Methanol oxidation catalyst

Abstract

The present invention provides a catalyst composition comprising: i) a catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO); and ii) a metal oxide A, which is an alkaline earth metal oxide or zirconium oxide, or a combination of zirconium oxide and cerium oxide.

Description

[Technical Field]

[0001] The present invention relates to a catalyst composition for the oxidation of methanol to formaldehyde, particularly one that reduces the production of the undesirable by-product methyl formate. [Background technology]

[0002] Processes for producing formaldehyde by catalytic oxidation of methanol have been known for many years. One well-known process involves the oxidation of methanol over a mixed oxide catalyst, usually containing oxides of iron and molybdenum: CHOH + 0.5O → CHO + HO. Plants operating this process typically operate at reactor inlet pressures of approximately 1 barg or less. Further increases in pressure can cause problems due to loss of catalyst selectivity, resulting in increased formation of unwanted by-products such as carbon monoxide, dimethyl ether, and methyl formate. This results in reduced utilization of the added feedstock and higher operating costs than if no by-products were formed. Considering that methanol contributes >90% to total operating costs, minimizing these losses is highly desirable.

[0003] Methyl formate can be formed according to the following reaction: 2CH3OH+O2→HCOOCH3+2H2O 2HCHO→HCOOCH3 CH3OH+CH2O+1 / 2O2→HCOOCH3+H2O HCOOH+CH3OH⇔HCOOCH3+H2O

[0004] Reducing methyl formate is desirable because it also reduces formaldehyde yield and operator profitability, leading to the production of formic acid according to the equilibrium reaction described above, which is problematic for manufacturers of adhesives and urea formaldehyde, for example, and requires the addition of buffers to formalin solutions.

[0005] The present invention seeks to overcome one or more of the above-mentioned problems of the prior art. In particular, the present invention seeks to reduce the loss of methyl formate in the formaldehyde production process. Summary of the Invention

[0006] Accordingly, the present invention provides a catalyst composition comprising: i) a catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); ii) a metal oxide A which is an alkaline earth metal oxide or zirconium oxide, or a combination of zirconium oxide and cerium oxide;

[0007] In particular, the present invention relates to a catalyst composition according to the present invention, i) granules of catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3); ii) metal oxide A; the catalyst composition comprises a physical blend of a catalyst material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO) and a metal oxide A; A catalyst composition is provided in which at least a portion of metal oxide A forms a coating around granules of a catalyst material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3).

[0008] Such catalyst compositions advantageously promote the oxidation of methanol to formaldehyde without reducing methyl formate selectivity and without significantly reducing methanol conversion.

[0009] The present invention also provides pellets containing the catalyst composition of the present invention. Such pellets retain their hardness at relatively low densities, i.e., exhibit an improved hardness-to-density ratio. Lower-density pellets are more active and more selective in methanol oxidation. For example, over-oxidation of formaldehyde is reduced, resulting in less carbon monoxide formation. However, relatively low-density pellets have traditionally been less durable. The pellets of the present invention address this issue.

[0010] The present invention also provides a process for preparing a catalyst composition according to the present invention, comprising the steps of: i) calcining metal oxide A to provide calcined metal oxide A; ii) mixing the calcined metal oxide A with a catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO); iii) calcining the mixture to provide a catalyst composition; The present invention provides a process including:

[0011] The present invention also provides a process for preparing the catalyst composition of the present invention, comprising the steps of: i) calcining metal oxide A to provide calcined metal oxide A; ii) calcining the catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO); ii) mixing the calcined metal oxide A with a calcined catalyst material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO); The present invention provides a process including:

[0012] The present invention also provides a process for producing formaldehyde from methanol, comprising the steps of: supplying a feed stream comprising methanol and an oxygen-containing gas to a reactor; and reacting the methanol in the gas phase with the oxygen-containing gas in the reactor in the presence of a catalyst composition or tablet according to the present invention.

