Ex-situ Catalytic Pyrolysis Research Articles

Solar assisted catalytic thermochemical processes: pyrolysis and hydropyrolysis of Chlamydomonas reinhardtii microalgae

Thermochemical processes using solar energy are considered promising approaches. To improve the product properties, alternative techniques have also been investigated, including the use of catalyst and hydrogen atmosphere. These techniques individually have proved to be efficient to overcome some inherent challenges of this process. However, they have never been studied as an integrated process. Thus, in this work the solar assisted catalytic hydropyrolysis process using microalgae Chlamydomonas reinhardtii as biomass source and hydrotalcite-derived mixed oxides as catalyst (in an ex-situ approach) was successfully investigated as an integrated approach. The effects of reaction time and catalyst percentage on the product distribution and the bio-oil content produced from distinct processes: ex-situ catalytic solar pyrolysis (CSP) and ex-situ catalytic solar hydropyrolysis (CSH) were investigated. The hydrogen used in CSH has been produced by solar aqueous alkaline electrolysis. The results showed that CSH produced higher liquid yields than CSP, reaching 48.83% in its best condition. The content of oxygenated compounds in bio-oil produced by hydropyrolysis was, on average, about 12% lower than that obtained by CSP. However, CSP presented individual tests with less nitrogenated (6.01%) and oxygenated (22.49%) compounds. The hydrocarbon production reached 35.58% for CSP and 37.01% for CSH.

Mild upgrading of biomass pyrolysis vapors via ex-situ catalytic pyrolysis over an iron-montmorillonite catalyst

Pyrolysis vapor upgrading can improve the stability of pyrolysis liquids to facilitate storage, transport, and drop in use as fuels and chemical feedstocks in existing refining infrastructure. This study investigates a low cost iron based catalyst for mild in-situ upgrading of fast pyrolysis vapors to increase the stability of pyrolysis liquid. Iron-doped montmorillonite K10 catalysts were characterized by ICP-OES, BET porosimetry, XRD, XPS, and NH3-TPD. The effect of three upgrading process parameters are evaluated by Box-Behnken experimental design using a fixed catalyst bed. Predictive model equations are developed based on response surface methodology to describe the effect of iron loading, catalyst to biomass ratio, and catalyst bed temperature on yields of pyrolysis liquids, non-condensable gas, and coke on the catalyst. Compared to non-catalytic pyrolysis, pyrolysis vapor upgrading over iron catalyst reduce pyrolysis liquid yields and increase gas yields as pyrolysis vapors are catalytically cracked into lighter molecules. Liquid yield decreases with C:B ratio while gas yields increase. By increasing Fe loading from 0% to 10%, catalyst coking decreases from 11.7% to 3.5% yield. Iron loading of 10% is the least susceptible to coking, but results in greater amounts of polyaromatics in the pyrolysis liquid product. According to GCMS analysis of the pyrolysis liquids, upgraded pyrolysis liquids have lower concentrations of unstable carboxylic acids and aldehydes. In addition, formation of phenols shift towards a greater fraction of alkyl phenols and lower fraction of methoxy phenols leading to a more stable liquid product as a result of upgrading. Overall, iron-doped montmorillonite catalyst is demonstrated to be a viable, low cost catalyst for mild upgrading of fast pyrolysis vapors.

Ex-Situ Catalytic Pyrolysis of Lignin Using Lignin-Carbon Catalyst Combined with HZSM-5 to Improve the Yield of High-Quality Liquid Fuels

Ex-Situ Catalytic Pyrolysis of Lignin Using Lignin-Carbon Catalyst Combined with HZSM-5 to Improve the Yield of High-Quality Liquid Fuels

Seaweed-derived biochar with multiple active sites as a heterogeneous catalyst for converting macroalgae into acid-free biooil containing abundant ester and sugar substances

A series of environmentally friendly and low-cost seaweed-derived biochar catalysts (SDBCs) were prepared. Results indicated that metals modified SDBCs at high temperature displayed highly developed porous structures and more aromatic rings with no less than 6 benzene rings along with defects and heteroatoms. The inorganic minerals were mostly present in the form of NaCl and KCl in the seaweed-derived biochars. Subsequently, the performance of SDBCs was examined through ex-situ catalytic pyrolysis of Enteromorpha clathrate. Results demonstrated that biooils from catalytic pyrolysis exhibited higher (H/C)eff and HHVs in comparison to the control. Interestingly, the carboxylic acids were decreased significantly after using SDBCs. The mechanism is that a significant amount of hydroxyl groups existed in biochar could react with carboxylic group to form FAMEs. Additionally, the metals Cu, Ce and Fe loaded on the BC-800 catalyst had particular effects on the C–C bond and - C = O - units in the pyrolysis volatiles. It was suggested that Cu-BC-800 catalyst was a promising metal modified biochar catalyst for producing acid-free biooils containing abundant esters and sugars.

