Guomin Xiao

Catalytic fast pyrolysis of straw biomass in an internally interconnected fluidized bed to produce aromatics and olefins: Effect of different catalysts

A novel reactor, named internally interconnected fluidized bed (IIFB), was specially designed for catalytic fast pyrolysis (CFP) of straw biomass. Catalytic characteristics of four types of catalysts (ZSM-5, LOSA-1, Gamma-Al2O3 and spent FCC catalysts) for producing aromatics and olefins were investigated in this reactor. The results show that IIFB reactor can realize CFP process. The maximum carbon yields of aromatics (12.8%) and C2-C4 olefins (10.5%) were obtained with ZSM-5. ZSM-5 shows the highest selectivity of naphthalene (12.1%), whereas spent FCC catalyst presents the highest selectivity of benzene (45.5%). The selectivity of ethylene and propylene are equal in the present of ZSM-5 and LOSA-1. Gamma-Al2O3 and spent FCC catalysts show a higher selectivity of ethylene than that of propylene. This paper provides a new reactor for CFP process and some suggestions for choosing catalyst.

Biomass catalytic pyrolysis to produce olefins and aromatics with a physically mixed catalyst.

Zeolite catalysts with micropores present good catalytic characteristics in biomass catalytic pyrolysis process. However, large-molecule oxygenates produced from pyrolysis cannot enter their pores and would form coke on their surfaces, which decreases hydrocarbon yield and deactivates catalyst rapidly. This paper proposed adding some mesoporous and macroporous catalysts (Gamma-Al2O3, CaO and MCM-41) in the microporous catalyst (LOSA-1) for biomass catalytic pyrolysis. The added catalysts were used to crack the large-molecule oxygenates into small-molecule oxygenates, while LOSA-1 was used to convert these small-molecule oxygenates into olefins and aromatics. The results show that all the additives in LOSA-1 enhanced hydrocarbon yield obviously. The maximum aromatic+olefin yield of 25.3% obtained with 10% Gamma-Al2O3/90% LOSA-1, which was boosted by 39.8% compared to that obtained with pure LOSA-1. Besides, all the additives in LOSA-1 improved the selectivities of low-carbon components in olefins and aromatics significantly.

Catalytic pyrolysis of black-liquor lignin by co-feeding with different plastics in a fluidized bed reactor

Catalytic co-pyrolysis of black-liquor lignin and waste plastics (polyethylene, PE; polypropylene PP; polystyrene, PS) was conducted in a fluidized bed. The effects of temperature, plastic to lignin ratio, catalyst and plastic types on product distributions were studied. Both aromatic and olefin yields increased with increasing PE proportion. Petrochemical yield of co-pyrolysis of PE and lignin was LOSA-1 > spent FCC > Gamma-Al2O3 > sand. The petrochemical yield with LOSA-1 is 43.9% which is more than two times of that without catalyst. The feedstock for co-pyrolysis with lignin is polystyrene > polyethylene > polypropylene. Catalytic co-pyrolysis of black-liquor lignin with PS produced the maximum aromatic yield (55.3%), while co-pyrolysis with PE produced the maximum olefin yield (13%).

Co-catalytic pyrolysis of biomass and waste triglyceride seed oil in a novel fluidized bed reactor to produce olefins and aromatics integrated with self-heating and catalyst regeneration processes

The catalytic and co-catalytic pyrolysis of rice stalk and waste seed oil to produce olefins and aromatics were conducted in a novel reactor named the internally interconnected fluidized bed (IIFB) reactor. The IIFB system was specially designed for the catalytic pyrolysis of biomass, integrated with self-heating and catalyst regeneration functions in a single-bed reactor. The results show that catalytic fast pyrolysis of rice stalk produced up to a 20% total petrochemical (aromatic + olefin) carbon yield over an experimental time of 3 h. Co-catalytic fast pyrolysis of rice stalk and waste oil dramatically increased the petrochemical yield. A petrochemical yield of 64.8% was obtained at H/Ceff = 1.2. The pyrolysis and combustion temperatures were very stable, while char combustion and catalyst regeneration proceeded well in the reactor. This paper provides a new pathway for the catalytic fast pyrolysis of biomass and some insights into how biomass resources can be used more efficiently to produce renewable petrochemicals.