[0013] The present invention also provides the use of the catalyst composition of the present invention to reduce the loss of methyl formate in a process for producing formaldehyde from methanol. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a chart showing methyl formate selectivity versus methanol conversion for a catalyst composition according to the present invention and a comparative catalyst. [Figure 2] 1 is a chart showing methyl formate selectivity versus methanol conversion for additional catalyst compositions according to the present invention and comparative catalysts. [Figure 3] 1 is a chart showing methyl formate selectivity versus methanol conversion for additional catalyst compositions according to the present invention and comparative catalysts. [Figure 4] 1 is a chart showing methyl formate selectivity versus methanol conversion for additional catalyst compositions according to the present invention and comparative catalysts. [Figure 5] 1 is a chart showing density versus hardness for pellets containing a catalyst composition according to the present invention. [Figure 6] 1 is a TEM image of a catalyst composition according to the present invention. [Figure 7] 1 is a collection of EDS images of catalyst compositions according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The catalyst composition of the present invention comprises a catalyst material that is typically a mixture of iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) with a Mo:Fe ratio of 2 to 3. Suitable catalyst materials have a molybdenum content of 2 to 20 m 2 / g, e.g., 3 to 10 m 2 / g。 Catalytic materials including iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) may optionally contain oxides of other metals, such as copper, as described, for example, in WO 2022 / 079434, and / or vanadium, aluminum, silicon, calcium, cobalt, chromium, magnesium, manganese, nickel, zinc, silver, and titanium. As will be appreciated by those skilled in the art, such additional components are present in small amounts, for example, about 1.0 wt% or less, typically 0.5 wt% or less.

[0016] The catalyst composition of the present invention also includes ii) a metal oxide A, which is an alkaline earth metal oxide or zirconium oxide, or a combination of zirconium oxide and cerium oxide. In one embodiment, metal oxide A is an alkaline earth metal oxide. A preferred alkaline earth metal oxide is magnesium oxide. In one embodiment, metal oxide A is zirconium oxide. In another embodiment, metal oxide A is a combination of zirconium oxide and cerium oxide, for example, in a weight ratio ranging from 5:1 to 1:5, typically about 1:1.

[0017] Typically, the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is in the form of granules, preferably resulting from an agglomeration of particles of the catalytic material. Preferably, the catalytic composition is a physical blend of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) with metal oxide A. For example, discrete solid forms of the catalytic material and metal oxide A are present in the catalytic composition. Preferably, at least a portion of metal oxide A forms a coating around granules of the catalytic material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3). For example, the discrete solid form of metal oxide A is typically homogeneously distributed over substantially all of the surface of the granules of catalytic material and is bound or fixed to the granules by physical or chemical bonds. In other words, the catalyst composition comprises granules of a catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO), preferably dry coated with a homogeneous coating of metal oxide A. Typically, at least about 50% by weight of metal oxide A forms a coating around the granules of catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO).

[0018] Typically, metal oxide A may be present in an amount of about 15 wt% or less of the total weight of the catalyst composition, preferably about 5 wt% or less of the total weight of the catalyst composition, more preferably about 3 wt% or less of the total weight of the catalyst composition, and even more preferably about 2 wt% or less of the total weight of the catalyst composition. Metal oxide A is typically present in an amount of at least about 0.1 wt% of the total weight of the catalyst composition.

[0019] The catalyst composition may further comprise an alkali metal, preferably sodium. Preferably, metal oxide A is impregnated with the alkali metal. The alkali metal is preferably present in an amount of about 5% by weight or less of metal oxide A, preferably about 1% by weight or less of metal oxide A, and more preferably about 0.5% by weight or less of metal oxide A. The alkali metal is typically present in an amount of at least about 0.1% by weight of the total weight of the catalyst composition.

