Catalysts For Catalytic Pyrolysis Research Articles

Exploring the potential of clay catalysts in catalytic pyrolysis of mixed plastic waste for fuel and energy recovery

Developing low-cost and high-activity catalysts is one of the keys to promoting the catalytic pyrolysis of waste plastics to fuels for plastic recycling. This work studied the effect of clay as the catalyst on mixed plastic pyrolysis for fuel and energy recovery. Four kinds of clay, including nanoclay, montmorillonite, kaolin, and hydrotalcite, were used as catalysts for the pyrolysis of mixed plastic consisted of polyethylene terephthalate, polystyrene, polypropylene, low-density polyethylene, and high-density polyethylene. The product yield and distribution varied with different clay in pyrolysis. The highest yield of oil was 71.0 % when using montmorillonite as the catalyst. While the highest contents of gasoline range hydrocarbons and diesel range hydrocarbons in the oil were achieved when using kaolin and nanoclay, respectively as catalysts. For the gas products, the CO, C2H4, C2H6, C3H6, and C4H10 increased with decreased CO2 in the gaseous products when using clay as catalysts. In general, the mild acidity of clay catalyst was essential to improve the oil yields and the proportion of the gasoline or diesel range fuels in the catalytic pyrolysis of mixed plastic waste.

Ex Situ Catalytic Pyrolysis of Invasive Pennisetum purpureum Grass with Activated Carbon for Upgrading Bio-Oil

Energy demands keep increasing in this modern world as the world population increases, which leads to a reduction in fossil fuels. To resolve these challenges, Pennisetum purpureum, an invasive grass in Brunei Darussalam, was examined as the feedstock for renewable energy through a catalytic pyrolysis process. The activated carbon was applied as the catalyst for a simple and economical solution. The catalytic pyrolysis was executed at 500 °C (the temperature for the highest biofuel yield) for both reactors to produce the highest amount of upgraded biofuels. The biochar produced from the non-catalytic and catalytic pyrolysis processes showed a consistent yield due to stable operating conditions, from which the activated carbon was generated and used as the catalyst in this work. A significant amount of improvement was found in the production of biofuels, especially bio-oil. It was found that for catalysts, the number of phenolic, alcohol, furans, and ketones was increased by reducing the amount of acidic, aldehyde, miscellaneous oxygenated, and nitrogenous composites in bio-oils. The highest amount of phenolic compounds was produced due to a number of functional groups (-C=O and -OH) in activated carbon. The regenerated activated carbons also showed promising outcomes as catalysts for upgrading the bio-oils. The overall performance of synthesized and regenerated activated carbon as a catalyst in catalytic pyrolysis was highly promising for improving the quality and stability of bio-oil.

Pretreatment of HZSM-5 with organic alkali and cobalt: Application in catalytic pyrolysis of lignin to produce monocyclic aromatic hydrocarbons

In this work, we adopted organic alkali and cobalt pretreated HZSM-5 zeolites as catalysts for monocyclic aromatic hydrocarbons production via catalytic fast pyrolysis of lignin in a two-stage fixed bed reactor. For the treatment, four kinds of organic hydroxides (tetraalkylammonium hydroxides, denoted as TMAOH, TEAOH, TPAOH, and TBAOH) were chosen as the desilication agent, and cetyltrimethylammonium bromide (CTAB) was introduced as assistant to control the pretreating process. In addition, cobalt modification was further conducted over the optimized alkali-treated sample for acidity adjustment. The treated zeolites were systematically characterized by XRD, SEM, NH3-TPD, and N2-adsorption/desorption techniques. The characterization results were analyzed together with the catalytic testing data to reveal the structure-function relationship of the catalysts in catalytic pyrolysis of lignin. As it turned out, the HZSM-5 zeolite pretreated by 0.5 mol/L of TPAOH in the presence of CTAB exhibits a coordinated micropore/mesopore proportion, proper average mesopore size, and a successful preservation of acidic properties. The addition of CTAB in the alkali treatment process was not only beneficial to preventing the over-treatment of HZSM-5, but could also regulate the mesoporous structure of zeolite. Eventually, the highest production of monocyclic aromatic hydrocarbons (31.8%, relative content) was achieved by the TPAOH pretreated HZSM-5 (2C-0.5TPHZ) at 500 °C, far exceeding that of the parent HZSM-5 (17.3%, relative content). Further modification of the 2C-0.5TPHZ sample with 1 wt% of cobalt could enhance the acidity of the alkali-treated zeolite, leading to a further improvement of the monocyclic aromatic hydrocarbons production to 38.3%. The reusability of the pretreated sample was further evaluated by cyclic reaction for 5 times, which demonstrated its reactivity stability for monocyclic aromatic hydrocarbons production.

