USE OF PENDULUM VISCOMETER IN FLUID-BED REACTION

Abstract: Method for using a pendulum viscometer having damped torsional oscillations, in a laboratory catalytic fluid-bed reactor, to monitor a propensity to stick which is exhibited by certain supported catalysts. A fluid-bed of such catalysts has been found to become suddenly more stikky just before a point at which a change in pressure drop across the fluid-bed can be measured due to a process "upset". At this point ("the inversion point"), the upset is usually irremediable. The method includes correlating data on catalyst stickiness from a laboratory reactor operating at atmospheric pressure, with an expected level of catalyst stickiness in a commercial reactor operating at elevated pressure. A pendulum viscometer and related auxiliary apparatus is disclosed for magnetically and electrically measuring and recording the rate at which the pendulum's torsional oscillations are damped. Frequent measurements are made during normal operation of the fluid-bed to determine its stickiness (as evidenced by the rate at which the pendulum's torsional oscillations are damped) relative to the stickiness at the inversion point. Operation of the fluid-bed under conditions for which measured rates of damping are predeterminedly lower than the rate near the inversion point, assures operation of the fluid-bed reactor at maximum efficiency.

Description: USE OF PENDULUM VISCOMETER IN FLUID - BED REACTION BACKGROUND OF THE INVENTION The commercial advantage of the fluid-bed reactor is the ability of a fluidized-solid bed to approach isothermal conditions. This makes it possible to control the temperature closely, which in turn permits close control of the process. Though there are fluid-bed processes in which no reaction takes place, this invention is concerned only with commercial processes where a chemical reaction occurs at elevated temperature and pressure, which processes we have found, are unexpectedly correlatable in operation with a laboratory fluid-bed process operating at ambient pressure. More particularly, this invention is related to those processes using chemical reactions in fluid-bed catalysts which, we have also found, display a peculiar phenomenon best described as "tackiness" or "stickiness" which is not necessarily viscosity, as conventionally defined. Stickiness may be defined as the degree of particle-to-particle agglomeration, viscosity or resistance to movement or separation of constituent particles. Stickiness of a supported catalyst is dependent upon the pressure and temperature of the catalytic reaction, the adsorptive quality of the catalyst, the amount and distribution of active ingredient on the surface, the number of active sites available on the catalyst and the manner and degree of their utilization, and the quantity and physico-chemical properties of the reactants and reaction products in the fluid-bed. It will be appreciated that fluid-bed catalysts, such as are used in commercial reactors in chemical processes, consist essentially of an attrition- resistant, usually porous catalyst support on which is deposited one or more essential catalytic ingredients. A typical catalyst support is silica, kieselguhr, fuller's earth, pumice, and alumina, the last named being generally preferred because of its superior resistance to attrition, its ability to fluidizε and especially because it can be prepared with a desired surface area, and in a preselected ratio of particle sizes. Except for a change in color and surface area, depositing a desirable catalytic ingredient on the catalyst support does not substantially change the physical characteristics of the catalyst support, which closely resembles fine sand. In the normal course of a conventional start-up of a fluid-bed reactor, the fluid-bed catalyst gives no indication that it might undergo a change in "consistency", however this may be defined. But at elevated temperatures above about 100 C but below a temperature deleterious to the catalyst, particularly while the catalyst is catalyzing a reaction between feed components fed to the reactor, primary particles of some catalysts exhibit a proclivity to stick to one and another, thus displaying an overall change of fluid-bed consistency within the reactor. Catalysts which exhibit such a tendency include catalyst supports on which deposited the "soft" elements of Groups I, V, VI and VTH of the Periodic Table, compounds thereof. Most susceptible to a change in consistency are suppor catalysts on which are deposited compounds of copper, iron, bismuth, antimony the like, and which additionally may be promoted by the rare earth elements elements of Groups II, IV, and VII. Numerous chemical processes utiliz supported catalysts in a fluid-bed reaction are listed in the chapter entit "Fluidization" in Encyclopedia of Chemical Technology, Kirk-Othmer, Vol. 9, p 4 404, 2d Edition, Interscience Publishers, John Wiley & Sons, Inc. (1966). Many these catalysts are stickiness-prone during