Liquid-phase Products Research Articles

Electrochemical Decomposition of Primary Alcohol Groups in Deep Eutectic Solvents

This work investigates the electrochemical decomposition of an ethylene glycol/sodium chloride electrolyte and a deep eutectic solvent (DES) comprised of ethylene glycol/choline chloride (ethaline). Understanding these reactions can help to better understand the safety risks of overcharge when these electrolytes are used in a battery and to guide the design of DES electrolytes for improved electrochemical stability. Analysis of the decomposition products was performed using a combination of coulometry, gas chromatography, mass spectrometry, and Fourier transform infrared spectroscopy. It was found that even at relatively low (mM) concentrations of water, a stoichiometric rate of hydrogen is produced under cathodic conditions in both the ethaline and EG/NaCl electrolytes. This suggest an electrochemical hydrolysis cathodic decomposition reaction that produces both hydrogen gas and hydroxyl ions. This reaction was verified in both electrolytes by also identifying the liquid phase products. Only liquid phase products were observed under anodic conditions. A suspected alcohol oxidation to aldehyde anodic decomposition reaction was confirmed through a similar analysis of products. A tertiary alcohol only DES was investigated to eliminate these decomposition paths and was found to have increased stability window compared to the primary alcohol.

Harnessing Shape Complementarity for Upgraded Cyclohexane Purification through Adaptive Bottlenecked Pores in an Imidazole-Containing MOF.

Shape complementarity is a biological craft for precisely binding substrates at protein-protein interfaces. An analogy to such a function can be drawn conceptually for crystalline porous solids; yet the manifested entities are rare in reticular chemistry. The bottleneck-shaped pores carved out of a metal-organic framework, Zn(MIBA)2 (aka. MAF-stu-13), can perfectly accommodate benzene molecules. Remarkably, its framework adapts to the optimal guest binding-the enhanced host-guest interactions in the neck in turn minimize the guest-guest repulsion in the pore to the extent it turns into attraction-as demonstrated by the combined X-ray structural and DFT computational studies. This adaptive material can be used for liquid-phase production of ultrahigh-purity (≥99 %) cyclohexane, achieving a balance between uptake capacity and separation selectivity and surpassing the performances of other porous and nonporous crystals reported recently (e.g. product purity 99.4 % vs. 97.5 % to date).

Experimental investigation and mathematical modelling of batch and semi-continuous anaerobic digestion of cellulose at high concentrations and long residence times

In the context of the anaerobic digestion of slowly biodegradable substrates for energy and chemicals production, this study investigated the anaerobic digestion of cellulose without any chemical pre-treatments using open (undefined) mixed microbial cultures. The anaerobic conversion of cellulose was investigated in extended-length (run length in the range 518–734 days) batch and semi-continuous runs (residence time 20–80 days), at high cellulose concentration (20–40 g L−1), at temperatures of 25 and 35 °C. The maximum cellulose removal was 77% in batch (after 412 days) and 60% (at 80 days residence time) in semi-continuous experiments. In semi-continuous experiments, cellulose removal increased as the residence time increased however the cellulose removal rate showed a maximum (0.17 g L−1 day−1) at residence time 40–60 days. Both cellulose removal and removal rate decreased when cellulose concentration in the feed was increased from 20 to 40 g L−1. Liquid-phase products (ethanol and short chain organic acids) were only observed under transient conditions but not at the steady state of semi-continuous runs. Most of the observed results were well described by a mathematical model which included cellulose hydrolysis and growth on the produced glucose. The model provided insight into the physical phenomena behind the observed results.

