Hydrogenation of Carbon Monoxide into Formaldehyde in Liquid Media

Abstract

Formaldehyde is a bulk chemical which is produced in excess of 30 million tons per annum and is growing in demand. However, the current production process requires methanol production, which is oxidized in air to produce formaldehyde, which must then be absorbed into water. Our recent work introduced a novel method to produce formaldehyde through CO hydrogenation in the aqueous phase. However, the aqueous phase has certain limitations which must be overcome to make it commercially viable. By applying a deuterium labeling technique and investigating the potential intermediates, the reaction mechanism was established which showed that solvents play a vital role in determining the yield. Various solvents were used for formaldehyde production, and the highest formaldehyde yield was achieved by using pure methanol followed by methanol−water mixtures. Formaldehyde reacts with methanol and water to produce hemiacetal and methylene glycol, respectively, thereby shifting the equilibrium of CO hydrogenation toward formaldehyde production. Methanol and water stabilize the hemiacetal and methylene glycol molecules, respectively, via hydrogen bonding. The highest yield of formaldehyde in methanol solvent was found to be 15.58 mmol L −1 g cat −1 at 363 K and 100 bar, which is four times higher than our previous report. The liquid phase method shown here has the potential to be greener and more sustainable than the commercial processes because it operates at low temperatures and results in 100% selectivity toward formaldehyde with no CO 2 generation. ■ INTRODUCTIONDue to the increasing global energy demand, many researchers have focused on reduction of energy consumption in the chemical industry. It is essential to search for more efficient, energy saving processes for the production of valuable chemicals. Many aspects can be considered and evaluated during process optimization. Increasing the conversion of reactants and product yield are often considered; however, process alternatives to save energy and capital costs are sometimes overlooked by researchers. Formaldehyde (HCHO) industrial production through methanol (CH 3 OH) partial oxidation dates back to 1882. 1 Since then, other methods of production such as methane (CH 4 ) partial oxidation 2−8 or CO 2 hydrogenation 9,10 were considered, but none were able to compete with the high conversion achieved by the methanol oxidation process. However, despite the high conversion of CH 3 OH and high selectivity toward HCHO, the industrial methods of HCHO production suffer from CO 2 generation as a byproduct 1 and a high energy consumption rate which leads to low exergy efficiency (43.2%). 11 A novel HCHO production method through direct CO hydrogenation in the aqueous phase using Ru−Ni/Al 2 O 3 was recently introduced, which could potentially increase the exergy efficiency with no CO 2 production, 12 as a result of bypassing the production of methanol and also the much lower reaction temperatures. However, it was not clear how the reaction proceeds in the aqueous phase. Although th...

The Prospecting Shortcut to an Old Molecule: Formaldehyde Synthesis at Low Temperature in Solution

“…The limitation of the method is the solubilityo fC Oa nd H 2 in water.I n2 016, the authors strikingly showed the effect of various solvents and co-solvents and they proposed four different reactionp athways for the formaldehyde formationf rom CO. [6] The best solvent was methanolw ith the highest yield of formaldehyde (15.6 mmol L À1 g cat À1 )a t9 0 8Ca nd ap ressure of 100 bar.This yield is four times higherthan the best in the previous report about hydrogenation in water,a nd the selectivity is 100 %t owards formaldehyde without anyCO 2 formation. In contrast, temperatures much highert han 80 8Ca re counterproductive for the yield, which is also in agreement with Le Chatelier 's principle.…”

“…[1][2][3] Besides these processes where formaldehydep lays am inor role as byproduct, there are more than 50 industrial processes where formaldehyde is ac rucial key ingredient and crucial buildingb lock for the manufacture of industrial products used in daily life such as processed wood, paints, cosmetics, resins,p olymers, adhesives, besides many others. All these branches sum up to multi-billion-dollar businesses with the production requirement of more than 30 megatons per year of formaldehyde, [6] respectively paraformaldehyde, asb uildingb lock and crosslinker.T he forecast for the growth of the global demandi s4% per annum.T he chemical industry produces formaldehyde in the gas phaset hrough partial oxidation and/or dehydrogenation of methanol since 1882, for example, in the so-called Formox process. All these branches sum up to multi-billion-dollar businesses with the production requirement of more than 30 megatons per year of formaldehyde, [6] respectively paraformaldehyde, asb uildingb lock and crosslinker.T he forecast for the growth of the global demandi s4% per annum.T he chemical industry produces formaldehyde in the gas phaset hrough partial oxidation and/or dehydrogenation of methanol since 1882, for example, in the so-called Formox process.…”

“…[5,6] The key to as uccessful conversion was performingt he reaction in the liquid rather than in the gaseous phase, andt hey found that the appropriate solvent played ac rucial role. [5,6] The key to as uccessful conversion was performingt he reaction in the liquid rather than in the gaseous phase, andt hey found that the appropriate solvent played ac rucial role.…”

Ruthenium‐Catalyzed Methylation of Amines with Paraformaldehyde in Water under Mild Conditions

“…[18] It was speculated that the use of an ucleophilic substrate, such as an amine, could attack the formaldehyde intermediate yielding an iminium cation and then undergos ubsequent reduction to lead to as ingle substrate acting as both the carbon andh ydrogen source in the methylation of amines for synthetic applications (Scheme1).The high importance of formaldehyde as ac hemical reagent for current andf uture technologiesi sr eflected in more than 50 industrial processesi nw hich formaldehyde plays ak ey role for the manufacture of products used in daily life. [15,[19][20][21] The product variety coversp rocessed wood, paints, cosmetics, resins, polymers, adhesives besides many others. Formaldehyde is usually processed in the liquid and even aqueous phase.…”

“…All these industries merge to am ulti-billion-dollar market based on more than 30 mega tonsp er year of formaldehydea sb uildingb lock and cross-linker. [15,[19][20][21] Currently, > 35 %o ft he world methanolp roduction is converted into formaldehyde,w hich turns formaldehyde into the number one product directly derived fromm ethanol. In this context,i ti s feasible to find furtherp rocesses using paraformaldehyde owing to its safe handling,a vailability and the fact that it can be derived from biomass (currently via syngas and methanol synthesis);t his will turn paraformaldehyde into ab ulk reagent availablef rom renewable sources in future biomass-a nd C 1based industries.…”