[0020] To prepare the catalyst composition, a catalyst material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is first typically sieved to obtain a particle size in the range of about 200 to about 400 μm as measured by sieving. In one embodiment, the catalyst material comprising iron molybdate (Fe2(MoO4)3) and molybdenum trioxide (MoO3) is then calcined, typically at a temperature in the range of about 400 to about 550°C, before being mixed with metal oxide A. In this embodiment, there is typically no calcination step after the step of mixing the catalyst material comprising iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3) with metal oxide A. In an alternative embodiment, the catalyst material comprising iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3) is not calcined before being mixed with metal oxide A. In this alternative embodiment, calcination is required after mixing the catalytic material containing iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3) with metal oxide A. Such calcination can be carried out at a temperature ranging from about 400 to about 550°C, typically for a time period of less than about 120 hours. For all calcination steps discussed herein, the calcination time is not particularly limited, and calcination is carried out as long as required for the desired surface area of ​​the material. The total time depends on factors such as the furnace used, flow conditions, and heat transfer, and can be determined by one of ordinary skill in the art using general knowledge. As demonstrated in the Examples section, both synthesis methods provide catalytic compositions, typically comprising a catalytic material containing iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3) dry-coated with metal oxide A, that achieve the benefits of the present invention. In an optional embodiment, metal oxide A is calcined prior to mixing with the catalytic material comprising iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO). Such calcination may be carried out at a temperature ranging from about 300 to about 1200°C, typically for a time period of less than about 120 hours.The mixing of the catalytic material containing iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3) with metal oxide A can be any form of physical mixing, typically a blend of the two solid forms, either manually or using automated means such as resonant acoustic mixing. Preferably, metal oxide A has a particle size, as measured by sieving, that is smaller than the granules of the catalytic material containing iron molybdate (Fe2(MoO)4)3) and molybdenum trioxide (MoO3). As demonstrated in the Examples section, the specific method used for blending is not particularly limited, and this is an advantage of the catalytic composition. When the catalytic composition contains an alkali metal, metal oxide A is preferably impregnated with the alkali metal. This is typically achieved by precipitating the alkali metal from a solution of a soluble alkali metal salt, typically an aqueous solution, in the presence of metal oxide A that has not undergone calcination. This can be accomplished, for example, by adding the solution dropwise to metal oxide A prior to the heating step within a range of about 80 to about 120°C. For uniform distribution of the alkali metal, the soluble alkali metal salt can be dissolved in a solvent, typically water, sufficient to fill the pores of the metal oxide A without overloading. Those skilled in the art can determine such an amount using general knowledge. The impregnated metal oxide A is then calcined at a temperature ranging from about 300 to about 1200°C, typically for a time period of less than about 120 hours. The alkali metal salt can be, for example, a hydroxide salt or a chloride salt.

[0021] The catalyst composition of the present invention may be incorporated into a molded or extruded catalyst. Accordingly, provided herein is a molded or extruded catalyst comprising the catalyst composition of the present invention. The catalyst composition may be molded into pellets, preferably ring-shaped pellets. Accordingly, provided herein are pellets, preferably ring-shaped pellets, comprising the catalyst composition of the present invention. The size of such pellets depends on the specific application. Preferably, the ring-shaped pellets have an outer diameter in the range of about 4.5 to about 5.5 mm. Preferably, the ring-shaped pellets have an inner diameter in the range of about 2.0 to about 3.7 mm. Preferably, the ring-shaped pellets have a height in the range of about 2.0 to about 5.5 mm. Pellets can be molded using standard means known to those skilled in the art, and the process may include the use of additives such as lubricants, i.e., graphite, and pore formers. Generally, such additives are removed during a subsequent heating step. However, for example, some lubricant may remain in the molded pellets in an amount of less than about 1% by weight. The pellet molding step is followed by a heating step. In the process for preparing the catalyst composition of the present invention, where there is a step iii) of calcining the mixture to provide the catalyst composition, the step of forming pellets is carried out before this step iii), so that the calcination step provides the necessary heat. The pellets suitably have a hardness-to-density ratio, typically in the axial direction, of greater than 9, typically greater than 10. The hardness-to-density ratio is calculated as hardness (kP) / density (g / cm 3 ). The pellets preferably have an axial hardness of at least about 7 kP, typically at least about 20 kP. The pellets typically have an axial hardness of up to about 40 kP. Hardness is measured axially on a Sotax MultiTest 50-FT WTDH 800N 100-240V / 50-60Hz or any equivalent instrument on ring-shaped pellets having an outer diameter of 5.0 mm, an inner diameter of 2.75 mm, and a height of 2.5 mm. The pellets also preferably have a maximum hardness of up to about 2.2 g / cm 3 , typically up to about 2.0 g / cm 3 , more typically about 1.9 g / cm 2 having a density of less than 。The pellets typically have a density of at least about 1.5 g / cm 3 Tablet density is calculated using the average mass and volume of 10 tablets at ambient temperature and pressure, e.g., 25°C and 1 atm. Volume dimensions can be measured, for example, using an optical microscope.

[0022] Typical processes for producing formaldehyde from methanol are known, for example, from WO 96 / 32189 and U.S. Pat. No. 2,504,402. A well-known process for producing formaldehyde is the Formox process offered by Johnson Matthey, as described, for example, in WO 2022 / 079434.