Co-pyrolysis of waste polyvinyl chloride and oil-based drilling cuttings: Pyrolysis process and product characteristics analysis

Oil-based drill cuttings (OBDC) and waste polyvinyl chloride (waste PVC) both are solid wastes. The pyrolysis/co-pyrolysis characterizations of OBDC, waste PVC and OBDC/waste PVC at varying heating rates were investigated using thermogravimetric analysis (TG/TGA). Coats-Redfern and Kissinger integration methods were employed to fit the TG curve. The optimal fitting effect was obtained with reaction order at 2 and Kissinger integration method was better than Coats-Redfern integration method for co-pyrolysis of OBDC/waste PVC. The practical co-pyrolysis condition was optimized using batch experiment and the optimal condition was as following: final temperature for 600 °C, holding time for 60 min, heating rate at 10 °C/min and ratio of PVC as 10% PO. The gas, solid and liquid phase products of pyrolysis/co-pyrolysis were characterized and analyzed using thermogravimetry-mass spectrometry (TG-MS), gas chromatography-mass spectrometry (GC-MS) and X-ray diffraction (XRD). The gas product of pyrolysis/co-pyrolysis indicated the inhibitory effect on HCl emission due to the positive synergic effect of OBDC and PVC. High pyrolysis temperature was beneficial to increase the content of hydrocarbons, which enhanced the quality of oil recovery. This study indicated that the co-pyrolysis of OBDC and waste PVC is a promising method for waste disposal and oil recovery.

Microwave demulsification characteristics and product analysis of oily sludge

ABSTRACT Oily sludge is a kind of industrial hazardous waste that contains a lot of harmful substances. It has high water content and oil content. Demulsification is the key link for its resource utilization. Based on the unique heating characteristics of microwave heating, this paper uses microwave heating method to demulsify oily sludge in refineries. The effects of microwave power, temperature, stirring time, and additives on the demulsification of oily sludge are studied. The composition of each layer of the oil phase is analyzed to explore the possibility of oil reuse. The orthogonal test results show that the order of the influence of various factors on the dehydration rate of sludge is: temperature>power>stirring time; microwave power 700 W, temperature 55°C, and stirring time 10 min, the dehydration rate of sludge reaches the maximum value of 69.3%; adding sludge pyrolysis residue can significantly improve the efficiency of sludge dehydration; based on the results of microwave primary demulsification experiments, a deep demulsification and dehydration method for sludge is proposed. Based on the carbon number method, the relative contents of the liquid phase product were corrected, and it was found that the three layers of liquid phase product composition after demulsification and centrifugation were significantly different. The upper layer was mainly composed of gasoline (69.54%), and the middle layer was mainly composed of diesel (89.55%), the lower layer was mainly heavy oil components (75.87%).

Insights into the desulfurization mechanism of low-grade limestone as absorbent induced by particle size

Utilization of low-grade limestone (LGL) in wet flue gas desulfurization (WFGD) has been considered as a promising technology due to the decrease in limestone grade caused by the overexploitation of natural high-grade limestone. In this study, the dissolution kinetics and desulfurization mechanism of LGL absorbents induced by particle size were investigated. Shrinking core kinetic model (SCKM) was employed to study the complete dissolution kinetic analysis. The results showed that the dissolution of LGL was controlled by the diffusion through an inert solid film composed of the residue CaMg(CO3)2, which was insensitive to the variation of particle size. Finer LGL particles having higher dissolution rate and stronger Ca2+ ions releasing ability exhibited a better desulfurization performance. The spent absorbents and reacted liquid phase products were analyzed by X-Ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and inductively coupled plasma luminescence spectrometry (ICP-OES). These characterizations illustrated that it was primarily CaCO3 in LGL which had a much higher desulfurization capacity that removed SO2 in the beginning. The solid film formed during the desulfurization process was thinner for fine LGL compared with that of coarse LGL. Furthermore, the desulfurization product mainly consisted of gypsum and the decrease in LGL particle size can greatly enhance the gypsum crystal formation. These investigations are of significant importance for providing insights to improve WFGD efficiency with the utilization of low-grade limestone.