Enhancement of hydrocarbons and phenols in catalytic pyrolysis bio-oil by employing aluminum hydroxide nanoparticle based spent adsorbent derived catalysts

The present study investigated the effects of metal loaded spent adsorbent as catalyst for the catalytic pyrolysis of pine needle biomass. Metal active sites (Ni, Fe, Cu, Zn and Mo) were introduced in alumina matrix by wet impregnation process. Non-catalytic and catalytic semi-batch pyrolysis study was carried out at conditions: 550 °C temperature, 50 °C min−1 heating rate and 200 mL min−1 N2 flow rate. Results indicated significant deoxygenation potential 3.33–35.57% of the applied catalysts towards oxygenated compounds by converting them into their corresponding hydrocarbon (27.70–36.41%) and phenolic (40.41–46.04%) derivatives. Among all the catalysts, Ni/Al and Fe/Al produced the highest quality bio-oil by enriching their carbon content to 62.93 and 60.14% and heating value to 31.41 and 26.86 MJ kg−1, respectively. Moreover, significant enhancement in their hydrocarbons (36.41 and 36.01% for Ni/Al and Fe/Al, respectively) and phenolic compounds (46.04 and 41.67% for Ni/Al and Fe/Al, respectively) from 9.15% hydrocarbons and 13.32% phenols in non-catalytic bio-oil had also been observed. Presence of CO and CO2 in the evolved gases also represented the occurrence of deoxygenation reactions during catalytic breakdown. Hydrocarbon and phenol-rich bio-oil can find its application either as a replacement for petroleum fuel or an industrial-grade chemical. Thus, catalysts derived from spent aluminum hydroxide nanoparticle adsorbent can act as an effective substitute for the currently utilized high-cost catalysts in catalytic pyrolysis of biomass.

Influence of calcium promoter on catalytic pyrolysis characteristics of iron-loaded brown coal in a fixed bed reactor

The Fe–Ca catalysts in catalytic pyrolysis of brown coals were studied to investigate the catalytic activity of the Fe–Ca in a fixed-bed reactor. Experimental results showed the maximum yields of the light aromatic hydrocarbons (LAHs) were 5.90 wt% (0.88 wt% of benzene, toluene and xylene ‘BTX’, 4.10 wt% of phenol and cresol ‘PC’ and 0.92 wt% of naphthalene) when the 1.5% Ca was added into 5% Fe-loaded brown coal. The yields of water and gas significantly reduced, the tar yield gradually increased with increasing heating rate. The characterization results indicated that when calcium promoter was impregnated with iron, Ca2Fe2O5, CaO, Fe2O3 and α-Fe were formed on the surface of the coal char, Ca2Fe2O5 and α-Fe decomposed polyaromatic tar, CaO and Fe2O3 accelerated water gas shift reaction to enhance the H2 yield, the Fe2O3 and Ca2Fe2O5 could be reduced to α-Fe by volatiles (C, CO and H2) under high temperature catalytic pyrolysis. The synergistic effects between iron and calcium improved brown coal pyrolysis and the volatiles such as free radical fragments were further pyrolyzed, indicating that Fe–Ca catalysts inhibited α-Fe deactivation by tar and carbon deposition, thus promoting brown coal pyrolysis and formation of COx, H2 and LAHs.

Aromatics production with metal oxides and ZSM-5 as catalysts in catalytic pyrolysis of wood sawdust

Dual catalysts are proposed in this study to convert biomass pyrolysis vapors into aromatics. Metal oxides (CaO, Al2O3, and ZnO) and ZSM-5 were introduced into the catalytic upgrading process. In the pyrolysis process without ZSM-5, the addition of CaO effectively removed carboxylic organics and methoxyphenols, reducing the product yield with a hydrogen to carbon ratio of 0, and the size of phenol compounds. The addition of Al2O3 greatly promoted the cracking of oxygenates with molecular weight above 109 g mol−1, such as large-size methoxyphenols and sugars. It is found that the upgraded pyrolysis volatiles are more conducive to conversion for aromatics with a ZSM-5 catalyst. The addition of CaO increased the selectivity of xylene (15.9%), while Al2O3 promoted the selectivity of toluene (18.3%). The highest yield of aromatics was obtained with CaO-ZSM-5 dual catalyst system, which was boosted by 6.14% compared to that of pure ZSM-5. To explore more effective methods for aromatics production, the arrangement of catalysts and temperature condition were investigated. Mixing CaO with biomass produced more aromatics than other methods, and the most suitable temperature for the formation of aromatic hydrocarbons was 600 °C.

