Yield Of Hydrocarbons Research Articles

Pollutant emissions during the pyrolysis and combustion of starch/poly(vinyl alcohol) biodegradable films

The massive use of petroleum-based polymers and their improper waste treatment has brought on significant global environmental problems due to their non-biodegradable nature. Starch/poly(vinyl alcohol) (PVA) bioplastics are suitable substitutes for conventional polymers, such as polyethylene, due to their full biodegradability and excellent mechanical properties. Knowledge of the pollutant emissions during pyrolysis and combustion of starch/PVA films is important because they can arrive at landfills mixed with conventional polymers and be thermally degraded in uncontrolled fires. On the other hand, controlled thermal treatments could result in thermal valorization of the waste. Pyrolysis and combustion experiments were carried out at 650, 750, 850 and 950 °C in a laboratory furnace. The analysis of carbon oxides, light hydrocarbons, and semivolatile compounds, including polycyclic aromatic hydrocarbons (PAHs), is shown. Experiments showed lower pollutant emissions than those found with conventional polymers, such as polyethylene and polyester, in the same equipment. Nevertheless, the pyrolysis run at 950 °C showed the highest light hydrocarbon yield (123013 mg kg−1), but this is considerably lower than the values found for polyethylene. The main semivolatile compounds (not PAHs) emitted, with maximum yields ranging from 1351 to 4694 mg kg−1, were benzaldehyde, phenol, indene, and acetophenone. Specifically, the total semivolatile compounds emitted after pyrolysis and combustion of starch/PVA samples represent only 38 and 50%, respectively, of those emitted with polyethylene. Further, the main PAHs were naphthalene, acenaphthylene, and phenanthrene with maximum values of 4694, 2704 and 1496 mg kg−1, respectively. The PAH yield was considerably higher in experiments with low oxygen content.

КАТАЛИТИЧЕСКАЯ ТРАНСФОРМАЦИЯ МЕТАНОЛА / ДИМЕТИЛОВОГО ЭФИРА В УГЛЕВОДОРОДЫ С ИСПОЛЬЗОВАНИЕМ ZN-МОДИФИЦИРОВАННОГО ЦЕОЛИТА H-ZSM-5

The universally depleting reserves of traditional hydrocarbons require the development of a technology for producing synthetic hydrocarbons from renewable sources or human waste. Currently, among the possible methods for producing synthetic hydrocarbons, it is necessary to note the Fischer–Tropsch method and the method of methanol / dimethyl ether catalytic transformation. Moreover, the production of synthetic hydrocarbons from synthesis gas — the Fischer–Tropsch method, is suitable for the production of linear hydrocarbons. The hydrocarbons synthesis using methanol / dimethyl ether is suitable for the production of olefins, branched paraffins, aromatic and polyaromatic hydrocarbons. Depending on the synthesis conditions, it is possible to preferentially obtain a certain type of hydrocarbon, which significantly increases the value of this process. In this article modification of zeolite type H-ZSM-5 with zinc is studied in order to increase the yield of liquid hydrocarbons. Zeolite in acid form was treated with zinс acetate solutions of different concentrations, followed by calcination of the samples. The efficiency of the catalysts was studied in a flow tube reactor set-up, and the surface acidity of the samples was also determined. An increase in the zinc content in zeolite contributed to a decrease in the acidity of the samples and modification of their active centers. However, at high zinc content, a separate oxide phase forms, which contributes to a slight increase in acidity. Modification of zeolite with zinc leads to a decrease in the rate of transformation of dimethyl ether and the rate of liquid hydrocarbons formation. However, a general decrease in acidity and modification of zeolite with zinc contributes to a significant decrease in the amount of heavy aromatic compounds formed, with an increase in the amount of gaseous and liquid hydrocarbons being formed.

