John W. Tierney

Hybrid zirconia catalysts for conversion of Fischer–Tropsch waxy products to transportation fuels

Conversion of long-chain normal paraffins found in Fischer–Tropsch products to high-quality transportation fuels, especially middle range products, was investigated using model hydrocarbons (n-C24 and n-C36) and a Fischer–Tropsch wax over modified zirconia catalysts. Most work was carried out using n-C24 as a representative reactant. With Pt-promoted tungstated zirconia (Pt/WO3/ZrO2, 0.5 wt.% Pt and 12.5 wt.% W) used as a base, addition of sulfated zirconia (SO4/ZrO2), tungstated zirconia (WO3/ZrO2) or certain zeolites increased its reactivity and selectivity at 200 °C to middle range products such as kerosene and diesel fuel. The effect of improving the performance of Pt/WO3/ZrO2 by adding the zeolite, mordenite, was studied in detail; an optimal mixing ratio exists for maximum conversion of n-C24 under certain reaction conditions. The hybrid catalysts are physical mixtures of compounds with different functions. Hybrid catalysts based on Pt/WO3/ZrO2 provide a promising way to obtain higher catalytic activity and higher selectivity for desired transportation fuels from Fischer–Tropsch products.

Kinetics of two-step methanol synthesis in the slurry phase

Abstract The carbonylation of methanol using potassium methoxide catalyst and hydrogenolysis of methyl formate using a copper-chromite catalyst (39% Cu; 37% Cr and 3% Mn) were studied in the temperature ranges of 60–110°C and 100–140°C and pressure ranges of 25–65 and 30–60 bar respectively in a mechanically agitated reactor. Kinetic rate expressions are presented for both reactions. The carbonylation reaction was found to be rapid and limited by equilibrium at the conditions studied. The apparent activation energy for the carbonylation was found to be 67.7 ± 1.5 kJ/mol. CO 2 reacts with the potassium methoxide catalyst and stops the reaction. The hydrogenolysis reaction was found to be slow at the studied conditions with an apparent activation energy of 69.8 ± 2.0 kJ/mol. CO inhibited the hydrogenolysis reaction over the copper-chromite catalyst used. CO 2 poisoned the copper-chromite catalyst. A Langmuir-Hinshelwood type rate model was used to fit the experimental data. A brief discussion of the feasibility of the two-step methanol synthesis in a single stage reactor is given. The data would be useful for evaluating the possibility of synthesizing methanol from H 2 and CO using these reactions either in two separate reactors or concurrently in one reactor.

Anion-modified zirconia: effect of metal promotion and hydrogen reduction on hydroisomerization of n-hexadecane and Fischer–Tropsch waxes

Abstract The effect of metal promoters on the activity and selectivity of tungstated zirconia (8 wt.% W) for n -hexadecane isomerization in a trickle bed continuous reactor is studied by using different metals (Pt, Ni, and Pd) and, in one case, by varying metal loading. Platinum is found to be the best promoter. The effect of hydrogen reduction is investigated using platinum-promoted tungstated zirconia catalysts (Pt/WO 3 /ZrO 2 , 0.5 wt.% Pt and 6.5 wt.% W). Pretreatment at temperatures between 300 and 400°C for 3 h in hydrogen is found to be slightly beneficial for achieving high yields of isohexadecane. A platinum promoted sulfated zirconia (Pt/SO 4 /ZrO 2 ) is compared with a Pt/WO 3 /ZrO 2 catalyst for the hydroisomerization of n -hexadecane in the same reactor at the same n -hexadecane conversion. The former is a good cracking catalyst and the latter is suitable for use as a hydroisomerization catalyst. In a 27-ml microautoclave reactor, studies of the hydroisomerization and hydrocracking of two Fischer–Tropsch (F–T) wax samples are carried out. Severe cracking can be effectively suppressed using a Pt/WO 3 /ZrO 2 catalyst so as to obtain branched isomers in the diesel fuel or lube-base oil range.

Methanol synthesis via methylformate in a slurry reactor

Abstract The synthesis of methanol from CO and H 2 using a reaction sequence in which methanol is first carbonylated to methylformate and then hydrogenated to methanol was studied. The reaction occurred concurrently in a single mechanically agitated slurry reactor using the usual homogeneous formate synthesis catalyst (CH 3 OK) and a heterogeneous catalyst (copper-chromite) at temperatures of 140 to 180°C and pressures of 38 to 62 bar. The concurrent operation is not a simple summation of the two individual reactions. It is likely that the CH 3 OK is adsorbed on the copper-chromite. The rate of formation of methanol is significantly higher than predicted from the individual reactions and the deleterious effect of CO 2 on the CH 3 OK catalyzed carbonylation of methanol and on the hydrogenolysis of methyl formate is reversible. The carbonylation reaction is in equilibrium under the conditions studied. A progressive reduction in reaction rate with time was found and is attributed to the effect of CO on the hydrogenolysis catalyst. Comparisons are made of the concurrent methanol synthesis in a slurry reactor with alternative methods of methanol synthesis.

Alkali compounds and copper chromite as low-temperature slurry phase methanol catalysts

Abstract A slurry phase synthesis of methanol via methyl formate in a single reactor at low temperatures (100–180°C) is discussed. Mixed catalyst systems comprised of alkali compounds (such as the hydroxide, formate, carbonate and bicarbonate) or alkali earth compounds and copper chromite as well as copper chromites impregnated with alkali have been found to be active for methanol synthesis. All the starting alkali compounds are converted by copper chromite to the corresponding alkali methoxide in solution. At low alkali methoxide loadings charged to the reactor, methanol formation increases with increasing methyl formate concentration while at higher loadings decreased rates of methanol synthesis are found, possibly due to blockage of hydrogenolysis sites on the copper chromite surface.