Photocatalytic Production of Methyl Formate by Methanol Self-Coupling: From Oxidative Dehydrogenation to Direct Dehydrogenation

Photocatalytic production of methyl formate (MF) by methanol direct dehydrogenation under an inert Ar atmosphere with Pd/TiO2 as photocatalyst was realized in the present work. For comparison, experiments of the oxidative dehydrogenation under a CO2 atmosphere were also conducted. The production rates of H2 in the gaseous product and MF in the liquid-phase product under different atmospheres were compared. Intermediates involved in the dehydrogenation processes were characterized by in situ DRIFTS analysis; on the basis of the results, a new mechanism of MF generation from methanol dehydrogenation was proposed: methanol successively breaks the O–H bond and C–H bond to form adsorbed formaldehyde, which then reacts with undissociated methanol to form MF rather than dimerize with another formaldehyde. In addition, it was evidenced that during the dehydrogenation in CO2, the intermediate formate derived from the reduction of CO2 further reacts with methanol to increase the production rate of MF.

Dechlorination of short-chain chlorinated paraffins by the metal sodium dispersion method

Short-chain chlorinated paraffins (SCCPs) are listed in Annex A (elimination) of the Stockholm Convention on persistent organic pollutants, and products containing SCCPs require detoxification. In the present study, the metal sodium (Na) dispersion method was applied to a wax sample containing SCCPs (58%, C10–C13 and Cl5–Cl9) to assess the dechlorination effect. Effective dechlorination of SCCPs was confirmed using 2-L and 20-L reaction systems. The initial concentrations of the wax (5, 10, 20, 30%), reaction time (10, 30, 60, 120, 180 min), and the ratios of the amount of Na dispersion and the initial amount of the wax containing SCCPs (Na/wax ratios; 3.9, 4.4, 5.2) were tested. The destruction efficiency of SCCPs was over 99.999% after 10 min of reaction at 90 °C under several conditions. The initial concentrations of the wax and the Na/wax ratios did not affect the results. The ultralow SCCP contents in exhaust gas from the reaction tank demonstrated a destruction removal efficiency of over 99.999999%. Trace levels of polychlorinated dibenzo-p-dioxins and furans, dioxin-like polychlorinated biphenyls, hexachlorobenzene, and pentachlorobenzene in the wax sample and treated materials (oil, water, and gas) met various regulatory values or exhibited the same levels as the environmental background. After dechlorination of the SCCPs, the main reaction products in the reaction liquid and final oil phase were identified as aliphatic compounds. The metal Na dispersion method was found to be an effective and decontaminated destruction technique for application to SCCPs in liquid-like samples with no formation of hazardous organic byproducts.

Process Water Recirculation during Hydrothermal Carbonization of Waste Biomass: Current Knowledge and Challenges

Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels and valuable carbonaceous materials. However, during HTC, a considerable amount of organics, initially present in the feedstock, are found in the process water (PW). PW recirculation is attracting an increasing interest in the hydrothermal process field as it offers the potential to increase the carbon recovery yield while increasing hydrochar energy density. PW recirculation can be considered as a viable method for the valorization and reuse of the HTC aqueous phase, both by reducing the amount of additional water used for the process and maximizing energy recovery from the HTC liquid residual fraction. In this work, the effects of PW recirculation, for different starting waste biomasses, on the properties of hydrochars and liquid phase products are reviewed. The mechanism of production and evolution of hydrochar during recirculation steps are discussed, highlighting the possible pathways which could enhance energy and carbon recovery. Challenges of PW recirculation are presented and research opportunities proposed, showing how PW recirculation could increase the economic viability of the process while contributing in mitigating environmental impacts.

Pyrolysis behaviors of coal-related model compounds catalyzed by Ni-modified HZSM-5 zeolite

The phenyl ethyl ether (PEE) and benzyloxybenzene (BOB) were selected as coal-related model compounds, and their catalytic pyrolysis behaviors in the presence of Ni-modified HZSM-5 zeolite were studied in a fixed-bed reactor. Nickel was introduced on HZSM-5 zeolite by wet impregnation. The catalysts were characterized by XRD, FT-IR, H2-TPR and NH3-TPD, and the effect of hydrogen reduction pretreatment on the catalytic performance was studied. NiO/HZSM-5 can significantly improve the yield of phenols in the liquid phase products of the two model compounds. Compared with Ni/HZSM-5, NiO/HZSM-5 exhibits superior pyrolysis conversion of PEE.