Green Biofuel Production via Catalytic Pyrolysis of Waste Cooking Oil using Malaysian Dolomite Catalyst

Malaysian Dolomite has shown potential deoxygenation catalyst due to high capacity in removing oxygen compound and produce high quality of biofuel with desirable lighter hydrocarbon (C8-C24). The performance of this catalyst was compared with several commercial catalysts in catalytic pyrolysis of Waste Cooking Oil. Calcination at 900 °C in N2 produced catalyst with very high activity due to decomposition of CaMg(CO3)2 phase and formation of MgO-CaO phase. The liquid product showed similar chemical composition of biofuel in the range of gasoline, kerosene and diesel fuel. Furthermore, Malaysian Dolomite showed high reactivity with 76.51 % in total liquid hydrocarbon and the ability to convert the oxygenated compounds into CO2, CO, CH4, H2, hydrocarbon fuel gas, and H2O. Moreover, low acid value (33 mg KOH/g) and low aromatic hydrocarbon content were obtained in the biofuel. Thus, local calcined carbonated material has a potential to act as catalyst in converting waste cooking oil into biofuel.

Catalytic pyrolysis of waste polypropylene using Ahoko kaolin from Nigeria

The aim of this study is to convert polypropylene waste into usable liquid fuel via pyrolysis technique using kaolin as a low-cost catalyst. Waste polypropylene was thermally and catalytically degraded in a chemical vapour deposition (CVD) horizontal glass reactor at a temperature of 450 °C, residence time of 30 min, and heating rate of 30 °C/min. The kaolin clay was characterized by XRF analysis while the ultimate and proximate analysis of the polypropylene feed carried out gave combustible materials content of 93.77 wt%, fixed carbon of 1.62 wt%, calorific value of 45.20 MJ/kg and elemental composition with carbon (83.65%), hydrogen (14.27%), oxygen (0.15%), sulphur (0.1%), chlorine (1.16%), and nitrogen (0.67%). Thermal cracking was carried out in the absence of catalyst and the process gave a yield of liquid, gaseous, and solid products of 67.48, 8.85, and 23.67 wt%, respectively. Furthermore, kaolin clay was employed as a catalyst in catalytic pyrolysis of the same feedstock for catalyst-to-plastic ratio of 1:1, 1:2, 1:3, and 1:4 at the same operating parameters as in thermal cracking. Optimum yield was obtained at a catalyst-to-plastic ratio of 1:3 with a yield of 79.85, 1.48, and 18.67 wt% for liquid, gaseous, and solid products, respectively. The liquid products obtained for both thermal and catalytic cracking at optimum conditions were characterized for their suitability as fuel. The properties determined were density, viscosity, flash point, fire point, pour point, and calorific value. The results suggest that catalytic pyrolysis produced liquid products, whose properties are comparable to conventional fuels (gasoline and diesel oil) than that produced through thermal pyrolysis. FTIR analysis of the liquid product from catalytic pyrolysis also shows that it contains hydrocarbons with different functional groups such as aromatics, olefins, carbonyl, amines, sulphides, and hydroxyl.

The effect of industrial waste coal bottom ash as catalyst in catalytic pyrolysis of rice husk for syngas production

Comparison between industrial waste coal bottom ash catalyst and commercial catalysts (nickel and natural zeolite) in catalytic pyrolysis of rice husk were investigated in this study. Characterization through X-ray fluorescence (XRF), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and energy disperse X-ray analysis (EDX), and Brunauer–Emmett–Teller analysis (BET) were carried out to understand the physiochemical activity of the catalysts in pyrolysis of rice husk. The catalyst to rice husk ratio of 0.1 was pyrolyzed in the temperature range of 323–1173 K using thermogravimetric analyzer coupled with mass spectrometer (TGA-MS) equipment to investigate the effect of catalysts in thermal degradation behavior of biomass and syngas production. The study revealed that lowest coke formation (3.65 wt%) associated with high syngas (68.3 vol%) were attained in catalytic pyrolysis using coal bottom ash catalyst compared to nickel and natural zeolite catalysts. Moreover, the hydrogen concentration had increased 8.4 vol% in catalytic pyrolysis of rice husk using coal bottom ash catalyst compared to non-catalytic pyrolysis.

Thermal and catalytic pyrolysis of plastic waste

The amount of plastic waste is growing every year and with that comes an environmental concern regarding this problem. Pyrolysis as a tertiary recycling process is presented as a solution. Pyrolysis can be thermal or catalytical and can be performed under different experimental conditions. These conditions affect the type and amount of product obtained. With the pyrolysis process, products can be obtained with high added value, such as fuel oils and feedstock for new products. Zeolites can be used as catalysts in catalytic pyrolysis and influence the final products obtained.

ChemInform Abstract: Catalysts and Sorbents for Thermochemical Conversion of Biomass to Renewable Biofuels — Material Development Needs

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