[0023] In the process for preparing formaldehyde from methanol, the reactor can be operated at an inlet pressure appropriate for the particular process and available plant equipment. Those skilled in the art will need to select the appropriate reactor pressure based on the plant and desired results. A typical process plant for producing formaldehyde using a catalyst material containing iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO) can operate at a reactor inlet pressure of approximately 0 barg. Barg refers to gauge pressure in bars, i.e., pressure above atmospheric pressure. Barg can be converted to absolute bar (bara) by adding the local atmospheric pressure in bars. Using the process of the present invention, the reactor inlet pressure can be at least 0.4 barg. The ability to increase the reactor inlet pressure without increasing or even reducing methyl formate losses is a particular advantage of the process of the present invention. In other words, because the present invention reduces methyl formate loss compared to prior art processes at the same pressure, prior art processes can be applied with the present invention and the pressure increased while still maintaining the same or better methyl formate loss and / or methyl formate loss. Thus, the reactor inlet pressure may preferably be at least about 0.4 barg, more preferably at least about 1.0 barg, even more preferably greater than about 1.5 barg, and even more preferably greater than about 3 barg. The reactor inlet pressure may be less than or equal to about 10 barg, or may be greater than about 10 barg.

[0024] The oxygen-containing gas may be any suitable gas stream. The oxygen concentration in the reactor is typically selected by the process designer according to the intended process. For example, the oxygen concentration may be selected so that the mixture of oxygen and the organic compound is not explosive. In a typical formaldehyde production process, the oxygen-containing gas is air. The oxygen-containing gas may be mixed with other components of the feed stream, such as methanol and recycle streams, either in the reactor, at the reactor inlet, or before the feed stream is fed through the reactor inlet.

[0025] The feed stream may contain methanol at a concentration of 1% to 20% by volume of the feed stream. The feed stream may contain 3% to 15% by volume, for example, about 6% to about 12% by volume of methanol.

[0026] In a typical process, the reaction product exiting the reactor containing a portion of the product formaldehyde is treated to remove a portion of the product formaldehyde from the formaldehyde reactor outlet stream. This results in a formaldehyde product stream containing the removed formaldehyde product and a treated stream containing some formaldehyde along with other by-products such as carbon monoxide, and typically unreacted methanol, water, and dimethyl ether. Other by-products may include nitrogen, for example, when the oxygen-containing gas used is air. A portion of the treated stream may be recycled to the reactor. In such cases, the feed stream to the reactor may contain dimethyl ether produced as a by-product in the reactor. It is known that adding dimethyl ether to the reactor tends to reduce the amount of dimethyl ether produced in the reaction. The feed stream may contain, for example, up to about 0.7% by volume of dimethyl ether. Typically, the feed stream may contain about 0.1 to about 0.6% by volume of dimethyl ether. Conversion of methanol to dimethyl ether is a known problem affecting the productivity of formaldehyde processes, especially when operating at high inlet pressures. The presence of water in the reactor feed stream can reduce the amount of dimethyl ether formed. Water may be added, as described in WO 2016 / 177999. Preferably, sufficient water is added to the feed stream to bring the amount of water in the feed stream to a value ranging from about 3.0 to about 15.0% by volume, preferably from about 3.5 to about 10.0% by volume water.

[0027] The reaction temperature of the reaction of methanol with an oxygen-containing gas in the vapor phase in a reactor is typically greater than about 250°C, usually between about 250°C and about 400°C. The reactor feed inlet temperature can typically range from about 60°C to about 220°C. The reaction temperature can vary along the length of the reactor bed. Typically, reactors are operated so that the temperature is greatest between the inlet and outlet sections of the reactor. The reaction temperature in different sections of the reactor can be influenced by the composition of the catalyst in the catalyst bed. Mixed catalyst beds can be used, in which catalysts can be mixed with inert materials or with catalysts of different compositions and activities to provide a desired activity profile across the catalyst bed. In particular, the catalyst composition of the present invention can be used in only a portion of the reactor. The reactor can contain a catalyst bed, such as a fixed-bed reactor. More commonly, the reactor contains multiple parallel catalyst beds, such as a tubular reactor, in which multiple tubes, each containing a catalyst bed, are surrounded by a heat transfer fluid. A tubular reactor can typically contain hundreds or thousands of such tubes. Preferably, the downstream third of the catalyst bed may contain the catalyst composition of the present invention. Alternatively, the downstream half of the catalyst bed may contain the catalyst composition of the present invention. The catalyst composition of the present invention may be used in the downstream portion of the catalyst bed where most of the methyl formate is formed. The catalyst composition of the present invention may be used throughout the catalyst bed or in the upstream portion of the catalyst bed. Using the catalyst composition of the present invention in only a portion of the catalyst bed may be particularly advantageous when the activity of the catalyst composition of the present invention differs from that of standard prior art catalysts.