Gasification of Psidium guajava L. Waste Using Supercritical Water: Evaluation of Feed Ratio and Moderate Temperatures

Biomass waste, as raw material for renewable energy, is an attractive alternative since it does not compete with human food supply. An emerging alternative for its treatment is supercritical water gasification (SCWG), due to the high moisture content of some types of biomass. On this regards, guava fruit (Psidium guajava L.) is one of the most wasted agro-food products in Mexico. This motivated us to evaluate gasification of guava waste on dry biomass base under supercritical water conditions for the first time, with the aim of analyzing the impact of moderate temperatures and feed ratios as reaction parameters on gas products. Temperature was varied in the range of 673.15–773.15 K and using a batch reactor loaded with biomass:water (B:W) mass ratios of 1:1, 1:4, and 1:6. Furthermore, the obtained solid, liquid, and gas phase products were characterized. Hydrogen (H2), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4H10) were identified in gas phase and quantified by means of a gas chromatograph equipped with a TCD detector. Liquid and solid phase products were subjected to Fourier Transform Infrared spectroscopy analyses. This preliminary research indicated that high temperature operation and high biomass:water mass ratio enhanced gas yields (mol/kg) of about 4.137 for CH4, 6.705 for CO2, and 7.743 for H2; whereas the selectivity and gas efficiency for hydrogen was 65.26% and 58.94%, respectively.

A generalized pH acceleration model of nano-sol products and the effects of model misspecification on shelf-life prediction

In existing pH acceleration models, which are used to assess the shelf-life of liquid-phase nano-sol products, a mixture of normal distributions is commonly employed to describe the sizes of particles mixing from two populations. The Gaussian mixture model approach falls short when used to characterize the asymmetric distributions of particle sizes in subgroups. This work considers instead a broader class of a mixture of log-F distributions, to be embedded in a pH acceleration model. This study aims at understanding the impact of the new modeling approach, in the presence of model misspecification of the particle size distribution, on the accuracy and precision for making the shelf-life predictions. This study found that model misspecification indeed significantly affects the shelf-life predictions. The proposed method shows favorable finite sample performance on a simulated data set. Both the quantitative analysis of the impact due to model misspecification and the solution proposed herein could benefit practitioners in the long run.

Mechanism analysis of hydrogen production by microwave discharge in ethanol liquid

Microwave discharge in ethanol solution to produce hydrogen can obtain optimistic flow rate of hydrogen, because of the high mass transfer efficiency and water participation in the reaction. In this work, combined with liquid and gas products analysis, the main aim is to identify the reaction pathways of hydrogen production by microwave discharge plasma in ethanol-water mixtures. The features of radicals, gas-phase and liquid-phase products were investigated by the optical emission spectrum (OES) and gas chromatography (GC). The experimental results showed the gas-phase products included: H2, CO, CH4, C2H2, C2H4, C2H6, and CO2, and the liquid-phase products primarily included CH3CHO and CH3OH. By analysis, it is found that the amount of hydrogen production is closely related to the production of the intermediate product CH3CHO, and the OH radicals can inhibit the formation of solid carbon and by-product (C2H2), also promote the generation of hydrogen.

