5\u2005wt\u2009% water. Previous characterization of this pyrolysis oil revealed viscosities of 0.1771\u2005Pa\u2009s at 25\u2009\u00b0C and 0.0638\u2005Pa\u2009s at 40\u2009\u00b0C.[26<\/a>] Microfiltration with a 0.8\u2005\u03bcm membrane similar to that previously performed in literature resulted in approximately 3\u2005wt\u2009% of the bio-oil being removed as char particles.[26<\/a>] Out of the total carbon content, \u224830\u2009% was present as acids, aldehydes, ketones, and furan-based compounds whereas \u224820\u2009% of the bio-oil was detected in the form of levoglucosan, sorbitol, and xylose. Sugars and their derivatives comprised a large portion of the bio-oil: mainly C5<\/sub> sugars (11.65\u2005wt\u2009%) and levoglucosan (7.17\u2005wt\u2009%). Major components derived from hemicellulose include acetic acid (9.73\u2005wt\u2009%), hydroxyacetaldehyde (6.17\u2005wt\u2009%), dimethyl tetrahydrofuran (2.49\u2005wt\u2009%), and hydroxyacetone (1.68\u2005wt\u2009%). Solubility tests indicated that 51\u2009% of the carbon (C\u2009%) making up the bio-oil was pyrolytic lignin. Carbon derived from the pyrolytic lignin was undetectable in GC and HPLC due to their high boiling point, which is consistent with other studies.[20<\/a>] The summation of the carbon detected by HPLC, GC, and solubility tests was 102\u2005C\u2009%, indicating that our characterization methods were able to detect all the carbon present in the bio-oil with slight calibration errors.<\/p>\n