operation of the fluid-bed reac containing the catalyst. In specific processes listed in Kirk-Othmer (supra), such as ammoxidation of propylene to make acrylonitrile, the oxidation of propylene make acrolein, the oxyhydrochlorination of lower alkanes and alkenes having fro to 4 carbon atoms, and particularly methane to make carbon tetrachlori chloroform, etc., and the oxyhydrochlorination of ethylene to make 1,2-dichlo ethane (referred to as "EDC"), close control of these reactors is conventiona exercised by monitoring flow rates and temperatures of feed components, t pressure drop and temperature profile in the fluid-bed, reactor effluent analys heat duty of condensers, and the like. To obtain a good indication of what is wid believed to be the precise condition of an operating fluid bed, it is conventional monitor the bed height, corresponding bed density and pressure drop continuou across the bed, and to record an hourly (or half-hourly) moving average bed heig bed density and pressure drop. With due experience, by correlating bed height a pressure drop with efficiency, one may continually estimate efficiency of t overall reaction. By "efficiency" we refer to conversion of one or more fe components to desirable products at minimum cost. Desired operating conditio for a reactor (referred to in the plant as "normal optimum" operating conditio are those which provide maximum conversion of one or more feed components desirable products at minimum cost. However, despite frequent pressure drop a bed height measurements derived from just-elapsed conditions, the estimate efficency is relatively long term, and of no value to predict an impending proce "upset", whatever its cause. There is no direct correlation between bed height a the inversion point for the bed. Moreover, especially in a large operating fluid-b reactor, any warning related to a process upset attributable to a dangerous chan in bed height or a change in pressure drop is usually measured much too late correct the conditions which gave rise to the process upset. The importance of time will be more readily recognized when it realized that a large fluid-bed reactor, operating at desired operating conditio has little latitude in acceptable process conditions. Moreover, in an operating fluid-bed having a quantum of stickiness, typical for a particular supported catalyst, we have found that a process upset can change the stickiness quite suddenly, long before an alarming change in pressure drop is measured. When the change in pressure drop is registered, even drastic changes in process conditions fail to restore the fluid-bed to its pre-upset operating stability. Very soon there is no alternative but to shut the reactor down. Stated differently, we have found that a process upset which causes a sudden change in stickiness of a fluid-bed operating at desired conditions, presages a process "point-of-no-return" or the "inversion point" for the fluid-bed, without immediately and significantly altering the pressure drop across the reactor. If one waits for the alarm to be set off by a sudden rise in pressure drop, or sudden collapse of the bed, it is too late. The reactor is soon shut down. It will now be evident that, in an operating commercial fluid-bed reactor using a supported catalyst having a proclivity to increase in stickiness as conversion of reaetants to a desired product improves, the risks attendant operation of the reactor at peak efficiency, near the inversion point of the fluid- bed, are too great. As a result, such a reactor is operated well short of peak efficiency with concomitant higher costs for feed components and operation of the recovery and purification systems. Pressure drop across the fluid-bed, the height of the fluid-bed, and the composition of the effluent, may all be monitored to control overall efficiency. If the fluid-bed is upset by process conditions which place the fluid-bed beyond the inversion point, the reactor is soon shut down. Though it is self-evident that the inversion point of a fluid-bed may be determined by running the bed at conditions from which there is no recovery, there is no reliable way of estimating when that inversion point may be reached under different process conditions with a particular catalyst, or with a different catalyst at the same process conditions. Measurement of changes in pressure drop by itself, is not generally correlatable with changes in stickiness. In some processes, for example in the oxyhydrochlorination of ethylene to produce EDC, pressure drop is actually found to decrease across the bed while the stickiness increases. Of course, once the inversion point is exceeded, the pressure drop will increase until the bed solidifies. There is no reason to expect that a supported catalyst should exhibit a proclivity to increase in stickiness as conversion of reaetants to desired product improves, or that the inversion point of a fluid-bed is immediately preceded by a sudden rise in stickiness, but it is, and the process