Propylene Oxide Production Research Articles

Saponification residue–sodium nitrate morphologically stable phase-change materials for medium- and high- temperature thermal energy storage

Saponification residue (SR) is a by-product of the chlor-alkali process used to produce propylene oxide. Owing to its high porosity and large specific area, SR is suitable as a carrier in the preparation of composite phase-change materials (CPCMs). This approach not only addresses the leakage issues associated with phase-change energy storage materials but also utilises solid waste. Herein, a morphologically stable CPCM was prepared using industrial SR solid waste and a phase-change material (sodium nitrate) via a hybrid sintering method. Phase analyses by X-ray diffractometer showed good chemical compatibility between sodium nitrate and SR. Further, scanning electron microscopy showed that SR has a porous structure, and sodium nitrate can be stably adsorbed on the pores and surface of SR. The maximum compressive strength of SR-CPCM was 43.37 MPa. Moreover, the highest loading capacity of SR for sodium nitrate was 50 wt%, resulting in no leakage and remarkable morphological stability. Differential scanning calorimetry indicated that SR-CPCM exhibited adequate thermal stability and that the latent heat increased with rising nitrate content, reaching a maximum value of 99.24 J/(g·°C). Importantly, after 100 thermal cycles, SR-CPCM demonstrated good stability in terms of chemical compatibility and latent heat. These results demonstrate the potential of SR as a carrier material for energy storage applications.

Modulating Ti coordination environment in Ti-containing materials by sulfation for synergizing with Au sites to facilitate propylene epoxidation

Modulating the coordination environment of Ti sites in Ti-containing materials to synergize with Au sites is a crucial issue to boost the process of propylene epoxidation with H2 and O2 to produce propylene oxide (i.e., HOPO), but still remains a great challenge. Herein, we report a facile strategy to tailor the coordination states and electronic properties of Ti sites. The sulfur-decorated Ti-SiO2 (i.e., Ti sites anchored onto silica) with moderate sulfur loading (Ti-SiO2-S-M) can synergize well with Au sites for the HOPO process with high activity, propylene oxide (PO) selectivity, and H2 efficiency, which are superior to those achieved on the referenced Ti-SiO2 synergizing with Au sites. Multiple characterizations, in-situ diffuse reflectance infrared Fourier transform spectroscopy of propylene and PO, PO conversion experiment, and kinetics behaviors demonstrate that the superior advantages of Ti-SiO2-S-M against Ti-SiO2 result from the increased Ti binding energy, improved hydrophobicity, and weakened acidity, which simultaneously facilitate the adsorption of propylene and promote the desorption of PO. This insight reported here could guide the rational design and optimization of Ti-containing materials to synergize with Au catalysts for propylene epoxidation.

Spatial‐coupled Ampere‐level Electrochemical Propylene Epoxidation over RuO2/Ti Hollow‐fiber Penetration Electrodes

AbstractThe electrochemical propylene epoxidation reaction (PER) provides a promising route for ecofriendly propylene oxide (PO) production, instantly generating active halogen/oxygen species to alleviate chloride contamination inherent in traditional PER. However, the complex processes and unsatisfactory PO yield for current electrochemical PER falls short of meeting industrial application requirements. Herein, a spatial‐coupling strategy over RuO2/Ti hollow‐fiber penetration electrode (HPE) is adopted to facilitate efficient PO production, significantly improving PER performance to ampere level (achieving over 80 % PO faradaic efficiency and a maximum PO current density of 859 mA cm−2). The synergetic combination of the penetration effect of HPE and the spatial‐coupled reaction sequence, enables the realization of ampere‐level PO production with high specificity, exhibiting significant potentials for economically viable PER applications.

Spatial-coupled Ampere-level Electrochemical Propylene Epoxidation over RuO2/Ti Hollow-fiber Penetration Electrodes.

