Modeling of molybdenum transport and pressure drop increase in fixed bed reactors used for selective oxidation of methanol to formaldehyde using iron molybdate catalysts

A Review and Experimental Revisit of Alternative Catalysts for Selective Oxidation of Methanol to Formaldehyde

The selective oxidation of methanol to formaldehyde is a growing million-dollar industry, and has been commercial for close to a century. The Formox process, which is the largest production process today, utilizes an iron molybdate catalyst, which is highly selective, but has a short lifetime of 6 months due to volatilization of the active molybdenum oxide. Improvements of the process’s lifetime is, thus, desirable. This paper provides an overview of the efforts reported in the scientific literature to find alternative catalysts for the Formox process and critically assess these alternatives for their industrial potential. The catalysts can be grouped into three main categories: Mo containing, V containing, and those not containing Mo or V. Furthermore, selected interesting catalysts were synthesized, tested for their performance in the title reaction, and the results critically compared with previously published results. Lastly, an outlook on the progress for finding new catalytic materials is provided as well as suggestions for the future focus of Formox catalyst research.

Methanol to Formaldehyde: An Overview of Surface Studies and Performance of an Iron Molybdate Catalyst

Formaldehyde is a primary chemical in the manufacturing of various consumer products. It is synthesized via partial oxidation of methanol using a mixed oxide iron molybdate catalyst (Fe2(MoO4)3–MoO3). This is one of the standard energy-efficient processes. The mixed oxide iron molybdate catalyst is an attractive commercial catalyst for converting methanol to formaldehyde. However, a detailed phase analysis of each oxide phase and a complete understanding of the catalyst formulation and deactivation studies is required. It is crucial to correctly formulate each oxide phase and influence the synthesis methods precisely. A better tradeoff between support and catalyst and oxygen revival on the catalyst surface is vital to enhance the catalyst’s selectivity, stability, and lifetime. This review presents recent advances on iron molybdate’s catalytic behaviour for formaldehyde production—a deep recognition of the catalyst and its critical role in the processes are highlighted. Finally, the conclusion and prospects are presented at the end.

Structured photocatalytic systems: photocatalytic coatings on low-cost structures for treatment of water contaminated with micropollutants-a short review

The persistence of many micropollutants in water and wastewater is of great concern to the contemporary scientific community. Several types of advanced techniques such as heterogeneous photocatalysis are being used for the degradation of micropollutants in waters from domestic, industrial, and agricultural activities. Thus, structured photocatalytic systems are a great alternative in the development of photocatalytic reactors and continuous water treatment systems, as they present good autonomy during the treatment process. Many aspects such as type and geometry of the catalytic structure to be developed must be carefully chosen for the proper functioning of the system, as well as the best routes by which the photocatalysts will be immobilized. In this sense, this work brings the main photocatalytic coating techniques in low-cost structures for the treatment of water and wastewater contaminated with micropollutants. The methodologies and synthesis parameters that can influence the final result of the coating were highlighted, as well as the ability to reuse photocatalysts and methods for pretreating the structural surface. The dip-coating technique was the most reported among the current works due to its simplicity and, predominantly, the pretreatment techniques of the structure are still cleaning the surface with water, soap, and also some alcohols.

Hydroxyapatite supported molybdenum oxide catalyst for selective oxidation of methanol to formaldehyde: studies of industrial sized catalyst pellets

Promising alternative catalysts for the Formox process as industrial sized pellets and the influence of pellet density on catalyst performance.

Alkali Earth Metal Molybdates as Catalysts for the Selective Oxidation of Methanol to Formaldehyde—Selectivity, Activity, and Stability

Alkali earth metal molybdates (MMoO4, M = Mg, Ca, Sr, and Ba) were investigated as catalysts for the selective oxidation of methanol to formaldehyde in the search for more stable alternatives to the current industrial iron molybdate catalyst. The catalysts were prepared by either sol-gel synthesis or co-precipitation with both stoichiometric ratio (Mo:M = 1.0) and 10 mol% to 20 mol% excess Mo (Mo:M = 1.1 to 1.2). The catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, Raman spectroscopy, temperature programmed desorption of CO2 (CO2-TPD), and inductively coupled plasma (ICP). The catalytic performance of the catalysts was measured in a lab-scale, packed bed reactor setup by continuous operation for up to 100 h on stream at 400 °C. Initial selectivities towards formaldehyde of above 97% were achieved for all samples with excess molybdenum oxide at MeOH conversions between 5% and 75%. Dimethyl ether (DME) and dimethoxymethane (DMM) were the main byproducts, but CO (0.1%–2.1%) and CO2 (0.1%–0.4%) were also detected. It was found that excess molybdenum oxide evaporated from all the catalysts under operating conditions within 10 to 100 h on stream. No molybdenum evaporation past the point of stoichiometry was detected.