of this invention is based on this finding. It has been suggested to measure a "pseudoviscosity" or stickiness which might be a fundamental eorrelant of slugging, good fluidity or other characteristics (see Matheson, G.C., Herbst, W. A. and Holt, P.H., Inc Eng. C 41, 1099 (1949)). It has not been suggested that by frequently monitoring relative pseudo-viscosity, stickiness, tackiness or consistency (all of which t are hereafter referred to simply as "viscosity", for brevity) of an operating fl bed in which a- chemical reaction takes place, the data might be used to maxi efficiency of the reaction; nor that a sudden rise in "viscosity", relative to viscosity at usual operating conditions, might signal a danger-point requi immediate attention. Neither has it been suggested that the viscosity charact ties of supported catalyst in a laboratory fluid-bed reactor operating atmospheric pressure, may be correlateable with those of a commercial or p fluid bed reactor operating at elevated pressure. Recognizing that a fluid-bed displays "viscosity", a pendulum visco ter having damped torsional oscillation has been used to make measurements w are empirically correlatable to obtain a rate of damping (see "Viscometers Ha Damped Torsional Oscillation", by Ashwin, B. S., Hagyard, T., et al J. Scien Instruments, 37^ p 480-485, December 1960). However, the referenc unconcerned with a reactor and does not suggest that flow rates are relati insignificant in comparison with the reaction conditions, or change in particle due to agglomeration induced by changes in reaction conditions. It is known reliable rates of damping cannot be obtained with vibrating-reed type viscomet or viscometers having quite small clearances, as in the capillary flow and concentric cylinder type, all of which are unsuited for the purpose. Simil powered viscometers in which the power to maintain a predetermined rotatio measured, are unsuited in a fluid-bed reactor because there is too much disturb of the particles in the immediate vicinity of the viscometer. It is essential that rate of damping be measured reliably and reprodueibly, and to our knowledge, can only be done with a pendulum viscometer which uses relatively low rotati velocity, and which does not appreciably disturb the state of the fluid bed in immediate vicinity of the viscometer. SUMMARY OF THE INVENTION It has been discovered that a relationship exists between the visco of an operating fluid-bed near its inversion point (which viscosity is referre hereinafter as "peak viscosity", for brevity), and its viscosity at desired opera conditions at which a reactor is usually run (hence referred to herein as "u viscosity"), a change in which relationship may be used to signal a process u requiring immediate correction. " B It is therefore a general object of this invention to provide a method for obtaining desired operation of a fluid-bed reactor provided with a pendulum viscometer, and means to provide the pendulum with a preselected initial angular displacement, comprising : (a) charging said reactor with a supported catalyst in the presence of which a chemical reaction occurs which increases stickiness of said catalyst as conversion to desired products improves, (b) measuring a peak rate of damping of a predetermined torsional oscillation of said pendulum during operation of said fluid-bed at or near its inversion point, (c) measuring a usual rate of damping of said predetermined torsional oscillation of said pendulum during desired operating conditions, (d) obtaining a quantitative difference between said usual rate and said peak rate of damping, and (e) adjusting said process conditions to operate said reactor while maintaining approximately said quantitative difference. By "desired operating conditions" we refer to the most preferred operation of the reactor, often referred to as the optimum normal operating conditions, at which maximum conversion to desired products is obtained at minimum cost. It has also been discovered that, though operating at ambient pressure, a laboratory fluid-bed reactor equipped with a torsional pendulum and related auxiliary means for measuring and recording the rate of damping of the pendulum, may be used to reproduce the effects of the viscosity variations in the fluid-bed of a pressurized commercial reactor. It is therefore a general object of this invention to provide a laboratory apparatus for measuring the relative viscosity of a normally operating fluid-bed of supported catalyst with a pendulum viscometer having damped torsional oscillations comprising, means for creating a fluctuating electrical potential proportional to the angular displacement of the pendulum during each successive oscillation, means for rectifying said potential to produce a unidirectional potential having amplitudes proportional to said displacement, means for recording the output of said rectifying means, and means for recording the slope of said output. BRIEF DESCRIPTION OF THE DRAWINGS The invention in its