Upgrading crude bio-oil by in situ and ex situ catalytic pyrolysis through ZSM-5, Ni2Fe3, and Ni2Fe3/ZSM-5: Yield, component, and quantum mechanism

Crude bio-oil was upgraded using in situ and ex situ catalysts (Ni2Fe3, ZSM-5, and Ni2Fe3/ZSM-5) in order to reduce the bio-oil oxygen content. The Ni2Fe3 catalyst powder was specifically designed for this research using materials' simulations, and it showed good activity in improving the bio-oil quality by increasing the heating value. Furthermore, a fixed bed reactor was used for comparing in situ catalytic pyrolysis (ISCP) with ex situ catalytic pyrolysis (ESCP). The results indicated that the Ni2Fe3 catalyst showed greater activity for the ISCP experiments resulting in increased bio-oil yield and improved the bio-oil quality. The bio-oil consisted of higher heating value compounds including a small number of hydrocarbon compounds. However, the results showed that the bio-oil yield with the Ni2Fe3/ZSM-5 catalyst was low for both cases of ISCP and ESCP while the sugar content decreased during the pyrolysis process. Different reaction pathways and mechanisms are proposed for ISCP and ESCP. ESCP reactions transformed 1-hydroxy-2-butanone completely to 2-propanone, 1-hydroxy-, but ISCP converted only 55% of 1-hydroxy-2-butanone to 2-propanone, 1-hydroxy- to the final product. ISCP and ESCP methods showed different reaction pathways for the 1,2-cyclopentanedione compound, and the final product was 2-cyclopenten-1-one and 1,2-cyclopentanedione, 3-methyl-, respectively. These results indicated that the catalysts showed different reactions for ISCP vs ESCP, while the Ni2Fe3 catalyst was effective for ISCP catalytic pyrolysis. Ni2Fe3 showed better activity when compared to ZSM-5 and when supported by ZSM-5 as an ESCP catalyst. These results indicated that the Ni2Fe3 metal catalyst has potential to replace the current catalysts for industrial use to upgrade bio-oil.

Catalytic Pyrolysis of Polyethylene Terephthalate Over Desilicated Beta.

The desilication effect of Beta on the catalytic pyrolysis of polyethylene terephthalate (PET) was investigated in this study. Compared to parent Beta, desilicated Beta revealed the higher aromatics formation efficiency due to its larger pore size allowing the efficient diffusion of PET pyrolysis intermediates to the catalyst pore. Compared to the in-situ catalytic pyrolysis, ex-situ catalytic PET pyrolysis over desilicated Beta produced a larger amount of aromatics. The desilicated catalyst could be re-used without catalyst regeneration due to the small extent of catalyst deactivation.

Effects of steam to enhance the production of light olefins from ex-situ catalytic fast pyrolysis of biomass

This study aims to report on the feasibility of enhancing light olefins production from ex-situ catalytic fast pyrolysis (CFP) of biomass by co-feeding with steam and determine the role of steam. Effects of steam on catalyst and pyrolysis/catalysis reactions in ex-situ CFP were investigated using a two-stage fluidized-bed/fixed-bed reactor. Carbon yield of olefins + monocyclic aromatic hydrocarbons (MAHs) increased by 23.80% after proper steam dealumination of HZSM-5 framework, which suggests that HZSM-5 can be activated at the initial exposure to steam. For activated HZSM-5, olefins carbon yield increased by 35.65% and olefins to MAHs (O/M) ratio boosted from 0.83 to 1.60 as steam concentration in carrier gas increased from 0% to 40%, while the total carbon yield of olefins and MAHs still kept at the same level. Steam enhanced olefins production by: (1) promoting the formation of light compounds in bio-oil, which are the main precursors of hydrocarbons, during pyrolysis; (2) inhibiting aromatization reactions during catalysis. It provides a possibility for the control of O/M ratio of hydrocarbon products and the enhancement of light olefins production from CFP of biomass.