The electrochemical propylene epoxidation reaction (PER) provides a promising route for ecofriendly propylene oxide (PO) production, instantly generating active halogen/oxygen species to alleviate chloride contamination inherent in traditional PER. However, the complex processes and unsatisfactory PO yield for current electrochemical PER falls short of meeting industrial application requirements. Herein, a spatial-coupling strategy over RuO2/Ti hollow-fiber penetration electrode (HPE) is adopted to facilitate efficient PO production, significantly improving PER performance to ampere level (achieving over 80 % PO faradaic efficiency and a maximum PO current density of 859 mA cm-2). The synergetic combination of the penetration effect of HPE and the spatial-coupled reaction sequence, enables the realization of ampere-level PO production with high specificity, exhibiting significant potentials for economically viable PER applications.

Plant Design for the Production of Propylene Oxide by Isopropylbenzene 2-phenylpropane, or (1-Methylethyl) Benzene (Cumene)

Cumene is a colorless, volatile liquid with a gasoline-like odor. It’s also known as isopropylbenzene, 2-phenylpropane, or (1-methylethyl) benzene. It’s a natural component of coal tar and crude oil, and it can also be employed in gasoline as a blending component. Cumene hydroperoxide is produced by oxidizing cumene with benzene and propylene in the presence of air. As a result, the cumene hydroperoxide is changed to cumyl alcohol, which is then transformed to propylene without the use of oxygen. Propylene oxide is an organic compound produced through various methods such as the cumene process and the hydroperoxide process. The cumene method is preferred due to its low by-product production and high market value of co-products. The reactive distillation process is a feasible method for producing propylene oxide with high purity and reduced costs. Future work includes optimizing processes, developing new catalysts, and improving efficiency. Propylene oxide has practical applications in the production of polyurethane foams, coatings, adhesives, polyether polyols, and propylene glycols.

Direct propylene epoxidation with molecular oxygen over titanosilicate zeolites.

The direct epoxidation of propylene with molecular oxygen represents a desired route for propylene oxide (PO) production with 100% theoretical atomic economy. However, this aerobic epoxidation reaction suffers from the apparent trade-off between propylene conversion and PO selectivity, and remains a key challenge in catalysis. We report that Ti-Beta zeolites containing isolated framework Ti species can efficiently catalyze the aerobic epoxidation of propylene. Stable propylene conversion of 25% and PO selectivity of up to 90% are achieved at the same time, matching the levels of industrial ethylene aerobic epoxidation processes. H-terminated pentacoordinated Ti species in Beta zeolite frameworks are identified as the preferred active sites for propylene aerobic epoxidation and the reaction is initiated by the participation of lattice oxygen in Ti-OH. These results are expected to spark new technology for the industrial production of PO toward more sustainable chemistry and chemical engineering.

Environmental impacts and mitigation potentials of CO2-based biodegradable plastic based on life cycle assessment – A case study of poly(propylene carbonate)

CO2-based biodegradable plastics are potential solutions for reducing fossil-fuel consumption, mitigating climate change, and addressing plastic pollution by reducing plastic waste accumulation. Poly(propylene carbonate) (PPC) is a commercial CO2-based biodegradable plastic derived from CO2 and propylene oxide (PO), and it has been used in flexible packaging and mulching film applications. However, the environmental performance of PPC is still unknown. Since China has become the largest producer of PPC in the world, this study takes the industrial production technologies of PPC and its feedstocks in China as an example. The cradle-to-gate life-cycle inventory of PPC resin was compiled, and life-cycle impact assessment was performed to assess the environmental impacts of PPC and mitigation potentials based on the ReCiPe 2016 method. Results indicated that PPC synthesis has the greatest impact on the environment (contributions of 38–95% of 16 environmental impact categories), followed by PO production. Technological innovation and renewable energy substitution scenarios were developed to explore the mitigation potential of PPC. We found that supercritical polymerization technology has greater mitigation potential than photovoltaic power substitution, which could reduce 17 impact categories of PPC by 17–96% by reducing energy and dichloromethane consumption during PPC synthesis. Photovoltaic power substitution reduced 2–22% of 11 impact categories of PPC. Compared with conventional plastics, PPC had advantages over conventional plastics in terms of 17 impact categories. The environmental impacts of PPC were 2–98% lower than those of conventional plastics. This study emphasizes the importance of technological innovation in reducing the lifecycle environmental impacts of PPC and provides a basis for environmental performance of CO2-based biodegradable plastics and the potential to replace conventional plastics. Policy implications for innovations in synthesis technology, sustainable feedstocks and environmental impact assessment were proposed, which could provide valuable insights for practitioners and policymakers in enhancing the sustainability of the plastics industry through biodegradable plastic alternatives.

