Procesamiento catalítico de bio-oils para su uso como fuente energética y de materias primas

Abstract

Se estudió el procesamiento catalítico de bio-oils derivados de la pirólisis de biomasa lignocelulósica, utilizándolos como co-reactivos de alimentaciones convencionales en refinerías. Subsidiariamente se desarrollaron técnicas adecuadas para la caracterización de los bio-oils y para la solución de inconvenientes que posiblemente pueden surgir durante el co-procesamiento, como la formación significativa de depósitos carbonosos, y se investigó la performance catalítica de catalizadores equilibrados de FCC sobre tales bio-oils. Los bio-oils fueron producidos en un reactor de lecho fijo, utilizando diferentes temperaturas de pirólisis (entre 300 y 650 ºC) y materias primas (aserrines de algarrobo, de álamo y de pino, y cáscara de trigo) con el objetivo de maximizar la producción de líquidos. Los bio-oils fueron acondicionados térmicamente en un reactor batch bajo diferentes condiciones (temperaturas entre 350 y 550 ºC y rampas de calentamiento entre 8 y 12 ºC/min) para reducir su potencial de formación de coque, disminuyendo la concentración de precursores. Se realizaron experiencias de conversión catalítica de compuestos modelos individuales representativos de los principales grupos químicos presentes en los bio-oils, de un bio-oil sintético generado en el laboratorio, del bio-oil de aserrín de pino y del producto líquido de su tratamiento térmico en un reactor de lecho fijo a 500 ºC. Las experiencias de co-procesamiento del bio-oil de aserrín de pino y del producto líquido de su tratamiento térmico con gas oil de vacío (VGO) se realizaron en un reactor Simulador de Riser CREC.

The catalytic co-processing of bio-oils derived from the pyrolysis of lignocelulosic biomass was studied by using them as co-reactants with conventional feedstocks in the process of catalytic cracking of hydrocarbons (FCC). Techniques to characterize the bio-oils and to solve potential problems during co-processing, such as higher coke yields, were also developed. The performance of commercial equilibrium FCC catalysts was addressed. The bio-oils were produced in a fixed bed reactor, using different pyrolysis temperatures between 350 and 650 ºC in order to maximize liquid yields. Various raw materials, such poplar, mesquite and pine sawdusts, and wheat shell, were used.The bio-oils were conditioned to decrease their coke-forming potential by means of a thermal treatment in a batch reactor under different conditions (heating ramps between 8 and 12 ºC/min and final temperatures between 350 and 550 ºC), aimed at reducing the concentration of coke precursors. Individual model compounds representing the main chemical groups in bio-oils, a synthetic bio-oil prepared by mixing model compounds, the bio-oil from pine sawdust and the liquid product from its thermal conditioning were reacted in a fixed bed reactor at 500 ºC. The experiments of co-processing bio-oil and the liquid product from its thermal conditioning together with vacuum gas oil (VGO) were performed in a CREC Riser Simulator reactor under conditions of the commercial process. The cracking of the mixtures yielded more C2-C4 olefins and less liquid hydrocarbons than the VGO feedstock. Coke yields were in the usual range of the commercial process, between 3.5 and 5.5 %wt.