Catalytic conversion of pure glycerol over an un-modified H-ZSM-5 zeolite to bio-based aromatics

The catalytic conversion of pure glycerol to bio-aromatics (bio-BTX) over an un-modified H-ZSM-5 (SiO2/Al2O3 molar ratio of 23) via an ex-situ catalytic pyrolysis approach in a continuous tandem-micro reactor at a scale of 1 g glycerol h−1 was investigated. A BTX peak carbon yield of 28.1 ± 0.2 % was obtained at a pyrolysis temperature of 400 °C, catalytic upgrading temperature of 500 °C, atmospheric pressure and a WHSV of 1 h−1. About 70 % of the bound oxygen in glycerol was converted to water. The latter was mainly formed in the catalytic upgrading unit (70 %), though conversion of glycerol to other oxygenates with water formation was also observed in the pyrolysis unit. Catalyst deactivation occurs at a time scale of hours and is mainly due to coke deposition (12.0 wt.%) on the catalyst surface. An oxidative regeneration procedure to remove coke was applied and 5 cycles of reaction-regeneration were performed successfully, though a drop in activity was observed after each cycle due to irreversible catalyst deactivation. Characterization of the fresh, deactivated and regenerated catalysts by various techniques revealed dealumination of the H-ZSM-5 framework and resulted in a dramatic decrease in Brønsted acidity of the catalyst. Dealumination mainly occurred in the catalytic upgrading reactor and to a by far lesser extent during catalyst regeneration. This information is relevant for a better understanding of the process on a molecular level but also for scale-up studies, e.g. for the design of pilot plants.

Catalytic cracking of Etek lignin with zirconia supported metal-oxides for alkyl and alkoxy phenols recovery

Alkyl and alkoxy phenols are desirable products from the catalytic depolymerisation of lignin. In this work, ex-situ catalytic pyrolysis of Etek lignin in presence of Na, Ce, NiCe, MgCe, Fe and FePd on ZrO2 was studied. The largest combined yield of monomeric phenolics and alkylphenols was produced by Na/ZrO2 catalysts. A parametric study of the most promising Na/ZrO2 then resulted in using a catalyst:lignin ratio of 3:1 at 500 °C as the best option, enhancing at 17.5 wt% the recovery of total phenolics including 6 wt% alkyl phenols, which is equivalent to 27.8 wt% and 9.5 wt% of the starting lignin in Etek lignin waste. The study of the catalyst basicity indicates that the mild basicity of Na/ZrO2 was mostly responsible for the enhanced mono phenols recovery. Due to formation of thermally stable Na2CO3 during pyrolysis, successful Na/ZrO2 regeneration requires temperature of 900 °C or higher.

Effect of H-ZSM-5 and Al-MCM-41 Proportions in Catalyst Mixtures on the Composition of Bio-Oil in Ex-Situ Catalytic Pyrolysis of Lignocellulose Biomass

The present work is an attempt to optimize the proportion of H-ZSM-5 and Al-MCM-41 in the catalyst mixtures for lignocellulose biomass catalytic pyrolysis. The H-ZSM-5 proportions of 50.0, 66.7, 75.0, and 87.5 wt.% were examined for the upgrading of biomass pyrolysis vapors in the fixed bed reactor. The catalyst mixture of 87.5 wt.% H-ZSM-5 and 12.5 wt.% Al-MCM-41 was found most effective in this study, giving a 65.75% deoxygenation degree. An organic-rich bio-oil was obtained with 74.90 wt.% of carbon content, 8 wt.% of hydrogen content, 15 wt.% oxygen content, a 0.39 wt.% water content, and a high heating value of 34.15 MJ/kg. The highest amount of desirable compounds among the studied catalytic experiments, which include hydrocarbons, phenols, furans, and alcohols, was obtained with a value of 95.89%. A significant improvement in the quality of bio-oil with the utilization of H-ZSM-5 and Al-MCM-41 catalyst mixtures was the rise of desirable compounds in bio-oil.