Jet Fuel Range Hydrocarbon Production from Propanal: Mechanistic Insights into Active Site Requirement of a Dual-Bed Catalyst

Utilization of sustainable biomass to produce jet fuel range hydrocarbons is imperatively needed to mitigate CO2 emissions and to liberate the over-reliance on fossil resources. Using propanal as the feedstock, an excellent jet fuel range hydrocarbon yield (81.7%), high conversion (ca. 100%), and purity (85%) were achieved over a novel dual-bed Cu/SiO2–TiO2||Ni/ZSM-5 catalyst at low temperature and pressure in only one reactor. The intrinsic active site requirement was further investigated by multitechniques including density functional theory calculation, quantitative CO2/NH3-temperature-programmed desorption/diffuse reflectance infrared Fourier-transform spectroscopy, high-resolution transmission electron microscopy, and thermogravimetric analysis–mass spectrometry. Results showed that for the upstream bed catalyst (Cu/SiO2–TiO2), the Ti–O site pair and Ti Lewis acid site were crucial for enolate formation, carbon-chain growth, and ring closure reactions, which can be altered by the calcination temperature. The synergy between the site strength and number led to a volcanic relationship between acidity/basicity and the intermediate yield. In addition, the downstream bed Ni/HZSM-5 catalyst promoted the hydrodeoxygenation reaction toward hydrocarbon formation.

Production of bio-oil with low oxygen and nitrogen contents by combined hydrothermal pretreatment and pyrolysis of sewage sludge

In this study, sewage sludge (SS) is first hydrothermally pretreated at 160–250 °C, and subsequently pyrolyzed at 550 °C to produce bio-oil. The effects of the hydrothermal pretreatment (HTP) temperature on the chemical composition, fuel properties, and energy balance of the process are investigated to assess its feasibility. The results show that the characteristics of SS are improved during HTP, including better thermal stability, decreased N content, and enhanced aromaticity, which could influence subsequent pyrolysis. After HTP, the composition of bio-oil shows clear variation. The contents of undesirable O-containing and N-containing compounds, especially acids and amides, are significantly decreased, while the yields of aliphatic hydrocarbons and aromatics increase by 9.53% and 23.18%，respectively. The H/C ratio and higher heating value (HHV) of bio-oil in Sample 190–550 increase to 0.136 and 36.382 MJ/kg, respectively, which are similar to those of biodiesel. The suggested optimal HTP temperature is 190 °C for the HHV and energy recovery rate (44.23%). Meanwhile, the formation pathway of bio-oil with low N and O contents is explored.

Mechanistic and microkinetic study of non-oxidative methane coupling on a single-atom iron catalyst

Non-oxidative methane coupling has promising economic potential, but the catalytic and radical reactions become complicated at high temperatures. Here, we investigate the mechanism of non-oxidative methane coupling on an iron single-atom catalyst using density functional theory, and evaluate the catalytic performance under various reaction conditions using microkinetic modelling and experiments. Under typical reaction conditions (1300 K and 1 bar), C–C coupling and subsequent dehydrogenation to produce ethylene shows comparable energetics between the gas-phase and catalytic pathways. However, the microkinetic analysis reveals that the iron single-atom catalyst converted methane to mainly CH3 and H2 at reaction temperatures above 1300 K, and acetylene production is dominant over ethylene production. The sensitivity analysis suggests that increasing the C2 hydrocarbon yield by optimising the reaction conditions is limited. The experimental results obtained at 1293 K are consistent with the theoretical estimation that acetylene is the main C2 product over the iron single-atom catalyst.