several aspects, including other objects, features and advantages not above mentioned, will be more fully understood by now referring to the following detailed description of a preferred embodiment thereof, reference for this purpose being had to the accompanying drawing, in which: Figure 1 is a graphical simulation of the effect of a typical process upset in the oxyhydrochlorination of ethylene to EDC in a fluid-bed reactor, as evidenced by measurements of the ratio of feed components, particularly HC1:C 2 H 4 , bed height and corresponding bed density, all plotted as a function of time. OMPI Figure 2 is a schematic illustration of a laboratory fluid-bed react which a catalytic reaction is carried out. The reactor is fitted with a pend viscometer and is provided with related auxiliary measuring means for meas and recording viscosity of the fluid-bed during operation. . Figure 3 is a reproduction of a representative strip chart graphi illustrating a fluctuating output signal o ' f diminishing amplitude. Figure 4 is a semilog plot graphically illustrating successively dimi ing peak amplitudes corresponding to damped torsional oscillations as a functio time. Figure 5 is a plot graphically illustrating the rate of damping with t and the recovery of the fluid-bed from a process upset near the "inversion po but before a sharp pressure drop across the bed could be measured. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTI The apparatus of this invention is a laboratory fluid-bed reactor includes related auxiliary equipment to measure and record the visc characteristics of an operating fluid-bed. The pressure within the reacto essentially atmospheric. By "viscosity" we particularly refer to a character stickiness peculiar to certain supported catalysts which have deposited thereo least one essential catalytic ingredient consisting essentially of at least element, or an inorganic compound of an element, selected from Groups I B, III B and VI of the Periodic Table optionally combined with a promoter selected f the group consisting of elements and compounds of elements of Groups π, VQ, Vm. The catalytic ingredients of Groups I B, III B, V A and VI B are gener referred to as being "soft" because of their propensity to imbue a catalyst sup on which they are deposited, with a peculiar stickiness, referred to herei "viscosity". This viscosity increases progressively as the efficiency of a fluid of the supported catalyst approaches theoretical maximum for selected opera conditions. Specific active ingredients which display this progressive increas viscosity of a fluid-bed approaching optimum operating conditions, are compounds of copper, silver, bismuth, phosphorus, antimony, and uranium. apparatus may be used to measure the relative viscosity characteristics of single fluent material, or a mixture of materials, but as will presently be appar has particular utility for the measurement of viscosity characteristics of a fl bed while in operation. The method of this invention is useful to correlate the operation pressurized commercial or "plant" reactor, with an unpressurized labora _Λ3 reactor in which the process conditions of the plant reactor are simulated for feed ratios, contact time and temperature, but not for pressure. The laboratory reactor is operated concurrently with the plant reactor, simulating the plant reactor's operating conditions, but ignoring pressure. Any change in process conditions in the plant reactor is simulated in the laboratory reactor, where the effect upon viscosity is quickly evidenced as a change in the value of the decay constant before it is evidenced as a change in pressure drop, bed height or bed density, and before an effluent analysis from the plant reactor would indicate that a process upset has occurred. The necessary process adjustments are made to return the laboratory reactor to normal operation, near the optimum, and the appropriate analogous process adjustments are then made in the plant reactor though it (the plant reactor) provides no evidence that such changes are necessary. Thus, the effects of the process upset are minimized, and desired reactor operating conditions are maintained. The method of this invention is also useful to select the most desirable catalyst from a number of catalysts with slightly varying specifications, or even from several batches of purportedly identical catalysts, by performance testing them with the fluid-bed viscometer of this invention. On the basis of performance, one can then select the catalyst which produces highest yields, yet displays- the least sensitivity to process upsets. It will be appreciated that such testing by actual performance, will forseeably include the testing from time to time, of "used" catalyst, that is catalyst still in use in the plant reactor, to determine whether its sensitivity and/or its efficiency has been impaired. A preferred embodiment of the method of this invention will be described as it applies to the operation of a catalytic