Ex-situ catalytic fast pyrolysis of soapstock for aromatic oil over microwave-driven HZSM-5@SiC ceramic foam

In view of the poor selectivity of aromatic hydrocarbons in bio-oil from biomass pyrolysis and the high pressure drop and rapid coking and deactivation of catalyst in industrial scale, a microwave-driven HZSM-5@SiC ceramic foam has been constructed, and applied to the ex-situ catalytic fast pyrolysis of soapstock to improve the content of aromatic hydrocarbons in bio-oil. The effects of different catalysts and heating modes and mass ratios of HZSM-5@SiC ceramic foam to soapstock on the distribution of pyrolysis products have been investigated. In addition, combined with the comparison of microwave and electric heating, the deactivation characteristics of HZSM-5@SiC ceramic foam have been studied. Finally, the process of preparing aromatic oil by microwave-driven catalytic pyrolysis of soapstock was discussed. Experimental results indicate that compared with HZSM-5, HZSM-5@SiC ceramic foam has a higher yield of bio-oil and higher aromatization activity. Under microwave heating, the relative content of aromatic hydrocarbons increases from 25.18% to 100% when the mass ratio of HZSM-5@SiC ceramic foam to soapstock increases from 0:1 to 1:1. Compared with electric heating catalysis, HZSM-5@SiC ceramic foam has the lowest yield of coke under microwave heating. After five consecutive uses, it still maintains more than 90% catalytic activity and has higher stability, which provides a scientific basis for the pilot scale experiments of soapstock catalytic pyrolysis.

Calcium formate assisted catalytic pyrolysis of pine for enhanced production of monocyclic aromatic hydrocarbons over bimetal-modified HZSM-5

An efficient process was developed to selectively produce monocyclic aromatic hydrocarbons (MAHs) from ex-situ catalytic fast pyrolysis (CFP) of pine assisted with calcium formate (CF) over bimetal-modified HZSM-5. Mo and another metal (Mg, Ga or Zn) were used to modify the HZSM-5, and the as-synthesized bimetal-modified HZSM-5 catalysts were utilized for both pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale CFP tests with CF as a hydrogen donor to selectively obtain MAHs. The results revealed that the presence of CF and Mg-Mo modified HZSM-5 (0.5Mg1Mo/HZ) exhibited excellent capability for MAHs production with tiny generation of polycyclic aromatic hydrocarbons (PAHs). The maximum MAHs yield attained 12.79 wt% at 650 °C from Py-GC/MS with the CF-to-pine (CF-to-PN) ratio of 3 and catalyst-to-pine (CA-to-PN) ratio of 11, and became 9.67 wt% from lab-scale device with CF-to-PN and CA-to-PN ratios of 0.5 and 4, respectively. In addition, compared with HZSM-5, 0.5Mg1Mo/HZ possessed better anti-deactivation ability.

Synthesis of iron nanoparticles-based hydrochar catalyst for ex-situ catalytic microwave-assisted pyrolysis of lignocellulosic biomass to renewable phenols

Selective production of phenols via ex-situ catalytic pyrolysis of lignocellulosic biomass is a promising route in biomass conversion. Therefore, developing a low-cost and effective catalyst for this process has emerged as an important topic. Here, the iron nanoparticles-based carbonaceous catalysts were prepared via combining hydrothermal carbonization and pyrolysis approach and first used in the catalytic microwave-assisted pyrolysis of torrefied corn cob for phenols production. The effects of catalyst types, catalytic temperature, and catalyst to feedstock ratio on the production of phenolic compounds were studied. The total selectivity of phenols can reach 91.07 area% with the total yield of 18706.6 µg/ml bio-oil using the FeHC@ hydrochar catalyst (prepared by hydrothermal carbonization in the Fe(NO3)3 solution and pyrolysis) at the catalytic temperature of 450 °C and catalyst to feedstock ratio of 5:10. After using seven times, partial loss of catalytic activity of FeHC@hydrochar was found. This study also presented unique insights into the deactivation of carbonaceous catalysts, showing that sintering, oxidation of α-Fe and Fe3C phases, active site coverage, and pore blockage were the causes of the reduction of catalytic performance. Regeneration experiments showed that it is impracticable to calcine deactivated catalyst at an inert atmosphere and more advanced techniques needed to be developed to solve this problem. Overall, this study can provide a reference for realistic scale-up production of renewable phenols.

