Читать книгу Handbook of Biomass Valorization for Industrial Applications - Группа авторов - Страница 56

Aqueous phase reforming (APR) has certainly gained attention as most promising and suitable alternative for production of hydrogen as well as alkanes from lignocellulosic biomasses. The APR has several advantages over other methods as the reaction is wet or water-soluble feedstocks compatible, that can take place in both batch and continuous flow reactor, in a single step. As compared to conventional alkane steam reforming process, APR of carbohydrate is carried at relatively mild reaction conditions which facilitate water gas shift reaction leading to low CO production due to reduced decomposition rate of carbohydrates. However, in APR, methanation of CO₂ and production of alkanes/alcohols competitively lowers the H₂ yield [34–36]. Moreover, the type of starting raw material, design of reactor, reaction conditions and use of suitable catalyst cumulatively influence the APR reactions. APR was first popularized by Cortright et al. [37], who demonstrated mainly hydrogen production from oxygenated hydrocarbons extracted from renewable biomass and biomass waste streams. They carried the reaction at relatively low temperature and pressure (473–523 K, 15–50 bar) in single-reactor aqueous-phase reforming process using a Pt/Al₂O₃ catalyst and were able to generate hydrogen-rich fuel gas with high purity and yield. Since then, numerous substrates have been tested for H₂ production.

Valenzuela et al. [38], for very first time used woody biomass as APR raw material for direct production of H₂. They generated 18 vol% of H₂ by treating southern pine sawdust with H₂SO₄ followed by soluble products reforming using Pt/Al₂O₃ catalyst in a one pottwo-step process. In subsequent years, use degreased cotton, filter paper and microcrystalline cellulose as a raw material in place lignocellulosic biomass was adopted as an attractive choice for H₂/alkane production [39, 40]. As the chemical structure of feed molecule restrict the efficiency of hydrogen production, various studies have been undertaken to investigate ethylene glycol, glycerol, glucose, sucrose, sugars-derived polyols namely sorbitol and xylitol as starting material [36, 41–43]. It is suggested that xylitol and sorbitol are far more reliable raw material compared to glucose and cellulose giving fairly good H₂ yield. Although, APR process of production hydrogen rich biofuel from renewable sources is a smart approach, its cost of feedstock limits its applications at industrial level. However, recent studies have shown the utilization of biomass-derived organic compounds obtained from industrial wastewater as feedstock for APR process. Oliveira et al. [44] showed brewery wastewater as an interesting way of valorization to H₂-rich gas, thus, integrating wastewater treatment with waste-to-value added process. Zoppi et al. [45] recently proposed APR of water effluent derived from hydrothermal liquefaction to produce a gas mixture rich in hydrogen a well clean water effluent from its carbon content. Therefore, APR is an environmentally promising solution that can be used to subject different biomass derived raw material under suitable reaction conditions for selective production of H₂/alkanes.