Tuning the product distribution during the catalytic pyrolysis of waste tires: The effect of the nature of metals and the reaction temperature

Metal catalysts based on Ni, Co, and Pd supported on SiO2 were evaluated in the catalytic pyrolysis of waste tires using pyrolysis experiments coupled to gas chromatography/mass spectrometry (Py–GC/MS) and thermogravimetric analysis coupled with Fourier Transform Infrared spectrometer (TGA–FTIR) techniques. The effect of temperature and the nature of metals on the product distribution and reaction pathways was determined. Catalytic pyrolysis promoted aromatization and cracking reactions at particularly low temperatures ca. 350 °C, leading mainly to the formation of alkenes (isoprene), aromatic terpenes (p-cymene), aliphatic terpenes (d,l-limonene), and other aromatic compounds such as benzene, toluene, and xylenes (BTX). The Pd/SiO2 catalyst was the most selective toward aromatic compounds (around 40 %), owing to its well-known hydrogenation/dehydrogenation capacity, while CCsingle bond bond cleavage reactions, leading to alkenes, were more favored on the Ni/SiO2 and Co/SiO2 catalysts. In all cases, high selectivity to limonene and isoprene was observed at low temperature. Above 400 °C, no significant differences in product distribution were observed between catalyzed and uncatalyzed pyrolysis. Herein, selectivity toward high-value hydrocarbons (i.e., d,l-limonene, isoprene, BTX, and p-cymene) during the catalytic pyrolysis of waste tires was tuned by the nature of the supported transition metals (i.e., Ni, Co, Pd) and the reaction temperature (e.g., <400 °C). The results demonstrate that the use of these catalysts is a promising strategy to valorize waste tires into high added-value products.Fil: Osorio Vargas, Paula Alejandra. Universidad del Bio Bio; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Menares, Tamara. Universidad del Bio Bio; Chile. Universidad de Concepción; ChileFil: Lick, Ileana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Casella, Mónica Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Romero, Romina. Universidad de Concepción; Chile. Universidad de Tarapaca. Instituto de Alta Investigacion.; ChileFil: Jiménez, Romel. Universidad de Concepción; ChileFil: Arteaga Pérez, Luis E.. Universidad del Bio Bio; Chile. Universidad de Concepción; Chil

Diet of the neotropical otter Lontra longicaudis (Carnivora: Mustelidae) from the Santiago River basin, Mexico

The diet of the neotropical otter Lontra longicaudis is reported in the Santiago River, Nayarit - Jalisco, Mexico. A diet based on fish was found (percentage of occurrence 43.86%), with lower frequencies of insects (22.81%), reptiles (9.36%) and amphibians (8.77%), with the introduced fish Oreochromis aureus and Cyprinus carpio, the most consumed.Se reporta la dieta de la nutria neotropical Lontra longicaudis en el Río Santiago, Nayarit/Jalisco, México. Se encontró una dieta basada en peces (porcentaje de ocurrencia 43.86%), con frecuencias menores de insectos (22.81%), reptiles (9.36%) y anfibios (8.77%), siendo los peces introducidos Oreochromis aureus y Cyprinus carpio, las especies más consumidas

Development of a dispersive liquid-liquid microextraction coupled with magnetic dispersive microsolid phase extraction for determination of triazines in wastewater samples

Producción CientíficaThe combination of two microextraction techniques (dispersive liquid-liquid microextraction [DLLME] and magnetic dispersivemicrosolid phase extraction [MDMSPE]) was developed and reported for atrazine and simazine preconcentration from wastewatersamples. The proposal methodology involved the use of magnetite supports functionalized with different alkyl or phenyl groups. Themagnetic adsorbents were synthesized by the solvothermal methodassisted by microwave, characterized, and used in the samplepreconcentration of atrazine and simazine. The method validation included parameters such as the wastewater matrix effect, repeat-ability, and recovery. The analyte separation and quantification were performed by high-performance liquid chromatography withultraviolet detection (HPLC-DAD). Parameters, such as the polarity and mass of magnetic solids and pH, were evaluated to providebetter extraction performance. The highest recoveries (> 95%) were obtained with 50 mg of the phenyl group support (CS2) at pH 5,using 5 mL of the sample and carbon tetrachloride and methanol, as extraction and dispersive solvents, respectively. The lowest limitsof detection (LOD) achieved were 13.16 and 13.86 ng L−1, and the limits of quantification (LOQ) were 43.89 and 46.19 ng L−1forsimazine and atrazine, respectively, with repeatability (expressed as %RSD) below 5% in all cases. The developed method is simple,easy, and low cost for the analysis of two herbicides potentially dangerous for environmental and human health

Genomic variation in recently collected maize landraces from Mexico

AbstractThe present dataset comprises 36,931 SNPs genotyped in 46 maize landraces native to Mexico as well as the teosinte subspecies Zea maiz ssp. parviglumis and ssp. mexicana. These landraces were collected directly from farmers mostly between 2006 and 2010. We accompany these data with a short description of the variation within each landrace, as well as maps, principal component analyses and neighbor joining trees showing the distribution of the genetic diversity relative to landrace, geographical features and maize biogeography. High levels of genetic variation were detected for the maize landraces (HE=0.234 to 0.318 (mean 0.311), while slightly lower levels were detected in Zea m. mexicana and Zea m. parviglumis (HE=0.262 and 0.234, respectively). The distribution of genetic variation was better explained by environmental variables given by the interaction of altitude and latitude than by landrace identity. This dataset is a follow up product of the Global Native Maize Project, an initiative to update the data on Mexican maize landraces and their wild relatives, and to generate information that is necessary for implementing the Mexican Biosafety Law