Aliphatic Olefin Epoxidation with Hydrogen Peroxide Catalyzed by an Integrated Mn/TS-1/N System

AbstractPropylene liquid-phase epoxidation with 50–75% H2O2 is an important process for the industrial production of propylene oxide (PO). To realize a propylene epoxidation process that proceeds with low hydrogen peroxide concentration, we developed an integrated Mn/TS-1/N catalytic system via in-situ reaction of Mn/TS-1 with an N-donor ligand, affording the PO product in excellent yield with only 30 wt% H2O2. Other long-chain aliphatic epoxides were also readily synthesized by this catalytic epoxidation system. Moreover, in addition to the standard micro-pressure reactor, a continuous-flow microreactor was developed that executed the hydrogen peroxide propylene oxide (HPPO) process with excellent efficiency for 1300 hours. This innovative Mn/TS-1/N catalyzed epoxidation represents a promising direction for advancing HPPO industrial processes, offering improved efficiency while minimizing the reliance on high concentrations of H2O2.

Interchain-expanded extra-large-pore zeolites.

Stable aluminosilicate zeolites with extra-large pores that areopen through rings of more than 12 tetrahedra could be used to process molecules larger than those currently manageable in zeolite materials. However, until very recently1-3, they proved elusive. In analogy to the interlayer expansion of layered zeolite precursors4,5, we report a strategy that yields thermally and hydrothermally stable silicates by expansion of a one-dimensional silicate chain with an intercalated silylating agent that separates and connects the chains. As a result, zeolites with extra-large pores delimited by 20, 16 and 16 Si tetrahedra along the three crystallographic directions are obtained. The as-made interchain-expanded zeolite contains dangling Si-CH3 groups that, by calcination, connect to each other, resulting in a true, fully connected (except possible defects) three-dimensional zeolite framework with a very low density. Additionally, it features triple four-ring units not seen before in any type of zeolite. The silicate expansion-condensation approach we report may be amenable to further extra-large-pore zeolite formation. Ti can be introduced in this zeolite, leading to a catalyst that isactive in liquid-phase alkene oxidations involving bulky molecules, which shows promise in the industrially relevant clean production of propylene oxide using cumene hydroperoxide as an oxidant.

New insights into brominated epoxy resin type WPCBs pyrolysis mechanisms: Integrated experimental and DFT simulation studies

Pyrolysis is a recycling technology for waste circuit boards (WPCBs) with a wide range of applications. In this research, the brominated epoxy resin (BER) type WPCBs were taken as the research object, and the optimal pyrolysis process parameters were determined. Combined with experiments and density functional theory (DFT) calculations, the pyrolysis gaseous generation pattern and product distribution of BER type WPCBs were analyzed, and the generation mechanism of phenol, bromide and other pyrolysis products was investigated in depth. The results of the study showed that the pyrolysis rate of WPCBs exceeded 95 % under optimal reaction conditions. In the initial phase of the pyrolysis of WPCBs, the BER's CO bonds and a portion of Ph-Br bonds will be broken, leading to the production of intermediates such propylene oxide, bisphenol A, isopropyl alcohol, tetrabromobisphenol A and HBr. Among them, propylene oxide can generate ethylene oxide through free radical reaction. In the second stage, intermediates such as bisphenol A undergo homolytic cleavage and radical addition to form phenols, bromides, alcohols, ketones and other pyrolysis products.