fluid-bed process in which ethylene is reacted with oxygen and hydrogen chloride in the presence of a copper chloride supported catalyst, to produce 1,2-dichloroethane ("EDC"). In this oxyhydrochlorination process, the catalyst is preferably cupric chloride supported on an attrition resistant catalyst support such as silica, kieselguhr, clay and alumina, alumina being preferred. The process is described in detail in U.S.Patent No. 3,488,398 the disclosure of which is incorporated by reference thereto as if fully set forth herein. The overall reaction for converting ethylene to 1,2-dichloroethane can be written empirically as follows: 2 C 2 H 4 + O 2 + 4 HC1 -→ 2 CH 2 C1CH 2 C1 + 2 H 2 O During the reaction some C«H , is converted to higher chloride containing materials and some is oxidized to CO and CO 2 , so it is desirable to use a slight excess of C„H 4 and O 2 over stoichiometric. Thus, for every two moles of HC1, from a 1.02 to about 1.2 moles of C ^ H., and from about 0.55 to about 0.9 mole of O„ preferably fed into the reactor to maximize utilization of HC1. The most prefe molar ratio of ethylene, HC1 and oxygen is 1: 1.9: 0.8. Preheated feed compon are contacted with the catalyst after it is fluidized and maintained a temperature in the range from about 210 C to about 240 C, in a plant rea pressurized in the range from about 10 to 100 psig. It is essential that a minimum of excess HC1 be fed to the reactor, and that the maximum conversio ethylene be obtained, both from the standpoint of effective use of the reaetant well as from the standpoint of minimizing the corrosive effects and purifica problems in the recovery system. The catalyst is prepared by impregna microspheroidal gel alumina with a solution of copper ehloride,and drying it so the amount of copper salt on the support is in -the range .from about 2.0 to a 12% by weight copper. In a typical operation of the plant reactor, the ratio of HC1 to ethyl is monitored, along with the bed height and the bed density. It is desirabl maintain each within a narrow range in which operation of the reactor is know be safe. A process upset is evidenced when the bed height increases (say) bey its preferred prescribed boundary, and the bed density decreases correspondin To mitigate the effect of a mushrooming process upset, the ratio of HCl:ethylen immediately changed (decreased), by increasing the flow of C-H., but overcom sated to . ensure that both the bed height and density revert to values wi prescribed operating limits. The overcompensation, and subsequent compensa attempts to return the bed to a stable, safe and cost-effective operating condit may be made over several operating shifts and a period of days during mos which period the reactor is operating at process conditions which may be safe far from the desired operating conditions. Referring now to Fig. 1 there is shown a graph for a typical upset large plant reactor, in which graph is plotted (a) ratio of HC1 : C„H 4 (Curve A); bed height, h» (Curve B); and, (c) bed density, p » (Curve C); all as a functio time. Operating limits for each are indicated on the graph with subscripts "m and "min." Referring first to Curve A, the ratio 2 is the upper (stoichiomet limit at which operation for any substantial length of time will result in excee the inversion point. At the lower limit of 1.6, excessive use of ethylene res with incidental problems in recovery and purification. The most preferred u operating ratio for the EDC process is about 1.9, the precise ratio being affec by the supported catalyst used, the variations in concentration of compon which make-up the feed stream, the actual geometry of the fluid-bed reactor, and other physical considerations. Referring now to Curve B, the bed height may vary within relatively narrow limits, about +20% from the usual operating bed height at the usual operating ratio (1.9) of HC1/C-H . . As shown in Curve B, a bed usually operating at a height of 31 ft may increase in height to about 37 ft during a process upset, and then decrease to about 31 ft after a correction in ratio is made. Referring to Curve C, the bed density during operation may vary within minimum and maximum 3 limits from about 28 lb/ft , marked P - . on the right hand side of Fig. 1, to about 40 lb/ft . During a process upset, the bed density may vary about +20% from the usual operating density. A bed condition where maximum bed density and maximum pressure drop are simultaneously exceeded indicates that the inversion point (not shown in this Figure) has been reached. Essentially parallel lines, for each of the variables being plotted, near the beginning of the time period indicates stable operation of the reactor at desired operating conditions. The first increase in the ratio of HC1 : C„H 4 occurs from about 1.9 to about 1.98, which as shown occurs gradually, but may also occur suddenly. The increase indicates a process upset which is corrected at the point indicated by reference symbol U, by increasing the flow of ethylene