Dataset from analytical pyrolysis assays for converting waste tires into valuable chemicals in the presence of noble-metal catalysts

About 25.7 million tons of waste tires (WT) are discarded each year worldwide causing important environmental, and health problems. This waste is difficult to manage and dispose due to its huge rate of generation and its extremely slow biodegradation. Therefore, many efforts are being made to valorise WTs into a series of marketable products under a circular economy framework. In the attempt to convert WT into higher-value products, thermochemical decomposition by pyrolysis has emerged as a promising process. The pyrolysis is a thermochemical transformation (under an oxygen-depleted atmosphere) of the tire´s polymeric constituents: natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) into three major fractions. These fractions are a gas (10–35%, TPG) which is usually used as a heat source (50 MJ kg⁻¹), a solid consisting mainly of recovered carbon black (12–45%, rCB), and a liquid fraction (35-65%, TPO) containing a complex mixture of organic compounds. Among the high-value compounds that can be found in the TPO are D,L-limonene, isoprene, benzene, toluene, mixed-xylene, ethylbenzene, styrene, p-cymene, and some polycyclic aromatic hydrocarbons. This mixture is commonly used as a diesel substitute and owing to its complex composition it rarely is seen as a source for more valuable products. To overcome such a complexity, and selectively produce specific chemical identities, different types of catalysts have been used. Herein, we provide a dataset from a systematic study about catalytic pyrolysis of WT for selectively producing benzene, toluene, and xylenes (BTX) and p-cymene on noble metals (Pd, Pt, Au) supported on titanate nanotubes (NT-Ti). The comprehensive analysis of this data was recently published, thus, the analytical techniques, experimental conditions and dataset are given in the present paper as a complement to that publication. The reaction was evaluated in an analytical pyrolysis unit consisting in a micropyrolizer coupled to a mass spectrometer (Py-GC/MS) operating at temperatures between 400 and 450 °C in a fast pyrolysis regime (12 s). The effectivity of catalysts was measured in terms of selectivity to monoaromatics as BTX and p-cymene, under non-catalytic and for catalytic pyrolysis conditions. Moreover, the reaction was conducted on individual rubbers (Polyisoprene, Polybutadiene, and Styrene-Butadiene) and DL-limonene, to get deep insights into the transformation behaviour and reaction pathways. Therefore, the reader will find a data-in-brief paper containing some characterizations of the WTs used for the investigation, along with a complete dataset of Py-GC/MS results. Finally, the original files for the interpretation of the MS results are also provided, so that the reader can easily use this information to further expand the study to their own interest (industrial or scientific).Puede accederse a los datos primarios de este trabajo haciendo clic en "Documentos relacionados".Centro de Investigación y Desarrollo en Ciencias Aplicada

Influence of feedstock demineralization on the chemical composition of pyrolysis vapours derived from sugarcane residues in py-GC/MS

Sugarcane bagasse (SCB) and trash (SCT) are prospective feedstock materials for fast pyrolysis systems. However, their relatively high inorganic content, especially alkali and alkaline earth metals (AAEMs), affects the quality of the produced bio-oil. In order to overcome this problem, various chemical pretreatment methods have been developed. This study aims to evaluate the effect of demineralization of SCB and SCT on the chemical composition of the bio-oil, viz. by applying micro-pyrolysis (py-GC/MS). Both biomass types were leached with demineralized water, HCl, H2SO4 and citric acid solutions at different temperatures and leaching times. The results indicate that leaching with either inorganic or organic acids, causes the yields of levoglucosan in the pyrolysis vapours to increase. This is explained by the mitigation of undesirable degradation reactions of cellulose and cellulose intermediates in the presence of catalytically active AAEMs, the latter being partially removed in the leaching process. The limited variations in yield of phenolic compounds upon different pretreatments demonstrated the stability of the lignin irrespective any leaching pretreatment. The composition of pyrolysis vapours derived from citric acid-treated biomass is hardly influenced by any changes in demineralization conditions

Carbon Aerogel-Supported Nickel and Iron for Gasification Gas Cleaning. Part I: Ammonia Adsorption

Biomass gasification is a promising way to obtain green energy, but the gas composition makes it unsuitable for use in traditional technologies (i.e., IC engine). Gas purification over nickel and/or iron catalysts is an attractive alternative. Cellulose-based carbon aerogels (CAGs) have shown suitable physical chemical properties for use as catalyst supports. In this work, nickel and iron catalysts are supported on CAG made from cellulose microfibers. Microfibers were impregnated with (NH4)(2)SO4 to increase the mass yield. Carbonization was evaluated at different heating rates, maximum temperatures, and dwell times to generate CAGs. Resulting chars were characterized by N-2 adsorption, X-ray diffraction (XRD), and Raman spectroscopy. The CAG with better properties (specific surface, pore size, thermal resistance) was impregnated with the metal precursor salt via incipient wetness and treated with H-2. Catalysts were characterized by transmission electron microscopy (TEM), XRD, N-2 adsorption, and inductively coupled plasma optical emission spectrometry (ICP-OES). Ammonia adsorption was studied over CAG and catalysts to estimate the thermodynamic parameters. The impregnation with ((NH4)(2)SO4 improves thermal resistance of the char obtained from carbonization. The catalysts exhibit higher adsorption capacity than CAG (without metal), indicating chemical interaction between ammonia and metals. The metal-ammonia interaction is stronger on Fe than on Ni catalyst, which is consistent with reported theoretical calculations