Tandem photocatalytic production of H2O2 and propylene oxide on 5-Bromoisatin modified carbon nitride

Propylene oxide (PO) is an important raw material and synthetic intermediate for organic chemical synthesis. The direct in-situ synthesis of hydrogen peroxide (H2O2) using molecular oxygen to produce PO is considered as one of the most promising methods. Herein, we propose a photocatalytic multiphase system for the production of PO with oxygen. The ligand 5-bromoindoline-2,3-dione doped graphitic carbon nitride (CN/Bd) was employed as a photocatalyst for the in-situ production of H2O2, in tandem with epoxidation catalyst titanium silicalite-1 (TS-1) to achieve the epoxidation of propylene. This system achieved H2-free and efficient production of PO at room temperature with a high yield of 1.33 mmol·g−1·h−1, the selectivity of PO over 99% and H2O2 utilization efficiency over 95%. The combination of in-situ H2O2 generation and selective oxidation reaction realizes the efficient utilization of H2O2 and provides guidance for safer industrial production of PO.

Energy-saving process development for the purification of propylene glycol based on MVR heat pump distillation combined with thermally coupled technology

In the process of recovering organic compounds from wastewater generated by propylene oxide (PO) production plant, the low concentration of propylene glycol (PG) in the wastewater makes it difficult and energy-intensive to achieve the high concentrations purify of PG using conventional distillation technology. Additionally, there is no publicly available commercial technology for this purpose. Therefore, the aim of this work is to develop an energy-efficient PG purification process based on mechanical vapor recompression (MVR) heat pump distillation combined with thermally coupled technology. Several energy-saving methods were implemented as follows. Firstly, MVR distillation technology was used to purify PG from 2.22% to 33.3% in the PG concentration tower, and the gas at the top of the tower was compressed and pressurized to serve as the heating medium for the reboiler, which significantly reduced the consumption of fresh steam. Secondly, in order to achieve heat matching, the dehydration tower was divided into two parts. The surplus steam compressed by the compressor was then served as the heat source for the reboiler of the first dehydration tower to reduce steam consumption, while achieving 98.7% water removal. Thirdly, the condenser of the de-heavy tower and the scraping film evaporator were thermally coupled to reduce the consumption of heating and cooling media. Based on the aforementioned energy-saving measures, the developed optimization process can achieve PG purification of over 90%, while significantly reducing costs. The total annual cost (TAC) is reduced by 34.89% compared to the traditional distillation process.

Reaction-Driven Formation of Ag-Cu Alloy Nanostructures from Cu@Ag Core-Shell Nanoparticles Analyzed by Moirè Patterns Using Environmental TEM Images

Well defined Cu@Ag core@shell (or core-shell) nanoparticles have been synthesized through a carbon monoxide (CO)-assisted solution phase method. These Cu@Ag nanoparticles transformed into Ag-Cu alloy nanostructures under propylene epoxidation conditions. Environmental transmission electron microscopy (ETEM) revealed the structural evolution of Cu@Ag nanoparticle under different propylene-to-oxygen (PP/O2) ratios based on the Moirè pattern analysis of the micrographs obtained in situ. The counter diffusion of Ag and Cu atoms, from the shell and core respectively, was observed at the PP/O2 ratio of 2:1. When the PP/O2 ratio was 1:1, Cu@Ag core-shell nanoparticles turned into alloy nanostructures. The transformation from Cu@Ag to Ag-Cu alloy nanoparticles changed the catalytic performance in the production of propylene oxide from partial oxidation of propylene, resulting in a yield of 1.14 min−1 and selectivity of 79% when the PP/O2 ratio was 2:1. This study shows besides temperature and pressure, other less-studied factors of reaction conditions such as composition of reactants may play critical roles in the dynamics of bimetallic nanostructures, thus their corresponding catalytic performances. This study develops the techniques on the applications of Moirè patterns for analyzing the dynamics of bimetallic core-shell nanostructures at atomic scale using (S)TEM micrographs.