Core-shell (Pt/Cu-TiO2)-Graphene Composites for Photocatalytic Conversion of CO2 Into Fuel

The global emissions of greenhouse gases continue to rise by about 3% each year. Increasing levels of CO2 in the atmosphere can be subsided through CO2 utilization technologies such as conversion into fuels or other value-added products. Unlike other CO2 conversion techniques, photocatalysis utilizes a renewable and sustainable form of energy and doesn’t increase net CO2 emissions. Various catalysts have already been tested in numerous studies for the photocatalytic reduction of gaseous CO2. However, researchers have yet to discover an efficient photocatalyst that can reduce CO2 to yield economic amounts of value-added products under the irradiation of solar light. Hence, in this study, an attempt to enhance the performance of TiO2-based photocatalysts for application in CO2 conversion was made. Surface modifications to help enhancement the visible light absorption and the charge separation of TiO2 photocatalysts were pursued. More specifically, a novel TiO2-based photocatalyst, incorporating copper (Cu), platinum (Pt), and reduced graphene oxide (rGO), was synthesized. Several advanced material characterization tools were employed to investigate the photocatalytic composite’s intrinsic and enhanced properties, including XRD, Raman, DRS, PL, TEM, STEM-EDX, FT-IR, etc. A custom-built reactor was used to test the photocatalytic activity of the catalyst in reducing CO2 under different parameters and conditions, most importantly is the photocatalytic reduction of liquid CO2, which has been rarely investigated. Gas-phase and liquid-phase products from the different photoreactivity tests were analyzed using GC-FID and HPLC, respectively. Results from this study show that CO2 was successfully reduced to CO, CH4, and other products under the irradiation of UV light, with the activity being much higher for liquid CO2 than for gaseous CO2. Furthermore, the proposed catalyst rGO-(Pt/Cu-TiO2) showed higher or comparable activity results during the photocatalytic reduction of liquid CO2 when compared to other tested catalysts, specifically in the formation of aldehydes.

Lewis Acid Combined with Microwave Converts Hemicellulose and Cellulose in Cane Pith into 5-Hydroxymethyl furfural and Glucose

The paper using sugarcane pith as a raw material, the feasibility of aluminum hydroxide Lewis acid combined with microwave conditions to be used as a resource was investigated.Under the conditions of the combination of stellate acid and microwave, the 5-hydroxymethyl furfural (5-HMF) in 0.9% of the liquid phase product can be detected, and its low yield of 0.9% is worthy of further improvement. Economic analysis shows that the added value of 5-HMF produced by Lewis acid combined with microwave is as high as about 30,000 yuan per ton, and the prospect of resource utilization is huge. Use oxalic acid to hydrolyze the remaining cellulose and hemicellulose after 5-HMF is prepared from sugarcane pith to glucose, which is used in food and related products. It has very important application value in the industry. In this paper, the hemicellulose in cane pith is converted to 5-HMF under microwave reaction conditions, and then the remaining residue of the reaction is hydrolyzed with oxalic acid to produce glucose, which provides theoretical basis and technical support for further research on the high-value utilization of sugar cane pith in the future.

Performance research of lanthanum-loaded dolomite catalyst for pine catalytic gasification

To enhance the catalytic effect of dolomite, La/Dol catalyst was prepared by impregnation modification of dolomite with La (NO3)3 as additive. The catalyst was characterized by BET, SEM and XRD. With pine rods as raw materials and La/Dolas reforming catalysts, the effects of gasification temperature and La amount of catalysts on the catalytic gasification of pine were compared and analyzed in a self-made two-stage biomass gasification reforming experimental furnace. The results show that a small amount of La (2%) can obviously promote the forward progress of water gas reaction and perfect the catalytic reforming effect. Under the working condition of steam flow rate of 10 g/min, 2-La/Dol catalyst and reforming temperature of 750°C, with the increase of gasification temperature, the amount of H2 increases significantly, and the highest volume fraction of H2 increases from 28.51% (0-La/Dol) to 41.72% (2-La/Dol). La2O3 in the catalyst promotes the secondary cracking of tar. As a result, the tar content of liquid phase product is obviously reduced, and the number of functional groups is also reduced. La2O3 on dolomite surface occupies active sites, so carbon filaments are not suitable for accumulation and carbon deposition is inhibited. Carbonate (La2O2CO3) in the catalyst can react with carbon to slow down the carbon deposition on the surface and improve the activity and service life of the catalyst.