Comparative study on pyrolysis of bamboo in microwave pyrolysis-reforming reaction by binary compound impregnation and chemical liquid deposition modified HZSM-5

The deactivation of catalyst is a significant reason for its limited application during the catalytic fast pyrolysis (CFP) process. To reduce the coke formation, binary compound impregnation (BCI) and chemical liquid deposition (CLD) were used to modify HZSM-5 catalysts. At the same time, the self-designed microwave reactor separated the pyrolysis of bamboo and catalytic upgrading of primary vapor, which made the catalytic effect more thorough. Experimental results indicated that CLD used TiO2 deposition to cover external acid sites, while BCI by phosphorus-nickel could cover and partly destroy superficial acid sites through two different ways. Within the scope of the loaded amount studied, the yield of aromatic hydrocarbons in the oil phase increased at first and then decreased, while the coke formation reduced continuously. BTX (benzene, toluene and xylene), the most valuable product in bio-oil, drastically increased by 39.1% and 22.6% respectively over the CLD and BCI modified catalysts. Considering the catalytic performance as well as cost, CLD over HZSM-5 has more advantages in the CFP process to upgrade bio-oil.

Enhancing the aromatic hydrocarbon yield from the catalytic copyrolysis of xylan and LDPE with a dual-catalytic-stage combined CaO/HZSM-5 catalyst

The high concentration of oxygenated compounds in pyrolytic products prohibits the conversion of hemicellulose to important biofuels and chemicals via fast pyrolysis. Herein CaO and HZSM-5 was developed to convert xylan and LDPE to valuable hydrocarbons by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and elucidate the reaction mechanism were also investigated in detail. The results indicated that xylan/LDPE copyrolysis was more complicated than pyrolysis of the individual components. LDPE hindered the thermal decomposition and aromatic hydrocarbon formation from xylan at temperatures under 350 °C and had a synergistic effect at high temperatures. 50% LDPE was proven to be more beneficial than other percentages for the formation of monocyclic aromatic hydrocarbons. Simultaneously, the addition of CaO/HZSM-5 significantly reduced the reaction Ea and increased the reaction rate. CaO can effectively improve the deoxygenation and aromatization reaction, enhancing the yield and selectivity of aromatics to a certain extent. The maximum yield of hydrocarbons (96.01%), mono-aromatic hydrocarbons (88.53%) and SBTXE (85.79%) were obtained at a CaO/HZSM-5 ratio of 1:2, a pyrolysis temperature of 450 °C, a catalytic temperature of 550 °C, a catalyst dose of 1:2 and a xylan-to-LDPE ratio of 1:1 via an ex situ process. The system was dominated by toluene, xylene and alkyl benzene. Diels-Alder reactions of furans and hydrocarbon pool mechanism of nonfuranic compounds improved aromatic formation. This study provides a fundamental for recovering energy and chemicals from pyrolysis of hemicellulose.

Effect of metal type on basic soap pyrolysis produce bio-gasoline

The basic metal soap from oleic acid submitted to pyrolysis to produce gasoline-like hydrocarbon fuels (biogasoline). The pyrolysis was carried out in a semi-batch reactor at 450°C and a feeding rate of 5 g/15 min. The influences of various metal (Ca, Mg, Zn) hydroxides, which are used to made basic soap, have been examined. The bio hydrocarbon of basic metal soap was characterized by GC-FID and FT-IR, showing the formation of paraffin, iso-paraffin, olefin, ketone, and aromatics. The liquid fraction derived from the pyrolysis of basic metal soap was dominated by gasoline (C7-C11) fraction hydrocarbon. The maximum yield of light C7-C11 hydrocarbon was 82.3 %-mol fraction of basic Ca soap and the highest yield of biohydrocarbon reached 34.77 wt.% from pyrolysis of basic Mg soap.