    Table\u00a01.\u00a0<\/span>Characterization of bio-oil using GC, HPLC, Karl\u2013Fisher, and elemental analysis (bold indicates major components).<\/header>\n
    \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    Component<\/th>\nMolecular formula<\/th>\nConcentration [mmol\u2009L\u22121<\/sup>]<\/th>\nTOC [%]<\/th>\n<\/tr>\n<\/thead>\n
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    1. [a]\u2005C5<\/sub> sugars are primarily xylose.<\/li>\n<\/ol>\n<\/td>\n<\/tr>\n<\/tfoot>\n
    methanol<\/td>\nCH3<\/sub>OH<\/td>\n120<\/td>\n0.34<\/td>\n<\/tr>\n
    hydroxyacetaldehyde<\/b><\/td>\nC2<\/sub>H4<\/sub>O2<\/sub><\/b><\/td>\n2160<\/b><\/td>\n6.17<\/b><\/td>\n<\/tr>\n
    acetic acid<\/b><\/td>\nC2<\/sub>H4<\/sub>O2<\/sub><\/b><\/td>\n3406<\/b><\/td>\n9.73<\/b><\/td>\n<\/tr>\n
    ethylene glycol<\/td>\nC2<\/sub>H6<\/sub>O2<\/sub><\/td>\n38<\/td>\n0.11<\/td>\n<\/tr>\n
    methyl acetate<\/td>\nC3<\/sub>H6<\/sub>O2<\/sub><\/td>\n50<\/td>\n0.14<\/td>\n<\/tr>\n
    hydroxyacetone<\/td>\nC3<\/sub>H6<\/sub>O2<\/sub><\/td>\n589<\/td>\n1.68<\/td>\n<\/tr>\n
    propanoic acid<\/td>\nC3<\/sub>H6<\/sub>O2<\/sub><\/td>\n177<\/td>\n0.51<\/td>\n<\/tr>\n
    propylene glycol<\/td>\nC3<\/sub>H8<\/sub>O2<\/sub><\/td>\n43<\/td>\n0.12<\/td>\n<\/tr>\n
    2\u2009(5\u2009H<\/em>)-furanone<\/td>\nC4<\/sub>H4<\/sub>O2<\/sub><\/td>\n182<\/td>\n0.52<\/td>\n<\/tr>\n
    \u03b3-butyrolactone<\/td>\nC4<\/sub>H6<\/sub>O2<\/sub><\/td>\n68<\/td>\n0.19<\/td>\n<\/tr>\n
    tetrahydrofuran<\/td>\nC4<\/sub>H8<\/sub>O<\/td>\n31<\/td>\n0.09<\/td>\n<\/tr>\n
    1-hydroxy-2-butanone<\/td>\nC4<\/sub>H8<\/sub>O2<\/sub><\/td>\n325<\/td>\n0.93<\/td>\n<\/tr>\n
    butanol<\/td>\nC4<\/sub>H10<\/sub>O<\/td>\n17<\/td>\n0.05<\/td>\n<\/tr>\n
    2,3-butanediol<\/td>\nC4<\/sub>H10<\/sub>O2<\/sub><\/td>\n90<\/td>\n0.26<\/td>\n<\/tr>\n
    furfural<\/td>\nC5<\/sub>H4<\/sub>O2<\/sub><\/td>\n188<\/td>\n0.54<\/td>\n<\/tr>\n
    R<\/em>-\u03b3-hydroxymethyl-\u03b3-butyrolactone<\/td>\nC5<\/sub>H8<\/sub>O3<\/sub><\/td>\n8<\/td>\n0.25<\/td>\n<\/tr>\n
    2-methyl tetrahydrofuran<\/td>\nC5<\/sub>H10<\/sub>O<\/td>\n600<\/td>\n1.71<\/td>\n<\/tr>\n
    cyclopentanol<\/td>\nC5<\/sub>H10<\/sub>O<\/td>\n23<\/td>\n0.06<\/td>\n<\/tr>\n
    C5<\/sub> sugars (HPLC)<\/b>[a]<\/sup><\/td>\nC5<\/sub>H<\/b>x<\/b><\/em><\/sub>O<\/b>y<\/b><\/em><\/sub><\/td>\n4079<\/b><\/td>\n11.65<\/b><\/td>\n<\/tr>\n
    phenol<\/td>\nC6<\/sub>H6<\/sub>O<\/td>\n4<\/td>\n0.01<\/td>\n<\/tr>\n
    catechol<\/td>\nC6<\/sub>H6<\/sub>O2<\/sub><\/td>\n376<\/td>\n1.07<\/td>\n<\/tr>\n
    5-hydroxymethylfurfural<\/td>\nC6<\/sub>H6<\/sub>O3<\/sub><\/td>\n198<\/td>\n0.57<\/td>\n<\/tr>\n
    3-methyl-1,2-cyclopentanedione<\/td>\nC6<\/sub>H8<\/sub>O2<\/sub><\/td>\n134<\/td>\n0.38<\/td>\n<\/tr>\n
    levoglucosan (HPLC)<\/b><\/td>\nC6<\/sub>H10<\/sub>O5<\/sub><\/b><\/td>\n2508<\/b><\/td>\n7.17<\/b><\/td>\n<\/tr>\n
    2,5-dimethyl tetrahydrofuran<\/td>\nC6<\/sub>H12<\/sub>O<\/td>\n872<\/td>\n2.49<\/td>\n<\/tr>\n
    cyclohexanol<\/td>\nC6<\/sub>H12<\/sub>O<\/td>\n282<\/td>\n0.80<\/td>\n<\/tr>\n
    1,2-cyclohexanediol<\/td>\nC6<\/sub>H12<\/sub>O2<\/sub><\/td>\n86<\/td>\n0.25<\/td>\n<\/tr>\n
    hexanoic acid<\/td>\nC6<\/sub>H12<\/sub>O2<\/sub><\/td>\n356<\/td>\n1.02<\/td>\n<\/tr>\n
    sorbitol (HPLC)<\/td>\nC6<\/sub>H14<\/sub>O6<\/sub><\/td>\n691<\/td>\n1.97<\/td>\n<\/tr>\n
    guaiacol<\/td>\nC7<\/sub>H8<\/sub>O2<\/sub><\/td>\n63<\/td>\n0.18<\/td>\n<\/tr>\n
    total C identified by GC and HPLC<\/td>\n<\/td>\n17\u2009843<\/td>\n51.0<\/td>\n<\/tr>\n
    pyrolytic lignin<\/b><\/td>\n<\/td>\n<\/td>\n51<\/b><\/td>\n<\/tr>\n
    total C present in bio-oil<\/td>\n<\/td>\n35\u2009000<\/td>\n102<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    The carbon distribution is presented in Figure\u20051<\/a>. Out of the total carbon content \u224850\u2009% of compounds are C2<\/sub>, C5<\/sub>, and C6<\/sub> carbons. C5<\/sub> carbons mostly include xylose, with appreciable amounts of 2-methyl tetrahydrofuran and furfural also present. C6<\/sub> carbons include mostly levoglucosan and smaller amounts of phenols and cyclohexanols. The C7<\/sub> carbons are mainly guaiacol. The remaining \u224850\u2009% of carbon in the bio-oil is detected as high molecular weight (MW) pyrolytic lignin with a carbon number greater than 7. Pyrolytic lignin consists of phenolic oligomers that can range anywhere from 50 to 3000\u2005Da but that have an average MW between 400 and 1300\u2005Da.[20, 27<\/a>]<\/p>\n

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    \"Figure\u00a01.<\/a><\/div>
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    \n

    Figure\u00a01.<\/h4>\n