Catalytic conversion of biomass pyrolysis-derived compounds with chemical liquid deposition (CLD) modified ZSM-5.

Chemical liquid deposition (CLD) with KH550, TEOS and methyl silicone oil as the modifiers was used to modify ZSM-5 and deposit its external acid sites. The characteristics of modified catalysts were tested by catalytic conversion of biomass pyrolysis-derived compounds. The effects of different modifying conditions (deposited amount, temperature, and time) on the product yields and selectivities were investigated. The results show KH550 modified ZSM-5 (deposited amount of 4%, temperature of 20°C and time of 6h) produced the maximum yields of aromatics (24.5%) and olefins (16.5%), which are much higher than that obtained with original ZSM-5 catalyst (18.8% aromatics and 9.8% olefins). The coke yield decreased from 44.1% with original ZSM-5 to 26.7% with KH550 modified ZSM-5. The selectivities of low-molecule-weight hydrocarbons (ethylene and benzene) decreased, while that of higher molecule-weight hydrocarbons (propylene, butylene, toluene, and naphthalene) increased comparing with original ZSM-5.

Biodiesel production in a membrane reactor using MCM-41 supported solid acid catalyst.

Production of biodiesel from the transesterification between soybean oil and methanol was conducted in this study by a membrane reactor, in which ceramic membrane was packed with MCM-41 supported p-toluenesulfonic acid (PTSA). Box-Behnken design and response surface methodology (RSM) were used to investigate the effects of reaction temperature, catalyst amount and circulation velocity on the yield of biodiesel. A reduced cubic model was developed to navigate the design space. Reaction temperature was found to have most significant effect on the biodiesel yield while the interaction of catalyst amount and circulation velocity have minor effect on it. 80°C of reaction temperature, 0.27 g/cm(3) of catalyst amount and 4.15 mL/min of circulation velocity were proved to be the optimum conditions to achieve the highest biodiesel yield.

Performance of hierarchical HZSM-5 zeolites prepared by NaOH treatments in the aromatization of glycerol

A series of hierarchical HZSM-5 zeolites were prepared by post-synthesis modification of conventional bulk crystals of HZSM-5 zeolite with sodium hydroxide (NaOH) solution at different concentrations. These micro–mesoporous composite molecular sieves were characterized by powder X-ray diffraction, transmission electron microscopy, nitrogen adsorption, Fourier transform infrared (FT-IR) spectroscopy techniques and pyridine FT-IR to investigate the changes in crystallinity, acidity, morphology and textural property of HZSM-5 zeolite before and after alkaline treatment. The catalytic performances of these hierarchical HZSM-5 zeolites were evaluated by the aromatization of glycerol with methanol as the solvent, which was a promising route for converting renewable glycerol and methanol into high value aromatics. Substantial mesoporosity with sizes centered at around 4 nm could be generated for HZSM-5 zeolites after treatment with mild NaOH solution (≤0.4 M), coupled with improved retained microporosity, resulting in great improvements in catalytic lifetime and selectivity to benzene, toluene and xylene (BTX) aromatics during the reaction of glycerol to aromatics. Although the larger mesopore surface areas were achieved when treated with NaOH concentrations that were higher than 0.5 M, the HZSM-5 structure was partly damaged, leading to the reduction of catalytic lifetime and selectivity to BTX aromatics. The HZSM-5 treated with 0.3 M NaOH solution was found to be the optimum catalyst for the transformation of glycerol/methanol to aromatics, producing a nearly two-fold increase in BTX aromatics (carbon yields of 25.18%) and three-fold improvement in catalyst lifetime (12.5 h) when compared to the parent microporous HZSM-5 (13.9% carbon yields of BTX aromatics and catalyst lifetime of 4 h). These improved catalytic performances are mainly attributed to the optimized bimodal micro–mesoporous HZSM-5 zeolite during the alkali treatment, which retained sufficient micropores that have the capacity for aromatization and also more mesopores were created that would shorten the average diffusion path lengths, increase the accessibility to the acid sites and facilitate the transportation of large molecules, e.g., glycerol and carbon precursors, during the aromatization of glycerol.