Selective generation of aromatic hydrocarbons from hydrotreating-cracking of bio-oil light fraction with MOx modified HZSM-5 (M = Ga, Mo and Zn)

The upgrading of highly unsaturated bio-oil by zeolite cracking suffers from severe catalyst deactivation due to the carbonaceous deposition. Therefore, the dual-stage hydrotreating-cracking process is developed for more stable operation. In this work, to further promote the generation of aromatic hydrocarbon in a hydrotreating-cracking process cofeeding bio-oil light fraction and methanol, the cracking catalyst HZSM-5 was modified by MOx (M = Ga, Mo and Zn). Compared with the blank HZSM-5, the promotion of aromatic hydrocarbon production by MoO3/HZSM-5 was mainly owing to the enhanced selective conversion of intermediate light alkenes to aromatics, while those by Ga2O3/HZSM-5 and ZnO/HZSM-5 were attributed to both the re-activation of hydrotreating-derived CH4 and the intensified selective aromatization of alkenes. Meanwhile, raising cracking temperature decreased the yield of aromatic hydrocarbon but favored the production of gases. Ga2O3/HZSM-5 was the most effective catalyst for aromatic hydrocarbon production and 400 °C was a suitable cracking temperature, under which the upgrading of a bio-oil aqueous fraction achieved the oil phase yield of above 22% with the aromatic hydrocarbon content of above 93%.

Potentiality of combined catalyst for high quality bio-oil production from catalytic pyrolysis of pinewood using an analytical Py-GC/MS and fixed bed reactor

The aim of this study was to investigate the potential of combined catalyst (ZSM-5 and CaO) for high quality bio-oil production from the catalytic pyrolysis of pinewood sawdust that was performed in Py-GC/MS and fixed bed reactor at 500 °C. In Py-GC/MS, the maximum yield of aromatic hydrocarbon was 36 wt% at biomass to combined catalyst ratio of 1:4 where the mass ratio of ZSM-5 to CaO in the combined catalyst was 4:1. An increasing trend of phenolic compounds was observed with an increasing amount of CaO, whereas the highest yield of phenolic compounds (31 wt%) was recorded at biomass to combined catalyst ratio of 1:4 (ZSM-5: CaO - 4:1). Large molecule compounds could be found to crack into small molecules over CaO and then undergo further reactions over zeolites. The water content, higher heating value, and acidity of bio-oil from the fixed bed reactor were 21%, 24.27 MJkg−1, and 4.1, respectively, which indicates that the quality of obtained bio-oil meets the liquid biofuel standard ASTM D7544-12 for grade G biofuel. This research will provide a significant reference to produce a high-quality bio-oil from the catalytic pyrolysis of woody biomass over the combined catalyst at different mass ratios of biomass to catalyst.

Catalytic Pyrolysis of Guaiacol over Ni/La–Modified Hierarchical HZSM‐5

AbstractCatalytic pyrolysis of guaiacol as a model compound of lignin was conducted to explore the lignin pyrolysis mechanism in this study. The effects of catalyst and temperature on product distribution were studied. Five catalysts were tested including HZSM‐5, hierarchical HZSM‐5, metal‐modified hierarchical HZSM‐5 catalysts. And the Ni/La bimetallic hierarchical HZSM‐5 (NiLa/HZ‐SH) contributes to the achievement of high conversion and selectivity in catalytic pyrolysis of guaiacol. we obtained the yields of monocyclic aromatic hydrocarbons over NiLa/HZ‐SH (550°C): Phenol (23.01%), Benzofuran (6.68%), Salicylaldehyde (1.54%), 2‐Methylphenol (31.48%), 4‐Methylphenol (6.54%), 2‐Ethylphenol (14.89%), 4‐Vinylphenol (1.45%) and Catechol (8.67%), and the maximal yields of these monocyclic aromatic hydrocarbons is 94.26%. Moreover, the yield of polycyclic aromatic hydrocarbons (PAH) as the non‐target product reached a minimum of 1.46% over NiLa/HZ‐SH, while it was 16.88% without catalyst. In addition, catalyst stability was investigated, the reason that led to the decrease of target products could be the acidity and surface area of catalysts decreased as the coke blocked the pore channels, spent catalyst can be successfully regenerated through calcination treatment. Finally, based on the experiment results in this work and other published studies, a guaiacol pyrolysis mechanism was summarized and proposed aiming to understand the lignin pyrolysis process.