sufficiently to lower the ratio to about 1.7. Despite the increase of mass flow of gases to the reactor, the bed height h» which initially increased as the ratio of HC1 : C„H . increased, begins to level off as does, correspondingly, the bed density. After a period of time the bed height commences to fall and, correspondingly, the bed density increases though the ratio is maintained at 1.7. When the rate of decrease of bed height, and correspondingly, the rate of increase of density, as is evidenced by the slopes of the curves, appears to accelerate, a correction of the ratio is made at the point indicated by the reference symbol "c", by slowly decreasing the rate of flow of C ^ H . and increasing the ratio to about 1.9 (say). Having thus reverted to the initial ratio at which desired operating conditions are attained, it is hoped that stable conditions, as illustrated by the parallel lines after point C, become re-established. Several additional corrections may be necessary before the desired operating corrections are achieved. At no time during which the ratio, pressure drop and bed height (or density) are unstable is there evidence of how closely the inversion point was approached, if indeed it was approached at all. The evidence indicates that the bed suffered a process upset which was countered by correcting the HC1 : C„H . ratio at point U; that after a period of time, the rates of change of bed height and density indicated that there was an overcorrection which was again countered by correcting the ratio at OMPI ■ _ wipo point C; and, that thereafter the initial, stable desired operating conditions bec re-established. The evidence does not indicate where the optimum opera conditions existed, or whether they existed at all. Simulation of the operation of a plant reactor will be more re understood by reference to Figure 2 wherein a laboratory reactor is diagramm ally illustrated, identified generally by reference numeral 1, including a glass about 2" in diameter and about 3.5 ft long, in which is placed a bed of suppo cuprie chloride catalyst resting on a gas-permeable porous glass frit, or sint metal plate 2. The glass tube reactor has an enlarged upper end from which, point marked EFFLUENT, the effluent is ducted for analysis and recovery shown). Thermocouple wells 5 and 6 are provided above and below the porous p 2, and several thermocouples are connected to a bank of temperature control Tl, T2, T3 and T4. Air, ethylene and anhydrous HC1 are flow controlled conventional means illustrated, and mixed just prior to being introduced into reactor, near its bottom, through feed line 3. A pendulum is longitudinally axi disposed within the reactor 1, its bob 4 being immersed in the bed of catalyst. bob 4 is affixed to one end of a rigid rod 7, the other end of which protrudes f the top of the reactor. A permanent magnet M is removably affixed to said o end of the rod 7 so that the magnet is symmetrically disposed about longitudinal axis of the rod. A rectangular frame 8 is provided to facili mounting of the magnet. A short extension of rigid rod 9 extends from the fr 8, the extension 9 being longitudinally axially aligned with the rod 7, and for with the frame 8, a rigid assembly. The pendulum thus includes extension 9, magnet M in its frame 8, the rod 7 and the bob 4. The pendulum is suspended f an actuator means 11 by a torsion wire 10. The actuator means 11 serves to provide a sudden predeterm angular torque to the torsion wire 10 which transmits the torque to the pendul This function is conveniently provided by a modified air operated ball valve (suc is commercially available from the Whitey Co., Oakland, California), in which valve has been removed but the valve stem retained, so that the ste pneumatically actuatable and rotatable through a predetermined angle, prefer in the range from about 5 to about 40 . After actuation and subsequent damp the stem }ψ returned to its original position by a spring. It is preferred to actuate the actuator 11 at regular intervals by a solenoid which is energized timing mechanism, say at intervals from about 30 sees to about 15 min, including the period of damping of the pendulum. Details of the actu mechanism are not shown as they are well-known. Also the precise manne which the actuation is imparted to the pendulum is not critical, it only b important that the sudden torque, through a predetermined angle, be reliably and reproducibly imparted to the pendulum. Adjacent the magnet M and in magnetic communication therewith is placed a Hall probe 12 in which is generated a fluctuating electrical potential induced by the oscillating magnetic field of the magnet. Current from the Hall probe is conducted to a gauss eter 14, and thence, part to a strip chart recorder 13 and part to a computer (not shown), popularly referred to as a "peak picker," which reads the peaks of the signals from the gaussmeter, where the signals are appropriately amplified, as is well-known in the art. Amplitudes of successive