[0028] The reaction temperature may be controlled by a heat transfer system. The reactor temperature may be varied over time. Typical catalysts tend to lose activity over their useful life. The reactor temperature may be varied to account for this loss of activity. [Example]

[0029] Example 1 Commercially available MgO (Sigma-Aldrich, 325 mesh) was calcined using a static oven at a ramp rate of 5°C / min, typically to 600 or 1000°C, and maintained at the target temperature for 2 hours. Amorphous methanol oxidation catalyst (Mo-Fe catalyst) containing iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO) was sieved to a particle size range of 250–355 μm, as described in Topics in Catalysis, Vol. 50, 2008, pp. 145–155. Mo-Fe catalyst (14.85 g) was added to the reaction pot, followed by calcined MgO (0.15 g). This aimed for a final product containing 99 wt% Mo-Fe catalyst and 1 wt% MgO. The reaction pot was then subjected to resonance acoustic mixing (RAM) for 5 minutes at 80 g force using a LabRAM II apparatus. The samples were then calcined at temperatures ranging from 400 to 500°C to obtain the final catalyst. Two catalyst compositions were prepared according to this process: 1a, which contained 1 wt. % MgO that had been previously calcined at 600°C. 1b, which contained 1 wt. % MgO that had been previously calcined at 1000°C.

[0030] As described in Topics in Catalysis, 50, 2008, pp. 145 to 155-C1, the methyl formate selectivity relative to the methanol conversion was evaluated for 1a and 1b together with a reference methanol oxidation catalyst containing iron molybdate (Fe(MoO)) and molybdenum trioxide (MoO).

[0031] Evaluations were conducted in a microreactor at 330 °C, 0.5 barg, and a total gas flow rate of 400 Nml / min. The concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0, 1.4, 0.2, 0.26, 4.06, 10.0, and 77.08 vol.%, respectively. The weight of C1 catalyst used in the microreactor was 0.1, 0.15, 0.2, and 0.25 g in separate experiments, which resulted in increasing levels of conversion, as shown in Figure 1. The weight of catalyst compositions 1a and 1b used in the microreactor tests was 0.2 g. Figure 1 shows that for 0.2 g of catalyst, methyl formate selectivity decreased, but methanol conversion did not decrease significantly. This effect can be extrapolated to higher catalyst loadings and methanol conversions.

[0032] Example 2 Three series of catalyst compositions were prepared to test the effect of different variables on the selectivity loss of methyl formate. The factors investigated consisted of MgO loading, the effect of adding Na to MgO, and the method of mixing the Mo-Fe catalyst with MgO (with or without added Na).

[0033] Variation of MgO loading on Mo-Fe catalysts and RAM mixing of components First, commercial MgO (Sigma-Aldrich, 325 mesh) was calcined using a static oven at a ramp rate of 5°C / min to 1000°C and held at the target temperature for 2 hours. The amorphous Mo-Fe catalyst was sieved to a particle size range of 250-355 μm. The final calcined catalyst compositions were prepared according to the same method described in Example 1. The following table shows the amounts of reactants used for each catalyst composition in this series:

[0034] [Table 1]

[0035] Variation of the loading of Na-impregnated MgO on Mo-Fe catalysts and RAM mixing of components First, commercial MgO (Sigma-Aldrich, 325 mesh) was calcined using a static oven at a ramp rate of 5°C / min to 1000°C and maintained at the target temperature for 2 hours. NaCl was then dissolved in enough demineralized water to fill the pores of the MgO without overfilling to ensure uniform distribution of the NaCl. The amount of solution required per gram of calcined MgO was 0.60 g / mL. 9.98 g of calcined MgO was weighed into a glass beaker. 0.05 g of NaCl was weighed into a separate beaker and dissolved in 6 mL of water. The NaCl solution was added dropwise to the calcined MgO and stirred to ensure good distribution. The resulting mixture was then dried in an oven at 105°C for approximately 16 hours.