PVC-Based Copper Electric Wires under Various Fire Conditions: Toxicity of Fire Effluents.

Ventilation-controlled fires tend to be the worst for toxicity, because they produce large amounts of fire effluent containing high yields of toxic products. In order to examine the dependence of the amount of chosen few main combustion gases under ventilation-controlled conditions, a PVC-insulated copper electric wire with unknown composition (PVC filled with chalk) was studied by mean of a steady state tube furnace. For the tested wire, lower values of CO2 yields at different ventilation conditions were obtained than for the reference pure polymer unplasticized PVC and additionally tested pure LDPE, the yields were higher three times in the case of PVC and two times in the case of LDPE than those received for wire at the same ventilation conditions, which pointed out decreasing contribution of hyperventilation effect to human during cable fire. In contrast, higher values of toxic CO yields, four times higher, were obtained for the PVC-insulated electric wire rather than for the pure polymers. The maximum value of CO yield (0.57 g/g) was determined in the case of 5 L/min of primary airflow and decreased with increasing ventilation. The measured yields of hydrocarbons were similar to the reference values except for the equivalence ratio ϕ = 0.27, where hydrocarbon yield was equal to 0.45 g/g. The HCl yield of fire effluents from the PVC-insulated wire was shown to be independent of ventilation conditions. The corrosive reaction between copper and the HCl species and the flame-retardant mechanisms of the additives, caused the lower values of HCl in the fire effluent of the PVC-insulated copper wire than for pure polymer.

Behavior, kinetic and product characteristics of the pyrolysis of oil shale catalyzed by cobalt-montmorillonite catalyst

In this work, the effects of the coupling between montmorillonite and CoCl2·6H2O on pyrolysis behavior, products distribution and characteristics of liquid fuel were investigated by the combination of pyrolysis experiment and kinetic analysis. The mass fraction of the MMT in oil shale was 3–9%, and the mass fraction of CoCl2·6H2O was 10–25%. The results showed that the coupling effect promoted the formation of shale oil. The maximum yield of shale oil (17.75 wt%) was obtained at 20CoCl2·6H2O5MMT. Catalytic pyrolysis behavior and kinetic analysis indicated that the presence of CoCl2·6H2O and montmorillonite led to the prominent advance of kerogen decomposition temperature and the decrease of apparent activation energy. Significantly, the addition of the 20CoCl2·6H2O5MMT led that the average apparent activation energy was decreased by about 122.42 kJ/mol compared to the catalyst-free pyrolysis. The strong cracking ability produced by their coupling effect was considered to be the main reason. Montmorillonite and CoCl2·6H2O enhanced the decarboxylation and free-radical reaction, resulting in a decrease of acids yield and an increase of aliphatic hydrocarbons yield. The relative content of aliphatic hydrocarbons increased from 41.55% to 51.27%. These results demonstrated that the combined use of montmorillonite and CoCl2·6H2O was beneficial to the generation of saturated hydrocarbon production.

Upgrading of cyclohexanone to hydrocarbons by hydrodeoxygenation over nickel–molybdenum catalysts

Cyclohexanone is largely generated in the direct or indirect conversion of lignin-derived bio-oils. Hence, the upgrading of cyclohexanone, i.e. deoxygenation in the presence of hydrogen is of great interest. In this regard, two nickel-molybdenum catalysts on alumina support were investigated in the temperatures up to 400 °C and pressures up to 15 bar. High activity, selectivity, and yield were achieved by utilizing these catalysts at the studied condition. The main products of the upgrading of cyclohexanone were C6, C7, and C12 cyclic, aromatic, and bicyclic including cyclohexane, cyclohexene, benzene, and cyclohexylbenzene. The results of the present study imply that these catalysts are beneficial in producing hydrocarbon-rich products from cyclohexanone and lignin-derived bio-oils. Based on the achievements of the present study, the nickel-molybdenum catalyst composed of 1.14 wt% nickel and 14.27 wt% molybdenum showed about 87%, 100%, and 116% conversion of cyclohexanone, total hydrocarbon selectivity, and total hydrocarbon yield, respectively. The optimum condition for obtaining such results was at 400 °C and 8 bar.