Catalytic pyrolysis of natural algae over Mg-Al layered double oxides/ZSM-5 (MgAl-LDO/ZSM-5) for producing bio-oil with low nitrogen content

Cyanobacteria were catalytically pyrolyzed over Mg-Al layered double oxide/ZSM-5 composites (MgAl-LDO/ZSM-5) to produce bio-oil. MgAl-LDO/ZSM-5 with a Mg/Al molar ratio of four was proved to be the best catalyst. Under the optima condition that the final temperature was 823K, heating rate was 10K/min and catalyst/algae mass ratio was 0.75, a maximum yield of liquid (41.1%) was achieved at 823K with a heating rate of 10K/min and a catalyst/algae mass ratio of 0.75, which was much higher than the one obtained without catalyst. The element analysis results proved that this bio-oil had much lower O/C molar ratio and higher HHV. The GC-MS results showed that the bio-oil had less nitrogenous compounds. MgAl4-LDO/ZSM-5 was proved to be an applicable and effective catalyst to obtain bio-oil from catalytic pyrolysis of water-blooming algae.

Promoting effect of Ce on a Cu–Co–Al catalyst for the hydrogenolysis of glycerol to 1,2-propanediol

In this work, a series of Cu–Co–Al catalysts with different Ce loadings were applied to the hydrogenolysis of glycerol to 1,2-propanediol in a fixed-bed flow reactor. The physicochemical properties of the synthesized catalysts were analyzed using BET, N2O chemisorption, SEM, TEM, XRD, H2-TPR, NH3-TPD and XPS techniques. Systematic characterization demonstrated that the incorporation of Ce into the Cu–Co–Al catalyst could effectively restrain the aggregation of active metal species as well as the growth of metallic particles during calcination and reduction, which resulted in the formation of highly dispersed active metals. Large amounts and superior strength of acid sites were present in the Ce-promoted Cu–Co–Al catalysts, as confirmed by NH3-TPD analysis. The reducible nature of the Cu–Co–Al catalyst greatly increased after the addition of Ce. The higher concentration of acid sites, excellent reducibility and highly dispersed active metals were responsible for the superior catalytic activity of the 8Ce/Cu–Co–Al catalyst and it attained 91.6% glycerol conversion and 92.4% 1,2-propanediol selectivity. In addition, the effects of different process parameters such as the solvent, reaction temperature, operating pressure, catalyst loading, glycerol concentration and liquid flow rate on glycerol hydrogenolysis together with the catalyst stability were studied in detail, showing that the Ce-promoted Cu–Co–Al catalyst had high efficiency and stability for glycerol hydrogenolysis.

The growth mode of ZnO on HZSM-5 substrates by atomic layer deposition and its catalytic property in the synthesis of aromatics from methanol

A series of ZnO/HZSM-5 catalysts were prepared by atomic layer deposition (ALD) with different cycle numbers and tested for methanol to aromatics (MTA) reactions. The growth rate of Zn content monotonically decreases with increasing number of deposition cycles due to the “half-self-limiting” ALD-type growth mode for ZnO on HZSM-5 zeolite, in which the density of the regenerated reactive –OH sites in the HZSM-5 substrates was less than that of the consumed –OH sites in one cycle. The deposited ZnO existed as small nanocrystallites upon low ALD cycles. However, as the number of ALD cycles exceeds a certain value, the resulting ZnO grown on the HZSM-5 substrate exists in the form of a continuous coating with corrugated surfaces, which could effectively prevent damage to the HZSM-5 framework caused by exposure of the zeolite skeleton to steam during the reaction and regeneration processes. The ZnO/HZSM-5 catalyst treated with 40 ALD cycles was proved to be the optimum catalyst for MTA reactions, producing a nearly twofold increase in BTX aromatics (carbon yield of 60.3%) than the parent HZSM-5 (28.3% carbon yield of BTX aromatics). The catalyst prepared by ALD not only is more effective for the aromatization of methanol but also shows a more stable performance in the MTA process than that prepared by conventional methods (i.e. IWI and IE) with a comparable amount of Zn content. This better performance could be ascribed to the synergetic effect that occurred between the multinuclear oxygenated zinc sites and (ZnOH)+ sites formed during the ALD process, which would boost the transformation of inert low alkanes to aromatics.