[0036] The amorphous Mo-Fe catalyst was sieved to a particle size range of 250-355 μm. The final calcined catalyst composition containing the Fe-Mo catalyst and Na-impregnated MgO was prepared according to the same method as described in Example 1. The following table shows the amounts of reactants used for each sample in this series:

[0037] [Table 2]

[0038] Manual mixing of catalyst components Calcined MgO: Commercially available MgO (Sigma-Aldrich, 325 mesh) was calcined using a static oven at a ramp rate of 5°C / min to 1000°C and held at the target temperature for 2 hours.

[0039] Na-Impregnated MgO: A batch of calcined MgO, prepared as described above, was impregnated with NaCl to achieve 0.2 wt.% Na on the MgO. To do so, NaCl was dissolved in enough demineralized water to fill the pores of the MgO without overfilling to ensure uniform distribution of the NaCl. The amount of solution required per gram of calcined MgO was 0.60 g / mL. 9.98 g of calcined MgO was weighed into a glass beaker. 0.05 g of NaCl was weighed into a separate beaker and dissolved in 6 mL of water. The NaCl solution was added dropwise to the calcined MgO and stirred to ensure good distribution. The resulting mixture was then dried in an oven at 105°C for approximately 16 hours.

[0040] Mo-Fe catalyst: The batch was sieved to a particle size range of 250-355 μm.

[0041] 2i, 1 wt% MgO manual mix: The Mo-Fe catalyst (14.85 g) was weighed into a glass beaker and calcined MgO (0.15 g) was added, and the reaction mixture was then carefully stirred with a metal spatula for approximately 5 minutes.

[0042] The samples were then calcined at 400-550°C to obtain the final catalyst compositions.

[0043] 2j, manual mixing of 1 wt% MgO containing Na The Mo-Fe catalyst (14.85 g) was weighed into a glass beaker and calcined Na-impregnated MgO (0.15 g) was added, and the reaction mixture was then carefully stirred with a metal spatula for approximately 5 minutes.

[0044] The samples were then calcined at 400-550°C to obtain the final catalyst compositions.

[0045] Along with reference C1, 2a-j were evaluated for methyl formate selectivity % relative to methanol conversion %.

[0046] Evaluations were conducted in a microreactor at 330 °C, 0.5 barg, and a total gas flow rate of 400 Nml / min. The concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0, 1.4, 0.2, 0.26, 4.06, 10.0, and 77.08 vol.%, respectively. The weight of C1 catalyst used in the microreactor was 0.1, 0.15, 0.2, and 0.25 g in separate experiments, which resulted in increasing levels of conversion, as shown in Figure 2. The weight of catalysts 2a-j used in the microreactor tests was 0.2 g. Figure 2 shows that for the 0.2 g catalyst, methyl formate selectivity decreased, but methanol conversion did not decrease significantly. This effect can be extrapolated to higher catalyst loadings and methanol conversions. The catalyst preparation also proves versatile, as both RAM and hand-mixing provide catalysts that exhibit a similar decrease in methyl formate selectivity. Although the Na-containing catalyst exhibits reduced catalytic activity, by extrapolation, methyl formate selectivity is found to decrease even more at a given methanol conversion.

[0047] Example 3 Catalyst compositions were prepared according to the procedure described in Example 2. However, the Mo-Fe catalyst was calcined at 400-550°C before blending or mixing with the MgO or Na-impregnated MgO, and the final catalyst was not calcined. Catalyst materials having the following compositions were produced:

[0048] [Table 3]

[0049] Along with reference C1, 3a-l were evaluated for methyl formate selectivity % relative to methanol conversion %.

[0050] Evaluations were conducted in a microreactor at 330 °C, 0.5 barg, and a total gas flow rate of 400 Nml / min. The concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0, 1.4, 0.2, 0.26, 4.06, 10.0, and 77.08 vol.%, respectively. The weight of C1 catalyst used in the microreactor was 0.1, 0.15, 0.2, and 0.25 g in separate experiments, which resulted in increasing levels of conversion, as shown in Figure 3. The weight of catalyst 3a-1 used in the microreactor tests was 0.2 g. Figure 3 shows that for the 0.2 g catalyst, methyl formate selectivity decreased, but methanol conversion did not decrease significantly. This effect can be extrapolated to higher catalyst loadings and methanol conversions. The catalyst preparation also demonstrates versatility, as both RAM and hand mixing provide catalyst compositions that exhibit similar decreases in methyl formate selectivity. Again, the Na-containing catalyst exhibits reduced catalytic activity, but by extrapolation, methyl formate selectivity is found to decrease even more at a given methanol conversion.

