Application of natural minerals for in-situ catalytic pyrolysis of orange peel

Abstract

Natural mineral catalysts dolomite and clinoptilolite were evaluated in their calcined and non-calcined form for application in the catalytic in-situ pyrolysis of orange peel. Biomass pyrolysis improved when using calcined catalysts, with an increase in biogas yields (5.4 and 5.2% increase for dolomite and clinoptilolite, respectively), while non-calcined catalysts promoted higher condensate yields with an increment of 21.3 and 16.2% for dolomite and clinoptilolite compared with the calcined catalyst tests. Characterization of the condensate fraction with GC-MS showed formation of less oxygenated organic molecules in the pyrolysis tests, with an increase of 66% and 139% in the relative areas of organic compounds with an atomic content lower than 20%, when calcined dolomite and clinoptilolite were used, respectively, compared with the non-calcined catalysts. A prominent formation of Limonene was also observed. Syngas analysis with GC-TCD showed calcined clinoptilolite promoted higher hydrogen contents, while calcined dolomite showed increased CO and CO2 production at the highest pyrolysis temperatures. The presence of catalyst almost always pro-moted higher primary gas generation when compared with the non-catalytic test. The kinetic study of the catalytic pyrolysis of orange peel showed calcination of the natural minerals promotes a decrease in the apparent activation energy and an increase in the kinetic constant of the process, which shows the promising application of natural minerals as catalysts for biomass pyrolysis applications.