Enhanced BTEX formation via catalytic fast pyrolysis of styrene-butadiene rubber: Comparison of different catalysts

Catalytic degradation of styrene-butadiene rubber (SBR) to produce value-added BTEXs (i.e., benzene, toluene, ethylbenzene, and xylenes) is a promising approach to dispose of solid wastes. In this work, the effects of catalyst contact mode (in-situ or ex-situ), catalyst type, and reaction conditions on desirable BTEXs production were investigated. Experimental results indicated that a limited amount of BTEXs with selectivity of 11.1% was obtained in the non-catalytic run, while a ~6-fold content increase was attained upon employing ultrastable Y (USY) zeolite as a catalyst in the in-situ catalytic trial. The USY catalyzed run also produced more C4 olefin, C5-6 linear alkanes and alkenes, and C9+ aromatic hydrocarbons. A comparison between in-situ and ex-situ catalytic pyrolysis suggesting that the former was more beneficial to the generation of BTEXs as the enhanced factor was 11.5% higher than that of the ex-situ catalytic pyrolysis. Catalyst type played a critical role in the catalytic degradation of SBR, and the BTEXs formation was highly dependent on the acidic property of the employed catalyst. The Y type zeolites with a higher content of acid sites, larger surface area, and moderate pore size, generated more targeted BTEXs than Hβ, HZSM-5, and SAPO-34. The optimized reaction conditions to promote the formation of BETXs in the catalytic degradation of SBR over USY, including heating rate, pyrolysis temperature, and catalyst to feedstock mass ratio, were determined to be at 10 °C/ms, 700 °C, and 3:1, respectively.

Upgrading of bio-oil by ex-situ catalytic pyrolysis and in-line esterification in fluidized bed reactor

Ex-situ catalytic pyrolysis of Quercus mongolica over HZSM-5 and in-line esterification of pyrolysis/catalytic pyrolysis vapors with liquid phase n-butyl alcohol were carried out in a fluidized bed reactor. The ex-situ catalytic pyrolysis over HZSM-5 beads was performed to produce bio-oil containing aromatic hydrocarbons. The temperature of the ex-situ catalytic upgrading reaction was varied from 450 °C to 600 °C, and the maximum aromatic hydrocarbons yield was obtained at 450 °C. The selectivity for aromatic hydrocarbons as a function of catalytic reaction temperature varied depending on aromatic ring number, as the selectivity for mono-aromatic hydrocarbons decreased and that for poly-aromatic hydrocarbons increased with temperature. In-line esterification of the pyrolysis/catalytic pyrolysis vapors with liquid n-butyl alcohol was also carried out, and the GC/MS analysis results showed that the acids, aldehydes and ketones in the bio-oil were converted to esters and acetals.

Online fast pyrolysis of cellulose over titanium dioxide using tandem micro-reactor-GC-MS

In this work, the catalytic effect of titanium dioxide (TiO2) on the online fast pyrolysis of cellulose was investigated using a tandem micro reactor coupled to a gas chromatograph-mass spectrometer (GC-MS) system. This system was used in the following two different modes: in-situ and ex-situ. The results obtained with TiO2 were compared with those of zeolite (HZSM-5) under identical pyrolysis conditions. Levoglucosan was the major product in the non-catalytic pyrolysis of cellulose. As for the catalytic pyrolysis of cellulose at 500 °C with TiO2 (in-situ), the peak of levoglucosan disappeared whereas aromatic hydrocarbons such as benzene, toluene and naphthalene were newly detected. In this case, oxygenated compounds such as furfural, furan, methylfuran were still observed for TiO2 whereas oxygenated compounds (i.e, furan, benzofuran, methylbenzofuran, acetone and 2-butanone) with low yields were observed for in-situ catalytic pyrolysis with HZSM-5. For ex-situ catalytic pyrolysis of cellulose at 500 °C using TiO2, oxygen-containing compounds were hardly formed, while various aromatic hydrocarbons were detected. When the ex-situ pyrolysis of cellulose with HZSM-5 was carried out, the yields of the aromatic hydrocarbons were comparable to those with TiO2.

Resolving challenges in biomass catalytic pyrolysis by co-optimization of process and catalyst: Removal of heavy fraction in pyrolysis vapours and application of novel zeolite catalyst with high thermal conductivity

Ex-situ catalytic pyrolysis of lignocellulosic biomass is an intriguing technology that combines thermal deconstruction of the feedstock with upgrading of the vapour and liquid intermediates. To date, in contrast with the current fossil fuel-based industrial processes, several fundamental challenges still impede its widespread deployment to generate renewable, cost-competitive biofuels and/or value-added chemicals. Catalyst improvements and process development offer a substantial opportunity to advance the technology. In this work, a novel zeolite catalyst SiC@MZSM-5 was successfully synthesized by growing ZSM-5 on SiC nanowires. The improved thermal conductivity was envisioned to minimize adverse effects of the downstream fixed-bed temperature fluctuation resulting from strong exothermic reactions during catalytic upgrading, hence fostering product distribution regulation. Concurrently, the pyrolysis process was managed to remove the heavy fractions from pyrolysis vapours by its internal recycling and forced secondary degradation, alleviating catalyst deactivation risk and thus extending the regeneration interval. The co-optimization of catalyst and process strategy improved the catalyst lifetime, optimized fixed-bed temperature distribution, and preserved the catalytic performance.