[0051] Example 4 4a, 3wt% ZrO2 catalyst Commercially available ZrO (Alpha Aesar) was sieved to a particle size less than 53 μm and then calcined using a static oven at a ramp rate of 5°C / min to 1000°C and held at the target temperature for 2 hours.

[0052] The amorphous Mo-Fe catalyst was sieved to have a particle size in the range of 250 to 355 μm.

[0053] Amorphous Mo-Fe catalyst (14.7 g) was added to a reaction pot, followed by calcined ZrO (0.3 g). The reaction pot was then subjected to RAM at 80 g force for 5 minutes using a LabRAM II apparatus. The sample was then calcined to obtain the final catalyst composition.

[0054] 4b, 3 wt% ZrO2:CeO2 (50:50) catalyst A commercially available 50:50 mixture of CeO2:ZrO2 (Rhodia) was sieved to a particle size less than 53 μm and then calcined using a static oven at a ramp rate of 5°C / min to 1000°C and held at the target temperature for 2 hours.

[0055] The amorphous Mo-Fe catalyst was sieved to have a particle size in the range of 250 to 355 μm.

[0056] Amorphous Mo-Fe catalyst (14.7 g) was added to a reaction pot, followed by calcined CeO2:ZrO2 50:50 (0.3 g). The reaction pot was then subjected to RAM at 80 g force for 5 minutes using a LabRAM II apparatus. The sample was then calcined to obtain the final catalyst.

[0057] The % methyl formate selectivity relative to the % methanol conversion was evaluated for 4a and b along with reference C1.

[0058] Evaluations were conducted in a microreactor at 330 °C, 0.5 barg, and a total gas flow rate of 400 Nml / min. The concentrations of oxygen, methanol, methyl formate, dimethyl ether, formaldehyde, water, and nitrogen were 7.0, 1.4, 0.2, 0.26, 4.06, 10.0, and 77.08 vol.%, respectively. The weight of C1 catalyst used in the microreactor was 0.1, 0.15, 0.2, and 0.25 g in separate experiments, which resulted in increasing levels of conversion, as shown in Figure 4. The weight of catalysts 4a and 4b used in the microreactor tests was 0.2 g. Figure 4 shows that for the 0.2 g catalyst, methyl formate selectivity decreased, but methanol conversion increased. This effect can be extrapolated to higher catalyst loadings and methanol conversions.

[0059] Example 5 A catalyst containing 3 wt. % MgO was prepared according to the same method as described in Example 1. Before calcination, the catalyst composition was tableted to obtain ring-shaped catalyst table 5a. For tableting, single-layer pellets were prepared using a compaction simulator, and die filling was performed using a vibratory feeder. After calcination, the tablets had an outer diameter of 5.1 mm and an inner diameter of 2.75 mm. Conventional lubricants and pore formers were used. Reference catalyst C1 was also tableted and calcined to obtain tablets with an outer diameter of 5.0 mm and an inner diameter of 2.75 mm. The average mass and volume of each of the 10 tablets were used to calculate the density of the calcined tablets at room temperature and ambient pressure. The tablet wall thickness was measured using a microscope (Infinity 2 model). The hardness of the tablets in the axial direction, outer diameter, and height was tested using a Sotax hardness tester MT50-FT, Standard, TDH, 800 N, 100-240 V / 50-60 Hz. As can be seen from Figure 5, tablets containing the catalyst composition of the present invention have a lower density but a higher hardness, which is beneficial to the activity of the catalyst. The ability to achieve such a hardness-to-density ratio means that tablets can be prepared at a lower density with a specific hardness that can correspond to the hardness of conventional catalyst pellets, for example. This is a great advantage for the durability and stability of the catalyst pellets.

[0060] Example 6 Figure 6 shows a TEM image (shown in color and grayscale) of coated granules in a catalyst composition of the present invention containing 1 wt% MgO, prepared by the method described above for Sample 1b. The image shows the presence of a homogeneous coating of Mg on the surface of the granules of the Fe-Mo catalyst material. The surface coating is also evident from the higher Mg density at the edges of the granules in the image, combined with the fact that the blending method used to prepare the catalyst does not result in impregnation of the granules with Mg.

[0061] Figure 7 is a collection of EDS images (shown in color and grayscale) of coated granules in a catalyst composition of the present invention containing 1 wt. % Mg, prepared by the method described above for Sample 1b. Similar to Figure 5, this image shows the presence of a homogeneous coating of Mg on the surface of the granules of the Fe-Mo catalyst material. The presence of Fe, O, and Mo throughout the granule is also evident.