oscillations of the pendulum, after it is given an initial angular displacement when the actuator means is air-actuated, are recorded on either the positive (preferred) or negative side of the horizontal. The slope of the curve formed by joining the peak points is computed to obtain a decay constant for the damped harmonic oscillations of the pendulum, which oscillations decay exponentially with time. The decay constant so obtained is directly proportional to the viscosity of the fluid bed of catalyst in the reactor. The foregoing may be stated mathematically as follows: A = A e cos (ω t) where A = amplitude of detector response ω = angular frequency t = time k = exponential decay constant Referring now to Fig. 3 there is illustrated a representative strip chart graphically illustrating a fluctuating output signal of diminishing amplitude. The curve, shown as a dotted line, connecting the peaks on the positive side of the horizontal, may be defined by the equation: AA == AA -ktt o ee -k , , bbeeccaause frequency remains constant, from which InA = -kt + In A o Referring now to Fig. 4 there is illustrated a se ilog plot graphically illustrating successively diminishing peak amplitudes corresponding to damped torsional oscillations as a function of time. The scale for amplitude is set arbitrarily, the first amplitude being the greatest, and successive amplitudes diminishing over a period about 30 sees. The initial amplitude will be determined by the apparatus. The period over which damping occurs will be determined by bed characteristics. The slope is quantitatively defined by "k," relative values of which are a measure of the relative stickiness of the catalyst. Referring now to Fig. 5 there is illustrated a plot of the rate of damping as a function of time. The dotted horizontal line through a point marked k . mm indicates stable but inefficient operation of the fluid bed. The dotted horizo line through a point marked indicates maximum stickiness at or near inversion point. The dotted horizontal line through a point marked k indic usual stickiness, at desired operating conditions, at which desired efficiency of reaction is obtained. The numerical quantitative difference Δk between k k is the desired difference between the stickiness as evidenced by the us max rate of damping (k ) and the peak rate of damping (k maχ )« Dots in Fig. 5 represent the average of 5 values of k (represented as on a series of sets of readings (five readings for each set), each reading made intervals of about 1 minute. With the particular system for which measurements plotted as dots in Fig. 5 were made, that is, with a partic pendulum, angular displacement, fluid-bed laboratory reactor, catalyst, and proc conditons, the inversion point occurred near k = 0.6. The operating range for reactor is in the range 'from k = 0.15 for a lower limit, to just above about k = which is a desired operating upper limit, i.e. an operating range from about 25% about 67% of k max . It will now be evident that op c eration of the fluid-bed reac at values of k near the lower limit will provide safer operation but lower ef icie while operating values of k near the upper limit provide greater efficiency but l margin of safety. In general, a ratio of HCl : C 2 H . of about 1.9 allows operat near the upper operating limit of k, i.e. near 67% of k_ Q . though these values vary from one catalyst to another. Of particular interest are values of k which are represented by dots and Aft on Fig. 5. Prior to commencing the oxyhydrochlorination reaction on supported copper chloride catalyst, the bed is fluidized with only that amount of corresponding to 0.8 moles oxygen per mole of ethylene to be fed for the react at reactor operating temperature. The value of k (average for 5 readings) represented by A- and is about 0.13. Thereafter ethylene and HCl are also fed the reactor nearly doubling the mass flow of gases through the fluid-bed, decreasing the bed density, yet the value of k increases. After numerous sets readings are made for various ratios of HCl : C„H ., the k values for which represented by the dots in Fig. 5, the flow of both HCl and C«H . is discontinu and a set of 5 readings are taken with only air being flowed to the reactor. average o -this set of 5 readings is represented by the dot identified as A _ 9 _ an about 0.13, which indicates that without the chemical reaction, the viscosity of fluid-bed with air flow only, is essentially constant. The method described hereinabove, of selecting a desirable mode of operation of a fluid-bed reactor, and the apparatus for doing so, may be adapted, with appropriate engineering modifications, to a commercial reactor in which the pendulum viscometer is disposed inside the reactor, so as to provide direct readings of viscosity while the reactor is operating. In such an embodiment it is possible to be informed, essentially continuously, of the condition of the catalyst in the reactor as well as the efficiency of the reaction therewithin.

