Selective production of chemicals from biomass pyrolysis over metal chlorides supported on zeolite

Enzymatic treatment improves fast pyrolysis product selectivity of softwood and hardwood lignin

Fast pyrolysis of lignin is still struggling in efficiency and scalable utilization. The low product selectivity thereby represents one of the most challenging issues. White-rot fungi have been widely used in bio-pretreatment of lignocellulosic biomass, where ligninolytic enzymes have been evidenced to modify lignin structures and enhance bio-refining efficiency. We thus treated lignin from both softwood (ginkgo) and hardwood (poplar) with enzymatic cocktail from white-rot fungus for fast pyrolysis. Both ginkgo and poplar lignin had much improved product selectivity at lower temperature after enzymatic modification, in particular, the 2-methoxy-phenol production from ginkgo lignin. Besides the improved product selectivity, the residue bio-char from pyrolysis had much improved surface area with more porous structures. Mechanistic study showed that the improvement of lignin pyrolysis products might attribute to demethoxylation and interunit linkage cleavage of lignin during enzymatic treatment. All these results highlighted that the product selectivity and bio-char performances have been synergistically improved by enzymatic treatment, which could thus pave a new way for enhancing fast pyrolysis efficiency. Overall, using softwood and hardwood lignin, this research has presented a new strategy using ligninolytic enzyme to modify lignin for synergistically improving product selectivity and bio-char performances, which opened up a new avenue for lignin valorization.

Pyrolysis of palm kernel shell with internal recycling of heavy oil

This paper investigated pyrolysis of palm kernel shell in a proposed reactor, which is characterized by internal recycling of heavy oil between a heavy oil sorption zone and pyrolysis zone. The internal recycling of heavy oil favors conversion of heavy oil to char, gas, and light oil. Compared with the product distribution from the conventional pyrolysis without heavy oil recycling, the yields of char, gas, and GC/MS detectable organic compounds increase from 34.8, 15.2, and 9.8 wt%-(dry feedstock) to 38.5, 19.0, and 16.9 wt%-(dry feedstock), respectively, with the help of internal recycling of heavy oil. The increases in the char and gas yields are interestingly found to be nearly equivalent. Furthermore, the yields of acetic acid and phenol in the resulting bio-oil can be as high as 10.1 and 2.7 wt%-(dry feedstock), and the outputs of 2-methylfuran, 2,6-dimethoxyphenol, and H₂ are increased by around 37, 7, and 4 times, respectively.

Effect of Zn/ZSM-5 and FePO4Catalysts on Cellulose Pyrolysis

A series of Zn/ZSM-5 catalysts with different Zn contents and FePO4were used to pyrolyze cellulose to produce value added chemicals. The nature of these catalysts was characterized by ammonia-temperature programmed desorption (NH3-TPD), IR spectroscopy of pyridine adsorption, and X-ray diffraction (XRD) techniques. Noncatalytic and catalytic pyrolytic behaviors of cellulose were studied by thermogravimetric (TG) technique. The pyrolytic liquid products, that is, the biooils, were analyzed by gas chromatography-mass spectrometry (GC-MS). The major components of the biooils are anhydrosugars such as levoglucosan (LGA), 1,6-anhydro-β-D-glucofuranose (AGF), levoglucosenone (LGO, 1,6-anhydro-3,4-dideoxy-β-D-pyranosen-2-one), and 1,4:3,6-dianhydro-α-D-glucopyranose (DGP), as well as furan derivatives, alcohols, and so forth. Zn/ZSM-5 samples with Brønsted and Lewis acid sites and the FePO4catalyst with Lewis acid sites were found to have a significant effect on the pyrolytic behaviors of cellulose and product distribution. These results show that Brønsted and Lewis acid sites modified remarkably components of the biooil, which could promote the production of furan compounds and LGO. On the basis of the findings, a model was proposed to describe the pyrolysis pathways of cellulose catalyzed by the solid acid catalysts.

Role of Brønsted acid in selective production of furfural in biomass pyrolysis

In this work, the role of Brønsted acid for furfural production in biomass pyrolysis on supported sulfates catalysts was investigated. The introduction of Brønsted acid was shown to improve the degradation of polysaccharides to intermediates for furfural, which did not work well when only Lewis acids were used in the process. Experimental results showed that CuSO4/HZSM-5 catalyst exhibited the best performance for furfural (28% yield), which was much higher than individual HZSM-5 (5%) and CuSO4 (6%). The optimum reaction conditions called for the mass ratio of CuSO4/HZSM-5 to be 0.4 and the catalyst/biomass mass ratio to be 0.5. The recycled catalyst exhibited low productivity (9%). Analysis of the catalysts by Py-IR revealed that the CuSO4/HZSM-5 owned a stronger Brønsted acid intensity than HZSM-5 or the recycled CuSO4/HZSM-5. Therefore, the existence of Brønsted acid is necessary to achieve a more productive degradation of biomass for furfural.

Fast pyrolysis product distribution of biopretreated corn stalk by methanogen

After pretreated by methanogen for 5, 15 and 25 days, corn stalk (CS) were pyrolyzed at 250, 300, 350, 400, 450 and 500 °C by Py-GC/MS and product distribution in bio-oil was analyzed. Results indicated that methanogen pretreatment changed considerably the product distribution: the contents of sugar and phenols increased; the contents of linear carbonyls and furans decreased; the contents of linear ketones and linear acids changed slightly. Methanogen pretreatment improved significantly the pyrolysis selectivity of CS to phenols especially 4-VP. At 250 °C, the phenols content increased from 42.25% for untreated CS to 79.32% for biopretreated CS for 5 days; the 4-VP content increased from 28.6% to 60.9%. Increasing temperature was contributed to convert more lignin into 4-VP, but decreased its content in bio-oil due to more other chemicals formed. The effects of biopretreatment time on the chemicals contents were insignificant.

Additives initiate selective production of chemicals from biomass pyrolysis

To improve chemicals selectivity under low temperature, a new method that involves the injection of additives into biomass pyrolysis is introduced. This method allows biomass pyrolysis to achieve high selectivity to chemicals under low temperature (300°C), while nothing was obtained in typical pyrolysis under 300°C. However, by using the new method, the first liquid drop emerged at the interval between 140°C and 240°C. Adding methanol to mushroom scrap pyrolysis obtained high selectivity to acetic acid (98.33%), while adding ethyl acetate gained selectivity to methanol (65.77%) in bagasse pyrolysis and to acetone (72.51%) in corncob pyrolysis. Apart from basic chemicals, one high value-added chemical (2,3-dihydrobenzofuran) was also detected, which obtained the highest selectivity (10.33%) in corncob pyrolysis through the addition of ethyl acetate. Comparison of HZSM-5 and CaCO3 catalysis showed that benzene emerged in the liquid because of the larger degree of cracking and hydrodeoxygenation over HZSM-5.