Catalytic Performance of Amorphous Ti/SiO2 in the Gas‐Phase Epoxidation of Propylene with H2O2

AbstractThe epoxidation of propylene with dilute H2O2 aqueous solution over titanium silicalite‐1 (TS‐1) zeolite catalyst is a green chemical reaction for propylene oxide (PO) production. Carrying out the reaction in gas‐phase can get rid of problems caused by using methanol solvent. This paper reports an attempt of using non‐zeolite catalyst for the gas‐phase epoxidation. Amorphous Ti/SiO2, obtained by grafting amorphous SiO2 with TCl4 in ethanol solvent in a chemical liquid‐phase deposition (CLD) process, has been used as the catalyst. Results show that the CLD Ti/SiO2 with appropriate Si/Ti molar ratio is an active catalyst for gas‐phase epoxidation, achieving 9.8 % propylene conversion and 66.9 % PO selectivity with 40.3 % H2O2 utilization, which indicates that this amorphous Ti/SiO2 catalyst deserves extensive studies in the future.

Visible Light-Driven Sandwich-like g-C3N4-Catalyzed Oxidation to Produce Cumene Hydroperoxide

Cumene hydroperoxide (CHP) is an important intermediate for the production of phenol, acetone, propylene oxide, and other raw materials in the petrochemical industry. However, due to the high reaction temperature and pressure, the current process for the industrial production of CHP has problems of potential safety hazards and high energy consumption. In this work, carbon nitride (g-C3N4) with a unique sandwich structure was discovered as a photocatalyst. It efficiently activates molecular oxygen in the air, oxidizes cumene (CM) to prepare CHP, and realizes high atom economy transformation at room temperature, atmospheric pressure, and solvent-free conditions. The continuous flow strategy was adopted to improve the gas–liquid mass transfer efficiency and reduce the phenomenon of back-mixing, thereby reducing the decomposition of the products and improving the product selectivity. The conversion rate was the same as that of the batch reaction, reaching 23%. The selectivity of the product CHP increased from 82 to 92%, and the reaction residence time was shortened from 10 h to 70 min. The catalysts have the advantages of high efficiency, easy availability, environmentally friendly, etc., and are recyclable and stable. This work provides a new strategy for establishing green, sustainable, clean, and efficient methods for the preparation of peroxides.

Ti-MWW Catalysts for Propylene Oxide Production: Influence of Si/Ti Ratio and Calcination Conditions

Titanium silicates of MWW structures with different Si/Ti ratios were prepared via hydrothermal synthesis using piperidine as the structure directing agent and boric acid as the crystallization agent. All the syntheses resulted in highly crystalline materials independent of the Si/Ti ratio. The observed morphology showed MWW-like well-defined thin hexagonal platelets. The synthesized Ti-MWW materials exhibited higher surface areas and partial meso-porosity compared to the commercial TS-1 catalyst. The coordination of the Ti-species was investigated by UV–vis- and IR-spectroscopy. The MWW titanium silicates were tested for the catalytic performance in the epoxidation of propylene in a laboratory-scale trickle bed reactor to compare their clear different physico-chemical properties with the commercial TS-1. The synthesized Ti-MWW materials showed significantly higher catalytic activities, up to 3.5 times, using acetonitrile as the solvent and enhanced epoxide selectivities partially up to 100% in methanol unlike TS-1. The effect of the Ti content in the MWW and the calcination conditions were investigated in propylene epoxidation, revealing the beneficial effect of a lower calcination temperature and an increased Ti content on the activity. The catalytic results were correlated with the physico-chemical properties of the synthesized materials.Graphical