Prevention of CaO deactivation using organic calcium precursor during multicyclic catalytic upgrading of bio-oil

The conversion of biomass wastes into upgraded bio-oil has been successfully implemented by catalytic fast pyrolysis (CFP) with CaO catalyst. The bottleneck of CFP technology is catalyst deactivation. Ex-situ catalytic pyrolysis of biomass wastes with multiple recycling of CaO from different calcium precursors were performed in a continuous fixed-bed at 500 °C. The objectives were to intensify the anti-deactivation and regenerative stability of CaO using organometallic precursor, and comprehensively distinguish the effects of calcium precursors on deactivation mechanism in terms of coke yield, coke species, structural and chemical changes et al. The results demonstrated that organic calcium precursor strengthened the recyclability of CaO catalyst during upgrading of bio-oil by showing longer lifetime and better recycling stability. Compared with conventional CaO from Ca(OH)2 (CH-CaO), the stronger deoxygenation and superior porosity of CaO from organic calcium precursors (Org-CaO) facilitated the removal of coke precursors and suppressed pore plugging. The average coke yields of CH-CaO and Org-CaO were respectively 5.1 and 2.2 g/m2. Moreover, CH-CaO promoted the aromatization of coke precursors, leading to coke existing in form of hard diamond-like structure. But coke deposited on Org-CaO exhibited softer layered graphite structure and contained more aliphatic matters. After 10 reaction/regeneration cycles, Org-CaO still kept 50% deoxygenation activity whereas CH-CaO showed almost complete deactivation. Organic calcium precursors delayed irreversible deactivation of CaO, since these precursors physically prevented the sintering and agglomeration of CaO, and chemically alleviated the loss of both the strength and density of basic sites on CaO.

Molecular shape selectivity of HZSM-5 in catalytic conversion of biomass pyrolysis vapors: The effective pore size

This article is intended to deepen the understanding of molecular shape selectivity of HZSM-5 in catalytic conversion of biomass pyrolysis vapors through the study of catalyst effective pore size. Ex-situ catalytic fast pyrolysis (CFP) of biomass over HZSM-5 with varied catalyst loadings were carried out using a continuous feeding two-stage fluidized-bed/fixed-bed combination reactor. Results showed that in addition to the shape selective reactions inside catalyst channels, cracking and aggregating reactions occur at the external surface of HZSM-5. The catalytic activity of HZSM-5 external surface for some heavy compounds was observed to be relatively low. On the basis of the molecular dimension information provided by quantum chemical calculations, it was found that HZSM-5 has an effective pore size which is significantly larger than its static pore size at CFP temperature. Catalytic alkylation of naphthalene with methanol over HZSM-5, HZSM-5@silicalite-1, HSAPO-34, HM, Hβ, HUSY and HMCM-41 were further compared to determine the effective pore size of HZSM-5. It is proposed that the effective pore size of HZSM-5 at CFP temperature is between the critical molecular diameters of 2,3- and 1,6-dimethylnaphthalene (between 7.520 and 7.961 Å).

Renewable phenol production from lignin with acid pretreatment and ex-situ catalytic pyrolysis

A novel pathway to clean production of phenol-rich bio-oil and syngas by catalytic pyrolysis of pretreated lignin was investigated for the first time. The process integrated pretreatment and catalysis. The results revealed that the optimal condition for phenol selectivity (95.5%) from unpretreated lignin pyrolysis was achieved at a pyrolytic temperature of 550 °C with catalyst/lignin ratio of 0.7. Lignin pretreatment boosted the volatile production as well as syngas formation. A significant increase in the phenol concentration (from 0.6 to 7.0 mg/mL) for pretreated lignin was achieved at pretreated temperature of 50 °C for 60 min. During the deactivation test, the catalyst exhibited a benign catalytic performance for phenol selectivity after using four times. Further, the “phenol pool” and free radical were proposed to uncover the mechanism of phenol generation from catalytic conversion of pretreated lignin. These findings pave a new and clean route to produce high-purity phenol, which could ultimately advance the utilization of lignin through facile fix-bed catalytic pyrolysis technology.