Experimental investigation of pyrolytic products obtained from biomass enabled with nano catalysts

Abstract

Conversion of biomass into more useful gaseous / liquid fuel is one of the thrust fields of interest for many researchers. Employing the rice husk as biomass, numerous reports dealt with the thermal and catalytic pyrolysis and their characterisations. However, many of the literature discuss only the production of oil / gaseous materials by changing the experimental conditions, catalyst, etc. Our work mainly focuses on the catalytic pyrolysis of rice husk enabled with nano size metallic and metal oxide particles in trace amounts, which promotes the yield of oil as well as gaseous fuel enriched with hydrogen. With the help of nano metallic / metallic oxide particles as catalyst, the cracking of rice husk was conducted at various temperatures and various kinds of hydrocarbons in volatile and non-volatile forms were produced. Initially, thermal distillation of rice husk was performed at different temperatures and the products obtained during the pyrolysis were collected and characterized through Fourier Transformed Infrared Spectrometer (FTIR), Gas Chromatography Mass Spectrometry (GC-MS) and Inductively Coupled Plasma - Optical Emission Spectrometry (ICP OES). Further, the solid product retained after the distillation process was subjected to steam gasification and the collected gaseous constituents were analysed using GC-MS. Besides the thermal cracking, the rice husk was also subjected to catalytic cracking by enabling with nickel, silver and nickel oxide nano particles synthesised in the laboratory by adopting wet chemical methods. The structural morphology of the synthesised metal/metal oxide particles was characterised through XRD, FESEM with EDAX. After evaluating the structural features, the nano metal particles like nickel, silver and the nickel oxide particles in meagre amount as catalyst (0.1 g, 0.2 g) were mixed with 30 g of rice husk and pyrolysis at various temperatures was performed. Rice husk enabled with nano size nickel particles produced tar, gaseous and carbonaceous rich char contents in varying proportions. The liquid and gaseous hydrocarbons were assessed by employing GC-MS and ICP-OES. In comparison with thermal pyrolysis (21.67%), the nickel catalytic pyrolysis offered more percentage of gaseous fuel (33.33%) at 400ºC. On analysing the tar obtained from both thermal and catalytic processes, it was found that the oil contained more percentage of aromatic contents than from the thermal process. The char obtained after catalytic pyrolysis favoured the formation of syn gas in higher amounts (H2 : 49.46%and CO : 32.32%) than the same formed from the char obtained in thermal pyrolysis (H2 : 38.24% and CO: 28.68%) at 750ºC. The catalytic pyrolysis performed using nano size silver particles produced different quantities of oil, tar and char. The products obtained were separately collected and characterized through GC-MS and ICP-OES. About 50 % of the solid biomass had been converted into more useful liquid and gaseous fuel. The quantity of H2 obtained in the silver catalysed pyrolysis was more (19.12%) in contrast to thermal pyrolysis which was attributable to the influence of silver nano particles towards the enhancement in hydrogen gas production. While using nickel oxide as catalyst, the biomass used produced different amounts of gas, oil and char. The non-condensable volatile collected was in higher amount during the pyrolysis performed at higher temperature. The gaseous constituents collected during the cracking process was subjected to GC-MS analysis; it revealed that at 500°C, the quantity of H2 gas obtained was maximum (12.41%). newline