Adjusting the Chemical Reactivity of Oxygen for Propylene Epoxidation on Silver by Rational Design: The Use of an Oxyanion and Cl

The development of catalysts for propylene oxide production from direct epoxidation using propylene and oxygen remains a challenge. Compared to ethylene epoxidation, where selectivity on silver catalysts is high, the low selectivity to produce propylene oxide over silver is partially attributed to the lack of electrophilic oxygen under propylene epoxidation reaction conditions. Here, we investigate how to mediate the chemical reactivity of oxygen by theory-inspired experiments for propylene epoxidation. We show how adding electrophilic-O via SO4 oxyanions to the surface of silver increases epoxide selectivity. Moreover, we show how the addition of Cl to the SO4-modified catalyst activates the oxyanion, giving a more than 4-fold increase in selectivity to propylene oxide. Finally, we explore different systems using DFT and draw a picture on how the next catalyst/co-catalyst systems should be tuned to design a catalyst with high selectivity for direct propylene oxidation.

Oxidation of Organic Compounds in Supercritical Fluid Conditions During Disposal of Industrial Waste Waters of Nizhnekamskneftekhim PJSC and Kazanorgsintez PJSC

The study performed on the supercritical aqueous oxidation of organic compounds in the water runoff of Nizhnekamskneftekhim PJSC, which was formed at the stage of epoxidation of propylene with ethylbenzene hydroperoxide during the joint production of propylene and styrene oxide, as well as run-off at PJSC "Kazanorginsez", when obtaining phenol and acetone from "Bisphenol-A" plant. The article studies a continuous operation mode on a flow reactor with induction heating (the drain from PJSC "Nizhnekamneftekhim") and periodic on coming from PJSC "Kazanorginsez". It was identified that close to complete oxidation in the presence of heterogeneous catalysts was achieved in a continuous mode at a temperature of 823 K and an excess of oxygen equal to 4.

Plasma-Induced Selective Propylene Epoxidation Using Water as the Oxygen Source.

Propylene oxide (PO) is a critical gateway chemical used in large-scale production of plastics and many other compounds. In addition, PO is also used in many smaller-scale applications that require lower PO concentrations and volumes. These include its usage as a fumigant and disinfectant for food, a sterilizer for medical equipment, as well as in producing modified food such as starch and alginate. While PO is currently mostly produced in a large-scale propylene epoxidation chemical process, due to its toxic nature and high transport and storage costs, there is a strong incentive to develop PO production strategies that are well-suited for smaller-scale on-site applications. In this contribution, we designed a plasma-liquid interaction (PLI) catalytic process that uses only water and C3H6 as reactants to form PO. We show that hydrogen peroxide (H2O2) generated in the interactions of water with plasma serves as a critical oxidizing agent that can epoxidize C3H6 over a titanium silicate-1 (TS-1) catalyst dispersed in a water solution with a carbon-based selectivity of more than 98%. As the activity of this plasma C3H6 epoxidation system is limited by the rate of H2O2 production, strategies to improve H2O2 production were also investigated.

Green synthesis of propylene oxide directly from propane

The chemical industry faces the challenge of bringing emissions of climate-damaging CO2 to zero. However, the synthesis of important intermediates, such as olefins or epoxides, is still associated with the release of large amounts of greenhouse gases. This is due to both a high energy input for many process steps and insufficient selectivity of the underlying catalyzed reactions. Surprisingly, we find that in the oxidation of propane at elevated temperature over apparently inert materials such as boron nitride and silicon dioxide not only propylene but also significant amounts of propylene oxide are formed, with unexpectedly small amounts of CO2. Process simulations reveal that the combined synthesis of these two important chemical building blocks is technologically feasible. Our discovery leads the ways towards an environmentally friendly production of propylene oxide and propylene in one step. We demonstrate that complex catalyst development is not necessary for this reaction.