Enhanced bioaromatics synthesis via catalytic co-pyrolysis of cellulose and spent coffee ground over microporous HZSM-5 and HY

Catalytic co-pyrolysis (CCP) of spent coffee ground (SCG) and cellulose over HZSM-5 and HY was characterized thermogravimetrically, and a catalytic pyrolysis of two samples was conducted using a tandem micro reactor that directly connected with gas chromatography-mass spectrometry. To access the more fundamental investigations on CCP, the effects of the zeolite pore structure, reaction temperature, in-situ/ex-situ reaction mode, catalyst to feedstock ratio, and the SCG and cellulose mixing ratio were experimentally evaluated. The temperature showing the highest thermal degradation rate of cellulose with SCG slightly delayed due to the interactions during the thermolysis of two samples. HZSM-5 in reference to HY produced more aromatic hydrocarbons from CCP. With respect to the reaction temperature, the formation of aromatic hydrocarbons increased with the pyrolytic temperature. Moreover, the in-situ/ex-situ reaction mode, catalyst/feedstock, and cellulose/SCG ratio were optimized to improve the aromatic hydrocarbon yield.

A study on potential recovery of energy and value-added chemicals from in-situ pyrolysis of Bambusa balcooa over basic metal oxides

NiO and CaO catalysts with different weight percentages were used as catalysts in pyrolysis to investigate the feasibility of producing biofuels from Bambusa balcooa. Non-catalytic bio-oil was dominated by aromatic (23.74 %), acids (18.07 %), and alcohols (20.02 %) while optimized catalysts NiO and CaO increased the rate of ketonization in pyrolysis of Bambusa balcooa and decreased the mass yield of acids to 6.31 % and 9.06 % respectively. The quality of bio-oil obtained from catalytic tests was compared to the non-catalytic tests in terms of its product distribution, gasoline range hydrocarbon, viscosity, pH, flash point and fire point. It was observed that 0.5 wt.% NiO and 5 wt.% CaO contained a high yield of gasoline range hydrocarbon reaching 66.75 % and 73.47 %, respectively. In addition to the chemical composition, lower viscosity of the pyrolytic oil shows 0.5 % NiO as a better catalyst in pyrolysis systems to produce enhanced quality bio-oil.

Aromatic hydrocarbons production and synergistic effect of plastics and biomass via one-pot catalytic co-hydropyrolysis on HZSM-5

The catalytic co-hydropyrolysis of pine sawdust (PW) and high density polyethylene (HDPE) to selectively produce aromatic hydrocarbons was studied by optimizing reaction parameters (feedstock composition, reaction temperature, residue time, initial hydrogen pressure and catalyst to reactant ratio). The composition of feedstocks, reaction temperature and the ratio of catalyst to reactant all had significant effects on the content of aromatic hydrocarbons, and the appropriate reaction parameters were selected to maximize the yield of aromatic hydrocarbons. The maximum aromatic hydrocarbons yield (18.3 %) and the highest selectively (67.8 %) were obtained when the ratio of plastic to reactant was 0.6, 400 °C, 1.5 MPa for 1 h and the catalyst to reactant ratio was 0.2. Compared with hydropyrolysis of biomass, the addition of plastics reduced the yield of solid residue and the oxygen content in bio-oil. Characteristic analysis of bio-oil showed that that monocyclic aromatic hydrocarbons accounted for the majority of aromatic hydrocarbons in blends, with benzene, toluene, xylene (BTX) having the highest selectivity (51.6–70.6 %), and oxygenates were almost absent in bio-oil. Meanwhile, the possible reaction pathways in the co-hydropyrolysis of biomass and plastic for aromatic hydrocarbons were discussed extensively.