[0062] For TEM and EDS measurements, samples were ground between two glass slides and sprinkled onto a holey carbon-coated Cu TEM grid. Samples were examined in a JEM2800 (scanning) transmission electron microscope using the following instrument conditions: voltage (kV) 200, C2 aperture (µm) 70 and 40. Dark-field (Z-contrast) imaging in scanning mode using an off-axis annular detector was used. SE signals were acquired simultaneously with other TEM images, providing topological information of the sample.

Claims

1. 1. A catalyst composition comprising: i) Iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ a catalyst material comprising ii) a metal oxide A which is an alkaline earth metal oxide or zirconium oxide or a combination of zirconium oxide and cerium oxide; A catalyst composition comprising:

2. 2. The catalytic composition of claim 1, wherein said metal oxide A is an alkaline earth metal oxide.

3. 3. The catalytic composition of claim 2, wherein said metal oxide A is magnesium oxide.

4. 2. The catalyst composition of claim 1, wherein the metal oxide A is zirconium oxide or a combination of zirconium oxide and cerium oxide.

5. The iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ 5. The catalyst composition of claim 1, wherein the catalyst material comprising:

6. The iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ 6. The catalyst composition of claim 1, comprising a physical blend of said metal oxide A with a catalytic material comprising:

7. At least a part of the metal oxide A is the iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ 7. The catalyst composition of claim 5 or 6, wherein the catalyst composition forms a coating around granules of catalyst material comprising:

8. i) The iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ granules of catalytic material comprising ii) Metal oxide A; Including, The catalyst composition is the iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ a physical blend of a catalytic material comprising the metal oxide A and the metal oxide B; At least a part of the metal oxide A is the iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ 8. The catalyst composition of claim 5, wherein the catalyst composition comprises a granule of catalyst material comprising:

9. 9. The catalyst composition of any one of claims 1 to 8, wherein said metal oxide A is present in an amount of up to about 15 wt % of the total weight of said catalyst composition.

10. The catalyst composition according to any one of claims 1 to 9, further comprising an alkali metal.

11. 11. The catalyst composition according to claim 1, wherein said metal oxide A is impregnated with said alkali metal.

12. 12. The catalyst composition of claim 10 or 11, wherein the alkali metal is present in an amount of about 5% by weight or less of the metal oxide A.

13. A pellet comprising the catalyst composition of any one of claims 1 to 12.

14. 14. The pellet of claim 13 having a hardness to density ratio greater than about 9.

15. A process for preparing the catalyst composition of any one of claims 1 to 12, comprising: i) calcining metal oxide A to provide calcined metal oxide A; ii) The calcined metal oxide A is converted into iron molybdate (Fe ２ (MoO ４ ) ３ ) and molybdenum trioxide (MoO ３ ) with a catalyst material comprising: iii) calcining the mixture to provide the catalyst composition; The process includes:

16. A process according to claim 15 for preparing a catalyst composition according to any one of claims 10 to 12, comprising: ii) impregnating the metal oxide A with the alkali metal using a salt of the alkali metal before calcining the metal oxide A to provide an impregnated metal oxide A. The process includes:

17. A process for producing formaldehyde from methanol, comprising the steps of: supplying a feed stream comprising the methanol and an oxygen-containing gas to a reactor; and reacting the methanol in the gas phase with the oxygen-containing gas in the presence of the catalyst composition of any one of claims 1 to 12 or the pellets of claim 13 or 14 in the reactor. The process includes:

18. 18. The process of claim 17, wherein the reactor comprises at least one reactor tube, each tube equipped with a catalyst bed, the catalyst bed in the lower part of the tube comprising the catalyst composition of any one of claims 1 to 12 or the pellets of claim 13 or claim 14.

19. Use of the catalyst composition of any one of claims 1 to 13 or the pellets of claim 13 or claim 14 to reduce losses of methyl formate in a process for producing formaldehyde from methanol.

20. 20. The use of claim 19, comprising the steps of: feeding a feed stream comprising the methanol and an oxygen-containing gas to a reactor; reacting the methanol in the vapor phase with the oxygen-containing gas in the reactor in the presence of the catalyst composition; and recovering a formaldehyde reactor effluent stream from the reactor, wherein the formaldehyde reactor effluent stream comprises formaldehyde and methyl formate.

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