Claims: WE CLAIM: 1. In a process using a catalytic fluid-bed reactor provided wit pendulum viscometer and means to provide said pendulum with a preselected ini angular displacement, a method for obtaining desired operation of said reac comprising, (a) charging said reactor with a supported catalyst in the presence of whic chemical reaction occurs which increases stickiness of said catalyst as convers of feed components to desired products is improved, (b) measuring a peak rate of damping of a predetermined torsional oscillation said pendulum viscometer during operation of said fluid-bed at or near its invers point, (c) measuring a usual rate of damping of said predetermined torsional oscillation said pendulum viscometer during usual, desired operating conditions, (d) obtaining a quantitative difference between said usual rate and said peak rate damping, and (e) adjusting said process conditions to operate said reactor while maintain approximately said quantitative difference. 2. The process of claim 1 wherein said reaction occurs at temperatur ■ ee iinn tthhee rraannggee aabboovvee aabboouutt 110000 CC bbuutt b below a temperature deleteri to said catalyst, and at about atmospheric pressure. 3. The process of claim 2 wherein feed components which enter i said reaction include a lower alkane having from about 1 to 4 carbon atoms, oxy and hydrogen chloride. 4. The process of claim 2 wherein feed components which enter i said reaction include a monoolefin having from 2 to about 4 carbon atoms and oxygen containing gas. 5. The process of claim 2 wherein said quantitative difference obtained at predetermined intervals of time, at least once every 8 hours dur operation of said reactor. 8. The process of claim 4 wherein said supported catalyst has as essential catalytic ingredient an element selected from the group consisting of s elements of Groups I, V, and VI. 7. The process of claim 5 wherein said feed components include ethylene and hydrogen chloride. 8. The process of claim 4 wherein said feed components include propylene and ammonia. 9. The process of claim 7 wherein said supported catalyst is supported copper chloride, and said reaction occurs at a temperature in the range from about 200°C to about 300°C. 10. A method for operating a pressurized plant fluid-bed reactor at desired operating conditions, and particularly at a desired ratio of feed components comprising: (a) operating at about atmospheric pressure, a laboratory fluid-bed reactor charged with a supported catalyst having a proclivity to increase in stickiness as conversion of f eed components to a desired product improves, (b) supplying said feed components to said reactor in a molar ratio corresponding to that supplied to said plant reactor, (c) measuring a peak rate of damping of a predetermined torsional oscillation of a pendulum viscometer during operation of said laboratory fluid-bed reactor at or near its inversion point, (d) measuring a usual rate of damping of said predetermined oscillation of said pendulum viscometer during said laboraory fluid-bed reactor with said molar ratio, (e) obtaining a quantitative difference between said usual rate and said peak rate of damping, and (f) adjusting flow rates of said components in said plant reactor to change said molar ratio so as to maintain said quantitative difference within preselected limits. 11. A process for comparing the sensitivity of a first supported catalyst with a second supported catalyst when each is separately used to promote a chemical reaction in a fluid-bed reactor provided with a pendulum viscometer comprising, (a) charging said reactor with said first catalyst and maintaining said reaction under conditions which increase stickiness of said catalyst as conversion of feed components to desired productes improves, (b) measuring a first rate of damping of a predetermined torsional oscillation of said pendulum viscometer during operation of said fluid-bed of said first catalyst, using a preselected ratio of HC1/C„H 4 , (c) substituting said second catalyst for said first catalyst in the same reactio said reactor, (d) measuring a second rate of damping of said predetermined torsional oscillat of said pendulum viscometer during operation of said fluid-bed of said sec catalyst, using the same preselected ratio of HC1/C„H 4 , (e) comparing said first and second rates of damping, and, (f) selecting the less sensitive catalyst. 12. A control system for a pressurized commercial fluidized bed reac comprising in combination, (a) a laboratory fluid-bed reactor operating at about atmospheric pressu including a supported catalyst having a proclivity to increase in stickiness conversion of reaetants to a desired product improves, (b) a torsional pendulum viscometer in said fluid-bed reactor, (c) means to impart a predetermined initial angular displacement to said pendulu (d) measurement means for measuring the rate of damping of said torsio pendulum after it is set in oscillation, and (e) means, responsive to the rate of damping of said torsional pendulum after it set in oscillation, for recording the rate of damping at successive predetermi periods of time so that a preselected rate of damping determines a choice desirable operating conditions of said pressurized reactor. O • -- WI

Inventors: COWFER J, JABLONSKI D, KOVACH R, MAGISTRO A
Applicants: GOODRICH CO B F
Application year: 1979
Main classification: C07C120
IPC codes: B01J8, C07C17, C07C19, C07C67, G01N11