Liquefaction of coal under mild conditions: Catalysis by strong acids, iodine and their combination

The concept of using an acid coal depolymerization catalyst with a balancing hydrogenation/ hydrogenolysis function to prevent retrogressive reactions forms the basis of this work. A catalytic system based on combining the superacid CF3SO3H (triflic acid) with iodine was examined in coal liquefaction under mild reaction conditions. This system was shown to be effective for three types of coal. For example, CF3SO3H (25 wt%)I2(0.5 wt%) in tetralin as solvent gave 79 ± 2% conversion of a Wyodak coal to 54% asphaltenes and 37% oils after 2 h at 300 °C under 6.8 MPa of H2 pressure using a batch microreactor. Under identical conditions the acid alone gave only 46% conversion, while iodine alone gave 58%. The combined catalytic system also performed well with toluene as solvent; with the higher rank Illinois no. 6 and Pittsburgh seam coals, best results were obtained with 10 wt% acid0.5 wt% I2. Weaker acids such as p-toluenesulphonic acid and sulphuric acid (98%) were less effective than triflic acid in this catalytic coal conversion. From the dependence of product selectivity on the catalytic system and reaction conditions, and from elemental analyses of liquids and residues and 1H and 13C n.m.r. measurements, it is concluded that the main function of the acid is to enhance coal depolymerization to asphaltenes while the (major) role of iodine in the combined catalytic system is to hydrogenate and hydrocrack the asphaltenes to oils. It is important to note that each catalyst alone, triflic acid as well as iodine, can utilize molecular H2 to liquefy coal. Finally, the combined catalytic system removed more than 50% of the nitrogen and over 90% of the sulphur of the original coal, as shown for Illinois no. 6 and Pittsburgh seam samples.

Evaluation of a delayed coking process by 1H and 13C n.m.r. spectroscopy: 2. Detailed interpretation of liquid n.m.r. spectra

Abstract The 1H and 13C nuclear magnetic resonance (n.m.r.) spectra of a delayed coking feedstock and products, presented in a previous paper, are analysed here in detail by matching results from inspection of both nuclei. The conventional spectra of whole samples are used in combination with elemental analysis data, and substantial agreement is obtained. Differences are explored to yield valuable information. Interpretation of some band assignments is modified to account for new results. This approach results in a detailed quantitative estimation of a few key structures that contain the main functional groups that characterize these petroleum fractions.

Liquefaction of lignocellulosic and plastic wastes with coal using carbon monoxide and aqueous alkali

Abstract An investigation has been made of the coprocessing of paper and other lignocellulosic wastes, and also of waste plastics, with coal via the COsteam route—treatment with CO, water and alkali at elevated pressures. The liquefaction of lignocellulosic and polymeric wastes was studied separately and then with the addition of coal. High conversion of lignocellulosic wastes could be achieved at 400°C. Polypropylene and polystyrene are completely converted to liquids and gases at 400°C; however, the conversion of high density polyethylene requires a temperature of 445°C. Coprocessing of Wyodak coal and lignocellulosics at 400°C did not change the yields or product quality compared with the liquefaction of Wyodak coal or lignocellulosics alone. However, the coprocessing of Wyodak coal and polypropylene at 400°C resulted in a decrease in coal conversion accompanied by an increase in the asphaltene fraction from coal. It is possible that the combination of free radicals from the polymer with coal fragments is responsible for this result. However, coliquefaction of Wyodak coal with less than 30% high density polyethylene at 445°C resulted in good coal conversion (85–90%) and did not increase the asphaltene yield from coal.

CALCULATION METHODS FOR DISTILLATION SYSTEMS WITH REACTION

Abstract A calculation procedure is presented for the solution of the equations describing a distillation process in which reaction is taking place. A mathematical model based on matrix notation is used to formulate the system equations. It is assumed that the distillation process can be represented by a system of interconnected stages, each of which is well mixed with the vapor and liquid phases in equilibrium. Reaction may take place in the vapor phase, liquid phase, or both. The equations describing this system are first presented. Then a calculation sequence and a correction algorithm are derived for the case in which the liquid and vapor solutions are ideal—that is, the equilibrium ratios are functions only of temperature and pressure and not of composition. The calculation sequence uses as variables of iteration the vectors of vapor flow rate, temperature, and reaction extents. A derivative correction method is used, and equations for the calculation of the Jacobian matrix are derived. The applicati...

Evaluation of a delayed coking process by 1H and 13C n.m.r. spectroscopy: 1. Material balances

Abstract The use of 1 H and 13 C nuclear magnetic resonance (n.m.r.) spectroscopy to evaluate the performance of a delayed coking process is presented in a series of papers, of which this is the first. A meaningful analysis requires an accurate balance, which in turn requires analysis of the various types of atoms in the feed and in all products, including solid coke, as well as the amounts of each. Product yields were determined in a delayed coking pilot plant. Complete n.m.r. ( 1 H and 13 C) characterization of feed and all delayed coking products, using a consistent classification, was combined with pilot plant data to obtain the total distribution of carbon and proton atoms in the delayed coking process. Changes in carbon and hydrogen distributions (products versus feedstock) reveal the nature of the thermal cracking reactions involved; the main change is a substantial increase in the number of aromatic and paraffinic carbons at the expense of naphthenic carbons.