The utilization of synthesis gas for the deoxygenation of cyclohexanone over alumina‐supported catalysts: Screening catalysts

AbstractEnvironmental regulations motivate the industries to replace conventional fuels and chemicals by those produced from biomass. In this regard, hydrodeoxygenation of lignin compounds is of a great deal of attention. Synthesis gas could be utilized instead of pure hydrogen for the cleavage of oxygen‐containing chemical bonds through hydrodeoxygenation. Following this, the utilization of synthesis gas is investigated in the present contribution. A wide range of commercial alumina‐supported catalysts is investigated. The experimental results of cyclohexanone hydrodeoxygenation in the presence of pure hydrogen and synthesis gas at 573 K and 20 bar of total pressure are presented and discussed. The whole investigated catalysts show good activity toward the hydrodeoxygenation of cyclohexanone. Methylatedbenzene derivatives are produced from cyclohexanone hydrodeoxygenation for the first time. The catalysts composed of platinum showed the best performance. By utilizing a chlorinated platinum catalyst, 89.6% cyclohexanone conversion, 100% total hydrocarbon selectivity, and 44.6% total hydrocarbon yield are obtained. In the case of syngas‐assisted hydrodeoxygenation, 80.1% cyclohexanone conversion, 100% total hydrocarbon selectivity, and 29.6% total hydrocarbon yield are obtained by utilizing the same catalyst. The presence of methylated aromatics proves the accomplishment of methanation or direct aromatization reactions in the presence of carbon oxides and hydrogen.

Review of catalyst materials in achieving the liquid hydrocarbon fuels from municipal mixed plastic waste (MMPW)

Present study aims to highlight the recent developments and challenges associated with catalytic pyrolysis technology for converting municipal mixed plastic waste (MMPW) to valuable hydrocarbon fuels. The study identifies gaps between conventional-thermal and catalytic pyrolysis technologies. Catalyst plays major role in pyrolysis reactions that would reflect yield of liquid product. Scale-up of pyrolysis process with MMPW is viable if catalyst used in the current existing pyrolysis process. A wide scientific literature indicates that catalyst used in pyrolysis has seen changing faces from commercial catalyst to designing of catalyst to synthesis of cheaper catalyst. However, tailored catalyst found to be very effective in processing the waste to fuels. In addition, discussion extended on the yields of liquid hydrocarbon fuel variation with the use of different catalysts in thermal pyrolysis.

Promoting Light Hydrocarbons Yield by Catalytic Hydrodechlorination of Residual Chloromethanes Using Palladium Supported on Zeolite Catalysts

Gas catalytic hydrodechlorination (HDC) of trichloromethane (TCM) and dichloromethane (DCM) was analyzed using Pd (1 wt.%) on different zeolites as catalysts. The aim of this study was to know the surface properties of the catalysts and reaction conditions that promote the yield to light hydrocarbons in this reaction. Five different zeolite supports were used from three commercial zeolites (KL, L-type; NaY, Faujasite; H-MOR, Mordenite). KL and NaY were submitted to ionic exchange treatments in order to increase their acidity and analyze the effect of the acidity in the activity and selectivity of the HDC reaction. Exchanged zeolites (HL and HY) showed the highest Pd dispersion due to their higher surface acidity. The best TCM/DCM conversion and selectivity to light hydrocarbons was obtained using the two non-exchanged zeolite-catalysts, KL and NaY. Low surface acidity seems to be the key aspect to promote the formation of light hydrocarbons. The formation of these products is favored at high reaction temperatures and low H2: chloromethane ratios. KL showed the highest selectivity to olefins (60%), although with a lower dechlorination degree. Non-exchanged NaY catalyst showed high selectivity to paraffins (70% and 95% for the HDC of DCM and TCM, respectively).