Rational Preparation of Atomically Precise Non-Alkyl Tin-Oxo Clusters with Theoretical to Experimental Insights into Electrocatalytic CO 2 Reduction Applications

Tin oxides (SnO2) have been widely utilized in electronics, nanolithography, and catalysis. As the atomically precise models of SnO2, tin-oxo clusters (TOCs) not only provide opportunities for mech...

Study on carbon rearrangements of CO2 co-feeding pyrolysis of corn stover and oak wood

Pyrolysis has been broadly applied to biomass valorization process to convert solid biomass waste into three phase value-added products such as biochar, pyrolytic oil, and pyrolytic gas. The carbon rearrangement process is highly affected by contents of cellulose, hemicellulose, and lignin due to their different structures. In this respect, this study laid great emphasis on the thermolytic behaviors of cellulosic corn stover (CS) and lignin-rich oak wood (OW) to understand carbon reallocations of them as a case study. In addition, CO2 was employed as a reaction medium for biomass pyrolysis to control the carbon redistribution between CO2 and CS/OW in line with the achievement of sustainable thermo-chemical conversion of biomass consuming a greenhouse gas (i.e., CO2). Lignin-rich OW showed higher tolerance to thermal degradation, thereby resulting in more biochar and less pyrolytic oil formations. During the CO2-assisted pyrolysis, carbon redistribution was appeared between liquid and gas phase products. This showed the gas phase reactions (GPRs) between volatilized liquid pyrolysates and CO2 with additional CO formation. To expedite the GPRs, Ni/SiO2 catalyst was employed. The CO2-assisted catalytic pyrolysis of CS and OW significantly improved dehydrogenation and deoxygenation, showing more than one order of magnitude higher production of H2 and CO.

Thermal thickening of nitrified liquid phase of digestate for production of concentrated complex fertiliser and high-quality technological water

Large production of liquid phase of digestate (LPD) characterised by low dry matter content increases the costs of LPD storage and transportation. Additionally, significant nitrogen losses result from LPD handling. The operation of biogas plants also requires large amounts of technological water, a scarce resource. The method of LPD nitrification and subsequent thermal thickening as a promising alternative treatment able to overcome those problems was investigated. The properties of thermally thickened nitrified LPD and of the distillate derived from vacuum evaporation of nitrified LPD were examined. The results show that over 99.9% of nitrogen was accumulated in thickened nitrified LPD. Total nitrogen (TN) concentration in thickened LPD ranged from 12 to 18 g/L depending on the distillate/thickened LPD volume ratio applied. The thickened LPD was also richer in other nutrients, which indicates its possible use as a concentrated complex fertiliser. TN concentration and conductivity in the distillate did not exceed 6 mg/L and 0.03 mS/m respectively, suggesting that the distillate may be useful as alternative source of technological water. It was concluded that the system consisting of nitrification and subsequent thermal thickening of nitrified LPD yields final products exhibiting significantly superior properties compared to thermal thickening of raw LPD, without requiring any additional chemical agents. The quality of these products is comparable to those obtained through advanced membrane processes.

Enhanced H2 production in the aqueous-phase reforming of maltose by feedstock pre-hydrogenation

Coupled hydrogenation and aqueous-phase reforming (APR) was studied as an approach to enhance H2 production from brewery wastewater, where maltose is the main component. Hydrogenation of maltose-bearing wastewater produced essentially maltitol. APR stage was performed over PtPd/C catalysts. Faster catalyst deactivation was observed in the APR of maltose than in the APR of maltitol, especially at high feedstock concentration. Higher H2 selectivity and yield were achieved in the APR of maltitol. The increase of temperature from 175 to 225 °C changed the reaction pathways, favouring the production of C1-C2 alkanes for both feedstocks. Higher selectivity to liquid-phase products was obtained in the APR of maltose, evidencing also reaction routes favouring the formation of solid carbonaceous deposits that lead to higher catalyst deactivation. The coupled process can be considered as efficient since H2 production compensated for H2 consumption in the hydrogenation stage and catalyst durability was increased.