Alfredo Valarezo

Dr. Alfredo Valarezo

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Research Focus & Metrics

Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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22 July 2011 in Journal of Thermal Spray Technology
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Journal Article
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AVAlfredo Valarezo
Alfredo Valarezo
SSSanjay Sampath
Sanjay Sampath

11 August 2020 in Journal of Thermal Spray Technology
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Journal Article
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AVAlfredo Valarezo
Alfredo Valarezo
KSKentaro Shinoda
Kentaro Shinoda
SSSanjay Sampath
Sanjay Sampath

13 May 2020 in Journal of Thermal Spray Technology
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Journal Article
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FOFelipe Oviedo
Felipe Oviedo
AVAlfredo Valarezo
Alfredo Valarezo

4 July 2024 in Polymers
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Journal Article
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Diego VenegasDiego Venegas
Diego Venegas
LOLourdes M. Orejuela-Escobar
Lourdes M. Orejuela-Escobar
AVAlfredo Valarezo
Alfredo Valarezo
Victor H. GuerreroVictor H. Guerrero
Victor H. Guerrero
LTLuis Tipanluisa
Luis Tipanluisa
Serguei Alejandro-MartínSerguei Alejandro-Martín
Serguei Alejandro-Martín
Catalytic biomass pyrolysis is one of the most promising routes for obtaining bio-sustainable products that replace petroleum derivatives. This study evaluates the production of aromatic compounds (benzene, toluene, and xylene (BTX)) from the catalytic pyrolysis of lignocellulosic biomass (Pinus radiata (PR) and Eucalyptus globulus (EG)). Chilean natural zeolite (NZ) was used as a catalyst for pyrolysis reactions, which was modified by double ion exchange (H2NZ) and transition metals impregnation (Cu5H2NZ and Ni5H2NZ). The catalysts were characterized by nitrogen adsorption, X-ray diffraction (XRD), ammonium programmed desorption (TPD-NH3), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) allowed us to study the influence of natural and modified zeolite catalysts on BTX production. XRD analysis confirmed the presence of metal oxides (CuO and NiO) in the zeolite framework, and SEM-EDS confirmed successful metal impregnation (6.20% for Cu5H2NZ and 6.97% for Ni5H2NZ). Py-GC/MS revealed a reduction in oxygenated compounds such as esters, ketones, and phenols, along with an increase in aromatic compounds in PR from 2.92% w/w (without catalyst) to 20.89% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/5, and in EG from 2.69% w/w (without catalyst) to 30.53% w/w with Ni5H2NZ at a biomass/catalyst ratio of 1/2.5. These increases can be attributed to acidic sites within the catalyst pores or on their surface, facilitating deoxygenation reactions such as dehydration, decarboxylation, decarbonylation, aldol condensation, and aromatization. Overall, this study demonstrated that the catalytic biomass pyrolysis process using Chilean natural zeolite modified with double ion exchange and impregnated with transition metals (Cu and Ni) could be highly advantageous for achieving significant conversion of oxygenated compounds into hydrocarbons and, consequently, improving the quality of the condensed pyrolysis vapors.

9 October 2014 in Journal of Thermal Spray Technology
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Journal Article
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AVAlfredo Valarezo
Alfredo Valarezo
GDG. Dwivedi
G. Dwivedi
SSS. Sampath
S. Sampath
RMR. Musalek
R. Musalek
JMJ. Matejicek
J. Matejicek

14 June 2024 in Zoosystematics and Evolution
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JMJorge L. Montalvo-Salazar
Jorge L. Montalvo-Salazar
MBM. Lorena Bejarano
M. Lorena Bejarano
AVAlfredo Valarezo
Alfredo Valarezo
DCDiego F. Cisneros-Heredia
Diego F. Cisneros-Heredia
The diversity of Neotropical velvet worms (Onychophora, Neopatida) is significantly underestimated, particularly within the Andean clade represented by the genus Oroperipatus, the last species of which was described more than 70 years ago. Here, we describe a new species of Oroperipatus from the Amazonian lowlands of Ecuador, bringing the total number of described species on mainland Ecuador to seven and in western Amazonia to three. The new species, Oroperipatus tiputini sp. nov., can be distinguished from its congenerics by the following combination of characters: two variations of primary papillae alternated between dorsal plicae; four scale ranks in the apical piece of primary papillae; reduced fifth spinous pad of legs IV and V; four supraocular papillae; occasionally reduced anterior papilla; males with two crural tubercles per leg in the first pregenital pair and a single crural tubercle per leg in the next pair; and some accessory papillae with one lateral rudimentary apical piece. We also discuss novel morphological similarities and differences with other Neopatida genera, as revealed by scanning electron microscopy (SEM).